JP2006143523A - Glass substrate for display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a glass substrate for a flat panel display device which is high in strain point, high in heat resistance, high in toughness and low in density and which has a composition capable of being melted by a float process allowing a mass production. <P>SOLUTION: The glass substrate for the flat panel display device substantially contains, by weight, 63-69% SiO<SB>2</SB>, 0.5-3% Al<SB>2</SB>O<SB>3</SB>, 2-6% Na<SB>2</SB>O, 12-16% K<SB>2</SB>O, 10-15% MgO, 0.2-2% CaO, 0-2% SrO, 0-1% BaO and 0.5-3.5% ZrO<SB>2</SB>and is characterized in that the 10<SP>2</SP>poise temperature is ≤1,560°C, the 10<SP>4</SP>poise temperature is ≤1,180°C and the temperature difference between the 10<SP>4</SP>poise temperature and the devitrification temperature is ≥30°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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.

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, in recent years, alkali-alkaline earth-silica glass similar to soda lime silica glass, thermal expansion coefficient approximates to soda lime silica glass, strain point exceeds 550 ° C, Or the high strain point glass which exceeds 600 degreeC is used (refer patent documents 1-3). 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.

Furthermore, since conventional high strain point glass is brittle compared to soda lime silica glass, there is a problem that it is easily broken when various treatments are performed. Generally, glass cracking is considered to be brittle fracture starting from scratches, and resistance to this fracture is called fracture toughness (K _IC ). In order to improve the cracking problem, a glass having a high K _IC is required.

Therefore, glass having a low density and a high K _IC is strongly desired for the glass substrate for display devices, and such glasses have been proposed (Patent Documents 4 to 6).
Japanese Patent No. 2738036 JP-A-9-202641 JP-A-9-255354 JP 11-314933 A JP 2002-193635 A JP 2001-226138 A

  However, the conventional high strain point glass has a composition slightly different from that of soda lime silica glass, and the density of the conventional high strain point glass is larger than that of soda lime silica glass and exceeds 2.6. There are many things. For example, the above-mentioned Japanese Patent Laid-Open No. 9-255354 includes a large amount of SrO and BaO, so that the density exceeds 2.8, and the density becomes 3 or more in a wide range. This has a problem that it is difficult to reduce the weight of the display device, and also causes a problem of deflection due to the weight of the glass substrate. 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 formula (1). 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.

W = c (ρ / E) (L ⁴ / t ² ) (1)
W: maximum deflection, L: distance between two side supports, t: plate thickness, ρ: glass density, E: Young's modulus of glass, c: constant

However, in order to lower the glass density or increase the K _IC , it is necessary to reduce the alkali oxides and alkaline earth oxides to increase the network-forming oxide.・ Molding temperature rises. For example, the above-mentioned JP-A-11-314933 and JP-A-2002-193635 have a low thermal expansion coefficient of 75 × 10 ⁻⁷ / ° C. or lower, and the thermal expansion matching with other members constituting the panel Sexuality gets worse. In addition, the above-mentioned patent increases the high-temperature viscosity of the glass because of this, so the melting temperature and molding temperature of the 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 and the productivity is lowered. Further, for example, in the above-mentioned JP-A No. 2001-226138, P ₂ O ₅ is required, so that there is a possibility that the glass is colored due to subtle fluctuations in melting and molding conditions.

  In order to solve these problems, the object of the present invention is a glass having a thermal expansion coefficient comparable to that of ordinary soda lime silica glass, excellent heat resistance, and extremely light weight and high strength. Regardless, the present invention provides a substrate glass for flat panel display devices that is easy to melt and form because it is suitable for melting including direct current melting and float method molding.

Substantially expressed by weight%, SiO ₂ is 63 to 69, Al ₂ O ₃ is 0.5 to 3, Na ₂ O is 2 to 6, K ₂ O is 12 to 16, MgO is 10 to 15, CaO is 0.2 to 2, SrO is 0 to 2, BaO is 0 to 1, ZrO ₂ consists 0.5-3.5, 10 ² poise temperature of the glass is 1560 ° C. or less, 10 ⁴ poise temperature 1180 ° C. or less A substrate glass for a flat panel display device having a temperature difference of 10 ⁴ poise temperature-devitrification temperature of 30 ° C. or more.

Furthermore, the substrate glass for a flat panel display device described above, wherein the density is less than 2.55 g / cm ³ .

Further, the substrate glass for a flat panel display device described above, wherein a linear expansion coefficient at 30 to 300 ° C. is 75 to 90 × 10 ⁻⁷ / ° C.

Furthermore, it is said substrate glass for flat panel display apparatuses characterized by fracture toughness K _IC being 0.7 MPa · m ^1/2 or more.

  Furthermore, it is said substrate glass for flat panel display apparatuses characterized by a strain point being 570 degreeC or more.

  According to the present invention, it has a high strain point suitable for a substrate glass of a flat panel display device, has an appropriate density, thermal expansion coefficient, and high fracture toughness, so there is little damage to the glass due to thermal stress or deflection, Provided is a glass composition that can be melted by a float process suitable for mass production. This is extremely suitable as a glass substrate for electronic displays such as PDP, EL and FED.

Substantially expressed by weight%, SiO ₂ is 63 to 69, Al ₂ O ₃ is 0.5 to 3, Na ₂ O is 2 to 6, K ₂ O is 12 to 16, MgO is 10 to 15, CaO is 0.2 to 2, SrO is 0 to 2, BaO is 0 to 1, ZrO ₂ consists 0.5-3.5, 10 ² poise temperature of the glass is 1560 ° C. or less, 10 ⁴ poise temperature 1180 ° C. or less , and the 10 ⁴ poise temperature - a flat panel display device substrate glass temperature difference devitrification temperature is equal to or 30 ° C. or higher.

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 expansion coefficient of glass becomes too small, and the compatibility with other members constituting the display panel is deteriorated. Therefore, the range is 63 to 69%, preferably 65 to 69%.

Al ₂ O ₃ is a component that lowers density and increases fracture toughness, but also increases high-temperature viscosity. If it exceeds 3% by weight, the high-temperature viscosity of the glass melt increases and the tendency to devitrification increases. Therefore, the range is 0.5 to 3%, preferably 0.5 to 2.5%.

Na ₂ O acts as a flux at the time of glass melting together with K ₂ O, 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 becomes too low. If it exceeds 6%, the strain point is too low. Therefore, the range is 2 to 6%, preferably 3 to 5%.

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 12%, the action thereof is insufficient, and if it exceeds 16%, the linear expansion coefficient is excessive and the strain point is too low. Therefore, the range is 12 to 16%, preferably 12 to 14%. And

MgO is an essential component that can increase the fracture toughness K _IC of the glass and increase the strain point. If it is less than 10%, their action is insufficient. On the other hand, if it exceeds 15%, the tendency of devitrification increases, so that it becomes difficult to form glass. Accordingly, the range is 10 to 15%, preferably 10 to 13%.

CaO is not an essential component, but has an effect of lowering the viscosity of the molten glass at the time of melting the glass and an effect of raising the strain point of the glass. If it is less than 0.2%, the effect cannot be obtained. On the other hand, if it exceeds 2%, the fracture toughness K _IC is lowered and the tendency to devitrification is also increased, so it is introduced in the range of 0.2 to 2%.

  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 2%, the density increases and the desired value cannot be maintained, so a range of 2% or less is desirable.

  BaO 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 as in the case of SrO. If it exceeds 1%, the density increases, and the desired value cannot be maintained, so a range of 1% or less is desirable.

ZrO ₂ is an essential component having an effect of raising the strain point of glass and improving the chemical durability of the glass and suppressing devitrification, and is preferably contained in an amount of 0.5% or more. If it exceeds 3.5%, the density increases and the desired value cannot be maintained. Accordingly, the range is 0.5 to 3.5%, 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%.

Further, the present invention is 10 ² poise temperature of the glass is 1560 ° C. or less, 10 ⁴ poise temperature is at 1180 ° C. or less, 10 ⁴ poise temperature - temperature difference between liquidus temperature, characterized in that at 30 ° C. or higher .

Generally, in order to melt a glass raw material and mix it uniformly, the melt viscosity needs to be 10 ² poises or less, and the 10 ² poise temperature at this time is also referred to as a melting temperature. When this temperature is high, it becomes difficult to melt the raw material and clarify the melt, and the cost increases, for example, the furnace material is damaged. To uniformly melted like a normal float furnace, it is desirable the 10 ² poise temperature of 1560 ° C. or less.

Further, in order to form a smooth glass surface in the float kiln, it is desirable melt viscosity during molding is about 10 ⁴ poise, 10 ⁴ poise temperature is said to molding temperature. Since the melt is molded on the float bath after melting, the bath temperature must be increased as the molding temperature increases. Increasing the bath temperature adversely affects the tin of the bus and causes defects and yield reduction. Therefore, considering the effect of tin and the like, the 10 ⁴ poise temperature is desirably 1180 ° C. or lower.

The devitrification temperature here means an upper limit temperature at which devitrification occurs when the glass is maintained at a constant temperature for 2 hours. Generally, the temperature range from 10 ⁴ poise temperature to the devitrification temperature is called the working temperature range, and is a measure of the ease of the molding work. If this temperature range is narrow, the glass tends to be devitrified during the molding operation, making it difficult to mold the glass. Thus this temperature range is wider is desirable, i.e. 10 ⁴ poise temperature - temperature difference between liquidus temperature is desirably 30 ° C. or higher.

The present invention also provides the above substrate glass for a flat panel display device, wherein the density is less than 2.55 g / cm ³ . If the density is 2.55 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 a linear expansion coefficient at 30 to 300 ° C. is 75 to 90 × 10 ⁻⁷ / ° C. When the linear thermal expansion coefficient is less than 75 or exceeds 90 × 10 ⁻⁷ / ° C., the thermal expansion consistency with other members constituting the panel is deteriorated.

Further, the substrate glass for a flat panel display device described above, wherein the fracture toughness K _IC is 0.7 MPa · m ^1/2 or more. When the fracture toughness K _IC is less than 0.7 MPa · m ^1/2, there is a problem that it is easily broken during the manufacturing process of the display device.

  Further, the substrate glass for a flat panel display device described above, wherein the strain point is 570 ° C. or higher. The strain point is a characteristic indicating the heat resistance of glass, and if it is less than 570 ° C., it is not suitable because thermal deformation increases in the display panel manufacturing process.

  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. About these glasses, high temperature viscosity (temperature corresponding to glass viscosity of 10 ² poise and 10 ⁴ poise), devitrification temperature (° C.), strain point (° C.), density (g / cm ³ ), 30 to 300 ° C. The average linear expansion coefficient (10 ⁻⁷ / ° C.) and fracture toughness K _IC (MPa · m ^1/2 ) were measured by the following methods.

The high temperature viscosity was measured by a platinum ball pulling method. As described above, the temperature of 10 ² poise is a standard temperature when the glass is melted, and the temperature of 10 ⁴ poise is a standard temperature when the glass is formed into a plate shape. Formability will be good. The devitrification temperature was measured by a rapid cooling method using a platinum holder and a temperature gradient furnace. 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). 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)
Table 1 is an example and Table 2 is a comparative example. Examples 1 to 9 in Table 1 are glasses in the present invention, and Comparative Example 1 is soda lime silica glass. Comparative Example 2 is a conventional high strain point glass, and Comparative Examples 3 and 4 are light and high strength high strain point glasses. In the soda-lime silica glass of Comparative Example 1, the moldability of the glass is good, the density is less than 2.55, and the fracture toughness K _IC is 0.7 MPa · m ^1/2 or more. It shows that it is significantly lower than the high strain point glass of No. 4. On the other hand, the conventional high strain point glass of Comparative Example 2 has a strain point as high as 570 ° C. or higher, but the density exceeds 2.6, and the fracture toughness K _IC is less than 0.7 MPa · m ^1/2 . is there. In Comparative Examples 3 and 4, the strain point is as high as 580 ° C. or higher, the density is less than 2.55, and the fracture toughness K _IC is 0.7 MPa · m ^1/2 or more, but 10 ² poise or 10 ⁴ poise. Since the temperature is high and the difference between the 10 ⁴ poise temperature and the devitrification temperature is small, it can be seen that it is not easy to melt and form the glass.

On the other hand, the glasses of Examples 1 to 9 have a linear expansion coefficient equivalent to that of soda lime silica glass, have a sufficiently high strain point of 570 ° C. or higher, and a density of less than 2.55, and fracture toughness. K _IC exceeds 0.7 MPa · m ^1/2 or more, and moreover, the temperature difference between 10 ² poise or 10 ⁴ poise temperature and 10 ⁴ poise temperature-devitrification temperature is appropriate. Is easy. Therefore, the present invention has a linear expansion coefficient equivalent to that of soda lime silica glass, heat resistance equivalent to that of a conventional high strain point glass, and low density and high fracture toughness. It is clear that it can be easily manufactured by the float process.

Claims (5)

Substantially expressed by weight%, SiO ₂ is 63 to 69, Al ₂ O ₃ is 0.5 to 3, Na ₂ O is 2 to 6, K ₂ O is 12 to 16, MgO is 10 to 15, CaO is 0.2 to 2, SrO is 0 to 2, BaO is 0 to 1, ZrO ₂ consists 0.5-3.5, 10 ² poise temperature of the glass is 1560 ° C. or less, 10 ⁴ poise temperature 1180 ° C. or less , and the 10 ⁴ poise temperature - a flat panel display device substrate glass temperature difference devitrification temperature is equal to or 30 ° C. or higher. The substrate glass for a flat panel display device according to claim 1, wherein the density is less than 2.55 g / cm ³ . The substrate glass for a flat panel display device according to claim 1 or 2, wherein the linear expansion coefficient at 30 to 300 ° C is 75 to 90 × 10 ^-7 / ° C. The substrate glass for flat panel display devices according to claim 1, wherein the fracture toughness K _IC is 0.7 MPa · m ^1/2 or more. 5. The substrate glass for flat panel display devices according to claim 1, wherein the strain point is 570 [deg.] C. or higher.