KR20160093605A - Glass substrate finish-polishing method and alkali-free glass substrate that has been finish-polished by said method - Google Patents

Abstract

The present invention relates to a finish polishing method of a glass substrate for polishing a main surface of a glass substrate using a polishing slurry containing cerium oxide as abrasive grains, characterized in that the composition of the glass substrate is the following alkali-free glass, Polishing is performed under the condition that 0.04 / X is 0.12 or more when the abrasion amount of the glass substrate is X (mu m) when the height of the bending converted into the bending of 20 mm pitch of the glass substrate changes from 0.14 mu m to 0.10 mu m To a finish polishing method for a glass substrate.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for polishing a glass substrate, and a method for polishing the glass substrate using the glass substrate,

The present invention relates to a method for finishing a non-alkali glass substrate substantially free of an alkali metal oxide for use as a display glass substrate or a glass substrate for a photomask, and a method for finishing a non- .

BACKGROUND ART [0002] Conventionally, when forming a glass substrate for various displays, particularly, a metal or an oxide thin film on a surface thereof, the following characteristics have been required.

(1) If it contains an alkali metal oxide, alkali metal ions should not be substantially contained because alkali metal ions diffuse into the thin film to deteriorate the film characteristics.

(2) When the film is exposed to high temperatures in the thin film forming step, the strain point should be high so as to minimize the shrinkage (heat shrinkage) accompanying the deformation of the glass and the structure stabilization of the glass.

(3) It should have sufficient chemical durability against various chemicals used for semiconductor formation. In particular, it is possible to use buffered hydrofluoric acid (BHF: mixed liquid of hydrofluoric acid and ammonium fluoride) for etching SiO _x or SiN _x , chemical solution containing hydrochloric acid used for etching of ITO, various acids used for etching metal electrodes Etc.), durability against the alkali of the resist stripping solution.

(4) There shall be no defects (bubbles, spots, inclusions, pits, scratches, etc.) on the inside and on the surface.

In addition to the above-mentioned demands, in recent years, the following situation is present.

(5) It is required to reduce the weight of the display, and the glass itself is required to have a low density.

(6) Lightness of the display is required, and thinning of the glass substrate is desired.

(7) In addition to the conventional amorphous silicon (a-Si) type liquid crystal display, a polycrystalline silicon (p-Si) type liquid crystal display having a slightly higher heat treatment temperature has been produced -Si: 350 to 550 < 0 > C).

(8) Production of liquid crystal display In order to increase the temperature rise speed of the heat treatment and to increase the productivity or increase the thermal shock resistance, a glass having an average coefficient of thermal expansion of glass is required.

On the other hand, as the dryness of the etching progressed, the demand for the BHF resistance became weak. In order to improve the BHF resistance, glass containing 6 to 10 mol% of B ₂ O ₃ has been used so far. However, B ₂ O ₃ tends to lower the strain point. Examples of the alkali-free glass which does not contain B ₂ O ₃ or has a low content include the following.

Patent Document 1 discloses a glass containing 0 to 5 mol% of B ₂ O ₃ and has an average thermal expansion coefficient of 50 × 10 ^-7 / ° C. at 50 to 350 ° C.

The alkali-free glass described in Patent Document 2 has a high strain point and can be molded by the float method, and is said to be suitable for use as a display substrate, a photomask substrate, and the like.

Japanese Patent Application Laid-Open No. 5-232458 Japanese Unexamined Patent Application Publication No. 10-45422

In the finish polishing carried out for this purpose, it is possible to remove minute irregularities and curvatures existing on the surface of the substrate with a smaller amount of polishing. This reduces the cost required for finish polishing, It is preferable to mix the glass scrap with the polishing slurry to reduce the frequency of replacement of the polishing slurry.

On the other hand, the glass substrate molded by the float method has minute unevenness and curvature (a pitch of 3 to 30 mm and a maximum height of about 0.3 탆) on its surface. Such minute convexo-concaves and convexities are not problematic when the glass substrate molded by the float method is used as a plate glass for automobiles and architectures, but when used as a glass substrate for various displays, Which causes deformation and color unevenness. For this reason, it is necessary to remove minute concavities and convexities by finishing polishing.

For the finish polishing carried out for this purpose, polishing using a polishing slurry containing cerium oxide is preferably used as abrasive grains.

However, there is a solid phase crystallization method as a manufacturing method of a high-quality p-Si TFT, but in order to do this, it is required to further increase the strain point.

In addition, it is required to lower the temperature T ₄ at which the viscosity of the glass, in particular, the glass viscosity becomes 10 ⁴ dPa · s, from the request in the glass manufacturing process, particularly in the melting and molding.

An object of the present invention is to solve the above-mentioned drawbacks and to provide a method for polishing a non-alkali glass substrate having a high strain point, low viscosity, especially a glass viscosity of 10 ⁴ dPa 가 at a low temperature T ₄ , There is provided a finish grinding method of a glass substrate capable of eliminating minute unevenness and bending existing on the surface of a substrate and a finishing polished non-alkali glass substrate by the method.

The present invention relates to a finish polishing method for a glass substrate for polishing a main surface of a glass substrate by using a polishing slurry containing cerium oxide as abrasive grains,

Wherein the composition of said glass substrate is the following alkali-free glass,

X is 0.12 or more, where X (mu m) represents the amount of abrasion of the glass substrate when the height of the bending of the main surface of the glass substrate at a pitch of 20 mm is changed from 0.14 mu m to 0.10 mu m Polishing the surface of the glass substrate.

A temperature T ₂ at which the glass transition temperature is 680 to 735 ° C, an average thermal expansion coefficient at 50 to 350 ° C is 30 × 10 ^-7 to 43 × 10 ^-7 / ° C, and a glass viscosity is 10 ² dPa · s is 1710 ° C or less , The temperature T ₄ at which the glass viscosity becomes 10 ⁴ dPa · s is 1330 ° C. or less, and the glass transition temperature

SiO ₂ 63 to 74,

Al₂O₃ 11.5 to 16,

B ₂ O ₃ 1.5 to 5 or less,

MgO 5.5 to 13,

CaO 1.5 to 12,

SrO 1.5 to 9,

BaO 0 to 1,

ZrO ₂ 0 to 2

MgO + CaO + SrO + BaO is 15.5 to 21,

Alkali-free glass having a MgO / (MgO + CaO + SrO + BaO) of 0.35 or more, CaO / (MgO + CaO + SrO + BaO) of 0.50 or less and SrO / (MgO + CaO + SrO + BaO) of 0.50 or less.

In the finish polishing method of the glass substrate of the present invention, it is preferable that the height of the bending in terms of bending at a pitch of 20 mm on the main surface of the glass substrate before the finish polishing is 0.2 탆 or less.

In the finish polishing method of the glass substrate of the present invention, the main surface of the glass substrate formed by the float method is preferably finely polished.

The present invention also provides a finish-polished alkali-free glass substrate using a finish polishing method of a glass substrate.

In the glass substrate of the present invention, it is preferable that the height of the bending in terms of bending at a pitch of 20 mm on the main surface of the glass substrate after finish polishing is 0.07 탆 or less.

In the glass substrate of the present invention, it is preferable that the surface roughness of the main surface of the glass substrate after finishing polishing is not more than 0.30 nm at 5 mu m square.

It is preferable that at least one side of the glass substrate of the present invention has a length of 900 mm or more.

According to the method of the present invention, when the non-alkali glass substrate formed by using the float method is finely polished, it is possible to remove minute concaves and convexes existing on the surface of the substrate with a small amount of polishing, A suitable high flatness can be achieved.

The non-alkali glass substrate finishing-polished by the method of the present invention is particularly preferable for a display substrate, a photomask substrate, and a glass substrate for a magnetic disk, particularly for a high strain point application.

1 is a schematic diagram showing a relationship between a pitch and a curvature.
2 is a perspective view showing an overall structure of a polishing apparatus to which a finish polishing method for a glass substrate according to an embodiment is applied.
3 is a side view of the polishing apparatus 10 shown in Fig.
Fig. 4 is a schematic diagram showing a dressing method of a polishing tool by the truing stone of the embodiment. Fig.
5 is a plan view of the polishing tool dressed by the dressing method shown in Fig.
6 is a side view showing a dressing method of a polishing tool by a watering nozzle for dressing.

Hereinafter, the finish polishing method of the glass substrate of the present invention will be described.

In the finish polishing method of the glass substrate of the present invention, a non-alkali glass substrate using glass raw materials combined so as to have the following glass composition is used.

Expressed in mole% based on oxide

SiO ₂ 63 to 74,

Al₂O₃ 11.5 to 16,

B ₂ O ₃ 1.5 to 5 or less,

MgO 5.5 to 13,

CaO 1.5 to 12,

SrO 1.5 to 9,

BaO 0 to 1,

ZrO ₂ 0 to 2

MgO + CaO + SrO + BaO is 15.5 to 21,

Alkali-free glass having a MgO / (MgO + CaO + SrO + BaO) of 0.35 or more, CaO / (MgO + CaO + SrO + BaO) of 0.50 or less and SrO / (MgO + CaO + SrO + BaO) of 0.50 or less.

Next, the composition range of each component will be described. When the SiO _{2 content} is less than 63% (mol%, the same applies unless otherwise specified), the strain point is not sufficiently increased, the thermal expansion coefficient is increased, and the density is increased. In addition, the chemical durability of the glass, particularly the acid resistance, is lowered, the convex part selectivity at the time of polishing is hardly obtained, and smoothness is hardly obtained. Is preferably 64% or more, more preferably 65% or more, still more preferably 66% or more, and particularly preferably 66.5% or more. If more than 74%, the solubility decreases, the temperature T ₄ is raised to be the temperature T ₂ and 10 ⁴ dPa · s the glass viscosity is 10 ² dPa · s, and the devitrification temperature increases. Is preferably 70% or less, more preferably 69% or less, and even more preferably 68% or less.

Al ₂ O ₃ enhances the Young's modulus to suppress the deformation during polishing of the glass, suppress the fracture of the glass, lower the coefficient of thermal expansion, increase the strain point, increase the hardness and increase the convex part selectivity during polishing , And if it is less than 11.5%, this effect does not appear, and the components for increasing other expansion are increased, resulting in a large thermal expansion. 12% or more, 12.5% or more, and more preferably 13% or more. If it is more than 16%, the solubility of the glass may be deteriorated or the melt temperature may be increased. Is preferably 15% or less, more preferably 14% or less, and further preferably 13.5% or less.

B ₂ O ₃ improves the dissolution reactivity of the glass, decreases the slag temperature and improves the internal BHF property. When the B ₂ O ₃ content is 1.5% or less, this effect is not sufficiently exhibited and the strain point becomes excessively high, or BHF It is likely to become a problem of haze after the treatment by the above method. 2% or more is preferable, and 3% or more is more preferable. However, if it is too large, the photoelastic constant becomes large, and when the stress is applied, problems such as color unevenness tend to occur. Also, if B ₂ O ₃ is too much, the Young's modulus is lowered, the smoothness is not easily caused by the deformation during polishing, and the surface roughness after polishing is increased. Also, the strain point is lowered. Therefore, it is 5% or less, preferably 4.5% or less, more preferably 4% or less.

MgO has the characteristic of increasing the Young's modulus while keeping the density low and not increasing the expansion in the alkaline earth and improving the solubility. When the content is less than 5.5%, MgO does not sufficiently exhibit this effect, and other alkaline earth ratios The higher the density, the higher the density. More preferably 8% or more, more preferably 8% or more, further preferably 8.3% or more, particularly preferably 8.5% or more. If it exceeds 13%, the melt temperature rises. Is preferably 12% or less, more preferably 11% or less, and particularly preferably 10% or less.

CaO has a feature of increasing the Young's modulus while keeping the density low and not increasing the expansion in the alkaline earth after MgO, and improving the solubility. If it is less than 1.5%, the effect of CaO addition described above does not sufficiently appear. Is preferably 2% or more, more preferably 3% or more, still more preferably 3.5% or more, and particularly preferably 4% or more. However, when the content exceeds 12%, there is a fear that the release temperature increases or phosphorus, which is an impurity in limestone (CaCO ₃ ) as a CaO raw material, is incorporated. Is preferably 10% or less, more preferably 9% or less, still more preferably 8% or less, and particularly preferably 7% or less.

SrO improves solubility without increasing the glass transition temperature, but if it is less than 1.5%, this effect does not sufficiently appear. Is preferably 2% or more, more preferably 2.5% or more, and still more preferably 3% or more. However, if it exceeds 9%, the expansion coefficient may increase. Is preferably not more than 7%, more preferably not more than 6% and not more than 5%.

BaO is not essential but may be contained for the purpose of improving solubility. However, if it is too much, the glass becomes brittle and easily scratched, and at the same time, the expansion and the density are excessively increased, so that it is 1% or less. It is preferably not more than 0.5%, more preferably not more than 0.3%, further preferably not more than 0.1%, particularly preferably not substantially. Substantially free means that it contains no inevitable impurities (the same applies hereinafter).

ZrO ₂ may contain up to 2% in order to increase the Young's modulus, to lower the glass melting temperature, or to promote the crystallization during firing. If it exceeds 2%, the glass becomes unstable or the relative dielectric constant epsilon of the glass becomes large. , Preferably not more than 1.5%, more preferably not more than 1.0%, further preferably not more than 0.5%, particularly preferably not substantially.

When the total amount of MgO, CaO, SrO, and BaO is less than 15.5%, the Young's modulus is low and it is difficult to suppress the deformation during polishing and the hardness is low. In addition, the photoelastic constant increases and the solubility decreases. 16% or more is preferable, and 17% or more is more preferable. If it is more than 21%, there is a fear that the thermal expansion coefficient can not be reduced. 20% or less, 19% or less, or 18% or less.

MgO, CaO, SrO, and BaO satisfying the above conditions and satisfying the following 3 conditions, the Young's modulus is high, the deformation during polishing is easily suppressed, the non-elasticity ratio is high, And the temperature T ₄ at which the viscosity of the glass, especially the glass viscosity, becomes 10 ⁴ dPa · s can be lowered.

MgO / (MgO + CaO + SrO + BaO) is 0.35 or more, preferably 0.37 or more, more preferably 0.4 or more.

CaO / (MgO + CaO + SrO + BaO) is 0.50 or less, preferably 0.48 or less, more preferably 0.45 or less.

The ratio of SrO / (MgO + CaO + SrO + BaO) is preferably 0.50 or less, more preferably 0.40 or less, more preferably 0.30 or less, still more preferably 0.27 or less,

Al ₂ O ₃ x (MgO / (MgO + CaO + SrO + BaO)) of 4.1 or more is preferable because the Young's modulus is increased to suppress the deformation during polishing. Preferably not less than 4.3, more preferably not less than 4.5, still more preferably not less than 4.7, particularly preferably not less than 5.0.

In order to prevent the deterioration of the characteristics of the metal or oxide thin film provided on the glass surface during the production of the display using the alkali-free glass substrate of the present invention, it is preferable that the glass material does not substantially contain P ₂ O ₅ . Further, in order to facilitate recycling of the glass, it is preferable that the glass raw material does not substantially contain PbO, As ₂ O ₃ , and Sb ₂ O ₃ .

In order to improve the solubility, the refining property and moldability of the glass, the glass is ZnO, Fe ₂ O _3, SO _3, F, Cl, SnO ₂ 1%, preferably 0.5%, more preferably at most 0.3% Or less, more preferably 0.15% or less, particularly preferably 0.1% or less. It is preferable that ZnO is substantially not contained.

The production of the alkali-free glass substrate of the present invention is carried out, for example, in the following procedure.

The raw materials of each component are combined so as to be a target component, the mixture is continuously introduced into a melting furnace, and the mixture is heated to 1500 to 1800 캜 for melting. The molten glass is molded into a plate-shaped glass ribbon having a predetermined plate thickness in a molding apparatus, the glass ribbon is annealed and then cut to obtain a non-alkali glass substrate.

In the present invention, it is preferable that the glass ribbon is formed into a plate shape by the float method.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of a finish polishing method of a glass substrate according to the present invention will be described in detail with reference to the accompanying drawings.

Fig. 2 is a perspective view showing the entire configuration of the polishing apparatus 10 to which the finish polishing method of the glass substrate of the embodiment is applied. 3 is a side view of the polishing apparatus 10 shown in Fig.

The polishing apparatus 10 shown in these figures is a glass plate G manufactured by a float method and has a main surface (a polishing surface) of a glass plate G having a thickness of 0.7 mm or less, a length of one side of 900 mm or more and a Young's modulus of 65 GPa or more, Is used to polish a flat glass substrate for an FPD glass substrate using a polishing tool. That is, the polishing apparatus 10 polishes the abrasive surface of the glass plate G having a bending height of 0.2 탆 or less in terms of the bending of 20 mm pitch, and adjusts the height of bending in terms of the bending of 20 mm pitch to 0.07 탆 or less To thereby produce an optimal glass plate as an FPD glass substrate that does not impart deformation or color unevenness to the image.

In addition, in the present invention, even if a thin plate having a thickness of 0.5 mm or less or a plate having a length of one side of 1000 mm or more is formed by setting the Young's modulus of the glass plate G to 78 GPa or more, the main surface (polished surface) The glass substrate for FPD can be polished to a desired flatness.

In addition, the method of measuring the bending is the method described in JIS B0031: '82 and JIS B0601: '82. The pitch and bend can be defined as shown in Fig. If the pitch is large, the bending becomes large, but the height of the bending converted into the bending of the pitch of 20 mm can be obtained by linearly regressing the relationship between the pitch and the bending.

It is more preferable that the height of the bending in terms of the bending at the pitch of 20 mm on the main surface of the glass substrate before finish polishing is 0.17 탆 or less. It is more preferable that the height of the bending in terms of the bending of 20 mm pitch on the main surface of the glass substrate after finish polishing is 0.05 탆 or less.

The polishing apparatus 10 is composed of a polishing head 12 and a surface plate 14. The polishing head 12 includes a glass holding member 16 for holding a non-polished surface of the glass plate G, a glass holding table 20 provided with a glass holding member 16 via a seal member 18, And a canvas (22) provided with a glass holding base (20). The rotary shaft 24 is fixed to the canvas 22 and the rotary shaft 24 is rotated around the axial center P1 so that the polishing head 12 is rotated and the rotary shaft 24 revolves around the pivotal axis P2 , The polishing head 12 is revolved.

Compressed air is supplied to the air chamber 23 of the canvas 22 via the hollow rotary shaft 24 and the pressure of the compressed air is applied to the glass holding table 20, And is transferred to the glass plate G via the glass holding member 16.

The surface plate 14 is provided with a polishing tool holding base plate 30 provided with a polishing tool 26 and a polishing tool 26 via a sealing material 28. The sealant 28 is a sealant made of a resin (e.g., polyurethane) which is soft and improves the adsorption retention.

Therefore, in the polishing apparatus 10 of the embodiment, the polishing surface of the glass plate G is pressed against the polishing tool 26 by the pressure of the compressed air, and the polishing head 12 is rotated and revolved, .

The abrasive grain 26 preferably has an A hardness of 20 or more, a D hardness of 99 or less, a thickness of 1.0 to 2.5 mm, and a thickness distribution of within ± 0.3 mm, And is preferably within ± 0.05 mm.

If the hardness A of the polishing tool 26 is less than 20, the bending of the glass plate G can not be reduced, and if the hardness D exceeds 99, the glass plate G tends to be broken. If the thickness of the polishing tool 26 is less than 1 mm, the grooving tool 26 can not be formed. Particularly, in the case of the large-area polishing tool 26, if the grooving can not be performed, the abrasive grain distribution becomes uneven and a problem arises in the processing of the glass plate G. On the other hand, when the thickness of the polishing tool 26 exceeds 2.5 mm, the deformation value of the polishing tool 26 becomes large and the processing quality of the glass plate G deteriorates. The thickness distribution of the polishing tool 26 is the maximum thickness in the region excluding the grooved portion-the minimum thickness. If this thickness distribution exceeds. + -. 0.3 mm, the pressure distribution becomes large and the quality of the glass plate becomes poor. The thickness distribution is preferably within ± 0.2 mm, more preferably within ± 0.1 mm, and even more preferably within ± 0.05 mm.

By defining the hardness, thickness, and thickness distribution of the polishing tool 26 as described above, it is possible to polish the glass plate G produced by the float method to a more optimal glass plate as the glass substrate for FPD.

On the other hand, as a result of intensive studies, the inventor of the present invention has found that it is not sufficient to manage the A hardness of the polishing tool 26 in order to make the height of the bending converted into the bending of 20 mm pitch 0.07 탆 or less, , The compressibility, the compressive modulus, the A hardness, the thickness, and the thickness distribution.

For example, if the A hardness of the glass holding member 16 is too low, the durability of the glass holding member 16 is lowered, and the glass holding member 16 can not be used repeatedly. Further, when the A hardness of the glass holding member 16 is appropriately low, the glass holding member 16 absorbs the bend existing on the non-polishing surface of the glass plate G, so that the glass holding member 16 is present on the polishing surface of the glass plate G It is possible to satisfactorily grind the curved portion by the polishing tool 26. [ On the other hand, when the A hardness of the glass holding member 16 is too high, the glass holding member 16 can not absorb the bend existing on the non-polishing surface of the glass sheet G, When the glass plate G is removed from the glass holding member 16, the glass plate G causes spring back. As a result, the glass plate G is bent on the polishing surface of the glass plate G, There is a fear that a bending exceeding 0.07 mu m is left.

In addition, if the thickness distribution is larger than ± 0.05 mm, the cushioning property of the glass holding member 16 may be uneven in the plane of the glass plate G, resulting in a problem that the curvature is not uniform.

The compressibility indicates the cushioning property following the initial glass plate G, and the compressive modulus is a parameter necessary for indicating the degree of restoration in the case of repeated use. The glass holding member 16 is made of foamed polyurethane.

In order to solve the above problem, the glass holding member 16 is required to have a compressibility (JIS L1021-6: '07 Annex 1) of 10 to 70% and a compressive elastic modulus (JIS L1021-6: It is preferable that the thickness distribution is within ± 0.05 mm, the initial hardness is 100 gf / cm 2, the final load is 1120 gf / cm 2) is 70 to 98, the A hardness is 2 to 20, the thickness is 0.3 to 2.0 mm.

Further, management of the glass holding member 16 is required to narrow the management range particularly when the glass plate G is thin. For example, the glass holding member 16 in the case of the glass plate G having a plate thickness of 0.5 mm or less has a compression ratio of 10 to 70%, a compression modulus of 70 to 98, an A hardness of 2 to 20, a thickness of 0.5 to 1.5 mm , And the thickness distribution is preferably within ± 0.05 mm. The glass holding member 16 in the case of the glass plate G having a thickness of 0.3 mm or less has a compression ratio of 10 to 70%, a compression modulus of 70 to 98, an A hardness of 2 to 20, a thickness of 0.7 to 1.2 mm, It is preferable that the distribution is within ± 0.05 mm.

By defining the compressibility, compression modulus, A hardness, thickness, and thickness distribution of the glass holding member 16 as described above, it is possible to polish the glass plate G produced by the float method as an optimal glass plate as the glass substrate for FPD have.

The surface of the glass holding support table 20 on which the glass holding member 16 is provided via the sealing material 18 is set such that the maximum section height of the curved line when the evaluation length is 30 mm is 20 m or less .

Even if the glass holding member 16 is managed, if the maximum cross-sectional height of the curved line of the glass holding platen 20 is too high, the curvature existing on the non- It is difficult to polish the bending of the polished surface of the glass plate G to 0.07 탆 or less at a bending height in terms of bending of 20 mm pitch.

By defining the maximum sectional height of the curved curve of the glass holding support table 20 as described above, it is possible to satisfactorily absorb the bend existing on the non-polishing surface of the glass plate G by the glass holding member 16, Can be polished with a more optimal glass plate as a glass substrate for an FPD.

It is preferable that a maximum cross sectional height of the section curve when the evaluation length is 30 mm is not more than 100 占 퐉 with respect to the surface of the polishing tool holding base 30 provided with the polishing tool 26 via the sealing material 28 .

Even if the polishing tool 26 is controlled, if the maximum sectional height of the sectional curve of the holding tool holding base 30 is too high, a large bending occurs on the surface of the polishing tool 26, It is difficult to polish the bending to 0.07 占 퐉 or less at the bending height converted into the bending of 20 mm pitch.

Therefore, by defining the maximum cross-sectional height of the cross-section curve of the holding tool holding base 30 as described above, the surface curvature of the polishing tool 26 can be suppressed, so that the glass plate produced by the float method can be used as the glass for FPD The substrate can be further polished with an optimal glass plate.

The maximum cross-sectional height of the curved line is described in JIS B0601: '01.

The maximum cross-sectional height of the bending curve is measured with a 1400-D64 Surfcommer manufactured by Tokyo Seimitsu Co., Ltd. under measurement conditions of measurement length 30 mm and? C = 0.8 mm.

It is also preferable that the variation of the load pressing the polishing surface of the glass plate G against the polishing tool 26 is 10% or less of the average load.

By defining the load of the polishing tool 26 with respect to the glass plate G as described above, the glass plate G produced by the float method can be further polished into an optimal glass plate as the glass substrate for FPD. As a means for measuring the load distribution, "BIG-MAT" or "HUGE-MAT" which is a large area pressure distribution measurement system manufactured by Nitta Corporation can be used.

As described above, according to the polishing apparatus 10 of the embodiment, the glass plate G manufactured by the float method, the glass plate G having a thickness of 0.7 mm or less, a length of one side of 900 mm or more and a Young's modulus of 65 GPa or more, , The non-polished surface of the glass plate G is held by the glass holding member 16 and bent at a height of a bend of 20 mm pitch on the polished surface of the glass plate G, To a thickness of 0.07 占 퐉 or less at a bending height equivalent to a bend of 20 mm pitch, thereby producing a glass substrate for a flat panel display. As a result, it is possible to produce an optimal glass plate G as an FPD glass substrate which does not impart deformation or color unevenness to the image.

In the finish polishing method of the glass substrate of the present invention, when the glass substrate polishing amount when the height of the bending converted into the bending of 20 mm pitch changes from 0.14 m to 0.10 m is X (mu m), 0.04 / Or more. As a result, the cost required for finish polishing is reduced, and the mixing of the glass powder or glass scrap removed in the polishing into the polishing slurry is reduced, and the frequency of replacement of the polishing slurry can be reduced. More preferably 0.14 or more, and particularly preferably 0.15 or more, under the condition that 0.04 / X is 0.13 or more.

In the finish polishing method of the present invention, the polishing conditions from the state where the height of the bending converted to the bending of 20 mm pitch is higher than 0.14 탆 until the height of the bending becomes 0.14 탆, 0.04 / X is not less than 0.12. However, it is preferable that the above-mentioned 0.04 / X is 0.12 or more.

Further, in the finish polishing method of the present invention, the polishing conditions when the height of the bending converted into the bending of 20 mm pitch is made smaller than 0.10 탆 are also satisfied under the condition that the above-mentioned 0.04 / X is 0.12 or more But the present invention is not limited to this and may be carried out under the condition that the above-mentioned 0.04 / X is smaller than 0.12.

In the finish polishing method of the glass substrate of the present invention, it is preferable that the height of the bending in terms of the bending of 20 mm pitch on the main surface of the glass substrate before the finish polishing is 0.2 탆 or less. As a result, the polishing time required for finishing can be reduced, and excellent flatness is easily obtained. The height of the bend in terms of the bend of the pitch of 20 mm is more preferably 0.17 占 퐉 or less, and still more preferably 0.15 占 퐉 or less.

In the finish polishing method of the glass substrate of the present invention, it is preferable that the height of the bending in terms of the bending at a pitch of 20 mm on the main surface of the glass substrate after the finish polishing is 0.07 탆 or less. This makes it difficult to cause deformation and color unevenness in the image on the display using the substrate. The height of the bend in terms of the bend of 20 mm pitch is more preferably 0.05 탆 or less, and still more preferably 0.03 탆 or less.

In the finish polishing method of the glass substrate of the present invention, it is preferable that the surface roughness Ra of 5 mu m square by the AFM on the main surface of the glass substrate after the finish polishing is 0.30 nm or less. This makes it easy to obtain stable driving characteristics in a display using this substrate.

An example of the polishing specification is shown below.

Polishing pressure: 2 kPa to 25 kPa

Polishing Slurry: A cerium oxide aqueous solution was supplied from a slurry supply hole of a polishing pad holding base

Sewing machine: Soft urethane-made suede type with a groove for slurry flow on the surface (groove pitch 4.5 mm, groove width 1.5 mm, groove depth 1 to 1.5 mm)

Thickness of glass plate: 0.2mm to 0.7mm

Shape of glass plate: Rectangular glass plate with one side of 900mm or more

Non-polished surface of glass plate: Adhered to glass holding member

Or more is an example of the polishing specification.

However, in the polishing apparatus 10 of the embodiment, in order to maintain the polishing rate of the glass plate G, the surface of the polishing tool 26 is regularly ground by a truing stone containing diamond abrasive grains to perform dressing .

4, a rectangular frame 42 having no diamond abrasive grains and having no grinding capability is inserted into the truing grindstone 40 as shown in the plan view of Fig. 5, Is provided on the glass holding member (16) so as to surround it. The truing stone 40 and the frame 42 are pressed against the polishing tool 26 by the air pressure of the compressed air supplied to the air chamber 23 of the canvas 22, And the surface is ground by the truing stone 40.

At this time, the air pressure is concentrated on the frame 42 located on the outer periphery of the truing stone 40. Since the frame 42 does not have grinding ability, Is not ground. That is, the surface of the polishing tool 26 is ground only by the truing stone 40 to which the air pressure is uniformly applied. As a result, the entire surface of the polishing tool 26 is flattened and the dressing by the truing stone 40 can be improved.

It is preferable to use the frame 42 not only in the case of truing the polishing tool 26 but also in polishing the glass plate G. [ Thus, it is possible to prevent the air pressure from concentrating on the edge of the glass plate G at the time of polishing the glass plate G, thereby preventing the edge of the glass plate G from being excessively grinded. As the material of the frame 42, a material having no polishing ability such as stainless steel, iron, aluminum, polyethylene, or polyurethane can be exemplified.

In the polishing apparatus 10 of the embodiment, the surface of the polishing tool 26 is regularly washed with water to maintain the polishing rate of the glass plate G, so that the surface of the polishing tool 26 attached to the surface of the polishing tool 26 And a dressing for removing residues such as cerium oxide is performed.

6, the dressing water nozzle 44 is inclined, and the spray angle? Of the washing water 48 sprayed from the spray hole 46 is set at an acute angle . Then, the water nozzle 44 and the polishing tool 26 are reciprocated relatively in the horizontal direction, thereby removing the residue attached to the surface of the polishing tool 26.

As a result, the residue attached to the surface of the polishing tool 26 is efficiently removed because the residue is torn by the pressure of the cleaning water 48 injected in an inclined manner. Also. The removed residue is efficiently washed out of the system of the polishing tool 26 by the inclined cleaning water 48 being injected. Thereby, the dressing by the water nozzle 44 can be improved.

The injection angle? Of the washing water 48 is preferably 10 to 45 degrees, more preferably 30 degrees, from the viewpoints of the extraction efficiency of the residue and the washing efficiency of the residue. The pressing force when the washing water 48 impinges against the polishing tool 26 is preferably from 5 to 50 kPa since the removal efficiency of the residue is low when the washing water is weak when the washing water 48 collides with the polishing water 26, . The relative speed between the polishing tool 26 and the water nozzle 44 is preferably 3 to 20 m / min in that the dressing efficiency of the polishing tool 26 is lowered and the removal efficiency of the residue is reduced as early as possible .

The alkali-free glass substrate of the present invention has a strain point of 680 캜 or more and 735 캜 or less.

Since the alkali-free glass of the present invention has a strain point of 680 占 폚 or higher, heat shrinkage during panel production is suppressed. In addition, a laser annealing method can be applied as a manufacturing method of the p-Si TFT. More preferably 685 DEG C or higher, and still more preferably 690 DEG C or higher.

Since the alkali-free glass of the present invention has a strain point of 680 占 폚 or higher, it can be used in a high-strain point application (for example, a display substrate having a plate thickness of 0.7 mm or less, preferably 0.5 mm or less, more preferably 0.3 mm or less, A substrate for illumination, or a display substrate or a substrate for a thin plate having a plate thickness of 0.3 mm or less, preferably 0.1 mm or less).

In the case of molding a plate glass having a plate thickness of 0.7 mm or less, further 0.5 mm or less, further 0.3 mm or less, and further 0.1 mm or less, the drawing speed at the time of molding tends to be accelerated so that the virtual temperature of the glass is increased, Factions are likely to increase. In this case, compaction can be suppressed by using a high strain point glass.

On the other hand, since the deformation point is 735 占 폚 or less, it is not necessary to set the temperature of the float bath and the float bath outlet so high, and the life of the metal member located in the float bath and on the downstream side of the float bath is less affected. More preferably 725 ° C or lower, still more preferably 715 ° C or lower, and particularly preferably 710 ° C or lower. Further, in order to improve the plane deformation of the glass, it is necessary to raise the temperature at the portion from the float bath outlet to the gradual cooling path, but there is no need to increase the temperature at that time. Therefore, no load is applied to the heater used for heating, and the life of the heater is less likely to be affected.

For the same reason as the strain point, the glass transition point of the alkali-free glass substrate of the present invention is preferably 730 占 폚 or higher, more preferably 740 占 폚 or higher, and still more preferably 750 占 폚 or higher. Further, it is preferably 780 DEG C or lower, more preferably 775 DEG C or lower, and particularly preferably 770 DEG C or lower.

The alkali-free glass substrate of the present invention has an average thermal expansion coefficient of 30 x 10 ^-7 to 43 x 10 ^-7 / 占 폚 at 50 to 350 占 폚, has a high thermal shock resistance, The productivity of the city can be increased. In the glass of the present invention, it is preferable that the average thermal expansion coefficient at 50 to 350 ° C is 35 × 10 ^-7 to 40 × 10 ^-7 / ° C. The average thermal expansion coefficient at 50 to 350 占 폚 is preferably 42 占^10-7 / 占 폚 or less, more preferably 41 占^10-7 / 占 폚 or less, further preferably 40 占^10-7 / 占 폚 or less.

The specific gravity of the alkali-free glass substrate of the present invention is preferably 2.62 or less, more preferably 2.60 or less, still more preferably 2.58 or less.

Further, the non-alkali glass substrate of the present invention preferably has a modulus of elasticity of 31 MN / kg or more. If it is less than 31 MNm / kg, it is difficult to obtain the convex portion selectivity at the time of polishing due to the self-weight deflection. More preferably not less than 32 MNN / kg.

In the alkali-free glass substrate of the present invention, the Young's modulus is preferably 78 GPa or more. When the glass substrate is less than 78 GPa, the glass substrate is deformed at the time of polishing to make it difficult to obtain smoothness, and it is difficult to obtain convex selectivity at the time of polishing due to deformation. More preferably 80 GPa or more, further preferably 81 GPa or more, particularly preferably 82 GPa or more.

In the alkali-free glass substrate of the present invention, the photoelastic constant is preferably 30 nm / MPa / cm or less.

The glass substrate may have birefringence due to the stress generated when the liquid crystal display panel manufacturing process or the liquid crystal display device is used, so that the black display may become gray and the contrast of the liquid crystal display may be lowered. By reducing the photoelastic constant to 30 nm / MPa / cm or less, this phenomenon can be suppressed to a small extent. Preferably 29 nm / MPa / cm or less, more preferably 28.5 nm / MPa / cm or less, further preferably 28 nm / MPa / cm or less.

The non-alkali glass substrate of the present invention preferably has a photoelastic constant of at least 23 nm / MPa / cm, more preferably at least 25 nm / MPa / cm, in consideration of ease of securing other physical properties.

The photoelastic constant can be measured at a measurement wavelength of 546 nm by a disk compression method.

The non-alkali glass substrate of the present invention preferably has a relative dielectric constant of 5.6 or more.

In the case of an in-cell type touch panel (one incorporating a touch sensor in a liquid crystal display panel) disclosed in Japanese Patent Application Laid-Open No. 2007-70092, the touch sensitivity of the touch sensor is improved, the driving voltage is decreased, It is preferable that the relative dielectric constant of the glass substrate is high. By setting the relative dielectric constant to 5.6 or more, the sensing sensitivity of the touch sensor is improved. Preferably at least 5.8, more preferably at least 5.9, and even more preferably at least 6.0.

The relative dielectric constant can be measured by the method described in JIS C-2141.

In the alkali-free glass substrate of the present invention, the temperature T ₂ at which the viscosity η is 10 ² poises (dPa 揃 s) is 1710 ° C. or less, preferably 1710 ° C. or less, more preferably 1700 ° C. or less Preferably 1690 占 폚 or lower, particularly preferably 1660 占 폚 or lower, so that dissolution is relatively easy.

In the alkali-free glass substrate of the present invention, the temperature T ₄ at which the viscosity η is 10 ⁴ poise is 1330 ° C. or less, preferably 1320 ° C. or less, more preferably 1315 ° C. or less, further preferably 1310 ° C. or less , Particularly preferably 1300 DEG C or less, and is suitable for float forming.

Further, in the alkali-free glass substrate of the present invention, a glass transition temperature of 1350 占 폚 or lower is preferable because the glass substrate can be easily formed by the float method. Preferably 1330 ° C or lower, more preferably 1310 ° C or lower, further preferably 1300 ° C or lower.

The glass transition temperature in this specification is a temperature at which glass particles pulverized in a platinum dish are placed and subjected to a heat treatment in an electric furnace controlled at a constant temperature for 17 hours and observed by an optical microscope after the heat treatment, And the average value of the minimum temperature at which crystals are not precipitated.

[Example]

(Example 1, Comparative Example 1)

Ingredients of the respective components were combined so as to have the target composition shown in Table 1, and the mixture was melted in a continuous melting furnace and subjected to plate molding by a float method to obtain a non-alkali glass substrate.

The obtained glass substrate (920 mm x 730 mm, thickness 0.5 mm) was supplied with a cerium oxide aqueous solution from the slurry supply hole of the holding support platen to a pad having a groove with a groove pitch of 4.5 mm, a groove width of 1.5 mm and a groove depth of 1 to 1.5 mm And polishing was carried out. During the course of the process, the glass was pulled out, and the amount of polishing and the height of curvature of the main surface of the glass substrate were measured and repeatedly carried out. The relationship between the amount of polishing and the height of curvature in terms of bending at a pitch of 20 mm was determined.

From the results, it was found that the polishing amount X (占 퐉) of the glass substrate when the height of the bending converted into the bending of 20 mm pitch on the main surface of the glass substrate changes from 0.14 占 퐉 to 0.10 占 퐉, Respectively. Further, the bending height of the main surface of the glass substrate before and after the finish polishing was measured at a pitch of 20 mm, and the surface roughness Ra of 5 탆 square from the main surface of the glass substrate after the finish polishing. The surface roughness Ra was measured with NanoScope IIIa manufactured by Digital Instruments at a scan rate of 1 Hz and a surface roughness of 5 탆 square at 256 points / scan.

The results are shown in Table 2 below.

Further, for the alkali-free glass substrate obtained in the above procedure, the strain point, the Young's modulus, the non-elasticity rate, and the photoelastic constant were measured. The results are shown in Table 2. The parentheses indicate the calculated values.

Although the present invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the scope and spirit of the present invention.

The present application is based on Japanese Patent Application No. 2013-251021 filed on December 4, 2013, the contents of which are incorporated herein by reference.

G: Glass plate
10: Polishing apparatus
12: Polishing head
14: Plate
16: Glass holding member
18: Seal material
20: Glass holding plate
22: Canvas
23: air chamber
24:
26: Opening harness
28: Seal material
30: Plate holding plate
40: Truing stone
42: frame
44: Water nozzle
46: injection hole
48: Washing water

Claims (7)

A finish polishing method for a glass substrate for polishing a main surface of a glass substrate using a polishing slurry containing cerium oxide as abrasive grains,
Wherein the composition of said glass substrate is the following alkali-free glass,
When the abrasion amount of the glass substrate is X (mu m) when the height of the bending converted into the curvature of 20 mm pitch on the main surface of the glass substrate changes from 0.14 mu m to 0.10 mu m, 0.04 / X is 0.12 or more Wherein the step of grinding the glass substrate comprises grinding the glass substrate at a predetermined temperature.
A temperature T ₂ at which the glass transition temperature is 680 to 735 ° C, an average thermal expansion coefficient at 50 to 350 ° C is 30 × 10 ^-7 to 43 × 10 ^-7 / ° C, and a glass viscosity is 10 ² dPa · s is 1710 ° C or less , The temperature T ₄ at which the glass viscosity becomes 10 ⁴ dPa · s is 1330 ° C. or less, and the glass transition temperature
SiO ₂ 63 to 74,
Al ₂ O ₃ 11.5 to 16,
B ₂ O ₃ 1.5 to 5 or less,
MgO 5.5 to 13,
CaO 1.5 to 12,
SrO 1.5 to 9,
BaO 0 to 1,
ZrO ₂ 0 to 2
MgO + CaO + SrO + BaO is 15.5 to 21,
An alkali-free glass having a MgO / (MgO + CaO + SrO + BaO) of 0.35 or more, CaO / (MgO + CaO + SrO + BaO) of 0.50 or less and SrO / (MgO + CaO + SrO + BaO) The finish polishing method for a glass substrate according to claim 1, wherein the height of the bending in terms of bending at a pitch of 20 mm on the main surface of the glass substrate before finish polishing is 0.2 탆 or less. The finish polishing method for a glass substrate according to claim 1 or 2, wherein the main surface of the glass substrate molded by the float method is finely polished. An alkali-free glass substrate finishing polished using the finish polishing method of the glass substrate according to any one of claims 1 to 3. 5. The alkali-free glass substrate according to claim 4, wherein the height of the bending in terms of bending at a pitch of 20 mm on the main surface of the glass substrate after the finish polishing is 0.07 占 퐉 or less. The alkali-free glass substrate according to claim 4 or 5, wherein the main surface of the glass substrate after the finish polishing has a surface roughness of not more than 0.30 nm at 5 mu m square. The alkali-free glass substrate according to any one of claims 4 to 6, wherein at least one side has a length of 900 mm or more.

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