JP6172481B2 - Glass substrate and manufacturing method thereof - Google Patents

Description

  The present invention relates to glass and a glass substrate, and specifically relates to glass and a glass substrate suitable for an organic EL (OLED) display and a liquid crystal display. Further, the present invention relates to a glass and a glass substrate suitable for an oxide TFT, a low temperature p-Si.TFT (LTPS) driven display.

  Conventionally, glass substrates have been widely used as substrates for flat panel displays such as liquid crystal displays, hard disks, filters and sensors. In recent years, in addition to conventional liquid crystal displays, OLED displays have been actively developed for reasons such as self-emission, high color reproducibility, high viewing angle, high-speed response, and high definition, and some have already been put into practical use. Has been. In addition, since the display of a mobile device such as a smartphone has a small area, it is required to display a large amount of information. Therefore, an ultra-high-definition screen is required and a moving image is displayed. I need it.

  In such applications, an OLED display or a liquid crystal display driven by LTPS is suitable. An OLED display emits light when a current flows through an OLED element constituting a pixel. For this reason, a material having low resistance and high electron mobility is used as the driving TFT element. As this material, in addition to the above LTPS, an oxide TFT typified by IGZO (indium, gallium, zinc oxide) has attracted attention. An oxide TFT has low resistance and high mobility, and can be formed at a relatively low temperature. Conventional p-Si TFTs, especially LTPS, form elements on a large-area glass substrate due to the instability of an excimer laser used when polycrystallizing an amorphous Si (a-Si) film. In this case, the TFT characteristics are likely to vary, and screen display unevenness is likely to occur in TV applications. On the other hand, an oxide TFT has been attracting attention as an effective TFT forming material when it is formed on a glass substrate having a large area, and thus has attracted attention as a powerful TFT forming material.

  Glass substrates used for high-definition displays have many required characteristics. In particular, the following characteristics (1) to (5) are required.

(1) When the alkali component in the glass is large, alkali ions are diffused into the semiconductor material on which the film is formed during the heat treatment, and the film characteristics are deteriorated. Therefore, the content of alkali components (particularly, Li component and Na component) is small or not substantially contained.
(2) Various chemicals such as acid and alkali are used in the photolithography etching step. Therefore, it has excellent chemical resistance.
(3) The glass substrate is heat-treated at several hundred degrees Celsius in steps such as film formation and annealing. When the glass substrate is thermally contracted during the heat treatment, pattern deviation or the like is likely to occur. Therefore, heat shrinkage is difficult, especially the strain point is high.
(4) The thermal expansion coefficient is close to a member (for example, a-Si, p-Si) formed on the glass substrate. For example, the thermal expansion coefficient is 30 to 40 × 10 ⁻⁷ / ° C. When the thermal expansion coefficient is 40 × 10 ⁻⁷ / ° C. or less, the thermal shock resistance is also improved.
(5) The Young's modulus (or specific Young's modulus) is high in order to suppress problems caused by the bending of the glass substrate.

Furthermore, from the viewpoint of manufacturing a glass substrate, the following properties (6) and (7) are required for glass.
(6) Excellent meltability in order to prevent melting defects such as bubbles, blisters and striae.
(7) Excellent devitrification resistance to avoid generation of foreign matter in the glass substrate.

  The present invention has been made in view of the above circumstances, and its technical problem is that it satisfies the above required characteristics (1) to (7) and is suitable for OLED displays and liquid crystal displays driven by LTPS and oxide TFT elements. And to create a glass substrate. Specifically, it is to create a glass and a glass substrate having a low alkali component, a low density and a low thermal expansion coefficient, a high strain point and a Young's modulus, and excellent in devitrification resistance, meltability, moldability, and the like. .

As a result of repeating various experiments, the present inventors have found that the above technical problem can be solved by regulating the glass composition within a predetermined range, and propose the present invention. That is, the glass of the present invention has a glass composition, in _{mass%, SiO 2 58~70%, Al} 2 O 3 16~25%, B 2 O 3 3~8%, 0~5% MgO, CaO 3~ 13%, SrO 0-6%, BaO 0-6%, ZnO 0-5%, ZrO ₂ 0-5%, TiO ₂ 0-5%, P ₂ O ₅ 0-5% To do.

The present inventors have used SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ —RO (RO: alkaline earth metal oxide, MgO + CaO + SrO + BaO) glass as a glass that satisfies the above required characteristics (1) to (7). If the content of SiO ₂ is regulated to 58% or more, the content of Al ₂ O ₃ to 16 to 25%, and the content of B ₂ O ₃ to 3 to 8%, high strain point and good resistance It has been found that chemical properties can be compatible. Further, it has been found that if the contents of SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ and RO are optimized, Young's modulus, devitrification resistance and the like are improved. _Further, B ₂ O 3, MgO, if appropriate the content of CaO, meltability, moldability, found that devitrification resistance and the like are improved.

Second, the glass of the present invention has a glass composition, in _{mass%, SiO 2 58~70%, Al} 2 O 3 16~25%, B 2 O 3 3~8%, 0~5% MgO, CaO _{3~13%, SrO 0~6%, BaO} 0~6%, 0~5% ZnO, containing _{ZrO 2 0~5%, TiO 2 0~5} %, the _P 2 O 5 _0~5%, substantially In particular, it does not contain a Li component or Na component, has a density of 2.43 to 2.52 g / cm ³ , and a strain point of 680 ° C. or higher. Here, “substantially does not contain” refers to the case where the content of the explicit component is 0.1% or less (preferably 0.05% or less), for example, “substantially contains no Li component. "" Refers to the case where the content of the Li component is 0.1% or less (preferably 0.05% or less). “Density” can be measured by the well-known Archimedes method. “Strain point” refers to a value measured based on the method of ASTM C336.

Third, the glass of the present invention contains substantially no Li component or Na component, a density of 2.43 to 2.52 g / cm ³ , and a thermal expansion coefficient of 30 to 40 × 10 ⁻⁷ / ° C. Young's modulus is 75 GPa or more, strain point is 680 ° C. or more and less than 740 ° C., temperature at 10 ^5.0 dPa · s is 1250 ° C. or less, temperature at 10 ^2.5 dPa · s is 1650 ° C. or less, liquid viscosity (liquid phase (Linear viscosity) is 10 ^5.0 dPa · s or more. Here, the “thermal expansion coefficient” refers to an average thermal expansion coefficient measured in a temperature range of 30 to 380 ° C., and can be measured by, for example, a dilatometer. “Young's modulus” refers to a value measured by a dynamic elastic modulus measurement method (resonance method) based on JIS R1602. “Temperature at 10 ^5.0 dPa · s” can be measured by, for example, a platinum ball pulling method. “Temperature at 10 ^2.5 dPa · s” can be measured, for example, by a platinum ball pulling method. “Liquid phase viscosity” refers to the viscosity of glass at the liquid phase temperature (liquidus temperature), and can be measured by, for example, a platinum ball pulling method. “Liquid phase temperature” is obtained by passing the standard sieve 30 mesh (500 μm) and putting the glass powder remaining in 50 mesh (300 μm) into a platinum boat and holding it in a temperature gradient furnace for 24 hours, then removing the platinum boat, The temperature at which devitrification (crystal foreign matter) is observed in the glass.

Fourth, the glass of the present invention has a glass composition, in _{mass%, SiO 2 59~67%, Al} 2 O 3 17~22%, B 2 O 3 4~7%, 0~4% MgO, CaO _{3~12%, SrO 0~5%, BaO} 0.1~5%, 0~5% ZnO, ZrO 2 0~5%, TiO 2 0~5%, P 2 O 5 0~5%, SnO 2 It is preferable to contain 0 to 5% and substantially not contain the Li component and the Na component.

Fifth, the glass of the present invention has a glass composition of mass%, SiO ₂ 60-65%, Al ₂ O ₃ 17-20%, B ₂ O ₃ 4-7%, MgO 0-3%, CaO. 4 to 10%, SrO 0 to 5%, BaO 0.1 to 5%, ZnO 0 to 1%, ZrO ₂ 0 to 1%, TiO ₂ 0 to 1%, P ₂ O ₅ 0 to 3%, SnO ₂ It is preferable to contain 0.01 to 1%, and to contain substantially no Li component and Na component.

  Sixth, the glass substrate of the present invention comprises any one of the above glasses.

  Seventh, the glass substrate of the present invention is preferably used for an OLED display. Eighth, the glass substrate of the present invention is preferably used for a liquid crystal display.

  Ninth, the glass substrate of the present invention is preferably used for an oxide TFT-driven display.

It is the schematic for demonstrating the measuring method of a heat contraction value.

  The reason why the content of each component is regulated as described above will be described below. In addition, in description of each component, the following% display points out the mass%.

When the content of SiO ₂ is too small, chemical resistance, particularly acid resistance is lowered, strain point is lowered, and it is difficult to lower the density. On the other hand, when the content of SiO ₂ is too large, the high-temperature viscosity becomes high and the meltability is liable to decrease, and the devitrification of cristobalite easily occurs, and the defect of devitrified foreign matter is likely to occur in the glass. The preferable upper limit content of SiO ₂ is 70%, 68%, 66%, 65%, particularly 64%, and the preferable lower limit content is 58%, 59%, 60%, particularly 61%. The most preferable content range is 61 to 64%.

When the content of Al ₂ O ₃ is too small, the strain point is lowered, the thermal shrinkage value increases, and the Young's modulus decreases, easily bending glass substrate. On the other hand, when the content of Al ₂ O ₃ is too large, and Resistance BHF (buffered hydrofluoric acid) is reduced, with white turbidity on the glass surface is likely to occur, crack resistance tends to decrease. Further, vitrition of mullite or anorthite easily occurs in the glass. The preferable upper limit content of Al ₂ O ₃ is 25%, 23%, 22%, 21%, particularly 20%, and the preferable lower limit content is 17%, 17.5%, particularly 18%. The most preferable content range is 18 to 20%.

B ₂ O ₃ is a component that works as a flux and lowers viscosity to improve meltability. The content of B ₂ O ₃ is preferably 3 to 8%, 3 to 7%, particularly 4 to 7%. When B ₂ O ₃ content is too small, it does not act sufficiently as a flux, the BHF resistance and crack resistance tends to decrease. Also, the liquidus temperature tends to increase. On the other hand, when the content of B ₂ O ₃ is too large, the strain point, heat resistance, acid resistance tends to decrease. In particular, when the content of B ₂ O ₃ is 7% or more, the tendency becomes remarkable. Further, when the content of B ₂ O ₃ is too large, reduced Young's modulus, easily bending of the glass substrate is increased.

Considering the balance between strain point and meltability, the mass ratio Al ₂ O ₃ / B ₂ O ₃ is preferably 1 to 5, 1.5 to 4.5, _{2 to} 4, particularly 2.5 to 3.5. It is.

  MgO is a component that improves the meltability by lowering the high temperature viscosity without lowering the strain point. MgO has the effect of reducing the density most in RO, but if it is introduced excessively, the liquidus temperature tends to rise. Further, MgO is a component that easily reacts with BHF or hydrofluoric acid to form a product. This reaction product may adhere to the element on the surface of the glass substrate or adhere to the glass substrate, and may cause the element or the glass substrate to become cloudy. Therefore, the content of MgO is preferably 0 to 5%, more preferably 0 to 4%, still more preferably 0 to 3%, and most preferably 0 to 2.5%.

  CaO, like MgO, is a component that lowers the high temperature viscosity without lowering the strain point and significantly improves the meltability. If the content of CaO is too large, devitrification is likely to occur and the BHF resistance is lowered, and the reaction product adheres on the surface of the glass substrate or adheres to the glass substrate. Or the glass substrate may become cloudy. The preferable upper limit content of CaO is 12%, 11%, 10.5%, particularly 10%, and the preferable lower limit content is 3%, 3.5%, particularly 4%. The most preferable content range is 4 to 10%.

  SrO is a component that enhances chemical resistance and devitrification resistance. However, if the ratio is excessively increased in RO, the meltability is likely to be lowered, and the density and the thermal expansion coefficient are liable to be increased. Therefore, the content of SrO is preferably 0 to 6%, 0 to 5%, particularly 0 to 4.5%.

BaO is a component that enhances chemical resistance and devitrification resistance, but if its content is too large, the density tends to increase. Moreover, BaO has a poor effect of improving the meltability in RO. Since the SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ —RO-based glass according to the present invention is generally difficult to melt, the melting property is enhanced from the viewpoint of supplying a high-quality glass substrate at low cost and in large quantities. Therefore, it is very important to reduce the defect rate due to bubbles, foreign matters and the like. Therefore, the content of BaO is preferably 0 to 6%, 0.1 to 5%, particularly 0.5 to 4%. In the _{SiO 2 -Al 2 O 3 -B 2} O 3 -RO based glass according to the present invention, when reducing the content of SiO _2, although the melting property is effectively improved, reducing the content of SiO ₂ As a result, the acid resistance tends to decrease, and the density and thermal expansion coefficient easily increase.

  MgO, SrO, and BaO have the property of improving crack resistance compared to CaO. Therefore, the content of MgO + SrO + BaO (total amount of MgO, SrO and BaO) is preferably 2% or more, 3% or more, and more particularly more than 3%. However, when there is too much content of MgO + SrO + BaO, a density and a thermal expansion coefficient will rise easily. Therefore, the content of MgO + SrO + BaO is preferably 9% or less and 8% or less.

  When RO is mixed and introduced, the liquidus temperature is drastically lowered, and it is difficult for crystal foreign matter to be generated in the glass, thereby improving the meltability and moldability. However, when there is too much content of RO, a density will rise and it will become difficult to attain weight reduction of a glass substrate. Accordingly, the RO content is preferably less than 15%, less than 14%, and particularly less than 2 to 13%.

  In order to optimize the mixing ratio of RO, the mass ratio CaO / (MgO + SrO + BaO) is preferably 0.7 or more, 0.8 or more, 0.9 or more, particularly 1 or more, and the mass ratio CaO / MgO is Preferably they are 2 or more, 3 or more, 4 or more, especially 5 or more.

  ZnO is a component that improves meltability and BHF resistance. However, if its content is too large, the glass tends to be devitrified or the strain point is lowered, making it difficult to ensure heat resistance. . Therefore, the ZnO content is preferably 0 to 5%, particularly 0 to 1%.

ZrO ₂ is a component that enhances chemical durability. However, when the amount of ZrO ₂ increases, devitrification of ZrSiO ₄ tends to occur. The preferable lower limit content of ZrO ₂ is 1%, 0.5%, 0.3%, 0.2%, particularly 0.1%, and 0.005% or more may be introduced from the viewpoint of chemical durability. preferable. The most preferable content range is 0.005 to 0.1%. ZrO ₂ may be introduced from a raw material or may be introduced by elution from a refractory.

TiO ₂ has the effect of lowering the high-temperature viscosity to increase the meltability and the chemical durability. However, when the introduction amount is excessive, the ultraviolet transmittance tends to decrease. The content of TiO ₂ is preferably 3% or less, 1% or less, 0.5% or less, 0.1% or less, 0.05% or less, particularly 0.03% or less. When a very small amount of TiO ₂ is introduced (for example, 0.001% or more), an effect of suppressing coloring due to ultraviolet rays can be obtained.

P ₂ O ₅ is a component that increases the strain point and is a component that can suppress precipitation of devitrified crystals of alkaline earth aluminosilicates such as anorthite. However, when P ₂ O ₅ is contained in a large amount, the glass is likely to be phase-separated. The content of P ₂ O ₅ is preferably 0 to 5%, 0 to 3%, 0 to 2%, 0 to 1%, particularly 0 to 0.5%.

As a clarifying agent, metal powder such as As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , SO ₃ , Fe ₂ O ₃ , CeO ₂ , F ₂ , Cl ₂ , C, Al, Si, or the like can be used. . The total content is preferably 3% or less.

As ₂ O ₃ and Sb ₂ O ₃ are environmentally hazardous chemicals, so it is desirable not to use them as much as possible. The content of As ₂ O ₃ and Sb ₂ O ₃ is less than 0.3%, less than 0.1%, less than 0.09%, less than 0.05%, less than 0.03%, and less than 0.01%, respectively. , Less than 0.005%, particularly preferably less than 0.003%.

SnO ₂ has a function as a fining agent for reducing bubbles in the glass and has an effect of maintaining a relatively high ultraviolet transmittance when coexisting with Fe ₂ O ₃ or FeO. On the other hand, when the content of SnO ₂ is too large, devitrification stones of SnO ₂ is likely to occur in the glass. The preferable upper limit content of SnO ₂ is 0.5%, 0.4%, particularly 0.3%, and the preferable lower limit content is 0.01%, 0.05%, particularly 0.1%. The most preferable content range is 0.1 to 0.4%. Further, with respect to the content of _Fe 2 _{O 3} or FeO in terms _{of Fe} 2 _{O 3} is 0.01 to 0.05 percent, by introducing a SnO ₂ 0.01 to 0.5% foam quality and UV transmittance The rate can be increased. Here, “Fe ₂ O ₃ conversion” refers to a value obtained by converting the total Fe amount to the Fe ₂ O ₃ amount regardless of the valence.

When 0.01 to 0.5% of SnO ₂ is contained, if the content of Rh ₂ O ₃ is too large, the glass is likely to be colored. Note that Rh ₂ O ₃ may be mixed from a platinum production container. The content of Rh ₂ O ₃ is preferably 0 to 0.0005%, more preferably 0.00001 to 0.0001%.

SO ₃ is a component mixed from the raw material as an impurity, but if the content of SO ₃ is too large, bubbles called reboil may be generated during melting and molding, which may cause defects in the glass. is there. The preferable upper limit content of SO ₃ is 0.005%, 0.003%, 0.002%, particularly 0.001%, and the preferable lower limit content is 0.0001%. The most preferable content range is 0.0001% to 0.001%.

Iron is a component mixed from the raw material as an impurity, but if the iron content is too large, the ultraviolet transmittance may be lowered. When the ultraviolet transmittance is lowered, there is a possibility that a defect may occur in a photolithography process for manufacturing a TFT or a liquid crystal alignment process using ultraviolet rays. Therefore, the preferable upper limit content of iron is 0.001% in terms of Fe ₂ O ₃ , and the preferable lower limit content is 0.05% and 0.04% in terms of Fe ₂ O _3. 0.03%, especially 0.02%. The most preferable content range is 0.001% to 0.02%.

Cr ₂ O ₃ is a component mixed from the raw material as an impurity. However, if the content of Cr ₂ O ₃ is too large, light is incident from the end face of the glass substrate and the inside of the glass substrate is inspected by scattered light. When it is performed, light transmission is less likely to occur, which may cause a defect in the foreign matter inspection. In particular, this problem is likely to occur when the substrate size is 730 mm × 920 mm or more. Also, if the glass substrate is thin (for example, 0.5 mm or less, 0.4 mm or less, particularly 0.3 mm or less), the amount of light incident from the end surface of the glass substrate is reduced, so the content of Cr ₂ O ₃ is restricted. The significance of doing is increased. The preferable upper limit content of Cr ₂ O ₃ is 0.001%, 0.0008%, 0.0006%, 0.0005%, particularly 0.0003%, and the preferable lower limit content is 0.00001%. The most preferable content range is 0.00001 to 0.0003%.

It is preferable to reduce the content of alkali components, particularly Li components and Na components (for example, Li ₂ O, Na ₂ O), because they deteriorate the characteristics of various films and semiconductor elements formed on the glass substrate. , It is desirable not to contain substantially.

A preferable glass composition range can be obtained by combining preferable ranges of components. Among them, particularly preferable glass composition ranges are as follows.
(1) As a glass composition, by mass%, SiO ₂ 59 to 67%, Al ₂ O ₃ 17 to 22%, B ₂ O ₃ 4 to 7%, MgO 0 to 4%, CaO 3 to 10%, SrO 0 _{~5%, BaO 0.1~5%, 0~5} % ZnO, ZrO 2 0~5%, TiO 2 0~5%, P 2 O 5 0~5%, contains SnO 2 0 to 5%, Substantially free of Li and Na components.
(2) as a glass composition, in _{mass%, SiO 2 60~65%, Al} 2 O 3 17~20%, B 2 O 3 4~7%, 0~3% MgO, CaO 4~10%, SrO 0 _{~5%, BaO 0.1~5%, 0~1} % ZnO, ZrO 2 0~1%, TiO 2 0~1%, P 2 O 5 0~3%, SnO 2 0.01~1% content However, it contains substantially no Li component or Na component.

In recent years, flat panel displays for mobile applications such as OLED displays and liquid crystal displays have been increasingly required to be lightweight, and glass substrates are also required to be lightweight. In order to satisfy this requirement, it is desirable to reduce the weight of the glass substrate by reducing the density. The density is preferably 2.52 g / cm ³ or less, 2.51 g / cm ³ or less, 2.50 g / cm ³ or less, 2.49 g / cm ³ or less, particularly 2.48 / cm ³ or less. On the other hand, if the density is too low, the melting temperature is likely to rise and the liquid phase viscosity is likely to be lowered, and the productivity of the glass substrate is likely to be lowered. In addition, the strain point is likely to decrease. Therefore, the density is preferably 2.43 g / cm ³ or more, 2.44 g / cm ³ or more, in particular 2.45 g / cm ³ or more.

In the glass and glass substrate of the present invention, the thermal expansion coefficient is preferably 30 to 40 × 10 ⁻⁷ / ° C., 32 to 39 × 10 ⁻⁷ / ° C., 33 to 38 × 10 ⁻⁷ / ° C., particularly 34 to 37. × 10 ⁻⁷ / ° C. If it does in this way, it will become easy to match with the thermal expansion coefficient of the member (for example, a-Si, p-Si) formed into a film on a glass substrate.

In an OLED display or a liquid crystal display, a large-area glass substrate (for example, 730 × 920 mm or more, 1100 × 1250 mm or more, particularly 1500 × 1500 mm or more) is used, and a thin glass substrate (for example, a plate thickness of 0.5 mm). Hereinafter, 0.4 mm or less, particularly 0.3 mm or less) tends to be used. When the glass substrate becomes large and thin, bending due to its own weight becomes a big problem. In order to reduce the bending of the glass substrate, it is necessary to increase the specific Young's modulus of the glass substrate. The specific Young's modulus is preferably 30.0 GPa / g · cm ⁻³ or more, 30.5 GPa / g · cm ⁻³ or more, 31.0 GPa / g · cm ⁻³ or more, particularly 31.5 GPa / g · cm ^−3. That's it. In addition, when the glass substrate becomes large and thin, warpage of the glass substrate becomes a problem after a heat treatment process on a surface plate or a film formation process of various metal films, oxide films, semiconductor films, organic films, etc. Become. In order to reduce the warpage of the glass substrate, it is effective to increase the Young's modulus of the glass substrate. The Young's modulus is preferably 75 GPa or more, particularly 76 GPa or more.

  Currently, LTPS used in ultra-high-definition mobile displays has a process temperature of about 400 to 600 ° C. In order to suppress thermal shrinkage at this process temperature, the strain point is preferably 680 ° C. or higher, 690 ° C. or higher, particularly 700 ° C. or higher.

  Recently, OLED displays are also used in applications such as mobile and TV. In addition to the LTPS described above, an oxide TFT has attracted attention as a driving TFT element for this application. Conventionally, an oxide TFT has been manufactured by a temperature process of 300 to 400 ° C. equivalent to a-Si. However, when annealing is performed at a higher heat treatment temperature than before, more stable device characteristics can be obtained. I understand. The heat treatment temperature is about 400 to 600 ° C., and a glass substrate with low heat shrinkage is required even in this application.

  In the glass and glass substrate of the present invention, when the temperature is raised from room temperature (25 ° C.) to 500 ° C. at a rate of 10 ° C./min, held at 500 ° C. for 1 hour, and then lowered to room temperature at a rate of 10 ° C./min. The heat shrinkage value is preferably 30 ppm or less, 25 ppm or less, 23 ppm or less, 22 ppm or less, particularly 21 ppm or less. In this way, even if heat treatment is performed in the LTPS manufacturing process, problems such as pixel pitch deviation are less likely to occur. If the heat shrinkage value is too small, the productivity of the glass tends to decrease. Therefore, the heat shrinkage value is preferably 5 ppm or more, particularly 8 ppm or more. In addition to increasing the strain point, the heat shrinkage value can also be reduced by reducing the cooling rate during molding.

In the overflow down-draw method, molten glass flows down the surface of a wedge-shaped refractory (or a refractory coated with a platinum group metal), joins at the lower end of the wedge, and is formed into a plate shape. In the slot down draw method, for example, a ribbon-shaped molten glass is caused to flow down from a platinum group metal pipe having a slit-shaped opening, cooled, and formed into a plate shape. If the temperature of the molten glass in contact with the molding apparatus is too high, the molding apparatus will be deteriorated, and the productivity of the glass substrate will be easily lowered. Therefore, the temperature at a high temperature viscosity of 10 ^5.0 dPa · s is preferably 1300 ° C. or lower, 1280 ° C. or lower, 1270 ° C. or lower, 1260 ° C. or lower, 1250 ° C. or lower, 1240 ° C. or lower, particularly 1230 ° C. or lower. The temperature at a high temperature viscosity of 10 ^5.0 dPa · s corresponds to the temperature of the molten glass at the time of molding.

The SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ —RO-based glass according to the present invention is generally difficult to melt. For this reason, improvement of meltability becomes a problem. When the meltability is increased, the defect rate due to bubbles, foreign matters, and the like is reduced, so that a high-quality glass substrate can be supplied in large quantities at a low cost. On the other hand, when the viscosity of the glass in a high temperature range is too high, defoaming is hardly promoted in the melting step. Therefore, the temperature at a high temperature viscosity of 10 ^2.5 dPa · s is preferably 1650 ° C. or lower, 1640 ° C. or lower, 1630 ° C. or lower, 1620 ° C. or lower, particularly 1610 ° C. or lower. The temperature at a high temperature viscosity of 10 ^2.5 dPa · s corresponds to the melting temperature, and the lower this temperature, the better the meltability.

Devitrification resistance is important when molding by the downdraw method or the like. In consideration of the molding temperature of the SiO ₂ —Al ₂ O ₃ —B ₂ O ₃ —RO glass according to the present invention, the liquidus temperature is preferably 1250 ° C. or lower, 1230 ° C. or lower, 1220 ° C. or lower, 1210 ° C. or lower, It is 1200 degrees C or less, especially 1190 degrees C or less. The liquid phase viscosity is preferably 10 ^5.0 dPa · s or more, 10 ^5.2 dPa · s or more, 10 ^5.3 dPa · s or more, 10 ^5.4 dPa · s or more, 10 ^5.5 dPa or more. · S or more, in particular 10 ^5.6 dPa · s or more.

  A transparent conductive film, an insulating film, a semiconductor film, a metal film, or the like is formed on a glass substrate used for a high-definition display. Furthermore, various circuits and patterns are formed by a photolithography etching process. In these film forming process and photolithography etching process, the glass substrate is subjected to various chemical treatments. For example, in a TFT type 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 (thin film transistors) are formed on the glass substrate by a photolithography etching process. The In such a process, various chemical treatments such as sulfuric acid, hydrochloric acid, alkaline solution, hydrofluoric acid, and BHF are performed. In particular, BHF is widely used for etching an insulating film, but BHF erodes the glass substrate and tends to cloud the surface of the glass substrate, and the reaction product clogs the filter during the manufacturing process. There is a risk of adhering to the glass substrate. From the above situation, it is important to improve the chemical resistance of the glass substrate.

  The glass and glass substrate of the present invention are preferably formed by an overflow down draw method. The overflow down draw method is a method of forming a glass substrate by overflowing molten glass from both sides of a wedge-shaped refractory and drawing the overflowed molten glass downward while joining at the lower end of the wedge shape. In the overflow down draw method, the surface to be the surface of the glass substrate is not in contact with the refractory, and is formed in a free surface state. For this reason, an unpolished glass substrate having a good surface quality can be manufactured at a low cost, and an increase in area and thickness can be easily achieved. The material of the refractory used in the overflow downdraw method is not particularly limited as long as it can realize desired dimensions and surface accuracy. In addition, the method of applying a force when performing downward stretch molding is not particularly limited. For example, a method may be adopted in which a heat-resistant roll having a sufficiently large width is rotated and stretched in contact with the glass, or a plurality of pairs of heat-resistant rolls are contacted only near the end face of the glass. It is also possible to adopt a method of stretching by stretching.

  In addition to the overflow downdraw method, the glass substrate can be formed by, for example, a downdraw method (slot down method, redraw method, etc.), a float method, or the like.

  In the glass and glass substrate of the present invention, the plate thickness (wall thickness) is not particularly limited, but is preferably 0.5 mm or less, 0.4 mm or less, 0.35 mm or less, particularly 0.3 mm or less. The smaller the plate thickness, the easier it is to reduce the weight of the device. On the other hand, the smaller the plate thickness, the easier the glass substrate bends. However, since the glass and the glass substrate of the present invention have a high Young's modulus and specific Young's modulus, problems due to bending are unlikely to occur. In addition, plate | board thickness can be adjusted with the flow rate at the time of glass manufacture, a board drawing speed, etc.

  In the glass and glass substrate of the present invention, when the β-OH value is lowered, the strain point can be increased. The β-OH value is preferably 0.5 / mm or less, 0.45 / mm or less, 0.4 / mm or less, particularly 0.35 / mm or less. If the β-OH value is too large, the strain point tends to decrease. In addition, when the β-OH value is too small, the meltability tends to be lowered. Therefore, the β-OH value is preferably 0.01 / mm or more, particularly 0.05 / mm or more.

The following method is mentioned as a method for reducing the β-OH value. (1) Select a raw material with a low water content. (2) Add a component (Cl, SO ₃ or the like) that reduces the amount of moisture in the glass. (3) Reduce the amount of moisture in the furnace atmosphere. (4) N ₂ bubbling is performed in molten glass. (5) Adopt a small melting furnace. (6) Increase the flow rate of the molten glass. (7) An electric melting method is adopted.

Here, “β-OH value” refers to a value obtained by measuring the transmittance of glass using FT-IR and using the following equation.
β-OH value = (1 / X) log (T ₁ / T ₂ )
X: Glass wall thickness (mm)
T ₁ : Transmittance (%) at a reference wavelength of 3846 cm ⁻¹
T ₂ : Minimum transmittance (%) in the vicinity of a hydroxyl group absorption wavelength of 3600 cm ⁻¹

  The glass and glass substrate of the present invention are preferably used for OLED displays. OLEDs are generally being marketed, but cost reduction by mass production is strongly desired. Since the glass and the glass substrate of the present invention are excellent in productivity and can be easily increased in area and thinned, it is possible to satisfy such a demand accurately.

  Hereinafter, based on an Example, this invention is demonstrated in detail. The following examples are merely illustrative. The present invention is not limited to the following examples.

  Tables 1 to 3 show examples of the present invention (sample Nos. 1 to 30).

Each sample was produced as follows. First, a glass batch in which glass raw materials were prepared so as to have the glass composition in the table was placed in a platinum crucible and melted at 1600 ° C. for 24 hours. In melting the glass batch, the mixture was stirred and homogenized using a platinum stirrer. Next, the molten glass was poured out on a carbon plate and formed into a plate shape. For each of the obtained samples, density, thermal expansion coefficient, Young's modulus, specific Young's modulus, strain point, softening point, temperature at a high temperature viscosity of 10 ^5.0 dPa · s, temperature at a high temperature viscosity of 10 ^2.5 dPa · s, Liquid phase temperature, liquid phase viscosity log ηTL, and chemical resistance were evaluated.

  The density is a value measured by a well-known Archimedes method.

  The thermal expansion coefficient is an average thermal expansion coefficient measured with a dilatometer in a temperature range of 30 to 380 ° C.

  The Young's modulus refers to a value measured by a dynamic elastic modulus measurement method (resonance method) based on JIS R1602, and the specific Young's modulus is a value obtained by dividing Young's modulus by density.

  The strain point and softening point are values measured based on the method of ASTM C336.

The temperature at a high temperature viscosity of 10 ^5.0 dPa · s and 10 ^2.5 dPa · s is a value measured by a platinum ball pulling method.

  Next, each 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 held in a temperature gradient furnace for 24 hours. The temperature at which devitrification (crystal foreign matter) was observed in the glass was taken as the liquidus temperature. Furthermore, the viscosity of the glass at the liquidus temperature was measured by the platinum ball pulling method, and this was taken as the liquidus viscosity.

  In addition, after both surfaces of each sample are optically polished and immersed in a chemical solution set to a predetermined concentration at a predetermined temperature for a predetermined time, the surface of the obtained sample is observed to be chemically resistant. Evaluated. Specifically, after chemical treatment, the glass surface becomes cloudy or has cracks, “X”, weak cloudiness, rough appearance is “△”, and no change is “○”. did. As chemical treatment conditions, acid resistance was evaluated by treatment with 10% hydrochloric acid at 80 ° C. for 3 hours, and BHF resistance was evaluated by treatment with 20 ° C. for 30 minutes using a well-known 130 BHF solution.

  Furthermore, sample No. in the table. With respect to 12, 20, 23, and 24, a glass substrate having a thickness of 0.5 mm was prototyped by the overflow down draw method, and the thermal shrinkage value was measured. First, a 30 mm × 160 mm × 0.5 mm sample was cut out from the glass substrate, and the thermal shrinkage value of each sample was measured in the following manner. As shown in FIG. 1 (a), two linear marks M1 and M2 are entered at predetermined intervals in a predetermined portion of the glass substrate 25, and then perpendicular to the mark M as shown in FIG. 1 (b). The glass substrate piece 25a and the glass plate piece 25b were obtained by dividing the glass substrate 25 in various directions. Then, only the glass plate piece 25a was heated from normal temperature to 500 ° C. at a rate of 10 ° C./min, held at 500 ° C. for 1 hour, and then cooled to normal temperature at a rate of 10 ° C./min. Thereafter, as shown in FIG. 1C, the glass plate piece 25a subjected to the heat treatment and the glass plate piece 25b not subjected to the heat treatment are arranged side by side and fixed with the adhesive tape T. , M2 and the marks M1 and M2 of the glass plate piece 25b were measured, and the heat shrinkage value was calculated based on the following Equation 1.

In Equation 1, l ₀ is the distance between the marks M on the glass substrate 25, l ₁ is the distance between the mark M1 of the glass plate piece 25a and the mark M1 of the glass plate piece 25b, and l ₂ is the glass plate piece. This is the distance between the mark M2 of 25a and the mark M2 of the glass plate piece 25b.

Sample No. 1 to 30 each have a density of 2.43 to 2.52 g / cm ³ , and can reduce the weight of the glass substrate. Further, the thermal expansion coefficient is 30 to 40 × 10 ⁻⁷ / ° C., the strain point is 680 ° C. or higher and lower than 740 ° C., and the thermal shrinkage value is also small. In addition, the Young's modulus is 75 GPa or more and the specific Young's modulus is 30 GPa / (g / cm ³ ) or more, so that bending and deformation hardly occur. The temperature at a high temperature viscosity of 10 ^5.0 dPa · s is 1250 ° C. or lower, the temperature at 10 ^2.5 dPa · s is 1650 ° C. or lower, the liquidus temperature is 1300 ° C. or lower, and the liquid phase viscosity is 10 ^5.0. Since it is dPa · s or more, it has excellent meltability and moldability and is suitable for mass production. Furthermore, chemical resistance is also excellent.

The glass and glass substrate of the present invention have few alkali components, low density and thermal expansion coefficient, high strain point and Young's modulus, and are excellent in devitrification resistance, meltability, moldability and the like. Therefore, the glass and glass substrate of the present invention are suitable for displays such as OLED displays and liquid crystal displays, and are suitable for displays driven by LTPS and oxide TFTs.

Claims (8)

As a glass composition, in _{mass%, SiO 2 58~70%, Al} 2 O 3 18~25%, B 2 O 3 3~8%, 0~5% MgO, CaO 3~13%, SrO 0~6% _{, BaO 0~6%, 0~5% ZnO} , T iO 2 0~5%, P 2 O 5 0~5%, ZrO 2 0.005~1%, contained the following MgO + SrO + BaO 8%, substantially Li component and Na component are not included, the plate thickness is 0.5 mm or less, the strain point is 690 ° C. or more, and the temperature is raised from room temperature (25 ° C.) to 500 ° C. at a rate of 10 ° C./min. A glass substrate having a heat shrinkage value of 30 ppm or less when held at 500 ° C. for 1 hour and then cooled to room temperature at a rate of 10 ° C./min. _2. The glass substrate according to claim 1, wherein a content of TiO ₂ in the glass composition is 0.05% by mass or less and a mass ratio CaO / (MgO + SrO + BaO) is 1 or more. Thermal expansion coefficient is 30-40 × 10 ⁻⁷ / ° C., Young's modulus is 75 GPa or more, temperature at 10 ^5.0 dPa · s is 1250 ° C. or less, temperature at 10 ^2.5 dPa · s is 1650 ° C. or less, liquid phase The glass substrate according to claim 1, wherein the viscosity is 10 ^5.0 dPa · s or more. The glass substrate according to claim 1, wherein the density is 2.50 g / cm ³ or less.   The glass substrate according to any one of claims 1 to 4, wherein a β-OH value is 0.4 / mm or less. As a glass composition, in _{mass%, SiO 2 58~70%, Al} 2 O 3 18~25%, B 2 O 3 3~8%, 0~5% MgO, CaO 3~13%, SrO 0~6% BaO 0-6%, ZnO 0-5% , TiO ₂ 0-5%, P ₂ O ₅ 0-5%, ZrO ₂ 0.005-1% , MgO + SrO + BaO 8% , substantially Li In order to obtain a glass substrate containing no component and Na component and having a strain point of 690 ° C. or higher, it is melted by an electric melting method and molded to a thickness of 0.5 mm or less by an overflow downdraw method,
When the temperature is raised from room temperature (25 ° C.) to 500 ° C. at a rate of 10 ° C./min, held at 500 ° C. for 1 hour, and then cooled to room temperature at a rate of 10 ° C./min, the heat shrinkage value becomes 30 ppm or less. A method for producing a glass substrate, comprising obtaining a glass substrate.   The method for producing a glass substrate according to claim 6, wherein the glass substrate is melted by an electric melting method so as to have a β-OH value of 0.4 / mm or less and molded by an overflow downdraw method. The glass melt is melted by an electric melting method so that a glass substrate having a TiO ₂ content of 0.05% by mass or less and a mass ratio CaO / (MgO + SrO + BaO) of 1 or more is obtained. Item 8. A method for producing a glass substrate according to Item 6 or 7.