JP4288657B2 - 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, and Al, Ag, Ni, etc. are formed on the rear glass substrate surface. After a partition is formed on the surface of the back glass substrate on which the electrode made of 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 higher). Those molded to a thickness of 8 to 3.0 mm are used.
[0004]
The high strain point glass has a higher strain point and volume resistivity than soda lime glass, so that the thermal deformation and thermal shrinkage of the glass substrate are small in the heat treatment process, and the front glass substrate and the back glass substrate are opposed to each other. At this time, the electrodes can be accurately aligned. In addition, 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 the ITO film or Nesa film is small, and the electrical resistance value of the electrode material can be stabilized. For these reasons, high strain point glass is now widely used as a glass substrate rather than soda-lime glass.
[0005]
However, since the glass substrate made of soda-lime glass or high strain point glass has a large thermal expansion coefficient of about 84 × 10 ⁻⁷ / ° C., heat treatment is performed at a temperature of 500 to 600 ° C. and then rapidly cooled. Cracks due to stress occur. For this reason, the cooling rate of the heat treatment process is limited, the time required for the process becomes long, and the productivity is lowered. Therefore, in order to improve productivity, a glass substrate excellent in thermal shock resistance that is difficult to break even when rapidly cooled is desired.
[0006]
Therefore, a glass substrate has been proposed in which the thermal expansion coefficient of the glass is reduced within a range in which consistency with peripheral materials such as a dielectric, a partition, and a frit can be obtained. (Patent Documents 1 to 3)
[0007]
[Patent Document 1]
JP 2001-226138 A [Patent Document 2]
JP-A-11-314933 [Patent Document 3]
JP 2002-193635 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.
[0009]
Moreover, since the glass currently disclosed by patent document 2, 3 has high 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.
[0010]
An object of the present invention is to provide a glass substrate for a flat panel display device comprising a high strain point glass that is easy to melt and mold, has excellent thermal shock resistance, and has a thermal expansion coefficient that is easy to match with surrounding materials. It is to be.
[0011]
[Means for Solving the Problems]
A glass substrate for a flat panel display device of the present invention, by mass _{percentage, SiO 2 55~74%, Al 2} O 3 0.5~4%, 1~15% MgO, CaO 0~8%, SrO 1~15 %, BaO 0~5%, RO ( RO represents MgO, CaO, SrO, and _{BaO) 21.6 ~27%, Na 2} O 0~8%, K 2 O 2~12%, ZrO 2 0~7 _%, containing a composition of P ₂ O 5 0 to 0.5%, the value of RO / _Al 2 _{O 3} is Ri der 6.5 or more and a thermal expansion coefficient at 30 to 380 ° C. is 65 to 74 × 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 1170 ° C. or lower .
[0012]
[Action]
Since the glass substrate for a flat panel display device of the present invention has a thermal expansion coefficient of glass set to 74 × 10 ⁻⁷ / ° C. or less, the thermal shock resistance can be improved, and the glass substrate in the heat treatment step can be improved. Generation of cracks can be suppressed. If the thermal expansion coefficient is lower than 65 × 10 ⁻⁷ / ° C., it is difficult to obtain consistency with the thermal expansion coefficient of the peripheral material.
[0013]
In order to reduce the thermal expansion coefficient, it can be adjusted by increasing SiO ₂ or Al ₂ O ₃ in the glass or decreasing Na ₂ O or K ₂ O. However, if SiO ₂ and Al ₂ O ₃ are increased or Na ₂ O and K ₂ O are decreased, the high-temperature viscosity of the glass becomes high and melting and molding become difficult.
[0014]
Therefore, the glass substrate for a flat panel display device of the present invention is a component that suppresses the content of Al ₂ O _{3 in} the glass to 4% by mass or less and lowers the high temperature viscosity of the glass to improve the meltability and formability. The content of RO (RO represents MgO, CaO, SrO, BaO) is 15% by mass or more, and the value of RO / Al ₂ O ₃ is limited to 6.5 or more. By doing in this way, the thermal expansion coefficient and high temperature viscosity of glass become low, As a result, high thermal shock resistance and the outstanding meltability and moldability can be obtained simultaneously.
[0015]
Further, it is desirable that the temperature of the glass melt corresponding to a viscosity of 10 ⁴ dPa is 1170 ° C. or lower (preferably 1150 ° C. or lower). When this temperature is higher than 1170 ° C., a burden is imposed on the molding apparatus.
[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]
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.
[0018]
SiO ₂ is a glass network former. When the content of SiO ₂ increases, the high temperature viscosity of the glass increases, and melting and molding become difficult, and the coefficient of thermal expansion becomes too small to make it compatible with the surrounding materials. In addition, when the content decreases, the thermal expansion coefficient increases and the thermal shock resistance of the glass tends to decrease, or the strain point of the glass tends to decrease. Cracks occur, and thermal deformation and shrinkage are likely to occur. If the content is 55 to 74%, it is possible to obtain a glass having a thermal expansion coefficient matching with the surrounding material and excellent in thermal shock resistance without deteriorating the meltability and moldability of the glass. A preferable range is 56 to 70%, more preferably 58 to 70%.
[0019]
Al ₂ O ₃ is a component that increases the strain point of glass. When the content of Al ₂ O ₃ increases, the high-temperature viscosity of the glass increases and melting and molding become difficult, and the thermal expansion coefficient decreases, making it difficult to achieve consistency with surrounding materials. In addition, when the content decreases, the thermal expansion coefficient increases and the thermal shock resistance of the glass tends to decrease, or the strain point of the glass tends to decrease. Cracks occur, and thermal deformation and shrinkage are likely to occur. If the content is 0.5 to 4%, it is possible to obtain a glass having a thermal expansion coefficient matching with the surrounding material and having excellent thermal shock resistance without deteriorating the meltability and moldability of the glass. . A preferable range is 0.5 to 3.8%, more preferably 0.5 to 3.5%.
[0020]
MgO is a component that remarkably lowers the high-temperature viscosity of glass and improves meltability and formability. When the content of MgO increases, the glass tends to devitrify. Further, when the content is reduced, it is difficult to obtain the effect. If the content is 1 to 15%, the high-temperature viscosity can be lowered without increasing the devitrification property of the glass, and the meltability and moldability can be improved. A preferable range is 2 to 13%, and more preferably 3 to 12%.
[0021]
CaO is a component that lowers the high-temperature viscosity of the glass and improves the meltability and moldability. When the content of CaO increases, the glass becomes extremely devitrified. If the content is 8% or less, the high-temperature viscosity can be lowered and the meltability and moldability can be improved without increasing the devitrification property of the glass. The preferred range is 1-8%, more preferably 1-7%.
[0022]
SrO is a component that lowers the high-temperature viscosity of the glass to improve the meltability and formability, and increase the volume resistivity. When the SrO content increases, the glass tends to devitrify. Further, when the content is reduced, it is difficult to obtain the effect. If the content is 1 to 15%, the high-temperature viscosity can be lowered without increasing the devitrification property of the glass, and the meltability and moldability can be improved. A preferable range is 3 to 15%, and more preferably 4 to 15%.
[0023]
BaO, like SrO, is a component that lowers the high-temperature viscosity of glass to increase meltability and formability, or increase volume electrical resistivity. When the content of BaO increases, the glass tends to devitrify. When the content is 5% or less, the high-temperature viscosity can be lowered without increasing the devitrification property of the glass, and the meltability and moldability can be improved. A preferable range is 4% or less, and more preferably 3%.
[0024]
In order to improve the meltability and formability by reducing the high temperature viscosity of the glass without increasing the devitrification property of the glass, RO, which is the total amount of MgO, CaO, SrO and BaO, is used . It should be 6-27%. When the content of RO increases, the glass tends to devitrify. Moreover, when content decreases, the high temperature viscosity of glass will rise and it will become difficult to fuse | melt and shape | mold .
[0025]
In order to simultaneously improve the thermal shock resistance, meltability and formability of the substrate glass, the value of RO / Al ₂ O ₃ is 6.5 or more (preferably 7.0 or more, more preferably 7.5 or more. ) Must be restricted. When this value is lowered, the high temperature viscosity of the glass increases, and melting and molding become difficult. If this value becomes too large, the strain point may be lowered. Therefore, the upper limit of this value is desirably 35.
[0026]
Na ₂ O is a component that increases the meltability and moldability by controlling the thermal expansion coefficient of the glass or lowering the high temperature viscosity of the glass. When the content of Na ₂ O increases, the thermal expansion coefficient increases and the thermal shock resistance of the glass decreases. Moreover, it exists in the tendency for the strain point of glass to fall. For this reason, the glass substrate is easily cracked or thermally deformed or contracted easily in the thermal process for manufacturing the plasma display device. If the content is 8% or less, it is possible to obtain a glass having a thermal expansion coefficient matching with the surrounding material and excellent in thermal shock resistance without lowering the strain point. A preferable range is 6% or less, and more preferably 5% or less.
[0027]
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 improve meltability and formability. When the content of K ₂ O increases, the thermal expansion coefficient increases and the thermal shock resistance of the glass decreases. Moreover, it exists in the tendency for the strain point of glass to fall. For this reason, the glass substrate is easily cracked or thermally deformed or contracted easily in the thermal process for manufacturing the plasma display device. On the other hand, when the content is reduced, the thermal expansion coefficient of the glass is reduced and it is difficult to match the thermal expansion coefficient of the surrounding material. In addition, the high temperature viscosity of the glass tends to increase, making melting and molding difficult. If the content is 2 to 12%, it is possible to obtain a glass having a thermal expansion coefficient matching with the surrounding material and excellent in thermal shock resistance without lowering the strain point. A preferable range is 3 to 10%, more preferably 4 to 10%.
[0028]
ZrO ₂ is a component that increases the strain point of glass. If the content of ZrO ₂ increases, devitrification will tend to occur and molding becomes difficult. If the content is 7% or less, the strain point of the glass can be increased without adversely affecting other properties. A preferable range is 6% or less, and more preferably 5% or less.
[0029]
P ₂ O ₅ is a component that suppresses devitrification of the glass. When the content of P ₂ O ₅ increases, the glass becomes milky. If content is 0.5% or less, the effect which suppresses devitrification of glass can be acquired, without whitening glass. The preferred range is 0.4% or less, more preferably not contained.
[0030]
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 in the float bath to become metal foreign matter, so introduction should be avoided.
[0031]
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.
[0032]
Next, a method for producing a glass substrate for a flat panel display device of the present invention will be described.
[0033]
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 using a forming 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.
[0034]
【Example】
Hereinafter, the present invention will be described based on examples.
[0035]
Tables 1 and 2 show examples (samples Nos. 1 to 5 ) and comparative examples (samples Nos. 6 and 7 ) of the present invention.
[0036]
[Table 1]
[0038]
Each sample in the table was prepared as follows.
[0039]
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, formed into a plate shape, slowly cooled, then polished on both sides 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.
[0040]
With respect to each sample thus obtained, the coefficient of thermal expansion, density, volume resistivity, strain point, and temperature of the glass melt corresponding to a viscosity of 10 ⁴ dPa were measured and shown in the table.
[0041]
As can be seen from the table, the sample No. Each of the samples 1 to 5 had a thermal expansion coefficient of 70 to 74 × 10 ⁻⁷ / ° C., and thus had excellent thermal shock resistance and had a thermal expansion coefficient that matched well with the surrounding materials. . Moreover, it turned out that the temperature of the glass melt equivalent to 10 < ⁴ > dPa * s is as low as 1170 degrees C or less, and is excellent in a moldability. Further, the density was 2.66 g / cm ³ or less. Furthermore, the strain point is 580 ° 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) at 150 ° C. was 12.4 Ω · cm or more.
[0042]
On the other hand, sample No. which is a comparative example. No. 6 has a glass melt temperature corresponding to 10 ⁴ dPa · s of 1150 ° C. and excellent moldability, but has a thermal expansion coefficient of 83 × 10 ⁻⁷ / ° C. and low thermal shock resistance. Sample No. No. 7 has a thermal expansion coefficient of 70 × 10 ⁻⁷ / ° C. and excellent thermal shock resistance, but the glass melt temperature corresponding to 10 ⁴ dPa · s is as high as 1220 ° C. and the moldability is poor. Guessed.
[0043]
In addition, about the thermal expansion coefficient, the cylindrical sample of diameter 3.5mm and length 50mm was produced, and the average thermal expansion coefficient in 30-380 degreeC was measured with the 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 invention's effect】
As described above, the glass substrate of the present invention has a high strain point and volume electrical resistance, is excellent in thermal shock resistance and moldability, and has a thermal expansion coefficient that can be consistent with the surrounding materials. In particular, it is suitable as a glass substrate of a plasma display device.

Claims (1)

By mass _{percentage, SiO 2 55~74%, Al 2} O 3 0.5~4%, 1~15% MgO, CaO 0~8%, SrO 1~15%, BaO 0~5%, RO (RO is MgO, CaO, SrO, BaO) 21.6 to 27%, Na ₂ O 0 to 8%, K ₂ O 2 to 12%, ZrO ₂ 0 to 7%, P ₂ O ₅ 0 to 0.5% containing composition, der value 6.5 or more RO / _Al 2 _{O 3} is, and the thermal expansion coefficient at 30 to 380 ° C. is 65~74 × ^{10 -7} / ℃, strain point 580 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 1170 ° C. or lower .