JP2003335548A - Alkalifree glass, and glass substrate for display using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alkalifree glass which satisfies the characteristics required for a glass substrate for TFT-LCD (thin-film-transistor liquid crystal display) and besides does not deteriorate in the glass melt properties even when reducing the content of an alkaline earth metal for the purpose of making a lightweight for the glass substrate. <P>SOLUTION: The alkalifree glass substrate comprises the composition: on the basis of % by mass, 53-70% of SiO<SB>2</SB>, 10-19% of Al<SB>2</SB>O<SB>3</SB>, 8-20% of B<SB>2</SB>O<SB>3</SB>, 0-10% of MgO, 0-10% of CaO, 0-10% of SrO, 0-10% of BaO, 0-10% of ZnO, 0-12% of MgO+CaO+BaO+SrO+ZnO, 0-5% of ZrO<SB>2</SB>, 0.1-10% of P<SB>2</SB>O<SB>5</SB>, 0-5% of SnO<SB>2</SB>, 0-5% of Sb<SB>2</SB>O<SB>3</SB>and 0-3% of Cl, with containing substantially no alkali metal oxide, and has a density of 2.45 g/cm<SP>3</SP>or lower and a distortion spot of 600°C or higher. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

The present invention relates to a liquid crystal display, E
Flat display substrates such as L displays, charge-coupled devices (CCD), 1x proximity solid-state imaging devices (CI)
The present invention relates to a non-alkali glass suitable as a glass substrate for an image sensor such as S) or a solar cell, and a glass substrate for a display using the same.

[0002]

2. Description of the Related Art Conventionally, glass substrates have been widely used as flat display substrates for liquid crystal displays, EL displays and the like.

In particular, electronic devices such as thin film transistor type active matrix liquid crystal displays (TFT-LCD) are thin and have low power consumption, so that they are used in various fields such as car navigation systems, digital camera viewfinders, and recently personal computer monitors and TVs. It is used for various purposes.

In a TFT-LCD panel maker, after manufacturing a plurality of devices on a glass substrate (base plate) formed by a glass maker, the devices are divided and cut into products to improve productivity. We are working to improve and reduce costs. 2. Description of the Related Art In recent years, in applications such as monitors for TVs and personal computers, large-sized devices are also required, and glass substrates with a large area of 1000 × 1200 mm are required in order to multi-face these devices. .

Further, in portable devices such as mobile phones and notebook computers, there is a demand for weight reduction of the device for convenience of carrying, and a glass substrate is also demanded for weight reduction. In order to reduce the weight of the glass substrate, it is effective to reduce the thickness of the substrate. Currently, TFT-LCD
The standard thickness of the glass substrate for use is very thin, about 0.7 mm.

However, the large-sized, thin-walled glass substrate as described above has a large deflection due to its own weight, which is a serious problem in the manufacturing process.

That is, a glass substrate of this type is molded by a glass maker and then passes through processes such as cutting, slow cooling, inspection and cleaning. During these steps, the glass substrates are put into and taken out of a cassette in which a plurality of shelves are formed. This cassette can be held horizontally by placing both sides or three sides of the glass substrate on a shelf formed on the left and right inner two surfaces or the left and right and inner three surfaces. However, the large and thin glass substrate has a large amount of deflection, so when placing the glass substrate in the cassette shelf,
A part of the glass substrate is easily damaged by coming into contact with the cassette or another glass substrate, or when the glass substrate is taken out of the shelf of the cassette, it is apt to swing greatly and become unstable. Further, display manufacturers also use the same type of cassette, and therefore, the same problem occurs.

The amount of deflection of the glass substrate due to its own weight changes in proportion to the density of the glass and in inverse proportion to the Young's modulus. Therefore, in order to suppress the amount of bending of the glass substrate to a low level, it is necessary to increase the specific Young's modulus represented by the Young's modulus / density ratio. In order to increase the specific Young's modulus, a glass material having a high Young's modulus and a low density is required.
The lighter the weight, the thicker the glass of the same weight can be.
Since the amount of bending of glass changes in inverse proportion to the square of the plate thickness, the effect of reducing the bending by increasing the plate thickness is very large. Since lowering the density of the glass has a great effect on reducing the weight of the glass, the density of the glass should be as small as possible.

In general, this type of alkali-free glass contains
It contains a relatively large amount of alkaline earth metal oxides. In order to reduce the density of the glass, it is effective to reduce the content of the alkaline earth metal oxide, but since the alkaline earth metal oxide is a component that promotes the meltability of the glass, If the content is reduced, the meltability will decrease.
When the meltability of the glass decreases, internal defects such as bubbles and foreign substances are likely to occur in the glass. Bubbles and foreign matter in the glass
Since it impedes the transmission of light, it becomes a fatal defect as a glass substrate for a display, but in order to suppress such internal defects, the glass must be melted at a high temperature for a long time.

However, melting at high temperatures increases the load on the glass melting furnace. For example, refractory materials such as alumina and zirconia used in kilns are severely eroded at higher temperatures, and the life cycle of kilns is shortened. Moreover, since the number of members that can be used at high temperatures is limited, all the members used are relatively expensive. Furthermore, the running cost for keeping the inside of the kiln always at a high temperature is higher than that of glass that melts at low temperatures, and melting at high temperatures is extremely disadvantageous in producing glass. There is a demand for alkali-free glass that can be used.

Thermal shock resistance is also an important requirement for this type of glass substrate. Even if chamfering is performed, fine scratches and cracks exist on the end surface of the glass substrate, and when tensile stress due to heat is concentrated on the scratches and cracks, the glass substrate sometimes breaks. Damage to glass not only lowers the operation rate of the line, but the fine glass powder generated at the time of damage adheres to another glass substrate,
There is a high risk of causing disconnection defects, patterning defects, and the like.

By the way, the recent development direction of the TFT-LCD includes high performance such as high definition, high speed response and high aperture ratio, in addition to large screen and light weight. In order to improve the performance and reduce the weight of polycrystalline silicon TFT-LCD (p-Si.TF
Development of T-LCD) has been actively conducted. In the conventional p-Si / TFT-LCD, the manufacturing process temperature is 8
Since the temperature was extremely high at 00 ° C. or higher, only a quartz glass substrate could be used. But with recent developments,
The manufacturing process temperature has dropped to 400-600 ° C, and the amorphous silicon TFT that is currently being mass-produced
Similar to LCD (a-Si.TFT-LCD), non-alkali glass substrates have come to be used.

The manufacturing process of p-Si / TFT-LCD is as follows.
Compared with the manufacturing process of a-Si.TFT-LCD, there are many heat treatment processes, and rapid heating and rapid cooling of the glass substrate are repeated, so that the thermal shock to the glass substrate is further increased. Further, as described above, the glass substrate is large in size, not only the temperature difference easily occurs on the glass substrate, but also the probability that minute scratches and cracks are generated on the end face is high, and the substrate is destroyed during the heating process. The probability increases. The most fundamental and effective way to solve this problem is to reduce the thermal stress caused by the difference in thermal expansion, and therefore a glass having a low coefficient of thermal expansion is required. Further, lowering the coefficient of thermal expansion is preferable because the difference in thermal expansion with a thin film transistor (TFT) material such as p-Si becomes small and warpage of the glass substrate is less likely to occur.

Further, although the manufacturing process temperature of p-Si.TFT-LCD has been recently lowered, it is still a-Si.
It is considerably higher than the manufacturing process temperature of TFT-LCD. If the heat resistance of the glass substrate is low, p-Si / TFT-LCD
When the glass substrate is exposed to a high temperature of 400 to 600 ° C. in the manufacturing process of 1., a minute dimensional shrinkage called heat shrinkage occurs, which may cause a pixel pitch shift of the TFT and cause a display defect. is there. Further, if the heat resistance of the glass substrate is lower, the glass substrate may be deformed or warped. Further, in the liquid crystal manufacturing process such as film formation, the glass substrate undergoes heat shrinkage, resulting in pattern shift. In order to prevent such a problem, glass having excellent heat resistance is required.

Further, a transparent conductive film, an insulating film, a semiconductor film, a metal film, etc. are formed on the surface of the glass substrate for TFT-LCD, and various circuits and patterns are formed by photolithography etching (photo etching). It Further, in these film forming and photo-etching steps, the glass substrate is subjected to various heat treatments and chemical treatments.

Therefore, the alkali metal oxide (N
a ₂ O, K ₂ O, Li ₂ O), alkali ions diffuse during the heat treatment into the semiconductor material on which the film is formed, leading to deterioration of the film characteristics. It is required that it does not contain any substance and that it has chemical resistance so as not to be deteriorated by chemicals such as various acids and alkalis used in the photoetching step.

Generally, the TFT array process is constituted by repeating a film forming process, a resist pattern forming process, an etching process and a resist stripping process. Al as an etching solution, a phosphoric acid-based solution, ITO for etching a Mo-based film
A wide variety of chemicals such as aqua regia (HCl + HNO ₃ ) based solution is used for etching the system film, and buffered hydrofluoric acid (BHF) solution is used for etching the SiN _x , SiO ₂ film, etc. Considering it, it is managed not by disposable but by circulating liquid flow.

If the chemical resistance of the glass substrate is low, the reaction product of the chemical solution and the glass substrate during etching may clog the filter of the circulating flow system or cause clouding on the glass surface due to non-uniform etching, or A change in the composition of the etching solution may cause various problems such as an unstable etching rate. In particular, a hydrofluoric acid-based chemical solution typified by BHF strongly corrodes the glass substrate, so that the above problems are likely to occur. Therefore, it is particularly required to have excellent BHF resistance.

Regarding the chemical resistance of the glass substrate, it is important not only that the amount of erosion is small, but also that it not cause a change in appearance. It is an indispensable characteristic for a display substrate that light transmittance is important that the appearance of glass does not change due to chemical treatment, such as cloudiness and roughness.

The evaluation results of the amount of erosion and the appearance change do not necessarily match especially with respect to the BHF resistance. For example, even if the glass shows the same amount of erosion, the composition does not cause or causes the appearance change after chemical treatment. It may happen.

The glass substrate for TFT-LCD is mainly formed by the down draw method or the float method. Examples of the down draw method include a slot down draw method and an overflow down draw method. Since the glass substrate formed by the down draw method does not require polishing, it has an advantage of easily reducing the cost. However, when the glass substrate is formed by the down draw method, the glass is easily devitrified, and therefore glass having excellent devitrification resistance is required.

[0022]

Currently, TFT-LCDs are used.
As the glass substrate for use, 1737 glass manufactured by Corning Incorporated, OA-10 glass manufactured by Nippon Electric Glass Co., Ltd., and the like are commercially available. However, although these glasses are excellent in heat resistance, all of them contain a large amount of alkaline earth metal oxide in order to promote the meltability of the glass and thus have a high density. Therefore, when a glass substrate is manufactured, it is difficult to reduce the thickness due to large deflection due to its own weight.

An object of the present invention is to satisfy the characteristics required for a glass substrate for TFT-LCD, and to reduce the weight of the glass substrate, even if the content of alkaline earth metal is reduced, the glass It is an object of the present invention to provide an alkali-free glass whose meltability does not decrease.

[0024]

As a result of repeating various experiments, the inventors of the present invention have obtained a glass composition which satisfies various characteristics required for a glass substrate used for a TFT-LCD and has an excellent meltability. The present invention has been found and is proposed as the present invention.

That is, the alkali-free glass substrate of the present invention has a mass percentage of SiO ₂ 53 to 70% and Al ₂ O _{3
10~19%, B 2 O 3 8~20} %, MgO 0~1
0%, CaO 0-10%, SrO 0-10%, Ba
O 0-10%, ZnO 0-10%, MgO + CaO
+ BaO + SrO + ZnO 0-12%, ZrO ₂ 0-
_{5%, P 2 O 5 0.1~10} %, SnO 2 0~5%,
Sb ₂ O ₃ has a composition of 0 to 5% and Cl 0 to 3%, contains substantially no alkali metal oxide, and has a density of 2.45.
The feature is that the strain point is g / cm ³ or less and the strain point is 600 ° C. or more.

[0026]

In non-alkali glass, the value of RO / Al ₂ O ₃ serves as a measure of the ease of precipitation of devitrification foreign matter such as mullite and anorthite, and the smaller the value, the stronger the devitrification tendency. By the way, in order to reduce the density of glass, the alkaline earth metal oxide RO (R: M) in the glass is used.
It is most effective to reduce the content of g, Ca, Sr, Ba). However, when the RO content in the glass is reduced, the value of RO / Al ₂ O ₃ becomes small, the liquidus temperature of the glass rises remarkably, and the glass is apt to devitrify. As a result, the formability of glass is deteriorated. Al along with RO to reduce the density and prevent devitrification
₂ O ₃ content may also be possible to make to reduce increases the value of the RO / Al ₂ O _3, but in this case, the strain point of the glass decreases.

If an attempt is made to maintain the strain point and reduce the density, the composition range of RO / Al ₂ O ₃ is low, but in the alkali-free glass of the present invention, P ₂ O ₅ is added. Since it is contained as an essential component, even in such a composition range, it is possible to reduce the density of the glass without devitrifying the glass. Further, even if the content of Al ₂ O ₃ is not reduced, devitrification can be suppressed, so that the strain point of glass can be prevented from lowering. The effective addition amount of P ₂ O ₅ for suppressing devitrification is (MgO + CaO
+ BaO + SrO) / Al ₂ O ₃ molar ratio is x, P ₂
When the O ₅ content (molar percentage) is y, y ≧ −0.
It is desirable to adjust so as to have a relationship of 5x + 0.55.

The alkali-free glass of the present invention has, in addition to strain point, density, meltability and moldability, various properties required for a glass substrate used in a TFT-LCD, that is, a coefficient of thermal expansion and chemical resistance. The composition is specified in consideration of the specific Young's modulus and the like.

The reasons for limiting the other components of the alkali-free glass of the present invention will be described below.

The content of SiO _{2 in} the present invention is 53-.
70%. If it is less than 53%, chemical resistance, particularly acid resistance is deteriorated, and it is difficult to achieve low density.
On the other hand, if it is more than 70%, the viscosity at high temperature becomes high, the meltability becomes poor, and cristobalite easily occurs in the glass. The preferable range of SiO ₂ is 55 to 68%, and more preferably 55 to 65%.

The content of Al ₂ O ₃ is 10 to 19%.
If it is less than 10%, the strain point is lowered. Al ₂ O ₃ has a function of improving the Young's modulus of glass and increasing the specific Young's modulus, but if it is less than 10%, the Young's modulus is lowered.
On the other hand, if it is more than 19%, the liquidus temperature becomes high and the devitrification resistance is lowered. The preferable range of Al ₂ O ₃ is 10 to 18%, more preferably 10 to 16.9%.

B ₂ O ₃ is a component that acts as a flux and lowers the viscosity and improves the meltability. The content of B ₂ O ₃ 8-20%
Is. If it is less than 8%, the function as a flux becomes insufficient and the buffered hydrofluoric acid resistance deteriorates. If it is more than 20%, the strain point of the glass is lowered, the heat resistance is lowered and the acid resistance is deteriorated. Further, since the Young's modulus is lowered, the specific Young's modulus is lowered. The preferable range of B ₂ O ₃ is 10 to 20%, more preferably 10 to 16%.

MgO lowers the high temperature viscosity and improves the meltability of glass without lowering the strain point. Further, it has the effect of reducing the density most among the alkaline earth metal oxides. However, when contained in large amounts, the liquidus temperature rises,
The devitrification resistance decreases. Further, MgO may react with buffered hydrofluoric acid to form a product, which may adhere to the element on the surface of the glass substrate or may adhere to the glass substrate and cause it to become cloudy. Therefore, its content is limited. is there. Therefore Mg
The O content is 0 to 10%, preferably 0 to 8%, more preferably 0 to 6%, and further 0 to 0.5%.

Like MgO, CaO is also a component that lowers the high temperature viscosity and remarkably improves the meltability of glass without lowering the strain point, and its content is 0 to 10%.
If it is more than 10%, it may react with buffered hydrofluoric acid to form a product, which may adhere to the element on the surface of the glass substrate or adhere to the glass substrate to cause clouding. Ca
The preferred range of O is 2 to 10%, more preferably 2 to 8%.
%.

SrO is a component for improving the chemical resistance and devitrification resistance of glass, and its content is 0 to 10%. When it is more than 10%, the density and the thermal expansion coefficient of glass increase. The preferable range of SrO is 0 to 6%, more preferably 0 to 1.5%.

Like SrO, BaO is a component that improves the chemical resistance and devitrification resistance of glass, and its content is 0.
-10%. When it is more than 10%, the density and the thermal expansion coefficient of glass increase. The preferable range of BaO is 0 to 6
%, And more preferably 0 to 2.2%.

ZnO is a component that improves the buffered hydrofluoric acid resistance of the glass substrate and also improves the meltability,
Its content is 0 to 10%. If it is more than 10%, the glass tends to be devitrified, the strain point is lowered, and the density is increased, which is not preferable. The preferred range of ZnO is 0
3%, more preferably 0-0.9%.

MgO, CaO, BaO, SrO, ZnO
By mixing and containing each of the above components, the liquidus temperature of the glass is remarkably lowered, and it becomes difficult for crystal foreign matter to be generated in the glass, so that the meltability and formability of the glass are improved. However, if the total amount of these exceeds 12%, the density increases, the weight of the glass substrate cannot be reduced, and the specific Young's modulus decreases, which is not preferable. The preferred range of the total amount of these components is 0 to 10%, more preferred range is 0 to 8.5%, and further 4 to 8.5%.

ZrO ₂ is a component that improves the chemical resistance of glass, especially the acid resistance, and improves the Young's modulus.
When the amount is larger, the liquidus temperature rises, and devitrified foreign matter of zircon is likely to occur, which is not preferable. The preferable range of ZrO ₂ is 0 to 3%, more preferably 0 to 1%.

P ₂ O ₅ suppresses devitrification of glass, has a high strain point,
It is an essential component for obtaining low-density glass. That is,
In order to reduce the density of glass while maintaining the strain point of glass, even if the value of RO / Al ₂ O ₃ is reduced, P ₂ O ₅
By containing, it is possible to suppress devitrification of the glass. The content of P ₂ O ₅ is 0.1 to 10%. 0.1%
If less, devitrification occurs in the glass. On the other hand, if it exceeds 10%, the glass undergoes phase separation and opalescence, and the acid resistance remarkably deteriorates, which is not preferable. The preferred range of P ₂ O ₅ is 0.1 to 8%, more preferably 0.1 to 6%.

In addition to the above components, in the present invention, in order to improve the chemical resistance and meltability of glass, TiO ₂ is added at 5%.
Can be included. However, if it exceeds 5%, the glass is colored and its transmittance is reduced, which is not preferable as a glass substrate for a display.

Further, Y ₂ O ₃ , Nb ₂ O ₃ and La ₂ O ₃ are also 5%.
It can be contained to the extent. These components are strain points,
Although it has a function of increasing the Young's modulus and the like, it is not preferable to contain a large amount thereof because the density increases.

Further, in the glass of the present invention, As ₂ O ₃ , Sb ₂ O ₃ , Sb ₂ O ₅ ,
A fining agent such as F ₂ , Cl ₂ , SO ₃ , C, or a metal powder such as Al or Si can be contained up to 5%.
Further, CeO ₂ , SnO ₂ , Fe ₂ O _{3 and the} like can be contained up to 5% as a fining agent.

By the way, when melting non-alkali glass as in the present invention, As ₂ O ₃ which works at high temperature has been used as a fining agent. However, in recent years, it has become difficult to use environmentally hazardous chemical substances such as As ₂ O ₃ from the viewpoint of considering the environment. Similar to As ₂ O ₃ , SnO ₂ has a fining power at a high temperature and is very effective as a fining agent for melting the alkali-free glass of the present invention. However, if it is contained in a large amount, devitrification occurs, so the content is 5% or less,
It is preferably regulated to 2% or less.

Further, Cl has an effect of promoting melting of non-alkali glass, and by adding Cl, glass is melted at a low temperature to promote the function of a fining agent, or the glass melting cost is lowered, and the length of manufacturing equipment is increased. The life can be extended. However, if the content is too large, the strain point of the glass is lowered, so that the content is desirably controlled to 3% or less. As a raw material of the Cl component, a chloride of an alkaline earth metal oxide such as barium chloride or a raw material such as aluminum chloride can be used.

Further, Sb ₂ O ₃ and Sb ₂ O ₅ are also effective as a fining agent for the alkali-free glass of the present invention, but since the alkali-free glass has a high melting temperature, the effect as a fining agent is As. Small compared to ₂ O ₃ . Therefore Sb ₂
When O ₃ or Sb ₂ O ₅ is used, it is desirable to decrease the melting temperature by increasing the amount or by combining with a component such as Cl that promotes the melting property. However, S
When b ₂ O ₃ or Sb ₂ O ₅ is contained in an amount of 5% or more, the density is increased. Therefore, the content is preferably 2% or less, more preferably 1.5%.
Limited to:

In the present invention, As is used as a fining agent.₂O₃To
If not used, Sb₂O₃, Sb ₂O_Five, SnO₂And
And one or more selected from the group of
It is preferable to contain 5 to 3.0%, especially Sb₂O₃
+ Sb₂O_Five  0.05-2.0%, SnO₂  0.01
~ 1.0%, Cl 0.005 to 1.0% contained
Most preferably.

The density of the glass is 2.45 g / cm ³ or less (preferably 2.40 g / cm) in order to reduce the amount of bending and prevent damage when the glass substrate is taken in and out of the shelf of the cassette. ³ or less).

Further, the strain point of the glass needs to be 600 ° C. or higher in order to suppress the thermal contraction of the glass substrate in the heating step.

In addition to the above characteristics, it is desired to have the following characteristics.

In order to reduce the warpage, it is desirable to approximate the coefficient of thermal expansion between the TFT material and the glass.
The average coefficient of thermal expansion of glass in the temperature range of 0 ° C. is 36
X10 ^-7 / ° C or less (preferably 26 to 33 x 10 ^-7 /
℃).

The liquidus temperature is 1200 ° C. or less (desirably 1180 ° C. or less) and the viscosity at the liquidus temperature is 10 so that devitrification does not occur even when formed into a plate by the downdraw method.
^5.0 dPa · s or more.

In order to reduce the amount of bending of the glass substrate, the specific Young's modulus is 27.5 GPa / g · cm ⁻³ or more (preferably 29.0 GPa / g · cm ⁻³ or more).

For good melting of the glass, 10
The temperature of the glass melt at a viscosity of ^2.5 dPa · s is 16
Must be 50 ° C or less.

Even if the glass substrate is dipped in a 10% HCl aqueous solution or buffered hydrofluoric acid, it has no chemical turbidity or roughness by visual observation and has excellent chemical resistance.

[0056]

EXAMPLES The present invention will be described in detail below based on examples.

Tables 1 to 8 show the example glasses of the present invention (Sample Nos. 1 to 23) and the comparative example glass (Sample No. 24).
Is shown.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3]

[0061]

[Table 4]

[0062]

[Table 5]

[0063]

[Table 6]

[0064]

[Table 7]

[0065]

[Table 8]

Each glass sample in the table was prepared as follows.

First, a batch prepared by mixing glass raw materials so as to have the composition shown in the table was put into a platinum crucible and melted at 1600 ° C. for 24 hours, and then poured onto a carbon plate to form a plate. With respect to the glass sample thus obtained, various characteristics such as density, thermal expansion coefficient, viscosity, Young's modulus, specific Young's modulus, BHF resistance, HCl resistance, liquidus temperature and liquidus viscosity were measured and shown in the table.

As is apparent from the table, No.
Each of the glass samples 1 to 23 does not contain an alkali metal oxide, has a density of 2.368 g / cm ³ or less, a thermal expansion coefficient of 28 to 33 × 10 ⁻⁷ / ° C., and a strain point of 618 ° C. or more. Met. The specific Young's modulus is 29.0 GPa / g · cm ^-3
As described above, the erosion amount was 0.9 in the evaluation of BHF resistance.
Less than μm, erosion amount is 8.1μ in the evaluation of HCl resistance
It was excellent as m or less, and no change was confirmed in the appearance evaluation. From this, each sample of the example is
It can be understood that it is suitable as a glass substrate for LCD.

Further, each of these samples had a high temperature viscosity of 10
^2.5The temperature corresponding to dPa · s is 1650 ° C. or lower
Therefore, it easily melts, the liquidus temperature is 1172 ° C or less, and the liquidus viscosity is
Is 10 ^5.0Excellent in devitrification resistance because it is more than dPa · s
I was there. Therefore, each sample of the example has excellent productivity.
Can understand.

On the other hand, No. The glass sample of No. 24 has a liquidus temperature of 1224 ° C., a liquidus viscosity of 10 ^4.7 dPa · s, which is low, and is expected to have poor devitrification resistance and moldability.

The density in the table was measured by the well-known Archimedes method.

For the thermal expansion coefficient, the average thermal expansion coefficient in the temperature range of 30 to 380 ° C. was measured using a dilatometer.

The strain point and annealing point are ASTM C336-7.
It measured based on the method of 1. The higher these values,
This means that the heat resistance of glass is high. The softening point is A
It was measured based on the method of STM 338-93. Also
Viscosity 10^4.010,^3.010, ^2.5Each temperature is
It was measured by the lifting method. High temperature viscosity 10^2.5dPa
The temperature corresponding to s indicates the melting temperature.
The lower the value, the better the meltability.

The Young's modulus was measured by the resonance method, and the specific Young's modulus was obtained from the values of Young's modulus and density.

The BHF resistance and the HCl resistance were evaluated by the following methods. First, both surfaces of each glass sample were optically polished, then a part thereof was masked, and then immersed in a chemical solution prepared to have a predetermined concentration at a predetermined temperature for a predetermined time. After the chemical treatment, the mask was removed, and the level difference between the mask portion and the eroded portion was measured with a surface roughness meter, and the value was taken as the erosion amount. Also, after optically polishing both sides of each glass sample, after immersing it in a chemical solution prepared to a prescribed concentration for a prescribed time at a prescribed temperature, visually observing the glass surface to make it cloudy or rough. Or, those with cracks were marked with X, and those without any change were marked with ◯.

The chemical solution and the treatment conditions are as follows: the BHF resistance erosion amount is 130 BHF solution (NH ₄ HF: 4.6 mass%, N
H4F: 36% by mass) was used and the measurement was carried out at 20 ° C. for 30 minutes. Appearance evaluation is 63BHF solution (HF:
6% by mass, NH4F: 30% by mass) at 20 ° C,
The treatment was carried out for 30 minutes. Further, the amount of HCl-resistant erosion was measured using a 10% by mass hydrochloric acid aqueous solution at 80 ° C. for 24 hours. The appearance was evaluated using a 10 mass% hydrochloric acid aqueous solution at 80 ° C. for 3 hours.

The liquidus temperature was such that each glass sample was crushed and passed through a standard sieve 30 mesh (500 μm), and the glass powder remaining on 50 mesh (300 μm) was put in a platinum boat.
The temperature at which crystals are precipitated is measured by holding the sample in a temperature gradient furnace for 24 hours.

The liquidus viscosity indicates the viscosity of glass at the liquidus temperature. The lower the liquidus temperature and the higher the liquidus viscosity, the better the devitrification resistance and the moldability. In order to successfully form a glass substrate for a display by the down draw method, the liquidus temperature is 1200 ° C. or lower and the liquidus viscosity is 10 or less.
It is desired to be ^5.0 dPa · s or more.

In addition, the sample No. A glass substrate for display having a thickness of 0.5 mm was produced by melting glass No. 1 in a test melting furnace and molding it by an overflow down draw method. The warp of this glass substrate is 0.
075% or less, waviness (WCA) 0.15 μm or less (cutoff fh: 0.8 mm, fl: 8 mm), surface roughness (Ry) 100 Å or less (cutoff λc: 9 μ)
m), which was excellent in surface accuracy and was suitable as a glass substrate for liquid crystal displays.

[0080]

As described above, since the alkali-free glass of the present invention contains P ₂ O ₅ as an essential component, it is hard to devitrify even in the composition range where devitrification is likely to occur, and the meltability and strain are high. Low density can be achieved while maintaining the points.

Continued front page    F term (reference) 2H090 JB02 JD06 JD09 JD17                 2H092 JA24 KB21 NA11 NA26 PA01                 4G062 AA01 BB01 BB05 BB06 CC04                       DA06 DB04 DC03 DC04 DD02                       DD03 DE01 DE02 DE03 DF01                       EA01 EB01 EC01 ED01 ED02                       ED03 EE01 EE02 EE03 EF01                       EF02 EF03 EG01 EG02 EG03                       FA01 FB01 FC01 FD01 FE01                       FE02 FE03 FF01 FG01 FH01                       FJ01 FK01 FL01 GA01 GB01                       GC01 GD01 GE01 HH01 HH03                       HH05 HH07 HH09 HH11 HH13                       HH15 HH17 HH20 JJ01 JJ03                       JJ05 JJ07 JJ10 KK01 KK03                       KK05 KK07 KK10 MM01 MM27                       MM31 MM35 NN29 NN32 NN34

Claims (4)

[Claims] 1. SiO ₂ 53 to 70 in terms of mass percentage.
%, Al ₂ O ₃ 10 to 19%, B ₂ O _{3 8 to} 20%, M
gO 0-10%, CaO 0-10%, SrO 0
10%, BaO 0-10%, ZnO 0-10%, M
gO + CaO + BaO + SrO + ZnO 0-12%,
ZrO ₂ 0-5%, P ₂ O ₅ 0.1-10%, SnO ₂
It has a composition of 0-5%, Sb ₂ O ₃ 0-5%, Cl 0-3%, contains substantially no alkali metal oxide, has a density of 2.45 g / cm ³ or less, and has a strain point. Alkali-free glass characterized by having a temperature of 600 ° C. or higher. 2. (MgO + CaO + BaO + SrO) /
The alkali-free glass according to claim 1, wherein a relation of y ≧ −0.5x + 0.55 is established, where x is a molar ratio of Al ₂ O ₃ and y is a molar percentage of P ₂ O ₅ . 3. The alkali-free glass according to claim 1, which is used for display applications. 4. A glass substrate for a display, comprising the glass according to claim 1.