JP2013256442A - Glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a large-sized glass substrate having no melt failure by carrying out a melt failure check appropriately over the whole glass substrate surface when the substrate size is at least 1,100 mm×1,250 mm, particularly at least 2,000 mm×2,000 mm.SOLUTION: The glass substrate has a substrate size of at least 1,100 mm×1,250 mm and transmittance at a wavelength of 500 to 800 nm and at a path length of 50 mm is at least 80%.

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.

  Therefore, 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 dimension is 1100 mm × 1250 mm or more, particularly 2000 mm × 2000 mm or more. Making it a technical issue.

  As a result of diligent efforts, the present inventors can evaluate the inspection accuracy of the melt defect inspection by using the transmittance at a wavelength of 500 to 800 nm at a path length (thickness) of 50 mm as an index when the substrate size of the glass substrate is large. The inventors have found that the above technical problem can be solved by regulating the transmittance of a wavelength of 500 to 800 nm at a path length of 50 mm, and propose the present invention. That is, the glass substrate of the present invention is characterized in that the substrate size is 1100 mm × 1250 mm or more, and the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm is 80% or more. Here, the “substrate dimension” refers to the area of one surface of the front and back surfaces of the glass substrate. Further, “transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm is 80% or more” means that the transmittance is 80% or more in the entire wavelength range of 500 to 800 nm.

  When the substrate size of the glass substrate is 1100 mm × 1250 mm or more, if the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm is regulated to 80% or more, the light incident on one end face of the glass substrate is absorbed by the glass. Even if the path length to the other substrate end surface 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, the other substrate end surface side (non-incident side) ) A sufficient illuminance can be obtained in the vicinity, and as a result, a melting defect can be detected properly over the entire surface of the glass substrate.

  Secondly, the glass substrate of the present invention is characterized by not containing 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.

Third, the glass substrate of the present invention is characterized by containing 0.001 to 0.03% by mass of Fe ₂ O ₃ in the glass composition. Here, “Fe ₂ O ₃ ” in the present invention includes not only iron oxide existing in the state of Fe ³⁺ but also iron oxide existing in the state of Fe ²⁺ . Note that iron oxide present in the form of ^{Fe 2+} is denoted on in terms of _Fe 2 _{O 3.}

  Fourth, the glass substrate of the present invention is characterized in that the average surface roughness Ra of the substrate end face is 1 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.

  Fifth, the glass substrate of the present invention is characterized in that the substrate surface is unpolished and the undulation is 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.

  Sixth, the glass substrate of the present invention is characterized by being formed by an overflow down draw method. In this way, it is possible to obtain a glass substrate that is unpolished and has a smooth substrate surface.

Seventh, the glass substrate of the present invention has a glass composition in terms of mass% in terms of the following oxides: SiO ₂ 50-80%, B ₂ O ₃ 0-20%, MgO 0-15%, CaO 0-15. _{%, SrO 0~15%, BaO 0~15} %, Na 2 O 0~15%, K 2 O 0~10%, characterized in that it contains Fe 2 O 3 0.001~0.03%.

Eighth, the glass substrate of the present invention contains ₃ to 20% by mass of B ₂ O ₃ as a glass composition, and substantially contains an alkali metal oxide (Li ₂ O, Na ₂ O, K ₂ O). It is characterized by not containing. 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.

  Ninth, the glass substrate of the present invention is characterized by being used for a display.

  Tenth, the glass substrate of the present invention is characterized by being 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, since the glass substrate of the present invention has a high transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm, it is possible to reliably detect melting defects in the glass substrate even if the substrate size is large. 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 500 to 800 nm at a path length of 50 mm is 80% or more, preferably 81% or more, more preferably 82% or more, and still more preferably 83% 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.

  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.

Fe ₂ O ₃ is a component contained in the glass raw material or the like as an impurity. In the glass composition, iron oxide exists mainly in two states, Fe ²⁺ and Fe ³⁺ . Fe ³⁺ causes light absorption in the visible region to the ultraviolet region (around 350 to 450 nm), and Fe ²⁺ in the long wavelength region of 600 to 1000 nm. The abundance ratio of Fe ²⁺ and Fe ³⁺ varies depending on various factors such as melting conditions (melting temperature, melting atmosphere, melting time, etc.), glass raw materials and impurities. Therefore, the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm is not uniquely determined by the content of Fe ₂ O ₃ in the glass composition. However, when the content of Fe ₂ O ₃ is regulated to 0.03% or less, preferably 0.025% or less, more preferably 0.02% or less, the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm is 80%. This makes it easier to regulate.

If the content of Fe ₂ O ₃ is made zero, the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm can be increased. However, in such a case, since a high-purity glass raw material is used, the manufacturing process of the glass substrate must be strictly controlled, and the content of impurities in Fe ₂ O ₃ must be zero. Is unreasonable and unrealistic. Therefore, considering the manufacturing cost of the glass substrate, the content of Fe ₂ O ₃ is 0.001% or more (preferably 0.005% or more, more preferably 0.006% or more, and further preferably 0.007%. It is preferable to regulate the above.

In addition to Fe 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 Fe 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 in the manufacturing process of LCDs and the like, which may cause display unevenness. 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 preferably 1 μm or less, and more preferably 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. If the average surface roughness Ra of the substrate end face is larger than 1 μm, light is scattered at the end face of the substrate, and the inspection accuracy of the melt defect inspection tends 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) The glass has excellent meltability and moldability 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 Fe 2 O 3 0.001~0.03%, 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%, Fe ₂ O ₃ 0.001 to 0.03%, 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.

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.

  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.

Cr ₂ O ₃ is a component that affects the transmittance of the glass, and its content is 0 to 0.001%, preferably 0.0001 to 0.002%, more preferably 0.0002 to 0.0015. %, More preferably 0.0003 to 0.001%. Since Cr ³⁺ absorbs light in the wavelength range of 400 to 550 nm and the wavelength range of 550 to 700 nm, if the content of Cr ₂ O ₃ is more than 0.002%, the inspection accuracy of the melt defect inspection tends to be lowered. 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.

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 wavelength range of 500 to 800 nm can be added. For example, Y ₂ O ₃ , Nb ₂ O ₅ , La ₂ O ₃ can be contained up to 5%. it can. 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. In addition, as a method for setting the transmittance of the glass substrate at a wavelength of 500 to 800 nm to 80% or more, (1) a glass raw material with few impurities that lower the transmittance, particularly a glass raw material with little Fe ₂ O ₃ is used. (1) Preventing Fe ₂ O _{3 and the} like from being mixed in the glass substrate production process, (3) methods for adjusting glass melting conditions such as melting temperature, melting atmosphere, and 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. Since the glass substrate of the present invention has a high transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm, melting defects can be easily detected, and the recent demand for higher definition and higher functionality of displays can be satisfied. Further, the glass substrate of the present invention is preferably used for an LCD or an organic EL display. Since the glass substrate of the present invention has a large substrate size and high transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm, 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 500 nm and 800 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, the transmittance of the measurement sample at wavelengths of 500 nm and 800 nm was measured using a spectrophotometer.

  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 illuminance was measured on the other end face side (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. 1 to 15 are transmittances of wavelengths of 500 nm and 800 nm at a path length of 50 mm of 80% or more, that is, transmittances of wavelengths of 500 to 800 nm at a path length of 50 mm are 80% or more, and evaluation of melting 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 an Fe ₂ O ₃ content of 0.020%, but since it was melted by adding C, which is a reducing agent, the transmittance at 800 nm was less than 80%, and the melt defect inspection at a path length of 2000 mm was performed. Evaluation was bad. Sample No. In No. 17, since the content of Fe ₂ O ₃ was 0.035%, the transmittance at 800 nm was less than 80%, 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 As a result, the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm was 80% or more, and a 25 μm melt defect could be detected by a melt defect inspection at a path length of 2000 mm. Here, the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm was 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.

  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.

  Therefore, 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 dimension is 1100 mm × 1250 mm or more, particularly 2000 mm × 2000 mm or more. Making it a technical issue.

As a result of diligent efforts, the present inventors can evaluate the inspection accuracy of the melt defect inspection by using the transmittance at a wavelength of 500 to 800 nm at a path length (thickness) of 50 mm as an index when the substrate size of the glass substrate is large. The inventors have found that the above technical problem can be solved by regulating the transmittance of a wavelength of 500 to 800 nm at a path length of 50 mm, and propose the present invention. That is, in the glass substrate of the present invention, the CaO content in the glass composition is 3 to 15% by mass, the substrate size is 1100 mm × 1250 mm or more, and the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm is 80. % Or more. Here, the “substrate dimension” refers to the area of one surface of the front and back surfaces of the glass substrate. Further, “transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm is 80% or more” means that the transmittance is 80% or more in the entire wavelength range of 500 to 800 nm.

  When the substrate size of the glass substrate is 1100 mm × 1250 mm or more, if the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm is regulated to 80% or more, the light incident on one end face of the glass substrate is absorbed by the glass. Even if the path length to the other substrate end surface 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, the other substrate end surface side (non-incident side) ) A sufficient illuminance can be obtained in the vicinity, and as a result, a melting defect can be detected properly over the entire surface of the glass substrate.

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 preferably contains 0.002 to 0.03% by mass of Fe ₂ O ₃ in the glass composition. Here, “Fe ₂ O ₃ ” in the present invention includes not only iron oxide existing in the state of Fe ³⁺ but also iron oxide existing in the state of Fe ²⁺ . Note that iron oxide present in the form of ^{Fe 2+} is denoted on in terms of _Fe 2 _{O 3.}

The glass substrate of the present invention preferably has an average surface roughness Ra of the substrate end face of 1 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 3 to 15%, SrO 0. _{~15%, BaO 0~15%, Na} 2 O 0~15%, K 2 O 0~10%, preferably contains Fe 2 O 3 0.001~0.03%.

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, since the glass substrate of the present invention has a high transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm, it is possible to reliably detect melting defects in the glass substrate even if the substrate size is large. 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 500 to 800 nm at a path length of 50 mm is 80% or more, preferably 81% or more, more preferably 82% or more, and still more preferably 83% 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.

  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.

Fe ₂ O ₃ is a component contained in the glass raw material or the like as an impurity. In the glass composition, iron oxide exists mainly in two states, Fe ²⁺ and Fe ³⁺ . Fe ³⁺ causes light absorption in the visible region to the ultraviolet region (around 350 to 450 nm), and Fe ²⁺ in the long wavelength region of 600 to 1000 nm. The abundance ratio of Fe ²⁺ and Fe ³⁺ varies depending on various factors such as melting conditions (melting temperature, melting atmosphere, melting time, etc.), glass raw materials and impurities. Therefore, the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm is not uniquely determined by the content of Fe ₂ O ₃ in the glass composition. However, when the content of Fe ₂ O ₃ is regulated to 0.03% or less, preferably 0.025% or less, more preferably 0.02% or less, the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm is 80%. This makes it easier to regulate.

If the content of Fe ₂ O ₃ is made zero, the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm can be increased. However, in such a case, since a high-purity glass raw material is used, the manufacturing process of the glass substrate must be strictly controlled, and the content of impurities in Fe ₂ O ₃ must be zero. Is unreasonable and unrealistic. Therefore, considering the manufacturing cost of the glass substrate, the content of Fe ₂ O ₃ is 0.001% or more (preferably 0.005% or more, more preferably 0.006% or more, and further preferably 0.007%. It is preferable to regulate the above.

In addition to Fe 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 Fe 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 in the manufacturing process of LCDs and the like, which may cause display unevenness. 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 preferably 1 μm or less, and more preferably 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. If the average surface roughness Ra of the substrate end face is larger than 1 μm, light is scattered at the end face of the substrate, and the inspection accuracy of the melt defect inspection tends 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) The glass has excellent meltability and moldability 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 3 to 15%, SrO 0. _{~15%, BaO 0~15%, Na} 2 O 0~15%, K 2 O 0~10%, preferably contains Fe 2 O 3 0.001~0.03%, 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%, Fe ₂ O ₃ 0.001 to 0.03%, 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 3 to 15%, preferably 3 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.

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.

  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.

Cr ₂ O ₃ is a component that affects the transmittance of the glass, and its content is 0 to 0.001%, preferably 0.0001 to 0.002%, more preferably 0.0002 to 0.0015. %, More preferably 0.0003 to 0.001%. Since Cr ³⁺ absorbs light in the wavelength range of 400 to 550 nm and the wavelength range of 550 to 700 nm, if the content of Cr ₂ O ₃ is more than 0.002%, the inspection accuracy of the melt defect inspection tends to be lowered. 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.

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 wavelength range of 500 to 800 nm can be added. For example, Y ₂ O ₃ , Nb ₂ O ₅ , La ₂ O ₃ can be contained up to 5%. it can. 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. In addition, as a method for setting the transmittance of the glass substrate at a wavelength of 500 to 800 nm to 80% or more, (1) a glass raw material with few impurities that lower the transmittance, particularly a glass raw material with little Fe ₂ O ₃ is used. (1) Preventing Fe ₂ O _{3 and the} like from being mixed in the glass substrate production process, (3) methods for adjusting glass melting conditions such as melting temperature, melting atmosphere, and 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. Since the glass substrate of the present invention has a high transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm, melting defects can be easily detected, and the recent demand for higher definition and higher functionality of displays can be satisfied. Further, the glass substrate of the present invention is preferably used for an LCD or an organic EL display. Since the glass substrate of the present invention has a large substrate size and high transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm, 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 500 nm and 800 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, the transmittance of the measurement sample at wavelengths of 500 nm and 800 nm was measured using a spectrophotometer.

  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 illuminance was measured on the other end face side (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. 1 to 15 are transmittances of wavelengths of 500 nm and 800 nm at a path length of 50 mm of 80% or more, that is, transmittances of wavelengths of 500 to 800 nm at a path length of 50 mm are 80% or more, and evaluation of melting 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 an Fe ₂ O ₃ content of 0.020%, but since it was melted by adding C, which is a reducing agent, the transmittance at 800 nm was less than 80%, and the melt defect inspection at a path length of 2000 mm was performed. Evaluation was bad. Sample No. In No. 17, since the content of Fe ₂ O ₃ was 0.035%, the transmittance at 800 nm was less than 80%, 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 As a result, the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm was 80% or more, and a 25 μm melt defect could be detected by a melt defect inspection at a path length of 2000 mm. Here, the transmittance at a wavelength of 500 to 800 nm at a path length of 50 mm was 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)

  A glass substrate having a substrate size of 1100 mm × 1250 mm or more and a transmittance of a wavelength of 500 to 800 nm at a path length of 50 mm of 80% or more.   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 0.002 to 0.03 mass% of Fe ₂ O ₃ is contained in the glass composition.   The glass substrate according to claim 1, wherein an average surface roughness Ra of the substrate end face is 1 μm 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 Fe 2 O 3 0.001~0.03% 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.