Alkali-free glass substrate and method for reducing thickness of alkali-free glass substrate

Abstract

The present invention pertains to an alkali-free glass substrate reduced in thickness by at least 5 µm using hydrofluoric acid (HF) etching to yield a plate thickness of no more than 0.4 mm, wherein the alkali-free glass substrate has a relative elastic modulus of at least 32 MNm / kg and a photoelastic constant of no more than 31 nm / MPa / cm; the glass of the substrate has a distortion point of at least 710°C, an average thermal expansion coefficient at 30-350°C of 30×10-7 to 43×10-7 / °C, a temperature T2 where the viscosity is 102 dPa / s of no more than 1710°C, and a temperature T4 at which the viscosity is 104 dPa / s of no more than 1320°C; the composition of the glass expressed as an oxide-basis molar percentage is SiO2: 66 to 70%, Al2O3 : 12 to 15%, B2O3: 0 to 1.5%, MgO: greater than 9.5 to 13%, CaO: 4 to 9%, SrO: 0.5 to 4.5%, BaO: 0 to 1%, and ZrO2: 0 to 2%; MgO+CaO+SrO+BaO is 17 to 21%; MgO / (MgO+CaO+SrO+BaO) is at least 0.40%, MgO / (MgO+CaO) is at least 0.40%; and MgO / (MgO+SrO) is at least 0.60.

Description

technical field

[0001] The present invention relates to an alkali-free glass substrate that is suitable as various glass substrates for displays, glass substrates for photomasks, thinned by etching using hydrofluoric acid (HF) and does not substantially contain alkali metal oxides, and non-alkali glass substrates. Thinning method of alkali glass substrate. Background technique

[0002] Conventionally, various glass substrates for displays, especially glass substrates on which a metal or oxide thin film or the like is formed on the surface, have required the following characteristics.

[0003] (1) When an alkali metal oxide is contained, the alkali metal ions diffuse into the thin film to degrade the film properties, so the alkali metal ion should not be contained substantially.

[0004] (2) When exposed to high temperature in the thin film forming process, in order to minimize the deformation of the glass and the shrinkage (thermal shrinkage) accompanying the structural sta...

Examples

Embodiment 1、2

[0155] (Example 1, 2, Comparative Example 1)

[0156] The raw materials of each component were prepared so that the target composition shown in Table 1 was obtained, melted in a continuous melting furnace, and formed into a flat plate by a float method to obtain an alkali-free glass substrate.

[0157] After mirror-polishing the obtained glass substrate, one side of the glass substrate was etched while bubbling with a mixed acid of 8 mass % hydrofluoric acid and 10 mass % hydrochloric acid, so that the thickness of the plate changed from 0.7 mm to 0.7 mm. 0.4mm, so as to reduce the thickness.

[0158] Using the thinned glass substrate, the breaking load was measured five times by the ball-and-ring (BOR) method using a SUS ring with a diameter of 30 mm and R = 2.5 mm and a SUS ball with a diameter of 10 mm. Table 2 shows the average breaking load converted to a plate thickness of 0.4 mm.

[0159] In addition, when the plate thickness was etched to 30 μm by the same procedure ...

Embodiment 3～5、 comparative example 2

[0171] The raw materials of each component were prepared so that the target compositions shown in Examples 3 to 5 in Table 3 were prepared, and melted at a temperature of 1650° C. for 1 hour using a platinum crucible. After melting, it flows out into a carbon plate shape, and after being kept at a temperature of glass transition temperature + 30° C. for 1 hour, it is cooled at 1° C. / minute and annealed to obtain an alkali-free glass substrate.

[0172] After mirror-polishing the obtained glass substrate, one side of the glass substrate was etched while bubbling with a mixed acid of 8 mass % hydrofluoric acid and 10 mass % hydrochloric acid, so that the thickness of the plate changed from 0.7 mm to 0.7 mm. 0.4mm, so as to reduce the thickness.

[0173] Using the thinned glass substrate, the breaking load was measured five times by the ball ring (BOR) method using a SUS ring with a diameter of 30 mm and R = 2.5 mm and a SUS ball with a diameter of 10 mm. Table 4 shows the avera...

technical field

[0001] The present invention relates to an alkali-free glass substrate that is suitable as various glass substrates for displays, glass substrates for photomasks, thinned by etching using hydrofluoric acid (HF) and does not substantially contain alkali metal oxides, and non-alkali glass substrates. Thinning method of alkali glass substrate. Background technique

[0002] Conventionally, various glass substrates for displays, especially glass substrates on which a metal or oxide thin film or the like is formed on the surface, have required the following characteristics.

[0003] (1) When an alkali metal oxide is contained, the alkali metal ions diffuse into the thin film to degrade the film properties, so the alkali metal ion should not be contained substantially.

[0004] (2) When exposed to high temperature in the thin film forming process, in order to minimize the deformation of the glass and the shrinkage (thermal shrinkage) accompanying the structural sta...

Examples

Embodiment 1、2

[0155] (Example 1, 2, Comparative Example 1)

[0156] The raw materials of each component were prepared so that the target composition shown in Table 1 was obtained, melted in a continuous melting furnace, and formed into a flat plate by a float method to obtain an alkali-free glass substrate.

[0157] After mirror-polishing the obtained glass substrate, one side of the glass substrate was etched while bubbling with a mixed acid of 8 mass % hydrofluoric acid and 10 mass % hydrochloric acid, so that the thickness of the plate changed from 0.7 mm to 0.7 mm. 0.4mm, so as to reduce the thickness.

[0158] Using the thinned glass substrate, the breaking load was measured five times by the ball-and-ring (BOR) method using a SUS ring with a diameter of 30 mm and R = 2.5 mm and a SUS ball with a diameter of 10 mm. Table 2 shows the average breaking load converted to a plate thickness of 0.4 mm.

[0159] In addition, when the plate thickness was etched to 30 μm by the same procedure ...

Embodiment 3～5、 comparative example 2

[0171] The raw materials of each component were prepared so that the target compositions shown in Examples 3 to 5 in Table 3 were prepared, and melted at a temperature of 1650° C. for 1 hour using a platinum crucible. After melting, it flows out into a carbon plate shape, and after being kept at a temperature of glass transition temperature + 30° C. for 1 hour, it is cooled at 1° C. / minute and annealed to obtain an alkali-free glass substrate.

[0172] After mirror-polishing the obtained glass substrate, one side of the glass substrate was etched while bubbling with a mixed acid of 8 mass % hydrofluoric acid and 10 mass % hydrochloric acid, so that the thickness of the plate changed from 0.7 mm to 0.7 mm. 0.4mm, so as to reduce the thickness.

[0173] Using the thinned glass substrate, the breaking load was measured five times by the ball ring (BOR) method using a SUS ring with a diameter of 30 mm and R = 2.5 mm and a SUS ball with a diameter of 10 mm. Table 4 shows the avera...

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