JP5484220B2 - Glass substrate for display device and display device - Google Patents

Description

  The present invention relates to a glass substrate for a display device and a display device.

More specifically, the present invention relates to a glass substrate for a display device used in a liquid crystal display device (LCD), an electroluminescence display device (ELD), a field emission display device (FED), and the like, and a display device using the glass substrate. It is.

  When glass containing an alkali component is used as a glass substrate constituting a thin film transistor driving color liquid crystal display (TFT-LCD), alkali ions in the glass substrate are eluted to deteriorate TFT characteristics, and the glass has a large thermal expansion coefficient. The glass substrate is damaged during the heat treatment. For this reason, as a glass substrate for TFT-LCD, the alkali free glass which does not contain an alkali component is generally used (for example, refer patent document 1).

  By the way, in recent years, display devices such as liquid crystal display devices have been steadily increasing in size, and accordingly, in glass substrates used in display devices, for example, the amount of bubbles remaining in the glass substrate is reduced. It has been demanded to further reduce the weight of the glass substrate.

In the process of producing a glass substrate, the prevention of bubbles and the like from remaining in the glass substrate is referred to as a fining treatment, and this fining treatment is generally performed by adding a fining agent to the glass melt. In particular, arsenic oxide, antimony oxide, and the like are suitably used as a fining agent for glass substrates for liquid crystals. In these fining agents, when the glass reaches a high temperature from a low temperature, the metal constituting the fining agent is used. A reaction of MO _x → MO _y + zO ₂ ↑ accompanied by valence fluctuation occurs, and entrained bubbles are expanded by oxygen generated at this time, and floating defoaming is performed.

  However, the arsenic oxide, antimony oxide, and the like, which are known for their high clarification effect, are concerned about the environmental impact, and so reduction of their usage and emissions has become a social requirement.

For this reason, Patent Document 1 has reported a method of defoaming without using arsenic oxide by containing 0.05 to ₂ % of SnO ₂ in the alkali-free aluminoborosilicate glass.

Japanese Patent Laid-Open No. 10-59741

  However, as a result of intensive studies by the present inventors, in general, the alkali-free aluminoborosilicate glass used in the active matrix liquid crystal display device has a high viscosity, so that the clarification method described in Patent Document 1 performs a sufficient clarification treatment. It turned out to be difficult.

  Further, as a result of intensive studies by the present inventors, it has been clarified that clarification of molten glass becomes more difficult than ever when the glass density is reduced in order to reduce the weight of the glass substrate.

That is, according to the study by the present inventors, in order to reduce the density of glass, generally an alkaline earth metal oxide having a large mass number such as barium oxide or strontium oxide is used as a mass such as magnesium oxide or calcium oxide. Substitution with a small number of alkaline earth metal oxides or substitution with network-forming oxides such as boron oxide, aluminum oxide, and silicon oxide is effective, but by these substitutions, melting of SnO ₂ or the like It has been found that the clarification effect due to oxides of metals whose valence fluctuates in glass is reduced. This is considered not only because the viscosity increases due to an increase in the network-forming oxide, but also because the basicity and oxidation degree of the glass decrease due to the above substitution.

  As described above, the refining action by the oxide of the metal whose valence fluctuates is that the metal having a high oxidation number changes to a low valence as the temperature rises in the glass melt after the initial melting and releases oxygen at that time. It is expressed by. Therefore, in order to obtain the effect, the metal oxide whose valence fluctuates must be maintained in a sufficiently oxidized state after the initial melting of the raw material is completed until it becomes a glass melt. .

  However, the metal oxide whose valence fluctuates has a property that the higher the basicity of the glass, the easier it is oxidized (that is, the lower the basicity of the glass, the less likely it is oxidized and the lower the valence). .

Therefore, in order to reduce weight, the amount of components such as barium oxide and strontium oxide is reduced, and the amount of components such as calcium oxide and magnesium oxide with lower basicity is increased, as well as acidic to neutral boron oxide, oxidized In molten glass with increased amounts of aluminum and silicon oxide components, the basicity of the glass becomes low, making it difficult to maintain the valence of metals whose valence fluctuates, resulting in sufficient clarity. It will not be possible.

  In order to promote oxidation and suppress reduction in oxides of valence-fluctuating metals, use an oxidizing substance as a glass raw material, specifically, an alkaline earth metal nitrate as a part of the raw material Can be considered. However, alkaline earth metal nitrates have a decomposition temperature of, for example, 1100 ° C. for strontium nitrate, but 400 ° C. for magnesium nitrate, and the decomposition temperature of metal element nitrates with lower mass numbers is lower. Therefore, glass using mainly magnesium nitrate and calcium nitrate as nitrates loses oxidation ability at an extremely early stage when the glass raw material is dissolved. In addition, calcium and magnesium nitrates are particularly easy to deliquesce compared to barium and strontium nitrates, and industrially available hydrates easily liquefy even at low temperatures below 100 ° C. When added in large quantities, it tends to cause solidification of raw materials and adhesion to equipment in the transfer line, making it difficult to perform stable operation.

  Therefore, conventionally, a substrate for a display device made of borosilicate glass has a problem that it is extremely difficult to obtain a substrate that is lightweight and has high clarity while reducing the environmental load.

  Under such circumstances, it is an object of the present invention to provide a glass substrate for a display device that is lightweight and has high clarity while reducing environmental burden, and a display device using the glass substrate. Is.

As a result of intensive studies to achieve the above object, the present inventors have found that SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , RO (R is at least one selected from Mg, Ca, Sr and Ba). And R ′ ₂ O (R ′ is at least one selected from Li, Na and K), and a predetermined amount of a metal oxide whose valence fluctuates in the molten glass. It has been found that the object can be achieved by a glass substrate for a display device comprising an aluminoborosilicate glass substantially free of ₂ O ₃ , Sb ₂ O ₃ and PbO, and the present invention has been completed based on this finding. It was.

That is, the present invention
(1) In mass% display,
SiO ₂ 50~70%,
B ₂ O ₃ 5~18%,
Al ₂ O ₃ 10-25%,
MgO 0-10%,
CaO 0-20%,
SrO 0-20%,
BaO 0-10%,
RO 5-20%
(Wherein R is at least one selected from Mg, Ca, Sr and Ba),
R ′ ₂ O 0.20% or more and 2.0% or less (where R ′ is at least one selected from Li, Na and K)
Including
A total of 0.05 to 1.5% of metal oxides whose valence fluctuates in the molten glass , the glass contains tin oxide as an essential component as a metal oxide whose valence fluctuates in the molten glass,
A glass substrate for a display device, characterized by being made of glass that does not substantially contain As ₂ O ₃ , Sb ₂ O _3, and PbO, and does not contain halide ions in the glass except when it is contained as an impurity ;
(2) In mass% display,
SiO ₂ 55~65%,
B ₂ O ₃ 10-14%,
Al ₂ O ₃ 15-19%,
MgO 1-3%,
CaO 4-7%,
SrO 1-4%,
BaO 0-2%
RO 6-16%
(Wherein R is at least one selected from Mg, Ca, Sr and Ba),
R ′ ₂ O 0.20% or more and 2.0% or less (where R ′ is at least one selected from Li, Na and K)
Including
Including 0.1 to 1.5% in total of oxides of metals whose valence fluctuates in molten glass,
Glass contains tin oxide as an essential component as a metal oxide whose valence fluctuates in molten glass,
The glass substrate for a display device according to the above (1), which is substantially free of As ₂ O ₃ , Sb ₂ O ₃ and PbO and is made of glass containing no halide ions in the glass, except when contained as impurities ,
(3) The glass substrate for a display device according to (1) or (2), wherein the content of R ′ ₂ O is 0.20% or more and 0.5% or less,
(4) R 'includes _{K 2} O as ₂ O, substantially Li ₂ O and Na ₂ O made of glass that does not contain the above (1) to (3) for a display device glass substrate according to any one of,
(5) Display device according to any one of made of glass containing at least one selected from oxides and to acid iron and cerium oxide of a metal that changes in valence number in a molten glass (1) to (4) Glass substrate for
(6) The glass substrate for a display device according to any one of (1) to (5), wherein the content of tin oxide in the glass is in the range of 0.01 to 0.5%,
(7) The glass substrate for a display device according to (5) or (6), wherein the content of iron oxide in the glass is in the range of 0.05 to 0.2%,
(8) The glass substrate for a display device according to any one of (5) to (7), wherein the content of cerium oxide in the glass is in the range of 0 to 1.2%,
(9) The glass for a display device according to any one of the above (1) to (8), wherein the content of sulfur oxide in the glass is limited to 0% by mass or more and less than 0.010% by mass in terms of SO _3. substrate,
(10) The glass substrate for a display device according to any one of (1) to (9), wherein the total content of halide ions in the glass is limited to 0% by mass or more and less than 0.05% by mass,
(11) The glass substrate for a display device according to any one of (1) to (10), which is made of glass having a density of 2.49 g / cm ³ or less,
(12) The display device according to any one of the above (1) to (11), which is made of glass having a linear thermal expansion coefficient of 28 × 10 ^{−7 to} 39 × 10 ⁻⁷ / ° C. from 50 ° C. to 300 ° C. Glass substrate,
(13) A display device comprising the glass substrate for a display device according to any one of (1) to (12) ,
( 14) The display device according to (13), wherein the display device is a liquid crystal display device , and
(15) A glass raw material batch is melted and refined to produce glass, and the obtained glass is processed into a thin plate shape to produce the glass substrate for a display device according to any one of (1) to (12) above. The present invention provides a method for producing a glass substrate for a display device .

According to the present invention, the alkali metal oxide and the metal oxide whose valence fluctuates in the molten glass are respectively contained in a predetermined amount, and have a specific composition substantially free of As ₂ O ₃ , Sb ₂ O ₃ and PbO. By using a specific aluminoborosilicate glass, it is possible to provide a glass substrate for a display device that is lightweight and has high clarity while reducing environmental burden, and a display device using the glass substrate is provided. Can be provided.

  First, the glass substrate for a display device of the present invention will be described.

The glass substrate for a display device of the present invention is displayed in mass%,
SiO ₂ 50~70%,
B ₂ O ₃ 5~18%,
Al ₂ O ₃ 10-25%,
MgO 0-10%,
CaO 0-20%,
SrO 0-20%,
BaO 0-10%,
RO 5-20%
(Wherein R is at least one selected from Mg, Ca, Sr and Ba),
R ′ ₂ O 0.20% or more and 2.0% or less (where R ′ is at least one selected from Li, Na and K)
Including
Including 0.05 to 1.5% in total of oxides of metals whose valence fluctuates in the molten glass,
The _{As 2 O 3, Sb 2 O} 3 and PbO is characterized in that made of glass that is substantially free.

  Hereinafter, although the composition of the glass which comprises the glass substrate for display apparatuses of this invention is demonstrated in detail, unless otherwise specified,% shall mean the mass%.

SiO ₂ is an essential component that forms a glass skeleton, and has an effect of increasing the chemical durability and heat resistance of the glass. If the content is less than 50%, the effect cannot be obtained sufficiently, and if it exceeds 70%, the glass tends to be devitrified, making it difficult to form, and increasing the viscosity, making it difficult to homogenize the glass. become. Therefore, the content of SiO ₂ is 50 to 70%, preferably 55 to 65%, and more preferably 57 to 62%.

B ₂ O ₃ is an essential component that lowers the viscosity of the glass and promotes melting and clarification of the glass. If the content is less than 5%, the effect cannot be obtained sufficiently. If the content exceeds 18%, the acid resistance of the glass is lowered and volatilization is increased, making it difficult to homogenize the glass. Therefore, the content of B ₂ O ₃ is 5 to 18%, preferably 10 to 14%, and more preferably 11 to 13%.

Al ₂ O ₃ is an essential component forming a glass skeleton, and has an effect of improving the chemical durability and heat resistance of the glass. If the content is less than 10%, the effect cannot be obtained sufficiently. On the other hand, when the content rate exceeds 25%, the viscosity of the glass increases and melting becomes difficult, and the acid resistance decreases. Therefore, the Al ₂ O ₃ content is 10-25%, 15-19%
Is preferable, and 16 to 18% is more preferable.

  MgO and CaO are optional components that lower glass viscosity and promote glass melting and fining. Mg and Ca are advantageous components for improving the solubility while reducing the weight of the resulting glass because the proportion of the alkaline earth metal that increases the density of the glass is small. However, when the content exceeds 10% and 20%, respectively, the chemical durability of the glass decreases. Therefore, the content of MgO is 0 to 10%, preferably 0.5 to 4%, and more preferably 1 to 3%. The CaO content is 0 to 20%, preferably 4 to 7%, and more preferably 5 to 7%.

  SrO and BaO are optional components that lower the viscosity of the glass and promote glass melting and fining. Moreover, it is also a component which improves the oxidizability of a glass raw material and improves clarity. However, when the content exceeds 20% and 10%, respectively, the chemical durability of the glass is lowered. Therefore, the SrO content is 0 to 20%, preferably 1 to 4%, and more preferably 2 to 3%. Further, the content of BaO is 0 to 10%, preferably 0 to 6.5%, more preferably 0 to 2%, and still more preferably 0.5 to 1%.

Here, when RO (where R is at least one selected from Mg, Ca, Sr and Ba) is less than 5%, the viscosity of the glass becomes high and melting becomes difficult, and when it exceeds 20%, chemical durability is reached. The nature will decline. For this reason, content of RO which is the total amount of MgO, CaO, SrO, and BaO is 5 to 20%, it is preferable to set it as 6 to 16%, and it is more preferable to set it as 8 to 13%.

In order to obtain a particularly lightweight substrate, use glass containing MgO 1 to 3%, CaO 4 to 7%, SrO 1 to 4%, BaO 0 to 2%, and RO content 6 to 16%. Is preferred.

Since Li ₂ O, Na ₂ O, and K ₂ O are components that are eluted from the glass to deteriorate the TFT characteristics, or increase the thermal expansion coefficient of the glass to damage the substrate during the heat treatment. As a constituent component of a glass substrate for a display device, it has not been used so much. However, in the glass substrate of the present invention, by deliberately containing the above components in the glass, the basicity of the glass is increased while suppressing deterioration of TFT characteristics and thermal expansion of the glass within a certain range, It makes it easy to oxidize metals that fluctuate in valence, and exhibits clarity. Here, the total content of Li ₂ O, Na ₂ O and K ₂ O represented by R ′ ₂ O (where R ′ is at least one selected from Li, Na and K) is 0.20%. If the ratio is less than 2.0%, the clarification effect cannot be obtained. If the ratio exceeds 2.0%, these components are likely to be eluted after the display device is formed, and the possibility that the liquid crystal and the conductive film will be affected increases. For this reason, R ′ ₂ O is 0.20% or more and 2.0% or less. In order to obtain a suitable expansion coefficient for a liquid crystal substrate, R ′ ₂ O is preferably 0.20% or more and 0.5% or less, and more preferably 0.22% or more and 0.35% or less.

Glass substrate of the present invention, R 'together containing _{K 2} O as ₂ O, is preferably one consisting essentially free glass Li ₂ O and Na ₂ O. That is, as R ′ ₂ O, among Li ₂ O, Na ₂ O and K ₂ O, those containing only K ₂ O are preferable.

This is because, among Li ₂ O, Na ₂ O, and K ₂ O, K ₂ O having a high basicity is most excellent in the effect of improving the clarity. Alkali metal oxides are easily bonded to B ₂ O ₃ and volatilized as alkali borate. In particular, Li ⁺ and Na ⁺ having a small ionic radius have a high mobility in the glass melt and are thus easily removed from the melt surface. Since it is easy to volatilize, it is easy to generate striae on the glass surface by forming a concentration gradient to the inside of the glass. On the other hand, since K ⁺ has a large ionic radius, the moving speed in the glass melt is small and the above-described problems are hardly caused. Therefore, in this respect as well, Li ₂ O, Na ₂ O and K ₂ It can be said that the use of glass containing only K ₂ O among O is preferable.

  The metal oxide whose valence fluctuates in the molten glass is a component necessary for clarification of the glass, and if it is less than 0.05%, the effect cannot be obtained, and if it exceeds 1.5%, devitrification or coloring is caused. Therefore, the total content is 0.05 to 1.5%, preferably 0.1 to 1.5%, more preferably 0.1 to 1%, and 0.1 to 0%. More preferably, 5%.

The oxide of the metal whose valence fluctuates in the molten glass is not particularly limited as long as it has a small environmental load and excellent glass clarity. For example, tin oxide, iron oxide, cerium oxide, terbium oxide And at least one selected from metal oxides such as molybdenum oxide and tungsten oxide. Among the above metal oxides, it is selected from tin oxide, iron oxide and cerium oxide which are less harmful and show a particularly excellent clarification effect in the presence of alkali metal oxides such as Li ₂ O, Na ₂ O and K ₂ O. It is preferable to use at least one kind.

  However, since tin oxide is a component that makes glass easily devitrified, its content is preferably 0.01 to 0.5% in order to prevent devitrification while enhancing clarity. It is more preferably 0.05 to 0.3%, and further preferably 0.1 to 0.2%.

  Moreover, since iron oxide is a component that colors glass, the content is preferably 0.05 to 0.2% in order to obtain a suitable transmittance as a display device while enhancing clarity. It is more preferably 0.05 to 0.15%, and further preferably 0.05 to 0.10%.

  The content of cerium oxide is preferably 0 to 1.2%, more preferably 0.01 to 1.2%, still more preferably 0.05 to 1.0%, It is especially preferable that it is 0.3 to 1.0%.

  The glass constituting the glass substrate of the present invention contains, in addition to the above components, other components such as zinc and phosphorus up to 0.5% in total for the purpose of adjusting physical properties. can do.

On the other hand, SO ₃ originating from sulfate and the like is also a component accompanied by a valence change in the molten glass and causes a reaction of SO ₃ → SO ₂ + 1 / 2O _{2 in} the molten glass, but after releasing oxygen The remaining SO ₂ has a very low solubility in the glass melt having a low basicity. Therefore, the SO ₂ contained in the glass melt after clarification is not subject to slight temperature changes or contact with the tank wall. It can be gasified with a slight stimulus and become a source of new bubbles. Accordingly, in the glass substrate of the present invention, it is preferable to limit to not include SO ₃ and SO ₂ substantially in the glass. In particular, when SnO ₂ is used as an oxide of a metal whose valence fluctuates in molten glass and a glass substrate is produced from the molten glass by a continuous production method, bubbles containing a large amount of SO ₂ tend to be generated in the glass. This is because SnO ₂ releases O ₂ in the refining process to produce SnO, and this SnO acts as a strong reducing agent in the process of cooling the glass melt to a temperature suitable for molding, so that SO ₃ in the glass is absorbed. Presumably due to reduction to SO ₂ . The bubbles generated at this time are not removed from the glass melt because the viscosity of the glass melt is not low enough to float the bubbles, and are likely to remain in the glass substrate. Therefore, the glass constituting the glass substrate of the present invention, it is preferable to limit to not include SO ₃ and SO ₂ in except glass case containing as impurities, even at the time of glass making, SO ₃ from raw batch It is preferable to remove the sulfate that is the source of SO ₂ . Specifically, the sulfur oxide content in the glass constituting the glass substrate is preferably less than 0.010% in terms of SO ₃ , more preferably 0.005% or less, and 0.003 More preferably, it is% or less.

Further, As ₂ O ₃ , Sb ₂ O ₃ and PbO are substances having an effect of causing a reaction accompanied by valence fluctuation in the molten glass and clarifying the glass, but these are substances having a large environmental load. Therefore, in the glass substrate of the present invention, the glass is restricted so as not to substantially contain As ₂ O ₃ , Sb ₂ O ₃ and PbO. In the present specification, “substantially free of As ₂ O ₃ , Sb ₂ O ₃ and PbO” means that the total content of As ₂ O ₃ , Sb ₂ O ₃ and PbO in the glass is 0.1%. It means the following.

In addition, when glass containing halide ions such as fluoride ions and chloride ions is used to produce a glass substrate from molten glass by a continuous production method, the glass melt contacts a platinum tank or stirrer in a furnace. And cause bubbles. This is presumed to be because halide ions reduce the wettability between glass and platinum, and facilitate the foaming of the aforementioned SO ₂ at the interface between platinum and glass. Therefore, it is preferable that the glass constituting the glass substrate of the present invention is limited so as not to contain halide ions in the glass except when it is contained as an impurity. Is preferably removed. Specifically, the total amount of halide ions in the glass constituting the glass substrate is preferably less than 0.05%, more preferably 0.03% or less, and 0.01% or less. More preferably.

Glass for the glass substrate of the present invention preferably has a density of 2.49 g / cm ³ or less, more preferably 2.46 g / cm ³ or less, 2.43 g / cm ³ or less Is more preferable.

Further, the glass constituting the glass substrate of the present invention preferably has a linear thermal expansion coefficient from 50 ° C. to 300 ° C. of 28 × 10 ^{−7 to} 39 × 10 ⁻⁷ / ° C., and 28 × 10 ⁻⁷ to It is more preferably 37 × 10 ⁻⁷ / ° C., and further preferably 30 × 10 ^{−7 to} 35 × 10 ⁻⁷ / ° C.

  The glass substrate of the present invention, for example, weighs and prepares glass raw materials corresponding to the above components, supplies them to a platinum alloy melting vessel, heats and melts them, then clarifies and homogenizes the glass having a desired composition. It can be obtained by manufacturing and then processing into a thin plate using a method such as a downdraw method, a float method, a fusion method, or a rollout method.

  Next, the display device of the present invention will be described.

The display device of the present invention has the glass substrate for a display device of the present invention.
Examples of the display device include a liquid crystal display device (LCD), such as a liquid crystal display device (LCD), an electroluminescence display device (ELD), and a field emission display device (FED).

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Examples 1 to 19 and Comparative Examples 1 and 2 (Batch type glass substrate production example)
1. Preparation of glass First, refined cinnabar, boron oxide, alumina, basic, which are ordinary industrial glass raw materials so as to have the glass compositions of Examples 1 to 19 and Comparative Examples 1 and 2 shown in Table 1 and Table 2. Glass raw material batches (hereinafter referred to as batches) were respectively prepared using magnesium carbonate, calcium carbonate, strontium nitrate and barium nitrate, potassium carbonate, sodium carbonate, and lithium carbonate. In Comparative Example 2, ammonium chloride was used as the Cl raw material, and dihydrate gypsum was used as the SO ₃ raw material.

  The blended batches were melted and clarified in platinum crucibles, respectively. First, this crucible is held in an electric furnace set at 1550 ° C. for 2 hours to roughly dissolve the raw materials, and then the crucible is transferred to an electric furnace set at 1620 ° C., and the glass melt is clarified by raising the temperature. did. The crucible was taken out of the furnace and allowed to cool and solidify at room temperature to obtain each glass body. These glass bodies were taken out from the crucible and subjected to a slow cooling operation. The slow cooling operation was performed by holding the glass body in another electric furnace set at 800 ° C. for 30 minutes, and then turning off the electric furnace and cooling to room temperature. The glass body that had undergone this slow cooling operation was used as a sample glass.

Tables 1 and 2 show the results of measuring the density, the thermal expansion coefficient, the glass transition point, and the number of bubbles in each of the obtained sample glasses. In addition, a thermal expansion coefficient, a glass transition point, and the number of bubbles are measured with the following method.
(Measurement of thermal expansion coefficient and glass transition point)
Each glass sample is subjected to a normal glass processing technique to produce cylindrical glass specimens having a diameter of 5 mm and a length of 18 mm, and using a differential thermal dilatometer (Thermoflex TMA8140, manufactured by Rigaku Corporation) The thermal expansion coefficient from 50 ° C. to 300 ° C. and the glass transition point were measured.
(Measurement of number of bubbles (evaluation of clarity))
Each sample glass was observed with a 20 × optical microscope, and the number of remaining bubbles was counted. However, the foam in the portion that contacts the crucible side was excluded from the count.
Since each sample glass is obtained by a simple melting process using a crucible, there is a part that differs from the state of bubbles generated in the actual production line, but as an indicator of clarity It can be used sufficiently.

2. Production of Glass Substrate Each of the above sample glasses was processed into a thin plate having a thickness of 0.6 mm by a downdraw method to obtain a glass substrate for each display device.

From Table 1 and Table 2, the glass constituting the glass substrate obtained in Example 1-19, the density is as small as ^{2.37g / cm 3 ~2.47g / cm 3} , a display apparatus for a glass substrate for the resulting It can be seen that the weight can be reduced. The thermal expansion coefficient of the glass be 32.4 × ^{10 -7} /℃~36.0×10 ^-7 / ℃ with low and hardly cause damage when heat-treating the glass substrate, a display device with a high yield It can be seen that it can be manufactured. Furthermore, it can be seen that the environmental load was reduced because As ₂ O ₃ , Sb ₂ O ₃ and PbO were not included in the glass constituting the substrate.

In addition, from Tables 1 and 2, the glass constituting the glass substrates obtained in Examples 1 to 19 contains 0.20 to 1.40% in total of Li ₂ O, Na ₂ O and K ₂ O. And at least one selected from tin oxide (SnO ₂ ), iron oxide (Fe ₂ O ₃ ), and cerium oxide (CeO ₂ ) as an oxide of a metal whose valence fluctuates in molten glass. The number of bubbles in the glass is 0.7 / cm ^{3 to} 4.9 / cm ³ .

On the other hand, the glass obtained in Comparative Example 1 does not contain Li ₂ O, Na ₂ O, and K ₂ O, and the number of bubbles is 7.9 / cm ³ . In particular, the glasses obtained in Examples 1 and ₂ have almost the same basic composition other than the content of K ₂ O in relation to the glass obtained in Comparative Example 1, but the number of bubbles is 0.00. Since it is 7 pieces / cm ^{3 to} 1.4 pieces / cm ³ , the glass obtained in Examples 1 and 2 is superior in clarity to the glass obtained in Comparative Example 1. I understand.

The glass obtained in Comparative Example 2 contains 0.30% tin oxide (SnO ₂ ) and 0.05% iron oxide (Fe ₂ O ₃ ), but Li ₂ O, Na ₂ O and K _2. The total content of O is 0.18%, and further contains 0.49% of chloride ions (Cl) and 0.30% of SO _3, and the number of bubbles is 6.3. / Cm ³ . When the glass obtained in Examples 1 to 19 and the glass obtained in Comparative Example 2 are compared, the number of bubbles in the glasses obtained in Examples 1 to 19 is 0.7 / cm ³ to 4. Since it is 9 pieces / cm ³ , it can be seen that the glass obtained in Comparative Example 2 is superior in clarity.

Example 20 to Example 22 (Example of manufacturing glass substrate by continuous method)
The glass raw materials prepared so as to have the composition shown in Table 3 were melted at 1580 ° C. using a continuous melting apparatus equipped with a refractory brick melting tank and a platinum adjustment tank, clarified at 1650 ° C., and 1500 ° C. After stirring, it was processed into a thin plate having a thickness of 0.6 mm by a downdraw method to obtain a glass substrate for each display device. In the preparation of the raw materials, refined industrial raw materials with low sulfur content and chlorine content are used and replaced with calcium carbonate. In Example 21, dihydrate gypsum is added. In Example 22, the amount of SO ₃ is added by adding calcium chloride. The amount of Cl was adjusted. SO ₃ and Cl were quantified by dissolving the produced glass substrate with hydrofluoric acid and chemically separating SO ₃ and Cl from other components.

  Table 3 shows the results obtained by measuring the number of bubbles in the same manner as in Examples 1 to 19 for each glass.

From Table 3, the glass constituting the glass substrate obtained in Example 20 has a bubble count of 24 × 10 ⁻⁶ / cm ³ , which is sufficient for large substrates of the seventh generation (1870 × 2200 mm) and later. High foam quality applicable to the achieved. Moreover, the glass which comprises the glass substrate obtained in Example 21 and Example 22 contains 0.010% of SO ₃ (Example 21), or 0.05% of Cl (Example 22). Although the number of bubbles is 120 × 10 ⁻⁶ pieces / cm ^{3 to} 720 × 10 ⁻⁶ pieces / cm ³ , it can be sufficiently put into practical use as a large glass before the sixth generation (1500 × 1850 mm). Met.

  When a liquid crystal display module was actually produced using the glass substrate obtained in Example 20 and tested, no problems occurred as compared with a module using conventional alkali-free glass. It was confirmed that the glass substrate of the invention can be used as an alternative to the conventional alkali-free glass.

  Since the glass substrate for a display device of the present invention is lightweight and has high clarity while reducing environmental load, it can be suitably used for a display device such as a TFT-LCD.

Claims (15)

In mass% display,
SiO ₂ 50~70%,
B ₂ O ₃ 5~18%,
Al ₂ O ₃ 10-25%,
MgO 0-10%,
CaO 0-20%,
SrO 0-20%,
BaO 0-10%,
RO 5-20%
(Wherein R is at least one selected from Mg, Ca, Sr and Ba),
R ′ ₂ O 0.20% or more and 2.0% or less (where R ′ is at least one selected from Li, Na and K)
Including
A total of 0.05 to 1.5% of metal oxides whose valence fluctuates in the molten glass, the glass contains tin oxide as an essential component as a metal oxide whose valence fluctuates in the molten glass,
A glass substrate for a display device, characterized by being made of glass that does not substantially contain As ₂ O ₃ , Sb ₂ O _3, and PbO, and does not contain halide ions in the glass except when it is contained as an impurity. In mass% display,
SiO ₂ 55~65%,
B ₂ O ₃ 10-14%,
Al ₂ O ₃ 15-19%,
MgO 1-3%,
CaO 4-7%,
SrO 1-4%,
BaO 0-2%,
RO 6-16%
(Wherein R is at least one selected from Mg, Ca, Sr and Ba),
R ′ ₂ O 0.20% or more and 2.0% or less (where R ′ is at least one selected from Li, Na and K)
Including
Including 0.1 to 1.5% in total of oxides of metals whose valence fluctuates in molten glass,
Glass contains tin oxide as an essential component as a metal oxide whose valence fluctuates in molten glass,
_{2. The} glass substrate for a display device according to claim 1 , wherein the glass substrate is made of a glass that does not substantially contain As ₂ O ₃ , Sb ₂ O _3, and PbO and does not contain halide ions in the glass except when contained as impurities. R _'2 O display glass substrate according to claim 1 or claim 2 content is less than 0.5% 0.20% of. R 'includes _{K 2} O as ₂ O, substantially Li ₂ O and Na ₂ O made of glass without the claims 1 to display glass substrate according to claim 3. Display device for a glass substrate according to any one of the iron oxide and made of glass containing at least one selected from cerium oxide claims 1 to 4 as an oxide of a metal of a valence in the molten glass. The glass substrate for a display device according to any one of claims 1 to 5 , wherein the content of tin oxide in the glass is in the range of 0.01 to 0.5%. The glass substrate for a display device according to claim 5 or 6 , wherein the content of iron oxide in the glass is in the range of 0.05 to 0.2%. The glass substrate for a display device according to any one of claims 5 to 7 , wherein the content of cerium oxide in the glass is in the range of 0 to 1.2%. Display device for a glass substrate according to any one of content SO ₃ according to claim 1, translated at is limited to less than 0 wt% to 0.010% by weight to claim 8 of the sulfur oxides in the glass. Display device for a glass substrate according to any one of claims 1 to 9 in which the content of the halide ions in the glass is limited to less than 0 wt% to 0.05 wt% in total. Display device for a glass substrate according to any one of claims 1 to 10 in which the density is made of glass is 2.49 g / cm ³ or less. Display device for a glass substrate according to any one of claims 1 to 11, linear thermal expansion coefficient of from 50 ° C. to 300 ° C. is made of glass is ^{28 × 10 -7 ~39 × 10 -7} / ℃. Display device characterized by having a glass substrate for a display device according to any one of claims 1 to 12. The display device according to claim 13 , wherein the display device is a liquid crystal display device. A glass raw material batch is melted and refined to produce a glass, and the obtained glass is processed into a thin plate to produce the glass substrate for a display device according to any one of claims 1 to 12. The manufacturing method of the glass substrate for display apparatuses.