KR101654753B1 - Glass substrate for flat panel displays and method for manufacturing same - Google Patents

Abstract

The present invention provides a glass substrate for a flat panel display and a flat panel display, which both have a low heat shrinkage ratio and suppression of a luminescence.
The glass substrate for a flat panel display of the present invention, in mol%
55 to 80% of SiO ₂ ,
Al ₂ O ₃ : 8 to 20%
B ₂ O ₃ : 0 to 8%,
MgO: more than 0 to 15%
CaO: 0 to 20%
SrO: 0 to 15%
BaO: 0 to 10%
≪ / RTI >
SiO ₂ + 2 x Al ₂ O ₃ is 100% or less,
The molar ratio B ₂ O ₃ / (SiO ₂ + Al ₂ O ₃ ) is 0 to 0.12,
The molar ratio MgO / RO is in the range of 0.15 to 0.9,
The devitrification temperature is lower than 1280 DEG C,
The heat shrinkage rate is 3 ppm or more and less than 75 ppm as shown by the following formula after the temperature is raised from room temperature to 10 ° C / minute, held at 550 ° C for 2 hours, and then decreased to 10 ° C /
Heat shrinkage rate (ppm) = (shrinkage of glass before and after heat treatment / length of glass before heat treatment) x 10 ⁶

Description

TECHNICAL FIELD [0001] The present invention relates to a glass substrate for a flat panel display,

The present invention relates to a glass substrate for a flat panel display and a manufacturing method thereof. More particularly, the present invention relates to a glass substrate for a flat panel display (hereinafter referred to as a low-temperature-polycrystalline-silicon thin-film-transistor (LTPS-TFT)). The present invention also relates to a glass substrate for an oxide semiconductor thin film transistor (hereinafter referred to as an OS-TFT (Oxide-Semiconductor Thin-Film-Transistor)) flat panel display. More particularly, the present invention relates to a glass substrate for a flat panel display in which the flat panel display is a liquid crystal display. Or the flat panel display is an organic EL display.

In a display mounted on a portable device or the like, it is desired to apply LTPS to the manufacture of a thin film transistor (TFT) for reasons such as reducing power consumption. However, in the production of an LTPS-TFT, Heat treatment is required. On the other hand, the display of a small portable device has recently been required to have high precision. As a result, the thermal shrinkage of the glass substrate, which occurs during the manufacture of the display panel, which causes the pitch shift of the pixels, becomes a problem. In addition, the glass substrate on which the OS-TFT is formed also has a problem of suppressing heat shrinkage.

Generally, the heat shrinkage rate of the glass substrate can be reduced by improving the strain point of the glass or lowering the thermal expansion coefficient.

Patent Documents 1 and 2 disclose a glass substrate on which a heat shrinkage rate is noted. Patent Documents 1 and 2 all disclose inventions relating to a glass substrate for a liquid crystal display.

Japanese Patent Application Laid-Open No. 2004-315354 Japanese Patent Application Laid-Open No. 2007-302550

The glass substrate described in Patent Document 1 has a high strain point, but a high devitrification temperature, which is problematic in that devitrification is likely to occur. For example, the glass substrate disclosed in Patent Document 1 has a problem in that the problem of slippery becomes remarkable in a molding method such as an overflow down-draw method in which the productivity of the glass substrate surface can be improved by omitting the polishing process or the like . Further, since the glass substrate described in Patent Document 2 has a sufficiently high strain point, if it is desired to reduce the heat shrinkage rate, it is necessary to extremely slow down the cooling rate within the temperature range in which the flat glass after molding is in the vicinity of Tg. As a result, the glass substrate described in Patent Document 2 has a problem in that it is difficult to reduce the heat shrinkage rate while maintaining the productivity.

Accordingly, it is an object of the present invention to provide a glass substrate that achieves both a low heat shrinkage ratio and suppression of delamination. In particular, it is an object of the present invention to provide a glass substrate for a flat panel display suitable for a flat panel display using an LTPS-TFT and a manufacturing method thereof. Further, it is also an object of the present invention to provide a glass substrate for a flat panel display and a method of manufacturing the same, both of which have a suitable low heat shrinkage ratio and suppression of devitrification, even in a flat panel display using an OS-TFT.

The present inventors have found out that by studying the glass composition, it is possible to provide a glass substrate for a flat panel display suitable for a flat panel display using an LTPS-TFT, which has both a low heat shrinkage ratio and suppression of slipping, and completed the present invention . Further, the present inventors have also found that the above-mentioned glass substrate has both a low heat shrinkage rate that can be used for an OS-TFT and suppression of slip, and thus accomplished the present invention.

The present invention is as follows.

[One]

In mol%

55 to 80% of SiO ₂ ,

Al ₂ O ₃ : 8 to 20%

B ₂ O ₃ : 0 to 8%,

MgO: more than 0% to 15%

CaO: 0 to 20%

SrO: 0 to 15%

BaO: 0 to 10%

≪ / RTI >

SiO ₂ + 2 x Al ₂ O ₃ is 100% or less,

The molar ratio B ₂ O ₃ / (SiO ₂ + Al ₂ O ₃ ) is 0 to 0.12,

The molar ratio MgO / RO (where RO is the sum of MgO, CaO, SrO, and BaO) is in the range of 0.15 to 0.9, the devitrification temperature is less than 1280 占 폚,

Wherein the glass substrate for a flat panel display has a heat shrinkage rate of not less than 3 ppm and not more than 75 ppm as shown by the following formula after heating from room temperature to 10 占 폚 / min, holding at 550 占 폚 for 2 hours,

Heat shrinkage rate (ppm) = (shrinkage of glass before and after heat treatment / length of glass before heat treatment) x 10 ⁶

[2]

In mol%

63 to 72% of SiO ₂ ,

Al ₂ O ₃ : 11 to 15%

(1). ≪ / RTI >

[3]

SiO ₂ -Al ₂ O _3/2 a glass substrate according to the range of [1] or [2] of 45% to 64%.

[4]

In mol%

63 to 70% of SiO ₂ ,

Al ₂ O ₃ : 12 to 15%

B ₂ O ₃ : 1.5 to 7%,

MgO: 3 to 11%

CaO: 5 to 11%

SrO: 0 to 4%

BaO: 0 to 4%

(1) to (3).

[5]

In mol%

BaO: 0 to 2%

[1] The glass substrate according to any one of [1] to [4].

[6]

SnO ₂ and Fe ₂ O ₃ ,

In mol%

SnO _2: 0.03 to 0.15%,

The glass substrate according to any one of [1] to [5], wherein the total amount of SnO ₂ and Fe ₂ O ₃ is in the range of 0.05 to 0.2%.

[7]

In mol%

The glass substrate according to any one of [1] to [6], wherein the total amount of Li ₂ O, Na ₂ O and K ₂ O is 0.01 to 0.5 mol%.

[8]

The glass substrate according to any one of [1] to [7], which is substantially free of As ₂ O ₃ and Sb ₂ O ₃ .

[9]

The glass substrate according to any one of [1] to [8], wherein an average thermal expansion coefficient at 100 to 300 캜 is 28 占^10-7占 폚 ^-1 or more and less than 50 占^10-7占 폚 ^-1 .

[10]

The glass substrate according to any one of [1] to [9], which is a glass substrate molded by an overflow down-draw method.

[11]

A flat panel display in which a thin film transistor formed of LTPS or an oxide semiconductor is formed on a surface of a glass substrate, wherein the glass substrate is a glass substrate according to any one of [1] to [10].

[12]

A flat panel display wherein the flat panel display is a liquid crystal display or an organic EL display.

[13]

A melting step of melting a glass raw material combined in a predetermined composition,

A molding step of molding the molten glass dissolved in the melting step into a flat glass,

The flat panel display according to any one of [1] to [10], wherein the step of slowly cooling the flat glass includes a slow cooling step of controlling cooling conditions of the flat glass to reduce the heat shrinkage rate of the flat glass Wherein the method comprises the steps of:

[14]

[13] The production process according to [13], wherein the dissolving step dissolves the glass raw material by using at least direct energization heating.

[15]

[13] The method according to [13] or [14], wherein the melting step is a step of dissolving the glass raw material in a melting tank comprising at least a high-temperature zirconia refractory material.

[16]

The slow cooling step may be any one of [13] to [15], wherein the slow cooling step is carried out so that the flat glass-like glass has a cooling rate of 30 to 300 캜 / ≪ / RTI >

[17]

SiO _2: 55 to 80%,

Al ₂ O ₃ : 8 to 20%

B ₂ O ₃ : 0 to 5%,

MgO: more than 0% to 15%

CaO: 0 to 20%

SrO: 0 to 15%

BaO: 0 to 2%

≪ / RTI >

SiO ₂ + 2 x Al ₂ O ₃ is 100% or less,

The molar ratio B ₂ O ₃ / (SiO ₂ + Al ₂ O ₃ ) is 0 to 0.12,

The molar ratio of MgO / RO (wherein RO is the sum of MgO, CaO, SrO and BaO) is in the range of 0.15 to 0.9, the temperature is raised at a rate of 10 ° C / min from the room temperature and maintained at 550 ° C for 2 hours, Deg.] C / minute to a room temperature, and has a heat shrinkage rate of less than 60 ppm as shown by the following formula.

Heat shrinkage rate (ppm) = (shrinkage of glass before and after heat treatment / length of glass before heat treatment) x 10 ⁶

According to the present invention, it is possible to provide a glass substrate for a flat panel display, which has both a low heat shrinkage ratio and suppression of slipping. In particular, it is possible to provide a glass substrate for flat panel display suitable for a flat panel display using LTPS-TFT or OS-TFT.

The glass substrate for a flat panel display of the present invention, in mol%

55 to 80% of SiO ₂ ,

Al ₂ O ₃ : 8 to 20%

B ₂ O: 0 to 8%,

MgO: more than 0% to 15%

CaO: 0 to 20%

SrO: 0 to 15%

BaO: 0 to 10%

≪ / RTI >

SiO ₂ + 2 x Al ₂ O ₃ is 100% or less,

The molar ratio B ₂ O ₃ / (SiO ₂ + Al ₂ O ₃ ) is 0 to 0.12,

The molar ratio MgO / RO (wherein RO is the sum of MgO, CaO, SrO and BaO) is in the range of 0.15 to 0.9,

The devitrification temperature is lower than 1280 DEG C,

The heat shrinkage rate is 3 ppm or more and less than 75 ppm as shown by the following formula after the temperature is raised from room temperature to 10 ° C / minute, held at 550 ° C for 2 hours, and then decreased to 10 ° C /

Heat shrinkage rate (ppm) = (shrinkage of glass before and after heat treatment / length of glass before heat treatment) x 10 ⁶

Hereinafter, a glass substrate for a flat panel display of the present invention will be described.

SiO ₂ is a skeleton component of glass, and is therefore an essential component. When the content is decreased, the acid resistance is lowered, the strain point is lowered, and the coefficient of thermal expansion tends to increase. If the SiO ₂ content is too small, it becomes difficult to make the glass substrate low in density. On the other hand, when the content of SiO ₂ is too large, the melt viscosity tends to become remarkably high and the dissolution becomes difficult. If the SiO ₂ content is too large, resistance to devitrification tends to be lowered. The content of SiO ₂ is in the range of 55 to 80 mol%. The content of SiO ₂ is preferably 60 to 75 mol%, more preferably 62 to 73 mol%, still more preferably 63 to 72 mol%, still more preferably 63 to 70 mol%, still more preferably 65 to 70 mol% , Still more preferably 65 to 69 mol%, still more preferably 65 to 68 mol%.

Al ₂ O ₃ is an essential component for suppressing the phase separation and increasing the strain point. If the content of Al ₂ O ₃ is too small, the glass tends to be dispersed. When the Al ₂ O ₃ content is too small, the strain point is lowered. When the content of Al ₂ O ₃ is too small, the Young's modulus also decreases, and the etching rate due to acid (acid) also tends to decrease. If the content of Al ₂ O ₃ is too large, the glass transition temperature rises and the resistance to devitrification tends to deteriorate, so that the moldability tends to deteriorate. From this viewpoint, the content of Al ₂ O ₃ is in the range of 8 to 20 mol%. The content of Al ₂ O ₃ is preferably 8 to 18 mol%, more preferably 9 to 17 mol%, still more preferably 11 to 15 mol%, still more preferably 12 to 15 mol%, still more preferably 12 to 15 mol% 14 mol%.

B ₂ O ₃ is a component that lowers the high-temperature viscosity of the glass and improves the meltability. That is, the viscosity is lowered in the vicinity of the melting temperature, thereby improving the solubility. It is also a component that lowers the melt temperature. When the content of B ₂ O ₃ is small, the solubility is lowered and the resistance to devitrification tends to be lowered. When the content of B ₂ O ₃ is excessively large, the strain point is lowered and the heat resistance is lowered. Also, if the content of B ₂ O ₃ is excessively large, the Young's modulus deteriorates. In addition, devitrification tends to occur due to the volatilization of B ₂ O ₃ during glass forming. Particularly, since a glass having a high strain point tends to have a high molding temperature, the above volatilization is promoted, and generation of a slag is remarkable. In addition, due to the volatilization of B ₂ O ₃ at the time of melting the glass, the heterogeneity of the glass becomes remarkable, and consequently, spots are likely to occur. From this point of view, the B ₂ O ₃ content is in the range of 0 to 8 mol%, preferably 0 to 5 mol%. The B ₂ O ₃ content is preferably in the range of 0.1 to 5 mol%, more preferably 1.5 to 5 mol%, and still more preferably 1.5 to 4.5 mol%. On the other hand, in the case of emphasizing insolubility, the content of B ₂ O ₃ is preferably 0 to 7 mol%, more preferably 0.1 to 7 mol%, still more preferably 1 to 7 mol%, still more preferably 1.5 to 7 mol% , Still more preferably from 1.5 to 6.5 mol%, still more preferably from 2 to 6 mol%. The B ₂ O ₃ content is suitably determined in consideration of both the solubility and the resistance to devitrification. The B ₂ O ₃ content is preferably in the range of 1 to 5 mol%, more preferably 1.5 to 5 mol%, and still more preferably 1.5 to 4.5 mol% in consideration of both the solubility and the emulsion resistance.

MgO is an essential component for improving solubility. In addition, among the alkaline earth metals, since the component is difficult to increase in density, if the content is relatively increased, it is easy to achieve the low density. The solubility can be improved. However, if the content of MgO is too large, the glass transition temperature rises sharply, so that the glass transition temperature is particularly susceptible to devitrification in the molding step. If the MgO content is too large, the acid resistance tends to decrease. From this viewpoint, the MgO content is more than 0 mol% to 15 mol%, preferably 1.5 to 15 mol%, more preferably 2 to 15 mol%, still more preferably 2 to 12 mol%, still more preferably 3 to 11 mol% , Even more preferably from 4 to 10 mol%, still more preferably from 5 to 9 mol%.

CaO is an effective component for improving the solubility of glass without sharply raising the glass transition temperature. In addition, among the alkaline earth metals, since the component is difficult to increase in density, if the content is relatively increased, it is easy to achieve the low density. If the content is too small, resistance to devitrification tends to occur. If the CaO content is excessively high, the thermal expansion coefficient increases and the density tends to increase. From this viewpoint, the CaO content is in the range of 0 to 20 mol%, preferably 3 to 15 mol%, more preferably 4 to 13 mol%, still more preferably 5 to 11 mol%, and still more preferably 7 to 11 mol% .

SrO is a component that can lower the glass transition temperature. SrO is not essential, but if it is contained, resistance to devitrification and solubility are improved. However, if the SrO content is excessively large, the density increases. From this viewpoint, the SrO content is 0 to 15 mol%, preferably 0 to 10 mol%, more preferably 0 to 7 mol%, still more preferably 0 to 4 mol%, still more preferably 0 to 2 mol% , Preferably 0 to 1.5 mol%, further preferably 0 to 1 mol%. When it is desired to lower the density of the glass, it is preferable that SrO is not substantially contained.

BaO is a component that can lower the glass transition temperature. Though not essential, if contained, resistance to devitrification and solubility are improved. However, if the content of BaO is excessively large, the density increases. Further, the BaO content is 0 to 10 mol%, preferably 0 to 4 mol%, more preferably 0 to 3 mol%, still more preferably 0 to 3 mol%, in view of the environmental load and the tendency of the thermal expansion coefficient to increase. More preferably 0 to 2 mol%, still more preferably 0 to 2 mol%, still more preferably 0 to 1 mol%, still more preferably 0 to 0.5 mol%, still more preferably substantially not contained.

Li ₂ O and Na ₂ O are components that may elute from the glass substrate to deteriorate the TFT characteristics or increase the coefficient of thermal expansion of the glass to damage the substrate during heat treatment. Li ₂ O and Na ₂ O are preferably substantially free from all of them.

K ₂ O is a component that promotes the clarity by increasing the basicity of the glass. It is also a component that improves the solubility and lowers the resistivity of the molten glass. Although it is not essential, if it is contained, the resistivity of the molten glass is lowered, and current can be prevented from flowing to the refractory constituting the melting tank, and erosion of the melting tank can be suppressed. Further, in the case where the refractory constituting the melting tank contains zirconia, since the melting vessel is eroded, the release of zirconia from the melting vessel to the glass can be inhibited, and therefore, the failure due to zirconia can be suppressed. In addition, since the glass viscosity in the vicinity of the melting temperature is lowered, the solubility and clarifying property are improved. On the other hand, if the content of K ₂ O is excessively large, there is a fear that the TFT characteristics may deteriorate due to elution from the glass substrate. In addition, the coefficient of thermal expansion also tends to increase. From this viewpoint, the K ₂ O content is preferably in the range of 0 to 0.8 mol%, more preferably 0.01 to 0.5 mol%, and still more preferably 0.1 to 0.3 mol%.

ZrO ₂ and TiO ₂ are components that improve the chemical durability and strain point of glass. Although ZrO ₂ and TiO ₂ are not essential components, they contain an increased strain point and improved acid resistance. However, if the amount of ZrO _{2 and} the amount of TiO ₂ are excessively large, the devitrification temperature remarkably increases, and the resistance to devitrification and the formability are sometimes lowered. In particular, ZrO ₂ has a high melting point and is difficult to dissolve, so that a part of the raw material is deposited on the bottom of the melting furnace. The incorporation of these components into the glass substrate results in the inclusion of the quality of the glass. Further, TiO ₂ is not preferable for display substrates because it is a component for coloring glass. From this viewpoint, in the glass substrate of the present invention, the content of ZrO ₂ and TiO ₂ is preferably 0 to 5 mol%, more preferably 0 to 3 mol%, still more preferably 0 to 2 mol%, and 0 to 1 mol % Is more preferable. Even more preferably, the glass substrate of the present invention does not substantially contain ZrO ₂ and TiO ₂ .

ZnO is a component that improves internal BHF resistance and solubility. However, it is not an essential component. If the ZnO content is excessively large, the melt temperature increases, the strain point decreases, and the density tends to increase. From this point of view, the ZnO content is preferably in the range of 0 to 5 mol%, more preferably 0 to 3 mol%, still more preferably 0 to 2 mol%, still more preferably 0 to 1 mol%. It is preferable that ZnO is not substantially contained.

P ₂ O ₅ is a component which lowers the high-temperature viscosity and improves the solubility. However, it is not an essential component. If the content of P ₂ O ₅ is excessively large, the P ₂ O ₅ is volatilized at the time of dissolving the glass, whereby the heterogeneity of the glass becomes remarkable, and consequently, spots are likely to occur. In addition, the acid resistance is remarkably deteriorated. In addition, milky white easily occurs. From this point of view, the content of P ₂ O ₅ is preferably in the range of 0 to 3 mol%, more preferably 0 to 1 mol%, still more preferably 0 to 0.5 mol%, particularly preferably substantially not contained.

The glass substrate of the present invention may contain a refining agent. The cleaning agent is not particularly limited as long as it has a small environmental load and is excellent in refinement of the glass. Examples of the cleaning agent include at least one selected from the group of metal oxides of Sn, Fe, Ce, Tb, Mo, Sb and W . SnO ₂ is suitable as the fining agent. If the content of the refining agent is too small, the quality of the bubble deteriorates, and if the content is excessively large, it may cause staining and coloring. The content of the fining agent depends on the type of the fining agent and the composition of the glass. For example, the total amount of SnO ₂ , Fe ₂ O ₃ and Sb ₂ O ₃ is preferably 0.05 to 0.20 mol%.

SnO ₂ is a refining agent that obtains a refining effect even when the temperature is higher than or equal to 1600 ° C .; a glass substrate for a flat panel display (for example, a total amount of alkali metal oxides is 0 to 0.8 mol%) which can contain only a small amount of alkali metal oxides Are some of the purifying agents available. However, since SnO ₂ is a component which is liable to cause a slag, it is not preferable to add a large amount of SnO ₂ from the viewpoint of suppressing the slag.

In addition, since a glass having a high strain point (for example, a glass having a strain point of 670 DEG C or higher) tends to have a higher melt temperature than a glass having a low strain point (for example, a glass having a strain point of less than 670 DEG C) The temperature of the molten glass in the molding step may have to be made higher than that of the glass having a low strain point. Here, from the viewpoint of creep resistance and heat resistance, the formed body used in the overflow down draw method is preferably composed of a refractory containing zirconia. When the overflow down draw is employed as the molding method, the temperature of the molded body needs to be increased as the temperature of the molten glass in the molding step is increased. However, when the temperature of the molded article is increased, there is a problem that zirconia elutes from the molded article, and the zirconia is easily released. In the particularly advantageous to containing a large amount of SnO _2, due to the zirconia it is liable to cause devitrification of the SnO _2.

In addition, a glass having a high strain point (for example, a glass having a strain point of 670 DEG C or higher) tends to have a higher melting point of a glass raw material than a glass having a low strain point (for example, a glass having a strain point of less than 670 DEG C) . Here, from the viewpoint of erosion resistance, it is preferable that the melting tank for performing the melting process comprises a high zirconia refractory containing zirconia. From the viewpoint of energy efficiency, it is preferable to dissolve the glass raw material by a combination of electric melting or electric melting and other heating means. However, in the case of melting a glass which can contain only a small amount of alkali metal oxide while having a high strain point as described in the present invention, since the resistivity of the molten glass is large, a current flows in the high-refractory zirconia refractory, The problem that the zirconia elutes becomes easy to occur. When the zirconia is eluted, there is a fear that the above-described zirconia disintegration and zirconia-induced disintegration of SnO ₂ may occur.

In other words, from the viewpoint of suppressing the occurrence of dislocation of SnO ₂ due to zirconia, it is not preferable to contain SnO ₂ in an amount exceeding 0.2 mol% in the glass substrate of the present invention. From this viewpoint, the SnO ₂ content is preferably in the range of, for example, 0.01 to 0.2 mol%, more preferably 0.03 to 0.15 mol%, and still more preferably 0.05 to 0.12 mol%.

Fe ₂ O ₃ has a function as a refining agent and is a component that lowers the resistivity of the molten glass. In order to lower the resistivity of the molten glass, it is preferable that the glass is high in high-temperature viscosity and poorly soluble. However, if the content of Fe ₂ O ₃ is excessively large, the glass is colored and the transmittance is lowered. Therefore, the Fe ₂ O ₃ content is in the range of 0 to 0.1 mol%, preferably 0 to 0.05 mol%, more preferably 0.001 to 0.05 mol%, still more preferably 0.003 to 0.05 mol% Is in the range of 0.005 to 0.03 mol%.

In the present invention, the refining agent is preferably used in combination of SnO ₂ and Fe ₂ O ₃ . From the viewpoint of disintegration, it is as described above that it is not preferable to contain a large amount of SnO ₂ . However, in order to sufficiently obtain the purifying effect, it is required to contain the purifying agent at a predetermined value or more. Therefore, by using SnO ₂ and Fe ₂ O ₃ in combination, it is possible to produce a glass substrate with a sufficient purifying effect and few bubbles, even if the content of SnO ₂ is not increased as much as the occurrence of slag. The total amount of SnO ₂ and Fe ₂ O ₃ is preferably in the range of 0.05 to 0.2 mol%, more preferably 0.08 to 0.2 mol%, still more preferably 0.1 to 0.18 mol%, still more preferably 0.1 to 0.15 mol% mol%.

If the molar ratio (SnO ₂ / (SnO ₂ + Fe ₂ O ₃ )) of the content of SnO ₂ to the total amount of SnO ₂ and Fe ₂ O ₃ is excessively large, disintegration tends to occur. So that the glass may be colored. Therefore, it is preferably in the range of 0.55 to 1, more preferably 0.6 to 1, still more preferably 0.65 to 1, still more preferably 0.65 to 0.95, still more preferably 0.65 to 0.9.

It is preferable that the glass substrate of the present invention contains substantially no As ₂ O ₃ in view of environmental load. In the glass substrate of the present invention, Sb ₂ O ₃ preferably contains 0 to 0.5 mol%, more preferably 0 to 0.1 mol%, most preferably substantially no Sb ₂ O ₃ in view of environmental load.

The glass substrate of the present invention is preferably substantially free of PbO and F for environmental reasons.

In the present specification, the term " substantially not containing " means not using a substance as a raw material for these components in the glass raw material, and includes components contained as impurities in glass raw materials of other components, It does not exclude the incorporation of components eluted into the solution.

When the content of SiO ₂ + 2 x Al ₂ O _{3, which} is the sum of the content of SiO _{2 and} the content of Al ₂ O ₃ , is too small, the strain point tends to decrease, while if it is excessively large, the resistance to devitrification tends to deteriorate. Therefore, SiO ₂ + 2 x Al ₂ O ₃ is 100 mol% or less, preferably 75 to 100 mol%, more preferably 75 to 97 mol%, more preferably 80 to 96 mol%, still more preferably 85 to 95 mol% More preferably 85 to 95 mol%, still more preferably 87 to 95 mol%, still more preferably 89 to 95 mol%, still more preferably 89 to 94 mol%.

If the content and the difference SiO ₂ -Al ₂ O _3/2, the value of the Al ₂ O ₃ 1/2 of SiO ₂ is too small, the etching rate is improved but there is a substantial risk of degradation is full. If the value is too high, there is a fear that the etching rate is lowered. In view of _{this, SiO 2 -Al 2 O 3/} 2 is preferable, and preferably from 45 to 69mol%, more preferably from 45 to 64mol%, more preferably from 50 to 63mol%, more preferably not more than 69mol% Is 55 to 62 mol%, still more preferably 55 to 61.5 mol%, still more preferably 55 to 61 mol%.

The molar ratio B ₂ O ₃ / (SiO ₂ + Al ₂ O ₃ ) is mainly an index of strain and resistance. As described above, when the content of B ₂ O ₃ is small, the solubility and resistance to devitrification decrease. On the other hand, when the content is increased, the strain point is lowered and the heat resistance is lowered. In addition, when the content is large, the acid resistance and the Young's modulus tend to decrease. B ₂ O ₃ / (SiO ₂ + Al ₂ O ₃ ) basically has a similar tendency. Therefore, the molar ratio B ₂ O ₃ / (SiO ₂ + Al ₂ O ₃ ) is in the range of 0 to 0.12. If B ₂ O ₃ / (SiO ₂ + Al ₂ O ₃ ) is more than 0.12, the strain point can not be made sufficiently high, and the resistance to devitrification tends to decrease as it approaches zero. The molar ratio B ₂ O ₃ / (SiO ₂ + Al ₂ O ₃ ) is preferably 0 to 0.1, more preferably 0.001 to 0.08, still more preferably 0.005 to 0.08, still more preferably 0.01 to 0.075, Preferably in the range of 0.01 to 0.07. On the other hand, in the case of emphasizing the resistance to devitrification, the molar ratio B ₂ O ₃ / (SiO ₂ + Al ₂ O ₃ ) is 0 to 0.12, preferably 0.01 to 0.10, more preferably 0.02 to 0.09, 0.025 to 0.085. In addition, (SiO ₂ + Al ₂ O ₃ ) / B ₂ O _{3 which} is an inverse number of the molar ratio is preferably 8.3 or more when B ₂ O ₃ is more than 0 mol%.

B ₂ O ₃ and P ₂ O ₅ in the total amount of B ₂ O ₃ + P ₂ O ₅ is if too small, there is a tendency that the solubility is decreased, is too large, B ₂ O ₃ + P ₂ O ₅ in the glass of the fire The homogeneity becomes remarkable, and it is easy for the fissure to occur and the strain point tends to be lowered. Therefore, B ₂ O ₃ + P ₂ O ₅ is preferably 0 to 8 mol%, more preferably 0 to 5 mol%, still more preferably 0.1 to 5 mol%, still more preferably 1.5 to 5 mol%. On the other hand, when emphasis is placed on impermeability, the content of B ₂ O ₃ + P ₂ O ₅ is preferably 0 to 7 mol%, more preferably 0.1 to 7 mol%, still more preferably 1 to 7 mol% Is in the range of 1.5 to 7 mol%, still more preferably 1.5 to 6.5 mol%, still more preferably 2 to 6.5 mol%, still more preferably 2 to 6 mol%. B ₂ O ₃ + P ₂ O ₅ is appropriately determined in consideration of both the solubility and the resistance to devitrification. B ₂ O ₃ + P ₂ O ₅ is preferably 1 to 8 mol%, more preferably 1.5 to 7 mol%, and still more preferably 2 to 5 mol% in consideration of both solubility and impermeability.

The molar ratio MgO / RO is an indicator of resistance. Note that RO is the sum of the contents of MgO, CaO, SrO and BaO (MgO + CaO + SrO + BaO). MgO / RO is preferably in the range of 0.15 to 0.9, more preferably 0.2 to 0.8, still more preferably 0.3 to 0.7, still more preferably 0.3 to 0.6. By setting these ranges, resistance to insolubility and solubility can be achieved at the same time. In addition, the density can be reduced.

SrO and BaO are components that can lower the glass transition temperature. Though not essential, if contained, resistance to devitrification and solubility are improved. However, if the content is excessively large, the density is increased. From this viewpoint, the sum of the SrO content and the BaO content (SrO + BaO) is preferably in the range of 0 to 15 mol%, more preferably 0 to 10 mol%, still more preferably 0 to 7 mol% Is 0 to 5 mol%, still more preferably 0 to 4 mol%, still more preferably 0 to 3 mol%, still more preferably 0 to 2 mol%. When the density is intended to be lowered, it is preferable that it is not substantially contained.

MgO, CaO, SrO, and BaO are components that improve solubility. If the amount of RO (MgO + CaO + SrO + BaO) which is the sum of the contents of MgO, CaO, SrO and BaO is too small, the solubility deteriorates. If the RO is excessively large, the strain point is lowered, the density is increased, and the Young's modulus is lowered. Also, if the RO is excessively large, the coefficient of thermal expansion tends to increase. From this viewpoint, RO is preferably in the range of 4 to 25 mol%, more preferably in the range of 7 to 21 mol%, and more preferably in the range of 12 to 19 mol%.

BaO is a component having a large load on the environment, and when the content thereof is large, the density of the glass becomes high, and it becomes difficult to reduce the weight of the glass substrate. The BaO / RO is preferably in the range of 0 to 0.5, more preferably 0 to 0.1, more preferably 0 to 0.07, still more preferably 0 to 0.05, still more preferably 0 to 0.02.

Li ₂ O, Na ₂ O and K ₂ O are components that enhance the basicity of the glass, facilitate the oxidation of the fining agent, and exert the fineness. It is also a component for lowering the viscosity at the melting temperature and improving the solubility. It is also a component that lowers the resistivity of the molten glass. Li ₂ O, Na ₂ O and K ₂ O are not essential, but if they are contained, the resistivity of the molten glass is lowered and the refinability and solubility are improved. Particularly, it is possible to prevent the current from flowing excessively to the refractory constituting the melting tank, and it is possible to suppress erosion of the melting tank. Further, in the case where the melting vessel contains zirconia, the dissolution of zirconia into the glass from the melting vessel can be suppressed, so that the elimination due to zirconia can also be suppressed. Further, since the viscosity of the molten glass is lowered, the solubility and clarifying property are improved. However, if R ₂ O, which is the sum of the contents of Li ₂ O, Na ₂ O and K ₂ O, is excessively large, there is a risk of eluting from the glass substrate and deteriorating TFT characteristics. Further, the coefficient of thermal expansion tends to increase. R ₂ O is preferably 0 to 0.8 mol%, more preferably 0.01 to 0.5 mol%, and still more preferably 0.1 to 0.3 mol%.

Since K ₂ O has a larger molecular weight than Li ₂ O or Na ₂ O, it is difficult to elute from the glass substrate. Therefore, when R ₂ O is contained, it is preferable to contain a larger amount of K ₂ O than Li ₂ O or Na ₂ O. If the ratio of Li ₂ O and Na ₂ O is large, there is a high possibility of eluting from the glass substrate to deteriorate TFT characteristics. The molar ratio K ₂ O / R ₂ O is preferably in the range of 0.5 to 1, more preferably 0.6 to 1, still more preferably 0.65 to 1, still more preferably 0.7 to 1.

The glass substrate of the present invention preferably has a glass transition temperature of preferably less than 1280 DEG C, more preferably 1260 DEG C or less, still more preferably 1250 DEG C or less, still more preferably 1235 DEG C or less, still more preferably 1215 DEG C or less . If the temperature is lower than 1280 ° C, the glass plate can be easily formed by the overflow down-draw method. By applying the overflow down-draw method, the step of polishing the surface of the glass substrate can be omitted, so that the surface quality of the glass substrate can be improved. In addition, the production cost can be reduced. If the slagging temperature is excessively high, the slag is liable to occur, which may cause deterioration in quality. Also, the application to the overflow down-draw method tends to become difficult.

The glass substrate of the present invention preferably has an average thermal expansion coefficient (100-300 ° C) at 100 ° C to 300 ° C of 28 x 10 ^-7 캜 ^-1 and less than 50 x 10 ^-7 캜 ^-1 , Is preferably less than 41 占^10-7占 폚 ^-1 , more preferably less than 28 占 41 占^0-7占 폚 ^-1 , more preferably less than 28 占 39 占^10-7占 폚 ^-1 , still more preferably 28 to 38 × 10 ^-7 ℃ ^-1 or less, still more preferably from 32 to less than 38 × 10 ^-7 ℃ ^-1, incidentally preferably greater than 34 × 10 ^-7 ℃ ^-1 to less than 38 × 10 ^{-7 -1} ℃ of Range. When the coefficient of thermal expansion is large, there is a tendency that heat shock or heat shrinkage ratio increases in the heat treatment step. In the manufacturing process of the LTPS-TFT, rapid heating and quenching are repeated, and the thermal shock applied to the glass substrate becomes large. Further, in a large glass substrate, a temperature difference (temperature distribution) is likely to be generated in the heat treatment step, and the probability of destruction of the glass substrate is increased. Further, if the thermal expansion coefficient is large, it is difficult to reduce the heat shrinkage ratio. On the other hand, if the coefficient of thermal expansion is small, it is difficult to match the thermal expansion coefficient with the surrounding material such as a metal or an organic adhesive agent formed on the glass substrate, and the peripheral member may peel off.

In general, when the glass substrate has a low strain point, heat shrinkage tends to occur in a heat treatment process at the time of manufacturing a display. The glass substrate of the present invention preferably has a strain point of at least 670 ° C, more preferably at least 680 ° C, more preferably at least 685 ° C, more preferably at least 690 ° C, even more preferably at least 695 ° C .

The glass substrate of the present invention has a heat shrinkage of less than 75 ppm, preferably less than 70 ppm, more preferably less than 65 ppm, and more preferably less than 60 ppm. The heat shrinkage ratio is preferably 55 ppm or less, more preferably 50 ppm or less, still more preferably 48 ppm or less, still more preferably 45 ppm or less. When the heat shrinkage rate (amount) is excessively large, a large pitch shift of the pixel is caused, and high-precision display can not be realized. In order to control the heat shrinkage rate (amount) to a predetermined range, it is preferable that the strain point of the glass substrate is 670 캜 or higher and the average thermal expansion coefficient (100-300 캜) is less than 50 x 10 ^-7 캜 ^-1 . The heat shrinkage rate is most preferably 0 ppm. However, when the heat shrinkage rate is 0 ppm, it is required to make the slow cooling process extremely long, or to perform the heat shrinkage reduction process (offline slow cooling) after the slow cooling and the cutting process. , The productivity is lowered and the cost is greatly increased. Considering productivity and cost, the heat shrinkage is preferably from 3 ppm to less than 75 ppm, more preferably from 5 ppm to less than 75 ppm, more preferably from 10 ppm to less than 65 ppm, still more preferably from 15 ppm to less than 60 ppm More preferably from 20 to 55 ppm, and still more preferably from 25 to 50 ppm.

The heat shrinkage rate is shown by the following formula after the heat treatment at the elevation temperature rate of 10 ° C / min and holding at 550 ° C for 2 hours. More specifically, the temperature is raised at a rate of 10 占 폚 / min from a room temperature, held at 550 占 폚 for 2 hours, and then lowered to a room temperature at a rate of 10 占 폚 / min.

Heat shrinkage rate (ppm) = (shrinkage of glass before and after heat treatment / length of glass before heat treatment) x 10 ⁶

Here, the " amount of shrinkage of the glass before and after the heat shrinkage treatment " is the " length of the glass after heat treatment "

The glass substrate of the present invention preferably has a density of 2.6 g / cm 3 or less, more preferably 2.57 g / cm 3 or less, still more preferably 2.53 g / cm 3 or less in terms of density, light weight of the glass substrate, , And still more preferably not more than 2.5 g / cm 3. If the density is excessively high, it is difficult to reduce the weight of the glass substrate, and the weight of the display can not be reduced.

When the transition point of the glass (hereinafter referred to as Tg) is lowered, the heat resistance tends to decrease. In addition, there is a tendency that heat shrinkage tends to occur in the heat treatment step. The glass substrate of the present invention has a Tg of preferably 720 占 폚 or higher, more preferably 730 占 폚 or higher, even more preferably 740 占 폚 or higher, and still more preferably 750 占 폚 or higher. In order to make the Tg of the glass substrate in the above-described range, the range of composition of the glass substrate of the present invention, to increase the Tg, for example, SiO ₂ and Al ₂ O _3, such as increasing the component or of the, or the components of B ₂ O ₃ .

The glass constituting the glass substrate of the present invention preferably has an etching rate of 50 m / h or more. If the etching rate is increased, the productivity is improved. In particular, in the case where the TFT side and the glass substrate on the color filter side are brought back to each other and etched to reduce the weight, the etching rate affects the productivity. However, if the etching rate is excessively high, the productivity during the production of the liquid crystal is improved, but the resistance to devitrification of the glass is deteriorated. In addition, the heat shrinkage rate is also easily increased. The etching rate is preferably 60 to 140 占 퐉 / h, more preferably 70 to 120 占 퐉 / h, more preferably 75 to 120 占 퐉 / h, and still more preferably 80 to 120 占 퐉 / h. In order to increase the etching rate of the glass is smaller when the value of _{SiO 2 -Al 2 O 3/2} . On the other hand, in order to decrease the etching rate of the glass, for example, when the value of SiO ₂ -Al ₂ O _3/2 significantly. In the present invention, it is defined that the etching rate is measured under the following conditions. The etching rate (占 퐉 / h) of the glass substrate per unit time (1 hour) in the case of immersing the glass substrate in an etching solution of 40 占 폚 for one hour adjusted to have an HF concentration of 1 mol / kg and an HCl concentration of 5 mol / (탆) of the thickness of one surface.

The glass substrate of the present invention may have a thickness in the range of, for example, 0.1 to 1.1 mm. However, the present invention is not limited to this range. The plate thickness may be in the range of, for example, 0.1 to 0.7 mm, 0.3 to 0.7 mm, and 0.3 to 0.5 mm. If the thickness of the glass plate is too thin, the strength of the glass substrate itself is lowered. For example, breakage at the time of manufacturing a flat panel display is likely to occur. If the plate thickness is excessively large, it is not preferable for a display requiring thinness. Further, since the weight of the glass substrate becomes heavy, it is difficult to reduce the weight of the flat panel display. Further, when the etching process is performed after the TFT is formed, the etching process amount becomes large, which leads to cost and time.

The glass substrate of the present invention is used, for example, in the manufacture of a flat panel display in which an array color filter is etched back to a glass substrate surface. Particularly, the glass substrate of the present invention is suitable for a glass substrate for a flat panel display in which an LTPS-TFT or an OS-TFT is formed. Specifically, it is suitable for a glass substrate for a liquid crystal display and a glass substrate for an organic EL display. In particular, it is suitable for glass substrates for LTPS-TFT liquid crystal displays and glass substrates for LTPS-TFT organic EL displays. Among them, it is suitable for a display glass substrate such as a portable terminal requiring high precision.

<Flat Panel Display>

The present invention includes a flat panel display in which an LTPS-TFT or an OS-TFT is formed on the surface of a glass substrate, wherein the glass substrate is the glass substrate of the present invention. The flat panel display of the present invention may be, for example, a liquid crystal display or an organic EL display.

&Lt; Production method of glass substrate >

A manufacturing method of a glass substrate for a flat panel display according to the present invention is a manufacturing method of a glass substrate for a flat panel display comprising a melting step of melting a glass raw material combined with a predetermined composition by using direct energization heating or combustion heating,

A molding step of molding the molten glass melted by the melting step into flat glass,

And a slow cooling step of slowly cooling the flat glass.

In particular, the slow cooling step is preferably a step of controlling the cooling condition of the flat glass to reduce the heat shrinkage rate of the flat glass.

[Melting process]

In the melting step, glass raw materials combined to have a predetermined composition are dissolved by, for example, direct electric heating or combustion heating. The glass raw material can be appropriately selected from known materials. From the viewpoint of energy efficiency, it is preferable to dissolve the glass raw material at least in the dissolving step by using direct energization heating. Further, it is preferable that the melting tank for performing the melting step comprises a high-zirconia-based refractory.

[Molding process]

In the molding step, the molten glass dissolved in the melting step is molded into a flat glass. For example, a down-draw method, in particular, an overflow down-draw method is suitable for forming a glass ribbon into a plate-like glass. In addition, a float method, a lead-down method, a roll-out method, or the like can be applied. Since the main surface of the obtained glass substrate is formed on the free surface other than the atmosphere by using the down-draw method, compared with the case of using other forming methods such as the float method, the glass substrate has extremely high smoothness, The process becomes unnecessary, so that the manufacturing cost can be reduced and the productivity can be further improved. In addition, since both main surfaces of the glass substrate molded by the down-draw method have a uniform composition, etching can be uniformly performed irrespective of the front and back of the glass substrate when the etching process is performed. In addition, by using the down-draw method, it is possible to obtain a glass substrate having a surface state free from micro-cracks due to the polishing process of the surface of the glass substrate, so that the strength of the glass substrate itself can be improved.

[Step of slow cooling]

The heat shrinkage ratio of the glass substrate can be controlled by suitably adjusting the conditions for the slow cooling. In particular, it is preferable to control the cooling conditions of the flat glass to reduce the heat shrinkage rate of the flat glass. The heat shrinkage rate of the glass substrate is 3 ppm or more and less than 75 ppm as described above. For example, in the case of using the down-draw method, the temperature of the glass ribbon as the flat plate glass is changed from 20 to 200 seconds in the temperature range of Tg to 100 deg. C from Tg It is preferable to carry out the molding so as to cool it over. If it is less than 20 seconds, the heat shrinkage may not be sufficiently reduced. On the other hand, if it exceeds 200 seconds, the productivity is lowered and the glass manufacturing apparatus (slow cooling furnace) becomes larger. Alternatively, it is preferable to perform the slow cooling so that the cooling rate of the glass ribbon as the flat plate-shaped glass is set to 30 to 300 ° C / min within the temperature range of Tg to 100 ° C from Tg. If the cooling rate exceeds 300 캜 / min, the heat shrinkage may not be sufficiently reduced. On the other hand, if the heating temperature is less than 30 ° C / minute, the productivity decreases and the glass manufacturing apparatus (annealing furnace) becomes large. The preferred range of the cooling rate is 30 to 300 캜 / min, more preferably 50 to 200 캜 / min, and still more preferably 60 to 120 캜 / min. In addition, the heat shrinkage ratio can be lowered by performing slow cooling separately off-line after cutting the flat glass at the downstream of the slow cooling step. In this case, besides the equipment for performing the slow cooling step, It becomes. Therefore, as described above, it is preferable from the viewpoint of productivity and cost that the slow cooling step is controlled so as to reduce the heat shrinkage rate so that offline slow cooling can be omitted.

[Example]

Hereinafter, the present invention will be described in more detail based on examples. However, the present invention is not limited to the embodiments.

&Lt; Examples 1 to 34 >

Sample glasses of Examples 1 to 34 and Reference Examples 1 to 4 were prepared according to the following procedure so that the glass composition shown in Table 1 was obtained. Tg, average thermal expansion coefficient, heat shrinkage ratio, density and strain point in the range of 100 to 300 占 폚 were determined for the obtained sample glass and the sample glass substrate.

(Preparation of sample glass)

First, in order to obtain the glass composition shown in Table 1, silica, alumina, boron oxide, potassium carbonate, basic magnesium carbonate, calcium carbonate, strontium nitrate, barium nitrate, stannic oxide and ferric oxide (Hereinafter referred to as &quot; batch &quot;) were combined. Further, they were combined in an amount of 400 g as glass.

The combined batches were melted and cleaned in a platinum crucible. First, the crucible was held in an electric furnace set at 1600 캜 for 3 hours to melt the arrangement. Next, the electric furnace was heated to 1640 占 폚 and maintained for 4 hours to refine the free melt. Thereafter, the glass melt was poured onto the steel plate outside the furnace, cooled and solidified to obtain a glass body. This glass body was subjected to a slow cooling operation. In the slow cooling operation, the vitreous body was held in another electric furnace set at 800 DEG C for 2 hours, cooled to 740 DEG C for 2 hours, further cooled to 660 DEG C for 2 hours, turned off the electric furnace, Respectively. The glass body subjected to the slow cooling operation was used as a sample glass. The sample glass was used for the measurement of the characteristics (the devitrification temperature, the thermal expansion coefficient, the Tg and the strain point) which were not influenced by the slow cooling condition and / or could not be measured in the substrate shape.

The sample glass was cut, ground, and polished to form a columnar shape with a diameter of 5 mm and a length of 20 mm. The sample glass was held at Tg for 30 minutes, cooled to Tg-100 DEG C at 100 DEG C / Cooled to obtain a sample glass for heat shrinkage measurement.

(Strain point)

The sample glass was cut and grinded into a prism shape having a length of 3 mm and a length of 55 mm to obtain test pieces. The test piece was measured using a beam bending measuring apparatus (manufactured by Tokyo Kogyo Co., Ltd.), and the strain point was determined by calculation according to the beam bending method (ASTM C-598).

(Heat shrinkage ratio)

The heat shrinkage ratio was calculated from the following equation (1) using the shrinkage of the sample glass for thermal shrinkage measurement after the temperature was raised from room temperature to 10 ° C / min, held at 550 ° C for 2 hours, Respectively.

Heat shrinkage rate (ppm) = (shrinkage of glass before and after heat treatment / length of glass before heat treatment) x 10 ⁶

(Method of measuring the devitrification temperature)

The sample glass was pulverized and passed through a sieve having a size of 2380 mu m to obtain glass particles remaining on a sieve of 1000 mu m. The glass particles were immersed in ethanol, ultrasonically cleaned, and then dried in a thermostatic chamber. The dried glass particles were placed in a platinum boat having a width of 12 mm, a length of 200 mm, and a depth of 10 mm so that 25 g of the glass particles were allowed to have a substantially constant thickness. This platinum boat was held in an electric furnace having a temperature gradient of 1080 to 1400 DEG C for 5 hours and then taken out of a furnace and observed for an occurrence of the inside of the glass with a 50 times optical microscope. The highest temperature at which the release was observed was defined as the release temperature.

(A method of measuring the average thermal expansion coefficient? And Tg in the range of 100 to 300 占 폚)

The sample glass was processed into a cylindrical shape having a diameter of 5 mm and a length of 20 mm to obtain a test piece. The temperature and the elongation of the specimen were measured using a differential thermal expansion meter (Thermo Plus2 TMA8310). At this time, the temperature raising rate was set at 5 DEG C / min. Based on the measurement result of the temperature and the elongation amount of the test piece, the average thermal expansion coefficient and Tg in a temperature range of 100 to 300 캜 were obtained. The Tg in the present application means that the glass body is maintained in another electric furnace set at 800 DEG C for 2 hours, then further cooled to 740 DEG C for 2 hours and further cooled to 660 DEG C for 2 hours, the electric furnace is turned off, It is the value measured for one sample glass.

(density)

The density of the glass was measured by the Archimedes method.

(Etching rate)

The etching rate (占 퐉 / h) was obtained by immersing sample glass (12.5 mm 占 20 mm 占 0.7 mm) for 1 hour in an etching solution (200 ml) at 40 占 폚 adjusted to have an HF concentration of 1 mol / kg and an HCl concentration of 5 mol / kg (탆) of one surface of the glass substrate per unit time (1 hour).

The glass raw materials combined so as to have the compositions shown in the examples were melted at 1560 to 1640 占 폚 using a melting furnace of refractory bricks containing a high zirconia refractory and a continuous melting furnace equipped with a platinum alloy regulating tank to obtain 1620 To 1670 占 폚 and stirred at 1440 to 1530 占 폚 and then molded into a thin plate having a thickness of 0.7 mm by an overflow down-draw method at a rate of 100 占 폚 / min in a temperature range of Tg to 100 占 폚 Followed by slow cooling to obtain a glass substrate. The properties of the substrate were measured using the obtained glass substrate. The heat shrinkage percentage was determined by the following method.

After linear marking was written on a predetermined position of the glass substrate, the glass substrate was cut perpendicularly to the marking, and divided into two glass plate pieces. Next, only one glass plate piece was subjected to a heat treatment at 550 DEG C for 2 hours. Thereafter, the glass plate pieces subjected to the heat treatment and the untreated glass plate pieces were arranged and fixed with an adhesive tape, and the deviation of the markings was measured, and the heat shrinkage percentage was calculated by the following formula.

Heat shrinkage rate (ppm) = (shrinkage of glass before and after heat treatment / length of glass before heat treatment) x 10 ⁶

The glass obtained as described above had a heat shrinkage rate of 3 ppm or more and less than 75 ppm. The devitrification temperature was also lower than 1280 占 폚. Therefore, by using these glasses, it is possible to manufacture a glass substrate which can be used for a display to which an LTPS-TFT is applied by an overflow down-draw method. These glass substrates are suitable as OS-TFT glass substrates.

Claims (19)

In mol%
55 to 80% of SiO ₂ ,
Al ₂ O ₃ : 8 to 20%
B ₂ O ₃ : 0 to 8%,
MgO: more than 0% to 15%
CaO: 0 to 20%
SrO: 0 to 15%
BaO: more than 0% and less than 10%
&Lt; / RTI &gt;
The total amount of SnO ₂ and Fe ₂ O ₃ is in the range of 0.05 to 0.2%
As ₂ O ₃ and Sb ₂ O ₃ ,
SiO ₂ + 2 x Al ₂ O ₃ is 100% or less,
The molar ratio B ₂ O ₃ / (SiO ₂ + Al ₂ O ₃ ) is 0 to 0.12,
The molar ratio MgO / RO (wherein RO is the sum of MgO, CaO, SrO and BaO) is in the range of 0.15 to 0.9,
The strain point is not lower than 706 캜,
A glass transition temperature of 740 캜 or higher,
The devitrification temperature is not lower than 1169 DEG C but not higher than 1235 DEG C,
A glass substrate for display having a heat shrinkage rate of not less than 3 ppm and not more than 75 ppm as expressed by the following formula after heating from room temperature to 10 ° C / minute, holding at 550 ° C for 2 hours, and then lowering the temperature to room temperature at 10 ° C / minute.
Heat shrinkage rate (ppm) = (shrinkage of glass before and after heat treatment / length of glass before heat treatment) x 10 ⁶ The method according to claim 1,
In mol%
63 to 72% of SiO ₂ ,
Al ₂ O ₃ : 11 to 15%
&Lt; / RTI &gt; 3. The method according to claim 1 or 2,
SiO ₂ -Al ₂ O ₃ / of the glass substrate 2 in the range of 45 to 64%. 3. The method according to claim 1 or 2,
In mol%
63 to 70% of SiO ₂ ,
Al ₂ O ₃ : 12 to 15%
B ₂ O ₃ : 1.5 to 7%,
MgO: 3 to 11%
CaO: 5 to 11%
SrO: 0 to 4%
BaO: more than 0% and less than 4%
&Lt; / RTI &gt; 3. The method according to claim 1 or 2,
In mol%
SnO _2: 0.03 to 0.15% of the glass substrate. 3. The method according to claim 1 or 2,
In mol%
Li ₂ O, Na ₂ O and K ₂ O is 0.01 to 0.5%. 3. The method according to claim 1 or 2,
And an average coefficient of thermal expansion at 100 to 300 占 폚 of 28 占^10-7占 폚 ^-1 or more and less than 50 占^10-7占 폚 ^-1 . 3. The method according to claim 1 or 2,
A glass substrate containing 1.0% or more of BaO. 3. The method according to claim 1 or 2,
A glass substrate which is a glass substrate for a liquid crystal display. 3. The method according to claim 1 or 2,
A glass substrate which is a glass substrate molded by an overflow down-draw method. 3. The method according to claim 1 or 2,
In mol%
The total amount of Li ₂ O, Na ₂ O and K ₂ O is 0.01 to 0.3%. 3. The method according to claim 1 or 2,
A glass substrate having a strain point of at least 722 占 폚. A display in which a thin film transistor formed of LTPS or an oxide semiconductor is formed on a surface of a glass substrate, wherein the glass substrate is the glass substrate of claim 1 or 2. Wherein the display is a liquid crystal display or an organic EL display, and the glass substrate of the display is the glass substrate of claim 1 or 2. A melting step of melting a glass raw material combined in a predetermined composition,
A molding step of molding the molten glass dissolved in the melting step into a flat glass,
Wherein the step of slow cooling the flat plate glass comprises a slow cooling step of controlling the cooling condition of the flat plate glass so that a heat shrinkage rate of the flat plate glass is less than 3 ppm and less than 75 ppm, Wherein the glass substrate is a glass substrate. 16. The method of claim 15,
Wherein the dissolving step comprises dissolving the glass raw material using direct energization heating. 16. The method of claim 15,
Wherein the melting step includes dissolving the glass raw material in a melting tank, and a part or all of the refractory constituting the melting tank is a refractory material comprising zirconia. In mol%
55 to 80% of SiO ₂ ,
Al ₂ O ₃ : 8 to 20%
B ₂ O ₃ : 0 to 5%,
MgO: more than 0% to 15%
CaO: 0 to 20%
SrO: 0 to 15%
BaO: more than 0% and less than 2%
&Lt; / RTI &gt;
The total amount of SnO ₂ and Fe ₂ O ₃ is in the range of 0.05 to 0.2%
As ₂ O ₃ and Sb ₂ O ₃ ,
SiO ₂ + 2 x Al ₂ O ₃ is 100% or less,
The molar ratio B ₂ O ₃ / (SiO ₂ + Al ₂ O ₃ ) is 0 to 0.12,
The molar ratio MgO / RO (wherein RO is the sum of MgO, CaO, SrO and BaO) is in the range of 0.15 to 0.9,
The strain point is not lower than 706 캜,
A glass transition temperature of 740 캜 or higher,
The slagging temperature is not lower than 1169 DEG C and not higher than 1235 DEG C,
Wherein the glass substrate for display has a heat shrinkage rate of less than 60 ppm as shown by the following formula after the temperature is raised from room temperature to 10 占 폚 / min, held at 550 占 폚 for 2 hours, and then lowered to room temperature at 10 占 폚 /
Heat shrinkage rate (ppm) = (shrinkage of glass before and after heat treatment / length of glass before heat treatment) x 10 ⁶ delete