JP2005281101A - Glass substrate for display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a desired glass substrate for a flat panel display, which has a high strain point, high heat resistance, high toughness, and a low density. <P>SOLUTION: The glass substrate for the flat panel display device substantially comprises, by weight, 63-69% SiO<SB>2</SB>, 2-6% Al<SB>2</SB>O<SB>3</SB>, 66-72% of SiO<SB>2</SB>+Al<SB>2</SB>O<SB>3</SB>, 2-5% Na<SB>2</SB>O, 9-12% K<SB>2</SB>O, 12-17% of Na<SB>2</SB>O+K<SB>2</SB>O, 2-10 MgO, 5-10% CaO, 0-3% SrO, 0-2% BaO, 10-15% of MgO+CaO, 0-3% of SrO+BaO, 10-15% RO (wherein, R is Mg, Ca, Sr or Ba), and 0.8-4% Zr0<SB>2</SB>, and is characterized in that the strain point is ≥570°C. Further, the glass substrate is characterized in that the average coefficient of thermal expansion within a range of 30-300°C is (75-85)×10<SP>-7</SP>/°C, the Young's modulus E is 71-76 GPa, and the density is <2.6 g/cm<SP>3</SP>. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a substrate glass for a plasma display device, and more particularly to a substrate glass for a display device suitable as a substrate glass for a plasma display panel (PDP).

Conventionally, in the PDP manufacturing field, soda lime silica glass having a thermal expansion coefficient of about 80 to 90 × 10 ⁻⁷ / ° C. and a strain point of about 510 to 520 ° C. has been used as a substrate glass. 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, in recent years, alkali-alkaline earth-silica glass similar to soda lime silica glass has a thermal expansion coefficient close to that of soda lime silica glass, and a strain point exceeds 550 ° C., or High strain point glass exceeding 600 ° C. has been proposed. These are intended to obtain the required physical properties by preparing glass components, and in comparison with soda lime glass, there are fewer SiO ₂ and alkaline earth oxide (MgO, CaO, SrO, BaO) components. And increasing the ZrO ₂ component increases the strain point. (For example, Patent Documents 1 to 3). These substrates using glass are less susceptible to thermal deformation in the manufacturing process of the display panel, and also have good thermal expansion consistency with other members constituting the panel.
JP-A-8-290939 JP 10-152339 A Japanese Patent No. 2738036

However, high strain point glasses with a small amount of SiO _{2 and a} large amount of alkaline earth oxides (MgO, CaO, SrO, BaO) and ZrO ₂ have a high Young's modulus and exceed 76 GPa. In addition, the density is often higher than 2.6.

  During the manufacturing process of the display device, since various heat treatments are performed as described above, a thermal shock is applied to the glass substrate in the process of overheating and cooling, a temperature gradient is generated, and a thermal stress is generated in the glass substrate. This thermal stress σ is generally expressed by an equation such as equation (1).

Thermal stress σ = 0.31 {Eα / (1-ν)} · ΔT (γm · h / k) (1)
Here, E is the Young's modulus, α is the thermal expansion coefficient, ν is the Poisson's ratio, ΔT is the temperature change, γm is a factor depending on the material shape, h is the heat transfer coefficient of the surface, and k is the thermal conductivity of the material. Since glass that exhibits brittle fracture breaks relatively easily with such thermal stress, it is necessary to minimize the generation of thermal stress. For that purpose, in the above formula (1), E, α, ΔT, γm, h, and ν must be reduced and k must be increased, but α is inconsistent with other materials constituting the display device. The appropriate range cannot be changed from the surface, and h, k and ν are almost constant in the glass of this system. In addition, since ΔT and γm are factors determined by the conditions of the heat treatment process of the display panel and the shape of the glass substrate, it is difficult to limit them. Therefore, the magnitude of the thermal stress generated in the glass substrate largely depends on the Young's modulus E of the glass, and in a glass having a large Young's modulus, the thermal stress generated in the heat treatment process increases, and the probability that the glass substrate breaks. There is a problem of becoming higher.

  Furthermore, the Young's modulus is related to the amount of deflection due to the weight of the glass. That is, the amount of deflection (W) due to the weight of the glass substrate increases as the Young's modulus decreases, as represented by Equation (2).

W = k (ρ / E) (L ⁴ / t ² ) (2)
Here, W is the maximum amount of deflection, L is the distance between the two side supports, t is the plate thickness, ρ is the density of the glass, E is the Young's modulus of the glass, and k is a constant. For this reason, when the glass substrate is increased in size, the amount of deflection becomes larger, and there is a problem that problems such as breakage occur in the process of transporting and moving the substrate.

  Therefore, if the Young's modulus is large, there is a problem of destruction of the glass substrate due to thermal stress as described above, and if the Young's modulus is small, there is a problem such as breakage due to the deflection of the glass substrate. A range exists.

On the other hand, when the density of the glass substrate is high, there is a problem that it is difficult to reduce the weight of the display device, and the problem of deflection due to the weight of the glass substrate also occurs. That is, the amount of deflection (W) due to the weight of the glass substrate increases in proportion to the density (ρ) of the glass as represented by the equation (2). Therefore, when the glass substrate is enlarged, the amount of deflection becomes larger, and there is a problem in that problems such as breakage occur in the process of transporting and moving the substrate.
An object of the present invention is to solve the above-mentioned problems, and has a linear thermal expansion coefficient similar to that of soda lime silica glass, and has a high strain point suitable for a substrate glass of a flat panel display device, particularly a plasma display panel (PDP). Furthermore, it is an object of the present invention to provide a glass composition that is less susceptible to glass breakage due to thermal stress and deflection due to an appropriate Young's modulus and low density.

The present invention is substantially expressed in wt%, with SiO ₂ 63-69, Al ₂ O ₃ 2-6, SiO ₂ + Al ₂ O ₃ 66-72, Na ₂ O 2-5, K ₂ O. There _{9~12, Na 2 O + K 2} O is 12 to 17, MgO is 2 to 10, CaO is 5 to 10, SrO 0 to 3, BaO is 0 to 2, MgO + CaO is 10 to 15, SrO + BaO is 0 to 3 , RO (where R is Mg, Ca, Sr, Ba) is 10-15, ZrO ₂ is 0.8-4, and the strain point is 570 ° C. or higher, characterized in that it is a substrate for a flat panel display device It is glass.

Further, the substrate glass for a flat panel display device described above, wherein an average linear thermal expansion coefficient at 30 ° C. to 300 ° C. is (75 to 85) × 10 ⁻⁷ / ° C.

  Furthermore, the substrate glass for a flat panel display device described above, wherein Young's modulus E is 71 to 76 GPa.

Furthermore, the substrate glass for a flat panel display device described above, wherein the density is less than 2.6 g / cm ³ .

  According to the present invention, as described above, the linear thermal expansion coefficient is the same as that of soda lime silica glass, and it has a high strain point suitable for flat panel display devices, particularly plasma display panel (PDP) substrate glasses, and more appropriately. Because of its low Young's modulus and low density, it is possible to obtain a glass that is less damaged by thermal stress and deflection. By using this glass for a glass substrate for a flat panel display, deformation and cracking due to heat and dead weight of the glass substrate in the display panel manufacturing process are reduced, and the manufacturing efficiency of the display device is improved.

The present invention is substantially expressed in wt%, with SiO ₂ 63-69, Al ₂ O ₃ 2-6, SiO ₂ + Al ₂ O ₃ 66-72, Na ₂ O 2-5, K ₂ O. There _{9~12, Na 2 O + K 2} O is 12 to 17, MgO is 2 to 10, CaO is 5 to 10, SrO 0 to 3, BaO is 0 to 2, MgO + CaO is 10 to 15, SrO + BaO is 0 to 3 , RO (where R is Mg, Ca, Sr, Ba) is 10-15, ZrO ₂ is 0.8-4, and the strain point is 570 ° C. or higher, characterized in that it is a substrate for a flat panel display device It is glass.

SiO ₂ is a main component of glass, and if it is less than 63% 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 thermal expansion coefficient of glass becomes too small, and compatibility with other members constituting the display panel is deteriorated. Therefore, the range is 63 to 69%, preferably 64 to 68%.

Al ₂ O ₃ is a component that increases the strain point and is an essential component. If the percentage by weight is less than 2%, the strain point of the glass is lowered. On the other hand, if it exceeds 6%, the high-temperature viscosity of the glass melt increases, and the Young's modulus increases, making it impossible to obtain the desired Young's modulus. Therefore, the range of 2 to 6%, preferably 3 to 5% is preferable.

By setting the total amount of SiO ₂ + Al ₂ O ₃ to 66 to 72%, the heat resistance and chemical durability of the glass can be maintained in an appropriate range. If the total amount is less than 66%, the heat resistance and chemical durability of the glass are too low. Further, the density increases and the desired density cannot be maintained. If it exceeds 72%, the linear thermal expansion coefficient of the glass becomes too low, and the high temperature viscosity of the glass melt becomes high, so that it becomes difficult to form the glass.

Na ₂ O acts together with K ₂ O as a flux at the time of melting the glass, and is indispensable for maintaining the linear expansion coefficient of the glass at an appropriate size. If it is less than 2%, the effect as a flux is insufficient, and the linear expansion coefficient is too low. If it exceeds 5%, the strain point is too low. Therefore, the range is 2 to 5%, preferably 3 to 4%.

K 2 _O is, with shows the same effect as Na 2 _O, and suppress the movement of the alkali ions by mixed alkali effect with Na 2 _O, it is an essential component to improve the volume resistivity of the glass. If it is less than 9%, the action thereof is insufficient, and if it exceeds 12%, the linear expansion coefficient is excessive and the strain point is too low. Therefore, the range is 9 to 12%, preferably 10 to 11%. And

Maintaining the strain point, linear thermal expansion coefficient, high temperature viscosity, and devitrification temperature in appropriate ranges by adjusting the total amount of the alkali components (Na ₂ O, K ₂ O) to 12 to 17%. I can do it. If the total amount of the alkali components is less than 12%, the coefficient of linear thermal expansion is excessively lowered, and the Young's modulus increases and the desired Young's modulus cannot be maintained. Moreover, the tendency of devitrification of the glass increases. If it exceeds 17%, the strain point will be too low, and the Young's modulus and volume resistivity will be reduced. Therefore, this range is made 12 to 17%.

  MgO has the effect of lowering the viscosity of the molten glass when the glass is melted, and also has the effect of increasing the strain point. If it is less than 2%, their action is insufficient. On the other hand, if it exceeds 10%, the Young's modulus increases and the desired Young's modulus cannot be obtained. In addition, the tendency to devitrify the glass increases, making it difficult to form the glass. Therefore, the range is 2 to 10%, preferably 4 to 8%.

  CaO has the effect of lowering the viscosity of the molten glass at the time of melting the glass and has the effect of raising the strain point of the glass, but the effect is insufficient if it is less than 5%, and devitrification if it exceeds 10%. The tendency increases and the density increases and the desired density cannot be obtained. Therefore, the range is 10 to 15%, preferably 11 to 14%.

  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 exceeds 3%, the density is too high, so a range of 3% or less is desirable.

  BaO is not an essential component, but has an effect of suppressing the devitrification tendency of the glass melt and has an effect of lowering the Young's modulus. However, since the density increases when it exceeds 2%, the range of 2% or less is desirable. .

  Further, within the above composition range, the total amount of the divalent metal oxide RO (R is Mg, Ca, Sr, Ba) is in the range of 10 to 15%, so that the melting property of the glass is in a favorable range. While maintaining the above, it is possible to obtain a glass having an appropriate viscosity-temperature gradient, good glass moldability, excellent heat resistance and chemical durability, and having an appropriate range of linear expansion coefficient. If the total amount of RO is less than 10%, the high-temperature viscosity increases and it becomes difficult to melt and mold the glass. In addition, the strain point is excessively lowered and the linear thermal expansion coefficient is lowered. On the other hand, if it exceeds 15%, the density increases, the tendency to devitrification increases, and the chemical durability decreases. A more preferable range is 11 to 14%.

ZrO ₂ has an effect of raising the strain point of the glass and improving the chemical durability of the glass, so it is preferable to contain 0.8% or more. If it exceeds 4%, the Young's modulus and density increase, and both cannot maintain desired values. Therefore, it is 0.8 to 4%, preferably 1 to 3%.

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 3% 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%.

  According to the composition of the present invention, a substrate glass for a flat panel display device having a strain point of 570 ° C. or higher can be obtained. When the strain point is less than 570 ° C., deformation of the substrate glass, such as warping and shrinkage, is performed when various heat treatments are performed on the panel production, such as arranging an electrode line pattern on the glass substrate and further forming an insulating coating with low-melting glass. The problem that it is easy to produce occurs.

Moreover, according to the said composition, the substrate glass for flat panel display apparatuses whose average linear thermal expansion coefficient in 30 degreeC-300 degreeC is (75-85) x10 < ^-7 > / degreeC can be obtained. When the average linear thermal expansion coefficient is outside (75 to 85) × 10 ⁻⁷ / ° C., the compatibility with other members constituting the display panel is deteriorated.

  Furthermore, according to the said composition, the substrate glass for flat panel display apparatuses whose Young's modulus E is 71-76 GPa can be obtained. When the Young's modulus is less than 71 GPa, the amount of deflection of the glass substrate increases, and problems such as breakage are likely to occur in the substrate transport and movement processes. On the other hand, when it exceeds 76 GPa, it becomes easy to break due to thermal stress.

Furthermore, according to the above composition, a substrate glass for a flat panel display device having a density of less than 2.6 g / cm ³ can be obtained. When the density is 2.6 g / cm ³ or more, the value becomes larger than that of general soda lime silica glass, and when the display device is increased in size, there is a possibility of causing problems such as deformation and cracking due to the weight of the glass substrate.

  Hereinafter, a description will be given based on examples.

(Creation of glass)
Silica sand as SiO ₂ source, aluminum oxide as Al ₂ O ₃ source, sodium carbonate and sodium sulfate as Na ₂ O source, potassium carbonate as K ₂ O source, magnesium oxide as MgO source, calcium carbonate as reduced CaO , Strontium carbonate as the SrO source, barium carbonate as the BaO source, and zirconium silicate as the ZrO ₂ source. These were prepared so as to have the high strain point glass compositions shown in Table 1 and Table 2, filled in a platinum crucible, and heated and melted in an electric furnace at 1550 ° C. for about 6 hours. During the heating and melting, the glass melt was stirred with a platinum rod to homogenize the glass. Next, the molten glass is poured into a mold to form a glass block, which is transferred to an electric furnace maintained at 650 ° C. and gradually cooled in the furnace. Examples 1 to 6 in Table 1 and Comparative Examples 1 to 4 in Table 2 A glass having the composition shown in FIG. The obtained glass sample was homogeneous without bubbles or striae.

For these glasses, the strain point (° C.), the average linear thermal expansion coefficient (10 ⁻⁷ / ° C.) of 30 to 300 ° C., Young's modulus (GPa), and density (g / cm ³ ) were measured by the following methods. .

  The strain point was measured by a beam bending method based on JIS R3103-2. For the linear thermal expansion coefficient, an average linear thermal expansion coefficient at room temperature to 300 ° C. was measured using a thermomechanical analyzer TMA8310 (manufactured by Rigaku Corporation). The Young's modulus was measured using a sink-around type acoustic wave measuring device UVM-2 (manufactured by Ultrasonic Industry Co., Ltd.). The density was measured by Archimedes method on glass without bubbles (about 50 g).

(result)
Various test results are shown in the table. In addition, the comparative example 1 in Table 2 is a general soda-lime silica glass.

As shown in Examples 1 to 6 in Table 1, within the composition range of the present invention, the strain point is sufficiently high as 570 ° C. or higher, the Young's modulus E is about 75 GPa, and the average linear thermal expansion coefficient is also (76 to 82) × 10 ⁻⁷ / ° C., which is a favorable result for the substrate glass for a display device. Further, the density was 2.52 to 2.56 g / cm ³ ), and a density of less than 2.6 was obtained. This is close to the density value of the soda lime silica glass of Comparative Example 1.

On the other hand, Comparative Examples 1 to 4 in Table 2 outside the composition range of the present invention have a Young's modulus E of 72 GPa and a density of less than 2.6 g / cm ^{3 in} the soda-lime silica glass of Comparative Example 1. It shows that the strain point is significantly lower than other glasses. Moreover, although the glass of Comparative Examples 2-4 has a high strain point of 570 degreeC or more, it represents that the Young's modulus E exceeds 76 GPa and the density exceeds 2.6.

Claims (4)

Substantially expressed by weight%, SiO ₂ is 63 to 69, Al ₂ O ₃ is 2 to 6, SiO ₂ + Al ₂ O ₃ is 66 to 72, Na ₂ O is 2 to 5, K ₂ O is 9 to 12 Na ₂ O + K ₂ O is 12-17, MgO is 2-10, CaO is 5-10, SrO is 0-3, BaO is 0-2, MgO + CaO is 10-15, SrO + BaO is 0-3, RO (however, R is Mg, Ca, Sr, Ba) of 10 to 15, ZrO ₂ of 0.8 to 4, and a strain point of 570 ° C. or higher, and a substrate glass for flat panel display devices. 2. The substrate glass for a flat panel display device according to claim 1, wherein an average linear thermal expansion coefficient at 30 ° C. to 300 ° C. is (75 to 85) × 10 ⁻⁷ / ° C. 3. The substrate glass for flat panel display devices according to claim 1, wherein Young's modulus E is 71 to 76 GPa. The substrate glass for a flat panel display device according to any one of claims 1 to ^{3, wherein the} density is less than 2.6 g / cm ³ .