Glass and method for producing glass

Abstract

The present invention suppresses a decrease in the transmittance, while suppressing the inclusion of air bubbles. This glass (10) contains La2O3 and B2O3, and has a content of S of 100 ppm or more in terms of the mass ratio, an internal transmittance of 85% or more with respect to light having a wavelength of 440 nm, and a βOH of 0.1 mm-1 to 1.0 mm-1 inclusive.

Description

Glass and glass manufacturing method

[0001] The present invention relates to glass and to a method for making glass.

[0002] In recent years, there has been a demand for glass with a high refractive index. In particular, in wearable devices such as head-mounted displays that realize AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality), etc., a high refractive index and high transmittance for visible light are required for the light guide plate. For example, Patent Document 1 discloses La ２ O ３ , and B ２ O ３ and an optical glass containing 1 ppm or more and less than 300 ppm of sulfur S. Patent Document 1 describes that the inclusion of sulfur S can promote degassing.

[0003] Patent No. 6292877

[0004] However, if sulfur (S) is added to glass to suppress bubbles, there is a risk of a decrease in transmittance. Therefore, there is a need to suppress the decrease in transmittance while suppressing the inclusion of bubbles.

[0005] An object of the present invention is to provide glass and a method for manufacturing glass that can suppress the inclusion of bubbles while suppressing a decrease in transmittance.

[0006] The glass according to the present disclosure is ２ O ３ , and B ２ O ３ The mass ratio of S is 100 ppm or more, the internal transmittance for light with a wavelength of 440 nm is 70% or more, and βOH is 0.1 mm －１ More than 1.0 mm －１ The following is the result.

[0007] The method for producing glass according to the present disclosure includes mixing a raw material containing La, a raw material containing B, and SO ３ A raw material containing H ２a raw material containing O; heating the mixed raw material to melt it; and cooling the melted raw material to obtain glass, wherein the ratio of H to the total mass of the glass based on oxides is 1 / 2. ２ The ratio of the amount of added O is 0.5 wt% or more and 20 wt% or less. ２ The raw materials containing O are mixed.

[0008] According to the present invention, it is possible to suppress the inclusion of bubbles and also suppress the decrease in transmittance.

[0009] Fig. 1 is a schematic diagram of the glass according to the present embodiment, and Fig. 2 is a cross-sectional view of the glass according to the present embodiment when it is made into a glass plate.

[0010] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments, and when there are multiple embodiments, the present invention also includes combinations of the embodiments. Numerical values ​​include rounded ranges. Numerical ranges expressed as "to" refer to a range that includes the numbers before and after "to" as the lower and upper limits, and the same meaning will be used hereafter. In the present embodiment, the lower and upper limits can be combined as appropriate.

[0011] (Glass) FIG. 1 is a schematic diagram of glass according to this embodiment. As shown in FIG. 1, the glass 10 according to this embodiment is a plate-shaped glass plate, but the shape of the glass 10 is not limited to a plate shape and may be any shape. In this embodiment, the glass 10 is used as a light guide plate. More specifically, the glass 10 is used as a light guide plate for a head-mounted display. A head-mounted display is a display device (wearable device) that is worn on a person's head. However, the use of the glass 10 is arbitrary and is not limited to being used as a light guide plate, nor is it limited to being used in a head-mounted display.

[0012] (Composition) The composition of the glass 10 will be described below.

[0013] (La ２ O ３ and B ２O ３ ) The glass 10 is La ２ O ３ and B ２ O ３ Includes: ２ O ３ and B ２ O ３ By including La, a high refractive index and a high transmittance can be appropriately achieved. ２ O ３ and B ２ O ３ Whether or not a compound contains the compound can be measured by ICP mass spectrometry. As a measuring device, for example, Agilent 8800 manufactured by Agilent Technologies can be used.

[0014] (S) The S content of glass 10 relative to the total mass of glass 10 (S content / total mass of glass) in terms of mass ratio is 60 ppm or more, preferably 80 ppm or more, 100 ppm or more, preferably 120 ppm or more, more preferably 140 ppm or more, even more preferably 160 ppm or more, preferably 500 ppm or less, more preferably 400 ppm or less, even more preferably 350 ppm or less, preferably 300 ppm or less, more preferably 250 ppm or less, and even more preferably 200 ppm or less. The S content relative to the total mass of glass 10 is preferably 100 ppm to 500 ppm, more preferably 100 ppm to 300 ppm, more preferably 120 ppm to 250 ppm, more preferably 140 ppm to 200 ppm, and even more preferably 160 ppm to 200 ppm. When the lower limit of the S content falls within this range, the inclusion of bubbles in glass 10 can be appropriately suppressed. Furthermore, when the upper limit of the S content falls within this range, the decrease in transmittance of glass 10 can be more appropriately suppressed. The S content can be measured by ion chromatography. When calculating the S content, the total mass of glass 10 refers to the total mass of glass 10 based on oxides. The oxide basis refers to the assumption that all raw materials containing metal atoms other than S, which are constituents of glass 10, are decomposed and converted to metal oxides during melting, and the sum of the masses of these metal oxides is taken as the total mass (100 wt%) of glass 10.

[0015] (βOH) βOH of glass 10 is 0.1 mm －１ or more, and 0.2 mm －１ More than 0.3 mm is preferable. －１ More preferably, 0.4 mm or more －１ The βOH of the glass 10 is more preferably 1.0 mm. －１ less than or equal to 0.8 mm －１ Preferably less than 0.6 mm －１ More preferably, 0.5 mm or less －１ The following is more preferable: βOH of the glass 10 is 0.1 mm －１ More than 1.0 mm －１ less than 0.2 mm －１ More than 0.8 mm －１ Preferably less than 0.3 mm －１ More than 0.6 mm －１ More preferably, 0.4 mm or less －１ More than 0.5 mm －１ The following is even more preferable. βOH is an index showing the amount of water in glass, and a larger βOH value means a larger amount of water in the glass. When the lower limit of βOH of glass 10 falls within this range, it is possible to suppress a decrease in the transmittance of glass 10 even if the S content is within the above range (for example, 100 ppm or more). However, if a large amount of water is contained in the refining process and the amount of water has decreased by the time of the forming process, the amount of water contained in the raw materials may be reduced by the time of the forming process. ２ It is preferable to determine the water content based on the amount of O. Furthermore, by setting the upper limit of βOH of the glass 10 within this range, it is possible to suppress the generation of bubbles before molding. Generally, water contained in glass melted in a Pt container is converted into O by the permeation of H through the Pt container. ２ It is known that bubbles may occur. ２ In order to suppress bubbles, it is preferable to suppress the amount of water before the molding process. The βOH of the glass 10 is calculated by the following formula (1).

[0016] βOH=(1 / D)log １０ (τ1 / τ2) ...(1)

[0017] βOH in formula (1) is the value of βOH of glass 10 (mm－１ ), D refers to the thickness (mm) of the glass 10, and τ1 refers to the reference wave number 4000 (cm －１ ) and τ2 refers to the transmittance (%) of the glass 10 at a reference wave number of 3450 (cm －１ ) The transmittances τ1 and τ2 are measured using a Fourier transform infrared spectrophotometer (FT-IR).

[0018] A preferred composition of the glass 10 is described in detail below.

[0019] (SiO ２ ) The glass 10 is SiO ２ The glass 10 preferably contains, in mass % on an oxide basis, SiO ２ The content of the glass 10 is preferably 2.5% or more, more preferably 3.0% or more, and even more preferably 3.5% or more, expressed as mass % on an oxide basis. ２ The content of SiO is preferably 7.0% or less, more preferably 6.0% or less, and even more preferably 5.0% or less. ２ The content of SiO is preferably 2.5% or more and 7.0% or less, more preferably 3.0% or more and 6.0% or less, and even more preferably 3.5% or more and 5.0% or less. ２ When the upper limit of the content of SiO is within this range, good melting properties can be achieved. ２ When the lower limit of the content falls within this range, good resistance to devitrification can be achieved.

[0020] (B ２ O ３ ) Glass 10 is B ２ O ３ Glass 10 contains, in mass % on an oxide basis, B ２ O ３ The content of is preferably 6% or more, more preferably 7% or more, even more preferably 7.5% or more, and most preferably 8% or more. The glass 10 contains, in mass % on an oxide basis, B ２ O ３The content of is preferably 12% or less, more preferably 10% or less, further preferably 9.5% or less, and most preferably 9% or less. ２ O ３ The content of B is preferably 6% or more and 12% or less, more preferably 7% or more and 10% or less, even more preferably 7.5% or more and 9.5% or less, and most preferably 8% or more and 9% or less. ２ O ３ When the upper limit of the content of B is within this range, good melting properties can be achieved. ２ O ３ When the lower limit of the content is within the above range, good resistance to devitrification can be achieved.

[0021] (P ２ O ５ ) Glass 10 is P ２ O ５ or P ２ O ５ The glass 10 may contain, in mass % on an oxide basis, P ２ O ５ The content of P may be 0% or more, 0.3% or more, or 0.5% or more. The glass 10 contains, in mass % on an oxide basis, ２ O ５ The content of P is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less, expressed as mass % on an oxide basis. ２ O ５ The content of P may be 0% or more and 3% or less, 0.3% or more and 2% or less, or 0.5% or more and 1% or less. ２ O ５ When the content of P is in this range, it is possible to appropriately realize resistance to devitrification. ２ O ５ It is more preferable that it is not contained.

[0022] (CaO) The glass 10 may contain CaO or may not contain CaO. The CaO content of the glass 10, expressed in mass% on an oxide basis, is preferably 0% or more, more preferably 1% or more, and even more preferably 2% or more. The CaO content of the glass 10, expressed in mass% on an oxide basis, is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less. The CaO content of the glass 10, expressed in mass% on an oxide basis, is preferably 0% or more and 5% or less, more preferably 1% or more and 4% or less, and even more preferably 2% or more and 3% or less. When the CaO content is within this range, low specific gravity, devitrification resistance, high refractive index, and high transmittance can be appropriately achieved.

[0023] (SrO) Glass 10 may contain SrO or may not contain SrO. The SrO content of glass 10, expressed in mass % on an oxide basis, is preferably 0% or more, more preferably 1% or more, and even more preferably 2% or more. The SrO content of glass 10, expressed in mass % on an oxide basis, is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less. The SrO content of glass 10, expressed in mass % on an oxide basis, is preferably 0% or more and 5% or less, more preferably 1% or more and 4% or less, and even more preferably 2% or more and 3% or less. When the SrO content is within this range, devitrification resistance, a high refractive index, and a high transmittance can be appropriately achieved.

[0024] (BaO) The glass 10 may contain BaO or may not contain BaO. The BaO content of the glass 10, expressed in mass % on an oxide basis, is preferably 0% or more, more preferably 1% or more, and even more preferably 2% or more. The BaO content of the glass 10, expressed in mass % on an oxide basis, is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less. The BaO content of the glass 10, expressed in mass % on an oxide basis, is preferably 0% or more and 5% or less, more preferably 1% or more and 4% or less, and even more preferably 2% or more and 3% or less. When the BaO content is within this range, devitrification resistance, a high refractive index, and a high transmittance can be appropriately achieved.

[0025] (Li ２ O) The glass 10 contains Li to improve meltability. ２ It may contain O, or Li ２ The glass 10 may contain no O. The glass 10 contains, in mass % on an oxide basis, Li ２ The content of O may be 0% or more, 0.1% or more, or 0.3% or more. The glass 10 contains, in mass % on an oxide basis, Li ２ The O content is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. ２ The content of O may be 0% or more and 3% or less, 0.1% or more and 2% or less, or 0.3% or more and 1% or less. ２ When the content of O is within this range, it is possible to appropriately realize devitrification resistance, a high refractive index, and a high transmittance. ２ It is more preferable that O is not contained.

[0026] (Na ２ O) Glass 10 is Na ２ It may contain O or Na ２ The glass 10 may contain no O. The glass 10 contains, in mass % on an oxide basis, Na ２The content of O may be 0% or more, 0.1% or more, or 0.3% or more and 1% or less. ２ The O content is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. ２ The O content may be 0% or more and 3% or less, 0.1% or more and 2% or less, or 0.3% or more and 1% or less. ２ When the content of O is within this range, it is possible to appropriately realize devitrification resistance, a high refractive index, and a high transmittance. ２ It is more preferable that O is not contained.

[0027] (K ２ O) Glass 10 is K ２ It may contain O or K ２ The glass 10 may contain no O. The glass 10 contains, in mass % on an oxide basis, K. ２ The content of O may be 0% or more, 0.1% or more, or 0.3% or more. ２ The O content is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. ２ The O content may be 0% or more and 3% or less, 0.1% or more and 2% or less, or 0.3% or more and 1% or less. ２ When the content of O is within this range, it is possible to appropriately achieve devitrification resistance, a high refractive index, and a high transmittance. ２ It is preferable that O is not contained.

[0028] (ZnO) The glass 10 may contain ZnO or may not contain ZnO. The ZnO content of the glass 10, expressed in mass% on an oxide basis, is preferably 0% or more, more preferably 1% or more, and even more preferably 2% or more. The ZnO content of the glass 10, expressed in mass% on an oxide basis, is preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less. The ZnO content of the glass 10, expressed in mass% on an oxide basis, is preferably 0% or more and 5% or less, more preferably 1% or more and 4% or less, and even more preferably 2% or more and 3% or less. When the ZnO content is within this range, devitrification resistance, a high refractive index, and a high transmittance can be appropriately achieved.

[0029] (TiO ２ ) Glass 10 is TiO ２ The glass 10 preferably contains, in mass % on an oxide basis, TiO ２ The content of TiO is preferably 14% or more, more preferably 15% or more, and even more preferably 16% or more. ２ The content of TiO is preferably 20% or less, more preferably 18% or less, and even more preferably 17% or less, expressed as mass % on an oxide basis. ２ The content of TiO is preferably 14% or more and 20% or less, more preferably 15% or more and 18% or less, and even more preferably 16% or more and 17% or less. ２ When the upper limit of the content of TiO is within this range, high transmittance can be appropriately achieved. ２ When the lower limit of the content is within this range, it is possible to appropriately achieve both a high refractive index and resistance to devitrification.

[0030] (Nb ２ O ５ ) Glass 10 is Nb ２ O ５ The glass 10 preferably contains, in mass % on an oxide basis, Nb ２ O ５The content of Nb is preferably 8% or more, more preferably 8.5% or more, and even more preferably 9% or more, expressed in mass % on an oxide basis. ２ O ５ The content of Nb is preferably 13% or less, more preferably 12% or less, more preferably 11% or less, and even more preferably 10% or less, expressed in mass % on an oxide basis. ２ O ５ The content of Nb is preferably 8% or more and 13% or less, more preferably 8.5% or more and 12% or less, even more preferably 9% or more and 12% or less, still more preferably 9% or more and 11% or less, and even more preferably 9% or more and 10% or less. ２ O ５ When the upper limit of the Nb content is within this range, devitrification resistance can be appropriately achieved. ２ O ５ When the lower limit of the content falls within this range, a high refractive index can be appropriately achieved.

[0031] (Ta ２ O ５ ) The glass 10 is Ta ２ O ５ may contain Ta ２ O ５ The glass 10 may contain, in mass % on an oxide basis, Ta. ２ O ５ The content of Ta is preferably 0% or more, more preferably 0.3% or more, and even more preferably 0.5% or more. The glass 10 contains Ta, expressed as mass % on an oxide basis. ２ O ５ The content of Ta is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less. ２ O ５ The content of Ta is preferably 0% or more and 5% or less, more preferably 0.3% or more and 3% or less, and even more preferably 0.5% or more and 1% or less. ２ O ５When the content falls within this range, meltability, resistance to devitrification, a high refractive index, and a high transmittance can be appropriately achieved.

[0032] (W.O. ３ ) Glass 10 is WO ３ The glass 10 preferably contains, in mass % on an oxide basis, WO ３ The content of WO is preferably 0% or more, more preferably 0.1% or more, more preferably 0.2% or more, and even more preferably 0.3% or more. ３ The content of WO is preferably 5% or less, more preferably 3% or less, more preferably 2% or less, even more preferably 1% or less, and even more preferably 0.5% or less. ３ The content of WO is preferably 0% or more and 5% or less, more preferably 0.1% or more and 3% or less, even more preferably 0.2% or more and 2% or less, and still more preferably 0.3% or more and 1% or less. ３ When the content falls within this range, meltability, resistance to devitrification, and a high refractive index can be appropriately achieved.

[0033] (La ２ O ３ ) The glass 10 is La ２ O ３ Glass 10 contains, in mass % on an oxide basis, La ２ O ３ The content of La is preferably 38% or more, more preferably 40% or more, and even more preferably 41% or more. ２ O ３ The content of La is preferably 47% or less, more preferably 45% or less, and even more preferably 44% or less, expressed in mass % on an oxide basis. ２ O ３ The content of La is preferably 38% or more and 47% or less, more preferably 40% or more and 45% or less, and even more preferably 41% or more and 44% or less. ２O ３ When the upper limit of the content of La is within this range, the specific gravity and devitrification resistance can be appropriately achieved. ２ O ３ When the lower limit of the content falls within this range, both a high refractive index and a high transmittance can be appropriately achieved.

[0034] (Gd ２ O ３ ) Glass 10 is Gd ２ O ３ The glass 10 preferably contains, in mass % on an oxide basis, Gd ２ O ３ The content of Gd is preferably 6% or more, more preferably 7% or more, more preferably 8% or more, and even more preferably 9% or more. ２ O ３ The content of Gd is preferably 12% or less, more preferably 11% or less, even more preferably 10% or less, and still more preferably 9.5% or less, expressed as mass % on an oxide basis. ２ O ３ The content of Gd is preferably 6% or more and 12% or less, more preferably 7% or more and 11% or less, even more preferably 8% or more and 11% or less, preferably 8% or more and 10% or less, and even more preferably 9% or more and 9.5% or less. ２ O ３ When the upper limit of the Gd content is within this range, the specific gravity and devitrification resistance can be appropriately achieved. ２ O ３ When the lower limit of the content falls within this range, a high refractive index and a high transmittance can be appropriately achieved.

[0035] (Y ２ O ３ ) Glass 10 is Y ２ O ３ The glass 10 preferably contains, in mass % on an oxide basis, Y ２ O ３ The content of Y is preferably 0% or more, more preferably 1% or more, and even more preferably 2% or more.２ O ３ The content of Y is preferably 5% or less, more preferably 4.0% or less, and even more preferably 3.5% or less. ２ O ３ The content of Y is preferably 0% or more and 5% or less, more preferably 1% or more and 4.0% or less, and even more preferably 2% or more and 3.5% or less. ２ O ３ By setting the upper limit of the content of Y within this range, it is possible to appropriately achieve the specific gravity and devitrification resistance. ２ O ３ When the lower limit of the content falls within this range, a high refractive index and a high transmittance can be appropriately achieved.

[0036] (SiO ２ and B ２ O ３ Glass 10 contains SiO in mass% on an oxide basis. ２ and B ２ O ３ The total content of SiO is preferably 9% or more, more preferably 10% or more, and even more preferably 11% or more. ２ and B ２ O ３ The total content of SiO and SiO2 is preferably 14% or less, and more preferably 13% or less. ２ and B ２ O ３ The total content of SiO is preferably 9% or more, more preferably 10% or more and 14% or less, and even more preferably 11% or more and 13% or less. ２ and B ２ O ３ When the upper limit of the total content of SiO is within this range, a high refractive index and a high transmittance can be appropriately achieved. ２ and B ２ O ３ When the lower limit of the total content of and is within this range, devitrification resistance can be appropriately achieved.

[0037] (TiO ２ / B ２ O ３ ) B contained in glass 10 ２ O ３ TiO ２ The content ratio (TiO ２ / B ２ O ３ ) is preferably 3.00 or less, more preferably 2.50 or less, even more preferably 2.20 or less, even more preferably 2.00 or less, even more preferably 1.95 or less, even more preferably 1.90 or less, and even more preferably 1.70 or less, in mass ratio. ２ / B ２ O ３ ) is preferably 0.50 or more, more preferably 0.80 or more, even more preferably 1.00 or more, even more preferably 1.20 or more, even more preferably 1.30 or more, and even more preferably 1.50 or more, in mass ratio. ２ / B ２ O ３ ) is, in mass ratio, preferably 0.50 or more and 3.00 or less, more preferably 0.80 or more and 2.50 or less, even more preferably 1.00 or more and 2.20 or less, even more preferably 1.20 or more and 2.00 or less, even more preferably 1.30 or more and 1.95 or less, even more preferably 1.50 or more and 1.90 or less, and even more preferably 1.50 or more and 1.70 or less.

[0038] (Pt and Fe) The total content of Pt and Fe in the glass 10, by mass ratio, relative to the entire glass 10, is preferably 10 ppm or less, more preferably 9 ppm or less, even more preferably 8 ppm or less, and even more preferably 7 ppm or less. The total content of Pt and Fe in the glass 10, by mass ratio, relative to the entire glass 10, is preferably 0 ppm or more and 10 ppm or less, more preferably 0.1 ppm or more and 9 ppm or less, even more preferably 0.3 ppm or more and 8 ppm or less, and even more preferably 0.5 ppm or more and 7 ppm or less. By keeping the Pt and Fe contents within this range, the decrease in transmittance can be appropriately suppressed. The contents of Pt and Fe can be measured by ICP mass spectrometry. As a measuring instrument, for example, an Agilent 8800 manufactured by Agilent Technologies can be used.

[0039] (Sb) The glass 10 preferably does not contain Sb. By not containing Sb, high transmittance can be appropriately achieved. Note that "not containing Sb" means that the inclusion of Sb as an unavoidable impurity is permitted. Whether or not Sb is contained can be measured by ICP mass spectrometry. As a measuring instrument, for example, an Agilent 8800 manufactured by Agilent Technologies can be used.

[0040] (Glass Characteristics) The characteristics of the glass 10 will be described below.

[0041] (internal transmittance τ ４４０ ) Internal transmittance τ of glass 10 ４４０ is 70% or more, preferably 85% or more, more preferably 88% or more, and even more preferably 92% or more. ４４０ The transmittance τ of the glass 10 may be 99.9% or less, 99.8% or less, 99% or less, or 98% or less. ４４０ is 70% or more, preferably 85% or more and 99% or less, more preferably 88% or more and 98% or less, and even more preferably 92% or more and 98% or less. ４４０ When the transmittance τ is in this range, visible light can be transmitted appropriately. ４４０indicates the internal transmittance for light with a wavelength of 440 nm. More specifically, the internal transmittance τ ４４０ is the internal transmittance for light with a wavelength of 440 nm when converted to a thickness of 10 mm. The internal transmittance can be calculated from the measured values ​​of the external transmittance for two types of glass with different thicknesses and the following formula (2). Note that the external transmittance means the transmittance including surface reflection loss. In formula (2), τ is the internal transmittance of the glass when converted to a thickness of 10 mm, T1 and T2 are external transmittances, and Δd is the difference in thickness of the sample. The external transmittance can be measured using a spectrophotometer (U-4100 manufactured by Hitachi High-Technologies Corporation) for a sample that has been mirror-polished on both sides to a thickness of 10 mm.

[0042]

[0043] (Refractive index n ｄ ) Refractive index n of glass 10 ｄ is preferably 1.95 or more, more preferably 1.98 or more, more preferably 2.03 or more, and even more preferably 2.04 or more. ｄ is preferably 2.06 or less, and more preferably 2.05 or less. ｄ is more preferably 1.98 or more and 2.06 or less, and further preferably 2.03 or more and 2.05 or less. ｄ The refractive index n is the refractive index at the d line of helium (wavelength 587.6 nm). ｄ can be measured by the V-block method.

[0044] (Abbe number v ｄ ) Abbe number v of glass 10 ｄ is preferably 24 or more, more preferably 25 or more, and even more preferably 26 or more. ｄ is preferably 30 or less, more preferably 28 or less, and even more preferably 27 or less. ｄ is preferably 24 or more and 30 or less, more preferably 25 or more and 28 or less, and even more preferably 26 or more and 27 or less. ｄ By keeping the Abbe number v in this range, it is possible to appropriately control the wavelength dispersion. ｄis the variance (n Ｆ -n Ｃ ) with respect to the refractive index (n ｄ -1) Refractive index n F is the refractive index at the F line of hydrogen (wavelength 486.1 nm), and the refractive index n C refers to the refractive index at the C-line of hydrogen (wavelength 656.3 nm).

[0045] (Glass Transition Temperature) The glass transition temperature Tg of the glass 10 is preferably 680°C or higher, more preferably 700°C or higher, and even more preferably 710°C or higher. The glass transition temperature Tg of the glass 10 is preferably 760°C or lower, more preferably 750°C or lower, even more preferably 740°C or lower, and even more preferably 730°C or lower. The glass transition temperature Tg of the glass 10 is preferably 680°C or higher and 760°C or lower, more preferably 700°C or higher and 750°C or lower, and even more preferably 710°C or higher and 740°C or lower. The glass transition temperature can be measured according to the method specified in JIS R3103-3:2001 "Viscosity and Viscosity Fixed Points of Glass - Part 3: Method for Measuring Transition Temperature by Thermal Expansion Method."

[0046] (Devitrification Temperature) The devitrification temperature of glass 10 is preferably less than 1290°C, more preferably 1270°C or less, and even more preferably 1250°C or less. Having a devitrification temperature within this range allows the temperature at which raw materials are melted during the production of glass 10 to be relatively low, thereby preventing Pt contained in the melting equipment from dissolving and being mixed into the glass, thereby appropriately suppressing a decrease in transmittance. The devitrification temperature can be measured by the following method. A sample glass was crushed to obtain glass particles that passed through a 4 mm sieve and remained on a 2 mm sieve. These glass particles were immersed in ethanol, ultrasonically cleaned, and then dried in a dryer. Approximately 5 g of the dried glass particles were placed in a platinum dish and held at temperatures from 1000°C to 1400°C in 10°C increments for one hour. The glass particles were then allowed to cool naturally, and the presence or absence of crystal precipitation was observed under a microscope. The lowest temperature at which crystals with a long side or major axis of 1 μm or more were not observed was determined as the devitrification temperature.

[0047] (Coefficient of Linear Thermal Expansion) The coefficient of linear thermal expansion α of the glass 10 is 94×10 －７ / °C or less, and 93 x 10 －７ / °C or less is more preferable, and 92 × 10 －７ / °C or less is more preferable, and 91 x 10 －７ / °C or less. The linear thermal expansion coefficient α of the glass 10 is 86×10 －７ / °C or more is more preferable, and 87 x 10 －７ / °C or more. The linear thermal expansion coefficient α of the glass 10 is 86×10 －７ / ℃ or more 93 x 10 －７ / °C or less is more preferable, and 86 x 10 －７ / ℃ or more 91 x 10 －７ / °C or less is more preferable, and 87 x 10 －７ / ℃ or more 92 x 10 －７ / °C or less is more preferable, and 87 x 10 －７ / ℃ or more 90 x 10 －７ / °C or less is even more preferable. By setting the linear thermal expansion coefficient in this range, deflection can be appropriately suppressed. The linear thermal expansion coefficient α is the average thermal expansion coefficient in the range of 100°C to 300°C, and is a value measured in accordance with DIN-51045-1 as a standard for thermal expansion measurement. For example, measurement is performed in the range of 30°C to 400°C using a thermal dilatometer DIL 402 Expedis Supreme manufactured by NETZSCH as a measuring device, and the average thermal expansion coefficient in the range of 100°C to 300°C may be taken as the linear thermal expansion coefficient.

[0048] (Young's Modulus E) The Young's modulus E of the glass 10 is preferably 125 GPa or more, more preferably 127 GPa or more, and even more preferably 130 GPa or more. The Young's modulus E of the glass 10 is preferably 145 GPa or less, more preferably 142 GPa or less, and even more preferably 140 GPa or less. The Young's modulus E of the glass 10 is preferably 125 GPa or more and 145 GPa or less, more preferably 127 GPa or more and 142 GPa or less, and even more preferably 130 GPa or more and 140 GPa or less. Such a high Young's modulus can appropriately suppress breakage of the glass 10. The Young's modulus can be measured based on the propagation of ultrasonic waves using a 38DL PLUS manufactured by Olympus Corporation.

[0049] (Specific Gravity d) The specific gravity d of the glass 10 is 5.5 g / cm ３ It is preferable that the density is 5.4 g / cm or less. ３ More preferably, 5.3 g / cm ３ It is preferable that the density is 5.2 g / cm or less. ３ It is even more preferable that the specific gravity is equal to or less than 0.5 g / cm. Such a low specific gravity makes it easy to handle the glass 10. The specific gravity d can be measured by Archimedes' method.

[0050] (Glass Form) The glass 10 according to this embodiment is preferably an optical glass, and is preferably a glass plate having a thickness of 0.01 mm or more and 2.0 mm or less. A thickness of 0.01 mm or more can prevent breakage of the glass 10 during handling or processing. In addition, deflection of the glass 10 due to its own weight can be reduced. This thickness is more preferably 0.1 mm or more, even more preferably 0.2 mm or more, and even more preferably 0.3 mm or more. On the other hand, a thickness of 2.0 mm or less can reduce the weight of an optical element using the glass 10. This thickness is more preferably 1.5 mm or less, even more preferably 1.0 mm or less, and even more preferably 0.8 mm or less.

[0051] When the glass 10 according to this embodiment is a glass plate, the area of ​​the main surface is 8 cm ２ This area is preferably 8 cm or more. ２ If the area is more than 30 cm, a large number of optical elements can be arranged, improving productivity. ２ More preferably, it is 170 cm or more. ２ More preferably, it is 300 cm or more. ２ More preferably, it is 1000 cm ２ On the other hand, the area is 6500 cm ２ If the area is less than 4500 cm, the glass plate can be easily handled and breakage of the glass plate during handling or processing can be suppressed. ２ More preferably, it is 4000 cm or less. ２ and even more preferably 3000 cm ２It is particularly preferably 2000 cm ２ The following is the result.

[0052] When the glass 10 according to this embodiment is a glass plate, 25 cm ２ The LTV (Local Thickness Variation) in the above range is preferably 2 μm or less. By having a flatness in this range, it is possible to form a nanostructure of a desired shape on the main surface using imprinting technology or the like, and to obtain desired light-guiding characteristics. In particular, in a light guide, ghost phenomena and distortion due to differences in optical path length can be prevented. This LTV is more preferably 1.5 μm or less, even more preferably 1.0 μm or less, and particularly preferably 0.5 μm or less.

[0053] When the glass 10 according to this embodiment is formed into a circular glass plate having a diameter of 8 to 12 inches, the warpage is preferably 50 μm or less. If the warpage of this glass 10 is 50 μm or less, it is possible to form a nanostructure of a desired shape on the main surface using imprinting technology or the like, and the desired light guide characteristics can be obtained. When multiple light guides are to be obtained, they can be obtained with stable quality. The warpage of this glass 10 is more preferably 40 μm or less, even more preferably 30 μm or less, and particularly preferably 20 μm or less.

[0054] Furthermore, when the glass 10 according to this embodiment is formed into a circular glass plate with a diameter of 6 inches, the warpage is preferably 30 μm or less. If the warpage of this glass 10 is 30 μm or less, it is possible to form a nanostructure of a desired shape on the main surface using imprinting technology or the like, and the desired light-guiding characteristics can be obtained. When multiple light guides are to be obtained, they can be obtained with stable quality. The warpage of this glass 10 is more preferably 20 μm or less, even more preferably 15 μm or less, and particularly preferably 10 μm or less.

[0055] Furthermore, when the glass 10 according to this embodiment is a square glass plate with sides of 6 inches, the warpage is preferably 100 μm or less. If the warpage of this glass 10 is 100 μm or less, it is possible to form a nanostructure of a desired shape on the main surface using imprinting technology or the like, and the desired light-guiding characteristics can be obtained. When multiple light guides are to be obtained, they can be obtained with stable quality. The warpage of this glass 10 is more preferably 70 μm or less, even more preferably 50 μm or less, even more preferably 35 μm or less, and particularly preferably 20 μm or less.

[0056] 2 is a cross-sectional view of a glass plate made from the glass according to this embodiment. When the glass 10 according to this embodiment is used as a glass plate G1, the "warpage" refers to a difference C between a maximum value B and a minimum value A of a perpendicular distance between a reference line G1D of the glass plate G1 and a center line G1C of the glass plate G1 in an arbitrary cross section that passes through the center of a main surface G1F of the glass plate G1 and is perpendicular to the main surface G1F of the glass plate G1.

[0057] The intersection line between the arbitrary orthogonal cross section and the main surface G1F of the glass sheet G1 is defined as a base line G1A. The intersection line between the arbitrary orthogonal cross section and the other main surface G1G of the glass sheet G1 is defined as an upper line G1B. Here, the center line G1C is a line connecting the centers of the glass sheet G1 in the thickness direction. The center line G1C is calculated by finding the midpoint between the base line G1A and the upper line G1B with respect to the direction of laser irradiation, which will be described later.

[0058] The reference line G1D is determined as follows. First, a base line G1A is calculated based on a measurement method that cancels the influence of the weight. A straight line is determined from the base line G1A using the least squares method. The determined straight line is the reference line G1D. A known method is used as the measurement method that cancels the influence of the weight.

[0059] For example, the main surface G1F of the glass plate G1 is supported at three points, a laser is irradiated onto the glass plate G1 using a laser displacement meter, and the height of the main surface G1F and the other main surface G1G of the glass plate G1 from an arbitrary reference plane is measured.

[0060] Next, the glass sheet G1 is inverted, and three points on the other main surface G1G opposite to the three points where the one main surface G1F was supported are supported, and the heights of the main surface G1F and the other main surface G1G of the glass sheet G1 from an arbitrary reference plane are measured. The influence of the glass sheet's own weight is canceled out by averaging the heights of each measurement point before and after inversion. For example, before inversion, the height of the main surface G1F is measured as described above. After inverting the glass sheet G1, the height of the other main surface G1G is measured at a position corresponding to the measurement points on the main surface G1F. Similarly, before inversion, the height of the other main surface G1G is measured. After inverting the glass sheet G1, the height of the main surface G1F is measured at a position corresponding to the measurement points on the other main surface G1G. The warpage is measured, for example, using a laser displacement meter.

[0061] Furthermore, in the glass 10 according to this embodiment, the surface roughness Ra of the main surface is preferably 2 nm or less. Having an Ra in this range allows for the formation of a nanostructure of a desired shape on the main surface using imprinting technology or the like, and also allows for the attainment of desired light-guiding characteristics. In particular, in a light guide, diffuse reflection at the interface is suppressed, preventing ghosting and distortion. This Ra is more preferably 1.7 nm or less, even more preferably 1.4 nm or less, even more preferably 1.2 nm or less, and particularly preferably 1 nm or less. Here, the surface roughness Ra is the arithmetic mean roughness defined in JIS B0601 (2001). In this specification, the surface roughness Ra is a value measured over an area of ​​10 μm × 10 μm using an atomic force microscope (AFM).

[0062] (Method for Producing Glass) The method for producing the glass 10 according to this embodiment is not particularly limited, but a preferred method for producing the glass 10 will be described below.

[0063] In this embodiment, the manufacturing method includes a mixing step of mixing raw materials for the glass 10, a melting step of melting the raw materials, and a cooling step of cooling the melted raw materials to obtain the glass 10. In this manufacturing method, existing methods for manufacturing flat glass can be used. For example, known methods such as the float method, the fusion method, and the roll-out method can be used.

[0064] (Mixing Step) The raw materials of the glass 10 are selected according to the composition of the desired glass 10, and are mixed in a compounding ratio according to the composition of the desired glass 10. In this embodiment, the raw materials of the glass 10 include at least a raw material containing La, a raw material containing B, and SO ３ A raw material containing H ２ The raw materials containing La, the raw materials containing B, and SO are prepared and mixed. ３ A raw material containing H ２ The raw materials containing O are not limited to being different raw materials, and at least two of them may be the same raw material. ２ As raw materials containing O, B and H ２ Alternatively, the raw materials of the glass 10 may be a raw material containing La, a raw material containing B, and SO ３ A raw material containing H ２ The raw materials are not limited to those containing O, and other raw materials may be used depending on the composition of the glass 10 desired to be obtained.

[0065] (La-containing raw material) The La-containing raw material is a simple substance of La or a compound of La, and is preferably a compound of La. Examples of the La-containing raw material include La ２ O ３ is preferably used.

[0066] (Raw material containing B) The raw material containing B is a simple substance of B or a compound of B, and is preferably a compound of B. Examples of the raw material containing B include B ２ O ３ and H ３ BO ３ It is preferable to use at least one of B ２ O ３ In a glass composition containing 7 wt % or more of H ３ BO ３ is more preferably used.

[0067] (SO ３ Raw materials containing SO ３ The raw material containing SO ３(containing at least one S and three O), and more preferably sulfate. ３ Examples of raw materials containing La include ２ (SO ４ ) ３ ・9H ２ O, and Zr(SO ４ ) ２ ・4H ２ It is preferable that at least one of O is used.

[0068] (H ２ Raw materials containing O) H ２ Raw materials containing O are those that are burned to produce H ２ In other words, it is a compound that contains at least two H atoms and one O atom. ２ The raw material containing O is H ３ BO ３ It is preferable to use at least one of La, hydrate, and organic material. However, care must be taken when using raw materials containing HO, as this may worsen the melting property and worsen the transmittance. As the hydrate, the above-mentioned La, which has good melting property, is preferable. ２ (SO ４ ) ３ ・9H ２ Hydrates of sulfates such as La(NO ３ ) ３ ・4H ２ Preferred organic substances are hydrates of nitrates such as glucose C ６ H １２ O ６ Sugars such as B are preferred. ２ O ３ In the glass composition containing 7 wt% or more of H ３ BO ３ It is more preferable to use

[0069] (H ２ O addition ratio) Here, the mass ratio is the ratio of the total mass of the glass 10 based on the oxides. ２ Ratio of the amount of added O (H ２ O addition amount / total glass mass) is calculated by ２ O addition ratio. ２The amount of O added is the amount of H added in the mixing step. ２ Among raw materials containing O, H ２ It refers to the mass of the O component, in other words, H ２ From raw materials containing O, ２ It refers to the mass of the components excluding components other than O. For example, H ２ H as a raw material containing O ３ BO ３ When using H ３ BO ３ Of B ２ O ３ The mass of the components excluding H ２ H from raw materials containing O ２ O (3H ２ Therefore, for example, the mass of H relative to the total mass of the glass 10 based on oxides is ３ BO ３ (H ２ When the ratio of the amount of added raw material containing O) is 18.66 wt%, H ２ The O addition ratio is B ２ O ３ Excluding this, the total is 8.16 wt%.

[0070] In this case, H ２ The O addition ratio is preferably 5 wt% or more, more preferably 6 wt% or more, and even more preferably 7 wt% or more. ２ The O addition ratio is preferably 20 wt% or less, more preferably 15 wt% or less, and even more preferably 10 wt% or less. ２ The O addition ratio is preferably 5 wt% or more and 20 wt% or less, more preferably 6 wt% or more and 15 wt% or less, and even more preferably 7 wt% or more and 10 wt% or less. ２ When the lower limit of the O addition ratio is within this range, the glass melt of the glass 10 can contain an appropriate amount of water, and the SO ３ Even when a raw material containing H is added, an appropriate reducing atmosphere is created, so that Pt elution from the Pt device can be reduced and the decrease in transmittance can be suppressed. ２By setting the upper limit of the O addition ratio within this range, appropriate melting properties can be achieved. Note that βOH evaluated in a glass state is an index of the amount of water remaining in the molding process, and in order to evaluate the water content itself during glass melting in the fining process where Pt dissolution progresses most, H ２ It is more preferable to take into consideration the O addition ratio.

[0071] (SO ３ Addition ratio) Here, the mass ratio is the ratio of the total mass of the glass 10 based on oxides to the total mass of the glass 10 based on oxides. ３ The ratio of the amount of addition (SO ３ The amount of addition / total mass of glass) is calculated by ３ Addition ratio: SO ３ The amount of SO added is the amount of SO mixed in the mixing process. ３ Among the raw materials containing SO ３ In other words, SO ３ From a raw material containing SO ３ This refers to the mass of the components excluding components other than SO ３ The addition ratio is preferably 0.3 wt% or more, more preferably 0.5 wt% or more, and even more preferably 0.7 wt% or more. ３ The addition ratio is preferably 2.5 wt% or less, more preferably 2.2 wt% or less, preferably 2.0 wt% or less, more preferably 1.5 wt% or less, and even more preferably 1.0 wt% or less. ３ The addition ratio is preferably 0.3 wt% or more and 2.0 wt% or less, more preferably 0.5 wt% or more and 1.5 wt% or less, even more preferably 0.7 wt% or more and 1.3 wt% or less, and even more preferably 0.7 wt% or more and 1.0 wt% or less. ３ By setting the lower limit of the addition ratio within this range, it is possible to appropriately suppress the inclusion of bubbles in the glass 10. Furthermore, it contributes to lowering the melting temperature during glass melting, making it possible to suppress the elution of the Pt component and appropriately suppress the transmittance. ３ By setting the upper limit of the addition ratio within this range, the decrease in the transmittance of the glass 10 can be more appropriately suppressed.

[0072] (Melting Process) In the melting process, the raw materials are placed in a container such as a crucible, and the raw materials placed in the container are heated to melt the raw materials. Any material may be used as the container, but in this embodiment, a container containing Pt is used. The heating temperature when melting the raw materials is preferably 1350°C or less, more preferably 1330°C or less, and even more preferably 1300°C or less. The heating temperature when melting the raw materials is preferably 1250°C or more, and more preferably 1270°C or more. The heating temperature when melting the raw materials is preferably 1350°C or less, more preferably 1250°C or more to 1330°C or less, and even more preferably 1270°C or more to 1300°C or less. By setting the heating temperature within this range, defects such as foreign matter and bubbles are eliminated, and furthermore, dissolution of the Pt contained in the container is suppressed, thereby appropriately suppressing a decrease in transmittance.

[0073] (Effects) As described above, the glass 10 according to the first aspect of the present disclosure has La ２ O ３ , and B ２ O ３ The mass ratio of S is 100 ppm or more, the internal transmittance for light with a wavelength of 440 nm is 70% or more, and βOH is 0.1 mm －１ More than 1.0 mm －１ The glass 10 according to the present disclosure can suppress the inclusion of bubbles by containing S within the above range. ２ O ３ and B ２ O ３ When producing glass containing ３ The inventors have found that when a glass containing a raw material containing βOH (a raw material containing βOH), in other words, when S is contained in the glass, transmittance decreases. As a result of extensive research, the inventors have found that transmittance can be improved by increasing the amount of water contained in such glass. That is, by containing βOH in the above range, glass 10 according to the present disclosure can appropriately contain water while suppressing bubble generation, thereby suppressing a decrease in transmittance.

[0074] The glass 10 according to the second aspect of the present disclosure is the glass 10 according to the first aspect, except that the refractive index n ｄPreferably, the refractive index of glass 10 of the present disclosure is 1.95 or greater. Due to its high refractive index, glass 10 of the present disclosure can be suitably used as an optical element.

[0075] Glass 10 according to a third aspect of the present disclosure is glass 10 according to the first or second aspect, in which the ratio of the content of tetravalent Ti to the content of trivalent B is preferably not more than 3. With this composition, glass 10 of the present disclosure can appropriately achieve a high refractive index and high transmittance.

[0076] Glass 10 according to a fourth aspect of the present disclosure is glass 10 according to any one of the first to third aspects, further comprising, in a mass ratio based on oxides, SiO ２ , and B ２ O ３ The total content of is preferably 10% or more. With this composition, glass 10 of the present disclosure can appropriately achieve a high refractive index and high transmittance.

[0077] Glass 10 according to a fifth aspect of the present disclosure is glass 10 according to any one of the first to fourth aspects, wherein the specific gravity is 5.30 g / cm ３ Such a low specific gravity makes the glass 10 easy to handle.

[0078] Glass 10 according to a sixth aspect of the present disclosure is glass 10 according to any one of the first to fifth aspects, and preferably has a devitrification temperature of 1270° C. or less. Since glass 10 according to the present disclosure has a devitrification temperature of 1270° C. or less, the temperature at which raw materials are melted during the production of glass 10 can be kept relatively low, and a decrease in transmittance can be suppressed.

[0079] Glass 10 according to the seventh aspect of the present disclosure is glass 10 according to any one of the first to sixth aspects, and preferably does not contain Sb, thereby making it possible to appropriately achieve a high refractive index and high transmittance.

[0080] Glass 10 according to an eighth aspect of the present disclosure is the glass 10 according to any one of the first to seventh aspects, and is preferably used as a light guide plate. Glass 10 according to the present disclosure can be suitably used for a light guide plate.

[0081] The method for producing glass 10 according to the ninth aspect of the present disclosure is a method for producing glass 10 by adding a raw material containing La, a raw material containing B, and SO ３ A raw material containing H ２ The method includes mixing raw materials containing O with glass 10, heating the mixed raw materials to melt them, and cooling the melted raw materials to obtain glass, and the ratio of H to the total mass of the glass 10 based on oxides is 1:1. ２ The ratio of the amount of added O is 5 wt% or more and 20 wt% or less. ２ The raw material containing O is mixed. According to the present disclosure, it is possible to suppress a decrease in transmittance by appropriately incorporating moisture while reducing the time required for production.

[0082] A method for manufacturing glass 10 according to a tenth aspect of the present disclosure is a method for manufacturing glass 10 according to the ninth aspect, ２ The raw material containing O is boric acid (H ３ BO ３ ), hydrates, and organic substances. By using such raw materials, the glass 10 can appropriately contain moisture, thereby suppressing a decrease in transmittance.

[0083] A method for producing glass 10 according to an eleventh aspect of the present disclosure is a method for producing glass 10 according to the ninth or tenth aspect, wherein the amount of H relative to the total mass of glass 10 based on oxides is ２ The ratio of the amount of added O was 7 wt % or more. ２ It is preferable to mix a raw material containing O. ２ By setting the amount of O added within this range, the glass 10 can contain an appropriate amount of moisture, thereby suppressing a decrease in transmittance.

[0084] The method for producing glass 10 according to a twelfth aspect of the present disclosure is a method for producing glass 10 according to any one of the ninth to eleventh aspects, in which the mixed raw materials are preferably heated at 1350° C. or less. By setting the heating temperature within this range, it is possible to appropriately suppress a decrease in transmittance.

[0085] Examples Next, examples will be described. Tables 1 to 11 show the glasses of the respective examples. Note that the embodiments may be modified as long as the effects of the invention are achieved.

[0086]

[0087] (Example 1) In Example 1, glasses having thicknesses of 10 mm and 1 mm were produced with the composition shown in Table 1. Specifically, raw materials having the composition shown in Table 1 were uniformly mixed. At this time, in addition to the raw materials having the composition shown in Table 1, H ２ H as a raw material containing O ３ BO ３ And, H ２ It is a raw material containing O and SO ３ It is also a raw material containing La (it is also a raw material containing La) ２ (SO ４ ) ３ ・9H ２ O was also added. ２ The H O addition ratio was adjusted to the value shown in Table 1. ２ The amount of raw material containing O added is adjusted to ３ SO 4 was added so that the addition ratio was as shown in Table 1. ３ The amount of raw materials containing H in Table 1 was adjusted. ２ The O addition ratio I is H ２ H of raw material I containing O ２ The O addition ratio is H in Table 1. ２ The O addition ratio II is H ２ H of raw material II containing O ２ The O addition ratio is H in Table 1. ２ O addition ratio III is H ２ H of raw material III containing O ２ The O addition ratio is H in Table 1. ２ The total O addition ratio is ２ H for the total of raw materials including O ２O addition ratio. Next, the mixed raw materials were melted in a platinum crucible at 1330 ° C. for 2 hours to obtain a uniform molten glass. Next, the molten glass was poured into a carbon mold having a length x width x height of 60 mm x 50 mm x 30 mm. After that, it was held at 740 ° C. for 1 hour and then cooled to room temperature at a temperature decrease rate of about 1 ° C. / min to obtain a glass block. Next, the glass block was cut into a length x width of 30 mm x 30 mm using a cutting machine (a small cutting machine manufactured by Maruto Co., Ltd.), and the plate thickness was adjusted and the surface was polished using a grinding machine (SGM-6301 manufactured by Hidewa Kogyo Co., Ltd.) and a single-sided polishing machine (EJ-380IN manufactured by Engis Japan Co., Ltd.), and glass having a length x width of 30 mm x 30 mm and a plate thickness of 10 mm and 1 mm was produced.

[0088] The S content (S concentration) of the glass of Example 1 was measured. The measurement method was the same as that described in the above embodiment. The βOH of the glass of Example 1 was calculated. The calculation method was the same as that described in the above embodiment. The glass transition temperature Tg, the linear thermal expansion coefficient α in the range of 100°C to 300°C, the specific gravity d, and the refractive index n of the glass of Example 1 were calculated. ｄ , Abbe number v ｄ , internal transmittance (transmittance τ ４４０ The measurement methods used were the same as those described in the above embodiment. The measurement results are shown in Table 1.

[0089] (Examples 2 to 51) In Examples 2 to 51, glasses were produced in the same manner as in Example 1, except that the production conditions and compositions were as shown in Tables 1 to 11. The measurement results for the glasses of each example are shown in Tables 1 to 11. In Examples 2 to 51, the internal transmittance columns left blank indicated that the internal transmittance was 70% or higher.

[0090] (Evaluation) The glasses of each example were evaluated for bubbles and transmittance. In the bubble evaluation, a glass having fewer than 50 bubbles larger than 30 μm in 100 ml of molten glass was evaluated as ◯, and a glass having 50 or more bubbles was evaluated as ×. In the transmittance evaluation, a glass having transparency when visually observed under a fluorescent lamp was evaluated as ◯, and a glass having opacity was evaluated as ×.

[0091] As shown in Tables 1 to 11, Examples 31, 47, and 48, which are comparative examples, are SO ３Since the amount of SO added is small, bubbles remain and the evaluation of bubbles is "×". ３ Although the amount of SO was larger than in the other comparative examples, the value of βOH was relatively high compared to the S concentration, and the foaming bubbles resulted in an evaluation of "x". ３ is not added, resulting in poor melting properties and poor permeability. As described above, in Examples 31 to 33 and Examples 47 to 48, at least one of the bubble evaluation and the permeability evaluation was poor, indicating that the inclusion of bubbles cannot be suppressed while the decrease in permeability cannot be suppressed. In Examples 1 to 30, Examples 34 to 46, and Examples 49 to 51, which are working examples, both the bubble evaluation and the permeability evaluation were good, indicating that the inclusion of bubbles can be suppressed while the decrease in permeability can be suppressed.

[0092] Although the embodiments of the present invention have been described above, the embodiments are not limited to the contents of these embodiments. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the scope of what is called equivalents. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiments.

[0093] 10. Glass

Claims

1. La ２ O ３ , and B ２ O ３ The content of S is 100 ppm or more by mass ratio, the internal transmittance for light with a wavelength of 440 nm is 70% or more, and βOH is 0.1 mm －１ More than 1.0 mm －１ Below is the glass.

2. Refractive index n ｄ 2. The glass of claim 1 , wherein 3. Mass ratio: B ２ O ３ TiO ２ The content ratio of TiO ２ / B ２ O ３ 3. The glass of claim 1 , wherein n is 3 or less.

4. Mass ratio based on oxide: SiO ２ , and B ２ O ３ The glass according to claim 1 or 2, wherein the total content of is 10% or more.

5. Specific gravity is 5.30 g / cm ３ 3. The glass of claim 1 or claim 2, wherein:

6. The glass according to claim 1 or 2, having a devitrification temperature of 1270°C or lower.

7. The glass according to claim 1 or 2, which does not contain Sb.

8. The glass according to claim 1 or 2, which is used as a light guide plate.

9. A raw material containing La, a raw material containing B, and SO ３ A raw material containing H ２ The method includes mixing a raw material containing O with a raw material containing H, heating the mixed raw material to melt it, and cooling the melted raw material to obtain glass, and the ratio of H to the total mass of the glass based on oxides is ２ The ratio of the amount of added O is 5 wt % or more and 20 wt % or less. ２ A method for producing glass, comprising mixing raw materials containing O.

10. H ２ The method for producing glass according to claim 9 , wherein the raw material containing O is at least one of boric acid, a hydrate, and an organic substance.

11. H based on the total mass of the glass on an oxide basis ２ The ratio of the amount of added O was 7 wt % or more. ２ The method for producing glass according to claim 9 or 10, further comprising mixing a raw material containing O.

12. The method for producing glass according to claim 9 or 10, wherein the mixed raw materials are heated at 1,350° C. or lower.