Optical Glass

Abstract

The present invention provides optical glass which has excellent light transmittance characteristics in the visible light region and devitrification resistance and has high refractive index characteristics.　This optical glass is characterized by containing, in terms of mass%, 3-18% of SiO2, 5-11.5% of B2O3, 0-7% of Al2O3, 0-11% of CaO, at most 1% of ZnO, 7-20% of TiO2, 3-38% of Nb2O5, 27-49.8% of La2O3, 6-14% of Gd2O3, 0-5% of Y2O3, below 6% of Ta2O5, and at most 0.6% of WO3, wherein B2O3 / SiO2 is 1-2.

Description

[Technical field]

[0001] The present invention relates to an optical glass used in optical elements such as lenses.

[0002] Glass materials are used as optical elements such as lenses in wearable devices such as glasses with projectors, eyeglass-type or goggle-type displays, virtual reality or augmented reality display devices, and virtual image display devices. The glass materials are required to have high refractive index properties in terms of widening the angle of images, increasing brightness and contrast, improving light guide properties, and the like. In addition, imaging glass lenses that are small and have a wide imaging angle are used for applications such as in-vehicle cameras and visual sensors for robots (see, for example, Patent Document 1). High refractive index properties are also required for such imaging glass lenses. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-74572 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the past, when a glass composition with a high refractive index was prepared, an element having absorption in the visible range was often used as a component for increasing the refractive index. Therefore, in general, high refractive index glass has a problem of low light transmittance in the visible range. In addition, when a glass composition with a high refractive index was prepared, the components constituting the glass skeleton tended to decrease. Therefore, in general, high refractive index glass has a problem of being easily devitrified and poor in mass productivity.

[0005] In view of the above, an object of the present invention is to provide an optical glass that has excellent light transmittance characteristics in the visible range, excellent resistance to devitrification, and a high refractive index. [Means for solving the problem]

[0006] As a result of extensive investigations by the present inventors, TiO 2 , Nb 2 O 5 , La 2 O 3 , Gd 2 O 3 It contains high refractive index components such as SiO, which contributes to vitrification stability. 2 and B. 2 O 3 It has been found that the above problems can be solved by strictly controlling the content of

[0007] That is, the optical glass of the present invention contains, in mass %, SiO 2 3-18%, B 2 O 3 5-11.5% Al 2 O 3 0~7%, CaO 0~11%, ZnO 1% or less, TiO 2 7-20%, Nb 2 O 5 3-38%, La 2 O 3 27-49.8%, Gd 2 O 3 6-14%, Y 2 O 3 0~5%, Ta 2 O 5 Less than 6%, WO 3 Contains 0.6% or less, B 2 O 3 / SiO 2 It is characterized in that 1 to 2.

[0008] The optical glass of the present invention comprises, in mass %, Ln 2 O 3 It is preferable that Ln contains 36% or more (wherein Ln is at least one selected from La, Gd, Y and Yb).

[0009] The optical glass of the present invention preferably contains, in mass %, 0 to less than 0.2% BaO.

[0010] The optical glass of the present invention preferably has a refractive index (nd) of 1.84 to 2.04.

[0011] The optical glass of the present invention preferably has a liquidus temperature of 1150° C. or lower.

[0012] The optical glass of the present invention preferably has an in-line transmittance of 72% or more at a wavelength of 500 nm and a thickness of 5 mm.

[0013] The optical element of the present invention is characterized by being made of the above-mentioned optical glass. Effect of the Invention

[0014] According to the present invention, it is possible to provide an optical glass that has excellent light transmittance characteristics in the visible range and resistance to devitrification, and also has high refractive index characteristics. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The optical glass of the present invention is composed of, in mass %, SiO 2 3-18%, B 2 O 3 5-11.5% Al 2 O 3 0~7%, CaO 0~11%, ZnO 1% or less, TiO 2 7-20%, Nb 2 O 5 3-38%, La 2 O 3 27-49.8%, Gd 2 O 3 6-14%, Y 2 O 3 0~5%, Ta 2 O 5 Less than 6%, WO 3 Contains 0.6% or less, B 2 O 3 / SiO 2 It is characterized in that the glass composition is 1 to 2. The reasons for limiting the glass composition in this way are explained below. In the following explanation of the content of each component, "%" means "mass %" unless otherwise specified.

[0016] SiO 2is a glass framework component that improves the stability of vitrification and chemical durability. SiO 2 The content of SiO is 3 to 18%, preferably 3.5 to 15%, 4 to 12%, and particularly preferably 5 to 10%. 2 If the content of SiO is too low, it becomes difficult to obtain the above effects. 2 If the content is too high, the refractive index tends to decrease.

[0017] B 2 O 3 is a component that contributes to the stability of vitrification. 2 O 3 The content of is 5 to 11.5%, preferably 6.5 to 11.5%, 7 to 11%, 8 to 10.5%, and particularly preferably 9 to less than 10.5%. 2 O 3 If the content of B is too small, it becomes difficult to obtain the above effect. 2 O 3 If the content is too high, the refractive index decreases and the chemical durability tends to decrease.

[0018] In order to increase the stability of vitrification and improve mass productivity, SiO 2 and B 2 O 3 It is preferable to appropriately adjust the ratio of B. 2 O 3 / SiO 2 is 1 to 2, preferably 1.3 to 1.99, and particularly preferably 1.5 to 1.98. In this specification, "X / Y" means the value obtained by dividing the content of X by the content of Y.

[0019] Al 2 O 3 Al is a component that improves water resistance. However, if its content is too high, the glass becomes more susceptible to devitrification. 2 O 3 is 0 to 7%, preferably 0 to 5%, 0 to 2%, and particularly preferably 0 to 1%.

[0020] Among alkaline earth metal oxides, CaO is a component that is particularly likely to contribute to glass stabilization. However, if the content is too high, the refractive index tends to decrease. Therefore, the CaO content is 0 to 11%, and preferably 0.1 to 9%, 1 to 8%, 2 to 7%, and particularly preferably 3 to 6%.

[0021] In the composition of the present invention, ZnO is a component that promotes devitrification, and therefore its content is preferably small. Specifically, the ZnO content is 1% or less, preferably 0.5% or less, and more preferably 0.1% or less, and particularly preferably zero.

[0022] TiO 2 is a component that increases the refractive index of glass. It also has the effect of improving chemical durability. 2 The content of TiO is 7 to 20%, preferably 8 to 18%, 9 to 17%, and particularly preferably 10 to 16%. 2 If the content of TiO is too low, it becomes difficult to obtain the above-mentioned effect. 2 If the content is too high, the transmittance of the glass in the visible range decreases, and the stability of vitrification also tends to decrease.

[0023] Nb 2 O 5 is a component that increases the refractive index of glass. 2 O 5 The Nb content is 3 to 38%, preferably 4 to 30%, 5 to 19%, 6 to 14%, and particularly preferably 7 to 10%. 2 O 5 If the content of Nb is too small, it becomes difficult to obtain the above effects. 2 O 5 If the content is too high, the resistance to devitrification decreases, which tends to reduce mass productivity, and the light transmittance in the visible range also tends to decrease.

[0024] La 2 O 3 La is a component that increases the refractive index and also improves the stability of vitrification. 2 O 3The content of La is 27 to 49.8%, preferably 30 to 49.5%, 35 to 49%, and particularly preferably 38 to 48.5%. 2 O 3 If the content of La is too low, it becomes difficult to obtain the above effects. 2 O 3 If the content is too high, devitrification is likely to occur, and the resistance to devitrification decreases, which tends to make mass production difficult.

[0025] Gd 2 O 3 Gd is also a component that increases the refractive index and improves the stability of vitrification. 2 O 3 The content is 6 to 14%, preferably 6 to 10%, and particularly preferably 6 to 9%.

[0026] Y 2 O 3 Y is a component that improves the stability of vitrification without decreasing the refractive index. However, if its content is too high, devitrification and striae are likely to occur. 2 O 3 The content is 0 to 5%, preferably 0.1 to 4%, 0.3 to 2%, 0.4 to 1%, and particularly preferably 0.5 to 0.8%.

[0027] Ta 2 O 5 is a component that increases the refractive index. However, if its content is too high, phase separation and devitrification tend to occur. 2 O 5 Since Ta is a rare and expensive component, if its content is high, the raw material batch cost will be high. 2 O 5 The content of is less than 6%, preferably 3% or less, 1% or less, and particularly preferably zero.

[0028] WO 3 Although it is a component that increases the refractive index, it also tends to decrease the light transmittance in the visible region. Therefore, its content is 0.6% or less, preferably 0.5% or less, more preferably 0.3% or less, and it is particularly preferable that it is not contained.

[0029] The optical glass of the present invention may contain the following components in addition to the above components.

[0030] Yb 2 O 3 is a component that increases the refractive index. However, if its content is too high, devitrification and striae are likely to occur. 2 O 3 The content is preferably 0 to 10%, more preferably 0 to 8%.

[0031] ZrO 2 is a component that increases the refractive index and chemical durability. 2 The content of ZrO is preferably 0 to 10%, 1 to 9%, 3 to 8%, 4 to 7.5%, and particularly preferably 5 to 7%. 2 If the content is too high, devitrification tends to occur.

[0032] SrO is a component that contributes to the stability of vitrification. However, if the content is too high, the refractive index tends to decrease. Therefore, the SrO content is preferably 0 to 11%, 0.1 to 9%, and particularly preferably 1 to 8%.

[0033] BaO is a component that contributes to the stability of vitrification and increases the refractive index. However, when BaO is contained, the density of the glass increases, and the weight of the optical element made of the optical glass of the present invention tends to increase. Therefore, it is not preferable for use in wearable devices and the like. Therefore, the content of BaO is preferably 1% or less, 0.5% or less, or 0.2% or less, and it is particularly preferable that BaO is not contained.

[0034] Li 2 O, Na 2 OK 2 O is a component that lowers the softening point, but if its content is too high, devitrification tends to occur. Therefore, the contents of these components are preferably 0 to 3%, and 0 to 1%, respectively, and it is particularly preferable that they are not contained.

[0035] Ln 2 O 3It is preferable that Ln is 36% or more, 40% or more, 45% or more, and particularly 48% or more. In this way, it is possible to increase the refractive index and the light transmittance in the visible range. 2 O 3 The upper limit of the content of Ln is not particularly limited, but if it is too high, devitrification is likely to occur, so it is preferably 70% or less, 65% or less, and particularly preferably 60% or less. 2 O 3 In the formula, Ln is at least one selected from La, Gd, Y, and Yb. That is, Ln 2 O 3 La 2 O 3 , Gd 2 O 3 , Y 2 O 3 and Yb 2 O 3 This means the total amount of.

[0036] In the present invention, in order to obtain a glass having a high refractive index and excellent vitrification stability, SiO 2 and B 2 O 3 The total amount of and Ln 2 O 3 It is preferable to appropriately adjust the ratio of (SiO 2 +B 2 O 3 ) / Ln 2 O 3 is preferably 0.15 to 0.9, more preferably 0.2 to 0.6, and even more preferably 0.25 to 0.5. In this specification, "X+Y+···" means the total amount of each component.

[0037] In the present invention, in order to obtain a glass having a high refractive index and excellent transmittance in the visible range, Nb 2 O 5 , TiO 2 , WO 3 It is preferable to appropriately adjust the ratio of Nb 2 O 5 / (Nb 2 O 5 +TiO 2 +WO 3) is preferably 0.15 to 0.8, more preferably 0.2 to 0.6, and particularly preferably 0.3 to 0.5.

[0038] In order to obtain glass with a high refractive index and excellent transmittance in the visible range, TiO 2 and Nb 2 O 5 It is preferable to appropriately adjust the ratio of TiO 2 / Nb 2 O 5 is preferably at least 0.3, at least 0.5, at least 0.8, particularly at least 1. If this ratio is too small, it becomes difficult to obtain the above effects, and vitrification tends to become unstable.

[0039] In the present invention, in order to obtain glass having excellent transmittance in the visible range, TiO 2 , WO 3 and Nb 2 O 5 It is preferable to appropriately adjust the total amount of TiO 2 +WO 3 +Nb 2 O 5 is preferably 45% or less, 30% or less, 27% or less, and particularly preferably 25% or less.

[0040] In the present invention, in order to increase the refractive index and the light transmittance in the visible range and to improve the stability of vitrification, Y 2 O 3 and Ln 2 O 3 It is preferable to appropriately adjust the ratio of Y 2 O 3 / Ln 2 O 3 is preferably 0 to 0.1, more preferably 0.005 to 0.05, and particularly preferably 0.01 to 0.3.

[0041] In the present invention, in order to increase the refractive index and the light transmittance in the visible range and to improve the stability of vitrification, Gd 2 O 3 and Ln 2 O 3It is preferable to appropriately adjust the ratio of Gd 2 O 3 / Ln 2 O 3 is preferably 0.1 to 0.25, and particularly preferably 0.12 to 0.2.

[0042] In the present invention, in order to obtain a glass having a high refractive index and excellent transmittance in the visible range, Nb 2 O 5 , TiO 2 , ZrO 2 , WO 3 , Ln 2 O 3 It is preferable to appropriately adjust the ratio of Nb 2 O 5 / (Nb 2 O 5 +TiO 2 +ZrO 2 ) is preferably 0.1 to 0.46, more preferably 0.15 to 0.4, and particularly preferably 0.2 to 0.37.

[0043] In the present invention, in order to increase the refractive index and the light transmittance in the visible range and to improve the stability of vitrification, TiO 2 and B. 2 O 3 The total amount of WO 3 and Nb 2 O 5 It is preferable to appropriately adjust the ratio of the total amount of (TiO 2 +B 2 O 3 ) / (WO 3 +Nb 2 O 5 ) is preferably 1.6 to 4, particularly preferably 2 to 3.5.

[0044] In the present invention, in order to enhance the stability of vitrification, the total amount of CaO, SrO, BaO and ZnO and Nb 2 O 5 , La 2 O 3 , TiO 2 and ZrO 2It is preferable to appropriately adjust the ratio of the total amount of (CaO+SrO+BaO+ZnO) / (TiO 2 +Nb 2 O 5 +La 2 O 3 +ZrO 2 ) is preferably 0 to 0.6, more preferably 0.01 to 0.4, and particularly preferably 0.03 to 0.3.

[0045] In addition, the As component (As 2 O 3 It is preferable not to contain Pb components (PbO, etc.) because they have a large environmental impact.

[0046] The refractive index (nd) of the optical glass of the present invention is preferably 1.84 to 2.04, 1.88 to 2.01, and particularly preferably 1.89 to 2.00. The optical glass of the present invention also has a light transmittance in the visible range, in terms of a light transmittance (linear transmittance) at a wavelength of 500 nm at a thickness of 5 mm, of preferably 72% or more, more preferably 74% or more, and even more preferably 75% or more. By satisfying the above optical properties, the optical glass of the present invention is suitable as an optical element such as a small imaging glass lens capable of capturing a wide range of images.

[0047] The Abbe number (νd) of the optical glass of the present invention is not particularly limited, but in consideration of the stability of vitrification, it is preferably 39 or less, 35 or less, particularly 31 or less, and further preferably 30 or less.

[0048] The partial dispersion ratio (θg, F) ​​of the optical glass of the present invention is preferably 0.615 or less, more preferably 0.61 or less, and even more preferably 0.6 or less. If the partial dispersion ratio is too large, chromatic aberration is likely to occur.

[0049] The liquidus temperature of the optical glass of the present invention is preferably not higher than 1150° C., not higher than 1100° C., and particularly not higher than 1070° C. This makes it less susceptible to devitrification during melting or molding, which tends to improve mass productivity. EXAMPLES

[0050] The present invention will be described in detail below using examples, but the present invention is not limited to these examples.

[0051] Tables 1 and 2 show examples (Nos. 1 to 10) of the present invention.

[0052] [Table 1]

[0053] [Table 2]

[0054] First, glass raw materials were mixed to obtain the compositions shown in Tables 1 and 2, and melted in a platinum crucible at 1200 to 1350°C for 2 hours. The molten glass was poured onto a carbon plate and annealed by holding it at 700 to 800°C for 2 to 72 hours, after which samples suitable for each measurement were prepared.

[0055] The refractive index (nd), Abbe number (νd), light transmittance, and liquidus temperature of the obtained sample were measured. The results are shown in Tables 1 and 2.

[0056] The refractive index was measured using the d-line (587.6 nm) of a helium lamp.

[0057] The Abbe number was calculated from the formula (νd) = [(nd-1) / (nF-nC)] using the refractive index of the d-line, the F-line (486.1 nm) of a hydrogen lamp, and the C-line (656.3 nm) of a hydrogen lamp.

[0058] The liquidus temperature was measured by remelting the glass in an electric furnace at 1200°C for 0.5 hours, holding it in an electric furnace with a temperature gradient for 18 hours, removing it from the electric furnace and allowing it to cool in air, and then determining the position of devitrified matter precipitation using an optical microscope.

[0059] The linear transmittance was measured as follows. For an optically polished sample having a thickness of 5 mm±0.1 mm, the linear transmittance including the surface reflection loss was measured at 0.5 nm intervals using a spectrophotometer (Shimadzu Corporation UV-3100). The linear transmittance at a wavelength of 500 nm was read from the light transmittance curve obtained by the measurement.

[0060] As shown in Tables 1 and 2, the samples Nos. 1 to 10 of the examples exhibited desired optical properties, and also had excellent resistance to devitrification, with a low liquidus temperature of 1150° C. or lower. In addition, the linear transmittance at a wavelength of 500 nm was good, being 73% or higher.

Claims

1. In mass%, SiO ２ 3-18%, B ２ O ３ 5-11.5%, Al ２ O ３ 0-7%, CaO 0-11%, ZnO 1% or less, TiO ２ 10-20%, Nb ２ O ５ 3-38%, La ２ O ３ 27-49.8%, Gd ２ O ３ 6-14%, Y ２ O ３ 0-5%, Ta ２ O ５ Less than 6%, WO ３ Contains 0.6% or less, BaO 0 to less than 0.2%, and B ２ O ３ / SiO ２ 1 or 2, and having a liquidus temperature of 1150° C. or lower.

2. In mass%, Ln ２ O ３ 2. The optical glass according to claim 1, wherein Ln is at least one element selected from the group consisting of La, Gd, Y and Yb.

3. 3. The optical glass according to claim 1, wherein the refractive index (nd) is 1.84 to 2.

04.

4. 4. The optical glass according to claim 1, wherein the optical glass has an in-line transmittance of 72% or more at a wavelength of 500 nm and a thickness of 5 mm.

5. 5. An optical element comprising the optical glass according to claim 1.

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