JP5446030B2 - Glass substrate - Google Patents

Description

  The present invention is suitable for a flat panel display substrate such as a liquid crystal display (LCD), an electroluminescence (EL) display, a plasma display panel (PDP), and various types of field emission displays (FED) having various electron-emitting devices. It relates to a glass substrate.

  Electronic devices such as thin-film transistor active matrix LCDs (TFT-LCDs) are thin and have low power consumption, so they are used in various applications such as car navigation, digital camera viewfinders, personal computer monitors, and televisions. .

  In general, aluminoborosilicate glass that does not substantially contain an alkali metal oxide is used as a material for a glass substrate for TFT-LCD, and various glass compositions have been proposed so far (Patent Documents 1 to 3). 3).

By the way, the TFT-LCD panel manufacturer produces a plurality of devices on a glass substrate (base plate) formed by a glass manufacturer, and then divides and cuts each device, and collects the product. Improvement and cost reduction. In recent years, the screen size of personal computer monitors, televisions, and the like has increased, and a large glass substrate is required in order to obtain a large number of these devices.
Japanese Patent No. 2990379 Japanese Patent No. 3465238 JP 2002-29775 A

  As described above, in recent years, the substrate size of the glass substrate tends to increase, and at present, a glass substrate having a substrate size of 2000 mm × 2000 mm or more is being used. However, when the substrate size of the glass substrate is increased, it becomes difficult to appropriately perform the melting defect inspection, and it becomes difficult to obtain a glass substrate having no melting defect.

  More specifically, the glass substrate melting defect inspection is performed by detecting light incident from one substrate end surface of the glass substrate and transmitted to the other substrate end surface side (non-incident side). . In this method, when a melted defect exists in the glass substrate, light incident from one substrate end face is scattered upon being hit by the melted defect, so this scattered light is visually observed from the surface of the glass substrate, or observed with a CCD camera, By measuring, the presence or absence of a melt defect can be detected. If incident light is introduced only in the end face direction, the light from the light source hardly affects the detection accuracy, and as a result, the melting defect inspection can be made highly accurate. However, as the substrate size of the glass substrate increases, the path length for reaching the other substrate end face side (non-incident side) becomes longer, and the rate at which incident light is absorbed by the glass increases. As a result, the amount of light transmitted decreases, and even if a melt defect exists on the glass substrate, sufficient illuminance cannot be obtained on the other substrate end surface side (non-incident side), making it difficult to detect the melt defect. . This problem becomes remarkable when the substrate size of the glass substrate is 1100 mm × 1250 mm or more, particularly 2000 mm × 2000 mm or more.

  In order to improve the detection accuracy of melting defects in glass substrates with large substrate dimensions, a measure to increase the illuminance on the light source side is also assumed, but if the illuminance on the light source side is excessively increased, the vicinity of the substrate end face where light is incident on the contrary Becomes too bright, making it difficult to detect fine flaws and, after all, is not an effective solution.

  Accordingly, the present invention provides a large glass substrate having no melting defect by appropriately performing a melting defect inspection over the entire surface of the glass substrate when the substrate size is 1100 mm × 1250 mm or more, particularly 2000 mm × 2000 mm or more. Is a technical issue.

As a result of diligent efforts, the inventors have regulated the difference between the transmittance at a wavelength of 550 nm at a path length (thickness) of 50 mm and the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm. The present inventors have found that the above technical problem can be solved and propose the present invention. That is, the glass substrate of the present invention has (1) a substrate size of 1100 mm × 1250 mm or more, (2) a transmittance of wavelength 550 nm at a path length of 50 mm is 85% or more, and (3) a transmittance of wavelength 550 nm at a path length of 50 mm. The difference in transmittance at a wavelength of 650 nm at a path length of 50 mm is 3% or less , (4) the average surface roughness Ra of the substrate end face is 0.5 μm or less, and (5) Cr ₂ O ₃ is 0.0001 to 0 in the glass composition. It is characterized by containing 0.002 mass% . Here, the “substrate dimension” refers to the area of one surface of the front and back surfaces of the glass substrate.

  When the substrate size of the glass substrate is 1100 mm × 1250 mm or more, if the transmittance at a wavelength of 550 nm at a path length of 50 mm is regulated to 85% or more, the ratio of the light incident on one end face of the glass substrate absorbed by the glass Even if the path length to the other substrate end face side (non-incident side) is long, it is possible to suppress a decrease in the amount of light transmitted through the glass substrate, that is, near the other substrate end face side (non-incident side). With this, sufficient illuminance can be obtained, and as a result, melting defects can be properly detected over the entire surface of the glass substrate.

As a result of diligent efforts, the present inventors have found that Cr ³⁺ in the glass composition decreases the transmittance of the glass substrate and greatly affects the inspection accuracy of the melt defect inspection, and an index for evaluating the influence of Cr ³⁺ The difference between the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm was regulated. That is, the glass substrate of the present invention regulates the difference between the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm to 3% or less when the substrate size is 1100 mm × 1250 mm or more. ^This prevents a situation in which the inspection accuracy of the melting defect inspection is lowered due to ³⁺ . Here, as the difference in transmittance of the absorption is large wavelength 650nm transmittance and ^{Cr 3+} wavelength 550nm absorbs less of ^{Cr 3+} is large, which means a greater influence of ^{Cr 3+.}

It is preferable that the glass substrate of the present invention does not contain a melting defect of 25 μm or more. In this way, since image defects caused by the glass substrate can be reduced, it is possible to appropriately cope with higher definition and higher performance of the display. Here, the “melting defect” includes undissolved raw materials, refractory mixture, devitrification, bubbles and the like.

The glass substrate of the present invention is characterized by containing 0.0001 to 0.002 mass% of Cr ₂ O ₃ in the glass composition. If the content of Cr ₂ O ₃ is regulated to 0.0001 to 0.002 mass%, it is easy to prevent a situation in which the inspection accuracy of the melt defect inspection is lowered due to Cr ³⁺ .

The glass substrate of the present invention is characterized in that the average surface roughness Ra of the substrate end face is 0.5 μm or less. Here, “average surface roughness Ra of the substrate end face” refers to a value measured by a method in accordance with JIS B0601: 2001, an evaluation length of 8 mm, a cutoff value λc = 0.8 mm, and a cutoff ratio λc / The value measured under the condition of λs = 100.

The glass substrate of the present invention preferably has a non-polished substrate surface and a swell of 0.1 μm or less. Here, “the substrate surface is unpolished” means that at least the surface of the glass substrate (priority guarantee surface), preferably both the front and back surfaces of the glass substrate are unpolished, except for the end surface of the glass substrate. “Waviness” is a value obtained by measuring WCA (filtered centerline waviness) described in JIS B-0610 using a stylus type surface shape measuring device. 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.

The glass substrate of the present invention is preferably formed by an overflow downdraw method. In this way, it is possible to obtain a glass substrate that is unpolished and has a smooth substrate surface.

The glass substrate of the present invention has, as a glass composition, mass% in terms of the following oxides: SiO ₂ 50 to 80%, B ₂ O ₃ 0 to 20%, MgO 0 to 15%, CaO 0 to 15%, SrO 0. _{~15%, BaO 0~15%, Na} 2 O 0~15%, K 2 O 0~10%, preferably contains Cr 2 O 3 0.0001~0.002%.

Glass substrates of the present invention has a glass _composition, a B 2 _{O 3} containing 3 to 20 wt%, and substantially alkali metal oxides _{(Li 2 O, Na 2 O} , K 2 O) that does not contain the Is preferred . Here, “substantially does not contain an alkali metal oxide” refers to a case where the content of the alkali metal oxide in the glass composition is 1000 ppm (mass) or less.

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

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

  In the glass substrate of the present invention, the substrate size is 1100 mm × 1250 mm or more, preferably 1500 mm × 1800 mm or more, more preferably 1870 mm × 2200 mm or more, further preferably 2350 × 2500 mm or more, particularly preferably 2400 × 2800 mm or more, and most preferably 2850. X3050 mm or more. That is, the larger the substrate size of the glass substrate, the greater the effect brought by the present invention. As the substrate size of the glass substrate increases, the path length necessary for the inspection of the melting defect becomes longer, so that it becomes difficult to obtain the illuminance necessary for inspecting the melting defect. However, the glass substrate of the present invention has a high transmittance at a wavelength of 550 nm at a path length of 50 mm, and the difference between the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm is small. Even if it is large, it is possible to reliably detect melting defects in the glass substrate. In the glass substrate of the present invention, the upper limit of the substrate size is not particularly set, but it is preferably 4000 mm × 4000 mm or less in consideration of the productivity of the glass substrate.

  In the glass substrate of the present invention, the transmittance at a wavelength of 550 nm at a path length of 50 mm is 85% or more, preferably 86% or more, more preferably 87% or more. If it does in this way, when the board | substrate dimension of a glass substrate is large, a fusion defect inspection can be performed appropriately and the fusion defect which exists in a glass substrate can be detected reliably.

In the glass substrate of the present invention, the difference between the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm is 3% or less, preferably 2% or less, more preferably 1.5% or less, still more preferably Is 1% or less. If it does in this way, it will become easy to prevent the situation where the inspection precision of a fusion defect inspection falls due to Cr3 ⁺ .

  The glass substrate of the present invention preferably does not contain melting defects of 25 μm or more (preferably 20 μm or more, more preferably 15 μm or more). If a glass substrate has a melting defect of 25 μm or more, it may be an obstacle to increase the definition and performance of the display. Since the glass substrate of the present invention can appropriately perform a melting defect inspection even when the substrate size is large, a glass substrate containing a melting defect of 25 μm or more can be easily detected.

Cr ₂ O ₃ is a component contained in the glass raw material or the like as an impurity. In the glass composition, chromium oxide exists mainly in a Cr ³⁺ state. Cr ³⁺ causes light absorption in a wavelength range of 400 to 550 nm and a wavelength range of 550 to 700 nm. The wavelength of 550 nm is a wavelength at which the absorption of Cr ³⁺ existing between these two wavelength ranges is relatively small. The wavelength of 650 nm is a wavelength at which Cr ³⁺ absorption is large in the wavelength range of 550 to 700 nm. Therefore, it can be said that the smaller the difference between the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm, the smaller the influence of absorption by Cr ³⁺ . If the difference in transmittance is regulated, it is easy to prevent a situation in which the inspection accuracy of the melt defect inspection is lowered due to Cr ³⁺ . The transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm are not uniquely determined by the content of Cr ₂ O ₃ in the glass composition, but contain Cr ₂ O ₃ When the amount is regulated to 0.002% by mass or less, preferably 0.0015% by mass or less, more preferably 0.001% by mass or less, the transmittance at a wavelength of 550 nm when the path length is 50 mm and the transmittance at a wavelength of 650 nm when the path length is 50 mm. It becomes easy to regulate the difference of 3% or less.

If the content of Cr ₂ O ₃ is made zero, it is easy to prevent a situation in which the inspection accuracy of the melt defect inspection is lowered due to Cr ³⁺ . However, in such a case, it is necessary to use a high-purity glass raw material, strictly control the manufacturing process of the glass substrate, and make the content of Cr ₂ O ₃ impurities zero. Is unreasonable and unrealistic. Therefore, considering the manufacturing cost of the glass substrate, the content of _Cr 2 _{O 3} was regulated to 0.0001% or more, good Mashiku 0.0002% or more, more preferably restricted to 0.0003% or more) To do .

In addition to Cr ₂ O ₃ , it is preferable to reduce the content of a component that absorbs light in the visible region or enhances light absorption in the visible region, such as a transition metal oxide, as much as possible. For example, the CeO ₂ content is preferably regulated to 0.1% or less (preferably 0.05% or less, more preferably 0.01% or less). However, similarly to the case of Cr ₂ O ₃ , considering the manufacturing cost of the glass substrate, the CeO ₂ content is preferably regulated to 0.001% or more. Further, the content of TiO ₂ is preferably regulated to 0.1% or less (preferably 0.05% or less, more preferably 0.01% or less). However, considering the manufacturing cost of the glass substrate, the content of TiO ₂ is preferably regulated to 0.001% or more. Furthermore, the content of NiO is preferably regulated to 0.05% or less (preferably 0.01% or less, more preferably 0.005% or less). However, considering the manufacturing cost of the glass substrate, the content of NiO is preferably regulated to 0.001% or more.

  In the glass substrate of the present invention, the substrate surface is preferably unpolished. If the substrate surface is unpolished, the polishing process is omitted, so that the manufacturing cost of the glass substrate can be greatly reduced. In the glass substrate of the present invention, the swell is preferably 0.1 μm or less (preferably 0.05 μm or less, more preferably 0.03 μm or less, still more preferably 0.01 μm or less). If the waviness of the glass substrate is larger than 0.1 μm, it may cause variations in the cell gap and cause display unevenness in the manufacturing process of LCDs and the like. In addition, if a glass substrate is shape | molded by the overflow downdraw method after adjusting manufacturing conditions, the substrate surface can be obtained without a grinding | polishing and a wave | undulation of 0.1 micrometer or less.

In the glass substrate of the present invention, the average surface roughness Ra of the substrate end face is 0.5 μm or less . In the melting defect inspection of a glass substrate, light is incident on one substrate end surface of the glass substrate, and the illuminance of light reaching the other substrate end surface side (non-incident side) is measured. Therefore, the surface state of the substrate end surface of the glass substrate has a considerable influence on the melting defect inspection. When the average surface roughness Ra of the substrate end surface is larger than 0.5 μm, light is scattered on the substrate end surface, and the inspection accuracy of the melt defect inspection is likely to be lowered.

A glass substrate used for an LCD or an organic EL display is also required to have the following characteristics.
(1) To have chemical resistance that does not deteriorate due to various acids, alkalis, and other chemicals used in the photoetching process.
(2) No heat shrinkage in heat treatment processes such as film formation and annealing. Therefore, it must have a high strain point.
(3) It has excellent meltability and formability so as not to cause undesirable melting defects as a glass substrate.

When the glass substrate of the present invention is immersed in a 10% HCl aqueous solution at 80 ° C. for 3 hours, it is preferable that no white turbidity or roughness is observed by visual observation of the surface. In addition, when the glass substrate of the present invention is immersed in a 63 BHF solution (HF: 6 mass%, NH ₄ F: 30 mass%) at 20 ° C. for 15 minutes, white turbidity and roughness may not be observed by visual observation of the surface. preferable. 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 TFT-LCD, and various circuits and patterns are formed by photoetching. In these film forming steps or photoetching steps, various heat treatments and chemical treatments are performed on the glass substrate. In general, in the TFT array process, a series of processes including a film forming process, a resist pattern forming process, an etching process, and a resist stripping process are repeated. At that time, as an etchant, a phosphoric acid solution is used for etching Al and Mo films, an aqua regia (HCl + HNO ₃ ) solution is used for etching ITO films, a BHF solution is used for etching SiNx, SiO ₂ films, and the like. A wide variety of chemical solutions are used, and these are not disposable but a circulating liquid system flow in consideration of cost reduction. If the chemical resistance of the glass substrate is low, the reaction product of the chemical and the glass substrate may clog the filter of the circulating liquid system during etching, or the glass substrate surface may become cloudy due to inhomogeneous etching or etching. Changes in the components of the liquid may cause various problems such as an unstable etching rate.

  In the glass substrate of the present invention, the strain point is preferably 630 ° C. or higher, more preferably 635 ° C. or higher, further preferably 640 ° C. or higher, and most preferably 645 ° C. or higher. In the TFT-LCD manufacturing process, the glass substrate is subjected to high-temperature heat treatment. If the strain point of the glass substrate is lower than 630 ° C., for example, when the glass substrate is heat-treated at 400 to 600 ° C., a minute dimensional shrinkage called thermal shrinkage occurs, which causes a shift in the pixel pitch of the TFT. It may cause a display failure. Moreover, there exists a possibility that a deformation | transformation, a curvature, etc. of a glass substrate may arise that the strain point of a glass substrate is less than 630 degreeC. Here, “strain point” refers to a value measured by a method based on ASTM C336.

  In the glass substrate of the present invention, the liquidus temperature is preferably 1200 ° C. or less, more preferably 1150 ° C. or less, still more preferably 1080 ° C. or less, particularly preferably 1050 ° C. or less, and most preferably 1030 ° C. or less. Generally, the overflow down draw method has a higher viscosity at the time of glass molding than other molding methods such as the float method, so if the devitrification resistance of the glass is poor, devitrification will occur during molding. It becomes difficult to form a glass substrate. Specifically, when the liquidus temperature is higher than 1200 ° C., it is difficult to mold by the overflow downdraw method, and it becomes difficult to obtain a glass substrate with good surface quality. That is, when the liquidus temperature is higher than 1200 ° C., an unreasonable restriction is imposed on the glass substrate forming method, and it becomes difficult to form a glass substrate having a desired surface quality. Here, “liquid phase temperature” refers to pulverizing glass, passing through a standard sieve 30 mesh (500 μm), and putting the glass powder remaining on 50 mesh (300 μm) into a platinum boat, and keeping it in a temperature gradient furnace for 24 hours. Later, it refers to the temperature at which crystals precipitate in the glass.

In the glass substrate of the present invention, the temperature at 10 ^2.5 dPa · s is preferably 1575 ° C. or less, and more preferably 1560 ° C. or less. If the glass is melted at a high temperature for a long time, melting defects such as bubbles and foreign matters in the glass can be reduced, but melting at a high temperature region increases the burden on the glass melting furnace. For example, refractories such as alumina and zirconia used in kilns are eroded violently by molten glass as the temperature rises, and the life cycle of the kiln is shortened accordingly. Moreover, the running cost for maintaining the interior of the kiln at a high temperature is higher than that when melting at a low temperature. Therefore, melting in a high temperature region is disadvantageous in producing a glass substrate. The temperature of the molten glass at a high temperature viscosity of 10 ^2.5 dPa · s corresponds to the melting temperature. Here, “temperature at 10 ^2.5 dPa · s” refers to a value measured by a known platinum pulling method.

The glass substrate of the present invention has, as a glass composition, mass% in terms of the following oxides: SiO ₂ 50 to 80%, B ₂ O ₃ 0 to 20%, MgO 0 to 15%, CaO 0 to 15%, SrO 0. _{~15%, BaO 0~15%, Na} 2 O 0~15%, K 2 O 0~10%, preferably contains Cr 2 O 3 0.0001~0.002%, in LCD or organic EL display if used, as a glass composition, in weight percent terms of _{oxide, SiO 2 50~80%, B 2} O 3 3~20%, 0~15% MgO, CaO 3~15%, SrO 0~15 %, BaO 0 to 15%, Cr ₂ O ₃ 0.0001 to 0.002%, and substantially no alkali metal oxide.

  The reason why the glass composition range of the glass substrate of the present invention is limited as described above will be described below. In addition, the following% display points out the mass% except the case where there is particular notice.

SiO ₂ is a glass network former, and is a component that improves the heat resistance of glass. Specifically, it is a component that has the effect of increasing the strain point and reducing the thermal shrinkage of the glass substrate. The amount is 50-80%, preferably 52-70%, more preferably 54-68%. When the content of SiO ₂ is large, the high-temperature viscosity of the glass becomes too high, and the meltability of the glass is lowered, and cristobalite devitrification is likely to precipitate. On the other hand, when the content of SiO ₂ is small, the acid resistance and strain point of the glass tend to decrease.

Al ₂ O ₃ is a component that raises the strain point of glass, suppresses the precipitation of devitrified cristobalite, and lowers the liquidus temperature of the glass, and its content is 5 to 25%, preferably 7 to 22%, more preferably 9 to 20%. When the content of Al ₂ O ₃ is large, the buffered hydrofluoric acid resistance (BHF resistance) of the glass tends to decrease, or the liquidus temperature of the glass tends to increase, making it difficult to mold the glass substrate. On the other hand, when the content of Al ₂ O ₃ is small, the strain point of the glass tends to decrease.

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 0 to 20%, preferably 3 to 20%, more preferably 5 to 5%. It is 15%, more preferably 6 to 14%, particularly preferably 7 to 13%. In the case of a non-alkali glass that does not substantially contain an alkali metal oxide in the glass composition, B ₂ O ₃ is an essential component, and B ₂ O ₃ in the glass composition is 3% or more, preferably 6% or more. Preferably, it is necessary to contain 7% or more. When there are many content of B ₂ O _3, may decrease the strain point of the glass, the acid resistance of the glass tends to decrease. On the other hand, the content of B ₂ O ₃ is small, becomes difficult to obtain an effect as a flux.

  MgO is a component that reduces only the high temperature viscosity without reducing the strain point of the glass and improves the meltability of the glass, and its content is 0 to 15%, preferably 0 to 10%, more preferably 0 to 7%, more preferably 0 to 0.5%. When the content of MgO is large, cristobalite or enstatite devitrification is likely to occur. Moreover, when there is much content of MgO, BHF resistance will fall, a glass substrate will be eroded by a photo-etching process, the reaction product will adhere to the surface of a glass substrate, and a glass substrate will become cloudy easily.

  CaO is a component that reduces only the high temperature viscosity without reducing the strain point of the glass and improves the meltability of the glass, and its content is 0 to 15%, preferably 0 to 12%, more preferably. 3 to 10%. In the case of alkali-free glass, CaO is an essential component, and it is necessary to contain 3% or more of CaO in the glass composition. When the content of CaO is large, in addition to the decrease in BHF resistance, the density and thermal expansion coefficient of glass tend to increase.

  SrO is a component that improves the chemical resistance and devitrification resistance of glass, and its content is 0 to 15%, preferably 0 to 12%, and more preferably 1 to 10%. When the content of SrO is large, the density and thermal expansion coefficient of glass tend to increase.

  BaO is a component that improves the chemical resistance and devitrification resistance of glass, and its content is 0 to 15%, preferably 0 to 12%, and more preferably 0 to 10%. When there is much content of BaO, it exists in the tendency for the density and thermal expansion coefficient of glass to rise.

  Alkaline earth metal oxides (MgO, CaO, SrO, BaO) can improve the meltability and devitrification resistance of glass when mixed and contained. The density tends to increase, making it difficult to reduce the weight of the glass substrate. The total content of the alkaline earth oxide is 0 to 25%, preferably 1 to 22%, more preferably 5 to 20%, still more preferably 7 to 18%.

Na ₂ O is a component that controls the thermal expansion coefficient of glass or increases the meltability of glass, and its content is 0 to 15%, preferably 0 to 10%. When Na 2 _O content is large, the strain point of the glass tends to decrease. K ₂ O is a component that controls the thermal expansion coefficient of glass or increases the meltability of glass, and its content is 0 to 10%. When K 2 _O content is large, the strain point of the glass tends to decrease. In the case of using the LCD or organic EL display, it is preferred not to contain alkali metal oxides _{(Na 2 O, K 2 O} , Li 2 O) a substantially. In this way, in the TFT manufacturing process, alkali metal ions are diffused into the semiconductor material on which the film is formed during the heat treatment, so that the film characteristics are not deteriorated, and the reliability of the TFT is not impaired.

Cr ₂ O ₃ is a component that affects the transmittance of the glass, and its content is 0.0001 to 0.002%, preferably 0.0002 to 0.0015%, more preferably 0.0003 to 0. 0.001%. When the content of cr ₂ O ₃ is more than 0.002%, the inspection accuracy of the molten defect inspection tends to decrease. On the other hand, if the content of Cr ₂ O ₃ is less than 0.0001%, it is necessary to use a high-purity glass raw material and to strictly control the glass substrate manufacturing process, so that the glass substrate manufacturing cost is unreasonable. To rise.

  The glass substrate of the present invention can contain up to 15% of the following components in addition to the above components in the glass composition.

  ZnO is a component that improves the BHF resistance of the glass and improves the meltability of the glass, and its content is 0 to 10%, preferably 0 to 5%, more preferably 0 to 3%. When there is much content of ZnO, it will become easy to devitrify glass and a strain point will fall easily.

ZrO ₂ is a component that improves the chemical resistance of glass, particularly acid resistance, and improves the Young's modulus, and its content is 0 to 10%, preferably 0 to 2%, more preferably 0 to 1. %. When the content of ZrO ₂ is large, the liquidus temperature of the glass rises, devitrification stones of zircon is readily released.

As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , Cl, and F are components that act as fining agents, and their content is 0 to 2% in total, preferably 0 to 1.5%, and more preferably Is 0.01 to 1%. Moreover, C and SO ₃ can also be contained as a fining agent in a range that does not affect the transmittance of the glass substrate. However, from the viewpoint of environmental protection, it is preferable that As ₂ O ₃ is not substantially contained as a clarifier. Here, “substantially does not contain As ₂ O ₃ ” refers to the case where the content of As ₂ O ₃ in the glass composition is 1000 ppm (mass) or less. Further, from the viewpoint of environmental protection, as a fining agent, it is preferable to contain substantially no Sb ₂ O _3. Here, “substantially does not contain Sb ₂ O ₃ ” refers to a case where the content of Sb ₂ O ₃ in the glass composition is 1000 ppm (mass) or less.

As ₂ O ₃ is a component that affects the transmittance, and when contained in the glass composition, the transmittance of the glass substrate tends to decrease. On the other hand, when SnO ₂ is contained in the glass composition in an amount of 0.01 to 2%, 0.05 to 1%, particularly 0.1 to 0.5%, the glass transmittance is increased due to the reduction effect of SnO _2. be able to. Further, as described _{above, As 2 O 3, Sb 2} O 3 , from the viewpoint of environmental protection, it is preferable not substantially contained. Considering the above points, it is preferable that SnO ₂ is contained as an essential component as a refining agent and substantially no As ₂ O ₃ or Sb ₂ O ₃ is contained.

Fe ₂ O ₃ is a component that affects the transmittance of glass, and its content is 0.001 to 0.03%, preferably 0.001 to 0.025%, more preferably 0.005 to 0. 0.02%, more preferably 0.006 to 0.02%, and particularly preferably 0.007 to 0.02%. When the content of Fe ₂ O ₃ is more than 0.03%, the transmittance of the glass substrate tends to decrease. On the other hand, if the content of Fe ₂ O ₃ is less than 0.001%, it is necessary to use a high-purity glass raw material and strictly control the manufacturing process of the glass substrate. To rise.

As described above, it is preferable to reduce the content of a component that absorbs light in the visible region or enhances light absorption in the visible region, such as a transition metal oxide, as much as possible. For example, the CeO ₂ content is preferably regulated to 0.1% or less (preferably 0.05% or less, more preferably 0.01% or less). However, considering the manufacturing cost of the glass substrate, the CeO ₂ content is preferably regulated to 0.001% or more. Further, the content of TiO ₂ is preferably regulated to 0.1% or less (preferably 0.05% or less, more preferably 0.01% or less). However, considering the manufacturing cost of the glass substrate, the content of TiO ₂ is preferably regulated to 0.001% or more. Furthermore, the content of NiO is preferably regulated to 0.05% or less (preferably 0.01% or less, more preferably 0.005% or less). However, considering the manufacturing cost of the glass substrate, the content of NiO is preferably regulated to 0.001% or more.

In addition to the above components, components that do not have significant absorption in the visible region can be added, and for example, Y ₂ O ₃ , Nb ₂ O ₅ , La ₂ O ₃ can be contained up to 5%. These components have a function of increasing the strain point, Young's modulus, etc. of the glass, but when the content is large, the density tends to increase.

In the 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 at 1450 to 1650 ° C., clarified, and then supplied to a molding apparatus. It can be produced by forming molten glass into a plate shape and slowly cooling it. As a method of setting the transmittance at a wavelength of 550 nm at a path length of 50 mm to 85% or more, and reducing the difference between the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm as 3% or less, 1) Use a glass raw material with few impurities that reduce the transmittance, especially a glass raw material with little Cr ₂ O ₃ , (2) prevent Cr ₂ O _{3 and the} like from being mixed in the glass substrate manufacturing process, (3) Examples of the method include adjusting the glass melting conditions such as the melting temperature, the melting atmosphere, and the melting time.

  As a material for the melting tank, it is preferable to use alumina refractories such as alumina electrocast bricks, zirconia refractories, zircon refractories, quartz refractories such as silica blocks, and the like. These refractories are suitable because they are hard to be eroded by molten glass and have little component elution into the glass.

The glass substrate of the present invention is preferably formed by an overflow downdraw method. If a glass substrate is formed by the overflow downdraw method, a glass substrate having good surface quality without polishing can be produced. The reason is that, in the case of the overflow downdraw method, the surface to be the surface of the glass substrate is not in contact with the bowl-like refractory and is molded in a free surface state. Here, the overflow down draw method is a method in which the molten glass is overflowed from both sides of the heat-resistant bowl-like refractory, and the overflowed molten glass is joined at the lower end of the bowl-like refractory and stretched downward to form glass. A method for manufacturing a substrate. The structure and material of the bowl-shaped refractory are not particularly limited as long as the dimensions and surface accuracy of the glass substrate can be set to a desired state and a quality usable for the glass substrate 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. If the liquid phase temperature is 1200 ° C. or lower and the liquid phase viscosity is 10 ^4.0 dPa · s or higher, the glass substrate can be produced by the overflow down draw method.

  In addition to the overflow down draw method, various methods can be employed as the glass substrate forming method of the present invention. For example, a forming method such as a float method, a slot down draw method, or a roll out method can be employed.

  The glass substrate of the present invention is preferably used for a display. The glass substrate of the present invention has a high transmittance at a wavelength of 550 nm at a path length of 50 mm, and a difference between the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm is small. It can detect and meet the recent demand for higher definition and higher functionality of displays. Further, the glass substrate of the present invention is preferably used for an LCD or an organic EL display. The glass substrate of the present invention has a large substrate size, high transmittance at a wavelength of 550 nm at a path length of 50 mm, and a small difference between the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm. Further, it is possible to easily improve the productivity of the LCD or the organic EL display and reduce the cost. Furthermore, since the glass substrate of the present invention can satisfy various properties required for LCDs or organic EL displays, it is suitable for this application.

  Hereinafter, based on an Example, this invention is demonstrated in detail.

  Tables 1 and 2 show examples of the present invention (sample Nos. 1 to 15), and Table 3 shows comparative examples (samples No. 16 and 17) of the present invention.

  Each sample in the table was prepared as follows.

  First, a batch prepared by preparing glass raw materials so as to have the glass composition shown in the table was put in a platinum crucible and melted at 1600 ° C. for 23.5 hours, and then poured out onto a carbon plate to be formed into a plate shape. Next, the molded glass was placed in an annealing furnace maintained at 750 ° C. and slowly cooled to obtain each sample.

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

  The thermal expansion coefficient was measured in a temperature range of 30 to 380 ° C. using a dilatometer.

  The strain point was measured by a method based on ASTM C336.

  The softening point was measured by a method based on ASTM C338.

The temperature at a high temperature viscosity of 10 ^2.5 dPa · s was measured by a well-known platinum ball pulling method.

  Young's modulus was measured by a resonance method.

  BHF resistance was evaluated by treating each sample using a 63BHF solution under the conditions of 20 ° C. and 15 minutes, and visually observing the surface of each sample. Specifically, “○” indicates that the sample surface is free of white turbidity, roughness and cracks, and “Sample” indicates that the surface of the sample is white turbidity but no roughness and cracks are generated on the surface of the sample. “△”, “X” means that the surface of the sample was clouded and the surface of the sample was rough or cracked.

  The acid resistance was evaluated by treating each sample using a 10% hydrochloric acid aqueous solution at 80 ° C. for 3 hours and visually observing the surface of each sample. Specifically, “○” indicates that the sample surface is free of white turbidity, roughness and cracks, and “Sample” indicates that the surface of the sample is white turbidity but no roughness and cracks are generated on the surface of the sample. “△”, “X” means that the surface of the sample was clouded and the surface of the sample was rough or cracked.

  The transmittance at wavelengths of 550 nm and 650 nm at a path length of 50 mm was measured as follows. First, each sample was cut to a thickness of 50 mm, and then the cut surface was mirror-polished to prepare a measurement sample having a thickness of 50 mm. Next, using a spectrophotometer, the transmittance of the measurement sample at wavelengths of 550 nm and 650 nm was measured.

  The melt defect inspection at a path length of 2000 mm was performed as follows. First, each sample was subjected to bull burner processing to produce a 2000 mm long rod, and both end surfaces were mirror-polished. Next, light was incident from one end face, and the illuminance was measured on the other end face (non-incident side). From the measured value of illuminance, evaluation was made with “◯” indicating that a 25 μm melt defect could be detected, and “X” indicating that a 25 μm melt defect could not be detected.

  As apparent from Tables 1 and 2, Sample No. Nos. 1 to 15 have a transmittance of 85% or more at a wavelength of 550 nm at a path length of 50 mm, and the difference between the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm is 3% or less. The evaluation of the melt defect inspection at a path length of 2000 mm was good.

On the other hand, as apparent from Table 3, the sample No. No. 16 has a Cr ₂ O ₃ content of 0.0025%, so that the difference between the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm is greater than 3%, The evaluation of the melt defect inspection was poor. Sample No. No. 17 has a Cr ₂ O ₃ content of 0.0040%, so that the transmittance at a wavelength of 550 nm at a path length of 50 mm is smaller than 85%, and the transmittance and path length at a wavelength of 550 nm at a path length of 50 mm. The difference in transmittance at a wavelength of 650 nm at 50 mm was greater than 3%, and the evaluation of the melt defect inspection at a path length of 2000 mm was poor.

  Furthermore, sample no. Glass substrates 1 to 15 were melted in a test melting furnace and molded by an overflow down draw method, so that the substrate surface was unpolished, the swell was 0.1 μm or less, and the substrate dimensions were 2000 mm × 2000 mm × 0.5 mm thick The transmittance of the wavelength 550 nm at a path length of 50 mm is 85% or more, the difference between the transmittance of the wavelength 550 nm at the path length of 50 mm and the transmittance of the wavelength 650 nm at the path length of 50 mm is 3% or less, and the path length A melting defect of 25 μm could be detected by a melting defect inspection at 2000 mm. Here, the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at 650 nm at a path length of 50 mm were measured after a glass substrate was laminated on a 50 mm glass cell. In the measurement, an immersion liquid (benzyl alcohol) was infiltrated between the glass substrates in consideration of the influence of the surface reflectance. In the measurement, the average surface roughness Ra of the substrate end face was regulated to 1 μm or less.

  As is apparent from the above description, the glass substrate of the present invention is suitable for flat panel display substrates such as LCDs, organic EL displays, inorganic EL displays, PDPs, and FEDs. The glass substrate of the present invention is also suitable for a cover glass for an image sensor such as a charge-coupled device (CCD) or a 1 × proximity solid-state imaging device (CIS), and a substrate for a solar cell.

Claims (10)

(1) The board dimension is 1100 mm × 1250 mm or more,
(2) The transmittance at a wavelength of 550 nm at a path length of 50 mm is 85% or more,
(3) The difference between the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm is 3% or less ,
(4) The average surface roughness Ra of the substrate end face is 0.5 μm or less,
(5) A glass substrate containing 0.0001 to 0.002 mass% of Cr ₂ O ₃ in the glass composition .   The glass substrate according to claim 1, wherein the glass substrate does not contain a melt defect of 25 μm or more. The glass substrate according to claim 1, wherein the glass composition contains 0.002 to 0.001 mass% of Cr ₂ O ₃ . 4. The glass substrate according to claim 1, wherein the difference between the transmittance at a wavelength of 550 nm at a path length of 50 mm and the transmittance at a wavelength of 650 nm at a path length of 50 mm is 1% or less .   The glass substrate according to claim 1, wherein the substrate surface is unpolished and the undulation is 0.1 μm or less.   The glass substrate according to any one of claims 1 to 5, wherein the glass substrate is formed by an overflow downdraw method. As a glass composition, in weight percent terms of _{oxide, SiO 2 50~80%, B 2} O 3 0~20%, 0~15% MgO, CaO 0~15%, SrO 0~15%, BaO 0~ _{15%, Na 2 O 0~15%} , K 2 O 0~10%, glass according to any one of claims 1 to 6, characterized in that it contains Cr 2 O 3 0.0001~0.002% substrate. The glass substrate according to any one of claims 1 to 7, wherein the glass composition contains ₃ to 20% by mass of B ₂ O ₃ and substantially does not contain an alkali metal oxide.   It uses for a display, The glass substrate in any one of Claims 1-8 characterized by the above-mentioned.   It uses for a liquid crystal display or an organic electroluminescent display, The glass substrate in any one of Claims 1-9 characterized by the above-mentioned.