JP4482699B2 - Glass substrate for flat panel display - Google Patents

Description

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

  The plasma display device is manufactured as follows. First, a transparent electrode made of an ITO film, a nesa film or the like is formed on the surface of the front glass substrate, a dielectric material is applied thereon, and baked at a temperature of about 500 to 600 ° C. to form a dielectric layer. Further, a back dielectric material is applied to a back glass substrate on which an electrode made of Al, Ag, Ni, or the like is formed, and is baked at a temperature of about 500 to 600 ° C. to form a dielectric layer, on which a partition wall is formed. A circuit is formed by applying a material and baking it at a temperature of about 500 to 600 ° C. to form a partition. 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.

Because of these circumstances, glass with a thermal expansion coefficient equivalent to that of soda-lime glass and higher volume resistivity and strain point than soda-lime glass is used for the glass substrate, and a large, high-definition plasma display device is produced. Has been.
JP-A-8-290938 JP-A-8-290939

  However, glasses such as those disclosed in Patent Documents 1 and 2 have 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 molding, it is easy to obtain a large glass substrate at a low cost. However, if the high-temperature viscosity of the glass is high, the temperature of the float bath for molding molten glass into a plate shape must be increased. The amount of volatilization of tin from the steel increases, which adversely affects the glass surface.

  The object of the present invention is excellent in meltability and moldability, and heat deformation and heat shrinkage are not a problem in a heat process when manufacturing a display device. Moreover, an alkali component in glass, an ITO film, a nesa film, etc. It is to provide a glass substrate for a flat panel display device in which a thin film electrode hardly reacts.

The glass substrate for a flat panel display device of the present invention is in mass percentage and has a glass composition of SiO ₂ 50-60%, Al ₂ O ₃ 5-15%, MgO 4-10%, CaO 0-3%, SrO 0. ~18%, BaO 2~18%, RO (RO represents MgO, CaO, SrO, and _{BaO) 20~30%, Na 2 O} 0~10%, K 2 O 0~12%, R 2 O (R ₂ O represents Na ₂ O, K ₂ O) 7 to less than 12.5%, ZrO ₂ 1 to 10%, strain point is 575 ° C. or higher, corresponding to a viscosity of 10 ⁴ dPa · s The glass melt has a temperature of 1120 ° C. or lower, and a volume resistivity (log ρ) at 150 ° C. of 11.0 Ω · cm or higher.

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

The glass substrate for a flat panel display device of the present invention has excellent meltability and moldability because the high temperature viscosity of the glass is low. Specifically, the temperature of the glass melt corresponding to a viscosity of 10 ⁴ dPa · s is 1120 ° C. or lower (preferably 1110 ° C. or lower). In addition, when this temperature becomes higher than 1120 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 · s to 1120 ° C. or less, RO (RO represents MgO, CaO, SrO, BaO) or R ₂ O (R ₂ O is Na ₂ O). , Which represents a large amount of K ₂ O).

  However, 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.

In addition, when the content of R ₂ O increases, the strain point of the glass decreases, and thermal deformation and thermal shrinkage are likely to occur in the thermal process when manufacturing the display device. It falls, and the alkali component in glass reacts with a thin film electrode such as an ITO film or a nesa film, so that the electric resistance value of the electrode material easily changes.

Therefore, in the glass substrate for a flat panel display device of the present invention, 4% by mass or more of MgO that does not affect crack resistance is included in RO, and 3% by mass or less of CaO that further reduces crack resistance. I have to. At the same time, the RO content is strictly adjusted to 20 to 30% by mass to suppress devitrification, and suppress the decrease in crack resistance and the increase in high temperature viscosity. Furthermore, the content of R ₂ O is strictly adjusted to 7 to less than 12.5% by mass to suppress a decrease in strain point and volume resistivity. By doing in this way, the glass substrate which has the outstanding crack resistance, a meltability, and a moldability, and also has a high strain point and volume electrical resistivity can be obtained.

  In the glass substrate of the present invention, the glass has a strain point of 575 ° C. or higher (more preferably 580 ° C. or higher) in order to suppress the occurrence of thermal deformation and thermal shrinkage in the heat process when manufacturing the display device. It is adjusted to.

  Further, in order to suppress the reaction between the alkali component in the glass and the thin film electrode such as ITO film or Nesa film and stabilize the electric resistance value of the electrode material, the volume electric resistivity of the glass at 150 ° C. is 11.0 Ω · cm. It is adjusted so that it is more (more preferably 11.5 Ω · cm or more).

In order to increase the strain point and volume resistivity of the glass, the content of R ₂ O may be reduced.

The glass substrate of the present invention has a coefficient of thermal expansion of more than 75 to 100 × 10 ⁻⁷ / ° C. (preferably more than 75 to 90 × 10 ⁻⁷ / ° C.). Sealing can be performed satisfactorily. 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. In order to make the thermal expansion coefficient of the glass within the above range, the contents of SiO ₂ , Al ₂ O ₃ , Na ₂ O, and K ₂ O may be adjusted.

The specific composition that can be used for the glass substrate for a flat panel display device of the present invention is, by mass percentage, SiO ₂ 50 to 70%, Al ₂ O ₃ 5 to 15%, MgO 4 to 10%, CaO 0 to 3%. SrO 0-18%, BaO 2-18%, RO (RO represents MgO, CaO, SrO, BaO) 20-30%, Na ₂ O 0-10%, K ₂ O 0-15%, R ₂ O (R ₂ O represents Na ₂ O, K ₂ O) 7 to less than 12.5% and ZrO ₂ 0 to 10%, and the range may be selected so as to satisfy the above condition.

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

SiO ₂ is a component that forms a glass network former. The content is 50 to 60 %, preferably 52 to 60%, more preferably 54 to 58%. When the content of SiO ₂ increases, the high-temperature viscosity of the glass increases, so that melting and molding become difficult, and the thermal expansion coefficient 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. Its content is 5-15%, preferably 5-10%, more preferably 5-7%. 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. 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.

  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. Its content is 4 to 10%, preferably 4 to 9%, more preferably 5 to 8%. 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. Its content is 0 to 3%, preferably 1 to 3%, more preferably 1.5 to 2.5%. When the content of CaO is increased, the crack resistance of the glass is remarkably lowered, and the glass substrate is easily damaged and broken 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 0-18%, preferably 3-12%, more preferably 5-9%. 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 increase volume electrical resistivity. Its content is 2-18%, preferably 5-12%, more preferably 6-9%. 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. On the other hand, when the content decreases, the high-temperature viscosity of the glass increases, and melting and molding become difficult.

  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, 20 Need to be ~ 30%. 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 preferred range is 22-28%, more preferably 23-26%.

Na ₂ O is a component that lowers the high-temperature viscosity of the glass and improves the meltability and moldability. It is also a component that adjusts the thermal expansion coefficient of glass. Its content is 0-10%, preferably 2-8%, more preferably 4-6%. When the content of Na ₂ O increases, the strain point of the glass tends to decrease, and thermal deformation and thermal shrinkage are likely to occur in the thermal process when manufacturing the display device. In addition, the volume resistivity of the glass is lowered, and the glass, the alkali component, and the thin film electrode such as the ITO film or the nesa film react to easily change the electric resistance value of the electrode material. Furthermore, the coefficient of thermal expansion becomes too large, making it difficult to match the coefficient of thermal expansion of the surrounding material.

K ₂ O, like Na ₂ O, is a component that lowers the high-temperature viscosity of glass and improves meltability and moldability. It is also a component that adjusts the thermal expansion coefficient of glass. Its content is 0 to 1 2%, preferably 3 to 12%, more preferably 4% to 7%. When the content of K ₂ O increases, the strain point of the glass tends to decrease, and thermal deformation and thermal contraction are likely to occur in the thermal process when manufacturing the display device. In addition, the volume resistivity of the glass is lowered, and the glass, the alkali component, and the thin film electrode such as the ITO film or the nesa film react to easily change the electric resistance value of the electrode material. Furthermore, the coefficient of thermal expansion becomes too large, making it difficult to match the coefficient of thermal expansion of the surrounding material.

In order to reduce the high temperature viscosity of the glass without significantly reducing the strain point and volume resistivity of the glass and to obtain a thermal expansion coefficient that matches the thermal expansion coefficient of the surrounding material, Na ₂ O and K the R ₂ O is a total amount of ₂ O, must be less than 7 to 12.5%. When the content of R ₂ O increases, the strain point and volume resistivity of the glass tend to decrease, and the thermal expansion coefficient becomes too large, making it difficult to match the thermal expansion coefficient of the surrounding materials. On the other hand, when the content of R ₂ O decreases, the high temperature viscosity of the glass increases, and melting and molding become difficult. In addition, the thermal expansion coefficient becomes too small, making it difficult to match the thermal expansion coefficient of the surrounding material. A preferable range is 7 to 12%, and more preferably 9 to 11.5%.

ZrO ₂ is a component that increases the strain point of glass. Its content is 1-10 %, preferably 1-7%, more preferably 2-5%. If the content of ZrO ₂ is increased, 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.

  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, heated and melted, defoamed, then supplied to a forming apparatus, formed into a plate shape, and slowly cooled to obtain a glass substrate.

  The glass substrate of the present invention is preferably formed into a plate shape by a float method, but other than this method, various forming methods such as a slot down draw method, an overflow down draw method, and a redraw method may be adopted. Can do.

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

  Tables 1 and 2 show examples (sample Nos. 1 to 9) and comparative examples (samples No. 10 and 11) of the present invention. Sample No. 11 is a commercially available high strain point glass for plasma display devices.

  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, strain point, glass melt temperature corresponding to a viscosity of 10 ⁴ dPa · s, volume resistivity and crack resistance were measured, and the results are shown in the table. It was.

As is apparent from the table, sample No. In each of the samples 1 to 9, the temperature of the glass melt corresponding to 10 ⁴ dPa · s was as low as 1120 ° C. or less, and the moldability was excellent. The thermal expansion coefficient is 83.0 to 85.0 × 10 ⁻⁷ / ° C., the thermal expansion coefficient is well matched with the surrounding materials, and the strain point is 580 ° C. It is possible to suppress thermal deformation and thermal shrinkage of the glass substrate. Furthermore, the volume electrical resistivity at 150 ° C. was 12.4 Ω · cm or more, and the crack resistance was 400 mN or more.

In contrast, Sample No. as a comparative example. No. 10 has a low strain point of 555 ° C., so that it is expected that the glass substrate is likely to be thermally deformed or contracted in the heat treatment step. Sample No. No. 11, the temperature of the glass melt corresponding to 10 ⁴ dPa · s was as high as 1160 ° C., and the moldability was poor.

  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, the higher this temperature is, the more the thermal deformation and thermal shrinkage of the glass substrate in the thermal process when manufacturing the display device can be suppressed.

The glass melt temperature 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.

  About volume electrical resistivity, the value in 150 degreeC was measured based on ASTMC657-78. In addition, the higher this value is, the more the electrical resistance value of the electrode material can be stabilized by suppressing the reaction between the alkali component in the glass and the thin film electrode such as ITO film or Nesa film.

  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 is counted by 15 seconds after the unloading, and the ratio to the maximum number of cracks (4) that can be generated is obtained 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 (2)

In percent by mass, as a glass _{composition, SiO 2 50~60%, Al 2} O 3 5~15%, 4~10% MgO, CaO 0~3%, SrO 0~18%, BaO 2~18%, RO ( RO represents MgO, CaO, SrO, BaO) 20-30%, Na ₂ O 0-10%, K ₂ O 0-12%, R ₂ O (R ₂ O represents Na ₂ O, K ₂ O) ) It contains 7 to less than 12.5%, 1 to 10% ZrO ₂ , has a strain point of 575 ° C. or higher, and the glass melt temperature corresponding to a viscosity of 10 ⁴ dPa · s is 1120 ° C. or lower. A glass substrate for a flat panel display device having a volume electrical resistivity (log ρ) at 150 ° C. of 11.0 Ω · cm or more. The glass substrate for a flat panel display device according to claim 1, wherein the thermal expansion coefficient at 30 to 380 ° C. is more than 75 to 100 × 10 ⁻⁷ / ° C.