JP2005162536A - Glass substrate for flat panel display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass substrate for a flat panel display device comprising high distortion point glass whose melting and forming are easy, which has excellent crack resistance, and has a coefficient of thermal expansion to make the glass easily consistent with peripheral materials. <P>SOLUTION: The glass substrate for the flat panel display device is, by mass %, over 54 to 70% SiO<SB>2</SB>, 0 to ≤5% Al<SB>2</SB>O<SB>3</SB>, over 7 to 15% MgO, 0 to ≤7% CaO, 0 to 20% SrO, 0 to 20% BaO, over 19 to 25% RO (RO represents MgO, CaO, SrO, and BaO), 0 to 10% Na<SB>2</SB>O, 0 to 15% K<SB>2</SB>O, and 0 to 10% ZrO<SB>2</SB>. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a glass substrate suitable for a flat panel display device, particularly a plasma display device.

  In the plasma display device, a transparent electrode made of an ITO film or a nesa film is formed on the front glass substrate surface, and a dielectric material is applied thereon to form a dielectric layer. By applying a back dielectric material and a partition wall material to the back glass substrate surface on which electrodes made of Al, Ag, Ni, etc. are formed, a partition is formed, and then fired at a temperature of about 500 to 600 ° C., respectively. Form. 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.

Conventionally, as a glass substrate, soda-lime glass (coefficient of thermal expansion of about 84 × 10 ⁻⁷ / ° C.) formed to a thickness of 1.8 to 3.0 mm by a float method or the like has been generally used. In addition, the thermal expansion coefficient of peripheral materials such as insulating paste, rib paste, and frit seal is also adjusted in the range of 70 to 90 × 10 ⁻⁷ / ° C. in accordance with soda lime glass.

  However, since soda-lime glass has a strain point as low as about 500 ° C., when heat-treated at a temperature of 570 to 600 ° C., thermal deformation and thermal shrinkage occur, and the dimensions change remarkably. As a result, when the front glass substrate and the back glass substrate are made to face each other, it is difficult to realize the alignment of the electrodes with high accuracy, and in particular, it is difficult to produce a large and high-definition plasma display device.

  In addition, soda-lime glass has a low volume resistivity (log ρ) at 150 ° C. of 8.4 Ω · cm, and the mobility of alkali components in the glass is large. Accordingly, the alkali component in the glass reacts with a thin film electrode such as an ITO film or a nesa film, thereby causing a problem of changing the electric resistance value of the electrode material.

From these circumstances, in order to solve the problems of volume resistivity, thermal deformation and heat shrinkage of the glass substrate, it has a thermal expansion coefficient equivalent to that of soda lime glass, and has a volume resistivity higher than that of soda lime glass. A high strain point glass having a strain point is used for a glass substrate, and a large and high definition plasma display device is produced.
JP-A-8-290938 JP-A-8-290939

  However, in general, high strain point glass has a higher high-temperature viscosity of glass than soda-lime glass. Therefore, it is necessary to increase the melting temperature and molding temperature of the glass, and melting and molding become 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.

  An object of the present invention is to provide a glass substrate for a flat panel display device, which is made of high strain point glass having a thermal expansion coefficient that can be easily melted and molded and that is easily compatible with surrounding materials.

The glass substrate for a flat panel display device of the present invention is, in mass percentage, SiO ₂ 54 to 70%, Al ₂ O ₃ 0 to less than 5%, MgO 7 to 15%, CaO 0 to less than 7%, SrO 0. ~20%, BaO 0~20%, RO (RO represents MgO, CaO, SrO, and BaO) 19 super _{~25%, Na 2 O 0~10%} , K 2 O 0~15%, ZrO 2 0~ It is characterized by 10%.

  The glass substrate of the present invention has a low high temperature viscosity and is excellent in meltability and moldability. Furthermore, since it has a high strain point and a thermal expansion coefficient that can be consistent with the surrounding materials, it is suitable as a glass substrate for flat panel display devices, particularly plasma display devices.

Since the glass substrate for flat panel display devices of the present invention has a low high temperature viscosity, a glass substrate having excellent meltability and formability can be obtained. Specifically, the temperature of the glass melt corresponding to a viscosity of 10 ⁴ dPa is set to 1150 ° C. or lower (preferably 1145 ° C. or lower). In addition, when this temperature becomes higher than 1150 degreeC, not only shaping | molding will become difficult, but a burden will be applied to a shaping | molding apparatus.

In order to set the temperature of the glass melt corresponding to a viscosity of 10 ⁴ dPa to 1150 ° C. or lower, the content of Al ₂ O ₃ is decreased and RO (RO represents MgO, CaO, SrO, BaO) is increased. Can be adjusted. However, when the content of Al ₂ O ₃ decreases, the strain point of the glass decreases. In addition, when the RO content increases, the glass becomes devitrified and it becomes difficult to mold, or the crack resistance (crack resistance) of the glass decreases, and the glass substrate is easily damaged and cracked in the glass substrate transporting process and the like. Become.

Therefore, in the glass substrate for flat panel display device of the present invention, among RO, the adverse effect on crack resistance is small, and more than 7% by mass of MgO, which is a component that raises the strain point of glass, is contained. . Further, the RO content is strictly adjusted to more than 19 to 25% by mass, and the Al ₂ O ₃ content is suppressed to less than 5% by mass, thereby suppressing devitrification, lowering of crack resistance and high temperature viscosity. The rise of is suppressed. By doing in this way, the glass substrate which consists of high strain point glass which has the outstanding meltability and moldability can be obtained, maintaining crack resistance.

  In the glass substrate for a flat panel display device of the present invention, the reason why the glass composition is limited as described above is as follows.

SiO ₂ is a component that forms a glass network former. The content is more than 54 to 70%, preferably 58 to 68%, more preferably 60 to 66%. 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, making it difficult to achieve consistency with surrounding materials. On the other hand, 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, and the glass substrate is cracked in the thermal process when manufacturing the display device. Or heat deformation or shrinkage is likely to occur.

Al ₂ O ₃ is a component that increases the strain point of glass. The content is 0 to less than 5%, preferably 0 to 4%, more preferably 0.1 to 3%. 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.

  MgO is a component that raises the strain point of the glass without reducing the crack resistance of the glass and significantly lowers only the high-temperature viscosity of the glass to improve the meltability and formability. The content is more than 7 to 15%, preferably more than 7 to 13%, more preferably more than 7 to less than 10%. If the content of MgO is increased, the glass tends to be devitrified and it becomes difficult to mold. On the other hand, when the content is reduced, the strain point of the glass tends to be lowered, and the glass substrate is easily cracked or thermally deformed or contracted easily in the heat process when manufacturing the display device. Moreover, the high temperature viscosity of glass becomes high, and melting and forming become difficult.

  CaO is a component that lowers the high-temperature viscosity of the glass and improves the meltability and moldability. The content is 0 to less than 7%, preferably 0 to 6%, more preferably 0 to 5%. When the content of CaO is increased, the crack resistance of the glass is lowered, and the glass substrate is easily damaged and cracked in the glass substrate transporting process and the like.

  SrO is a component that lowers the high-temperature viscosity of the glass to improve the meltability and formability, and increase the volume resistivity. Its content is 0-20%, preferably 0-15%, more preferably 0-11%. When the content of SrO increases, the glass tends to be devitrified and it becomes difficult to mold. Further, the crack resistance of the glass is lowered, and the glass substrate is easily scratched and broken during the glass substrate transport process.

  BaO, like SrO, is a component that lowers the high-temperature viscosity of glass to increase meltability and formability, or to increase volume electrical resistivity. Its content is 0-20%, preferably 0-10%, more preferably 0-5%. When the content of BaO is increased, the glass tends to be devitrified and it is difficult to mold. Further, the crack resistance of the glass is lowered, and the glass substrate is easily scratched and broken during the glass substrate transport process.

  In order to lower the high temperature viscosity of the glass and improve the meltability and formability without reducing the crack resistance of the glass, RO, which is the total amount of MgO, CaO, SrO and BaO, is 19 It needs to be more than 25%. When the content of RO increases, the crack resistance of the glass decreases, and the glass substrate easily breaks in the manufacturing process. Moreover, when content decreases, the high temperature viscosity of glass will rise and it will become difficult to fuse | melt and shape | mold. A preferable range is more than 19 to 24%, more preferably more than 19 to 23%.

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. Its content is 0-10%, preferably 0-6%, more preferably 0-5%. When the content of Na ₂ O increases, the thermal expansion coefficient becomes too large, and it becomes difficult to match the thermal expansion coefficient of the surrounding materials. In addition, the strain point of glass tends to decrease, and the glass substrate is easily cracked or thermally deformed or contracted easily during the heat process when manufacturing the display device.

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. The content is 0 to 15%, preferably 7 to 14%, more preferably 9 to 13%. When the content of K ₂ O increases, the thermal expansion coefficient becomes too large, and it becomes difficult to match the thermal expansion coefficient of the surrounding materials. In addition, the glass strain point tends to decrease, and the glass substrate is easily cracked, or is likely to be thermally deformed or shrunk in the heat process when manufacturing the display device.

ZrO ₂ is a component that increases the strain point of glass. The content is 0 to 10%, preferably 0.1 to 4%, more preferably 0.1 to 3%. If the content of ZrO ₂ increases, devitrification will tend to occur and molding becomes difficult.

In the present invention, in addition to the above components, for example, to reduce X-ray coloring, the liquid phase temperature is lowered to 5% CeO ₂ and to 3% TiO ₂ to prevent ultraviolet coloring. In order to improve the moldability, Y ₂ O ₃ , La ₂ O ₃ and Nb ₂ O ₃ are each added up to 3% as colorants, and Fe ₂ O ₃ , CoO, NiO, Cr ₂ O ₃ , Nd ₂ It is possible to add up to 2% of O ₃ each, and as a clarifier, As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , 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.

Further, in the present invention, the thermal expansion coefficient of the glass 80~100 × 10 ^-7 / ℃ (more preferably 80~95 × 10 ^-7 / ℃) preferably to. If the thermal expansion coefficient of the glass is out of this range, it does not match the thermal expansion coefficient of the surrounding materials, and it becomes difficult to perform frit sealing well.

  Further, it is preferable that the strain point of the glass is 570 ° C. or higher (more preferably 575 ° C. or higher). When the strain point of the glass is lower than 570 ° C., the glass substrate is easily cracked or thermally deformed or contracted easily in the heat process when manufacturing the display device.

  Next, a method for producing a glass substrate for a flat panel display device of the present invention will be described.

  First, a glass raw material is prepared so that it may become said glass composition range. Subsequently, the prepared glass raw material is put into a continuous melting furnace, the glass raw material is heated and melted, defoamed, then supplied to a molding apparatus, and the molten glass is formed into a plate shape and gradually cooled to obtain a glass substrate. be able to.

  As a method for forming the glass substrate, there are various forming methods such as a float method, a slot down draw method, an overflow down draw method, and a redraw method, but it is preferable to form the glass substrate into a plate shape by the float method. The reason is that in the case of the float process, it is easy to obtain a large glass substrate at a relatively low cost.

  Hereinafter, the glass substrate for flat panel display devices of the present invention will be described in detail based on examples.

  Table 1 shows examples (sample Nos. 1 to 4) and comparative examples (samples No. 5 and 6) of the present invention. Sample No. 6 is a high strain point glass conventionally used.

  Each sample in the table was prepared as follows.

  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.

For each sample thus obtained, the coefficient of thermal expansion, the strain point, the temperature of the glass melt corresponding to the viscosity of 10 ⁴ dPa and the crack resistance were measured and shown in the table.

As can be seen from the table, the sample No. In each of the samples 1-4, the temperature of the glass melt corresponding to 10 ⁴ dPa · s was as low as 1140 ° C. or less, and the moldability was excellent. The thermal expansion coefficient is 83.0 to 85.0 × 10 ⁻⁷ / ° C., has a thermal expansion coefficient that is well matched with the surrounding materials, and has a strain point of 570 ° C. or higher. Thermal deformation and thermal shrinkage of the glass substrate can be suppressed. Furthermore, the crack resistance was 480 mN or more.

On the other hand, sample No. which is a comparative example. In 5 and 6, the temperature of the glass melt corresponding to 10 ⁴ dPa · s was as high as 1160 ° C. or higher, and the moldability was inferior.

  In addition, about the thermal expansion coefficient, the cylindrical sample of diameter 5.0mm and length 20mm was produced, and the average thermal expansion coefficient in 30-380 degreeC was measured with the dilatometer.

  Further, the strain point was measured based on ASTM C336-71. In addition, it is better that this temperature is high, and thermal deformation and thermal shrinkage of the glass substrate in the thermal process when manufacturing the display device can be suppressed.

The temperature of the glass melt corresponding to a glass viscosity of 10 ⁴ dPa · s was measured by a platinum ball pulling method. In addition, this temperature becomes a standard at the time of shape | molding glass in plate shape, and the one where this temperature is lower will have a good moldability.

  For the measurement of crack resistance, the method proposed by Wada et al. (M. Wada et al. Proc., The Xth ICG, vol. 11, Ceram. Soc., Japan, Kyoto, 1974, p39) was used. 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. Then, the number of cracks generated from the four corners of the indentation was counted up to 15 seconds after unloading, and the ratio to the maximum number of cracks (4) that could be generated was determined to obtain the crack generation rate. Further, the load when the crack occurrence rate was 50% 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.

  The crack occurrence rate 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%.

  In addition, the thermal expansion coefficient, density, and crack resistance were measured using heat-treated materials so as not to be affected by thermal history. In this heat treatment, the sample is heated from room temperature to the glass strain point + 80 ° C. at a rate of temperature increase of 10 ° C./min, held at that temperature for 1 hour, and then cooled to 500 ° C. at a rate of temperature decrease of 2 ° C./min. Then, it was performed under the condition of cooling to room temperature at a temperature decreasing rate of 10 ° C./min.

  The glass substrate for a flat panel display device of the present invention is not limited to the plasma display device application, and can be used for, for example, a field emission display and an electroluminescence display.

Claims (3)

By mass percentage, SiO ₂ 54 to 70%, Al ₂ O ₃ 0 to less than 5%, MgO 7 to 15%, CaO 0 to less than 7%, SrO 0 to 20%, BaO 0 to 20%, RO ( RO represents MgO, CaO, SrO, BaO) Flat panel display characterized by being over 19-25%, Na ₂ O 0-10%, K ₂ O 0-15%, ZrO ₂ 0-10% Glass substrate for equipment. The glass substrate for a flat panel display device according to claim 1, wherein a coefficient of thermal expansion at 30 to 380 ° C. is 80 to 100 × 10 ⁻⁷ / ° C. The glass substrate for a flat panel display device according to claim 1 or 2, wherein the glass melt has a strain point of 570 ° C or higher and the temperature of the glass melt corresponding to a viscosity of 10 ⁴ dPa · s is less than 1150 ° C. .