Glass substrate

Abstract

To provide a glass substrate which has a low HF etching rate, is excellent in productivity, and hardly causes phase separation.SOLUTION: The glass plate of the present invention contains, as a glass composition, in% by mole, SiO265. 0 to 80.0%, Al2O32. 0 to 15.0%, B2O30. 15.0%, Li2O + Na2O + K2O0. 001 to less than 0.1%, MgO0. 15.0%, CaO0. 15.0%, SrO0. 15.0%,. 15.0%,. 01 to 1.0%,. less than 0.050%, and. less than 0.050%. BaO0 SnO20 Sb2O30 As2O30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a glass substrate, and more particularly to a glass substrate suitable for a micro LED display. [Background technology]

[0002] A tiling-type micro LED display has been developed (see Patent Document 1). In this display, a single display is constructed by arranging multiple display panels that use micro LEDs as light-emitting elements.

[0003] In a tiling-type micro LED display, it is necessary to make the boundaries between tiles less visible. For this reason, it is not possible to place the driving units on the periphery of the glass substrate, as in conventional displays. Therefore, the light-emitting elements on each tile must be driven from the back side of the glass. In this case, through-holes must be made in the thickness direction of the glass substrate to ensure electrical continuity between the front and back sides of the glass substrate.

[0004] A known method for forming through holes in the thickness direction of a glass substrate is to form modified areas inside the glass substrate by irradiating it with laser light, and then remove the modified areas by HF etching to form through holes (see Patent Document 2). Through holes formed by this method have a tapered shape in cross section. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-205525 [Patent Document 2] Patent No. 6333282 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, as pixel density increases due to higher resolution displays, wiring density also increases at the same time, and as a result, it becomes important to reduce the taper angle of the through-holes.

[0007] The taper angle of the through holes is thought to be determined by the ratio of the rate at which the holes extend in the plate thickness direction during etching to the rate at which the hole diameter expands. Slowing the rate at which the hole diameter expands can reduce the taper angle. Here, the rate at which the hole diameter expands is synonymous with the HF etching rate of the mother glass. Therefore, in order to produce through holes with a small taper angle, it is important to reduce the HF etching rate. To reduce the HF etching rate, the SiO2 content in the glass composition can be increased.

[0008] In addition, glass substrates for display applications are becoming increasingly cheaper. To reduce the cost of glass substrates, it is important to increase productivity (meltability, formability, and devitrification resistance) and improve surface quality by forming using the overflow downdraw method. However, increasing the SiO2 content as described above reduces meltability and increases melting costs. Furthermore, the forming temperature increases, which tends to shorten the life of the formed body used in the overflow downdraw method. As a result, the cost of the original glass substrate increases.

[0009] Furthermore, when glass components other than SiO2 are adjusted to increase the productivity of glass substrates, the glass becomes prone to phase separation. When glass phase separation occurs, not only does the transmittance decrease, but the glass surface tends to become cloudy during HF etching and unevenness tends to occur on the glass surface. As a result, the glass becomes unusable for display applications.

[0010] The present invention has been made in view of the above circumstances, and its technical object is to provide a glass substrate that has a low HF etching rate, is less susceptible to phase separation, and is highly productive. [Means for solving the problem]

[0011] After repeated experiments, the inventors discovered that the above technical problems can be solved by strictly controlling the glass composition of the glass substrate, and have proposed this invention. Specifically, the glass substrate of the present invention contains, in mole percent, 65.0 to 80.0% SiO2, 2.0 to 15.0% Al2O3, 0 to 15.0% B2O3, 0.001 to less than 0.1% Li2O + Na2O + K2O, 0 to 15.0% MgO, 0 to 15.0% CaO, 0 to 15.0% SrO, 0 to 15.0% BaO, 0 to 1.0% SnO2, 0 to less than 0.050% As2O3, and 0 to less than 0.050% Sb2O3. Note that "Li2O + Na2O + K2O" refers to the total amount of Li2O, Na2O, and K2O.

[0012] Furthermore, the glass substrate of the present invention preferably contains, as a glass composition, in mole percent, 69.6 to 80.0% of SiO2, 7.1 to 13.0% of Al2O3, 2.0 to 7.5% of B2O3, 0.001 to less than 0.1% of Li2O+Na2O+K2O, 3.4 to 10.0% of MgO, 0.1 to 5.5% of CaO, 0.1 to 15.0% of SrO, 0.3 to 3.0% of BaO, 0.01 to 1.0% of SnO2, 0 to less than 0.050% of As2O3, and 0 to less than 0.050% of Sb2O3.

[0013] Furthermore, the glass substrate of the present invention preferably contains, as a glass composition, in mole percent, 69.6 to 80.0% of SiO2, 7.1 to 12.5% ​​of Al2O3, 2.7 to 7.5% of B2O3, 0.001 to less than 0.1% of Li2O+Na2O+K2O, 3.4 to 10.0% of MgO, 0.1 to 5.5% of CaO, 0.5 to 3.8% of SrO, 0.3 to 3.0% of BaO, 0.01 to 1.0% of SnO2, 0 to less than 0.050% of As2O3, and 0 to less than 0.050% of Sb2O3.

[0014] Furthermore, the glass substrate of the present invention preferably contains, as a glass composition, in mole percent, 69.7 to 80.0% of SiO2, 2.0 to 15.0% of Al2O3, 2.5 to 15.0% of B2O3, 0.001 to less than 0.1% of Li2O+Na2O+K2O, 0 to 15.0% of MgO, 0 to 8.2% of CaO, 0 to 15.0% of SrO, 1.1 to 15.0% of BaO, 0.01 to 1.0% of SnO2, 0.0005 to 0.1% of TiO2, 0 to less than 0.050% of As2O3, and 0 to less than 0.050% of Sb2O3.

[0015] The glass substrate of the present invention preferably has an HF etching rate of 3.00 μm / min or less. Here, "HF etching rate" refers to a value measured by the following method. First, both sides of a sample were optically polished, then annealed, and partially masked. 300 mL of a 2.5 mol / L HF solution was set to 30°C using a water bath stirrer and stirred at approximately 600 rpm. The glass substrate was immersed in this HF solution for 20 minutes. The mask was then removed, the sample was washed, and the step between the masked and eroded areas was measured using a Surfcorder (ET4000A, manufactured by Kosaka Laboratory). The etching rate was calculated by dividing the value by the immersion time.

[0016] The glass substrate of the present invention has a high-temperature viscosity of 10 2.5 It is preferable that the temperature at which the viscosity reaches 10 dPa·s is 1760°C or less. 2.5 The "temperature at dPa·s" can be measured, for example, by the platinum sphere pulling method.

[0017] The glass substrate of the present invention preferably has through holes.

[0018] The glass substrate of the present invention is preferably used for a micro LED display. [Effects of the Invention]

[0019] According to the present invention, it is possible to provide a glass substrate which has a low HF etching rate, is less likely to cause phase separation, and is excellent in productivity. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic cross-sectional view of a glass substrate on which a modified portion is formed in the thickness direction. [Figure 2] FIG. 2 is a schematic cross-sectional view of a glass substrate during an etching process. [Figure 3] FIG. 1 is a schematic cross-sectional view of a glass substrate having a through-hole. [Figure 4] FIG. 10 is a schematic cross-sectional view of a glass substrate in which a narrowed portion inside a through hole is not located at the center in the plate thickness direction. [Figure 5] FIG. 10 is a schematic cross-sectional view of a glass substrate in which no narrowed portion is formed inside a through-hole. DETAILED DESCRIPTION OF THE INVENTION

[0021] The glass substrate of the present invention is characterized by its glass composition, which contains, in mole percent, 65.0 to 80.0% SiO2, 2.0 to 15.0% Al2O3, 0 to 15.0% B2O3, 0.001 to less than 0.1% Li2O + Na2O + K2O, 0 to 15.0% MgO, 0 to 15.0% CaO, 0 to 15.0% SrO, 0 to 15.0% BaO, 0 to 1.0% SnO2, 0 to less than 0.050% As2O3, and 0 to less than 0.050% Sb2O3. The reasons for limiting the content of each component as described above are as follows. Note that, in the description of the content of each component, % denotes mol% unless otherwise specified.

[0022] SiO2 is a component that forms the skeleton of glass. If the SiO2 content is too low, chemical resistance decreases. In particular, the HF etching rate increases, which increases the rate of hole diameter expansion during through-hole formation and increases the taper angle of the through-hole. Therefore, the lower limit of SiO2 is 65.0%, more preferably 68.0%, more preferably 68.6%, more preferably 68.8%, more preferably 68.9%, more preferably 69.1%, more preferably 69.6%, more preferably 69.7%, and particularly preferably 69.9%. Furthermore, when a glass substrate is etched with an HF solution, SiO2 dissolves in the solution and does not produce residue. Therefore, by incorporating a large amount of SiO2 into the glass, the amount of residue generated during etching is reduced, making it less likely for residue clogging to occur in the etching equipment, reducing the load when processing the residue, and reducing the cost required for residue processing. In particular, when the SiO2 content is 69.7% or more, the above-mentioned effects are enhanced, the HF etching rate is lowered, and the taper angle of the through-hole can be reduced. On the other hand, if the SiO2 content is too high, the high-temperature viscosity will increase, the amount of heat required for melting will increase, the melting cost will rise, and the SiO2 raw material will remain unmelted, which may cause a decrease in yield. Therefore, the upper limit of the SiO2 content is 80.0%, more preferably 78.0%, more preferably 76.0%, more preferably 75.8%, more preferably 75.5%, more preferably 75.3%, and particularly preferably 75.1%.

[0023] Al2O3 is a component that forms the glass skeleton and enhances chemical resistance. If the Al2O3 content is too low, chemical resistance decreases, and the HF etching rate in particular tends to increase. Therefore, the lower limit of Al2O3 is 2.0%, more preferably 5.2%, more preferably 7.1%, more preferably 7.3%, more preferably 7.5%, more preferably 7.7%, more preferably 8.0%, more preferably 8.6%, more preferably 8.7%, more preferably 8.8%, more preferably 8.9%, more preferably 9.0%, and particularly preferably 9.1%. On the other hand, if the Al2O3 content is too high, the amount of residue generated relative to the reduction in plate thickness during HF etching increases, making it more likely to cause residue clogging of the etching equipment. Therefore, the upper limit of Al2O3 is 15.0%, more preferably 13.0%, more preferably 12.9%, more preferably 12.5%, more preferably 12.3%, more preferably 12.0%, more preferably 11.8%, more preferably 11.5%, more preferably 11.0%, more preferably 10.9%, and particularly preferably 10.5%.

[0024] B2O3 is a component that improves meltability and devitrification resistance. If the B2O3 content is too low, meltability and devitrification resistance tend to decrease. Therefore, the lower limit of B2O3 content is 0%, preferably 0.1%, more preferably 0.5%, more preferably 0.6%, more preferably 1.0%, more preferably 1.5%, more preferably 2.0%, more preferably 2.1%, more preferably 2.5%, more preferably 2.7%, more preferably 2.8%, more preferably 3.1%, more preferably 3.4%, more preferably 3.5%, and particularly preferably 4.0%. Furthermore, when a glass substrate is etched with an HF solution, B2O3 dissolves in the solution and does not leave a residue. Therefore, by including B2O3 in glass, the amount of residue generated during etching is reduced, which reduces residue clogging in the etching equipment, reduces the load on the etching equipment when processing the residue, and reduces the cost required for residue processing. The above-mentioned effects are particularly easily achieved when the B2O3 content is 2.5% or more. On the other hand, if the B2O3 content is too high, the glass is prone to phase separation. When glass phase separation occurs, the glass substrate becomes cloudy, reducing the transmittance of the glass substrate. Even if no cloudiness is observed, the glass surface is prone to become cloudy during HF etching due to the effects of phase separation, and unevenness is likely to occur on the glass surface. Furthermore, phase separation regions with little SiO2 are formed, resulting in a high HF etching rate. Therefore, the upper limit of B2O3 is 15.0%, more preferably 10.0%, more preferably 7.5%, more preferably 7.4%, more preferably 7.3%, more preferably 7.0%, more preferably 6.5%, more preferably 6.0%, more preferably 5.5%, and particularly preferably 5.0%.

[0025] Li2O, Na2O, and K2O are components that are inevitably mixed in from the glass raw materials, and their total or individual contents are 0.001 to less than 0.1%, preferably 0.005 to 0.09%, and more preferably 0.01 to 0.05%. If the total or individual contents of Li2O, Na2O, and K2O are too high, there is a risk that alkali ions will diffuse into the semiconductor material formed in the heat treatment step.

[0026] MgO is a component that improves HF resistance and also reduces high-temperature viscosity, improving meltability. If the MgO content is too low, the HF etching rate increases, which tends to increase the taper angle of the through-holes. Furthermore, meltability also tends to decrease. Furthermore, the Young's modulus decreases, which makes the glass substrate more likely to bend and, as a result, more likely to break. Therefore, the lower limit of the MgO content is 0%, more preferably 1.0%, more preferably 1.1%, more preferably 1.1%, more preferably 3.0%, more preferably 3.4%, more preferably 3.5%, and particularly preferably 4.0%. In particular, when the MgO content is 3.4% or more, it is easier to form through-holes with a small taper angle. On the other hand, if the MgO content is too high, the glass is more likely to undergo phase separation. Furthermore, devitrified crystals such as mullite are more likely to form, which tends to reduce the liquidus viscosity. Therefore, the upper limit of MgO is 15.0%, more preferably 13.8%, more preferably 13.7%, more preferably 13.8%, more preferably 13.0%, more preferably 11.9%, more preferably 11.0%, more preferably 10.0%, more preferably 9.9%, more preferably 9.5%, and particularly preferably 9.0%.

[0027] CaO is a component that reduces high-temperature viscosity and improves meltability. If the CaO content is too low, the above effects are difficult to achieve. Therefore, the lower limit of the CaO content is 0%, more preferably 0.1%, more preferably 0.2%, more preferably 0.5%, and particularly preferably 1.0%. On the other hand, if the CaO content is too high, the glass is prone to phase separation. Furthermore, the amount of residue generated during etching increases, making it more likely for residue to accumulate inside some holes. As a result, the etching rate in the depth direction of the holes decreases, making the hole shape more likely to vary. In addition, residue clogging is more likely to occur in the etching equipment, increasing the load when processing the residue. Since the mass of the residue generated is proportional to the formula weight of the salt composed of alkaline earth elements, Al, and F, this problem becomes more pronounced as the atomic weight of the alkaline earth elements increases. In particular, when forming through holes by etching, residue equivalent to the volume of the through holes is generated in addition to the reduction in the thickness of the glass substrate. When a large number of through holes are provided, residues are generated in proportion to the number of through holes, and even for glass substrates that did not have problems in conventional slimming processes, the above-mentioned problems become apparent, resulting in increased manufacturing costs. Therefore, the upper limit of CaO is 15.0%, more preferably 10.0%, more preferably 8.5%, more preferably 8.2%, more preferably 8.0%, more preferably 5.5%, more preferably 5.4%, more preferably 5.3%, more preferably 5.0%, more preferably 4.5%, and particularly preferably 4.0%. In particular, when CaO is 5.5% or less, it becomes easier to solve the problems caused by the above-mentioned residues.

[0028] SrO is a component that reduces high-temperature viscosity and improves meltability. If the SrO content is too low, it becomes difficult to achieve the above-mentioned effects. Therefore, the lower limit of the SrO content is 0%, more preferably 0.1%, more preferably 0.2%, more preferably 0.5%, more preferably 0.6%, more preferably 0.7%, more preferably 0.8%, more preferably 0.9%, more preferably 1.0%, more preferably 1.5%, more preferably 2.0%, and particularly preferably 2.2%. On the other hand, if the SrO content is too high, the glass is prone to phase separation. Furthermore, the amount of residue increases, which leads to problems associated with the residue, leading to variations in hole shape and increased manufacturing costs. Therefore, the upper limit of the SrO content is 15.0%, more preferably 12.0%, more preferably 10.0%, more preferably 5.0%, more preferably 4.0%, more preferably 3.9%, more preferably 3.8%, more preferably 3.5%, more preferably 3.1%, and particularly preferably 3.0%. In particular, when the SrO content is 3.8% or less, the above-mentioned problems caused by residues are easily solved.

[0029] BaO is a component that enhances devitrification resistance and also makes glass phase separation more difficult. If the BaO content is too low, it becomes difficult to achieve the above-mentioned effects. Therefore, the lower limit of BaO content is 0%, more preferably 0.1%, more preferably 0.3%, more preferably 0.4%, more preferably 0.5%, more preferably 0.8%, more preferably 0.9%, more preferably 1.0%, more preferably 1.1%, more preferably 1.4%, more preferably 1.5%, more preferably 2.0%, and particularly preferably 2.1%. On the other hand, if the BaO content is too high, the HF etching rate tends to increase. In addition, the mass of the residue increases, causing the above-mentioned problems associated with the residue, leading to variations in hole shape and increased manufacturing costs. Therefore, the upper limit of BaO content is 15.0%, more preferably 10.0%, more preferably 5.0%, more preferably 3.0%, more preferably 2.9%, more preferably 2.8%, and particularly preferably 2.5%. In particular, when BaO is 3.0% or less, the above-mentioned problems caused by residues are easily solved.

[0030] SnO2 is a component that has a good clarification effect in the high temperature range, as well as a component that reduces high-temperature viscosity and improves meltability. Therefore, in order to produce glass substrates with a high yield, it is essential to include SnO2, and its content is preferably 0 to 1.0%, more preferably 0.01 to 0.8%, more preferably 0.01 to 0.5%, and particularly preferably 0.05 to 0.5%. If the SnO2 content is less than 0.01%, it becomes difficult to achieve the above effects. On the other hand, if the SnO2 content is too high, devitrified crystals of SnO2 are likely to precipitate, which may cause a decrease in yield.

[0031] TiO2 is a component that reduces high-temperature viscosity and improves meltability, and also increases absorbance in the ultraviolet range. High absorbance in the ultraviolet range, especially in the deep ultraviolet range, facilitates multiphoton absorption when irradiated with a femtosecond or picosecond laser, facilitating the creation of modified areas in glass. Therefore, the incorporation of TiO2 is advantageous when creating laser-modified areas on a glass substrate and subsequently removing the modified areas by etching to form through-holes in the glass substrate. Therefore, the lower limit of TiO2 is preferably 0%, more preferably 0.0005%, more preferably 0.001%, and particularly preferably 0.005%. On the other hand, if TiO2 is contained in large amounts, the glass substrate becomes colored and the transmittance of the glass substrate is likely to decrease. Therefore, when the glass substrate is used for displays, the upper limit of TiO2 is preferably 0.1%, more preferably less than 0.1%, more preferably 0.08%, and particularly preferably 0.05%.

[0032] ZnO is a component that improves meltability. However, if a large amount of ZnO is contained, the glass substrate becomes colored, and the transmittance of the glass substrate tends to decrease. Therefore, when the glass substrate is used for a display, it is desirable that the ZnO content be small, and the content is preferably 0 to less than 0.4%, more preferably 0 to 0.3%, more preferably 0 to 0.2%, and particularly preferably 0 to 0.1%.

[0033] In addition to the above components, the following components may be added as optional components: From the viewpoint of accurately enjoying the effects of the present invention, the content of components other than the above components is preferably 5% or less in total, and particularly preferably 1% or less.

[0034] P2O5 is a component that improves HF resistance. However, if a large amount of P2O5 is contained, the glass becomes prone to phase separation. Therefore, the P2O5 content is preferably 0 to 2.5%, more preferably 0.0005 to 1.5%, even more preferably 0.001 to 0.5%, and particularly preferably 0.005 to 0.3%.

[0035] CuO is a component that colors glass, and therefore, when a glass substrate is used for a display, it is desirable that the CuO content be as low as possible, and the content is preferably 0 to 0.1%, more preferably 0 to less than 0.1%, and particularly preferably 0 to 0.05%.

[0036] Y2O3, Nb2O5, and La2O3 are components that improve mechanical properties such as Young's modulus, but if the total amount or individual content of these components is too high, raw material costs tend to increase. Therefore, the total amount or individual content of Y2O3, Nb2O5, and La2O3 is preferably 0 to 5%, more preferably 0 to 1%, even more preferably 0 to 0.5%, and particularly preferably 0 to less than 0.5%.

[0037] As mentioned above, SnO2 is suitable as a fining agent, but as long as the glass properties are not impaired, F, SO3, C, or metal powders such as Al and Si can be added in amounts up to 1% each (preferably up to 0.8%, particularly up to 0.5%) instead of or together with SnO2 as a fining agent. CeO2 can also be added as a fining agent, but if the CeO2 content is too high, the glass will become colored, so the upper limit of its content is preferably 0.1%, more preferably 0.05%, and particularly preferably 0.01%.

[0038] As2O3 and Sb2O3 are also effective as fining agents. However, As2O3 and Sb2O3 are components that increase the environmental load. Therefore, it is preferable that the glass substrate of the present invention does not substantially contain these components, and the content range is 0 to less than 0.050%.

[0039] Cl is a component that promotes the initial melting of a glass batch. Furthermore, adding Cl can promote the action of a fining agent. As a result, melting costs can be reduced while the life of a glass manufacturing furnace can be extended. However, if the Cl content is too high, the strain point tends to decrease, which may cause problems such as total pitch deviation when used for displays. Therefore, the Cl content is preferably 0 to 3%, more preferably 0.0005 to 1%, and particularly preferably 0.001 to 0.5%. Cl can be introduced from a chloride of an alkaline earth metal oxide, such as strontium chloride, or from aluminum chloride.

[0040] Fe2O3 is a component that is inevitably mixed in from glass raw materials and is a component that causes glass coloration. If the Fe2O3 content is too low, raw material costs are likely to rise. On the other hand, if the Fe2O3 content is too high, the glass substrate will be colored, making it difficult to use for displays. The Fe2O3 content is preferably 0 to 300 ppm by mass, more preferably 80 to 250 ppm by mass, and particularly preferably 100 to 200 ppm by mass.

[0041] ZrO2 is a component that is irreversibly mixed in from the refractories used in glass manufacturing furnaces. If the ZrO2 content is too high, devitrification crystals are more likely to precipitate. On the other hand, if the ZrO2 content is reduced, the melting temperature must be lowered, which makes it difficult to melt the glass. Therefore, the ZrO2 content is preferably 0 to 0.5%, more preferably 0.0001 to 0.5%, more preferably 0.001 to 0.4%, and particularly preferably 0.005 to 0.3%.

[0042] The glass substrate of the present invention preferably has the following properties.

[0043] The HF etching rate is preferably 3.00 μm / min or less, 2.00 μm / min or less, 1.00 μm / min or less, 0.75 μm / min or less, 0.70 μm / min or less, 0.65 μm / min or less, and particularly preferably 0.60 μm / min or less. With such an etching rate, the hole diameter is less likely to expand when forming through-holes, allowing the taper angle to be small. As a result, through-holes can be formed in the glass substrate at a high density.

[0044] The average thermal expansion coefficient in the temperature range of 30 to 380°C is preferably 30 x 10 -7 ~50×10 -7 / °C, more preferably 32 × 10 -7 ~48×10 -7 / °C, more preferably 33 × 10 -7 ~45×10 -7 / °C, more preferably 34 × 10 -7 ~44×10 -7 / °C, particularly preferably 35 × 10 -7 ~43×10 -7 / °C. This makes it easier to match the thermal expansion coefficient of Si used in the TFT.

[0045] The Young's modulus is preferably 65 GPa or more, more preferably 70 GPa or more, more preferably 75 GPa or more, more preferably 77 GPa or more, and particularly preferably 78 GPa or more. If the Young's modulus is too low, defects due to bending of the glass substrate are likely to occur.

[0046] The strain point is preferably 650° C. or higher, more preferably 680° C. or higher, more preferably more than 686° C., and particularly preferably 690° C. or higher. In this way, thermal shrinkage of the glass substrate can be suppressed in the TFT manufacturing process.

[0047] The liquidus temperature is preferably 1350°C or lower, more preferably less than 1350°C, more preferably 1300°C or lower, and particularly preferably 1000 to 1280°C. This makes it easier to prevent the occurrence of devitrification crystals during forming, which would otherwise reduce productivity. Furthermore, since forming by the overflow downdraw method is easier, the surface quality of the glass substrate can be easily improved and the manufacturing cost of the glass substrate can be reduced. The liquidus temperature is an index of devitrification resistance, and the lower the liquidus temperature, the better the devitrification resistance.

[0048] The liquidus viscosity is preferably 10 4.0 dPa·s or more, preferably 10 4.1 dPa·s or more, preferably 10 4.2 dPa·s or more, particularly preferably 10 4.3 The viscosity is dPa·s or more. By doing so, devitrification is less likely to occur during forming, making it easier to form using the overflow downdraw method, which in turn makes it possible to improve the surface quality of the glass substrate and reduce the manufacturing costs of the glass substrate. The liquidus viscosity is an index of devitrification resistance and formability, and the higher the liquidus viscosity, the better the devitrification resistance and formability.

[0049] High temperature viscosity 10 2.5 The temperature at dPa·s is preferably 1760°C or less, more preferably 1700°C or less, more preferably 1690°C or less, more preferably 1680°C or less, and particularly preferably 1400 to 1670°C. 2.5 If the temperature at dPa·s is too high, it becomes difficult to melt the glass batch, and the manufacturing cost of the glass substrate rises. 2.5 The temperature at dPa·s corresponds to the melting temperature, and the lower this temperature, the better the melting property.

[0050] The β-OH value is an index indicating the amount of water in glass, and reducing the β-OH value can increase the strain point. Furthermore, even if the glass composition is the same, a smaller β-OH value results in a smaller thermal shrinkage at temperatures below the strain point. The β-OH value is preferably 0.35 / mm or less, more preferably 0.30 / mm or less, more preferably 0.28 / mm or less, more preferably 0.25 / mm or less, and particularly preferably 0.20 / mm or less. If the β-OH value is too small, the meltability tends to decrease. Therefore, the β-OH value is preferably 0.01 / mm or more, and particularly preferably 0.03 / mm or more.

[0051] The following methods can be used to reduce the β-OH value: (1) Select raw materials with a low water content. (2) Add components (Cl, SO3, etc.) to the glass that reduce the β-OH value. (3) Reduce the water content in the furnace atmosphere. (4) Bubble N2 in the molten glass. (5) Use a small melting furnace. (6) Increase the flow rate of the molten glass. (7) Use an electric melting method.

[0052] Here, the "β-OH value" refers to a value obtained by measuring the transmittance of glass using FT-IR and then using the following mathematical formula 1.

[0053] [Number 1] β-OH value = (1 / X) log(T1 / T2) X: Plate thickness (mm) T1: Reference wavelength 3846cm -1 Transmittance (%) T2: Hydroxyl group absorption wavelength 3600cm -1 Minimum transmittance (%) in the vicinity

[0054] The glass substrate of the present invention is preferably formed by an overflow downdraw method. The overflow downdraw method is a method for producing a glass substrate by overflowing molten glass from both sides of a heat-resistant trough-shaped structure, and drawing the overflowing molten glass downward while joining at the lower end of the trough-shaped structure. In the overflow downdraw method, the surface that will become the surface of the glass substrate does not come into contact with the trough-shaped refractory and is formed in a free surface state. Therefore, an unpolished glass substrate with good surface quality can be produced inexpensively, and thinning is also easy.

[0055] In addition to the overflow downdraw method, it is also possible to form a glass substrate by, for example, a downdraw method (such as a slot-down method) or a float method.

[0056] In the glass substrate of the present invention, the thickness is not particularly limited, but is preferably less than 0.7 mm, 0.6 mm or less, less than 0.6 mm, and particularly preferably 0.05 to 0.5 mm. The thinner the thickness, the smaller the diameter of the through holes can be. As a result, the through holes can be formed at a high density. The thickness can be adjusted by the flow rate during molding, the sheet drawing speed, etc.

[0057] The glass substrate of the present invention is preferably used as a substrate for a micro LED display, particularly a tiling-type micro LED display. In a tiling-type micro LED display, the light-emitting elements on the front surface of the glass substrate can be driven from the rear surface of the glass by establishing electrical continuity between the front and rear surfaces of the glass substrate via the through-holes. The glass substrate of the present invention allows for the formation of high-density through-holes, thereby enabling the tiling-type micro LED display to have high resolution.

[0058] The glass substrate of the present invention preferably has a through hole, and preferably has a plurality of through holes, which makes it easier to use as a substrate for a micro LED display, particularly a tiling type micro LED display.

[0059] A method for producing a through-hole will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of a glass substrate on which a modified portion is formed in the thickness direction. The glass substrate 100 has a first surface 101 and a second surface 102 as its main surfaces, and the modified portion 120 is formed so as to penetrate the first surface 101 and the second surface 102 in the thickness direction. The modified portion 120 can be formed by irradiating the glass substrate 100 with a femtosecond or picosecond pulse laser.

[0060] The laser beam shape is preferably a Gaussian beam shape or a Bessel beam shape, and particularly preferably a Bessel beam shape. The Bessel beam shape allows the modified region 120 to be formed so as to penetrate the plate thickness direction in one shot, thereby shortening the time required to form the modified region. The Bessel beam shape can be formed, for example, by using an alkoxy lens.

[0061] Fig. 2 is a schematic cross-sectional view of a glass substrate during an etching process. Fig. 3 is a schematic cross-sectional view of a glass substrate having a through-hole. For ease of explanation, Figs. 1 to 3 show one modified portion 120 and one through-hole 20, but in reality, a large number of modified portions 120 and many through-holes 20 are provided.

[0062] Glass substrate 100 having thickness tB and modified portion 120 is etched from both first surface 101 and first surface 102. During etching, modified portion 120 that has not yet been removed exists between non-through holes 21 extending from first surface 101 and first surface 102, as shown in Fig. 3. When etching proceeds further, the holes extending from first surface 101 and second surface 102 are connected to form through holes 20, as shown in Fig. 4.

[0063] By etching, the thickness of the glass substrate is reduced from tB to tA, the modified portion 120 is removed, and through-hole 20 is formed. Through-hole 20 has a tapered shape in cross-section, and its taper angle θ can be calculated from the following formula 1 using the hole diameter Φ1 at first surface 101 and second surface 102, the hole diameter Φ2 at the narrowed portion, and the plate thickness tA.

[0064] θ=arctan((Φ1−Φ2) / tA) Equation 1

[0065] The plate thickness tA after etching and the hole diameter Φ1 on the first surface 101 and the second surface 102 can be measured using, for example, a three-dimensional shape measuring machine (e.g., a CNC three-dimensional measuring machine manufactured by Mitutoyo Corporation) or a Surfcorder (ET4000A manufactured by Kosaka Laboratory Co., Ltd.). Alternatively, the plate thickness and hole diameter may be measured by observing the first surface, the second surface, and the cross section of the glass substrate using a transmission optical microscope (e.g., an ECLIPSE LV100ND manufactured by NIKON Corporation) and processing the images. The hole diameter Φ2 in the constricted portion is determined as follows: During cross-sectional observation in the evaluation method, the focus is moved into the glass and focused on the through-hole 20. The length of the constricted portion is measured from this image, and this value is taken as the hole diameter Φ2.

[0066] When used for displays, the taper angle is preferably 13° or less, more preferably 11° or less, more preferably 10° or less, more preferably 9° or less, more preferably 8° or less, and particularly preferably 7° or less. If the taper angle is too large, it becomes difficult to form through holes at a high density. As a result, it becomes difficult to mount semiconductors at a high density on a glass substrate. Furthermore, the taper angle is preferably 0° or more, more preferably 1° or more, more preferably 2° or more, more preferably 3° or more, more preferably 4° or more, and particularly preferably 5° or more. If the taper angle is too small, it becomes difficult to form a seed layer deep into the through hole by sputtering in the plating process for forming a conductive portion on the inner wall of the through hole.

[0067] The center-to-center distance between through holes is preferably 200 μm or less, more preferably 160 μm or less, and particularly preferably 100 μm or less. If the center-to-center distance between through holes is too large, it becomes difficult to form the through holes at a high density. As a result, it becomes difficult to mount semiconductors on the glass substrate at a high density. Furthermore, the center-to-center distance between through holes is preferably 1.5 times or more the hole diameter, more preferably 1.7 times or more, and particularly preferably 2.0 times or more. If the center-to-center distance between through holes is too small, the distance between the hole ends between the through holes becomes short, making the glass substrate more susceptible to breakage from the hole ends.

[0068] The type of etching solution used for etching is not particularly limited as long as it has a faster etching rate for the modified region 120 than for the glass substrate 100, and is preferably, for example, HF or KOH. HF is particularly preferred as the etching solution because of its fast etching rate. Alternatively, a mixed solution may be prepared by adding one or more acids such as HCl, H2SO4, or HNO3 to the HF solution. Using such a mixed solution makes it easier to reduce the adhesion of residues to the glass surface and the inner walls of the holes.

[0069] The temperature of the etching solution is not particularly limited, but it is effective to increase the temperature. In the case of an etching solution containing HF, the temperature range is preferably 0 to 50°C, more preferably 20 to 40°C. Increasing the temperature of the etching solution tends to relatively increase the etching rate of the modified portion. As a result, the time required to form the through-holes can be shortened and the amount of reduction in plate thickness can be reduced. On the other hand, if the temperature of the etching solution is too high, HF volatilizes in the etching solution, causing uneven HF concentration and increasing variation in hole shape.

[0070] During etching, it is preferable to agitate the etching solution or apply ultrasonic waves to the etching solution. In particular, applying ultrasonic waves can suppress the adhesion and re-adhesion of residues to the inner wall of the holes. The frequency of the ultrasonic waves is preferably 100 kHz or less, more preferably 45 kHz or less. This can enhance the cavitation effect caused by the ultrasonic waves.

[0071] Fig. 4 is a schematic cross-sectional view of a glass substrate in which the narrowed portion inside the through-hole is not located at the center in the plate thickness direction. The through-hole shown in Fig. 4 can be produced, for example, by etching a first surface 101 of a glass substrate 100 and then etching the second surface 102, which is the opposing surface. The taper angles θ1 and θ2 in this case can be calculated from the following equations 2 and 3. θ1=arctan((Φ1−Φ3) / (2*tA1)) Equation 2 θ2=arctan((Φ2−Φ3) / (2*tA2)) Equation 3

[0072] Fig. 5 is a schematic cross-sectional view of a glass substrate when no narrowed portion is formed inside the through-hole. The through-hole shown in Fig. 5 can be formed, for example, by etching only from the first surface 101 of the glass substrate 100. The taper angle in this case can be calculated from Equation 4 using the hole diameter Φ1 on the first surface 101, the hole diameter Φ2 on the second surface 102, and the plate thickness tA. θ=arctan((Φ1−Φ2) / (2*tA)) Equation 4 [Example]

[0073] The present invention will be described below based on examples. Note that the following examples are merely illustrative and the present invention is not limited to the following examples.

[0074] Table 1 shows examples of the present invention (samples Nos. 1 to 12).

[0075] [Table 1]

[0076] First, a glass batch prepared by blending glass raw materials to obtain the glass composition shown in the table was placed in a platinum crucible and melted at 1600-1650°C for 24 hours. When melting the glass batch, it was stirred using a platinum stirrer to homogenize it. Next, the molten glass was poured onto a carbon plate, formed into a plate, and then slowly cooled at a temperature near the annealing point for 30 minutes. For each sample obtained, the phase separation property, density, average coefficient of thermal expansion (CTE) in the temperature range of 30-380°C, Young's modulus, strain point (Ps), annealing point (Ta), softening point (Ts), and high-temperature viscosity (10 4.0 Temperature in dPa·s, high temperature viscosity 10 3.0 Temperature in dPa·s, high temperature viscosity 10 2.5 Temperature in dPa·s, liquidus temperature TL, initial phase, viscosity at liquidus temperature TL log 10 The ηTL, HF etching rate and β-OH value were evaluated.

[0077] The phase separation property was evaluated by assigning "◯" to a glass substrate on which no clouding was visually observed, and "×" to a glass substrate on which clouding was observed.

[0078] The density is a value measured by the well-known Archimedes method.

[0079] The average coefficient of thermal expansion CTE in the temperature range of 30 to 380°C is a value measured with a dilatometer.

[0080] The Young's modulus refers to a value measured by the well-known resonance method.

[0081] The strain point Ps, annealing point Ta, and softening point Ts are values ​​measured based on the methods of ASTM C336 and C338.

[0082] High temperature viscosity 10 4.0 dPa·s, 10 3.0 dPa·s, 10 2.5 The temperature at dPa·s was measured by the platinum sphere pulling method.

[0083] The liquidus temperature TL is the temperature at which crystals precipitate after the glass powder that passes through a standard 30 mesh (500 μm) sieve and remains on the 50 mesh (300 μm) sieve is placed in a platinum boat and held in a temperature gradient furnace for 24 hours. The crystals were then evaluated as the primary phase. In the table, "Cri" refers to cristobalite.

[0084] liquidus viscosity log 10 ηTL is the viscosity of the glass at the liquidus temperature TL measured by the platinum ball pull-up method.

[0085] The HF etching rate is a value measured by the above method.

[0086] As is clear from Table 1, in Samples Nos. 1 to 12, the glass composition was restricted within a predetermined range, and therefore the HF etching rate was 3.00 μm / min or less, and the high-temperature viscosity was 10 2.5 The temperature at dPa·s is 1700°C or less. Therefore, samples No. 1 to 12 have a low HF etching rate and excellent productivity, making them suitable for use as substrates for micro LED displays, especially tiling type micro LED displays. In addition, samples No. 1 to 9 do not exhibit phase separation in the glass, making them suitable for use as substrates for micro LED displays, especially tiling type micro LED displays.

[0087] Tables 2 to 5 show examples of the present invention (samples Nos. 13 to 61).

[0088] [Table 2]

[0089] [Table 3]

[0090] [Table 4]

[0091] [Table 5]

[0092] First, a glass batch prepared by blending glass raw materials to obtain the glass composition shown in the table was placed in a platinum crucible and melted at 1650-1680°C for 24 hours. When melting the glass batch, it was stirred using a platinum stirrer to homogenize it. Next, the molten glass was poured onto a carbon plate, formed into a plate, and then slowly cooled at a temperature near the annealing point for 30 minutes. For each sample obtained, the phase separation property, density, average coefficient of thermal expansion (CTE) in the temperature range of 30-380°C, Young's modulus, strain point (Ps), annealing point (Ta), softening point (Ts), and high-temperature viscosity (10 4.0 Temperature in dPa·s, high temperature viscosity 10 3.0 Temperature in dPa·s, high temperature viscosity 10 2.5 Temperature in dPa·s, liquidus temperature TL, initial phase, viscosity at liquidus temperature TL log 10 The ηTL, HF etching rate, and β-OH value were evaluated by the methods described above. In the table, "Mul" refers to mullite, and "Ano" refers to anorthite.

[0093] In Samples No. 13 to 61, the glass composition was restricted within a predetermined range, so the HF etching rate was 3.00 μm / min or less, and no phase separation occurred in the glass. Therefore, Samples No. 13 to 61 are suitable for substrates of micro LED displays, especially tiling type micro LED displays.

[0094] Furthermore, for Samples Nos. 1, 4 to 5, 8 to 10, and 24 to 43, micropores were formed by the following method, and the taper angles of the pores were confirmed.

[0095] First, we prepared glass substrates with a rectangular surface measuring 35 mm x 20 mm and a thickness of 500 μm. We irradiated these glass substrates with a femtosecond pulse laser shaped into a Bessel beam at a pitch of 160 μm, forming approximately 5,000 modified regions in a central area of ​​12.8 mm x 9.6 mm.

[0096] Next, this glass substrate was etched for a predetermined period of time. Specifically, the glass substrate was placed in a polypropylene test tube containing an etching solution, and ultrasonic waves were applied to the etching solution to etch the glass substrate, forming holes in the glass substrate. During this process, the glass substrate was fixed 40 mm from the bottom of the test tube using a Teflon (registered trademark) jig. The shapes of the formed through-holes and the glass substrate were as shown in Figure 4, and their shape parameters were measured using a transmission optical microscope (ECLIPSE LV100ND: manufactured by NIKON Corporation) using the method described above.

[0097] The etching solution used was a mixed acid of 2.5 mol / L HF and 1.0 mol / L HCl solution, and the temperature of the etching solution was set to 30°C. To prevent the temperature from rising during ultrasonic application, a chiller was used to circulate the water in the ultrasonic device, maintaining the water temperature at 30°C. An ultrasonic cleaner (VS-100III: AS ONE Corporation) was used to apply ultrasonic vibrations. This applied 28 kHz ultrasonic waves to the etching solution.

[0098] The thickness of the prepared glass substrate, the shape of the glass substrate after etching, and the shape of the holes created by etching are shown in Tables 6 to 14. The "HF etching rate" in the tables is the value shown in Tables 1 to 5, measured using a 2.5 mol / L HF solution. However, the etching solution used for forming the holes was a mixed acid of 2.5 mol / L HF and 1.0 mol / L HCl solution, and ultrasonic waves were also applied. Therefore, the etching rate when the holes were formed differs from the "HF etching rate" in the tables.

[0099] [Table 6]

[0100] [Table 7]

[0101] [Table 8]

[0102] [Table 9]

[0103] [Table 10]

[0104] [Table 11]

[0105] [Table 12]

[0106] [Table 13]

[0107] [Table 14]

[0108] These results show that the smaller the HF etching rate, the smaller the taper angle when microholes are formed. Also, the smaller the HF etching rate, the less likely it is that the taper angle will increase even if the etching time is increased to increase the hole depth. [Explanation of symbols]

[0109] 100 Glass substrate 101 First Surface 100 Second Surface 120 Reforming section 20 through holes 21 Non-through hole

Claims

1. The glass composition is, in mol%, SiO ２ 65.0-80.0%, Al ２ O ３ 2.0-15.0%, B ２ O ３ 0-15.0%, Li ２ O + Na ２ O+K ２ O 0.001 to less than 0.1%, MgO 0 to 15.0%, CaO 0 to 15.0%, SrO 0 to 15.0%, BaO 0 to 15.0%, SnO ２ 0-1.0%, As ２ O ３ 0 to less than 0.050%, Sb ２ O ３ A glass substrate containing 0 to less than 0.050%.

2. The glass composition is, in mol%, SiO ２ 69.6-80.0%, Al ２ O ３ 7.1-13.0%, B ２ O ３ 2.0-7.5%, Li ２ O + Na ２ O+K ２ O 0.001 to less than 0.1%, MgO 3.4 to 10.0%, CaO 0.1 to 5.5%, SrO 0.1 to 15.0%, BaO 0.3 to 3.0%, SnO ２ 0.01-1.0%, As ２ O ３ 0 to less than 0.050%, Sb ２ O ３ The glass substrate according to claim 1, containing 0 to less than 0.050%.

3. The glass composition is, in mol%, SiO ２ 69.6-80.0%, Al ２ O ３ 7.1-12.5%, B ２ O ３ 2.7-7.5%, Li ２ O + Na ２ O+K ２ O 0.001 to less than 0.1%, MgO 3.4 to 10.0%, CaO 0.1 to 5.5%, SrO 0.5 to 3.8%, BaO 0.3 to 3.0%, SnO ２ 0.01-1.0%, As ２ O ３ 0 to less than 0.050%, Sb ２ O ３ The glass substrate according to claim 1 or 2, containing 0 to less than 0.050% of Sn.

4. The glass composition is, in mol%, SiO ２ 69.7-80.0%, Al ２ O ３ 2.0-15.0%, B ２ O ３ 2.5-15.0%, Li ２ O + Na ２ O+K ２ O 0.001 to less than 0.1%, MgO 0 to 15.0%, CaO 0 to 8.2%, SrO 0 to 15.0%, BaO 1.1 to 15.0%, SnO2 0.01 to 1.0%, TiO ２ 0.0005-0.1%, As ２ O ３ 0 to less than 0.050%, Sb ２ O ３ The glass substrate according to claim 1 , wherein the content is 0 to less than 0.050%.

5. 5. The glass substrate according to claim 1, wherein the HF etching rate is 3.00 μm / min or less.

6. 6. The glass substrate according to claim 1, wherein the temperature at which the high-temperature viscosity is 102.5 dPa·s is 1760° C. or lower.

7. 7. The glass substrate according to claim 1, having a through hole.

8. The glass substrate according to any one of claims 1 to 7, which is used for a micro LED display.

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