JP5914453B2 - Glass substrate for display and manufacturing method thereof - Google Patents

Description

  The present invention relates to a glass substrate for display and a method for producing the same. In particular, the present invention relates to a glass substrate for a low-temperature polysilicon thin film transistor (hereinafter referred to as LTPS-TFT (Low-Temperature-Polycrystalline-Silicon Thin-Film-Transistor)) display. The present invention also relates to a glass substrate for an oxide semiconductor thin film transistor (hereinafter referred to as OS-TFT (Oxide-Semiconductor Thin-Film-Transistor)) display. More specifically, the present invention relates to a glass substrate for display, wherein the display is a liquid crystal display. Or the said display is related with the glass substrate for a display which is an organic electroluminescent display. Furthermore, the present invention relates to a glass substrate for flat panel display, wherein the display is a flat panel display.

  It is desirable to apply LTPS to the manufacture of thin film transistors (TFTs) for reasons such as reducing power consumption for displays mounted on portable devices, etc., but in the manufacture of LTPS-TFTs, a relatively high temperature of 400 to 600 ° C. Heat treatment at a high temperature is necessary. On the other hand, in recent years, higher definition has been required for displays of small portable devices. Therefore, there is a problem of thermal shrinkage of the glass substrate that occurs during display panel manufacturing, which causes pixel pitch shift. In addition, in the glass substrate on which the OS-TFT is formed, suppression of thermal shrinkage is also a problem.

In general, the thermal shrinkage of the glass substrate can be reduced by increasing the strain point of the glass, increasing the glass transition point (hereinafter referred to as Tg), or decreasing the slow cooling rate.
From such a background, a technique for increasing the strain point of glass in order to reduce the thermal shrinkage rate is disclosed (Patent Document 1). Further, a technique for reducing thermal shrinkage by adjusting the ratio of the gradient of the average density curve and the average linear expansion coefficient in the temperature region from the annealing point to the vicinity of the strain point is disclosed (Patent Document 2). In addition, a technique for increasing Tg in order to reduce the thermal shrinkage rate is disclosed (Patent Document 3). Furthermore, since the display panel is required to have higher definition in recent years, the technique of Patent Document 3 has been insufficient in reducing the thermal shrinkage rate. For this reason, a technique for setting the strain point of glass to 725 ° C. or higher is also disclosed (Patent Document 4).

JP 2010-6649 JP 2004-315354 A JP 2011-126728 A JP 2012-106919 A

In recent years, since higher definition is demanded more and more, it is required to further reduce the heat shrinkage rate. When the strain point of the glass substrate is increased in order to further reduce the heat shrinkage rate, it is necessary to increase the content of SiO ₂ and Al ₂ O _{3 in} the glass. As a result, the specific resistance of the molten glass increases. Tend to. In recent years, direct current heating is sometimes used to efficiently melt glass in a melting tank. When direct current heating is used, if the specific resistance of the molten glass increases, current may flow not to the molten glass but to the refractory that constitutes the melting tank, and as a result, the melting tank may be melted. It became clear that there was. However, in the invention described in Patent Document 1, no consideration is given to the specific resistance of the molten glass. Therefore, when it is going to manufacture the glass of patent document 1 through fusing by direct current heating, we are anxious about the problem of the said melting tank melting occurring. Further, in recent years, higher resolution has been demanded, and the strain point of the glass has been further demanded, so that the above problem becomes more prominent.
Moreover, since the strain point of the glass disclosed in Patent Document 2 is 682 to 699 ° C., it is necessary to make the slow cooling rate extremely slow in order to make the gradient of the average density curve sufficiently small in heat shrinkage. There was a problem that productivity was lowered. Furthermore, since the glass disclosed in Patent Document 2 has a devitrification temperature of 1287 ° C. or higher, devitrification is likely to occur. Further, the above-described problem becomes particularly remarkable when molding is performed using the downdraw method.
Furthermore, in manufacturing a display using a glass substrate, it is required to improve productivity. For example, improvement in productivity in a process of thinning a glass substrate on which a thin film transistor is formed is also required. The productivity of the process of thinning the glass substrate greatly depends on the time required for etching the glass substrate. Therefore, the display glass substrate is required to achieve both improvement in productivity due to increase in etching rate and reduction in heat shrinkage rate. However, the glass substrate described in Patent Document 4 has a problem that the etching rate is not considered although the strain point is high.

  In this way, when trying to reduce the thermal shrinkage rate of the glass substrate, there is a problem of melting bath melting due to an increase in the specific resistance of the glass, a problem of devitrification of the glass, or an improvement in productivity and heat due to an increase in the etching rate. There arises a problem of difficulty in achieving compatibility with a reduction in shrinkage rate.

Therefore, this embodiment is
(1) A glass substrate that achieves both a high strain point and prevention of melting bath melting by direct current heating during melting of the glass,
Or
(2) a glass substrate that achieves both a high strain point and suppression of devitrification in the molding process;
Or
(3) a glass substrate having both a high strain point and a high etching rate;
And it aims at providing this manufacturing method. In particular, an object of the present embodiment is to provide a glass substrate for display suitable for a display using LTPS-TFT or OS-TFT and a manufacturing method thereof.

  This embodiment has the following aspects.

[1]
Containing SiO ₂ , Al ₂ O ₃ ,
In mol%
B ₂ O ₃ 0-8%,
R ₂ O 0.01-0.8%,
The value calculated from the content of the component in the formula represented by BaO / RO is 0.05 to 1,
A glass substrate for display formed from glass having a strain point of 670 ° C. or higher.
Here, RO represents (MgO + CaO + SrO + BaO), and R ₂ O represents (Li ₂ O + Na ₂ O + K ₂ O).
In one embodiment, the composition of MgO is 1.4-15%.

[2]
The contents of SiO ₂ , Al ₂ O ₃ and BaO are expressed in mol%,
SiO ₂ 60~80%,
Al ₂ O ₃ 8-20%,
The glass substrate according to [1], which is BaO 0.1 to 15%.

[3]
Value calculated from the content of the component in the formula, expressed as (SiO ₂ + (2 × Al ₂ O ₃ )) / ((2 × B ₂ O ₃ ) + RO + (10 × R ₂ O)) The glass substrate according to [1] or [2], wherein is 2.5 or more.

[Four]
In mol%
SiO ₂ 60~80%,
Al ₂ O ₃ 8-20%,
B ₂ O ₃ 0-8%,
R ₂ O 0.01 to 0.8%, and is represented by the formula (SiO ₂ + (2 × Al ₂ O ₃ )) / ((2 × B ₂ O ₃ ) + RO + (10 × R ₂ O)) The value calculated from the content of the components in is 2.5 or more,
BaO / RO is 0.05-1
A glass substrate for display formed from glass having a strain point of 670 ° C. or higher.
Here, RO represents (MgO + CaO + SrO + BaO), and R ₂ O represents (Li ₂ O + Na ₂ O + K ₂ O).
The composition of MgO is 1.4 to 15% in one embodiment.

[Five]
In mol%
MgO 0-15%,
CaO 0-20%,
SrO 0-15%,
The glass substrate according to any one of [1] to [4], containing BaO 0.1 to 15%.

[6]
The glass substrate according to any one of [1] to [5], wherein a value represented by a molar ratio SiO ₂ / Al ₂ O ₃ is less than 10.

[7]
The value calculated from the content of the component in the formula represented by B ₂ O ₃ + RO + ZnO in mol% is 15 to 25%, according to any one of [1] to [6] Glass substrate.

[8]
Further containing SnO ₂ and Fe ₂ O ₃ ,
In mol%
SnO ₂ content is 0.03-0.15%,
The glass substrate according to any one of [1] to [7], wherein the total content of SnO ₂ and Fe ₂ O ₃ is 0.05 to 0.2%.

[9]
In mol%
SiO ₂ 66-72%,
Al ₂ O ₃ 11-15%,
B ₂ O ₃ 0-8%,
MgO 0-6%,
CaO 2-11%,
SrO 0-1%,
The glass substrate according to any one of [1] to [8], containing 1 to 10% of BaO.

[Ten]
In mol%
SiO ₂ 66-72%,
Al ₂ O ₃ 11-15%,
B ₂ O ₃ 0-8%,
MgO 0-6%,
CaO 2-11%,
SrO 0-1%,
BaO 1-10%,
Any of [1] to [9], wherein the value of BaO / RO is 0.1 to 0.5, the value of CaO / RO is 0.2 to 0.6, and the value of MgO / (RO + ZnO) is 0.15 to 0.6 A glass substrate as described in 1.

[11]
The glass substrate according to any one of [1] to [10], which does not substantially contain La ₂ O ₃ and Y ₂ O ₃ .

[12]
Containing SiO ₂ , Al ₂ O ₃ , MgO,
In mol%
MgO / (RO + ZnO) is 0.1-0.9,
Made of glass with a strain point of 700 ° C or higher, heated at a heating rate of 10 ° C / min, held at 550 ° C for 2 hours, cooled to 400 ° C over 55 minutes, and then allowed to cool to room temperature The glass substrate for a display whose thermal contraction rate shown by the following formula of a case is 5 ppm-75 ppm.
Thermal shrinkage rate (ppm) = {Shrinkage amount of glass before and after heat treatment / Glass length before heat treatment} × 10 ⁶ where RO represents (MgO + CaO + SrO + BaO).

[13]
Containing SiO ₂ , Al ₂ O ₃ , BaO,
In mol%
BaO 1-15%,
Sb ₂ O ₃ is not substantially contained, and is made of glass with a strain point of 700 ° C. or higher, heated at a rate of 10 ° C./min at a rate of temperature rise, held at 550 ° C. for 2 hours, and over 400 minutes over 400 minutes A glass substrate for display having a thermal shrinkage ratio of 5 ppm to 75 ppm represented by the following formula when the temperature is lowered to ° C. and then allowed to cool to room temperature.

[14]
The content of SiO ₂ and Al ₂ O ₃ is expressed in mol%,
SiO ₂ 60~80%,
The glass substrate according to [12] or [13], which is Al ₂ O _{3 8 to} 20%.

[15]
The glass substrate according to any one of [12] to [14], which is MgO 1 to 15% in terms of mol%.

[16]
In mol%
SiO ₂ 60~80%,
Al ₂ O ₃ 8-20%,
B ₂ O ₃ 0-15%,
BaO 1-15%,
MgO / (RO + ZnO) is 0.1-0.9,
Made of glass with a strain point of 700 ° C or higher, heated at a rate of 10 ° C / min at a rate of temperature rise, held at 550 ° C for 2 hours, cooled to 400 ° C over 55 minutes, and then allowed to cool to room temperature The glass substrate for a display whose thermal contraction rate shown by the following formula is 5 ppm-75 ppm.
Thermal shrinkage (ppm) = {Shrinkage amount of glass before and after heat treatment / Glass length before heat treatment} × 10 ⁶
Here, RO represents (MgO + CaO + SrO + BaO).

[17]
In any one of [12] to [16], (SiO ₂ + (2 × Al ₂ O ₃ )) / ((2 × B ₂ O ₃ ) + RO) is 2.8 to 20 in terms of mol%. Glass substrate.

[18]
In mol%
MgO 1-15%,
CaO 0-20%,
The glass substrate according to any one of [12] to [17], containing 0 to 15% of SrO.

[19]
The glass substrate according to any one of [12] to [18], wherein the SiO ₂ / Al ₂ O ₃ is 6.0 or less in terms of mol%.

[20]
Containing SnO ₂ and Fe ₂ O ₃ ,
In mol%
SnO ₂ 0.03-0.15%,
The glass substrate according to any one of [12] to [19], wherein the total amount of SnO ₂ and Fe ₂ O ₃ is 0.05 to 0.2%.

[twenty one]
In mol%
SiO ₂ 66-72%,
Al ₂ O ₃ 11-15%,
B ₂ O ₃ 0-7%,
MgO 1-6%,
CaO 2-11%,
The glass substrate according to any one of [12] to [20], which contains SrO 0 to 1% and BaO 1 to 10%.

[22] In mol%,
SiO ₂ 66-72%,
Al ₂ O ₃ 11-15%,
B ₂ O ₃ 0-7%,
MgO 1-6%,
CaO 2-11%,
SrO 0-1%,
BaO 1-10%,
Any of [12] to [21], wherein the value of BaO / RO is 0.1 to 0.5, the value of Ca / RO is 0.2 to 0.6, and the value of MgO / (RO + ZnO) is 0.15 to 0.6 A glass substrate as described in 1.

[twenty three]
Containing SiO ₂ , Al ₂ O ₃ , BaO,
In mol%
B ₂ O ₃ 0-7%,
BaO 1-15%,
SiO ₂ / Al ₂ O ₃ is 6.0 or less,
A glass substrate for display formed from glass having a strain point of 700 ° C. or higher.

[twenty four]
The content of SiO ₂ and Al ₂ O ₃ is expressed in mol%,
SiO ₂ 60~80%,
The glass substrate according to [23], which is Al ₂ O ₃ 10.5 to 20%.

[twenty five]
In mol%
SiO ₂ 60~80%,
Al ₂ O ₃ 10.5-20%,
B ₂ O ₃ 0-7%,
BaO 1-15%,
Substantially free of As ₂ O ₃
RO is 10.0-18.0%,
SiO ₂ / Al ₂ O ₃ is 3 or more and 5.7 or less,
SrO <0.25 × CaO,
A glass substrate for display formed from glass having a strain point of 700 ° C. or higher.
Here, RO represents (MgO + CaO + SrO + BaO).

[26]
In mol%
MgO 0-15%,
CaO 0-20%,
The glass substrate according to any one of [23] to [25], containing SrO 0 to 8%.

[27]
The glass substrate according to any one of [23] to [26], wherein SrO / RO is 0 to 0.1 in terms of mol%.

[28]
The glass substrate according to any one of [23] to [27], wherein the CaO / RO is 0.1 to 0.8 in terms of mol%.

[29]
Containing SnO ₂ and Fe ₂ O ₃ ,
In mol%
SnO ₂ 0.03-0.15%,
The glass substrate according to any one of [23] to [28], wherein the total amount of SnO ₂ and Fe ₂ O ₃ is in the range of 0.05 to 0.2%.

[30]
In mol%
SiO ₂ 66-72%,
Al ₂ O ₃ 11-15%,
B ₂ O ₃ 0-7%,
MgO 0-6%,
CaO 2-11%,
SrO 0-1%,
The glass substrate according to any one of [23] to [29], containing 1 to 10% of BaO.

[31]
In mol%
SiO ₂ 66-72%,
Al ₂ O ₃ 11-15%,
B ₂ O ₃ 0-7%,
MgO 0-6%,
CaO 2-11%,
SrO 0-1%,
BaO 1-10%,
Any of [23] to [30], wherein the value of BaO / RO is 0.1 to 0.5, the value of Ca / RO is 0.2 to 0.6, and the value of MgO / (RO + ZnO) is 0.15 to 0.6 A glass substrate as described in 1.

[32]
The glass substrate according to any one of [23] to [31], wherein an average coefficient of thermal expansion at 100 to 300 ° C is 28.0 to 45.0 × 10 ^-7 ° C ^-1 .

[33]
The values represented by (SiO ₂ + (2 × Al ₂ O ₃ )) / ((2 × B ₂ O ₃ ) + RO) are 3.1 or more, [1] to [11] and [23] to [ 32]. The glass substrate according to any one of [32].

[34]
The value calculated from the content of the component in the formula represented by SiO _2- (1/2 × Al ₂ O ₃ ) in mol% is less than 65%, from [1] to [33] The glass substrate in any one.

[35]
The glass substrate according to any one of [1] to [34], which does not substantially contain As ₂ O ₃ .

[36]
The glass substrate according to any one of [1] to [35], which does not substantially contain Sb ₂ O ₃ .

[37]
The glass substrate according to any one of [1] to [22], in which R ₂ O (Li ₂ O + Na ₂ O + K ₂ O) is 0.1 to 0.4% in terms of mol%.

[38]
The glass substrate according to any one of [1] to [22], wherein an average coefficient of thermal expansion at 100 to 300 ° C is 28.0 to 50.0 × 10 ^-7 ° C ^-1 .

[39]
The glass substrate according to any one of [1] to [38], which is a glass substrate formed by an overflow downdraw method.

[40]
The glass substrate according to any one of [1] to [39], which is a glass substrate for a flat panel display in which a thin film transistor formed using low-temperature polysilicon or an oxide semiconductor is formed on the surface of the glass substrate.

[41]
The glass substrate according to [1] to [40], which is a glass substrate for a liquid crystal display or an organic EL display.

[42]
The glass substrate according to [1] to [41], wherein the glass substrate is a glass substrate for display excluding a CRT (CRT) display.

[43]
A melting step of melting a glass raw material prepared to a predetermined composition using at least direct current heating;
A forming step of forming the molten glass melted in the melting step into a flat glass;
A step of slowly cooling the flat glass, and a slow cooling step of controlling cooling conditions of the flat glass so as to reduce a thermal shrinkage rate of the flat glass [1] to [42] The manufacturing method of the glass substrate for displays in any one of.

[44]
The melting method is the production method according to [43], wherein the glass raw material is melted in a melting tank configured to contain at least a high zirconia refractory.

[45]
The slow cooling step performs slow cooling so that the cooling rate of the flat glass is 30 to 300 ° C./min within the temperature range where the flat glass is changed from Tg to (Tg-100 ° C.) [43] Or the manufacturing method as described in [44].

[46]
A display using the glass substrate for display according to any one of [1] to [45].

According to one aspect of the glass substrate described above, high strain point glass can be produced while suppressing or avoiding melting of the glass melting tank.
Moreover, according to the one aspect | mode of the above-mentioned glass substrate, it becomes possible to manufacture the glass which is a high strain point and can suppress devitrification at the time of shaping | molding.
Furthermore, according to one aspect of the glass substrate described above, it is possible to produce a glass substrate that has both a high strain point and a high etching rate.
Thereby, the glass substrate for a display which can reduce the heat shrink at the time of display manufacture, especially the glass substrate for a display suitable for the flat panel display using LTPS-TFT or OS-TFT can be provided.

  In the specification of the present application, unless otherwise specified, the glass composition is expressed as mol% (mol%), and the content expressed as% means mol%. The ratio of the component which comprises a glass composition is displayed by molar ratio.

One form of the glass substrate for display of this embodiment is compatible with both a high strain point and prevention of melting bath melting due to direct current heating during melting of the glass. The glass substrate contains SiO ₂ , Al ₂ O ₃ ,
In mol%
B ₂ O ₃ is 0-8%,
R ₂ O is 0.01-0.8%,
BaO / RO is 0.05-1
The strain point is 670 ° C or higher.
In the present specification, RO represents (MgO + CaO + SrO + BaO), and R ₂ O represents (Li ₂ O + Na ₂ O + K ₂ O).

The contents of SiO ₂ , Al ₂ O ₃ and BaO are expressed in mol%,
SiO ₂ 60~80%,
Al ₂ O ₃ 8-20%,
BaO is preferably 0.1 to 15%.

More preferably, the glass substrate for display of the present invention is expressed in mol%,
SiO ₂ 60~80%,
Al ₂ O ₃ 8-20%,
B ₂ O ₃ 0-8%,
R ₂ O is 0.01-0.8%,
(SiO ₂ + (2 × Al ₂ O ₃ )) / ((2 × B ₂ O ₃ ) + RO + (10 × R ₂ O)) is 2.5 or more,
BaO / RO is 0.05-1
The strain point is 670 ° C or higher.
The said glass substrate is demonstrated in the Example mentioned later as a glass substrate (A).

Another embodiment of the glass substrate for display of the present embodiment achieves both a high strain point and suppression of devitrification in the molding process. The glass substrate is
Containing SiO ₂ , Al ₂ O ₃ , MgO,
In mol%
MgO / (RO + ZnO) is 0.1-0.9,
Made of glass with a strain point of 700 ° C or higher, heated at a rate of 10 ° C / min at a rate of temperature rise, held at 550 ° C for 2 hours, cooled to 400 ° C over 55 minutes, and then allowed to cool to room temperature In the case, the thermal shrinkage rate represented by the following formula is 5 ppm to 75 ppm.
Here, RO represents (MgO + CaO + SrO + BaO). In this embodiment, MgO / (RO + ZnO) is set to 0.1 to 0.9, so that devitrification during molding can be suppressed while maintaining a high strain point. Moreover, the meltability of glass can also be maintained by making MgO / (RO + ZnO) 0.1-0.9. Furthermore, since the thermal shrinkage rate is 5 ppm to 75 ppm, it is suitable as a display glass substrate suitable for a display using LTPS-TFT and a display glass substrate using OS-TFT.

Also contains SiO ₂ , Al ₂ O ₃ , BaO,
In mol%
BaO 1-15%,
Made of glass that does not contain Sb ₂ O ₃ substantially and has a strain point of 700 ° C. or higher, heated at a rate of 10 ° C./min at a rate of temperature rise, held at 550 ° C. for 2 hours, and taken 400 over 55 minutes. When the temperature is lowered to ° C. and then allowed to cool to room temperature, the thermal shrinkage rate represented by the following formula is 5 ppm to 75 ppm.

In this form, since the BaO content is 1 to 15%, the devitrification temperature of the glass can be effectively lowered while maintaining a high strain point. Since the thermal shrinkage rate is 5 ppm to 75 ppm, it is suitable as a display glass substrate suitable for a display using LTPS-TFT and a display glass substrate using OS-TFT.
The content of SiO ₂ and Al ₂ O ₃ is expressed in mol%,
SiO ₂ 60~80%,
Al ₂ O ₃ is preferably 8 to 20%.

More preferably, one form of the glass substrate for display of the present embodiment is expressed in mol%,
SiO ₂ 60~80%,
Al ₂ O ₃ 8-20%,
B ₂ O ₃ 0-15%,
BaO 1-15%,
MgO / (RO + ZnO) is 0.1-0.9,
Made of glass with a strain point of 700 ° C or higher, heated at a rate of 10 ° C / min at a heating rate, held at 550 ° C for 2 hours, cooled to 400 ° C over 55 minutes, and then allowed to cool to room temperature The thermal shrinkage rate represented by the following formula is 5 ppm to 75 ppm.
Thermal shrinkage (ppm) = {Shrinkage amount of glass before and after heat treatment / Glass length before heat treatment} × 10 ⁶
In this embodiment, MgO / (RO + ZnO) is 0.1 to 0.9 and the BaO content is 1 to 15%, so that the strain point of the glass can be increased while maintaining a low devitrification temperature. Furthermore, since the thermal shrinkage rate is 5 ppm to 75 ppm, it is suitable as a display glass substrate suitable for a display using LTPS-TFT and a display glass substrate using OS-TFT. The said glass substrate is demonstrated in the Example mentioned later as a glass substrate (B).

Still another embodiment of the glass substrate for display of the present embodiment achieves both a high strain point and a high etching rate. The glass substrate contains SiO ₂ , Al ₂ O ₃ , BaO,
In mol%
B ₂ O ₃ 0-7%,
BaO 1-15%,
SiO ₂ / Al ₂ O ₃ is 6.0 or less,
The strain point is 700 ° C or higher.
By setting the B ₂ O ₃ content to 0 to 7%, the high temperature viscosity of the glass can be lowered and the meltability can be improved.
By setting the content of BaO to 1 to 15%, the devitrification temperature can be effectively lowered while keeping the strain point of the glass high.
By setting SiO ₂ / Al ₂ O ₃ to 6.0 or less, the etching rate can be improved.
Moreover, the thermal shrinkage rate can be controlled within a predetermined range by setting the strain point of the glass to 700 ° C. or higher.
The content of SiO ₂ and Al ₂ O ₃ is expressed in mol%,
SiO ₂ 60~80%,
Al ₂ O ₃ is preferably 10.5 to 20%.
By setting SiO ₂ to 60 to 80%, it is possible to reduce the density while suppressing an increase in the thermal expansion coefficient of the glass. Further, by setting Al ₂ O ₃ to 10.5 to 20%, it is possible to suppress an increase in devitrification temperature while suppressing a decrease in strain point.

More preferably, in terms of mol%,
SiO ₂ 60~80%,
Al ₂ O ₃ 10.5-20%,
B ₂ O ₃ 0-7%,
BaO 1-15%,
Substantially free of As ₂ O ₃
RO is 10.0-18.0%,
SiO ₂ / Al ₂ O ₃ is 3 or more and 5.7 or less,
SrO <0.25 × CaO,
The strain point is 700 ° C or higher.
Here, RO represents (MgO + CaO + SrO + BaO).
By setting the RO to 10.0 to 18.0%, the density can be reduced while maintaining the meltability, and the increase in the thermal expansion coefficient can be suppressed.
By setting SiO ₂ / Al ₂ O ₃ to 3 or more and 5.7 or less, it is possible to achieve both a high strain point, devitrification resistance, and an etching rate.
By setting SrO <0.25 × CaO, the devitrification temperature of the glass can be effectively reduced.
Moreover, the thermal shrinkage rate can be controlled within a predetermined range by setting the strain point of the glass to 700 ° C. or higher.
The said glass substrate is demonstrated in the Example mentioned later as a glass substrate (C).

  Hereinafter, embodiments of the glass substrate for display of this embodiment will be described.

SiO ₂ is a skeletal component of glass and is therefore an essential component. When the content decreases, the strain point tends to decrease and the thermal expansion coefficient tends to increase. If the SiO ₂ content is too small, it is difficult to reduce the density of the glass substrate. On the other hand, if the SiO ₂ content is too large, the specific resistance of the molten glass increases, the melting temperature tends to be extremely high, and melting tends to be difficult. When SiO ₂ content is too large, the devitrification temperature rises, the devitrification resistance also tends to decrease. Furthermore, if the SiO ₂ content is too high, the etching rate becomes slow. From such a viewpoint, the content of SiO ₂ is preferably in the range of 60 to 80 mol%. The content of SiO ₂ is more preferably in the range of 64-73 mol% or 65-75 mol%, still more preferably 66-72 mol%, and still more preferably 67-71 mol%.

Al ₂ O ₃ is an essential component that increases the strain point. If the Al ₂ O ₃ content is too small, the strain point is lowered. Furthermore, if the Al ₂ O ₃ content is too small, the Young's modulus and acid etching rate tend to decrease. On the other hand, if the Al ₂ O ₃ content is too high, the devitrification temperature of the glass rises and the devitrification resistance decreases, so that the formability tends to deteriorate. From such a 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 in the range of 10 to 17 mol%, more preferably 10.5 to 17 mol%, more preferably 11 to 15 mol%, and further preferably 12 to 15 mol%.

B ₂ O ₃ is a component that lowers the high temperature viscosity of the glass and improves the meltability. That is, since the viscosity in the vicinity of the melting temperature is lowered, the meltability is improved. It is also a component that lowers the devitrification temperature. The content of B ₂ O ₃ is small, meltability and devitrification resistance tends to be lowered. When the content of B ₂ O ₃ is too large, the strain point and the Young's modulus is reduced. Further, devitrification is likely to occur due to volatilization of B ₂ O ₃ during glass forming. In particular, a glass having a high strain point tends to have a high molding temperature. Therefore, the volatilization is promoted, and the generation of devitrification becomes a significant problem. Further, due to the volatilization of B ₂ O ₃ during melting of the glass, non-uniformity of the glass becomes prominent and striae easily occur. From such a viewpoint, the content of B ₂ O ₃ is 0 to 15 mol%, preferably 0 to 8 mol%, more preferably 0 to 7 mol%, still more preferably 0.1 to 6 mol%, and still more preferably. Is in the range of 1-5 mol%, more preferably 1.5-4.5 mol%.

MgO is a component that improves meltability. Moreover, since it is a component which is hard to increase a density in alkaline-earth metal, when the content is increased relatively, it will become easy to achieve a low density. By containing, the specific resistance and melting temperature of the molten glass can be reduced. However, if the content of MgO is too large, the devitrification temperature of the glass rises abruptly, so that it tends to devitrify particularly in the molding process. From such a viewpoint, the MgO content is 0 to 15 mol%, preferably 1 to 15 mol%, more preferably 0 to 6 mol%, and further preferably 1 to 6 mol%. Alternatively, the MgO content is preferably 0 to 15 mol%, more preferably 0 to 6 mol%, and still more preferably 1 to 6 mol%.

  CaO is an effective component for improving the meltability of the glass without rapidly increasing the devitrification temperature of the glass. Moreover, since it is a component which is hard to increase a density in alkaline-earth metal oxide, when the content is increased relatively, it will become easy to aim at a density reduction. When there is too little content, there exists a tendency for the raise of the specific resistance of molten glass, and a devitrification resistance fall to arise. If the CaO content is too large, the coefficient of thermal expansion increases and the density tends to increase. From such a viewpoint, the CaO content is 0 to 20 mol%, preferably 1 to 15 mol%, more preferably 2 to 11 mol%, and further preferably 4 to 9 mol%.

  SrO is a component that can lower the devitrification temperature of glass. Although SrO is not essential, when it is contained, devitrification resistance and meltability are improved. However, if the SrO content is too high, the density will increase. From such a viewpoint, the SrO content is 0 to 15 mol%, preferably 0 to 8 mol%, more preferably 0 to 3 mol%, still more preferably 0 to 1 mol%, still more preferably 0 to 0.5 mol%. %, And even more preferably, it is not substantially contained.

  BaO is an essential component that can effectively lower the devitrification temperature of glass and the specific resistance of molten glass. When BaO is contained, devitrification resistance and meltability are improved. However, when there is too much content of BaO, a density will rise. Further, from the viewpoint of environmental load and the tendency of the thermal expansion coefficient to increase, the BaO content is 0 to 15 mol% or 0.1 to 15 mol%, preferably 1 to 15 mol%, more preferably 1 It is in the range of ˜10 mol%, more preferably 1.5 to 6 mol%.

Li ₂ O and Na ₂ O are components that may increase the thermal expansion coefficient of glass and damage the substrate during heat treatment. It is also a component that lowers the strain point. On the other hand, since the specific resistance of the molten glass can be reduced, it is possible to suppress the erosion of the melting tank by the inclusion. From the above viewpoint, the content of Li ₂ O is preferably 0 to 0.5 mol%, more preferably not substantially contained. The content of Na ₂ O is preferably 0 to 0.5 mol%, more preferably 0 to 0.2 mol%. Incidentally, Na ₂ O, since compared with Li ₂ O is a difficult component to lower the strain point is preferably Na ₂ O> Li ₂ O. Note that it is preferable that Li ₂ O and Na ₂ O are not substantially contained from the viewpoint of preventing elution from the glass substrate and deteriorating the TFT characteristics.

K ₂ O is a component that increases the basicity of the glass and promotes clarity. Moreover, it is a component which reduces the specific resistance of molten glass. When it is contained, the specific resistance of the molten glass is lowered, so that it is possible to prevent a current from flowing through the refractory constituting the melting tank and to suppress the erosion of the melting tank. In addition, when the refractory constituting the melting tank contains zirconia, the melting tank can be prevented from being eroded and the zirconia can be prevented from being eluted from the melting tank to the molten glass, so devitrification caused by zirconia can also be suppressed. . Moreover, since the glass viscosity in the vicinity of the melting temperature is lowered, the meltability and the clarity are improved. On the other hand, when the content of K ₂ O is too large, the thermal expansion coefficient tends to increase and the strain point tends to decrease. From such a 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 strain point of glass. However, when the amount of ZrO _{2 and the} amount of TiO ₂ are too large, the devitrification temperature is remarkably increased, so that the devitrification resistance tends to be lowered. In particular, since ZrO ₂ has a high melting point and is hardly melted, it causes a problem that a part of the raw material is deposited on the bottom of the melting tank. When these unmelted components are mixed into the glass substrate, the quality of the glass is deteriorated as inclusions. Further, TiO ₂ is a component that colors glass, and thus is not preferable for a display substrate. From such a viewpoint, in the glass substrate of the present embodiment, the contents of ZrO ₂ and TiO ₂ are each preferably 0 to 5 mol%, more preferably 0 to 2 mol%, and not substantially contained. More preferably.

  ZnO is a component that improves meltability. However, it is not an essential component. When the ZnO content is too high, the devitrification temperature is increased, the strain point is decreased, and the density tends to increase. From such a viewpoint, the ZnO content is preferably in the range of 0 to 5 mol%, more preferably 0 to 2 mol%, and even more preferably not contained.

P ₂ O ₅ is a component that reduces high temperature viscosity and improves meltability. However, it is not an essential component. P ₂ O ₅ content is too large strain point is lowered. Moreover, due to the volatilization of P ₂ O ₅ during glass melting, non-uniformity of the glass becomes prominent and striae easily occur. From such a viewpoint, the P ₂ O ₅ content is preferably in the range of 0 to 3 mol%, more preferably 0 to 1 mol%, still more preferably 0 to 0.5 mol%, and it is further not substantially contained. preferable.

The glass substrate of this embodiment can contain a fining agent. The fining agent is not particularly limited as long as the load on the environment is small and the fining of the glass is excellent. For example, from the group of metal oxides of Sn, Fe, Ce, Tb, Mo, Sb and W. There may be mentioned at least one selected. As the fining agent, SnO ₂ is suitable. If the content of the fining agent is too small, the foam quality is deteriorated, and if it is too large, devitrification and coloring may be caused. The content of the fining agent depends on the type of 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 0.50 mol%, and more preferably 0.05 to 0.20 mol%.

SnO ₂ is a refining agent that can achieve a refining effect even at 1600 ° C or higher, and glass substrates for flat panel displays that can contain only a small amount of Li ₂ O, Na ₂ O and K ₂ O (for example, Li ₂ O, Na ₂ O And a total amount of K ₂ O of 0.01 to 0.8 mol%). However, SnO ₂ is a component that easily causes devitrification, and is a component that promotes the generation of devitrification of other components. Therefore, it is not preferable to add a large amount from the viewpoint of suppressing devitrification.

Further, a glass having a high strain point (for example, a glass having a strain point of 670 ° C. or higher or a glass having a strain point of 700 ° C. or higher) is a glass having a low strain point (for example, a glass having a strain point lower than 670 ° C. or a glass having a strain point lower than 700 ° C.). In order to suppress devitrification, the temperature of the molten glass in the molding process may have to be higher than that of a glass having a low strain point. . Here, it is preferable that the molded object used by the overflow downdraw method is comprised including the refractory containing a zirconia from a viewpoint of creep resistance and heat resistance. When adopting overflow downdraw as a molding method, it is necessary to increase the temperature of the molded body as the temperature of the molten glass in the molding process is increased. However, when the temperature of the molded body becomes high, there is a problem that zirconia is eluted from the molded body and devitrification of the zirconia tends to occur. Further, particularly in the glasses containing a large amount of SnO _2, there SnO ₂ devitrification caused by the zirconia, the tendency to cause devitrification of zirconia due to SnO _2.

Furthermore, a glass having a high strain point (for example, a glass having a strain point of 670 ° C. or higher or a glass having a strain point of 700 ° C. or higher) is a glass having a low strain point (for example, a glass having a strain point lower than 670 ° C. or a glass having a strain point lower than 700 ° C.). Compared to the above, the temperature at which the glass raw material is melted tends to be high. Here, it is preferable that the melting tank which performs a melting process is comprised including the high zirconia refractory containing a zirconia from a viewpoint of erosion resistance. From the viewpoint of energy efficiency, it is preferable to melt the glass raw material by electric melting or a combination of electric melting and other heating means. However, when melting a glass having a high strain point as described in the present embodiment and containing only a small amount of Li ₂ O, Na ₂ O and K ₂ O, the specific resistance of the molten glass is large, Current flows through the high zirconia refractory, and the problem that zirconia elutes into the molten glass tends to occur. If zirconia is eluted, the above-described zirconia devitrification and SnO ₂ devitrification tend to occur.

That is, from the viewpoint of suppressing devitrification of zirconia and SnO ₂ , it is not preferable that SnO ₂ is contained in an amount exceeding 0.5 mol% in the glass substrate of the present embodiment. From such a viewpoint, the SnO ₂ content is, for example, preferably 0 or more and less than 0.5 mol%, preferably 0.01 to 0.5 mol%, more preferably 0.01 to 0.2 mol%, still more preferably 0.03 to 0.15 mol. %, More preferably in the range of 0.05 to 0.12 mol%.

Fe ₂ O ₃ is a component that lowers the specific resistance of the molten glass in addition to having a function as a fining agent. In high-viscosity and hardly meltable glass, it is preferably contained in order to reduce the specific resistance of the molten glass. However, if the Fe ₂ O ₃ content is too high, the glass is colored and the transmittance is lowered. Therefore, the content of Fe ₂ O ₃ 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%, and still more preferably 0.005 to It is in the range of 0.03 mol%.

In the present embodiment, the fining agent is preferably used in combination of SnO ₂ and Fe ₂ O ₃ . As described above, it is not preferable to contain a large amount of SnO ₂ from the viewpoint of suppressing devitrification. However, in order to obtain a sufficient clarification effect, it is required to contain a clarifier 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 less bubbles and a sufficient clarification effect without increasing the SnO ₂ content to the extent that devitrification occurs. 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 0.07 to 0.2 mol%, still more preferably 0.08 to 0.18 mol%, more preferably 0.09 to 0.15 mol%. Range.

If the molar ratio of SnO ₂ content to the total amount of SnO ₂ and Fe ₂ O ₃ (SnO ₂ / (SnO ₂ + Fe ₂ O ₃ )) is too large, devitrification tends to occur. The clarification effect cannot be obtained, and the glass may be colored. Therefore, it is preferably in the range of 0.6 to 0.95, more preferably in the range of 0.65 to 0.9.

The glass substrate of the present embodiment preferably contains substantially no As ₂ O ₃ because of environmental load problems. In the glass substrate of the present embodiment, Sb ₂ O ₃ is preferably 0 to 0.5 mol% (including 0), more preferably 0 to 0.3 mol%, and still more preferably 0 to 0.05 mol% due to environmental load problems. It is preferable that it is the range of this, and it is still more preferable not to contain substantially.

  The glass substrate of this embodiment preferably contains substantially no PbO and F for environmental reasons.

  In the present specification, “substantially does not contain” means that a material that is a raw material of these components is not used in the glass raw material, and a component contained as an impurity in the glass raw material of another component, It does not exclude the mixing of components that elute from the manufacturing apparatus such as the melting tank and the molded body into the glass.

When SiO ₂ which is the total amount of twice the amount of content and _{Al 2 O 3 SiO 2 + (} 2 × Al 2 O 3) is too small, there is a tendency that the strain point is lowered, while when too large , Devitrification resistance tends to deteriorate. Therefore, SiO ₂ + (2 × Al ₂ O ₃ ) is preferably 100 mol% or less, preferably 75 to 100 mol%, more preferably 80 to 100 mol%, and still more preferably 92 to 98 mol%.

The difference between the half in content and Al ₂ O ₃ of _{SiO 2 SiO 2 - (1/} 2 × Al 2 O 3) , when the value is too large, there is a possibility that the etching rate decreases. From such a viewpoint, SiO ₂ − (1/2 × Al ₂ O ₃ ) is preferably 69 mol% or less, more preferably less than 65 mol%. On the other hand, if SiO _2- (1/2 × Al ₂ O ₃ ) is too small, devitrification resistance may be lowered. From such a viewpoint, SiO ₂ − (1/2 × Al ₂ O ₃ ) is preferably 45 mol% to 69 mol%, more preferably 55 mol% or more and less than 65 mol%, and still more preferably 60 to 64 mol%.

If the molar ratio SiO ₂ / Al ₂ O ₃ is too large, the etching rate may decrease. From such a viewpoint, the molar ratio SiO ₂ / Al ₂ O ₃ is preferably less than 10, more preferably 6.0 or less, still more preferably 5.7 or less or less than 5.7. On the other hand, if the value of SiO ₂ / Al ₂ O ₃ is too small, the devitrification resistance may be lowered. From such a viewpoint, the molar ratio SiO ₂ / Al ₂ O ₃ is preferably 3.5 or more and less than 10, more preferably 4.0 to 6.0, still more preferably 4.5 or more and less than 5.7. Alternatively, the molar ratio SiO ₂ / Al ₂ O ₃ is preferably 3.0 to 5.7, more preferably 3.5 to 5.7, still more preferably 4.0 to 5.7, and still more preferably 4.5 to 5.6.
Note that in a glass having a composition in which the value of SiO ₂ + (2 × Al ₂ O ₃ ) is approximate, the etching rate depends more remarkably on SiO ₂ / Al ₂ O ₃ . From the viewpoint of achieving both high strain point, devitrification resistance and etching rate, SiO ₂ + (2 × Al ₂ O ₃ ) is 75 to 100 mol%, and SiO ₂ / Al ₂ O ₃ is 3.5 or more. It is preferably less than 10, more preferably, SiO ₂ + (2 × Al ₂ O ₃ ) is 92 to 98 mol%, and SiO ₂ / Al ₂ O ₃ is in the range of 4.0 to 6.0. preferable.

B ₂ O ₃ and B ₂ O ₃ + P ₂ O ₅ is the total amount of P ₂ O ₅ tends too small meltability is deteriorated, the too large B ₂ O ₃ + P ₂ O ₅ Glass inhomogeneity becomes prominent, striae tend to occur, and the strain point tends to decrease. Therefore, B ₂ O ₃ + P ₂ O ₅ is preferably 0 to 15 mol%, preferably 0 to 8 mol%, more preferably 0 to 7 mol%, still more preferably 0.1 to 6 mol%, more preferably 1 to 5 mol%. More preferably, it is in the range of 1.5 to 4.5 mol%.

MgO, CaO, SrO and BaO are components that lower the specific resistance and melting temperature of the molten glass and improve the meltability. MgO + CaO + SrO + BaO (hereinafter referred to as RO) which is the total content of MgO, CaO, SrO and BaO
When there is too little, meltability will deteriorate. When there is too much RO, a strain point and a Young's modulus will fall, and a density and a thermal expansion coefficient will rise. From such a viewpoint, RO is preferably in the range of 5 to 25 mol%, more preferably in the range of 8 to 18 mol%, still more preferably in the range of 10 to 18 mol%, and still more preferably in the range of 10 to 17 mol%.

The molar ratio (SiO ₂ + (2 × Al ₂ O ₃ )) / (2 × B ₂ O ₃ ) + RO) is mainly an index of strain point and devitrification resistance. If the value is too small, the strain point decreases. On the other hand, when the value is too large, meltability and devitrification resistance are lowered. Therefore, the molar ratio (SiO ₂ + (2 × Al ₂ O ₃ )) / (2 × B ₂ O ₃ ) + RO) is preferably 2.8 to 20, more preferably 3.1 to 20, further preferably 3.1 to 15 More preferably, it is in the range of 3.5 to 10, more preferably 3.7 to 7.

  In order to effectively reduce the devitrification temperature without excessively reducing the strain point, or without excessively decreasing the strain point and increasing the specific resistance, the devitrification temperature is effectively reduced. In order to decrease, BaO / RO is 0.05 to 1, more preferably 0.05 to 0.6, and still more preferably 0.1 to 0.5.

  In order to effectively lower the devitrification temperature without increasing the density too much, CaO / RO is preferably 0.1 to 0.8, more preferably 0.2 to 0.7, more preferably 0.2 to 0.6, and even more preferably 0.2 to 0.6. It is in the range of 0.5.

  The molar ratio MgO / (RO + ZnO) is an indicator of devitrification resistance and meltability. MgO / (RO + ZnO) is preferably in the range of 0.1 to 1, more preferably 0.1 to 0.9, still more preferably 0.1 to 0.85, more preferably 0.15 to 0.7, and still more preferably 0.15 to 0.6. By setting it as these ranges, devitrification resistance and meltability can be made compatible. Further, the density can be reduced.

Glass devitrification temperature with low SiO ₂ content (for example, SiO ₂ content of 80 mol% or less) and high Al ₂ O ₃ content (for example, Al ₂ O ₃ content of 8 mol% or more) In order to effectively lower the SrO <0.25 × CaO, it is preferable. That is, the SrO content is preferably less than 0.25 times the CaO content, more preferably SrO <0.2 × CaO, and even more preferably SrO <0.1 × CaO. Alternatively, the molar ratio SrO / RO is preferably 0 to 0.1.

Li ₂ O, Na ₂ O, and K ₂ O are components that increase the basicity of the glass, facilitate oxidation of the fining agent, and exhibit fining properties. Moreover, it is a component which reduces the viscosity in melting temperature and improves meltability. Moreover, it is also a component which reduces the specific resistance of molten glass. When Li ₂ O, Na ₂ O and K ₂ O are contained, the specific resistance of the molten glass decreases, and the clarity and meltability are improved. In particular, it is possible to prevent the current from flowing excessively through the refractory constituting the melting tank and to suppress the erosion of the melting tank. Moreover, when a melting tank contains a zirconia, since the elution of the zirconia from a melting tank to glass can be suppressed, the devitrification resulting from a zirconia can also be suppressed. Moreover, since the viscosity of molten glass is reduced, meltability and clarity are improved. However, if the total content of Li ₂ O, Na ₂ O and K ₂ O is too large, it may be eluted from the glass substrate and deteriorate the TFT characteristics. In addition, the strain point tends to decrease and the thermal expansion coefficient tends to increase. The total content of Li ₂ O, Na ₂ O and K ₂ O (hereinafter referred to as R ₂ O) is 0 to 0.8 mol%, more preferably 0.01 to 0.8 mol%, still more preferably It is 0.01-0.5 mol%, More preferably, it is 0.1-0.4 mol%, More preferably, it is 0.2-0.3 mol%.

K ₂ O has a higher molecular weight than Li ₂ O and Na ₂ O, and thus is difficult to elute from the glass substrate. Therefore, it is preferable to contain more K ₂ O than Li ₂ O or Na ₂ O. When the ratio of Li ₂ O and Na ₂ O is large, there is a strong risk of elution from the glass substrate and deterioration of the 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, further preferably 0.65 to 1, and more preferably 0.7 to 1.

The molar ratio (SiO ₂ + (2 × Al ₂ O ₃ )) / ((2 × B ₂ O ₃ ) + RO + (10 × R ₂ O)) is mainly an index of strain point and meltability. If the value is too small, the strain point decreases. Therefore, the molar ratio (SiO ₂ + (2 × Al ₂ O ₃ )) / ((2 × B ₂ O ₃ ) + RO + (10 × R ₂ O)) is 2.5 or more, preferably in the range of 3.0 or more It is. On the other hand, when the value is too large, meltability and devitrification resistance are lowered. Therefore, the molar ratio ((SiO ₂ + (2 × Al ₂ O ₃ )) / ((2 × B ₂ O ₃ ) + RO + (10 × R ₂ O)) is preferably 2.5 to 22, more preferably 3.0. It is in the range of ˜10. (SiO ₂ + (2 × Al ₂ O ₃ )) / ((2 × B ₂ O ₃ ) + RO + (10 × R ₂ O)) is preferably 3.5 to 7. .

RE ₂ O ₃ is the total amount of rare earth metal oxides, which include Sc ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , Pr ₂ O ₃ , Nd ₂ O ₃ , Sm Examples include ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Tm ₂ O ₃ , Yb ₂ O ₃ , and Lu ₂ O ₃ As mentioned. RE ₂ O ₃ is a component that increases the density and the thermal expansion coefficient. Moreover, it is a component with high cost. Therefore, RE ₂ O ₃ is 0 or more and less than 1.0 mol% (including 0), more preferably in the range of 0 to 0.5 mol% (including 0), and it is particularly preferable that it is not substantially contained.

From the viewpoint of preventing increase in density and thermal expansion coefficient and reducing cost, it is preferable that Y ₂ O ₃ and La ₂ O are not substantially contained.

  The glass substrate of this embodiment has a devitrification temperature of preferably 1280 ° C. or lower, more preferably 1250 ° C. or lower, and further preferably 1210 ° C. or lower. The lower the devitrification temperature, the easier it is to form the glass plate by the overflow downdraw method. By applying the overflow downdraw 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 devitrification temperature is too high, devitrification is likely to occur, so that application to the overflow downdraw method tends to be difficult.

Glass substrate of the present embodiment, the average thermal expansion coefficient at 100 ℃ ~300 ℃ (100-300 ℃) is, is a 50.0 × 10 ^-7 ℃ ^-1 or less, is 28.0~50.0 × 10 ^-7 ℃ ^-1 More preferably, 33.0 to 46.0 × 10 ⁻⁷ ° C.− ¹ , further preferably 33.0 to 45.0 × 10 ⁻⁷ ° C.− ¹ , more preferably 35.0 or more and less than 43.0 × 10 ⁻⁷ ° C.− ¹ , even more preferable. Is in the range of 38.0 to 43.0 × 10 ⁻⁷ ° C. ⁻¹ . When the thermal expansion coefficient is large, the thermal shock and the thermal contraction rate tend to increase in the heat treatment process. Further, if the thermal expansion coefficient is large, it is difficult to reduce the thermal shrinkage rate. Note that, regardless of whether the thermal expansion coefficient is large or small, it is difficult to match the thermal expansion coefficient with the peripheral material such as metal or thin film formed on the glass substrate, and the peripheral member may be peeled off.

  In general, when a glass substrate has a low strain point, heat shrinkage tends to occur in a heat treatment process during display manufacturing. The glass substrate of this embodiment has a strain point of 670 ° C. or higher, more preferably 700 ° C. or higher, and further preferably 710 ° C. or higher.

  The glass substrate of the present embodiment preferably has a thermal shrinkage rate of 90 ppm or less or 75 ppm or less. If the thermal contraction rate becomes too large, a large pitch shift of pixels is caused, and a high-definition display cannot be realized. In order to control the heat shrinkage rate within a predetermined range, it is preferable that the strain point of the glass substrate is 670 ° C. or higher or 700 ° C. or higher. In order to reduce the heat shrinkage rate to 0 ppm, it is required to make the slow cooling process extremely long, or to perform heat shrinkage reduction treatment (offline slow cooling) after the slow cooling and cutting process. Will drop and costs will rise. In view of productivity and cost, the heat shrinkage rate is preferably, for example, 3 to 90 ppm, 3 to 75 ppm, or 5 to 75 ppm, more preferably 5 ppm to 60 ppm, further preferably 10 ppm to 55 ppm, more preferably 15 ppm to 50 ppm.

The thermal shrinkage rate was 10 ° C / min. At a heating rate of 10 ° C / min, held at 550 ° C for 2 hours, and the temperature was lowered to 400 ° C over 55 min. ), And then the following formula after the heat treatment to cool to room temperature.
Thermal shrinkage (ppm) = {Shrinkage amount of glass before and after heat treatment / Glass length before heat treatment} × 10 ⁶
At this time, “the amount of shrinkage of the glass before and after the heat treatment” is “the length of the glass before the heat treatment−the length of the glass after the heat treatment”.

The glass substrate of the present embodiment has a density of preferably 3.0 g / cm ³ or less, more preferably 2.8 g / cm ³ or less, and further preferably 2.65 g / cm, from the viewpoints of reducing the weight of the glass substrate and the display. ³ or less. If the density becomes too high, it is difficult to reduce the weight of the glass substrate, and it is difficult to reduce the weight of the display.

When the glass transition point (hereinafter referred to as Tg) is lowered, thermal shrinkage tends to occur in the heat treatment step of display production. The glass substrate of the present embodiment has a Tg of preferably 720 ° C. or higher, more preferably 750 ° C. or higher, and further preferably 760 ° C. or higher. In order to make the Tg of the glass substrate in the above range, in the range of the composition of the glass substrate of the present embodiment, for example, more components such as SiO ₂ and Al ₂ O ₃ , or B ₂ O ₃ , RO, R It is appropriate to reduce the ₂ O component.

The glass of this embodiment has a temperature at which the viscosity is 10 ^2.5 [dPa · s] (hereinafter referred to as a melting temperature), preferably 1680 ° C. or less, more preferably 1500 to 1680 ° C., and still more preferably It is in the range of 1520 to 1660 ° C, more preferably 1560 to 1640 ° C. Glass having a low melting temperature tends to have a low strain point. In order to increase the strain point, it is necessary to increase the melting temperature to some extent. However, when the melting temperature is high, the load on the melting tank increases. Moreover, since energy is used in large quantities, cost also becomes high. Moreover, when applying electric melting to glass melting, an electric current flows into the heat-resistant brick which forms not a glass but a melting tank, and a melting tank may be damaged. In order to bring the melting temperature of the glass within the above range, it is appropriate to contain components such as B ₂ O ₃ , RO, etc. within the above-mentioned range that lower the viscosity in the composition range of the glass substrate of the present embodiment. It is.

The molten glass when producing the glass substrate of the present embodiment has a specific resistance (at 1550 ° C.) of preferably 30 to 700 Ω · cm, more preferably 30 to 400 Ω · cm, still more preferably 30 to 300 Ω · cm, one layer Preferably it is the range of 50-300 ohm * cm. If the specific resistance becomes too small, the current value necessary for melting becomes excessive, and there may be restrictions on the equipment. In addition, there is a tendency that the consumption of the electrode increases. If the specific resistance of the molten glass becomes too large, the current may flow not to the glass but to the heat-resistant brick forming the melting tank, and the melting tank may be melted. The specific resistance of the molten glass can be adjusted to the above range mainly by controlling the contents of RO, R ₂ O, and Fe ₂ O ₃ .

The glass constituting the glass substrate of the present embodiment preferably has an etching rate of 50 μm / h or more. Productivity improves as the etching rate increases. In particular, when the glass substrate is etched after bonding the glass substrate on the TFT side and the color filter side to reduce the weight, the etching rate affects the productivity. However, if the etching rate becomes too high, the productivity at the time of manufacturing the display is improved, but the devitrification resistance of the glass is lowered. In addition, the thermal shrinkage tends to increase. The etching rate is preferably 60 to 140 μm / h, more preferably 65 to 120 μm / h, still more preferably 70 to 120 μm / h. In order to increase the etching rate of glass, the value of SiO ₂ − (1/2 × Al ₂ O ₃ ) or SiO ₂ / Al ₂ O ₃ may be reduced. In the present embodiment, the etching rate is defined as measured under the following conditions. The etching rate (μm / h) in this specification is a unit time when the glass substrate is immersed in an etching solution at 40 ° C. adjusted to have an HF concentration of 1 mol / kg and an HCl concentration of 5 mol / kg for 1 hour. It is the thickness reduction amount (μm) of one surface of the glass substrate per (1 hour).

  The glass substrate of this embodiment can have a plate thickness in the range of, for example, 0.1 to 1.1 mm, or 0.3 to 1.1 mm. However, it is not intended to limit to this range. The plate thickness may be in the range of 0.3 to 0.7 mm, 0.3 to 0.5 mm, for example. If the glass plate is too thin, the strength of the glass substrate itself is reduced. For example, damage during flat panel display manufacturing is likely to occur. If the plate thickness is too thick, it is not preferable for a display that is required to be thin. In addition, since the weight of the glass substrate becomes heavy, it is difficult to reduce the weight of the flat panel display. Furthermore, when the glass substrate is etched after the TFT is formed, the amount of the etching process increases, which increases cost and time.

  The glass substrate of this embodiment is used, for example, in the manufacture of a flat panel display in which the glass substrate surface is etched after the array / color filter is bonded. The glass substrate of the present embodiment is suitable for a display glass substrate (however, a CRT (CRT) display is excluded). In particular, the glass substrate of the present embodiment is suitable for a glass substrate for flat panel display on which LTPS-TFT or OS-TFT is formed. Specifically, it is suitable for a glass substrate for liquid crystal display and a glass substrate for organic EL display. Particularly, it is suitable for a glass substrate for LTPS-TFT liquid crystal display and a glass substrate for LTPS-TFT organic EL display. Especially, it is suitable for the glass substrate for displays, such as a portable terminal in which high definition is calculated | required.

<Flat panel display>
The present embodiment includes a flat panel display in which LTPS-TFT or OS-TFT is formed on the surface of a glass substrate, and the glass substrate of the flat panel display is the glass substrate of the present embodiment. The flat panel display of this embodiment can be, for example, a liquid crystal display or an organic EL display.

<Glass substrate manufacturing method>
The method for producing a glass substrate for display of the present embodiment includes a melting step of melting a glass raw material prepared in a predetermined composition, for example, using at least direct current heating,
A forming step of forming the molten glass melted in the melting step into a 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 conditions of the flat glass so as to reduce the thermal shrinkage rate of the flat glass.

[Melting Step] In the melting step, the glass raw material prepared to have a predetermined composition is melted using, for example, direct current heating and / or combustion heating. The glass raw material can be appropriately selected from known materials. From the viewpoint of energy efficiency, in the melting step, it is preferable to melt the glass raw material using at least direct current heating. Moreover, it is preferable that the melting tank which performs a melting process is comprised including a high zirconia refractory. The said predetermined composition can be suitably adjusted, for example in the range with which content mentioned above regarding each component of glass is satisfy | filled.

[Molding process]
In the forming step, the molten glass melted in the melting step is formed into flat glass. For example, the down-draw method, particularly the overflow down-draw method is suitable as a method for forming the flat glass, and a glass ribbon is formed as the flat glass. In addition, a float method, a redraw method, a rollout method, etc. can be applied. By adopting the downdraw method, compared to the case where other molding methods such as the float method are used, the main surface of the obtained glass substrate is formed with a free surface that is non-contact except for the atmosphere. Since it has high smoothness and does not require a polishing step on the surface of the glass substrate after molding, the manufacturing cost can be reduced and the productivity can also be improved. In addition, since both main surfaces of the glass substrate molded using the downdraw method have a uniform composition, etching is performed uniformly regardless of the front and back of the molding process. Can do.

[Slow cooling process]
The heat shrinkage rate of the glass substrate can be controlled by appropriately adjusting the conditions during slow cooling. In particular, it is preferable to control the cooling conditions of the flat glass so as to reduce the thermal shrinkage of the flat glass. As described above, the thermal shrinkage rate of the glass substrate is 90 ppm or less, preferably 75 ppm or less, more preferably 5 to 75 ppm. In order to manufacture a glass substrate having such a thermal contraction rate, for example, when using the downdraw method, the cooling rate of the glass ribbon as a flat glass is changed from Tg (Tg-100 ° C). In this temperature range, it is preferable to perform slow cooling so that it may be 30-300 degreeC / min. If the cooling rate is too high, the heat shrinkage rate cannot be reduced sufficiently. On the other hand, when the cooling rate is too slow, productivity is lowered and a problem arises that the glass manufacturing apparatus (slow cooling furnace) is enlarged. A preferable range of the cooling rate is 30 to 300 ° C./min, more preferably 50 to 200 ° C./min, and further preferably 60 to 120 ° C./min. By setting the cooling rate to 30 to 300 ° C./min, the glass substrate of this embodiment can be more reliably manufactured. In addition, after cutting the flat glass downstream of the slow cooling step, the thermal shrinkage rate can also be reduced by separately cooling it offline, but in this case, in addition to the equipment for performing the slow cooling step, separately Equipment that performs slow cooling offline is required. Therefore, as described above, it is preferable from the viewpoint of productivity and cost to control the thermal shrinkage rate in the slow cooling step so that offline slow cooling can be omitted. In addition, in this specification, the cooling rate of a glass ribbon shall show the cooling rate of the center part of the width direction of a glass ribbon.

  Hereinafter, the present embodiment will be described in more detail based on examples. However, the present embodiment is not limited to the examples. In the following examples and comparative examples, the physical properties described below were measured.

(Strain point)
Measurement was performed using a beam bending measuring apparatus (manufactured by Tokyo Kogyo Co., Ltd.), and a strain point was determined by calculation according to the beam bending method (ASTM C-598).

(Devitrification temperature)
The glass was crushed, and glass particles that passed through a 2380 μm sieve and remained on the 1000 μm sieve were placed in a platinum boat. This platinum boat was held in an electric furnace having a temperature gradient of 1050 to 1380 ° C. for 5 hours, and then removed from the furnace, and devitrification generated in the glass was observed with a 50 × optical microscope. The maximum temperature at which devitrification was observed was defined as the devitrification temperature.

(Resistivity at 1550 ° C)
The specific resistance of the molten glass was measured by a four-terminal method using a HP 4192A LF impedance analyzer, and the specific resistance value at 1550 ° C. was calculated from the measurement result.

(Measuring method of average thermal expansion coefficient α and Tg in the range of 100 to 300 ° C)
It measured using the differential thermal dilatometer (Thermo Plus2 TMA8310). The temperature rising rate at this time was 5 ° C./min. Based on the measurement results, the average thermal expansion coefficient and Tg in the temperature range of 100 to 300 ° C. were determined.

(Heat shrinkage)
The thermal shrinkage rate was determined by the marking line method for glass having a size of 90 mm to 200 mm × 15 to 30 mm × 0.5 to 1 mm. As heat treatment for heat shrinkage measurement, using an air circulation furnace (Nabertherm N120 / 85HA), the temperature was raised from room temperature at 10 ° C / min, held at 550 ° C for 2 hours, and lowered to 400 ° C over 55 minutes. (The temperature drop rate was about 2.7 ° C./min), and then the door of the air circulation furnace was opened halfway and allowed to cool to room temperature.
Thermal shrinkage rate (ppm) = {Shrinkage amount of glass in heat treatment / Distance between scribing lines of glass before heat treatment} × 10 ⁶ When measuring the thermal shrinkage of the obtained glass, cut, grind and polish to a thickness of 0.7 mm, hold for 30 minutes at a temperature of Tg + 15 ° C using an electric furnace, then 4 minutes Glass taken out of the furnace was used. The average cooling rate in the range of Tg + 15 to 150 ° C. at this time was 100 to 200 ° C./min.

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

(Etching rate)
The etching rate (μm / h) is the value when glass (12.5 mm x 20 mm x 0.7 mm) is immersed in an etching solution (200 mL) adjusted to HF concentration 1 mol / kg and HCl concentration 5 mol / kg for 1 hour. The thickness reduction amount (μm) was measured, and the thickness reduction amount (μm) of one surface of the glass substrate per unit time (1 hour) was calculated.

  Hereinafter, the composition and evaluation of Examples and Comparative Examples will be described in three forms of glass substrates (A) to (C).

(Glass substrate (A): Examples 1 to 60, Comparative Examples 1 to 3)
The glass of Examples 1-60 and Comparative Examples 1-3 was produced according to the following procedures so that it might become the glass composition shown to Tables 1-4. About the obtained glass, the strain point, devitrification temperature, Tg, the average thermal expansion coefficient ((alpha)) in the range of 100-300 degreeC, the thermal contraction rate, the density, and the etching rate were calculated | required.

  The raw materials of each component were prepared and melted, clarified, and molded so as to have the glass compositions shown in Tables 1 to 4.

  Of the glasses obtained as described above, Examples 1 to 60 had a heat shrinkage of 90 ppm or less. The specific resistance of the molten glass at 1550 ° C. was also 700 Ω · cm or less. Moreover, the same result was obtained also when the glass raw material was melted using direct current heating and a glass substrate was produced by the overflow down draw method. Therefore, by using these glasses, a glass substrate that can be used for a display to which LTPS-TFT is applied can be manufactured by an overflow downdraw method. Moreover, these glass substrates are also suitable as a glass substrate for OS-TFT.

  On the other hand, in Comparative Examples 1 to 3, although the specific resistance of the molten glass at 1550 ° C. was 700 Ω · cm or less, the strain point was less than 670 ° C. Furthermore, Comparative Example 1 had a thermal shrinkage rate far exceeding 90 ppm.

(Glass substrate (B): Examples 101 to 148 and Comparative Example 101)
The glasses of Examples 101 to 148 and Comparative Example 101 were produced according to the following procedure so that the glass compositions shown in Tables 5 to 7 were obtained. About the obtained glass, the strain point, devitrification temperature, Tg, the average thermal expansion coefficient ((alpha)) in the range of 100-300 degreeC, the thermal contraction rate, the density, and the etching rate were calculated | required.

  The raw materials of each component were prepared and melted, clarified, and molded so as to have the glass compositions shown in Tables 5-7.

The glasses of Examples 101 to 148 obtained as described above had a heat shrinkage rate of 5 to 75 ppm. The devitrification temperature was 1280 ° C. or lower. In contrast, in Comparative Example 101 where MgO / (RO + ZnO) was 0.95, the heat shrinkage rate was 5 to 75 ppm, but the devitrification temperature was higher than 1280 ° C.
Moreover, the same result was obtained also when the glass raw material was melted using direct current heating and the glass substrate was produced by the overflow down draw method. Therefore, by using the glasses of Examples 101 to 148, a glass substrate that can be used for a display to which LTPS-TFT is applied can be manufactured by the overflow downdraw method. Further, the glass substrates of Examples 101 to 148 are also suitable as OS-TFT glass substrates.

(Glass substrate (C): Examples 201 to 255 and Comparative examples 201 to 203)
Glasses of Examples 201 to 255 and Comparative Examples 201 to 203 were produced according to the following procedure so that the glass compositions shown in Tables 8 to 11 were obtained. About the obtained glass, the strain point, devitrification temperature, Tg, the average thermal expansion coefficient ((alpha)) in the range of 100-300 degreeC, the thermal contraction rate, the density, and the etching rate were calculated | required.

  The raw materials of each component were prepared and melted, clarified, and molded so as to have the glass compositions shown in Tables 8 to 11.

  The glass obtained as described above had a strain point of 700 ° C. or higher. Further, the etching rate was 50 μm / h or more. Therefore, by using these glasses, a glass substrate that can be used for a display to which LTPS-TFT is applied can be manufactured by an overflow downdraw method. Moreover, these glass substrates are also suitable as a glass substrate for OS-TFT.

In Examples 201 to 255 and Comparative Example 203 in which SiO ₂ / Al ₂ O ₃ was 6.0 or less, the etching rate was 65 (μm / h) or more, which was favorable. On the other hand, in Comparative Examples 201 and 202 with SiO ₂ / Al ₂ O ₃ exceeding 6.0, the etching rate was 62 (μm / h) or less, which was not good.
In Examples 1 to 55 and Comparative Examples 1 and _{2 in which} the content of B ₂ O ₃ was 7% or less, the strain point was higher than 700 ° C. The devitrification temperature was 1100 ° C or higher.
On the other hand, in Comparative Example 203 having a B ₂ O ₃ content of 12.0%, the devitrification temperature decreased to 1050 ° C., but the strain point decreased to 660 ° C.

Claims (12)

In mol%
SiO ₂ 60~80%,
Al ₂ O ₃ 8-20%,
B ₂ O ₃ 0-8%,
MgO 2.1-15%,
R ₂ O 0.01-0.8%,
BaO / RO is 0.05-1
Substantially free of Y ₂ O ₃ and La ₂ O ₃ ,
A glass substrate for display formed from glass having a strain point of 670 ° C. or higher.
Here, RO represents (MgO + CaO + SrO + BaO), and R ₂ O represents (Li ₂ O + Na ₂ O + K ₂ O). In mol%
SiO ₂ 60~80%,
Al ₂ O ₃ 8-20%,
B ₂ O ₃ 0-8%,
MgO 2.1-15%,
R ₂ O 0.01-0.8%,
(SiO ₂ + (2 × Al ₂ O ₃ )) / ((2 × B ₂ O ₃ ) + RO + (10 × R ₂ O)) is 2.5 or more,
BaO / RO is 0.05-1
Substantially free of Y ₂ O ₃ and La ₂ O ₃ ,
A glass substrate for display formed from glass having a strain point of 670 ° C. or higher.
Here, RO represents (MgO + CaO + SrO + BaO), and R ₂ O represents (Li ₂ O + Na ₂ O + K ₂ O). In mol%
CaO 0-20%,
SrO 0-15%,
The glass substrate of Claim 1 or 2 containing BaO 0.1-15%. The glass substrate according to any one of claims 1 to 3, wherein SiO _2- (1/2 × Al ₂ O ₃ ) is less than 65% in terms of mol%. By _{mol%, B 2 O 3 + RO +} ZnO is 15 to 25%, a glass substrate according to any one of claims 1 to 4. Containing SnO ₂ and Fe ₂ O ₃ ,
In mol%
SnO ₂ 0.03-0.15%,
The glass substrate according to any one of claims 1 to 5, wherein the total amount of SnO ₂ and Fe ₂ O ₃ is 0.05 to 0.2%. In mol%
SiO ₂ 66-72%,
Al ₂ O ₃ 11-15%,
B ₂ O ₃ 0-8%,
MgO 2.1-6%,
CaO 2-11%,
SrO 0-1%,
The glass substrate of any one of Claims 1-6 containing BaO 1-10%. The as ₂ O ₃ does not substantially contain a glass substrate according to any one of claims 1-7. The molar ratio ((SiO ₂ + (2 × Al ₂ O ₃ )) / ((2 × B ₂ O ₃ ) + RO + (10 × R ₂ O)) is _{2.5 to} 5.0. The glass substrate of any one of Claims.   The glass substrate according to any one of claims 1 to 9, comprising 10 to 18% of RO in terms of mol%.   The glass substrate according to any one of claims 1 to 10, which contains CaO and has a molar ratio CaO / RO of 0.52 or less. A melting step of melting a glass raw material prepared to a predetermined composition using at least direct current heating;
A forming step of forming the molten glass melted in the melting step into a flat glass;
The step of gradually cooling the flat glass, comprising a slow cooling step of controlling cooling conditions of the flat glass so as to reduce the thermal shrinkage rate of the flat glass. A method for producing a glass substrate for display, wherein the glass substrate according to claim 1 is produced.