JP4151161B2 - Substrate glass - Google Patents

Description

【００３６】
【表２】

【００３７】
【発明の効果】
本発明によれば、ソーダ石灰ガラスと同程度の熱膨張係数を有し、軽量かつ高歪点であり、破壊じん性が高いガラス基板を提供できる。
このガラス基板をフラットディスプレイパネルに用いることにより、フラットディスプレイパネルの製造工程中のガラスの割れが減少する、ガラス基板の熱変形または熱収縮が小さくなる、パネルの構成部材として使用されるガラスフリット材料の熱膨張係数との整合が容易になる、パネルが軽量化される、等の効果が得られる。
【００３８】
また、このガラス基板を磁気ディスクに用いることにより、製造時または使用時のガラスの割れが減少するとともに、金属製固定治具の熱膨張係数との整合が容易になる。さらに、磁性層（磁気記録層）の熱処理温度を上げることができ、その結果磁性層の保磁力が高くなり磁気記録媒体の高記録密度化が可能となる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glass for a substrate having a high resistance to the progress of destruction, that is, a glass for a substrate having a high fracture toughness.
[0002]
[Prior art]
In recent years, large flat display panels represented by a color plasma display panel (hereinafter referred to as a color PDP) are becoming widespread, and glass used as a substrate has been diversified. Conventionally, ordinary soda lime glass has been widely used as a substrate for large flat display panels. One of the reasons is that it is easy to match the thermal expansion coefficient of various glass frit materials used as components of the panel including the inorganic sealing material with the thermal expansion coefficient of soda lime glass.
[0003]
On the other hand, in order to reduce the deformation and thermal shrinkage of the glass substrate in the heat treatment process of the large flat display panel manufacturing process, there is a strong demand for improving the heat resistance of the substrate glass. Therefore, it has a thermal expansion coefficient equivalent to that of soda-lime glass, has a higher strain point (about 550 ° C. or higher), and suppresses the alkali content to improve electrical insulation, so-called high Strain point glass is widely used as a substrate.
[0004]
Further, glass substrates have been put to practical use because of excellent mechanical strength such as surface smoothness and impact resistance as substrates for information recording media, particularly magnetic disk (hard disk) substrates.
[0005]
[Problems to be solved by the invention]
However, these high strain point glasses are more fragile than soda lime glass and have a problem of being easily broken during the manufacturing process. In addition, the high strain point glass has a large specific gravity, which makes it difficult to reduce the weight of the large flat display panel.
[0006]
In order to solve these problems, a glass for a substrate suitable for a flat panel display substrate, which has a small density and is hardly scratched, has been proposed (Japanese Patent Laid-Open No. 9-301733). However, the property of being hard to be scratched is effective when the scratch that is the starting point of breakage is caused in the manufacturing process of the panel, but when the scratch is scratched during processing such as cutting before the manufacturing process. Is not necessarily effective. In general, during the processing such as cutting, there are already many scratches that can be the starting points of breakage at the edge of the glass.
[0007]
Further, when glass is used as the magnetic disk substrate, many processing processes such as circular machining, centering, and chamfering on the inner and outer peripheral surfaces are required. During these processings, many scratches that could become breakage points occurred at the edges of the glass, and there was a problem that the glass was broken not only in the manufacturing process but also when using a magnetic disk. In particular, recently, it has been proposed to increase the disk rotation speed in order to improve the read / write speed. In this case, the problem of breaking the glass becomes more important.
[0008]
In order to prevent the glass from cracking in such a case, it has been necessary to provide a glass for a substrate that is essentially resistant to the progress of fracture due to tensile stress, that is, high fracture toughness.
The present invention solves the above problems, has a high glass transition point, and has a thermal expansion coefficient equivalent to that of soda-lime glass, and has a high resistance to fracture progression, that is, fracture toughness, in the production process, or It aims at providing the glass for substrates which is hard to break during use.
[0009]
[Means for Solving the Problems]
The present invention substantially represents the weight percentage,
SiO ₂ 45~65,
Al ₂ O ₃ 6-20,
B ₂ O ₃ 2.6 ~ 5,
MgO 2-5,
CaO 1-10,
SrO 0 to 6.5,
BaO 0-2,
MgO + CaO + SrO + BaO 10-17,
ZrO ₂ 0-7,
Na ₂ O + K ₂ O 7-15,
The fracture toughness is 0.70 MPa · m ^1/2 or more, the glass transition point is 600 ° C. or more, and the average thermal expansion coefficient is 50 × 10 ^{−7 to} 95 × 10 ⁻⁷ / ° C. A glass for a substrate is provided.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The glass for a substrate referred to in the present invention is a glass used for a substrate for a flat panel display such as a color PDP, a plasma addressed liquid crystal (PALC), a field emission display (FED), or a substrate for an information recording medium such as a magnetic disk. It is.
The substrate glass of the present invention is suitable for float forming.
[0011]
The glass for a substrate of the present invention is substantially expressed by weight%,
SiO ₂ 45~65,
Al ₂ O ₃ 10-20,
B ₂ O ₃ 2.6 ~ 5,
MgO 2-5,
CaO 1-10,
SrO 0 to 4.5,
BaO 0-2,
MgO + CaO + SrO + BaO 10-17,
ZrO ₂ 0-5,
Na ₂ O + K ₂ O 7-15,
Preferably it consists of.
[0012]
The reasons for limiting the composition in the present invention are as follows (in the following, unless otherwise specified,% by weight is simply expressed as%).
SiO ₂ is a network former and essential. If it exceeds 65%, the average thermal expansion coefficient at 50 to 350 ° C. (hereinafter simply referred to as thermal expansion coefficient) may be too small. Preferably it is 59% or less, More preferably, it is 55% or less, Most preferably, it is 54% or less. If it is less than 45%, heat resistance and chemical durability may be lowered. Preferably it is 50% or more.
[0013]
Al ₂ O ₃ has an effect of increasing the glass transition point and heat resistance, and is an essential component. If it exceeds 20%, the thermal expansion coefficient tends to be too small, and the viscosity of the molten glass becomes too high, making float molding difficult. Preferably it is 16% or less. If it is less than 6%, the effect is small. Preferably it is 10% or more, More preferably, it is 12% or more.
In the case where the glass for a substrate of the present invention is melted in a glass melting furnace in which an AZS (Al ₂ O ₃ —ZrO ₂ —SiO ₂ ) electrocast brick is used in a portion where the molten glass is in direct contact, Al ₂ The content of O ₃ is preferably 6% or more and less than 10%. If it is 10% or more, the erosion property of the molten glass against the AZS electrocast brick may be increased.
[0014]
B ₂ O ₃ has an effect of increasing the fracture toughness and lowering the viscosity of the molten glass when the glass is melted, and is an essential component. If it exceeds 6%, the thermal expansion coefficient tends to be too small, or B ₂ O ₃ volatilization at the time of melting the glass may be excessive. Preferably it is 5% or less. If it is less than 0.5%, the effect is small. Preferably it is 1% or more, More preferably, it is 2% or more. In order to increase the effect, 2.6 to 5% is preferable. In order to suppress damage due to volatilization B ₂ O ₃ in the glass melting furnace furnace material is preferably set to 0.5 to 2.5%, more preferably less than 0.5% to 1%.
[0015]
MgO has an effect of increasing the fracture toughness and lowering the viscosity of the molten glass when the glass is melted, and is an essential component. If it exceeds 5%, the glass may become unstable. Preferably it is 4% or less. If it is less than 2%, the effect is small. Preferably it is 3% or more.
[0016]
CaO has an effect of increasing the thermal expansion coefficient and lowering the viscosity of the molten glass when the glass is melted, and is an essential component. If it exceeds 10%, the glass may become unstable. Preferably it is 9% or less. If it is less than 1%, the effect is small. Preferably it is 5% or more, more preferably 6% or more.
[0017]
SrO is not essential, but has the effect of increasing the coefficient of thermal expansion and lowering the viscosity of the molten glass during glass melting, and may be added up to 6.5%. If it exceeds 6.5%, the specific gravity may be too large. Preferably it is 4.5% or less, More preferably, it is 4% or less, Most preferably, it is 3% or less.
[0018]
BaO is not essential, but has the effect of increasing the coefficient of thermal expansion and lowering the viscosity of the molten glass at the time of melting the glass, and up to 2% may be added. If it exceeds 2%, the specific gravity may be too large. Preferably it is 1% or less.
[0019]
The total amount of SrO and BaO is preferably 7% or less. If it exceeds 7%, the specific gravity may be too large. More preferably, it is 6% or less, and particularly preferably 5% or less.
[0020]
The total amount of MgO, CaO, SrO and BaO is 10 to 17%. If it exceeds 17%, the glass may become unstable. Preferably it is 15% or less. If it is less than 10%, the viscosity of the molten glass at the time of melting the glass may be too high. Preferably it is 12% or more.
[0021]
ZrO ₂ is not essential, but may be added up to 7% in order to increase fracture toughness, increase glass transition point, and improve alkali resistance. If it exceeds 7%, the glass tends to be unstable, and the glass may be easily damaged. Preferably it is 5% or less, More preferably, it is 4% or less. When glass substrate cleaning using an alkaline cleaning liquid is performed, ZrO ₂ is preferably more than 5% and 7% or less.
[0022]
Na ₂ O and K ₂ O are components having an effect of increasing the thermal expansion coefficient and lowering the viscosity of the molten glass at the time of melting the glass, and the total amount thereof is 7 to 15%. If it exceeds 15%, chemical durability and electrical insulation properties may be deteriorated. Preferably it is 13% or less. If it is less than 7%, the effect is small. Preferably it is 9% or more.
[0023]
Na ₂ O is preferably 1 to 10%. If it exceeds 10%, the electrical insulation property may be lowered. More preferably, it is 7% or less, and particularly preferably 6% or less. If it is less than 1%, the mixed alkali effect (improvement of electrical insulation) due to coexistence with K ₂ O may be reduced, or the viscosity of the molten glass at the time of melting the glass may be increased.
[0024]
K ₂ O is preferably 5 to 14%. If it exceeds 14%, the electrical insulation properties may be reduced. If it is less than 5%, the thermal expansion coefficient may be small, or the glass transition point may be lowered. Preferably it is 7% or more.
[0025]
In addition to the above components, the glass of the present invention may appropriately contain a refining agent such as SO ₃ , As ₂ O ₃ , Sb ₂ O ₃ , and a coloring agent such as Fe ₂ O ₃ , NiO, CoO. In order to prevent browning due to an electron beam or the like, TiO ₂ and CeO ₂ can be added within a range of 2% or less and a total amount of 2% or less, respectively.
[0026]
Furthermore, ZnO may be added in order to improve the solubility. However, if it is added in an amount of 5% or more, it may be reduced in a float bath in which float forming is performed to cause a defect.
In order to obtain the same effect as Na ₂ O and K ₂ O, Li ₂ O may be added. However, since excessive addition may cause a decrease in the glass transition point, it is preferably made 2% or less.
[0027]
The fracture toughness of the glass of the present invention is preferably 0.70 MPa · m ^1/2 or more in order to make it difficult to break during the production process or during use.
The specific gravity of the glass of the present invention is preferably less than 2.65, particularly 2.6 or less, for weight reduction.
[0028]
The glass transition point of the glass of the present invention is preferably 600 ° C. or higher in order to make it difficult for thermal deformation or thermal shrinkage of the glass substrate. This corresponds to a strain point of about 550 ° C. or higher.
The thermal expansion coefficient of the glass of the present invention is about 80 × 10 ^{−7 to} 95 × 10 ⁻⁷ / ° C., particularly 80 × 10 ^{−7 to} 90 × 10 ⁻⁷ / ° C., which is similar to that of soda lime glass. preferable.
[0029]
The glass substrate using the glass for a substrate of the present invention can be produced, for example, by the following method. That is, the raw material of each component normally used is mixed so that it may become a target component, this is continuously thrown into a melting furnace, and it heats and melt | dissolves at 1500-1650 degreeC. The molten glass is formed into a predetermined plate thickness by a float method, and is cooled and then cut to obtain a transparent glass substrate.
[0030]
【Example】
The raw materials were prepared so as to have the composition indicated by weight% in the upper part of the table, put in a platinum crucible, heated to 1550 to 1650 ° C. and dissolved for 4 to 5 hours. Meanwhile, the mixture was stirred for 2 hours with a platinum stirrer to homogenize the glass. Next, molten glass was poured out and formed into a plate shape, and then slowly cooled.
In the column of RO total amount and M ₂ O total amount in the table, the total amount of MgO, CaO, SrO, BaO, and the total amount of Na ₂ O, K ₂ O are shown by weight%.
[0031]
About the obtained glass, specific gravity, fracture toughness (unit: MPa · m ^1/2 ), thermal expansion coefficient (unit: 10 ⁻⁷ / ° C.), glass transition point (unit: ° C.), and some glasses The strain point (unit: ° C.), the viscosity η in the molten state, and the specific resistance ρ (unit: Ω · cm) were also measured. The measurement results are shown in the table. Shown in the columns of log η = 4 and log η = 2 in the table are temperatures (unit: ° C.) at which the viscosity η is 10 ⁴ poise and 10 ² poise, respectively. The former is an indicator of float moldability, and the latter is an indicator of glass solubility. Also, what is shown in the log ρ column of the table is the common logarithm of ρ at 150 ° C. ρ is an index of electrical insulation, and log ρ is preferably 9.5 or more at 150 ° C.
[0032]
The various measurement methods are shown below.
Specific gravity: Measured by Archimedes method for about 30 g of glass lump containing no foam.
Fracture toughness: Int. J. et al. Fracture, 16 (1980) 137-141. That is, a chevron-type notch was formed at the center of a test piece having a thickness of 8 mm, a width of 8 mm, and a length of 80 mm. Using a Tensilon type strength tester, a four-point bending test was performed at a crosshead speed of 0.005 mm / min so that stable fracture occurred from the notch tip of the test piece supported at a span of 64 mm. The upper span was 16 mm. In order to avoid the fatigue effect of the glass due to moisture, the measurement was performed in a dry N ₂ atmosphere.
[0033]
Thermal expansion coefficient: A differential thermal dilatometer was used to measure the elongation of the glass when the temperature was raised from room temperature at a rate of 5 ° C./min using quartz glass as a reference sample. The measurement was performed up to a temperature at which the glass was softened and elongation was no longer observed, that is, the yield point, and an average linear thermal expansion coefficient of 50 to 350 ° C. was calculated.
Strain point: Measured by a method defined in JIS R3103.
Glass transition point: The temperature corresponding to the bending point in the thermal expansion curve obtained at the time of measuring the thermal expansion coefficient was read and used as the glass transition point.
Viscosity in the molten state: measured by the rotating cylinder method.
Specific resistance: Measured by the method specified in ASTM C657.
[0034]
As apparent from Table, the fracture toughness of Examples 1 to 1 1 of glass which is an embodiment of the present invention is 0.70 MPa · m ^1/2 or more, resistance to the progress of destruction is high. Moreover, specific gravity is also less than 2.65, and the weight reduction of a glass substrate is easy. On the other hand, the glass of Comparative Examples 1 2 and 1 3 is a glass known as a color PDP substrate and a magnetic disk substrate, respectively, but the fracture toughness is less than 0.70 MPa · m ^1/2 , It has a low resistance to progress and has a high probability of cracking during the manufacturing process or during use.
[0035]
[ Table 1 ]

[0036]
[Table 2]

[0037]
【The invention's effect】
According to the present invention, a glass substrate having a thermal expansion coefficient comparable to that of soda-lime glass, having a light weight and a high strain point, and having a high fracture toughness can be provided.
By using this glass substrate for a flat display panel, the glass frit material used as a component of the panel is reduced, the glass deformation during the manufacturing process of the flat display panel is reduced, and the thermal deformation or shrinkage of the glass substrate is reduced. The effects such as easy matching with the coefficient of thermal expansion and weight reduction of the panel can be obtained.
[0038]
Further, by using this glass substrate for a magnetic disk, glass breakage during production or use is reduced, and matching with the thermal expansion coefficient of the metal fixture is facilitated. Furthermore, the heat treatment temperature of the magnetic layer (magnetic recording layer) can be raised, and as a result, the coercive force of the magnetic layer is increased and the recording density of the magnetic recording medium can be increased.

Claims (3)

Substantially in weight% display,
SiO ₂ 45~65,
Al ₂ O ₃ 6-20,
B ₂ O ₃ 2.6 ~ 5,
MgO 2-5,
CaO 1-10,
SrO 0 to 6.5,
BaO 0-2,
MgO + CaO + SrO + BaO 10-17,
ZrO ₂ 0-7,
Na ₂ O + K ₂ O 7-15,
The fracture toughness is 0.70 MPa · m ^1/2 or more, the glass transition point is 600 ° C. or more, and the average thermal expansion coefficient is 50 × 10 ^{−7 to} 95 × 10 ⁻⁷ / ° C. The glass for substrates characterized by the above-mentioned.   2. The glass for a substrate according to claim 1, wherein the specific gravity is less than 2.65. The glass for a substrate according to claim 1 or 2, wherein Na ₂ O + K ₂ O is 13.2% by weight or less.