JP4320772B2 - Glass substrate for flat panel display - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a glass substrate suitable for a flat panel display device, particularly a plasma display device.
[0002]
[Prior art]
In the plasma display device, a transparent electrode made of an ITO film, a nesa film, or the like is formed on the front glass substrate surface, and a dielectric layer is formed on the transparent electrode. On the rear glass substrate surface, Al, Ag, and Ni are formed. After a partition is formed on the surface of the back glass substrate on which the electrode to be formed is formed, a circuit is formed by firing at a temperature of about 500 to 600 ° C., respectively. Thereafter, the front glass substrate and the rear glass substrate are opposed to each other to align the electrodes and the like, and the periphery is frit-sealed at a temperature of about 500 to 600 ° C.
[0003]
In general, the glass substrate is made of soda-lime glass having a thermal expansion coefficient of about 84 × 10 ⁻⁷ / ° C. or high strain point glass (glass having a strain point of 570 ° C. or more), and includes a float method, a roll-out method, and the like. The one formed to a thickness of 1.8 to 3.0 mm is used.
[0004]
By the way, soda-lime glass has been conventionally used as the glass substrate, but at present, high strain point glass is widely used.
[0005]
The reason for this is that high strain point glass has higher strain point and volume resistivity than soda lime glass, so that heat treatment and thermal shrinkage of the glass substrate are small in the heat treatment process, and the front glass substrate and the back glass substrate. The electrode material can be aligned with high accuracy when facing each other, and the mobility of the alkali component in the glass is small, the reaction between the alkali component in the glass and the thin film electrode such as ITO film or Nesa film is small, and the electrode material This is because the electrical resistance value can be stabilized.
[0006]
However, the above-described high strain point glass is more susceptible to cracking in the manufacturing process than soda lime glass. Therefore, the yield of the apparatus is low, which is one of the causes that hinder productivity improvement. Therefore, it is necessary to make the glass substrate difficult to break in order to improve productivity. That is, a glass substrate having high crack resistance and excellent crack resistance is desired.
[0007]
Thus, a high strain point glass composition having excellent crack resistance has been disclosed. (Patent Documents 1 to 4)
[0008]
[Patent Document 1]
JP 2001-226138 A [Patent Document 2]
JP 2001-247332 A [Patent Document 3]
JP-A-2002-193635 [Patent Document 4]
JP 2002-293567 A
[Problems to be solved by the invention]
However, since the glass disclosed in Patent Document 1 requires P ₂ O ₅ , there is a possibility that the glass may become milky due to slight fluctuations in melting conditions and molding conditions, which causes a reduction in production yield. . In particular, in the case of float forming, P ₂ O ₅ may be reduced and the glass may be colored.
[0010]
Moreover, since the glass currently disclosed by patent document 2 has the high-temperature viscosity of glass, it has to make the melting temperature and shaping | molding temperature of glass high, and melting and shaping | molding are difficult. In particular, in the case of float forming, if the high-temperature viscosity of the glass is high, the temperature of the float bath for forming the molten glass into a plate shape must be increased, and the volatilization amount of tin from the float bath increases. It will adversely affect the surface.
[0011]
Since the glass disclosed in Patent Documents 3 and 4 has a low coefficient of thermal expansion of 75 × 10 ⁻⁷ / ° C. or less, in the current manufacturing process, consistency with surrounding materials cannot be obtained, and the glass substrate has When the peripheral material is formed, there is a risk of peeling or cracking.
[0012]
An object of the present invention is a glass substrate for a flat panel display device comprising a high strain point glass which is easily melted and molded, and has a thermal expansion coefficient which is easy to match with surrounding materials and has excellent crack resistance. Is to provide.
[0013]
[Means for Solving the Problems]
A glass substrate for a flat panel display device of the present invention, by mass _{percentage, SiO 2 55~70%, Al 2} O 3 3~8%, 8~15% MgO, CaO 1~8%, SrO 5~10%, BaO 0 to 5%, RO (RO represents MgO, CaO, SrO, BaO) 14 to less than 19.5%, Na ₂ O 0 to 8%, K ₂ O 12.6 to 17%, ZrO ₂ 0 It contains 5% composition, does not contain P ₂ O _5, has a value of RO / Al ₂ O ₃ of 1.7 or more, and a thermal expansion coefficient at 30 to 380 ° C. of 81 to 90 × 10 ^−7. / ° C, the strain point is 580 ° C or higher, and the temperature of the glass melt corresponding to a viscosity of 10 ⁴ dPa is 1200 ° C or lower.
[0014]
[Action]
In order to increase the crack resistance of the glass substrate, the content of RO in the glass is decreased to increase the crack resistance of the glass. However, when the RO content decreases, the high temperature viscosity of the glass increases, and melting and molding become difficult.
[0015]
Therefore, the glass substrate for a flat panel display device of the present invention suppresses the content of RO in the glass to less than 19.5% by mass, suppresses the content of Al ₂ O ₃ to 8% by mass or less, and RO. The value of / Al ₂ O ₃ is limited to 1.7 or more. By doing in this way, the temperature of the glass melt corresponding to the viscosity of 600 mN or more and 10 ⁴ dPa can be reduced to 1200 ° C. or less, and a glass excellent in crack resistance, meltability and formability can be obtained. it can. In addition, in order to obtain the glass which has the outstanding crack resistance, it is desirable to make crack resistance 600 mN or more. If it is smaller than 600 mN, cracks are likely to occur in the conveyance and manufacturing process, and cracks are likely to occur. In order to obtain a glass having excellent formability, the temperature of the glass melt corresponding to a viscosity of 10 ⁴ dPa is preferably 1200 ° C. or lower (preferably 1195 ° C.). When this temperature is higher than 1200 ° C., a burden is imposed on the molded body.
[0016]
Further, since the glass substrate for a flat panel display device of the present invention has a glass strain point set to 580 ° C. or higher, the glass substrate is subjected to thermal deformation and thermal shrinkage in the heat treatment process when manufacturing the plasma display device. Can be suppressed.
[0017]
Furthermore, since the thermal expansion coefficient is set to 81 to 90 × 10 ⁻⁷ / ° C., consistency with the thermal expansion coefficient of the surrounding material can be obtained.
[0018]
The reason why the ratio of each component is limited as described above in the glass substrate of the present invention will be described below.
[0019]
SiO ₂ is a glass network former. When the content is 55 to 70%, a glass substrate having a high strain point and small thermal shrinkage and thermal deformation is easily obtained. A preferable range is 56 to 70%, more preferably 58 to 63.5%. When the content of SiO ₂ is increased, the coefficient of thermal expansion is reduced, and consistency with the surrounding materials cannot be obtained, or the high temperature viscosity of the glass is increased, so that melting and molding become difficult. Further, when the content is reduced, the coefficient of thermal expansion is increased and the consistency with the surrounding materials cannot be obtained, or the strain point of the glass is lowered, and thermal deformation and thermal contraction are likely to occur.
[0020]
Al ₂ O ₃ is a component that increases the strain point of glass. When the content is 3 to 8%, the high-temperature viscosity of the glass can be kept low, and a glass substrate having a high strain point and small thermal shrinkage and thermal deformation is easily obtained. A preferred range is 3-7%, more preferably 4-7%. In addition, when the content of Al ₂ O ₃ increases, the high temperature viscosity of the glass increases, and melting and molding become difficult. Further, when the content is reduced, the strain point of the glass is lowered and thermal deformation and thermal shrinkage are likely to occur.
[0021]
MgO is a component that remarkably lowers the high-temperature viscosity of glass and improves meltability and formability. If content is 8 to 15%, the high temperature viscosity of glass can be made low, without reducing the crack resistance of glass. A preferable range is 8 to 13%, and more preferably 8 to 11%. In addition, when the content of MgO increases, the glass tends to devitrify. Further, when the content is reduced, it is difficult to obtain the effect.
[0022]
CaO is a component that lowers the high-temperature viscosity of the glass and improves the meltability and moldability. If content is 8% or less, the high temperature viscosity of glass can be made low, without reducing the crack resistance of glass. The preferred range is 1-7%, more preferably 1-6%. In addition, when content of CaO increases, there exists a tendency for the crack resistance of glass to fall remarkably, and it becomes easy to generate | occur | produce a crack.
[0023]
SrO is a component that lowers the high-temperature viscosity of the glass to increase the meltability and formability of the glass, and increase the volume resistivity. If content is 5 to 10%, the high temperature viscosity of glass can be made low, without reducing the crack resistance of glass. A preferable range is 6 to 13%, and more preferably 6 to 11%. In addition, when content of SrO increases, it exists in the tendency for the crack resistance of glass to fall, and it becomes easy to generate | occur | produce a crack. Further, when the content is reduced, it is difficult to obtain the effect.
[0024]
BaO, like SrO, is a component that lowers the high-temperature viscosity of the glass to increase the meltability and formability of the glass, and increase the volume electrical resistivity. If content is 5% or less, the high temperature viscosity of glass can be made low, without reducing the crack resistance of glass. A preferable range is 4% or less, and more preferably 3%. In addition, when content of BaO increases, it exists in the tendency for the crack resistance of glass to fall, and it becomes easy to generate | occur | produce a crack.
[0025]
In addition, in order to suppress the fall of the crack resistance of glass, it is necessary to make RO which is the total amount of MgO, CaO, SrO, and BaO into 14 to less than 19.5%. A preferable range is 14 to 19%, and more preferably 14 to 18%. When the content of RO increases, the crack resistance of the glass tends to decrease, and cracking tends to occur. Moreover, when RO content decreases, the high temperature viscosity of glass will rise and it will become difficult to fuse | melt and shape | mold.
[0026]
Further, in order to prevent an increase in the high temperature viscosity of the glass accompanying a decrease in the RO content, it is necessary to limit the value of RO / Al ₂ O ₃ to 1.7 or more. A preferable range is 2.0 or more. In addition, when this value becomes low, the high temperature viscosity of glass will rise and it will become difficult to fuse | melt and shape | mold.
[0027]
Na ₂ O is a component that increases the meltability and moldability of the glass by controlling the thermal expansion coefficient of the glass or lowering the high temperature viscosity of the glass. If the content is 8% or less, a glass having a low coefficient of thermal expansion and a high temperature viscosity matching with the surrounding materials can be obtained. A preferable range is 6% or less, and more preferably 5% or less. In addition, when the content of Na ₂ O increases, the thermal expansion coefficient of the glass increases, and it becomes difficult to obtain a thermal expansion coefficient consistent with the surrounding materials, or the strain point of the glass tends to decrease. Thermal deformation and thermal shrinkage are likely to occur during the thermal process.
[0028]
K ₂ O is a component that controls the coefficient of thermal expansion of glass in the same manner as Na ₂ O, or lowers the high-temperature viscosity of glass to increase the meltability and formability of glass. If the content is 12.6 to 17%, a glass having a low coefficient of thermal expansion and high temperature viscosity that matches the surrounding material can be obtained . In addition , when the content of K ₂ O increases, the thermal expansion coefficient of the glass increases, and it becomes difficult to obtain a thermal expansion coefficient that is consistent with the surrounding materials, or the strain point of the glass tends to decrease. Thermal deformation and thermal shrinkage are likely to occur during the thermal process. Further, when the content is reduced, the thermal expansion coefficient of the glass becomes small, and it becomes difficult to obtain a thermal expansion coefficient that matches the surrounding material, or the high temperature viscosity of the glass tends to increase, so that melting and molding become difficult.
[0029]
ZrO ₂ is a component that increases the strain point of glass. If the content is 5% or less, the strain point of the glass can be increased without adversely affecting other properties. A preferable range is 4% or less, and more preferably 3% or less. If the content of ZrO ₂ increases, devitrification will tend to occur and molding becomes difficult.
[0030]
P ₂ O ₅ is a component that raises the crack resistance of the glass and suppresses the occurrence of cracking, but should also be contained because it is also a component that opacifies the glass.
[0031]
In the present invention, in addition to the above components, in order to prevent ultraviolet coloration, the TiO ₂ up to 3%, in order to reduce the liquidus temperature, to improve the moldability, Y ₂ O _3, La ₂ O ₃ , Nb ₂ O _{3 up} to 3% each, as a colorant, Fe ₂ O ₃ , CoO, NiO, Cr ₂ O ₃ , Nd ₂ O _{3 up} to 2% each, as a fining agent, As ₂ O ₃ , Sb ₂ O ₃ , SO ₃ , F, Cl, etc. can be added up to 1% in total. However, when forming by the float process, As ₂ O ₃ and Sb ₂ O ₃ are reduced, so introduction should be avoided.
[0032]
In the present invention, since B ₂ O ₃ significantly lowers the strain point, the content should be suppressed to less than 2%, and it is desirable not to contain it.
[0033]
Next, a method for producing a glass substrate for a flat panel display device of the present invention will be described.
[0034]
First, a raw material is prepared so that it may become said glass composition range. Subsequently, the prepared raw materials are melted at a temperature of 1520 to 1680 ° C. in a continuous melting furnace. Thereafter, the glass substrate can be obtained by forming the molten glass into a plate shape by a method such as a slot down draw method, an overflow down draw method, a float method, or a roll out method, followed by slow cooling.
[0035]
【Example】
Hereinafter, the present invention will be described based on examples.
[0036]
Table 1 shows examples of the present invention (sample Nos. 1 and 2 ) and comparative examples (samples No. 3 and 4 ).
[0037]
[Table 1]
[0039]
Each sample in the table was prepared as follows.
[0040]
First, the glass raw material was prepared so that it might become the composition of a table | surface, and it melted at 1450-1600 degreeC for 4 hours using the platinum pot. Thereafter, the molten glass is poured onto a carbon plate and formed into a plate shape. After slow cooling, both sides are polished so that the plate thickness becomes 2.8 mm, and the obtained plate glass is cut into a size of 200 mm square. Sample glass was produced by processing.
[0041]
With respect to each sample thus obtained, the coefficient of thermal expansion, density, volume resistivity, strain point, glass melt temperature corresponding to a viscosity of 10 ⁴ dPa, and crack resistance were measured and shown in the table.
[0042]
In addition, about the measurement of a thermal expansion coefficient, a density, and crack resistance, it measured using what was heat-processed so that it might not be influenced by a thermal history. In the heat treatment, the sample is heated from room temperature to the strain point of glass + 80 ° C. at a rate of temperature increase of 10 ° C./min, held at that temperature for 1 hour, and then to 500 ° C. at a rate of temperature decrease of 2 ° C./min. Cooling was carried out under the condition of cooling to room temperature at a rate of temperature decrease of 10 ° C./min.
[0043]
Regarding the thermal expansion coefficient, a cylindrical sample having a diameter of 3.5 mm and a length of 50 mm was prepared, and the average thermal expansion coefficient at 30 to 380 ° C. was measured with a dilatometer.
[0044]
The density was measured by the well-known Archimedes method.
[0045]
About volume electrical resistivity, the value in 150 degreeC was measured based on ASTMC657-78.
[0046]
Further, the strain point was measured based on ASTM C336-71. The glass melt temperature corresponding to a glass viscosity of 10 ⁴ dPa · s was measured by a platinum ball pulling method. This temperature serves as a standard for molding glass into a plate shape, and the lower the temperature, the better the moldability.
[0047]
The crack resistance was measured using the method proposed by Wada et al. (M. Wada et al. Proc., The Xth ICG, vol. 11, Ceram. Soc., Japan, Kyoto, 1974, p39). The load when the crack occurrence rate was 50% was determined as “crack resistance”. In this method, a sample glass is placed on the stage of a Vickers hardness tester, and a diamond-shaped diamond indenter is pressed against the surface of the sample glass with various loads for 15 seconds. When the number of cracks generated from the four corners of the indentation is counted by 15 seconds after unloading, the ratio (crack generation rate) to the maximum number of cracks (4) that can be generated is determined, and the crack generation rate is 50% The load was defined as “crack resistance”. A large crack resistance means that cracks are unlikely to occur even under high loads, that is, excellent crack resistance.
[0048]
The crack resistance was measured 20 times with the same load, and the average value was obtained. The measurement conditions were a temperature of 25 ° C. and a humidity of 30%.
[0049]
As can be seen from the table, the sample No. In each of the samples 1 and 2 , the glass melt temperature corresponding to 10 ⁴ dPa · s was as low as 1190 ° C. or less, the crack resistance was 600 mN or more, and the moldability and crack resistance were excellent. The density was 2.56 g / cm ³ or less. Since the thermal expansion coefficient is 81 to 85 × 10 ⁻⁷ / ° C., it can be well matched with the surrounding materials. Furthermore, the strain point is 600 ° C. or higher, and thermal deformation and thermal shrinkage of the glass substrate in the heat treatment step can be suppressed. The volume electrical resistivity (log ρ) was 11.5 Ω · cm or more.
[0050]
On the other hand, sample No. which is a comparative example. No. 3 had a crack resistance of 600 mN, but the glass melt temperature corresponding to 10 ⁴ dPa · s was high at 1240 ° C., and the moldability was poor. Sample No. In No. ⁴ , the temperature of the glass melt corresponding to 10 ⁴ dPa · s was as low as 1150 ° C., but the crack resistance was as low as 470 mN.
[0051]
【The invention's effect】
As described above, the glass substrate of the present invention is suitable as a glass substrate for flat panel display devices, particularly plasma display devices, because it is excellent in crack resistance and moldability and has a high strain point and volumetric electrical resistance.

Claims (2)

By mass _{percentage, SiO 2 55~70%, Al 2} O 3 3~8%, 8~15% MgO, CaO 1~8%, SrO 5~10%, BaO 0~5%, RO (RO is MgO, 14 to less than 19.5%, Na ₂ O 0 to 8%, K ₂ O 12.6 to 17%, ZrO ₂ 0 to 5%, and P ₂ O ₅ , which represents CaO, SrO and BaO) And the value of RO / Al ₂ O ₃ is 1.7 or more, the thermal expansion coefficient at 30 to 380 ° C. is 81 to 90 × 10 ⁻⁷ / ° C., and the strain point is 580 ° C. or more. A glass substrate for a flat panel display device, wherein the temperature of the glass melt corresponding to a viscosity of 10 ⁴ dPa is 1200 ° C. or lower.   2. The glass substrate for a flat panel display device according to claim 1, wherein a crack resistance value is 600 mN or more.