JP2013173670A - Alkali-free glass and alkali-free glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an environmentally friendly glass substrate which suffices various characteristics required for glass for a liquid crystal display or the like, especially the characteristics such as melting characteristics and devitrification resistance, by designing a glass composition with reduced or substantially no environmentally harmful components.SOLUTION: This alkali-free glass contains, as its glass composition, 50-70% SiO, 10-20% AlO, 8-12% BO, 0-3% MgO, 4-15% CaO, 0-10% SrO, 0-1% BaO, and 0-5% ZnO in wt.% as oxide equivalent, and contains substantially no alkali metal oxide and AsO.

Description

  The present invention relates to an alkali-free glass and an alkali-free glass substrate suitable for substrates such as liquid crystal displays and organic EL displays, and cover glasses such as solid-state imaging devices such as CMOS.

  Glass substrates are widely used for displays such as liquid crystal displays and organic EL displays, substrates for hard disks, filters, sensors, etc., and cover glasses for solid-state imaging devices such as CMOS. In particular, liquid crystal displays and organic EL displays are mainly active matrix type displays in which pixels are driven by active elements typified by thin film transistors (hereinafter referred to as TFTs). It is widely used for color displays and moving image displays such as liquid crystal monitors, mobile phones and digital camera displays. In such an active matrix display, micron-order high-definition electronic circuits such as TFT elements and signal lines are formed on the surface of a glass substrate using a thin film.

Various characteristics shown below are required for the glass substrate for the above applications (refer to Patent Document 1 if necessary).
(1) If an alkali metal oxide is contained in the glass, alkali ions diffuse into the semiconductor material on which the film is formed during the heat treatment, resulting in deterioration of the film characteristics. Do not contain.
(2) To have chemical resistance that does not deteriorate due to various acids, alkalis, and other chemicals used in the photoetching process.
(3) No thermal contraction due to heat treatment in processes such as film formation and annealing. Therefore, it must have a high strain point.
(4) The density is small in order to achieve weight reduction of the display.
(5) The thermal expansion coefficient of the peripheral member must be matched.
In consideration of meltability and moldability, this type of glass substrate is also required to have the following characteristics.
(6) The glass is excellent in meltability so as not to cause undesirable melting defects as glass substrates in the glass. There should be no bubble defects.
(7) The glass is excellent in devitrification resistance so that there is no foreign matter generated during melting and molding in the glass.

JP 2000-302475 A

  In recent years, there has been a growing demand for environmental considerations for industrial products, as seen in the enforcement of the RoHS directive in Europe. In particular, environmentally hazardous chemical substances are required to have strict regulations on the content in the product or not to be contained at all depending on the product. Even if it is a glass substrate for a display, it is not the exception of the object, and it is calculated | required to reduce the content of the environmental impact chemical substance in a glass substrate as much as possible, or not to use at all.

  Among the components contained in the glass composition, those that are regarded as a problem as an environmentally hazardous chemical include heavy metals such as Pb, Cd, and Cr, As, and Sb. As and Sb are components used as glass refining agents (foam breakers, antifoaming agents), and are suitable for glass that requires high-temperature melting such as non-alkali glass systems, but from an environmental aspect. , Its use is not preferred. In particular, As is highly toxic, its use tends to be severely restricted.

  Further, Ba, which is an alkaline earth metal component, is preferably used in a reduced amount or not at all because the raw material compound is an environmentally hazardous substance.

  Therefore, the present invention has reduced the harmful components to the environment while satisfying various properties required for glass for liquid crystal displays and the like, in particular, satisfying properties such as meltability and devitrification resistance. Alternatively, a technical problem is to design a glass composition that does not substantially contain and to obtain an environmentally friendly glass substrate.

As a result of diligent efforts, the inventors of the present invention expressed the glass composition in terms of weight% in terms of the following oxides: SiO ₂ 50 to 70%, Al ₂ O ₃ 10 to 20%, B ₂ O ₃ 8 to 12%, MgO 0. Restricted to the range of ~ 3%, CaO 4-15%, SrO 0-10%, BaO 0-1%, ZnO 0-5%, and substantially free of alkali metal oxides and As ₂ O ₃ Thus, the present inventors have found that the above problems can be solved and propose the present invention. In the present invention, “substantially does not contain an alkali metal oxide” means that it is not contained other than the amount mixed from the raw material as an impurity component. The case where the content of (Li ₂ O, Na ₂ O, K ₂ O) is 0.1% by weight or less is indicated. Further, “substantially not containing As ₂ O ₃ ” in the present invention means that it is not contained other than the amount mixed from the raw material or the like as an impurity component. In the glass composition, As ₂ O ₃ The content is 0.1 wt% or less (desirably 50 ppm or less).

  The alkali-free glass of the present invention strictly regulates the glass composition to the above component range, and can be suitably used for a liquid crystal display or a glass substrate for an organic EL display. That is, since the alkali-free glass of the present invention strictly regulates the glass composition within the above range, it is possible to satisfy the required characteristics (1) to (7). In particular, since the alkali-free glass of the present invention is excellent in meltability and devitrification resistance, the productivity of the glass substrate can be dramatically improved.

  The alkali-free glass of the present invention contains substantially no alkali metal oxide. When an alkali metal oxide is contained in a glass substrate used for an active matrix liquid crystal display or an organic EL display, an alkali component may be diffused into the TFT element formed on the surface of the glass substrate, which may cause an abnormality in performance. There is. Since the alkali-free glass of the present invention does not substantially contain an alkali metal oxide, the alkali component diffuses into the TFT element, and the performance is not impaired.

  BaO is a component that improves the chemical resistance and devitrification resistance of glass, but since it is an environmentally hazardous chemical substance, it is desirable to limit its content from an environmental point of view. The alkali-free glass of the present invention strictly restricts the BaO content, and specifically restricts the BaO content to 1% by weight or less, so that it is an environmentally friendly glass. Moreover, since the alkali-free glass of the present invention can be a glass that does not substantially contain BaO, the influence on the environment can be further reduced. Although BaO is a component that increases the density, the alkali-free glass of the present invention is advantageous from the viewpoint of reducing the density of the glass because the content of BaO is severely restricted.

In order to obtain a glass free from bubbles, it is important to select a refining agent that generates a refining gas in the temperature range from the vitrification reaction to the homogenization melting. In other words, glass clarification removes the gas generated during the vitrification reaction from the glass melt by the clarification gas, and further lifts and removes the fine bubbles remaining by the clarification gas generated again during the homogenization melting. . By the way, the alkali-free glass used for the glass substrate for liquid crystal displays has a high viscosity of the glass melt and is melted at a higher temperature than glass containing an alkali component. Conventionally, As ₂ O ₃ which generates a clarification gas in a wide temperature range (about 1200 to 1600 ° C.) has been widely used as a clarifier. However, As ₂ O ₃ is very toxic and may contaminate the environment during the glass production process or waste glass processing, and its use is being restricted. In that respect, since the alkali-free glass of the present invention does not use As ₂ O ₃ as a fining agent, it is possible to avoid as much as possible the situation of polluting the environment.

Secondly, the alkali-free glass of the present invention has a glass composition expressed in terms of weight% in terms of the following oxides: SiO ₂ 50 to 70%, Al ₂ O ₃ 10 to 20%, B ₂ O ₃ 8 to 12%. MgO 0 to 3%, CaO 4 to 15%, SrO 0 to 10%, BaO 0 to 1%, ZnO 0 to 5%, and substantially alkali metal oxides, As ₂ O ₃ and Sb ₂ Characterized by containing no O ₃ . In the present invention, “substantially does not contain Sb ₂ O ₃ ” means that it is not contained other than the amount mixed from the raw material or the like as an impurity component. In the glass composition, Sb ₂ O ₃ When the content of is 0.05% by weight or less.

Thirdly, the alkali-free glass of the present invention has a glass composition expressed in terms of weight% in terms of the following oxides: SiO ₂ 50 to 70%, Al ₂ O ₃ 10 to 20%, B ₂ O ₃ 8 to 12%. MgO 0 to 3%, CaO 4 to 15%, SrO 0 to 10%, BaO 0 to 0.2%, ZnO 0 to 5%, and substantially containing an alkali metal oxide and As ₂ O ₃ It is characterized by not containing.

Fourth, the alkali-free glass of the present invention has a glass composition, in percent by weight in terms of _{oxide, SiO 2 55~65%, Al 2} O 3 12~20%, B 2 O 3 8~12% MgO 0 to 2%, CaO 5 to 12%, SrO 1 to 10%, ZnO 0 to 5%, RO 5 to 20%, and substantially containing alkali metal oxides, BaO and As ₂ O ₃ It is characterized by not containing. Here, “RO” in the present invention refers to the total amount of MgO, CaO, SrO, and ZnO (MgO + CaO + SrO + ZnO). The term “substantially free of BaO” in the present invention means that it is not contained other than the amount mixed from the raw material as an impurity component, and the content of BaO in the glass composition is 0.00. It refers to the case of 1% by weight or less.

Fifth, the alkali-free glass of the present invention has a glass composition expressed in terms of weight% in terms of the following oxides: SiO ₂ 55 to 65%, Al ₂ O ₃ 12 to 20%, B ₂ O ₃ 8 to 12%. MgO 0 to 2%, CaO 5 to 12%, SrO 1 to 10%, ZnO 0 to 5%, RO 5 to 20%, and substantially containing alkali metal oxides, BaO and As ₂ O ₃ It is characterized by not containing.

Sixth, the alkali-free glass of the present invention has a glass composition expressed in terms of weight% in terms of the following oxides: SiO ₂ 55 to 65%, Al ₂ O ₃ 12 to 20%, B ₂ O ₃ 8 to 11%. MgO 0 to 1%, CaO 6 to 11%, SrO 3 to 10%, ZnO 0 to 5%, RO 7 to 20%, and substantially alkali metal oxides, BaO, As ₂ O ₃ and Characterized by containing no Sb ₂ O ₃ .

Seventh, the alkali-free glass of the present invention has a glass composition expressed in terms of% by weight in terms of the following oxides: SiO ₂ 55 to 65%, Al ₂ O ₃ 13 to 17%, B ₂ O ₃ 8.5. 10.5% (excluding 10.5%), MgO 0-0.5% (excluding 0.5%), CaO 6.5-11%, SrOv 3-7%, ZnO 0 It is characterized by containing ˜1%, RO 7-20% and substantially free of alkali metal oxides, BaO, As ₂ O ₃ and Sb ₂ O ₃ .

  Eighth, the alkali-free glass substrate of the present invention is characterized by being composed of the alkali-free glass described above.

  Ninth, the alkali-free glass substrate of the present invention is characterized in that the average surface roughness (Ra) is 20 mm or less. Here, “average surface roughness (Ra)” refers to a value measured by a method based on SEMI D7-94 “Measurement method of surface roughness of FPD glass substrate”.

  Tenth, the alkali-free glass substrate of the present invention is characterized in that the swell is 0.1 μm or less. Here, “swell” is a value obtained by measuring WCA (filtered center line swell) described in JIS B-0610 using a stylus type surface shape measuring device, and this measurement is based on SEMI STD D15- 1296 "Measurement method of surface waviness of FPD glass substrate" Measured with a measurement cutoff of 0.8 to 8mm and a length of 300mm in the direction perpendicular to the drawing direction of the glass substrate. It is a thing.

  Eleventh, the alkali-free glass substrate of the present invention is characterized in that the difference between the maximum thickness and the minimum thickness is 20 μm or less. Here, the “thickness difference between the maximum plate thickness and the minimum plate thickness” is the maximum plate of the glass substrate by scanning a laser from one side of the glass substrate in the plate thickness direction using a laser type thickness measuring device. The value obtained by subtracting the value of the minimum thickness from the value of the maximum thickness after measuring the thickness and the minimum thickness.

  Twelfth, the alkali-free glass substrate of the present invention is characterized in that an error with respect to the target plate thickness is 10 μm or less. Here, the “error with respect to the target plate thickness” refers to the larger one of the absolute values of the values obtained by subtracting the maximum plate thickness or the minimum plate thickness obtained by the above method from the target plate thickness.

  Thirteenth, the alkali-free glass substrate of the present invention is characterized by being used for a display.

  Fourteenth, the alkali-free glass substrate of the present invention is characterized by being used for a liquid crystal display or an organic EL display.

  Fifteenth, the alkali-free glass substrate of the present invention is characterized by being used for a liquid crystal display for a flat TV.

  Sixteenth, the method for producing an alkali-free glass substrate of the present invention is characterized in that the forming method is an overflow down-draw method (also referred to as a fusion method).

  The reason why the composition range is limited as described above will be described in detail below. In addition, the following% display points out the weight% display unless there is particular limitation.

SiO ₂ is a component that forms a network of glass, and its content is 50 to 70%, preferably 55 to 68%, more preferably 55 to 65%, still more preferably 57.5 to 61.5%, Most preferably, it is 58 to 61.5%. When the content of SiO ₂ is less than 50%, chemical resistance, particularly acid resistance is deteriorated, and it is difficult to reduce the density. On the other hand, when the content of SiO ₂ is more than 70%, the high temperature viscosity is increased, the meltability is deteriorated, the cristobalite is easily devitrified, and the defect of the devitrified foreign matter is easily generated in the glass.

Al ₂ O ₃ is a component that has an effect of increasing the strain point of glass and improves the Young's modulus of glass, and its content is 10 to 20%, preferably 12 to 18%, and more preferably 13 to 17. %, More preferably 14.5 to 17%. When the content of Al ₂ O ₃ is less than 10%, the devitrification temperature is increased, and the devitrification foreign matter of cristobalite is likely to be generated in the glass, and the strain point is likely to be lowered. On the other hand, when the content of Al ₂ O ₃ is more than 20%, the resistance to buffered hydrofluoric acid (hereinafter referred to as BHF resistance) is deteriorated, and the glass surface is likely to be clouded, and anodite is contained in the glass. SiO ₂ —Al ₂ O ₃ —RO-based devitrification tends to occur, which is not preferable.

B ₂ O ₃ is a component that acts as a flux, lowers the viscosity of the glass, and improves the meltability of the glass, and its content is 8 to 12%, preferably 8 to 11%, more preferably 8.5. -11%, more preferably 8.5 to 10.5% (excluding 10.5%), particularly preferably 9 to 10.5% (excluding 10.5%). When the content of B ₂ O ₃ is less than 8%, the function as a flux is not sufficiently exhibited, and in addition to the deterioration of BHF resistance, the devitrification resistance is also lowered. When the content of B ₂ O ₃ is more than 12%, the acid resistance tends to deteriorate in addition to the strain point being lowered and the heat resistance being lowered.

  BaO is a component that improves the chemical resistance of glass and the devitrification resistance of glass. However, since it is an environmentally hazardous chemical substance, it is desirable to limit its content from an environmental point of view. Specifically, the BaO content needs to be limited to a range of 0 to 1%, preferably 0 to 0.6%, more preferably 0 to less than 0.5%, and still more preferably 0 to 0.2%. In view of environmental considerations, it is particularly preferable to use glass that does not substantially contain BaO. When the content of BaO is more than 1%, the load on the environment increases and it is difficult to reduce the density.

  SrO is a component that improves the chemical resistance of the glass and improves the devitrification of the glass. On the other hand, SrO reduces the viscosity at high temperature, but the effect of improving the meltability is small in the entire alkaline earth metal oxide. Further, when a large amount of SrO is contained, the density and the thermal expansion coefficient tend to increase. Therefore, the content is 0 to 10%, preferably 1 to 10%, more preferably 3 to 10%, still more preferably 3 to 8%, and particularly preferably 3 to 7%. If the SrO content is more than 10%, the density and thermal expansion coefficient may be excessively increased.

  MgO is a component that lowers the high temperature viscosity of the glass and improves the melting property of the glass, and is the component that has the effect of reducing the density most among the alkaline earth metal oxides. However, if a large amount of MgO is contained, the devitrification temperature rises and the moldability deteriorates. In addition, MgO reacts with BHF to form a product, which may adhere to an element on the surface of the glass substrate or adhere to the glass substrate and cause the glass substrate to become cloudy. Therefore, it is preferable to limit the content of MgO. Specifically, the content is 0 to 3%, preferably 0 to 2%, more preferably 0 to 1.9%, and still more preferably 0. -1%, more preferably 0-0.5%, particularly preferably 0-0.5% (however, 0.5% is not included), most preferably substantially free. When the content of MgO is more than 3%, the devitrification resistance of the glass is deteriorated, and in addition to the difficulty of employing the overflow downdraw method, the BHF resistance may be deteriorated. In the present invention, “substantially free of MgO” means that it is not contained other than the amount mixed from the raw material as an impurity component, and the content of MgO in the glass composition is 0.00. It refers to the case of 1% or less.

  CaO has the effect of lowering the high temperature viscosity of the glass, improving the meltability of the glass, and improving the devitrification resistance of the glass, and is an essential component in the alkali-free glass of the present invention. CaO is a component that most improves the Young's modulus of glass among divalent alkaline earth metal oxides and suppresses the increase in glass density, and is suitable for glass substrates used in liquid crystal displays. It is a component which can provide. MgO has the same effect as CaO, but its devitrification resistance is likely to deteriorate and can be contained only in a small amount. Considering the above, it is important to make the CaO content relatively high in the alkali-free glass of the present invention. Therefore, in the alkali-free glass of the present invention, the content of CaO is 4 to 15%, preferably 5 to 12%, more preferably 6 to 11%, still more preferably 6.5 to 9%, particularly preferably. 7-9%. When the content of CaO is less than 4%, the above effects may not be sufficiently enjoyed. If the content of CaO is more than 15%, the BHF resistance is impaired, and the surface of the glass substrate is likely to be eroded. In addition, the reaction product may adhere to the surface of the glass substrate and cause the glass to become cloudy. is there.

  ZnO is a component that improves the BHF resistance of the glass and improves the meltability of the glass, but if it is incorporated in an amount of more than 5%, the glass tends to devitrify. On the other hand, when ZnO is contained in an amount of more than 5%, the strain point is lowered, making it difficult to obtain desired heat resistance. Furthermore, although ZnO does not have a great influence on the environment, it may be handled as a substance in accordance with an environmentally hazardous chemical substance. Therefore, the content is desirably as low as possible. Specifically, the content of ZnO is preferably 5% or less, more preferably 2% or less, further preferably 1% or less, particularly preferably 0.5% or less, and ideally not substantially contained. Here, “substantially free of ZnO” means that it is not contained other than the amount mixed from the raw material as an impurity component, and the content of ZnO is 0.1% or less in the glass composition. Refers to the case.

  Alkaline earth metal oxides can be mixed and contained to effectively lower the devitrification temperature of the glass, that is, it is less likely to cause crystal foreign matter in the glass, improving the meltability of the glass and the moldability of the glass. An effect is obtained. However, if these components are contained in a large amount, the density of the glass increases and it becomes difficult to reduce the weight of the glass substrate. Therefore, the total amount of these components is preferably 5 to 20%, and 8 to 15%. And is more preferably 10 to 15%. However, for the reasons already described, it is desirable that BaO and MgO are not substantially contained.

ZrO ₂ is a component that improves the chemical resistance of glass, particularly acid resistance. However, if the content of ZrO ₂ is more than 5%, the devitrification temperature rises, and devitrified foreign substances of zircon are likely to appear. It is not preferable. Therefore, the content of ZrO ₂ is preferably 0 to 5%, more preferably 0 to 1%, and still more preferably 0.01 to 0.5%. It is also possible to use the raw material for the ZrO ₂ as a main component as ZrO ₂ introduction source, but by using the elution or the like from the refractory or the like constituting the glass melting furnace, no problem be contained.

TiO ₂ is a component that improves the chemical resistance of glass, particularly acid resistance, and lowers the high-temperature viscosity to improve the meltability. TiO ₂ has an effect of preventing coloring with respect to ultraviolet rays. However, when the content of TiO ₂ is more than 3%, the glass is colored and the transmittance of the glass substrate is lowered, so that it is difficult to use for display applications. Therefore, the content of TiO ₂ is preferably a small amount, specifically 0 to 3% is preferable, and 0 to 1% is desirable.

The alkali-free glass of the present invention can contain up to 5% of other components as long as the characteristics that characterize the present invention are not impaired. For example, Y ₂ O ₃ , Nb ₂ O ₅ , WO _{3 and the} like can be contained within 5%. These components are effective for improving devitrification resistance and Young's modulus.

  The alkali-free glass of the present invention is characterized by containing substantially no alkali metal oxide. If an alkali metal oxide is contained in a glass substrate used for an active matrix liquid crystal display or an organic EL display, an alkali component may diffuse into the TFT element formed on the surface of the glass substrate, and the performance may be impaired. . Therefore, a non-alkali glass substrate that does not substantially contain an alkali metal oxide is used as the glass substrate used in these applications.

As described above, As ₂ O ₃ has been widely used as a glass fining agent, but the alkali-free glass of the present invention does not substantially contain As ₂ O ₃ from an environmental point of view. Furthermore, the alkali-free glass of the present invention preferably contains substantially no Sb ₂ O ₃ as a fining agent. Sb ₂ O ₃ is less toxic than As ₂ O ₃ , but it is an environmentally hazardous substance, so it is preferable to limit its use from an environmental point of view. Furthermore, halogens such as F and Cl are added as glass fluxes. However, since the volatiles generated when the glass melts are toxic, it is preferable to reduce the amount used and not contain them substantially. Is preferred. Here, “substantially free of halogens such as F and Cl” means that they are not contained in amounts other than the amount mixed from the raw materials as impurity components. This refers to the case where the halogen content is 0.05% or less.

The alkali-free glass of the present invention preferably uses SnO ₂ as a fining agent, and its content is preferably 0 to 1%, more preferably 0.01 to 0.5%, and more preferably 0.05 to 0.00. 3% is more preferable. SnO ₂ can generate a large number of clarification gases due to the valence change of Sn ions occurring in a high temperature range. Generally, an alkali-free glass system has a higher melting point than an alkali-containing glass, so It can be preferably used. On the other hand, if the SnO ₂ content is more than 1%, the devitrification resistance of the glass may be lowered. It is also possible to use the raw material for the SnO ₂ as a main component as SnO ₂ introduction source, but by using the elution or the like from the electrode or the like installed in a glass melting furnace, no problem be contained. Further, as will be described later, when the SnO ₂ content is large, the devitrification resistance of the glass deteriorates. Therefore, considering the devitrification resistance of the glass, the SnO ₂ content is 0.3% or less. It is preferable to do this.

So long as the glass characteristics that characterize the present invention are not impaired, SO ₃ or metal powder of C, Al, Si, or the like can be used as a fining agent. CeO ₂ , Fe ₂ O _{3 and the} like can also be used as a fining agent, but the glass may be colored, and its content is preferably 0.1% or less.

In the above glass composition range, it is naturally possible to select a preferable glass composition range by arbitrarily combining the preferable content ranges of the respective components, but there is a more preferable glass composition range as an alkali-free glass. , by weight% in terms of _{oxide, SiO 2 55~65%, Al 2} O 3 12~20%, B 2 O 3 8~12%, 0~2% MgO, CaO 5~12%, SrO An alkali-free glass characterized by containing 1 to 10%, ZnO 0 to 5%, RO 5 to 20% and substantially not containing an alkali metal oxide, BaO and As ₂ O ₃ can be mentioned.

As a more preferable composition range of the alkali-free glass, SiO ₂ 55 to 65%, Al ₂ O ₃ 12 to 20%, B ₂ O ₃ 8 to 12%, MgO 0 to 2% in terms of weight% in terms of the following oxides. , CaO 5-12%, SrO 1-10%, ZnO 0-5%, RO 5-20%, and substantially free of alkali metal oxides, BaO and As ₂ O ₃ Non-alkali glass to be used. Further, in percent by weight in terms of _{oxide, SiO 2 55~65%, Al 2} O 3 v12~20%, B 2 O 3 8~11%, 0~1% MgO, CaO 6~11%, SrO 3 to 10%, ZnO 0 to 5%, RO 7 to 20%, and containing no alkali metal oxide, BaO, As ₂ O ₃ and Sb ₂ O ₃ Glass is also suitable. Furthermore, in% by weight in terms of _{oxide, SiO 2 57.5~61.5%, Al 2} O 3 14.5~17%, B 2 O 3 8.5~11%, MgO 0~0. 5%, BaO 0-0.6%, CaO 6-9%, SrO 3-7%, ZnO 0-1% and substantially alkali metal oxides, As ₂ O ₃ and Sb ₂ O ₃ Also suitable is an alkali-free glass characterized in that it does not contain. These alkali-free glasses are excellent in meltability and devitrification resistance, so that not only can the productivity of the glass substrate be remarkably improved, but they are also suitable for the overflow down draw method with high viscosity during glass forming. .

As a particularly preferable composition range of the alkali-free glass, SiO ₂ 55 to 65%, Al ₂ O ₃ 13 to 17%, B ₂ O ₃ 8.5 to 10.5% (however, expressed in terms of weight% in terms of the following oxide) 10.5% not included), MgO 0 to 0.5% (excluding 0.5%), CaO 6.5 to 11%, SrO 3 to 7%, ZnO 0 to 1%, RO An alkali-free glass containing 7 to 20% and substantially not containing an alkali metal oxide, BaO, As ₂ O ₃ and Sb ₂ O ₃ is mentioned. Since this alkali-free glass does not substantially contain BaO, As ₂ O ₃ and Sb ₂ O ₃ , the influence on the environment can be extremely reduced, and it is suitable as a next-generation glass substrate considering the environment. Moreover, since this alkali-free glass does not substantially contain BaO, As ₂ O ₃ and Sb ₂ O ₃ , the glass substrate can be easily recycled.

  In order to form into a thin plate and stably produce a glass substrate, it is required that the glass has excellent devitrification resistance. The most typical method for forming a glass substrate used for a liquid crystal display or an organic EL display is an overflow down draw method. By using the overflow downdraw method, it is possible to form a glass substrate with a large area, a small thickness, and a very smooth surface without polishing the surface. Is suitable. On the other hand, the float method is well known as a process for forming window glass, but when this method is used to form a thin glass substrate, streaky irregularities parallel to the glass drawing direction are generated. The streaks on the glass substrate may seriously affect the image quality of the display such as image distortion and display unevenness due to a change in the thickness of the liquid crystal layer between the glass substrates. Under these circumstances, when a glass substrate molded by the float process is used as a glass substrate for an active matrix type liquid crystal display, a treatment for removing irregularities is required through a polishing process. However, the polishing process contributes to an increase in cost, and the fine scratches on the surface of the glass substrate generated by the polishing may break the electronic circuit formed on the glass substrate in the manufacturing process of the active matrix type liquid crystal display. May cause.

In order to employ the overflow downdraw method, the devitrification resistance of the glass is an important characteristic. Here, devitrification means that a crystalline foreign substance is deposited inside or on the surface of a glass in a process of forming glass by cooling a glass raw material that has become a molten liquid at a high temperature. Such a crystalline foreign substance blocks light and thus becomes a fatal defect as a glass substrate for display. In addition, the overflow downdraw method has a lower temperature during glass molding than the float method even when the same glass composition is used. Therefore, in order to apply the overflow downdraw method, it is indispensable to design a glass composition that easily causes devitrification in the glass and has good devitrification resistance. Specifically, taking into consideration the temperature at which the glass is molded, the liquidus viscosity of the glass is preferably 10 ^5.2 dPa · s or more, more preferably 10 ^5.5 dPa · s or more, and 10 ^5.8. dPa · s or more is more preferable. In terms of the liquidus temperature, it is preferably 1200 ° C. or lower, more preferably 1150 ° C. or lower, still more preferably 1100 ° C. or lower, and particularly preferably lower than 1100 ° C. If the liquid phase viscosity of the glass is less than 10 ^5.2 dPa · s, the overflow downdraw method cannot be adopted, and unreasonable restrictions are imposed on the glass forming method to ensure the surface quality of the glass substrate. It becomes difficult. Similarly, if the liquidus temperature of the glass is higher than 1200 ° C., the overflow downdraw method cannot be adopted, improper restrictions are imposed on the glass forming method, and the surface quality of the glass substrate can be ensured. It becomes difficult. Here, the “liquid phase viscosity” referred to in the present invention refers to a value obtained by measuring the viscosity of glass at a liquid phase temperature by a well-known platinum ball pulling method. The “liquid phase temperature” is obtained by crushing glass, passing through a standard sieve 30 mesh (aperture 500 μm), and putting the glass powder remaining in 50 mesh (aperture 300 μm) into a platinum boat and putting it in a temperature gradient furnace. The maximum temperature at which devitrification (crystal foreign matter) was observed in the glass was measured after holding for a period of time.

Alkali-free glass of the present invention, the following terms of oxide, the SnO ₂ containing from 0 to 0.3%, as and glass composition, until SnO ₂ is 0.3%, upon addition of SnO _2, obtained The glass liquid phase temperature is preferably 1150 ° C. or lower, more preferably 1100 ° C. or lower. If there are internal defects such as bubbles in the glass, light transmission is hindered, which is a fatal defect for a glass substrate for display. In general, as the glass substrate becomes larger, the probability that bubbles remain is increased, the probability that defects are caused by bubbles increases, and the productivity of the glass substrate decreases. Therefore, a technique for reducing bubbles in the glass is important. As a method for reducing bubbles contained in glass, there are a method of using a fining agent and a method of lowering the high temperature viscosity. In the former method, As ₂ O ₃ is the most effective as a clarifier for alkali-free glass. However, as described above, As ₂ O ₃ is an environmentally hazardous chemical, its use needs to be reduced. There is. Therefore, from the environmental point of view, the introduction of SnO ₂ as an alternative fining agent for As ₂ O ₃ has been studied. However, SnO ₂ is likely to cause crystalline foreign matter (devitrification), which is an internal defect of the glass substrate. There is a risk. Therefore, if the glass is not easily devitrified with respect to SnO ₂ , even if SnO ₂ is introduced as a clarifier, it is difficult to cause devitrification. It is possible to achieve both and is considered very effective. In addition, in the manufacturing process of the glass substrate, it is assumed that the Sn electrode is eluted to some extent in the glass. Therefore, glass that is less susceptible to devitrification with respect to SnO ₂ is further advantageous. In that respect, according to the alkali-free glass of the present invention, even if the content of SnO _{2 in} the glass composition is increased to 0.3%, the liquidus temperature of the obtained glass can be 1150 ° C. or lower. The above-mentioned effect can be enjoyed to the maximum. On the other hand, when the content of SnO _{2 in} the glass composition is 0.3%, it is difficult to receive the above effect if the liquidus temperature of the obtained glass is higher than 1150 ° C. Here, "until SnO ₂ is 0.3%, upon addition of SnO _2, the liquidus temperature of the glass to be obtained", as the batch as a raw material, SnO ₂ is 0.3% in the glass composition SnO ₂ was added until the total glass composition was 100%, and the glass was melted and molded. Thereafter, the obtained glass sample was pulverized, passed through a standard sieve 30 mesh (500 μm), and 50 mesh. The glass powder remaining at (300 μm) is placed in a platinum boat and kept in a temperature gradient furnace for 1 week, and then refers to the temperature at which crystals precipitate.

In the alkali-free glass of the present invention, when 0.5% of ZrO ₂ is added to the glass composition, the liquidus temperature of the obtained glass is preferably 1150 ° C. or lower, and more preferably 1100 ° C. or lower. As a measure for reducing the manufacturing cost of the glass substrate other than reducing internal defects such as bubbles and foreign matters, it is effective to lengthen the life of the melting kiln and reduce the frequency of repairing the kiln. As a means for that, it is preferable to use a Zr-based refractory that is not easily eroded by molten glass, but as the number of use points of the Zr-based refractory increases, Zr-based crystalline foreign matters (devitrification) are likely to occur. This may become an internal defect of the glass substrate. Therefore, if the glass is less susceptible to devitrification with respect to ZrO ₂ , even if a Zr-based refractory is used as the refractory for the melting furnace, devitrification due to this hardly occurs. Costs can be reduced and are considered very effective. In that respect, according to the alkali-free glass of the present invention, even if 0.5% of ZrO ₂ is added to the glass composition, the liquidus temperature of the obtained glass can be reduced to 1150 ° C. or lower. You can enjoy it to the fullest. On the other hand, when 0.5% of ZrO ₂ is added to the glass composition, if the liquidus temperature of the obtained glass is higher than 1150 ° C., it is difficult to receive the above effect. Here, “when 0.5% of ZrO ₂ is added to the glass composition, the liquidus temperature of the glass obtained” is the amount of ZrO ₂ added to the glass composition in an amount corresponding to 0.5% to the batch as a raw material. (The glass composition is apparently 100.5% in total.) The glass is melted and molded, and then the obtained glass sample is pulverized, passed through a standard sieve 30 mesh, and remains in 50 mesh. It refers to the temperature at which crystals precipitate after the powder is placed in a platinum boat and held in a temperature gradient furnace for 1 week.

In the alkali-free glass of the present invention, the thermal expansion coefficient is preferably 30 to 50 × 10 ⁻⁷ / ° C., more preferably 35 to 45 × 10 ⁻⁷ / ° C. Conventionally, it is desirable that the thermal expansion coefficient of an alkali-free glass substrate is consistent with the thermal expansion coefficient of a-Si or p-Si formed on the glass substrate, specifically 35 × 10. ^-7 / ° C or less has been desirable. However, glass substrates for liquid crystal displays and organic EL displays have not only a-Si or p-Si films on their surfaces, but also SiNx with a lower thermal expansion coefficient, Cr, Ta, Al, etc. with a higher thermal expansion coefficient. The metal wiring, ITO and the like are deposited. From the viewpoint of matching the thermal expansion coefficient with these members, it has been found that the thermal expansion coefficient of the alkali-free glass is not necessarily low. That is, there is an appropriate range for the thermal expansion coefficient of the alkali-free glass. Specifically, the thermal expansion coefficient is preferably 30 to 50 × 10 ⁻⁷ / ° C., more preferably 34 to 45 × 10 ⁻⁷ / ° C. 35 to 45 × 10 ⁻⁷ / ° C. is more preferable, and 36 to 40 × 10 ⁻⁷ / ° C. is particularly preferable. When the thermal expansion coefficient of the alkali-free glass is within this range, not only the thermal expansion coefficients of various films are matched, but also the thermal shock resistance can be improved. However, if the thermal expansion coefficient is out of this range, the thermal expansion coefficient cannot be matched with various films, and the thermal shock resistance may be deteriorated. The “thermal expansion coefficient in the temperature range of 30 to 380 ° C.” referred to in the present invention refers to a value obtained by measuring the average thermal expansion coefficient at 30 to 380 ° C. with a dilatometer based on JIS R3102.

In the alkali free glass of the present invention, the density is preferably 2.54 g / cm ³ or less, more preferably 2.50 g / cm ³ or less, more preferably less than ^{2.50g / cm 3, 2.47g / cm} 3 or less Is particularly preferred. Liquid crystal displays and organic EL displays are required to be thinner and lighter, and glass substrates are also required to be lighter and thinner. For this reason, a thin glass substrate having a thickness of 0.4 to 0.7 mm is mainly used as the glass substrate for these applications, but low-density glass is also required to further reduce the weight of the panel. The smaller the density of the glass substrate, the lighter the glass becomes and it is suitable for mobile device applications. However, if the density is excessively reduced, the meltability and devitrification resistance deteriorate, and foam, It is difficult to obtain a defect-free glass substrate that does not exist, and is not desirable from the viewpoint of stably producing a glass substrate such as a flat television. Therefore, considering the other properties, density, 2.40 g / cm ³ or more (preferably 2.44 g / cm ³ or more, 2.45 g / cm ³ or more) becomes a guide to design the. Here, in the present invention, “density” refers to a value measured by a well-known Archimedes method based on JIS Z8807.

  In the alkali-free glass of the present invention, the strain point is preferably 620 ° C. or higher, more preferably 630 ° C. or higher, further preferably 635 ° C. or higher, and particularly preferably 650 ° C. or higher. In the process of forming electronic circuits such as TFT and wiring, a transparent conductive film, an insulating film, a semiconductor film, a metal film, etc. are formed on a glass substrate, and various circuits and patterns are formed by a photolithography etching process. . In these film formation and photolithography etching processes, the glass substrate is subjected to various heat treatments and chemical treatments. For example, in an active matrix liquid crystal display, an insulating film or a transparent conductive film is formed on a glass substrate, and a large number of amorphous silicon or polycrystalline silicon TFTs are formed on the glass substrate through a photolithography etching process. . In these steps, the glass substrate is subjected to heat treatment at 300 to 600 ° C. By this heat treatment, the glass substrate may undergo a dimensional change of about several ppm (several μm with respect to the length of the glass substrate 1 m: this dimensional change is generally called thermal shrinkage). If the thermal shrinkage of the glass substrate is large, the TFT pattern will be displaced, and it will not be possible to accurately form an element in which multiple thin films are laminated. In order to suppress the thermal shrinkage, it is effective to increase the heat resistance of the glass, specifically to increase the strain point. However, if the strain point is raised too much, the temperature at the time of melting and forming the glass substrate rises, increasing the load on the glass production facility, which may increase the cost. Therefore, if other characteristics are taken into consideration, the strain point is designed to be 680 ° C. or lower, particularly 670 ° C. or lower.

An alkali-free glass system does not contain an alkali metal oxide that is highly effective as a flux component, and therefore requires an advanced melting technique. Examples of the method of melting an alkali-free glass system include a method of optimizing melting equipment and melting conditions such as increasing the temperature of a melting furnace and a method of lowering the melting point of glass to facilitate melting of the glass. In the latter method, as an indication of meltability of glass, there is a temperature in the high temperature viscosity ¹⁰ 2.5 dPa · s, the lower the temperature in the high temperature viscosity ¹⁰ 2.5 dPa · s, is easily dissolved glass. In the alkali-free glass of the present invention, the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is preferably 1600 ° C. or less, more preferably 1580 ° C. or less, and more preferably 1560 ° C. or less, The temperature is more preferably 1550 ° C. or lower, and particularly preferably 1540 ° C. or lower. When the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is higher than 1600 ° C., it is necessary to keep the melting kiln at a high temperature in order to melt the glass uniformly, and this is accompanied by the melting kiln such as alumina or zirconia. The refractory used is easily eroded, and as a result, the life cycle of the melting furnace is shortened, which may increase the manufacturing cost of the glass substrate. In addition, if the glass can be melted at a low temperature, the energy cost required for melting the glass can be suppressed, and the load on the environment can be reduced. The “temperature at a high temperature viscosity of 10 ^2.5 dPa · s” in the present invention refers to a value measured by a well-known platinum ball pulling method.

Alkali-free glass of the present invention, when soaked for 24 hours in 10% HCl aqueous solution 80 ° C., its erosion amount is preferably 1.0 mg / cm ² or less, 0.6 mg / cm ² or less being more preferred. Further, the alkali-free glass of the present invention, when immersed for 30 minutes in 63BHF solution of 20 ° C., its erosion amount is preferably 1.2 mg / cm ² or less, 0.9 mg / cm ² or less being more preferred. Furthermore, when the alkali-free glass of the present invention is immersed in a 63 BHF solution at 20 ° C. for 30 minutes, it is preferable that white turbidity and roughness are not observed by visual observation of the surface. A transparent conductive film, an insulating film, a semiconductor film, a metal film, and the like are formed on the surface of the glass substrate for liquid crystal display, and various circuits and patterns are formed by photolithography etching. In these film formation and photolithography etching processes, the glass substrate is subjected to various heat treatments and chemical treatments. In general, in the TFT array process, a series of processes including a film formation process, a resist pattern formation, an etching process, and a resist stripping process is repeated. At that time, in addition to receiving various chemical treatments such as sulfuric acid, hydrochloric acid, alkaline solution, hydrofluoric acid, and BHF as an etching solution, an etching step by plasma using a gas such as CF ₄ , S ₂ F ₆ , or HCl. Pass through. These chemical solutions are not disposable but are circulated liquid system flows in consideration of cost reduction. If the chemical resistance of the glass is poor, the reaction product between the chemical and the glass substrate will clog the filter of the circulating liquid system during etching, or the glass surface may become cloudy due to inhomogeneous etching, or the etching solution The change in the components may cause various problems such as an unstable etching rate. In particular, a hydrofluoric acid-based chemical solution typified by BHF erodes the glass substrate strongly, so the above-mentioned problems are likely to occur, and the glass substrate is required to have excellent BHF resistance. That is, it is very important from the viewpoint of preventing contamination of the chemical solution and clogging of the filter during the process by the reaction product that the erosion amount of the glass with respect to the chemical solution is small. In addition, regarding the chemical resistance of the glass, it is important that not only the amount of erosion is small but also the appearance change is not caused. It is an indispensable characteristic for a glass substrate for a display such as an active matrix liquid crystal display in which light transmittance is important, that the appearance of the glass does not change due to chemical treatment, such as white turbidity or roughness. The evaluation results of the amount of erosion and the change in appearance do not necessarily coincide with each other particularly with respect to BHF resistance. For example, even if the glass shows the same amount of erosion, the appearance may or may not change after chemical treatment depending on the composition. There is. In that respect, according to the alkali-free glass of the present invention, even when immersed in a 63 BHF solution at 20 ° C. for 30 minutes, the erosion amount is 1.2 mg / cm ² or less and immersed in a 63 BHF solution at 20 ° C. for 30 minutes. However, since the white turbidity and roughness cannot be recognized by visual surface observation, the above-mentioned problems can be reliably solved.

  The alkali-free glass of the present invention has a Vickers hardness of preferably 560 or more, more preferably 570 or more, and further preferably 580 or more. If the Vickers hardness is less than 560, the glass substrate is likely to be scratched, which may cause disconnection of the electronic circuit formed on the glass substrate. In addition, "Vickers hardness" as used in the field of this invention points out the value measured by the method based on JISZ2244-1992.

The alkali-free glass of the present invention preferably has a specific Young's modulus (value obtained by dividing Young's modulus by density) of 27 GPa / g · cm ⁻³ or more, more preferably 28 GPa / g · cm ⁻³ or more, and 29 GPa / g · cm. ⁻³ or more is more preferable, and 29.5 GPa / g · cm ⁻³ or more is particularly preferable. If the specific Young's modulus is 27 GPa / g · cm ⁻³ or more, even a large and thin glass substrate can be suppressed to a deflection amount that does not cause a problem. Here, “Young's modulus” refers to a value measured by a resonance method based on JIS R1602.

The alkali-free glass of the present invention preferably satisfies the relationship of T ₃ −T ₄ ≦ 330 ° C. when the temperature at 10 ⁴ dPa · s is T ₃ (° C.) and the softening point is T ₄ (° C.). . The thickness of the glass substrate and the shape of warpage and undulation in the plate width direction are substantially determined until the temperature of the molten glass reaches the softening point from the molding temperature. _Therefore, reducing the T 3 -T _4, specifically, preferably _T 3 -T ₄ of 330 ° C. or less, more preferably 325 ° C. or less, more preferably be below 320 ° C., a glass substrate thickness, the plate It becomes easier to control the shape of warpage and undulation in the width direction. Also, if regulated to T ₃ -T ₄ ≦ 330 ℃, the viscosity increases quickly upon cooling, can be quickly formed on the glass substrate shape. That is, when T ₃ -T _{4 is set} to 330 ° C. or less, a thin glass substrate can be easily formed flat. Further, when T ₃ -T _{4 is set} to 330 ° C. or less, a large glass substrate can be easily formed flat. Furthermore, in the case of downdraw molding, the furnace distance used for slow cooling is limited due to equipment design, and as a result, the slow cooling time of the glass substrate is also limited. For example, in a few minutes from the molding temperature to room temperature. Must be cooled. Thus, the above viscosity characteristics are very advantageous. On the other hand, if T ₃ -T ₄ is higher than 330 ° C., it becomes difficult to control the thickness of the glass substrate, the shape of the warp and the undulation in the plate width direction. Incidentally, T ₃ corresponds to the molding temperature.

In the glass composition range described above, it is naturally possible to limit the preferred glass composition range by arbitrarily combining preferred fining agents and preferred properties, and in that, as alkali-free glass, substantially alkali metal It does not contain oxide, Sb ₂ O ₃ and As ₂ O ₃ , and is expressed in terms of weight% in terms of the following oxides: SiO ₂ 50 to 70%, Al ₂ O ₃ 10 to 20%, B ₂ O ₃ 8 to 12 %, MgO 0 to 3%, CaO 4 to 15%, SrO 0 to 10%, BaO 0 to 1%, RO 8 to 15%, SnO ₂ 0.05 to 1% as a basic composition, and strain point Preferred is an alkali-free glass having the characteristics that the temperature is 630 ° C. or higher, the density is less than 2.50 g / cm ³ , and the liquidus viscosity is 10 ^5.2 dPa · s or higher and the temperature at 10 ^2.5 dPa · s is 1550 ° C. or lower. so is there.

As a further preferred embodiment of the alkali-free glass, substantially no alkali metal oxide, Sb ₂ O ₃ and As ₂ O ₃ are contained, and SiO ₂ 58 to 68%, Al _{2 in} terms of weight% in terms of the following oxides. Basic composition of O ₃ 14-18%, B ₂ O ₃ 9-12%, MgO 0-1.9%, CaO 4-12%, SrO 1-8%, BaO 0-1%, RO 10-15% And a strain point of 630 ° C. or higher, a density of less than 2.50 g / cm ³ , a liquid phase viscosity of 1100 ° C. or lower, and a liquid phase viscosity of 10 ^5.5 dPa · s or higher, 10 ^2.5 dPa · s. A non-alkali glass having a temperature of 1550 ° C. or lower and a specific Young's modulus of 29.5 GPa / g · cm ⁻³ or higher is preferable.

In a liquid crystal display or the like, so-called multi-sided manufacturing for producing a number of displays from a large glass substrate (called mother glass) has been performed. The required area of the glass substrate is gradually increasing. On the other hand, when the area of a glass substrate becomes large, the probability that a devitrification thing will appear in a glass substrate becomes high, and the non-defective rate of a glass substrate falls rapidly. Therefore, according to the alkali-free glass substrate of the present invention having good devitrification resistance, there is a great merit in producing a large substrate. For example, the substrate area is 0.1 m ² or more (specifically, a size of 320 mm × 420 mm or more), particularly 0.5 m ² or more (specifically, a size of 630 mm × 830 mm or more), 1.0 m ² or more ( Specifically, a size of 950 mm × 1150 mm or more, further 2.3 m ² or more (specifically, a size of 1400 mm × 1700 mm or more), 3.5 m ² or more (specifically, 1750 mm × 2050 mm or more) (Size) 4.8 m ² or more (specifically, a size of 2100 mm × 2300 mm or more), the larger the size, the more advantageous. Further, according to the alkali-free glass substrate of the present invention, in addition to being able to impart characteristics of low density and high specific Young's modulus, it is possible to accurately mold a thin glass substrate, Of 0.8 mm or less (preferably 0.7 mm or less, more preferably 0.5 mm or less, and even more preferably 0.4 mm or less), the advantages of the present invention (especially the lightening effect) can be enjoyed effectively. it can. Further, the alkali-free glass substrate of the present invention can reduce the amount of deflection of the glass substrate as compared with the conventional glass substrate even if the thickness of the glass substrate is reduced. This makes it easier to prevent breakage during loading and unloading.

  The alkali-free glass substrate of the present invention is preferably used for a liquid crystal display for a flat TV. In recent years, the screen size of a liquid crystal display for flat televisions tends to increase, and the alkali-free glass substrate of the present invention is excellent in productivity, so that the substrate area can be easily increased in size. Furthermore, since the alkali-free glass substrate of the present invention can be formed by the overflow downdraw method, a glass substrate having a good surface quality can be efficiently produced without impairing the video quality of the liquid crystal display for flat televisions. Therefore, the alkali-free glass substrate of the present invention is suitable for this application.

  The alkali-free glass substrate of the present invention preferably has an unpolished surface. The theoretical strength of glass is inherently very high, but breakage often occurs even at a stress much lower than the theoretical strength. This is because a small defect called Griffith flow occurs on the surface of the glass substrate in a post-molding process such as a polishing process. Therefore, if the surface of the glass substrate is unpolished, the mechanical strength of the original glass substrate is hardly impaired, and the glass substrate is hardly broken. Further, if the surface of the glass substrate is unpolished, the polishing process can be omitted in the glass substrate manufacturing process, so that the manufacturing cost of the glass substrate can be reduced. In the alkali-free glass substrate of the present invention, if both surfaces of the glass substrate are unpolished, the glass substrate becomes more difficult to break. Further, in the alkali-free glass substrate of the present invention, a chamfering process or the like may be applied to the cut surface of the glass substrate in order to prevent a situation from being broken from the cut surface of the glass substrate.

  In the alkali-free glass substrate of the present invention, the average surface roughness (Ra) of the glass substrate is preferably 10 mm or less, more preferably 7 mm or less, still more preferably 4 mm or less, and most preferably 2 mm or less. If the average surface roughness (Ra) is larger than 10 mm, it is difficult to accurately pattern electrodes in the manufacturing process of the liquid crystal display. As a result, the probability that the circuit electrode is disconnected or short-circuited increases. It becomes difficult to ensure reliability such as.

  In the alkali-free glass substrate of the present invention, the difference between the maximum thickness and the minimum thickness of the glass substrate is preferably 20 μm or less, more preferably 10 μm or less. If the difference between the maximum thickness and the minimum thickness of the glass substrate is larger than 20 μm, it becomes difficult to perform accurate patterning of the electrodes and the like, and as a result, the probability that the circuit electrodes are disconnected and short-circuited increases. It becomes difficult to ensure reliability.

  In the alkali-free glass substrate of the present invention, the waviness of the glass substrate is preferably 0.1 μm or less, more preferably 0.05 μm or less, still more preferably less than 0.03 μm, and most preferably 0.01 μm or less. Furthermore, ideally, it is desirable that there is substantially no swell. If the waviness is larger than 0.1 μm, it is difficult to perform accurate patterning of the electrodes and the like, and as a result, the probability that the circuit electrodes are disconnected or shorted increases, and it becomes difficult to ensure the reliability of the liquid crystal display or the like.

  In the alkali-free glass substrate of the present invention, the error with respect to the target plate thickness is preferably 10 μm or less, and more preferably 5 μm or less. If the error with respect to the target thickness of the glass substrate is larger than 10 μm, the patterning accuracy of electrodes and the like is lowered, and it becomes difficult to stably produce a high-quality liquid crystal display or the like under predetermined conditions.

  In the alkali-free glass substrate of the present invention, a glass raw material prepared so as to have a desired glass composition is put into a continuous melting furnace, the glass raw material is heated and melted, defoamed, and then supplied to a molding apparatus. Can be produced by forming the plate into a plate shape and slowly cooling it.

  From the viewpoint of manufacturing a glass substrate with good surface quality, it is preferable to form a plate by an overflow down draw method. The reason for this is that, in the case of the overflow down draw method, the surface to be the surface of the glass substrate does not come into contact with the bowl-like refractory, and is molded in a free surface state. This is because it can be molded. Here, the overflow down draw method is a method in which molten glass is overflowed from both sides of a heat-resistant bowl-shaped structure, and the overflowed molten glass is stretched and formed downward while joining at the lower end of the bowl-shaped structure. It is a method of manufacturing. The structure and material of the bowl-shaped structure are not particularly limited as long as the dimensions and surface accuracy of the glass substrate can be set in a desired state and the quality usable for the glass substrate for display can be realized. Moreover, in order to perform the downward extending | stretching shaping | molding, you may apply force with what kind of method with respect to a glass substrate. For example, a method may be employed in which a heat-resistant roll having a sufficiently large width is rotated and stretched in contact with the glass substrate, or a plurality of pairs of heat-resistant rolls are only near the end face of the glass substrate. You may employ | adopt the method of making it contact and extending | stretching. The alkali-free glass of the present invention is excellent in devitrification resistance and has a viscosity characteristic suitable for molding, so that molding by the overflow down draw method can be performed with high accuracy.

  Hereinafter, the present invention will be described in detail based on examples.

  Tables 1 to 16 show examples of the present invention (sample Nos. 1 to 79). Table 17 shows comparative examples (sample Nos. 80 and 81) of the present invention.

  Each glass sample was produced as follows. A batch prepared by mixing the raw materials in a predetermined ratio was put in a platinum crucible, melted at 1600 ° C. for 24 hours, then poured onto a carbon plate and molded into a plate shape. Various characteristics such as density, strain point, and high temperature viscosity were measured using this glass sample.

   The density was measured by a well-known Archimedes method based on JIS Z8807. The strain point, annealing point, and softening point were measured based on JIS R3103.

  As for the thermal expansion coefficient, an average thermal expansion coefficient in a temperature range of 30 to 380 ° C. was measured with a dilatometer based on JIS R3102.

The temperature at a high temperature viscosity of 10 ^4.0 poise and the temperature at a high temperature viscosity of 10 ^2.5 poise were measured using a known platinum ball pulling method.

  The liquid phase temperature is obtained by pulverizing each glass sample, passing through a standard sieve 30 mesh (aperture 500 μm), putting the glass powder remaining at 50 mesh (aperture 300 μm) into a platinum boat, and maintaining it in a temperature gradient furnace for 24 hours. Then, the maximum temperature at which devitrification (crystal foreign matter) was observed in the glass was measured. The liquid phase viscosity is a value obtained by measuring the viscosity of the glass at the liquid phase temperature by a well-known platinum ball pulling method.

The liquidus temperature when SnO ₂ is added (SnO ₂ devitrification resistance in the table) is added to the raw material batch until SnO ₂ becomes 0.3% in the glass composition, and the same conditions as above The glass is melted and molded with, then the glass sample is pulverized, passed through a standard sieve 30 mesh (500 μm), and the glass powder remaining on 50 mesh (300 μm) is placed in a platinum boat and kept in a temperature gradient furnace for 1 week. Then, the temperature at which crystals were deposited was measured. Next, “◯” indicates that no devitrification was observed at 1150 ° C., and “X” indicates that devitrification was observed at 1150 ° C. In parallel with this evaluation, when the clarity of the glass was evaluated, no bubble defects were observed in the glass when SnO ₂ was added to 0.3%.

The liquidus temperature when ZrO ₂ is added (ZrO ₂ devitrification resistance in the table) is the same as above, with ZrO ₂ being added in an amount corresponding to 0.5% in the glass composition to the raw material batch. The glass was melted and molded under the following conditions, after which the glass sample was pulverized, passed through a standard sieve 30 mesh (500 μm), and the glass powder remaining on 50 mesh (300 μm) was placed in a platinum boat and placed in a temperature gradient furnace. Holding for a week, the temperature at which crystals were deposited was measured. Next, “◯” indicates that no devitrification was observed at 1150 ° C., and “X” indicates that devitrification was observed at 1150 ° C.

  The Young's modulus was measured by a resonance method based on JIS R1602. Specific Young's modulus was calculated by dividing Young's modulus by density.

  Vickers hardness was measured by a method based on JIS Z2244-1992.

The chemical resistance was measured by the following procedure after processing each glass sample to 25 × 30 × 1 mm, optically polishing both sides. The weight W ₁ of each glass sample was measured in advance, and after immersing in a chemical solution prepared to a predetermined concentration at a predetermined temperature for a predetermined time, the weight W ₂ of each glass sample was measured again. The amount of erosion (ΔW / S) was determined by dividing the weight loss (ΔW = W ₁ -W ₂ ) by the surface area S of each glass sample before measurement. Furthermore, about each glass sample, the cloudiness of the glass surface after a chemical | medical solution process was observed. When the glass surface was clouded or cracked, “X” was given, when the glass was slightly cloudy or rough, “△” was given, and when there was no change, “◯” was given. Regarding chemical solutions and treatment conditions, acid resistance was evaluated by treatment at 80 ° C. for 24 hours using a 10% hydrochloric acid aqueous solution. BHF resistance was evaluated by treatment at 20 ° C. for 30 minutes using a 63BHF solution (HF: 6%, NH ₄ F: 30%).

Each glass sample of the example of the present invention has a density of 2.41 to 2.53 g / cm ³ , a thermal expansion coefficient of 36 to 43 × 10 ⁻⁷ / ° C., a strain point of 643 to 675 ° C., and an annealing point. 696-728 ° C., softening point 909-963 ° C., high temperature viscosity 10 ^4.0 dPa · s temperature 1215-1292 ° C. high temperature viscosity 10 ^2.5 dPa · s temperature 1475-1573 ° C., liquidus temperature The liquid phase viscosity was 10 ^5.2 to 10 ^6.1 dPa · s, the Young's modulus was 70 to 75 GPa, and the specific Young's modulus was 29 to 31 GPa / g · cm ⁻³ . Further, the erosion amount when immersed in a 10% HCl aqueous solution having a Vickers hardness of 590 to 610 and 80 ° C. for 24 hours is 0.4 to 0.6 mg / cm ² and eroded when immersed in a 63 BHF solution at 20 ° C. for 30 minutes. The amount was 0.6 to 0.8 mg / cm ² , and no change in appearance was observed. Furthermore, Sn devitrification resistance and Zr devitrification resistance were also good.

Therefore, it can be said that each glass sample according to the example of the present invention does not contain an environmentally hazardous substance or has a small content, and thus is a glass in which environmental considerations have been made. In addition, the density is 2.54 g / cm ³ or less, the glass substrate can be reduced in weight, and the thermal expansion coefficient is in the range of 35 to 45 × 10 ⁻⁷ / ° C. Since the consistency is good and the strain point is 640 ° C. or higher, the glass is unlikely to thermally shrink in the heat treatment process in the display manufacturing process. Furthermore, since the liquidus temperature is 1200 ° C. or less and the liquidus viscosity is 10 ^5.2 dPa · s or more, the glass has excellent devitrification resistance and glass moldability, Since the temperature at a high temperature viscosity of 10 ^2.5 dPa · s was 1580 ° C. or lower, the glass was excellent in melting and moldability, and further excellent in chemical resistance, particularly BHF resistance and acid resistance.

  The glass sample No. of the comparative example of this invention. No. 80 was inferior in devitrification resistance and chemical resistance. Moreover, the glass sample No. of the comparative example of this invention. Since 81 contains 2.5% of BaO, there is a concern about the influence on the environment.

  Further, Example Sample No. 44 glass was melted in a test melting furnace and formed into a glass substrate by an overflow down draw method to produce a glass substrate for display having a substrate size of 900 mm × 1100 mm and a thickness of 0.5 mm. The warp of this glass substrate was 0 0.05% or less, waviness (WCA) of 0.1 μm or less, surface roughness (Ra) of 50 mm or less (cut-off λc: 9 μm), excellent surface quality, and suitable as a glass substrate for LCD . In addition, when forming by the overflow downdraw method, the speed of the pulling roller, the speed of the cooling roller, the temperature distribution of the heating device, the temperature of the molten glass, the flow rate of the glass, the drawing speed, the rotation speed of the stirring stirrer, etc. should be adjusted appropriately. Thus, the surface quality of the glass substrate was adjusted. “Warpage” is measured by placing a glass substrate on an optical surface plate and using a clearance gauge described in JIS B-7524. “Waviness” is a value obtained by measuring WCA (filtered center line waviness) described in JIS B-0610 using a stylus type surface shape measuring device. This measurement is performed by SEMI STD D15-1296 “FPD”. Measured by a method in accordance with “Measurement method of surface waviness of glass substrate”, cut-off at the time of measurement is 0.8 to 8 mm, measured at a length of 300 mm in a direction perpendicular to the drawing direction of the glass substrate. is there. “Average surface roughness (Ra)” is a value measured by a method based on SEMI D7-94 “Method for measuring surface roughness of FPD glass substrate”.

  The alkali-free glass of the present invention can be a glass having a small content of environmentally hazardous substances and substantially free of environmentally hazardous substances. Therefore, the alkali-free glass of the present invention is an environment-friendly glass, and can be used as a next-generation glass substrate because it can easily recycle the glass raw material and is less likely to cause environmental pollution. be able to.

Therefore, the alkali-free glass of the present invention is suitable as a display substrate such as a liquid crystal display and an organic EL display, a cover glass such as a solid-state imaging device such as a CMOS, and a substrate such as a filter and a sensor.

As a result of diligent efforts, the inventors of the present invention expressed the glass composition in terms of weight% in terms of the following oxides: SiO ₂ 50 to 70%, Al ₂ O ₃ 10 to 20%, B ₂ O ₃ 8 to 12%, MgO 0. ~3%, CaO 4~15%, SrO 0~10%, BaOv0~1%, 0~5% ZnO, alkaline earth metal oxides _{11.2~20%, ZrO 2 0~0.5%,} SnO ₂ It is found that the above problems can be solved by restricting the content to 0.01 to 1% and substantially not containing an alkali metal oxide , As ₂ O ₃ and Sb ₂ O _3, and proposes the present invention. Is. In the present invention, “substantially does not contain an alkali metal oxide” means that it is not contained other than the amount mixed from the raw material as an impurity component. The case where the content of (Li ₂ O, Na ₂ O, K ₂ O) is 0.1% by weight or less is indicated. Further, “substantially not containing As ₂ O ₃ ” in the present invention means that it is not contained other than the amount mixed from the raw material or the like as an impurity component. In the glass composition, As ₂ O ₃ The content is 0.1 wt% or less (desirably 50 ppm or less).

The alkali-free glass of the present invention has a glass composition expressed in terms of weight% in terms of the following oxides: SiO ₂ 50 to 70%, Al ₂ O ₃ 10 to 20%, B ₂ O ₃ 8 to 12%, MgO 0 to 3%, CaO 4-15%, SrOv 0-10%, BaO 0-1%, ZnO 0-5% , alkaline earth metal oxide 11.2-20%, ZrO ₂ 0-0.5 %, SnO ₂ contains 0.01% to 1%, and substantially alkali metal oxide, it is preferable free of _as 2 _{O 3} and _Sb 2 _{O 3.} In the present invention, “substantially does not contain Sb ₂ O ₃ ” means that it is not contained other than the amount mixed from the raw material or the like as an impurity component. In the glass composition, Sb ₂ O ₃ When the content of is 0.05% by weight or less.

The alkali-free glass of the present invention has a glass composition expressed in terms of weight% in terms of the following oxides: SiO ₂ 50 to 70%, Al ₂ O ₃ 10 to 20%, B ₂ O ₃ 8 to 12%, MgO 0 to 3%, CaO 4~15%, SrO 0~10%, BaO 0~0.2%, 0~5% ZnO, alkaline earth metal oxides _11.2~20%, ZrO 2 _0~0.5% It is preferable that SnO ₂ is contained in an amount of 0.01 to 1% and substantially no alkali metal oxide , As ₂ O ₃ and Sb ₂ O ₃ are contained.

The alkali-free glass of the present invention has a glass composition expressed in terms of weight% in terms of the following oxides: SiO ₂ 55 to 65%, Al ₂ O ₃ 12 to 20%, B ₂ O ₃ 8 to 12%, MgO 0 to 2%, CaO 5-12%, SrO 1-10%, ZnO 0-5%, alkaline earth metal oxide 11.2-20%, ZrO ₂ 0-0.5 %, SnO ₂ 0.01-1 % , And substantially no alkali metal oxides, BaO ₂ , As ₂ O ₃ and Sb ₂ O ₃ are preferably contained. In here, the term "substantially free of BaO" the present invention, a means that does not include other than that coming mixed from raw materials as an impurity component in the glass composition, the content of BaO It refers to the case of 0.1% by weight or less.

The alkali-free glass of the present invention has a glass composition expressed in terms of weight% in terms of the following oxides: SiO ₂ 55 to 65%, Al ₂ O ₃ 12 to 20%, B ₂ O ₃ 8 to 12%, MgO 0 to 2%, CaO 5-12%, SrO 1-10%, ZnO 0-5%, alkaline earth metal oxide 11.2-20%, ZrO ₂ 0-0.5 %, SnO ₂ 0.01-1 % containing, and substantially alkali metal oxide, preferably contains no BaO and _as 2 _{O 3.}

The alkali-free glass of the present invention has a glass composition expressed in terms of weight% in terms of the following oxides: SiO ₂ 55 to 65%, Al ₂ O ₃ 12 to 20%, B ₂ O ₃ 8 to 11%, MgO 0 to 1%, CaO 6-11%, SrO 3-10%, ZnO 0-5%, alkaline earth metal oxide 11.2-20%, ZrO ₂ 0-0.5 %, SnO ₂ 0.01-1 % containing, and substantially alkali metal oxide, BaO, it is preferred that free of _as 2 _{O 3} and _Sb 2 _{O 3.}

The alkali-free glass of the present invention has a glass composition expressed in terms of weight% in terms of the following oxides: SiO ₂ 55 to 65%, Al ₂ O ₃ 13 to 17%, B ₂ O ₃ 8.5 to 10.5%. (However, 10.5% is not included), MgO 0-0.5% (however, 0.5% is not included), CaO 6.5-11%, SrO 3-7%, ZnO 0-1% , Alkaline earth metal oxides 11.2-20%, ZrO ₂ 0-0.5%, SnO ₂ 0.01-1% , and substantially alkali metal oxides, BaO, As ₂ O ₃ And Sb ₂ O ₃ is preferably not contained.

The alkali-free glass substrate of the present invention is preferably composed of the alkali-free glass described above.

The alkali-free glass substrate of the present invention preferably has an average surface roughness (Ra) of 20 mm or less. Here, “average surface roughness (Ra)” refers to a value measured by a method based on SEMI D7-94 “Measurement method of surface roughness of FPD glass substrate”.

The alkali-free glass substrate of the present invention preferably has a swell of 0.1 μm or less. Here, “swell” is a value obtained by measuring WCA (filtered center line swell) described in JIS B-0610 using a stylus type surface shape measuring device, and this measurement is based on SEMI STD D15- 1296 "Measurement method of surface waviness of FPD glass substrate" Measured with a measurement cutoff of 0.8 to 8mm and a length of 300mm in the direction perpendicular to the drawing direction of the glass substrate. It is a thing.

In the alkali-free glass substrate of the present invention, the difference between the maximum plate thickness and the minimum plate thickness is preferably 20 μm or less. Here, the “thickness difference between the maximum plate thickness and the minimum plate thickness” is the maximum plate of the glass substrate by scanning a laser from one side of the glass substrate in the plate thickness direction using a laser type thickness measuring device. The value obtained by subtracting the value of the minimum thickness from the value of the maximum thickness after measuring the thickness and the minimum thickness.

Alkali-free glass substrate of the present invention is preferably an error with respect to the target plate thickness is 10μm or less. Here, the “error with respect to the target plate thickness” refers to the larger one of the absolute values of the values obtained by subtracting the maximum plate thickness or the minimum plate thickness obtained by the above method from the target plate thickness.

The alkali-free glass substrate of the present invention is preferably used for a display.

The alkali-free glass substrate of the present invention is preferably used for a liquid crystal display or an organic EL display.

The alkali-free glass substrate of the present invention is preferably used for a liquid crystal display for a flat TV.

In the method for producing an alkali-free glass substrate of the present invention, the forming method is preferably an overflow down draw method (also referred to as a fusion method).

Alkaline earth metal oxides can be mixed and contained to effectively lower the devitrification temperature of the glass, that is, it is less likely to cause crystal foreign matter in the glass, improving the meltability of the glass and the moldability of the glass. An effect is obtained. However, if a large amount of these components is contained, the density of the glass increases, making it difficult to reduce the weight of the glass substrate . Therefore, the total amount of these components is preferably 11.2 to 20% . It is preferable to set it as 2 to 15%, and it is more preferable to set it as 11.2 to 15%. However, for the reasons already described, it is desirable that BaO and MgO are not substantially contained.

ZrO ₂ is a component that improves the chemical resistance of glass, particularly acid resistance. However, if the content of ZrO ₂ is more than 5%, the devitrification temperature rises, and devitrified foreign substances of zircon are likely to appear. It is not preferable. Accordingly, the content of ZrO ₂ is 0 preferably 0.5%, 0 is more preferably 0.5%, even more preferably 0.01-0.5%. It is also possible to use the raw material for the ZrO ₂ as a main component as ZrO ₂ introduction source, but by using the elution or the like from the refractory or the like constituting the glass melting furnace, no problem be contained.

As described above, As ₂ O ₃ has been widely used as a glass fining agent, but the alkali-free glass of the present invention does not substantially contain As ₂ O ₃ from an environmental point of view. Furthermore, the alkali-free glass of the present invention does not substantially contain S b ₂ O ₃ as a fining agent. Sb ₂ O ₃ is less toxic than As ₂ O ₃ , but it is an environmentally hazardous substance, so it is preferable to limit its use from an environmental point of view. Furthermore, halogens such as F and Cl are added as glass fluxes. However, since the volatiles generated when the glass melts are toxic, it is preferable to reduce the amount used and not contain them substantially. Is preferred. Here, “substantially free of halogens such as F and Cl” means that they are not contained in amounts other than the amount mixed from the raw materials as impurity components. This refers to the case where the halogen content is 0.05% or less.

Alkali-free glass of the present invention, as a fining agent, it is preferred to use SnO _2, the content thereof is from 0.01 to 1%, 0.01-0.5% virtuous preferred, 0.05 -0.3% is still more preferable. SnO ₂ can generate a large number of clarification gases due to the valence change of Sn ions occurring in a high temperature range. Generally, an alkali-free glass system has a higher melting point than an alkali-containing glass, so It can be preferably used. On the other hand, if the SnO ₂ content is more than 1%, the devitrification resistance of the glass may be lowered. It is also possible to use the raw material for the SnO ₂ as a main component as SnO ₂ introduction source, but by using the elution or the like from the electrode or the like installed in a glass melting furnace, no problem be contained. Further, as will be described later, when the SnO ₂ content is large, the devitrification resistance of the glass deteriorates. Therefore, considering the devitrification resistance of the glass, the SnO ₂ content is 0.3% or less. It is preferable to do this.

In the above glass composition range, it is naturally possible to select a preferable glass composition range by arbitrarily combining the preferable content ranges of the respective components, but there is a more preferable glass composition range as an alkali-free glass. , by weight% in terms of _{oxide, SiO 2 55~65%, Al 2} O 3 12~20%, B 2 O 3 8~12%, 0~2% MgO, CaO 5~12%, SrO 1 to 10%, ZnO 0 to 5%, alkaline earth metal oxide 11.2 to 20%, ZrO ₂ 0 to 0.5%, SnO ₂ 0.01 to 1% , and substantially alkaline An alkali-free glass characterized by not containing a metal oxide, BaO ₂ , As ₂ O _3, and Sb ₂ O ₃ may be mentioned.

As a more preferable composition range of the alkali-free glass, SiO ₂ 55 to 65%, Al ₂ O ₃ 12 to 20%, B ₂ O ₃ 8 to 12%, MgO 0 to 2% in terms of weight% in terms of the following oxides. CaO 5-12%, SrO 1-10%, ZnO 0-5%, alkaline earth metal oxide 11.2-20%, ZrO ₂ 0-0.5 %, SnO ₂ 0.01-1% Examples include alkali-free glass that contains and substantially does not contain an alkali metal oxide, BaO ₂ , As ₂ O _3, and Sb ₂ O ₃ . Further, in percent by weight in terms of _{oxide, SiO 2 55~65%, Al 2} O 3 12~20%, B 2 O 3 8~11%, 0~1% MgO, CaO 6~11%, SrO 3-10%, ZnO 0-5%, alkaline earth metal oxide 11.2-20%, ZrO ₂ 0-0.5 %, SnO ₂ 0.01-1% and substantially alkaline An alkali-free glass characterized by not containing a metal oxide, BaO, As ₂ O ₃ and Sb ₂ O ₃ is also suitable. Furthermore, in% by weight in terms of _{oxide, SiO 2 57.5~61.5%, Al 2} O 3 14.5~17%, B 2 O 3 8.5~11%, MgO 0~0. 5%, BaO 0-0.6%, CaO 6-9%, SrO 3-7%, ZnO 0-1% , alkaline earth metal oxide 11.2-20%, ZrO ₂ 0-0.5 % Also preferred is an alkali-free glass characterized by containing 0.01 to 1% of SnO ₂ and substantially free of alkali metal oxides, As ₂ O ₃ and Sb ₂ O ₃ . These alkali-free glasses are excellent in meltability and devitrification resistance, so that not only can the productivity of the glass substrate be remarkably improved, but they are also suitable for the overflow down draw method with high viscosity during glass forming. .

As a particularly preferable composition range of the alkali-free glass, SiO ₂ 55 to 65%, Al ₂ O ₃ 13 to 17%, B ₂ O ₃ 8.5 to 10.5% (however, expressed in terms of weight% in terms of the following oxide) 10.5% not included), MgO 0 to 0.5% (not including 0.5%), CaO 6.5 to 11%, SrO 3 to 7%, ZnO 0 to 1%, alkali Earth metal oxides 11.2-20%, ZrO ₂ 0-0.5%, SnO ₂ 0.01-1% and substantially alkali metal oxides, BaO, As ₂ O ₃ and Sb An alkali-free glass characterized by not containing ₂ O ₃ is mentioned. Since this alkali-free glass does not substantially contain BaO, As ₂ O ₃ and Sb ₂ O ₃ , the influence on the environment can be extremely reduced, and it is suitable as a next-generation glass substrate considering the environment. Moreover, since this alkali-free glass does not substantially contain BaO, As ₂ O ₃ and Sb ₂ O ₃ , the glass substrate can be easily recycled.

In the glass composition range described above, it is naturally possible to limit the preferred glass composition range by arbitrarily combining preferred fining agents and preferred properties, and in that, as alkali-free glass, substantially alkali metal It does not contain oxide, Sb ₂ O ₃ and As ₂ O ₃ , and is expressed in terms of weight% in terms of the following oxides: SiO ₂ 50 to 70%, Al ₂ O ₃ 10 to 20%, B ₂ O ₃ 8 to 12 %, MgO 0 to 3%, CaO 4 to 15%, SrO 0 to 10%, BaO 0 to 1%, alkaline earth metal oxide 11.2 to 20%, ZrO ₂ 0 to 0.5%, SnO ₂ It contains 0.05 to 1% as a basic composition, has a strain point of 630 ° C. or higher, a density of less than 2.50 g / cm ³ , and a liquidus viscosity of 10 ^5.2 dPa · s or more and 10 ^2.5 dPa · s. The temperature at s is 15 An alkali-free glass having a characteristic of 50 ° C. or less is preferred.

As a further preferred embodiment of the alkali-free glass, substantially no alkali metal oxide, Sb ₂ O ₃ and As ₂ O ₃ are contained, and SiO ₂ 58 to 68%, Al _{2 in} terms of weight% in terms of the following oxides. 10. O ₃ 14-18%, B ₂ O ₃ 9-12%, MgO 0-1.9%, CaO 4-12%, SrO 1-8%, BaO 0-1%, alkaline earth metal oxide. 2 to 20%, ZrO ₂ 0 to 0.5% as a basic composition, a strain point of 630 ° C. or higher, a density of less than 2.50 g / cm ³ , a liquid phase viscosity of 1100 ° C. or lower, and a liquid phase viscosity of An alkali-free glass having characteristics such that the temperature at 10 ^5.5 dPa · s or more and 10 ^2.5 dPa · s is 1550 ° C. or less and the specific Young's modulus is 29.5 GPa / g · cm ⁻³ or more is suitable.

Tables 1 to 16 show examples of the present invention (Sample Nos. 1 to 10, 38 to 45, and 73 to 79). Table 17 shows comparative examples (sample Nos. 80 and 81) of the present invention. Sample No. Reference numerals 11 to 37 and 46 to 72 are reference examples.

Claims (16)

As a glass composition, in percent by weight in terms of _{oxide, SiO 2 50~70%, Al 2} O 3 10~20%, B 2 O 3 8~12%, 0~3% MgO, CaO 4~15% , SrO 0 to 10%, BaO 0 to 1%, ZnO 0 to 5%, and containing no alkali metal oxide and As ₂ O ₃ substantially. As a glass composition, in percent by weight in terms of _{oxide, SiO 2 50~70%, Al 2} O 3 10~20%, B 2 O 3 8~12%, 0~3% MgO, CaO 4~15% , SrO 0 to 10%, BaO 0 to 1%, ZnO 0 to 5%, and substantially free of alkali metal oxides, As ₂ O ₃ and Sb ₂ O ₃ Glass. As a glass composition, in percent by weight in terms of _{oxide, SiO 2 50~70%, Al 2} O 3 10~20%, B 2 O 3 8~12%, 0~3% MgO, CaO 4~15% , SrO 0 to 10%, BaO 0 to 0.2%, ZnO 0 to 5%, and substantially free of alkali metal oxide and As ₂ O ₃ . As a glass composition, in percent by weight in terms of _{oxide, SiO 2 55~65%, Al 2} O 3 12~20%, B 2 O 3 8~12%, 0~2% MgO, CaO 5~12% , SrO 1 to 10%, ZnO 0 to 5%, RO 5 to 20%, and substantially free of alkali metal oxides, BaO and As ₂ O ₃ . As a glass composition, in percent by weight in terms of _{oxide, SiO 2 55~65%, Al 2} O 3 12~20%, B 2 O 3 8~12%, 0~2% MgO, CaO 5~12% , SrO 1 to 10%, ZnO 0 to 5%, RO 5 to 20%, and substantially free of alkali metal oxides, BaO and As ₂ O ₃ . As a glass composition, in percent by weight in terms of _{oxide, SiO 2 55~65%, Al 2} O 3 12~20%, B 2 O 3 8~11%, 0~1% MgO, CaO 6~11% , SrO 3 to 10%, ZnO 0 to 5%, RO 7 to 20%, and substantially free of alkali metal oxides, BaO, As ₂ O ₃ and Sb ₂ O ₃ Alkali-free glass. As a glass composition, in percent by weight in terms of _{oxide, SiO 2 55~65%, Al 2} O 3 13~17%, B 2 O 3 8.5~10.5% ( however, 10.5% Not included), MgO 0 to 0.5% (excluding 0.5%), CaO 6.5 to 11.5%, SrO 3 to 7%, ZnO 0 to 1%, RO 7 to 20% And an alkali-free glass characterized by substantially not containing an alkali metal oxide, BaO, As ₂ O ₃ and Sb ₂ O ₃ .   An alkali-free glass substrate comprising the alkali-free glass according to claim 1.   9. The alkali-free glass substrate according to claim 8, wherein the average surface roughness (Ra) is 20 mm or less.   10. The alkali-free glass substrate according to claim 8, wherein the swell is 0.1 μm or less.   The alkali-free glass substrate according to any one of claims 8 to 10, wherein a difference in plate thickness between the maximum plate thickness and the minimum plate thickness is 20 µm or less.   The alkali-free glass substrate according to any one of claims 8 to 11, wherein an error with respect to the target plate thickness is 10 µm or less.   It uses for a display, The alkali free glass substrate in any one of Claims 8-12 characterized by the above-mentioned.   It uses for a liquid crystal display or an organic electroluminescent display, The alkali free glass substrate in any one of Claims 8-13 characterized by the above-mentioned.   It uses for the liquid crystal display for flat televisions, The alkali free glass substrate in any one of Claims 8-14 characterized by the above-mentioned. The method for producing an alkali-free glass substrate according to any one of claims 8 to 15, wherein the forming method is an overflow down draw method.