JP4807024B2 - Substrate glass for display devices - Google Patents

Description

  The present invention relates to a glass composition having high productivity, excellent heat resistance, light weight and high strength because it is suitable for melting including direct electric melting and float molding. In particular, glass substrates that require the same thermal expansion coefficient and high heat resistance as ordinary soda lime silica glass, such as electronic displays such as PDP (plasma display panel), EL (electroluminescence), and FED (field emission display). The present invention relates to a glass composition suitable for an industrial substrate.

  Currently, high strain point glass is used in the PDP manufacturing field, and alkali-free glass is used in the LCD manufacturing field.

Conventionally, in a PDP manufacturing field, the thermal expansion coefficient of the normal temperature to 300 ° C. as the substrate glass is 80-90 × 10 ^{over 7} / ° C. approximately, strain point have used soda lime silica glass of about 510 to 520 ° C.. Soda lime silica glass is used in many fields and is advantageous in that it can be easily procured at a low price. However, since the strain point is low, the electrode glass pattern is arranged on the glass substrate, and the insulation coating with low melting point glass is formed. The problem that it is easy to occur arises.

  In order to eliminate the above problems, currently, alkali, alkaline earth, and silica glass similar to soda lime silica glass has a thermal expansion coefficient close to that of soda lime silica glass, and the strain point exceeds 550 ° C. or 600 A high strain point glass exceeding ℃ is used (see Patent Documents 1 to 3). These substrates using glass are less susceptible to thermal deformation in the manufacturing process of the display panel, and have good thermal expansion consistency with other members constituting the panel.

On the other hand, in the LCD manufacturing field, alkali-free glass containing no alkali metal oxide is used. Since these substrates using glass have a small average linear expansion coefficient at 30 to 300 ° C. of 40 × 10 ⁻⁷ / ° C. or less and a high strain point of 640 ° C. or more in the manufacturing process of the display panel, the thermal shrinkage is low. There is an advantage that it is small (see Patent Documents 4 and 5).
Japanese Patent Laid-Open No. 10-45423 Japanese Patent Application Laid-Open No. 11-240735 JP 2000-103638 A JP 2002-29776 A JP 2002-308643 A

    However, since the conventional high strain point glass has a thermal expansion coefficient close to that of soda lime silica glass in the manufacturing process of the display panel, there is a problem that the thermal shrinkage is large and the thermal deformation is large in the panel manufacturing process.

  On the other hand, the alkali-free glass has a small thermal expansion coefficient and can suppress thermal deformation. However, since there is no alkali oxide or alkaline earth oxide, the melting / molding temperature is increased. Moreover, since the high temperature viscosity of glass becomes high, the melting temperature and molding temperature of glass must be increased, and melting and molding become difficult. In particular, in the molding by the float process, if the high-temperature viscosity of the glass is high, it adversely affects the kiln and the tin of the float bath. For this reason, there is a problem that the production is inevitably caused by the fusion method and the productivity is poor.

  In order to eliminate the above problems, the glass of the present invention is a glass having a thermal expansion coefficient lower than that of the high strain point glass and higher than that of the alkali-free glass. The substrate using this glass in the PDP manufacturing process has a low thermal expansion coefficient, so that there is little thermal deformation, and the thermal expansion consistency with other members constituting the panel is not a big problem. Furthermore, since it is a high strain point glass having a strain point exceeding 580 ° C., the substrate is unlikely to warp or shrink during various heat treatments in the display panel manufacturing process.

  On the other hand, even when this glass is used in the LCD manufacturing process, since it is a high strain point glass having a strain point exceeding 580 ° C., when performing various heat treatments in the display panel manufacturing process, the substrate is less likely to warp or shrink. Since this glass can be manufactured by the FL method, the productivity is high and the area can be easily increased.

  From the above, the glass of the present invention can improve the problems of the glass substrate for PDP and LCD, respectively, and has intermediate characteristics, so it can be used for both.

Substantially in terms of% by weight, SiO ₂ is 59 to 69, Al ₂ O ₃ is 0.5 to 3, Na ₂ O is 2 to 4, K ₂ O is 1.5 to 3.5, R ₂ O ( However, R is Na, K) is 3.5 to 7.5, Na ₂ O / R ₂ O is 0.3 to 1, MgO is 3 to 5.5, CaO is 5 to 8, SrO is 6 to 7 0.5, BaO is 4 to 14, R′O (where R ′ is Mg, Ca, Sr, Ba) is 20 to 29, and ZrO ₂ is 1 to 4.5.

Moreover, it is said substrate glass for display apparatuses characterized by the average linear expansion coefficient in 30-300 degreeC being (55-70) * 10 < ^-7 > / degreeC.

  Further, the substrate glass for a flat panel display device described above, which has a strain point of 580 ° C. or higher.

  The substrate glass for a display device described above, wherein Young's modulus is 75 to 85 GPa.

Moreover, it is said substrate glass for flat panel display apparatuses characterized by fracture toughness K _IC being 0.6 MPa · m ^1/2 or more.

Furthermore, the substrate glass for a flat panel display device described above, wherein the density is less than 2.9 g / cm ³ .

  According to the present invention, the problems of the PDP and the glass substrate for LCD can be improved and have intermediate characteristics, so that they can be used for both, and also suitable for mass production such as the float process. A very suitable glass substrate for display can be obtained.

Substantially in terms of% by weight, SiO ₂ is 59 to 69, Al ₂ O ₃ is 0.5 to 3, Na ₂ O is 2 to 4, K ₂ O is 1.5 to 3.5, R ₂ O ( However, R is Na, K) is 3.5 to 7.5, Na ₂ O / R ₂ O is 0.37 to 0.72 , MgO is 3 to 5.5, CaO is 5 to 8, SrO is 6 ~ 7.5, BaO is 4 to 14, R'O (where R 'is Mg, Ca, Sr, Ba) is 20 to 29, and ZrO2 is ₁ to 4.5. .

SiO ₂ is a main component of glass, and if it is less than 59% by weight, the heat resistance or chemical durability of the glass is deteriorated. On the other hand, if it exceeds 69%, the high-temperature viscosity of the glass melt increases, and glass molding becomes difficult. Moreover, the linear expansion coefficient of glass becomes too small, and the compatibility with other members constituting the display panel is deteriorated. Therefore, the range is 59 to 69%, preferably 59 to 63%.

Al ₂ O ₃ is a component that increases the strain point and decreases the density. If the weight percentage is less than 0.5%, the heat resistance or chemical durability of the glass is deteriorated. On the other hand, if it exceeds 3%, the tendency to devitrify the glass becomes large, and it becomes difficult to mold the molten glass. Therefore, it is 0.5 to 3% of range.

Na ₂ O acts as a flux at the time of glass melting together with K ₂ O. If it is less than 2%, the high-temperature viscosity of the glass melt becomes high and glass molding becomes difficult. On the other hand, if it exceeds 4%, the thermal expansion coefficient becomes large. Therefore, the range is 2 to 4%.

K ₂ O exhibits the same effect as Na ₂ O. If it is less than 1.5%, the high-temperature viscosity of the glass melt becomes high and glass molding becomes difficult. On the other hand, if it exceeds 3.5%, the thermal expansion coefficient increases. Therefore, the range is 1.5 to 3.5%.

With respect to the amount of the alkali component (Na ₂ O, K ₂ O), the linear thermal expansion coefficient, the high temperature viscosity and the devitrification temperature are maintained in appropriate ranges by setting the total amount to 3.5 to 7.5%. can do. If the total amount of the alkali components is less than 3.5%, the high-temperature viscosity of the glass melt becomes high and glass molding becomes difficult. Further, the tendency of glass to devitrify increases. If it exceeds 7.5%, the thermal expansion coefficient increases excessively. Therefore, it is set to 3.5 to 7.5% of range.

  MgO has the effect | action which lowers | hangs the viscosity of the molten glass at the time of glass melting. If it is less than 3%, the high-temperature viscosity of the glass melt becomes high, and glass molding becomes difficult. On the other hand, if it exceeds 5.5%, the tendency of devitrification of the glass increases and it becomes difficult to mold the molten glass. Therefore, the range is 3 to 5.5%.

  CaO has the effect of lowering the viscosity of the molten glass at the time of melting the glass and the effect of increasing the thermal expansion coefficient of the glass. If it is less than 5%, the thermal expansion coefficient of the glass becomes too low. On the other hand, if it exceeds 8%, the tendency of devitrification increases, and it becomes difficult to mold molten glass. Therefore, the range is 5 to 8%.

  SrO is not an essential component, but has the effect of suppressing the occurrence of devitrification by lowering the high-temperature viscosity of the glass melt in the presence of CaO. If it is less than 6%, the high-temperature viscosity of the glass melt becomes high and glass molding becomes difficult. On the other hand, if it exceeds 7.5%, the density becomes too high, so a range of 6 to 7.5% or less is desirable.

  BaO is not an essential component, but has an effect of suppressing the devitrification tendency of the glass melt and an effect of lowering the Young's modulus. If it is less than 4%, the tendency of devitrification of the glass increases, and it becomes difficult to mold molten glass. Since density will rise when it exceeds 14%, the range of 4-14% or less is desirable.

  Further, within the above composition range, the total amount of the divalent metal oxide R′O (R ′ is Mg, Ca, Sr, Ba) is set to a range of 20 to 29%, thereby improving the meltability of the glass. While maintaining in a good range, a glass having a suitable viscosity-temperature gradient and good glass moldability, excellent heat resistance, chemical durability and the like, and having an appropriate range of thermal expansion coefficient can be obtained.

  When the total amount of R′O is less than 20%, the high-temperature viscosity increases, making it difficult to melt and mold the glass. In addition, the strain point is lowered too much and the thermal expansion coefficient is lowered. On the other hand, if it exceeds 29%, the density particularly increases, the tendency to devitrification increases, and the chemical durability decreases. A more preferable range is 25 to 29%.

ZrO ₂ has the effect of increasing the strain point of the glass and improving the chemical durability of the glass. If it is less than 1%, the desired strain range of the glass cannot be maintained. If it exceeds 4.5%, the density increases, and any desired value cannot be maintained. Therefore, it is 1 to 4.5%, preferably 1 to 4.5%.

Although the glass of the preferable aspect of this invention consists of said component substantially, in the range which does not impair the objective of this invention, you may contain other components to 1% in total amount. For example, a total amount of SO ₃ , Cl, F, As ₂ O _{3 and the} like may be contained up to 1% in order to improve melting, fining, and moldability of glass. Further, _Fe 2 _O 3 to color the glass, CoO, may contain NiO, etc. up to 1% in total. Further, in order to prevent electron beam browning in the PDP, TiO ₂ and CeO ₂ may each be contained up to 1%, and the total amount may be contained up to 1%.

The thermal expansion coefficient and strain point are characteristics indicating the heat resistance of glass, and if the thermal expansion coefficient is 70 × 10 ⁻⁷ / ° C. or higher, thermal deformation becomes excessive in the display panel manufacturing process, which is not suitable. Also, if the strain point is 580 ° C. or lower, thermal deformation becomes excessive in the display panel manufacturing process, which is not suitable.

The present invention also provides the above substrate glass for a flat panel display device, wherein the density is less than 2.9 g / cm ³ . If the density is 2.9 g · cm ³ or more, the display device cannot be reduced in weight.

Further, the substrate glass for a flat panel display device described above, wherein the fracture toughness K _IC is 0.6 MPa · m ^1/2 or more and the Young's modulus is 75 to 85 GPa. These characteristics are related to the fragility of the glass. Outside these ranges, there is a problem that the glass is easily broken during the manufacturing process of the display device.

  Hereinafter, a description will be given based on examples.

(Creation of glass)
A prepared raw material consisting of silica sand, aluminum oxide, sodium carbonate, sodium sulfate, potassium carbonate, magnesium oxide, calcium carbonate, strontium carbonate, barium carbonate and zirconium silicate is charged into a platinum crucible, and 1450 to 1600 ° C., about 6 in an electric furnace. It was melted by heating for hours. During the heating and melting, the glass melt was stirred with a platinum rod to homogenize the glass. Next, the molten glass was poured into a mold to form a glass block, which was transferred to an electric furnace maintained at 600 to 700 ° C. and gradually cooled in the furnace. The obtained glass sample was homogeneous without bubbles or striae.

Table 1 shows the glass composition (as oxide) based on the raw material formulation. For these glasses, strain point (° C.), density (g / cm ³ ), average linear expansion coefficient (10 ⁻⁷ / ° C.) of ³⁰ to 300 ° C., Young's modulus (GPa), and fracture toughness K _IC (MPa · m ^1/2 ) was measured by the following method.

  The strain point was measured by a beam bending method based on JIS R3103-2. The density was measured by the Archimedes method using glass without bubbles (about 50 g). The expansion coefficient measured the average linear expansion coefficient in 30-300 degreeC using the thermomechanical analyzer TMA8310 (Rigaku Denki Co., Ltd. product). The Young's modulus was measured using a single-around type acoustic wave measuring device UVM-2 (manufactured by Ultrasonic Industry Co., Ltd.). Fracture toughness was calculated by a fine ceramic fracture toughness test method (indentation press-in method) described in JIS R 1607 using a microhardness meter DMH-2 (manufactured by Matsuzawa Seiki Co., Ltd.).

(result)
Examples 1 to 7 in Table 1 are glasses in the present invention, and Comparative Example 1 is soda lime silica glass. Comparative Examples 2 to 4 are conventional high strain point glasses, and Comparative Examples 5 to 7 are conventional alkali-free glasses. In the soda lime silica glass of Comparative Example 1 and the high strain point glasses of Comparative Examples 2 to 4, although the density, Young's modulus, and fracture toughness are appropriate values, the thermal expansion coefficients are all 70 × 10 ⁻⁷ / ° C. That's it. Further, in the alkali-free glasses of Comparative Examples 5 to 7, although the density and strain point are appropriate values, the thermal expansion coefficients are all 55 × 10 ⁻⁷ / ° C. or less, and the Young's modulus is 75 GPa or less. It is.

On the other hand, the glass of Examples 1 to 7 has a thermal expansion coefficient in the range of 55 to 70 × 10 ⁻⁷ / ° C., and has a desired density, strain point, fracture toughness value, and Young's modulus. is there. Accordingly, the glass of the present invention has the same density, strain point, fracture toughness value and Young's modulus as the conventional high strain point glass, and has a lower thermal expansion coefficient than the high strain point glass. As compared with the strain point glass, it is obvious that the thermal deformation of the glass substrate in the heat treatment process in the display panel manufacturing process is small and the generation of thermal stress is small.

Compared to conventional alkali-free glass, the thermal deformation of the glass substrate in the heat treatment process in the display panel manufacturing process is comparable, and since it can be manufactured by the FL method, the productivity is improved and the area is increased. It is obvious that it is easy.

Claims (6)

Substantially in terms of% by weight, SiO ₂ is 59 to 69, Al ₂ O ₃ is 0.5 to 3, Na ₂ O is 2 to 4, K ₂ O is 1.5 to 3.5, R ₂ O ( However, R is Na, K) is 3.5 to 7.5, Na ₂ O / R ₂ O is 0.37 to 0.72 , MgO is 3 to 5.5, CaO is 5 to 8, SrO is 6 A substrate glass for a display device in which ~ 7.5, BaO is 4 to 14, R'O (where R 'is Mg, Ca, Sr, Ba) is 20 to 29, and ZrO2 is ₁ to 4.5. The average coefficient of linear expansion (55~70) × 10- ⁷ / ℃ a display device substrate glass according to claim 1, characterized in that at 30 to 300 ° C.. 3. The substrate glass for a flat panel display device according to claim 1, wherein the strain point is 580 ° C. or higher. The substrate glass for a display device according to any one of claims 1 to 3, wherein Young's modulus is 75 to 85 GPa. The substrate glass for flat panel display devices according to any one of claims 1 to 4, wherein the fracture toughness K _IC is 0.6 MPa · m ^1/2 or more. The substrate glass for a flat panel display device according to any one of claims 1 to 5, wherein the density is less than 2.9 g / cm ³ .