Optical Glass and Optical Elements

Abstract

To provide an optical glass having a desired optical constant, a low temperature coefficient of a relative refractive index (dn / dT) due to a temperature change, and a large average linear thermal expansion coefficient, and an optical element that comprises the optical glass.SOLUTION: An optical glass has a refractive index nd of 1.63-1.80 and an Abbe number νd of 22-34. An Nb2O5 content is 25-55 mass%. A WO3 content is less than 30 mass%. A total content of TiO2, Nb2O5, WO3, Bi2O3 and Ta2O5 [TiO2+Nb2O5+WO3+Bi2O3+Ta2O5] is 36-60 mass%. A mass ratio of a total content of TiO2, Nb2O5, WO3, Bi2O3 and Ta2O5 to a total content of P2O5, B2O3, SiO2, Al2O3, Li2O, Na2O, K2O and Cs2O [(TiO2+Nb2O5+WO3+Bi2O3+Ta2O5) / (P2O5+B2O3+SiO2+Al2O3+Li2O+Na2O+K2O+Cs2O)] is 1.10 or less. A mass ratio of a content of TiO2 to a total content of P2O5 and B2O3 [TiO2 / (P2O5+B2O3)] is 0.50 or less. The optical glass satisfies (A) or (B).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to optical glass and optical elements.

Background Art

[0002] Optical elements incorporated in in-vehicle optical devices and optical elements incorporated in optical devices that generate heat, such as projectors, copy machines, laser printers, and broadcast equipment, are used in environments with greater temperature changes. When optical properties such as refractive index vary due to temperature changes, it affects imaging properties of the optical system and the like.

[0003] Here, it is known that by combining an optical element having a negative temperature coefficient of relative refractive index (dn / dT) and an optical element having a positive temperature coefficient of relative refractive index, the influence on imaging properties of the optical system and the like can be reduced.

[0004] The temperature coefficient of relative refractive index (dn / dT) represents the change in refractive index with respect to temperature change. In an optical element where the refractive index decreases when the temperature rises, the temperature coefficient of relative refractive index is negative. Conversely, in an optical element where the refractive index increases when the temperature rises, the temperature coefficient of relative refractive index is positive.

[0005] In addition, when the melting temperature and forming temperature of the glass are high, not only is the productivity poor, but the glass melting equipment (for example, crucibles, stirring equipment for molten glass, etc.) in the melting process is eroded, and the economic efficiency is also poor. Therefore, a glass with a low liquidus temperature LT, that is, a glass with a low melting temperature and forming temperature of the glass, is required.

[0006] Patent Document 1 discloses an optical glass having a negative temperature coefficient of relative refractive index (dn / dT). However, it has been found that the glass of Patent Document 1 has a high liquidus temperature LT and is inferior in productivity and economic efficiency.

[0007] In addition, the average linear thermal expansion coefficient of the optical element is important in optical design. When combining a low refractive index and low dispersion optical glass with a high refractive index and high dispersion optical glass, the smaller the difference in the average linear thermal expansion coefficient of the optical glasses, the better the bonding. For example, low refractive index and low dispersion optical glasses containing fluorine usually have a large average linear thermal expansion coefficient. Therefore, the high refractive index and high dispersion optical glass combined with it is also required to have a high average linear thermal expansion coefficient. The optical glass disclosed in Patent Document 2 has a high refractive index but low dispersion and a small average linear thermal expansion coefficient. Therefore, there is a need for an optical glass that has a high refractive index and high dispersion and a large average linear thermal expansion coefficient.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, an object of the present invention is to provide an optical glass having a desired optical constant, a low temperature coefficient (dn / dT) of relative refractive index due to temperature change, and a large average linear thermal expansion coefficient, and an optical element made of the optical glass.

Means for Solving the Problems

[0010] The gist of the present invention is as follows. (1) The refractive index nd is 1.63 to 1.80, the Abbe number νd is 22 to 34, Nb 2 O 5 content is 25 to 55% by mass, WO 3 content is less than 30% by mass, TiO 2 、Nb 2 O5 , WO 3 , Bi 2 O 3 and Ta 2 O 5 The total content of [TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 is 36 - 60% by mass, P 2 O 5 , B 2 O 3 , SiO 2 , Al 2 O 3 , Li 2 O, Na 2 O, K 2 O and Cs 2 The mass ratio of the total content of TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 and Ta 2 O 5 to the total content of [TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 ) / (P 2 O 5 + B 2 O 3 + SiO 2 + Al 2 O 3 + Li 2 O + Na 2 O + K 2 O + Cs 2 O)] is 1.10 or less, P 2 O 5 and B 2 O 3 The mass ratio of the content of TiO 2 to the total content of [TiO 2 / (P2 O 5 +B 2 O 3 )] is 0.50 or less, An optical glass satisfying the following (A) or (B). (A) The content of P 2 O 5 is 20 to 36% by mass, Li 2 O, Na 2 O, K 2 O and Cs 2 The mass ratio of P to the total content of 2 O 5 , B 2 O 3 and SiO 2 [(P 2 O 5 +B 2 O 3 +SiO 2 ) / (Li 2 O + Na 2 O + K 2 O + Cs 2 O)] is 1.50 or less, P 2 O 5 The mass ratio of the content of B to the content of 2 O 3 [B 2 O 3 / P 2 O 5 is 0.05 to 0.39, The total content of MgO, CaO, SrO and BaO [MgO + CaO + SrO + BaO] is 8.0% by mass or less. (B) P 2 O 5 The content of is 25 to 38% by mass, Al 2 O 3 The content of is less than 5% by mass, Li 2 O, Na 2 O, K 2 O and Cs 2 The mass ratio of P to the total content of 2 O 5 , B 2 O 3 and SiO2 The mass ratio of the total content of [(P 2 O 5 +B 2 O 3 +SiO 2 ) / (Li 2 O+Na 2 O+K 2 O+Cs 2 O)] is 1.80 or less, The total content of MgO, CaO, SrO and BaO [MgO+CaO+SrO+BaO] is 7.0% by mass or less, TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 and Ta 2 O 5 TiO relative to the total content 2 Mass ratio of the content [TiO 2 / (TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 +Ta 2 O 5 )] is 0.25 or greater.

[0011] (2) Li 2 O, Na 2 OK 2 O and Cs 2 P in relation to the total O content 2 O 5 , B 2 O 3 and SiO 2 The mass ratio of the total content of [(P 2 O 5 +B 2 O 3 +SiO 2 ) / (Li 2 O+Na 2 O+K 2 O+Cs 2 0)] is 1.00 or more.

[0012] (3) P 2O 5 、B 2 O 3 、SiO 2 、Al 2 O 3 、Li 2 O、Na 2 O、K 2 O and Cs 2 O with respect to the total content of TiO 2 、Nb 2 O 5 、WO 3 、Bi 2 O 3 and Ta 2 O 5 The mass ratio of the total content of [(TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 +Ta 2 O 5 ) / (P 2 O 5 +B 2 O 3 +SiO 2 +Al 2 O 3 +Li 2 O+Na 2 O+K 2 O+Cs 2 O)] is 0.50 or more, the optical glass according to (1) or (2).

[0013] (4) The average linear thermal expansion coefficient α at 100 - 300 °C is 100×10 -7 ~200×10 -7 °C -1 The optical glass according to any one of (1) to (3).

[0014] (5) The temperature coefficient dn / dT of the relative refractive index at the wavelength of the He-Ne laser (633 nm) is -0.1×10 -6 ~ -13.0×10 -6 °C -1 in the range of 20 - 40 °C, the optical glass according to any one of claims 1 to 4.

[0015] An optical element made of the optical glass according to any one of (1) to (5) above.

Advantages of the Invention

[0016] According to the present invention, there can be provided an optical glass having a desired optical constant, a low temperature coefficient (dn / dT) of relative refractive index due to temperature change, and a large average linear thermal expansion coefficient, and an optical element made of the optical glass.

Embodiments for Carrying Out the Invention

[0017] In the present invention and this specification, the glass composition of the optical glass is expressed on an oxide basis unless otherwise specified. Here, the “glass composition on an oxide basis” refers to the glass composition obtained by converting all the glass raw materials into oxides existing in the optical glass when melted, and the notation of each glass component follows the convention, such as SiO 2 , TiO 2 and so on. The content and total content of the glass components are on a mass basis unless otherwise specified, and “%” means “mass %”.

[0018] The content of the glass component can be quantified by known methods, for example, methods such as inductively coupled plasma atomic emission spectrometry (ICP-AES) and inductively coupled plasma mass spectrometry (ICP-MS). Also, in this specification and the present invention, that the content of a constituent component is 0% means that this constituent component is substantially not contained, and it is allowed that the component is contained at an inevitable impurity level.

[0019] In this specification, both the thermal stability and devitrification resistance of the glass refer to the difficulty of crystal precipitation in the glass. In particular, the thermal stability refers to the difficulty of crystal precipitation when the molten glass solidifies, and the devitrification resistance refers to the difficulty of crystal precipitation when the solidified glass is reheated, such as during reheat pressing.

[0020] Also, in this specification, the refractive index refers to the refractive index nd at the d-line of helium (wavelength 587.56 nm) unless otherwise specified.

[0021] The Abbe number νd is used as a value representing the properties related to dispersion and is expressed by the following formula. Here, nF is the refractive index at the F line (wavelength 486.13 nm) of blue hydrogen, and nC is the refractive index at the C line (656.27 nm) of red hydrogen. νd=(nd - 1) / nF - nC ···(1)

[0022] The optical glass according to this embodiment will be described in detail. The optical glass of this embodiment has a refractive index nd of 1.63 to 1.80, an Abbe number νd of 22 to 34, Nb 2 O 5 has a content of 25 to 55 mass%, WO 3 has a content of less than 30 mass%, TiO 2 , Nb 2 O 5 WO 3 Bi 2 O 3 and Ta 2 O 5 The total content of [TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 +Ta 2 O 5 is 36 to 60 mass%, P 2 O 5 B 2 O 3 SiO 2 Al 2 O 3 Li 2 O, Na 2 O, K 2 O and Cs 2 O with respect to the total content of TiO 2 Nb 2 O 5 WO 3 Bi 2 O 3 and Ta2 O 5 The mass ratio of the total content of [(TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 +Ta 2 O 5 ) / (P 2 O 5 +B 2 O 3 +SiO 2 +Al 2 O 3 +Li 2 O+Na 2 O+K 2 O+Cs 2 O)] is 1.10 or less, P 2 O 5 and B 2 O 3 The mass ratio of the content of TiO 2 to the total content of P 2 / (P 2 O 5 +B 2 O 3 )] is 0.50 or less, Satisfies the following (A) or (B). (A) The content of P 2 O 5 is 20 to 36% by mass, Li 2 O, Na 2 O, K 2 O and Cs 2 The mass ratio of P 2 O 5 to the total content of B 2 O 3 and SiO 2 [(P 2 O 5 +B 2 O 3 +SiO 2 ) / (Li 2 O+Na 2 O+K 2 O+Cs 2 O)] is 1.50 or less, P 2 O5 The mass ratio of B 2 O 3 to the content of [B 2 O 3 / P 2 O 5 is 0.05 to 0.39, and the total content of MgO, CaO, SrO and BaO [MgO + CaO + SrO + BaO] is 8.0 mass% or less. (B) P 2 O 5 The content of is 25 to 38 mass%, and Al 2 O 3 The content of is less than 5 mass%, and Li 2 O, Na 2 O, K 2 O and Cs 2 The mass ratio of P 2 O 5 , B 2 O 3 and SiO 2 to the total content of [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (Li 2 O + Na 2 O + K 2 O + Cs 2 O)] is 1.80 or less, and the total content of MgO, CaO, SrO and BaO [MgO + CaO + SrO + BaO] is 7.0 mass% or less, and TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 and Ta 2 O 5 The mass ratio of TiO 2 to the total content of TiO 2 / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta2 O 5 )] is 0.25 or more.

[0023] Hereinafter, unless otherwise specified, the optical glass according to the present embodiment means the optical glass according to the present embodiment that satisfies the above (A) and the optical glass according to the present embodiment that satisfies the above (B).

[0024] In the optical glass according to the present embodiment, the refractive index nd is 1.63 to 1.80. The lower limit of the refractive index nd may be 1.65, 1.67, or 1.69, and the upper limit of the refractive index nd may be 1.79, 1.78, or 1.77.

[0025] The refractive index nd can be set to a desired value by appropriately adjusting the content of each glass component. Components having the effect of relatively increasing the refractive index nd (high refractive index increasing components) are Nb 2 O 5 , TiO 2 , WO 3 , Bi 2 O 3 , Ta 2 O 5 , ZrO 2 , La 2 O 3 etc. On the other hand, components having the effect of relatively lowering the refractive index nd (low refractive index decreasing components) are P 2 O 5 , SiO 2 , B 2 O 3 , Li 2 O, Na 2 O, K 2 O etc. Therefore, for example, P 2 O 5 , B 2 O 3 , SiO 2 , Al 2 O 3 , Li 2 O, Na 2 O, K 2 O and Cs 2 O with respect to the total content of TiO 2 , Nb 2 O 5 , WO3 , Bi 2 O 3 and Ta 2 O 5 The mass ratio of the total content of [(TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 +Ta 2 O 5 ) / (P 2 O 5 +B 2 O 3 +SiO 2 +Al 2 O 3 +Li 2 O + Na 2 O + K 2 O + Cs 2 O)] can be increased to raise the refractive index nd, and the refractive index nd can be decreased by decreasing the mass ratio.

[0026] In the optical glass according to this embodiment, the Abbe number νd is 22 to 34. The lower limit of the Abbe number νd may be 22.5, 23, or 23.5, and the upper limit of the Abbe number νd may be 32, 30, or 28.

[0027] The Abbe number νd can be set to a desired value by appropriately adjusting the content of each glass component. Components that relatively lower the Abbe number νd, i.e., high-dispersion components, are Nb 2 O 5 , TiO 2 , WO 3 , Bi 2 O 3 , Ta 2 O 5 , ZrO 2 , etc. On the other hand, components that relatively increase the Abbe number νd, i.e., low-dispersion components, are P 2 O 5 , SiO 2 , B 2 O 3 , Li 2 O, Na 2 O, K 2 O, La 2O 3 include BaO, CaO, SrO, etc.

[0028] In the optical glass according to this embodiment, Nb 2 O 5 content is 25 - 55%. The lower limit of the Nb 2 O 5 content is preferably 27%, more preferably 29%, 31%, 33 in that order. Also, the upper limit of the Nb 2 O 5 content is preferably 53%, more preferably 51%, 49%, 47 in that order.

[0029] Nb 2 O 5 is a component that contributes to increasing the refractive index and dispersion. Therefore, by setting the content of Nb 2 O 5 within the above range, an optical glass having desired optical constants can be obtained. On the other hand, if the content of Nb 2 O 5 is too much, the coloring of the glass may be enhanced.

[0030] In the optical glass according to this embodiment, the content of WO 3 is less than 30%. The upper limit of the WO 3 content is preferably 20%, more preferably 15%, 10%, 5 in that order. The content of WO 3 is preferably less, and its lower limit is preferably 0%. The content of WO 3 may be 0%.

[0031] By setting the content of WO 3 within the above range, the transmittance can be increased, and the increase in the specific gravity of the glass can be suppressed. Also, the temperature coefficient of the relative refractive index (dn / dT) can be lowered.

[0032] In the optical glass according to this embodiment, TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O3 and Ta 2 O 5 The total content of [TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 is 36 - 60%. The lower limit of the total content is preferably 38%, more preferably 40%, 41%, 42 in that order. Also, the upper limit of the total content is preferably 58%, more preferably 56%, 54%, 52 in that order.

[0033] TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 and Ta 2 O 5 are components that contribute to the high dispersion of the glass. Therefore, by setting the total content [TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 within the above range, an optical glass having desired optical constants can be obtained. Also, the thermal stability of the glass can be improved. On the other hand, if the total content is too high, there is a possibility that an optical glass having desired optical constants cannot be obtained, and the thermal stability of the glass may decrease and the coloring of the glass may intensify.

[0034] In the optical glass according to this embodiment, P 2 O 5 , B 2 O 3 , SiO 2 , Al 2 O 3 , Li 2 O, Na 2 O, K 2 O and Cs 2 O with respect to the total content of TiO 2 , Nb2 O 5 、WO 3 、Bi 2 O 3 and Ta 2 O 5 The mass ratio of the total content of [(TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 +Ta 2 O 5 ) / (P 2 O 5 +B 2 O 3 +SiO 2 +Al 2 O 3 +Li 2 O+Na 2 O+K 2 O+Cs 2 O)] is 1.10 or less. The upper limit of the mass ratio is preferably 1.07, more preferably 1.04, 1.02, and 1.00 in that order. Also, the lower limit of the mass ratio is more preferably 0.50, and further preferably 0.55, 0.60, and 0.65 in that order.

[0035] The mass ratio [(TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 +Ta 2 O 5 ) / (P 2 O 5 +B 2 O 3 +SiO 2 +Al 2 O 3 +Li 2 O+Na 2 O+K 2 O+Cs 2 O)] is within the above range, an optical glass having desired optical constants can be obtained.

[0036] In the optical glass according to this embodiment, P 2 O 5 and B2 O 3 The mass ratio of the content of TiO 2 to the total content of 2 / (P 2 O 5 +B 2 O 3 )] is 0.50 or less.

[0037] The mass ratio [TiO 2 / (P 2 O 5 +B 2 O 3 )] within the above range enables the obtainment of an optical glass having desired optical constants and high thermal stability.

[0038] The optical glass according to this embodiment satisfies (A) or (B) as described above. First, (A) will be described in detail.

[0039] The optical glass according to this embodiment is (A) The content of P 2 O 5 is 20 to 36% by mass, and Li 2 O, Na 2 O, K 2 O, and Cs 2 The mass ratio of the content of P 2 O 5 , B 2 O 3 and SiO 2 to the total content of [(P 2 O 5 +B 2 O 3 +SiO 2 ) / (Li 2 O + Na 2 O + K 2 O + Cs 2 O)] is 1.50 or less, and P 2 O 5 The mass ratio of the content of B 2 O 3 to the content of P 2 O 3 / P 2 O 5is 0.05 to 0.39, and the total content of MgO, CaO, SrO and BaO [MgO + CaO + SrO + BaO] is 8.0 mass% or less, can satisfy the requirements with.

[0040] In the optical glass according to this embodiment that satisfies the above (A), P 2 O 5 content is 20 to 36%. P 2 O 5 The lower limit of the content is preferably 21%, more preferably 22%, 23%, 24 in that order. Also, P 2 O 5 The upper limit of the content is preferably 35%, more preferably 34%, 33%, 32 in that order.

[0041] P 2 O 5 is a network-forming component of the glass and is an essential component for containing a large amount of highly dispersed components in the glass. P 2 O 5 By setting the content of to the above range, an optical glass having high thermal stability and desired optical constants can be obtained.

[0042] In the optical glass according to this embodiment that satisfies the above (A), Li 2 O, Na 2 O, K 2 O and Cs 2 The mass ratio of the total content of O to P 2 O 5 , B 2 O 3 and SiO 2 The total content of [(P 2 O 5 +B 2 O 3 +SiO 2 ) / (Li 2 O+Na 2 O+K 2 O+Cs 2(O) is 1.50 or less. The upper limit of the mass ratio is preferably 1.47, more preferably 1.44, 1.42, and 1.40 in that order. The lower limit of the mass ratio is preferably 1.00, more preferably 1.05, 1.08, and 1.10 in that order.

[0043] Mass ratio [(P 2 O 5 +B 2 O 3 +SiO 2 ) / (Li 2 O+Na 2 O+K 2 O+Cs 2 O)] within the above range, an optical glass with high thermal stability, a low temperature coefficient of relative refractive index (dn / dT), and a large average linear thermal expansion coefficient can be obtained.

[0044] In the optical glass according to this embodiment that satisfies the above (A), the mass ratio [B 2 O 5 content with respect to the P 2 O 3 content [B 2 O 3 / P 2 O 5 is 0.05 to 0.39. The lower limit of the mass ratio is preferably 0.06, more preferably 0.07, 0.08, and 0.09 in that order. The upper limit of the mass ratio is more preferably 0.36, more preferably 0.33, 0.31, and 0.29 in that order.

[0045] Mass ratio [B 2 O 3 / P 2 O 5 within the above range, an optical glass with a low temperature coefficient of relative refractive index (dn / dT), a large average linear thermal expansion coefficient, high devitrification resistance, and a low liquidus temperature LT can be obtained.

[0046] In the optical glass according to the present embodiment satisfying the above (A), the total content of MgO, CaO, SrO, and BaO [MgO + CaO + SrO + BaO] is 8.0% or less. The upper limit of the total content is preferably 6%, more preferably 5%, 4%, and 3% in that order. The lower limit of the total content is preferably 0%.

[0047] By setting the total content [MgO + CaO + SrO + BaO] within the above range, high dispersion can be promoted.

[0048] Also, in the optical glass according to the present embodiment satisfying the above (A), P 2 O 5 and B 2 O 3 The mass ratio [TiO 2 / (P 2 O 2 + B 5 O 2 + B 3 )] of the content of TiO

[0049] The mass ratio [TiO 2 / (P 2 O 5 + B 2 O 3 )] is 0.50 or less. The upper limit of the mass ratio is preferably 0.47, more preferably 0.44, 0.42, and 0.40 in that order. The lower limit of the mass ratio is more preferably 0.00, more preferably 0.03, 0.06, 0.08, and 0.10 in that order. By setting the mass ratio [TiO

[0050] Regarding the content and ratio of the glass components in the optical glass according to the present embodiment satisfying the above (A), the following are non-limiting examples.

[0051] In the optical glass according to the present embodiment satisfying the above (A), the upper limit of the content of B 2 O 3 is preferably 10%, more preferably 8%, 7%, and 6% in that order. Also, B2 O 3 The lower limit of the content of O is preferably 1%, more preferably 1.5%, 1.8%, and 2.0% in this order.

[0052] B 2 O 3 BO is a glass network-forming component and has the function of improving the thermal stability of the glass. On the other hand, B 2 O 3 When the content of BO is large, the devitrification resistance tends to decrease. Therefore, the content of B 2 O 3 is preferably within the above range.

[0053] In the optical glass according to this embodiment that satisfies the above (A), the content of Al 2 O 3 is preferably 3% or less, more preferably 2% or less, and 1% or less in this order. The content of Al 2 O 3 may be 0%.

[0054] Al 2 O 3 is a glass component that has the function of improving the chemical durability and weather resistance of the glass and can be considered as a network-forming component. On the other hand, when the content of Al 2 O 3 increases, the devitrification resistance of the glass decreases. Also, problems such as an increase in the glass transition temperature Tg and a decrease in thermal stability are likely to occur. From the viewpoint of avoiding such problems, the upper limit of the content of Al 2 O 3 is preferably within the above range.

[0055] In the optical glass according to this embodiment that satisfies the above (A), for the total content of TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 and Ta 2 O 5 the mass ratio of the content of TiO 2 to [TiO 2 / (TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 +Ta 2 O 5 )] The lower limit is preferably 0, and more preferably 0.02, 0.04, 0.06 in that order. Also, the upper limit of the mass ratio is preferably 0.50, and more preferably 0.45, 0.40, 0.35 in that order.

[0056] TiO 2 Among the components for increasing the refractive index, it is a component having a particularly large effect on increasing the refractive index. Therefore, from the viewpoint of obtaining desired optical constants, the mass ratio [TiO 2 / (TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 +Ta 2 O 5 )] is preferably within the above range.

[0057] In the optical glass according to this embodiment that satisfies the above (A), the lower limit of the content of TiO 2 is preferably 0%, and more preferably 1%, 2%, 3%, 4% in that order. The content of TiO 2 may be 0%. Also, the upper limit of the content of TiO 2 is preferably 15%, and more preferably 13%, 11%, 10% in that order.

[0058] TiO 2 greatly contributes to high dispersion. On the other hand, TiO 2 tends to relatively increase the coloring of the glass and may deteriorate the meltability. Therefore, the content of TiO 2 is preferably within the above range.

[0059] In the optical glass according to this embodiment that satisfies the above (A), TiO 2 , Nb 2 O 5 , WO3 and Bi 2 O 3 The lower limit of the total content of [TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 is preferably 36%, more preferably 38%, 40%, 41%, 42 in that order. Also, the upper limit of the total content of [TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 is preferably 58%, more preferably 56%, 54%, 52 in that order.

[0060] TiO 2 , Nb 2 O 5 , WO 3 and Bi 2 O 3 contribute to the high dispersion of the glass and also have the function of improving the thermal stability of the glass by containing an appropriate amount. On the other hand, it is also a component that increases the coloring of the glass. Therefore, the total content of [TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 is preferably within the above range.

[0061] In the optical glass according to this embodiment that satisfies the above (A), the lower limit of the content of Na 2 O is preferably 6%, more preferably 8%, 9%, 10 in that order. Also, the upper limit of the content of Na 2 O is preferably 30%, more preferably 28%, 26%, 25 in that order.

[0062] Na 2 O is a component that contributes to the low specific gravity of the glass, improves the meltability of the glass, and also has the function of increasing the average linear thermal expansion coefficient. On the other hand, Na 2When the content of O increases, the devitrification resistance decreases. Therefore, the content of Na 2 O is preferably within the above range.

[0063] In the optical glass according to this embodiment that satisfies the above (A), Li 2 O, Na 2 O and K 2 The upper limit of the total content of O [Li 2 O + Na 2 O + K 2 O] is preferably 35%, more preferably 33%, 31%, 30 in that order. Also, the lower limit of the total content is preferably 10%, more preferably 14%, 17%, 18 in that order.

[0064] Li 2 O, Na 2 O and K 2 O all have the function of improving the thermal stability of the glass. However, when the content of these increases, there is a risk that the chemical durability and weather resistance will decrease. Therefore, the total content of Li 2 O, Na 2 O and K 2 O [Li 2 O + Na 2 O + K 2 O] is preferably within the above range.

[0065] Next, (B) will be described in detail.

[0066] The optical glass according to this embodiment is (B) The content of P 2 O 5 is 25 to 38% by mass, The content of Al 2 O 3 is less than 5% by mass, Li 2 O, Na 2 O, K 2 O and Cs 2 The ratio of P 2 O 5 , B 2 O 3 and SiO to the total content of O2 The mass ratio of the total content [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (Li 2 O + Na 2 O + K 2 O + Cs 2 O)] is 1.80 or less, The total content of MgO, CaO, SrO, and BaO [MgO + CaO + SrO + BaO] is 7.0 mass% or less, TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 and Ta 2 O 5 The mass ratio of the content of TiO 2 to the total content of TiO 2 / (TiO 2 + Nb 2 O 5 + WO 3 + Bi 2 O 3 + Ta 2 O 5 )] is 0.25 or more, can satisfy the requirements with

[0067] In the optical glass according to this embodiment that satisfies the above (B), P 2 O 5 The content is 25 to 38%. P 2 O 5 The lower limit of the content of P 2 O 5 is preferably 26%, more preferably 27%, 28%, 29%, 30% in that order. Also, P

[0068] P 2 O 5 is a network-forming component of the glass and is an essential component for containing a large amount of highly dispersed components in the glass. P 2 O 5By setting the content within the above range, an optical glass with high thermal stability and having desired optical constants can be obtained.

[0069] In the optical glass according to this embodiment that satisfies the above (B), Al 2 O 3 content is less than 5%. The content of Al 2 O 3 is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less in that order. The content of Al 2 O 3 may be 0%.

[0070] Al 2 O 3 is a glass component that has the function of improving the chemical durability and weather resistance of the glass and can be considered as a network-forming component. On the other hand, when the content of Al 2 O 3 increases, the devitrification resistance of the glass decreases. Also, problems such as an increase in the glass transition temperature Tg and a decrease in thermal stability are likely to occur. From the viewpoint of avoiding such problems, the upper limit of the content of Al 2 O 3 is preferably within the above range.

[0071] In the optical glass according to this embodiment that satisfies the above (B), the mass ratio of the total content of P 2 O, Na 2 O, K 2 O and Cs 2 O to the total content of P 2 O 5 , B 2 O 3 and SiO 2 is [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (Li 2 O + Na 2 O + K 2 O + Cs 2The mass ratio [(P

[0072] O)] is 1.80 or less. The upper limit of the mass ratio is preferably 1.78, more preferably 1.76, and even more preferably 1.74 in that order. Also, the lower limit of the mass ratio is preferably 1.00, more preferably 1.05, 1.08, and 1.10 in that order. 2 O 5 +B 2 O 3 +SiO 2 ) / (Li 2 O+Na 2 O+K 2 O+Cs 2 O)] within the above range results in an optical glass having high thermal stability, a low temperature coefficient of relative refractive index (dn / dT), and a large average linear thermal expansion coefficient.

[0073] In the optical glass according to this embodiment that satisfies the above (B), the total content of MgO, CaO, SrO, and BaO [MgO + CaO + SrO + BaO] is 7.0% or less. The upper limit of the total content is preferably 6%, more preferably 5%, 4%, and 3% in that order. Also, the lower limit of the total content is preferably 0%.

[0074] Setting the total content [MgO + CaO + SrO + BaO] within the above range can promote high dispersion.

[0075] In the optical glass according to this embodiment that satisfies the above (B), the mass ratio of the content of TiO 2 , Nb 2 O 5 , WO 3 , Bi 2 O 3 and Ta 2 O 5 to the total content of TiO 2 is [TiO 2 / (TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 +Ta 2 O 5)] is 0.25 or more. The lower limit of the mass ratio is preferably 0.26, and more preferably 0.27, 0.28, 0.29 in this order. Also, the upper limit of the mass ratio is preferably 0.50, and more preferably 0.45, 0.40, 0.35 in this order.

[0076] TiO 2 Among the high refractive index increasing components, it is a component having a particularly large effect of increasing the refractive index. Therefore, from the viewpoint of obtaining a desired optical constant, the mass ratio [TiO 2 / (TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 +Ta 2 O 5 )] is preferably within the above range.

[0077] Also, in the optical glass according to this embodiment that satisfies the above (B), P 2 O 5 and B 2 O 3 The mass ratio [TiO 2 / (P 2 / (P 2 O 5 +B 2 O 3 )] is 0.50 or less. The upper limit of the mass ratio is preferably 0.47, and more preferably 0.46, 0.45 in this order. Also, the lower limit of the mass ratio is preferably 0.00, and more preferably 0.20, 0.25, 0.30, 0.35 in this order.

[0078] By setting the mass ratio [TiO 2 / (P 2 O 5 +B 2 O 3 )] within the above range, an optical glass having a desired optical constant and high thermal stability can be obtained.

[0079] Regarding the content and ratio of the glass components in the optical glass according to this embodiment that satisfies the above (B), non-limiting examples are shown below.

[0080] In the optical glass according to this embodiment that satisfies the above (B), P 2 O 5 For the content of 2 O 3 The mass ratio of the content of 2 O 3 / P 2 O 5 The lower limit is preferably 0. The mass ratio may be 0. Also, the upper limit of the mass ratio is more preferably 0.36, and further preferably 0.33, 0.31, and 0.29 in that order.

[0081] Mass ratio [B 2 O 3 / P 2 O 5 By setting the mass ratio within the above range, an optical glass with a low temperature coefficient of relative refractive index (dn / dT), a large average linear thermal expansion coefficient, high devitrification resistance, and a low liquidus temperature LT can be obtained.

[0082] In the optical glass according to this embodiment that satisfies the above (B), B 2 O 3 The upper limit of the content is preferably 10%, and further preferably 8%, 7%, and 6% in that order. Also, B 2 O 3 The lower limit of the content is preferably 0%. B 2 O 3 The content may be 0%.

[0083] B 2 O 3 is a network-forming component of the glass and has the function of improving the thermal stability of the glass. On the other hand, when the content of B 2 O 3 is large, the devitrification resistance tends to decrease. Therefore, the content of B 2 O 3 is preferably within the above range.

[0084] In the optical glass according to this embodiment that satisfies the above (B), TiO 2The lower limit of the content is preferably 0%, more preferably 1%, 2%, 3%, 4%, 6%, 8%, 10%, 12% in this order. TiO 2 The content may be 0%. Also, TiO 2 The upper limit of the content is preferably 15%.

[0085] TiO 2 greatly contributes to high dispersion. On the other hand, TiO 2 tends to relatively increase the coloring of the glass and may also deteriorate the meltability. Therefore, the content of TiO 2 is preferably within the above range.

[0086] In the optical glass according to this embodiment that satisfies the above (B), TiO 2 , Nb 2 O 5 , WO 3 and Bi 2 O 3 The lower limit of the total content [TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 is preferably 36%, more preferably 38%, 40%, 41%, 42% in this order. Also, the upper limit of the total content [TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 is preferably 58%, more preferably 56%, 54%, 52%, 50%, 48%, 46% in this order.

[0087] TiO 2 , Nb 2 O 5 , WO 3 and Bi 2 O 3 contribute to high dispersion of the glass and also have the function of improving the thermal stability of the glass by containing an appropriate amount. On the other hand, they are also components that increase the coloring of the glass. Therefore, the total content [TiO 2 +Nb2 O 5 +WO 3 +Bi 2 O 3 is preferably within the above range.

[0088] In the optical glass according to this embodiment that satisfies the above (B), Na 2 The lower limit of the content of O is preferably 6%, and more preferably 8%, 9%, 10% in this order. Also, Na 2 The upper limit of the content of O is preferably 30%, and more preferably 28%, 26%, 25%, 22%, 20%, 18%, 17% in this order.

[0089] Na 2 O is a component that contributes to reducing the specific gravity of the glass, improves the meltability of the glass, and has the function of increasing the average linear thermal expansion coefficient. On the other hand, when the content of Na 2 O increases, the devitrification resistance decreases. Therefore, the content of Na 2 O is preferably within the above range.

[0090] In the optical glass according to this embodiment that satisfies the above (B), Li 2 O, Na 2 O and K 2 The upper limit of the total content of O [Li 2 O + Na 2 O + K 2 O] is preferably 35%, and more preferably 33%, 31%, 30%, 28%, 27%, 26%, 25% in this order. Also, the lower limit of the total content is preferably 10%, and more preferably 14%, 17%, 18%, 20% in this order.

[0091] Li 2 O, Na 2 O and K 2 O all have the function of improving the thermal stability of the glass. However, when the content of these increases, there is a risk of deterioration in chemical durability and weather resistance. Therefore, Li 2 O, Na 2 O and K 2 The total content of O [Li2 O + Na 2 O + K 2 It is preferable that O] is within the above range.

[0092] In the optical glass according to this embodiment that satisfies the above (B), Nb 2 O 5 The content of is 25 to 55%. Nb 2 O 5 The lower limit of the content of is preferably 27%, more preferably 29%. Also, Nb 2 O 5 The upper limit of the content of is preferably 53%, more preferably 51%, 49%, 47%, 40%, 35%, 33% in that order.

[0093] Nb 2 O 5 is a component that contributes to increasing the refractive index and dispersion. Therefore, by setting the content of Nb 2 O 5 within the above range, an optical glass having desired optical constants can be obtained. On the other hand, if the content of Nb 2 O 5 is too much, the coloring of the glass may be enhanced.

[0094] Next, the characteristics of the optical glass according to this embodiment will be described.

[0095] In the optical glass according to this embodiment, the lower limit of the average linear thermal expansion coefficient α at 100 to 300 °C is preferably 100×10 -7 °C -1 and further 105×10 -7 °C -1 、110×10 -7 °C -1 、115×10 -7 °C -1 、120×10 -7 °C -1 in that order are more preferable. Also, the upper limit of the average linear thermal expansion coefficient α is more preferably 200×10 -7 °C -1 and further 190×10 -7 °C -1 、180×10-7 °C -1 、170×10 -7 °C -1 、160×10 -7 °C -1 are preferred in this order.

[0096] By setting the average linear expansion coefficient α in the range of 100 to 300 °C within the above range, it is possible to suppress the change in the refractive index accompanying the thermal expansion of the glass, that is, the increase in the temperature coefficient dn / dT of the relative refractive index.

[0097] The average linear expansion coefficient α is measured based on the provisions of JOGIS08 - 2003. However, the sample is a round bar with a length of 20 mm ± 0.5 mm and a diameter of 5 mm ± 0.5 mm, and it is heated at a constant rate of 4 °C per minute while applying a load of 98 mN to the sample, and the temperature and the elongation of the sample are measured. In this specification, the average linear expansion coefficient α is expressed in the unit of [°C -1 , but even when using the unit of [K -1 , the numerical value of the average linear expansion coefficient α is the same.

[0098] In the optical glass according to this embodiment, the temperature coefficient dn / dT of the relative refractive index at the wavelength (633 nm) of the He - Ne laser is, in the range of 20 to 40 °C, preferably - 1.0×10 -6 ~ - 10.0×10 -6 °C -1 and further preferably - 1.5×10 -6 ~ - 9.0×10 -6 °C -1 、 - 2.0×10 -6 ~ - 8.0×10 -6 °C -1 、 - 2.5×10 -6 ~ - 7.0×10 -6 °C -1 、 - 3.0×10 -6 ~ - 6.5×10 -6 °C -1 are preferred in this order.

[0099] By setting dn / dT within the above range and combining it with an optical element with a positive dn / dT, even in an environment where the temperature of the optical element fluctuates greatly, the variation in refractive index is reduced, so that desired optical characteristics can be exhibited with high precision over a wider temperature range.

[0100] The temperature coefficient dn / dT of the relative refractive index is measured based on the interference method of JOGIS18-2008. In this specification, the temperature coefficient dn / dT is expressed in the unit of [°C -1 , but even when using [K -1 as the unit, the numerical value of the temperature coefficient dn / dT is the same.

[0101] (Glass component) Regarding the content and ratio of glass components other than the above in the optical glass according to this embodiment, non-limiting examples are shown below.

[0102] In the optical glass according to this embodiment, the upper limit of the content of SiO 2 is preferably 5%, more preferably 3%, 2%, and 1% in this order. The content of SiO 2 may be 0%.

[0103] Note that a melting tool made of fused silica such as a fused silica crucible may be used for melting the glass. In this case, since a small amount of SiO 2 dissolves from the melting tool into the glass melt, the produced glass contains a small amount of SiO 2 even if the glass raw material does not contain SiO 2 . The amount of SiO 2 mixed into the glass from the fused silica melting tool depends on the melting conditions, but is, for example, about 0.5 to 1% by mass based on the total content of all glass components. The content ratio of glass components other than SiO 2 remains constant, and the amount of SiO 2 increases by about 0.5 to 1% by mass. Note that the above amount increases or decreases depending on the melting conditions. Since the optical characteristics such as refractive index and Abbe number change depending on the content of SiO 2 , the content of SiO 2Fine-tune the content of glass components other than those mentioned above to obtain an optical glass with desired optical properties.

[0104] SiO 2 is a glass network-forming component, which has the function of improving the thermal stability, chemical durability, and weather resistance of the glass, increasing the viscosity of the molten glass, and making it easier to shape the molten glass. On the other hand, SiO 2 When the content is high, the devitrification resistance of the glass tends to decrease. Therefore, the upper limit of the content of SiO 2 is preferably within the above range.

[0105] In this embodiment, the upper limit of the content of Bi 2 O 3 is preferably 15%, more preferably 10%, 7%, 5%, and 3% in that order. Also, the lower limit of the content of Bi 2 O 3 is preferably 0%.

[0106] Bi 2 O 3 has the function of improving the thermal stability of the glass by containing an appropriate amount. On the other hand, when the content of Bi 2 O 3 is increased, the coloring of the glass increases. Therefore, the content of Bi 2 O 3 is preferably within the above range.

[0107] In the optical glass according to this embodiment, the upper limit of the content of Ta 2 O 5 is preferably 10%, more preferably 7%, 5%, and 3% in that order. Also, the lower limit of the content of Ta 2 O 5 is preferably 0%. The content of Ta 2 O 5 may also be 0%.

[0108] Ta 2 O 5 is a glass component that has the function of improving the thermal stability and devitrification resistance of the glass. On the other hand, Ta 2 O5 increases the refractive index and makes the glass have a high dispersion. Also, Ta 2 O 5 When the content of increases, the thermal stability of the glass decreases, and when melting the glass, it is likely to produce unmelted glass raw materials. Therefore, the content of Ta 2 O 5 is preferably within the above range. Furthermore, Ta 2 O 5 is a component that is extremely expensive compared to other glass components. When the content of Ta 2 O 5 increases, the production cost of the glass increases. Furthermore, since Ta 2 O 5 has a larger molecular weight compared to other glass components, it increases the specific gravity of the glass, and as a result, increases the weight of the optical element.

[0109] In the optical glass according to this embodiment, the upper limit of the content of Li 2 O is preferably 5%, and more preferably 3%, 2%, 1% in this order. The lower limit of the content of Li 2 O is preferably 0%. The content of Li 2 O may also be 0%.

[0110] Li 2 O is a component that contributes to reducing the specific gravity of the glass, improves the meltability of the glass, and also has the function of increasing the average linear thermal expansion coefficient. On the other hand, when the content of Li 2 O increases, the devitrification resistance decreases. Therefore, the content of Li 2 O is preferably within the above range.

[0111] In the optical glass according to this embodiment, the lower limit of the content of K 2 O is preferably 1%, and more preferably 2%, 3%, 4% in this order. Also, the upper limit of the content of K 2 O is preferably 13%, and more preferably 12%, 11%, 10% in this order.

[0112] K 2O is a component that contributes to reducing the specific gravity of the glass and has the function of improving the thermal stability of the glass. It also has the function of increasing the average linear thermal expansion coefficient. On the other hand, K 2 When the content of K 2 O increases, the thermal stability decreases, and veins are likely to occur during vitrification. Therefore, the content of K

[0113] In the optical glass according to this embodiment, Cs 2 The upper limit of the content of O is preferably 5%, more preferably 3%, 2%, and 1% in that order. Also, Cs 2 The lower limit of the content of O is preferably 0%. The content of Cs 2 O may be 0%.

[0114] Cs 2 O has the function of improving the meltability of the glass, but when the content increases, the thermal stability and refractive index nd of the glass decrease, and the volatilization of the glass components during melting increases, making it impossible to obtain the desired glass. Therefore, the content of Cs 2 O is preferably within the above range.

[0115] In the optical glass according to this embodiment, the content of MgO is preferably 5% or less, more preferably 3% or less, and 1% or less in that order. Also, the lower limit of the content of MgO is preferably 0%. The content of MgO may be 0%.

[0116] In the optical glass according to this embodiment, the content of CaO is preferably 5% or less, more preferably 3% or less, and 1% or less in that order. Also, the lower limit of the content of CaO is preferably 0%. The content of CaO may be 0%.

[0117] In the optical glass according to this embodiment, the content of SrO is preferably 6% or less, more preferably 5% or less, 3% or less, and 1% or less in that order. Also, the lower limit of the content of SrO is preferably 0%.

[0118] In the optical glass according to this embodiment, the content of BaO is preferably 8% or less, more preferably 5% or less, still more preferably 3% or less, and even more preferably 1% or less in this order. Further, the lower limit of the content of BaO is preferably 0%.

[0119] MgO, CaO, SrO, and BaO are all glass components that function to improve the thermal stability and devitrification resistance of the glass. However, when the content of these glass components increases, the high dispersibility is impaired, and the thermal stability and devitrification resistance of the glass decrease. Therefore, the content of each of these glass components is preferably within the above range.

[0120] In the optical glass according to this embodiment, the upper limit of the content of ZnO is preferably 10%, more preferably 6%, still more preferably 4%, and even more preferably 3% in this order. It is preferable that the ZnO content is small, and the lower limit is preferably 0%. The content of ZnO may be 0%.

[0121] ZnO is a glass component that functions to improve the thermal stability of the glass. However, if the content of ZnO is too high, the specific gravity of the glass increases. Also, the temperature coefficient (dn / dT) of the relative refractive index becomes high. Therefore, the content of ZnO is preferably within the above range.

[0122] In the optical glass according to this embodiment, ZrO 2 The content of is preferably 5% or less, more preferably 3% or less, and still more preferably 1% or less in this order. Further, the lower limit of the content of ZrO 2 is preferably 0%.

[0123] ZrO 2 is a glass component that functions to improve the thermal stability and devitrification resistance of the glass. However, if the content of ZrO 2 is too high, the thermal stability tends to decrease. Therefore, the content of ZrO 2 is preferably within the above range.

[0124] In the optical glass according to this embodiment, Sc 2O 3 The upper limit of the content is preferably 2%. Also, Sc 2 O 3 The lower limit of the content is preferably 0%.

[0125] In the optical glass according to this embodiment, HfO 2 The upper limit of the content is preferably 2%. Also, HfO 2 The lower limit of the content is preferably 0%.

[0126] Sc 2 O 3 and HfO 2 both have the function of increasing the refractive index nd and are expensive components. Therefore, the content of each of Sc 2 O 3 and HfO 2 is preferably within the above range.

[0127] In the optical glass according to this embodiment, Lu 2 O 3 The upper limit of the content is preferably 2%. Also, Lu 2 O 3 The lower limit of the content is preferably 0%.

[0128] Lu 2 O 3 has the function of increasing the refractive index nd. Also, since the molecular weight is large, it is also a glass component that increases the specific gravity of the glass. Therefore, the content of Lu 2 O 3 is preferably within the above range.

[0129] In the optical glass according to this embodiment, GeO 2 The upper limit of the content is preferably 2%. Also, GeO 2 The lower limit of the content is preferably 0%.

[0130] GeO 2has the function of increasing the refractive index nd and is a particularly expensive component among commonly used glass components. Therefore, from the perspective of reducing the manufacturing cost of glass, GeO 2 content is preferably within the above range.

[0131] In the optical glass according to this embodiment, La 2 O 3 The upper limit of the content is preferably 2%. Also, La 2 O 3 The lower limit of the content is preferably 0%. La 2 O 3 The content may be 0%.

[0132] La 2 O 3 When the content of La 2 O 3 increases, the thermal stability and devitrification resistance of the glass decrease, and the glass is likely to devitrify during manufacturing. Therefore, from the perspective of suppressing the decrease in thermal stability and devitrification resistance, the content of La

[0133] In the optical glass according to this embodiment, Gd 2 O 3 The upper limit of the content is preferably 2%. Also, Gd 2 O 3 The lower limit of the content is preferably 0%.

[0134] Gd 2 O 3 When the content of Gd 2 O 3 exceeds a certain level, the thermal stability and devitrification resistance of the glass decrease, and the glass is likely to devitrify during manufacturing. Also, when the content of Gd 2 O 3 exceeds a certain level, the specific gravity of the glass increases, which is not preferable. Therefore, from the perspective of maintaining good thermal stability and devitrification resistance of the glass while suppressing the increase in specific gravity, the content of Gd

[0135] In the optical glass according to this embodiment, Y 2 O 3 The upper limit of the content is preferably 2%. Also, Y 2 O 3 The lower limit of the content is preferably 0%. The content of Y 2 O 3 may be 0%.

[0136] Y 2 O 3 If the content of Y 2 O 3 becomes too large, the thermal stability and devitrification resistance of the glass will decrease. Therefore, from the viewpoint of suppressing the decrease in thermal stability and devitrification resistance, the content of Y

[0137] In the optical glass according to this embodiment, Yb 2 O 3 The upper limit of the content is preferably 2%. Also, Yb 2 O 3 The lower limit of the content is preferably 0%.

[0138] Yb 2 O 3 has a larger molecular weight compared to La 2 O 3 , Gd 2 O 3 , Y 2 O 3 and thus increases the specific gravity of the glass. When the specific gravity of the glass increases, the mass of the optical element increases. For example, when a lens with a large mass is incorporated into an autofocus type imaging lens, the power required for driving the lens during autofocus increases, and the battery consumption becomes severe. Therefore, it is desirable to reduce the content of Yb 2 O 3 to suppress the increase in the specific gravity of the glass.

[0139] Also, if the content of Yb 2 O 3 is too large, the thermal stability and devitrification resistance of the glass will decrease. From the viewpoint of preventing the decrease in the thermal stability of the glass and suppressing the increase in specific gravity, Yb 2O 3 The content of 3 is preferably within the above range.

[0140] The optical glass according to this embodiment that satisfies the above (A) mainly consists of the above glass components, that is, P as an essential component 2 O 5 、Nb 2 O 5 、B 2 O 3 、WO as an optional component 3 、SiO 2 、Al 2 O 3 、TiO 2 、Bi 2 O 3 、Ta 2 O 5 、Li 2 O、Na 2 O、K 2 O、Cs 2 O、MgO、CaO、SrO、BaO、ZnO、ZrO 2 、Sc 2 O 3 、HfO 2 、Lu 2 O 3 、GeO 2 、La 2 O 3 、Gd 2 O 3 、Y 2 O 3 、and Yb 2 O 3 It is preferably composed of the above, and the total content of the above glass components is preferably 95% or more, more preferably 98% or more, even more preferably 99% or more, and still more preferably 99.5% or more.

[0141] Also, the optical glass according to this embodiment that satisfies the above (B) mainly consists of the above glass components, that is, P as an essential component 2 O 5 、Nb 2 O 5 、B as an optional component 2 O 3 、WO 3 、SiO 2 、Al 2 O3 , TiO 2 , Bi 2 O 3 , Ta 2 O 5 , Li 2 O, Na 2 , K 2 , Cs 2 O, MgO, CaO, SrO, BaO, ZnO, ZrO 2 , Sc 2 O 3 , HfO 2 , Lu 2 O 3 , GeO 2 , La 2 O 3 , Gd 2 O 3 , Y 2 O 3 , and Yb 2 O 3 It is preferably composed of the above glass components, and the total content of the above glass components is preferably 95% or more, more preferably 98% or more, even more preferably 99% or more, and still more preferably 99.5% or more.

[0142] In the optical glass according to this embodiment, the upper limit of the content of TeO 2 is preferably 2%. Also, the lower limit of the content of TeO 2 is preferably 0%.

[0143] Since TeO 2 has toxicity, it is preferable to reduce the content of TeO 2 . Therefore, the content of TeO 2 is preferably within the above range.

[0144] In addition, the optical glass according to this embodiment is preferably basically composed of the above glass components, but it is also possible to contain other components within a range that does not prevent the effects of the present invention. Also, in the present invention, the inclusion of inevitable impurities is not excluded.

[0145] <Other component compositions> Pb, As, Cd, Tl, Be, and Se all have toxicity. Therefore, it is preferable that the optical glass according to this embodiment does not contain these elements as glass components.

[0146] U, Th, and Ra are all radioactive elements. Therefore, it is preferable that the optical glass according to this embodiment does not contain these elements as glass components.

[0147] V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, and Er can increase the coloring of the glass and become a source of fluorescence. Therefore, it is preferable that the optical glass according to this embodiment does not contain these elements as glass components.

[0148] Sb (Sb 2 O 3 ), Ce (CeO 2 ) are optionally addable elements that function as fining agents. Among these, Sb (Sb 2 O 3 ) is a fining agent with a large fining effect. However, Sb (Sb 2 O 3 ) has strong oxidizing properties. When the addition amount of Sb (Sb 2 O 3 ) is increased, the coloring of the glass increases due to light absorption by Sb ions, which is not preferable. Also, when melting the glass, if there is Sb in the melt, the elution of platinum constituting the glass melting crucible into the melt is promoted, and the platinum concentration in the glass increases. In the glass, when platinum exists as ions, the coloring of the glass increases due to light absorption. Also, when platinum exists as a solid in the glass, it becomes a light scattering source and deteriorates the quality of the glass. Ce (CeO 2 ) has a smaller fining effect compared to Sb (Sb 2 O 3 ). Ce (CeO 2 ) enhances the coloring of the glass when added in a large amount. Therefore, when adding a fining agent, it is preferable to add Sb (Sb 2 O 3 ) while paying attention to the addition amount.

[0149] Sb 2 O 3 The content of is expressed as an external division. That is, Sb 2 O 3 and CeO 2 When the total content of all glass components other than is 100% by mass, the content of Sb 2 O 3 is preferably less than 1% by mass, more preferably less than 0.1% by mass. Further, it is preferably less than 0.05% by mass, less than 0.03% by mass, and less than 0.02% by mass in this order. The content of Sb 2 O 3 may be 0% by mass.

[0150] CeO 2 The content of is also expressed as an external division. That is, CeO 2 , Sb 2 O 3 When the total content of all glass components other than is 100% by mass, the content of CeO 2 is preferably less than 2% by mass, more preferably less than 1% by mass, still more preferably less than 0.5% by mass, and even more preferably in the range of less than 0.1% by mass. The content of CeO 2 may be 0% by mass. By setting the content of CeO 2 within the above range, the clarity of the glass can be improved.

[0151] (Glass properties) <Glass transition temperature Tg> The glass transition temperature Tg of the optical glass according to this embodiment is preferably 570 °C or lower, and more preferably 560 °C or lower, 550 °C or lower, 540 °C or lower, and 530 °C or lower in this order.

[0152] By satisfying the upper limit of the glass transition temperature Tg within the above range, an increase in the molding temperature and annealing temperature of the glass can be suppressed, and thermal damage to the press molding equipment and annealing equipment can be reduced. Also, by satisfying the lower limit of the glass transition temperature Tg within the above range, it becomes easier to maintain good thermal stability of the glass while maintaining the desired Abbe number and refractive index.

[0153] <Specific gravity of glass> In the optical glass according to this embodiment, the specific gravity is preferably 3.60 or less, more preferably 3.50 or less, and even more preferably 3.40 or less in this order. If the specific gravity of the glass can be reduced, the weight of the lens can be decreased. As a result, the power consumption of the autofocus drive of the camera lens equipped with the lens can be reduced.

[0154] <Light transmittance of glass> The light transmittance of the optical glass according to this embodiment can be evaluated by the coloring degree λ5. For a glass sample with a thickness of 10.0 mm ± 0.1 mm, the spectral transmittance is measured in the wavelength range of 200 to 700 nm, and the wavelength at which the external transmittance becomes 5% is defined as λ5.

[0155] λ5 of the optical glass according to this embodiment is preferably 400 nm or less, more preferably 380 nm or less, and even more preferably 370 nm or less.

[0156] By using an optical glass with a shorter wavelength of λ5, an optical element enabling suitable color reproduction can be provided.

[0157] (Manufacture of optical glass) The optical glass according to the embodiment of the present invention may be prepared by formulating glass raw materials so as to have the above-mentioned predetermined composition, and then producing the formulated glass raw materials according to a known glass manufacturing method. For example, a plurality of types of compounds are formulated and sufficiently mixed to form a batch raw material. The batch raw material is placed in a quartz crucible or a platinum crucible and roughly melted (rough melt). The melt obtained by the rough melting is rapidly cooled and pulverized to produce cullets. Further, the cullets are placed in a platinum crucible, heated, and remelted (remelt) to form a molten glass. After further clarification and homogenization, the molten glass is formed and slowly cooled to obtain an optical glass. Known methods may be applied to the forming and slow cooling of the molten glass.

[0158] In addition, as long as the desired glass components can be introduced into the glass so as to have the desired contents, the compounds used when preparing the batch raw materials are not particularly limited. Examples of such compounds include oxides, carbonates, nitrates, hydroxides, fluorides, and the like.

[0159] (Manufacture of optical elements, etc.) To produce an optical element using the optical glass according to an embodiment of the present invention, a known method may be applied. For example, a glass raw material is melted to obtain molten glass, and this molten glass is poured into a mold and formed into a plate shape to produce a glass material made of the optical glass according to the present invention. The obtained glass material is appropriately cut, ground, and polished to produce a cut piece having a size and shape suitable for press molding. The cut piece is heated and softened, and press molded (reheat press) by a known method to produce an optical element blank approximating the shape of the optical element. The optical element blank is annealed and ground and polished by a known method to produce an optical element.

[0160] An antireflection film, a total reflection film, etc. may be coated on the optical functional surface of the produced optical element according to the purpose of use.

[0161] Examples of the optical element include various lenses such as spherical lenses, prisms, diffraction gratings, and the like.

[0162] The present invention will be described below with reference to examples, but the present invention is not limited only to the following examples.

[0163] (Examples) [Preparation of glass samples] Compound raw materials corresponding to each component, that is, raw materials such as phosphates, carbonates, oxides, etc., were weighed so as to obtain glass having the compositions of Sample Nos. 1 to 52 shown in Tables 1 to 6, and sufficiently mixed to obtain a prepared raw material. The prepared raw material was put into a platinum crucible, heated to 900 to 1350 °C in an air atmosphere and melted, and homogenized and clarified by stirring to obtain molten glass. The molten glass was poured into a molding die and molded, and slowly cooled to obtain a block-shaped glass sample. Incidentally, the compounding raw materials may be put into a quartz glass crucible, melted, then transferred to a platinum crucible and further heated and melted, homogenized and clarified by stirring, and the obtained molten glass may be cast into a mold for shaping and slowly cooled.

[0164] [Evaluation of Glass Samples] Regarding the obtained glass samples, the glass composition, specific gravity, refractive index nd, Abbe number νd, λ5, glass transition temperature Tg, temperature coefficient of relative refractive index dn / dT, and average linear expansion coefficient α were measured by the methods shown below. The results are shown in Tables 1, 2, and 4.

[0165] [(1) Glass Composition] Regarding the obtained glass samples, the content of each glass component was measured by inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0166] [(2) Specific Gravity] It was measured based on the standard JOGIS-05 of the Japan Optical Glass Industry Association.

[0167] [(3) Refractive Index nd and Abbe Number νd] It was measured based on the standard JOGIS-01 of the Japan Optical Glass Industry Association.

[0168] [(4) λ5] The glass samples were processed to have a thickness of 10 mm and parallel and optically polished planes, and the spectral transmittance in the wavelength range from 280 nm to 700 nm was measured. The intensity of the light incident perpendicularly to one of the optically polished planes was defined as intensity A, and the intensity of the light exiting from the other plane was defined as intensity B, and the spectral transmittance B / A was calculated. The wavelength at which the spectral transmittance becomes 5% was defined as λ5. Note that the spectral transmittance includes the reflection loss of light on the sample surface.

[0169] [(5) Glass Transition Temperature Tg] The glass transition temperature Tg was measured using a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH JAPAN at a heating rate of 10 °C / min.

[0170] 〔6〕Measurement of the temperature coefficient dn / dT of the relative refractive index For the obtained glass samples, measurements were carried out based on the interference method of JOGIS18-2008. A He-Ne laser with a wavelength of 633 nm was used as the light source, and continuous measurements were performed in the temperature range of -70 to 150 °C. Among the measurement results, the dn / dT values in the range of 20 °C to 40 °C are shown in Tables 1, 2, and 4.

[0171] 〔7〕Measurement of the average linear expansion coefficient α The average linear expansion coefficient α at 100 to 300 °C was measured based on the provisions of JOGIS08-2003. However, the sample was a round bar with a length of 20 mm ± 0.5 mm and a diameter of 5 mm ± 0.5 mm. With a load of 98 mN applied to the sample, it was heated at a constant rate of 4 °C per minute so as to rise, and the temperature and the elongation of the sample were measured.

[0172]

Table 1

[0173]

Table 2

[0174]

Table 3

[0175]

Table 4

[0176]

Table 5

[0177]

Table 6

[0178] (Example 2) The glass sample obtained in Example 1 was cut and ground to produce cut pieces. The cut pieces were press-molded by a reheat press to produce optical element blanks. The optical element blanks were precisely annealed, and the refractive index was precisely adjusted to the required refractive index. Then, by grinding and polishing by a known method, various lenses such as biconvex lenses, biconcave lenses, plano-convex lenses, plano-concave lenses, concave meniscus lenses, and convex meniscus lenses were obtained.

[0179] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

[0180] For example, with respect to the glass composition exemplified above, by performing the composition adjustment described in the specification, an optical glass according to one aspect of the present invention can be produced. Also, of course, it is possible to arbitrarily combine two or more of the matters exemplified or described as preferred ranges in the specification.

Claims

1. Optical glass having a refractive index nd of 1.63 to 1.80, an Abbe number νd of 22 to 34, Nb 2 O 5 The content of which is 25 to 55% by mass, WO 3 content is less than 30% by mass, TiO 2 The content thereof is 14.24 mass% or less, Li 2 The content of O is 0.89 mass% or less, TiO 2 , Nb 2 O 5 , W.O. 3 , Bi 2 O 3 and Ta 2 O 5 The total content [TiO 2 +Nb 2 O 5 +W.O. 3 +Bi 2 O 3 +Ta 2 O 5 ] is 36 to 60 mass %, P 2 O 5 、B 2 O 3 、SiO 2 、Al 2 O 3 、Li 2 O、Na 2 O、K 2 O and Cs 2 The mass ratio of TiO 2 、Nb 2 O 5 、WO 3 、Bi 2 O 3 and Ta 2 O 5 to the total content of P 2 、Nb 2 O 5 、WO 3 、Bi 2 O 3 、Ta 2 O 5 ) / (P 2 O 5 、B 2 O 3 、SiO 2 、Al 2 O 3 、Li 2 O、Na 2 O、K 2 O、Cs 2 O)] is 1.10 or less, P 2 O 5 and B 2 O 3 The mass ratio [TiO 2 content / (P 2 O 2 + B 5 O 2 content)] of the TiO content with respect to the total content of 3 is 0.50 or less, and satisfying the following (A). (A) P 2 O 5 The content of is 20 to 36% by mass, Li 2 O, Na 2 O, K 2 O and Cs 2 The mass ratio of P to the total content of 2 O 5 , B 2 O 3 and SiO 2 [(P 2 O 5 + B 2 O 3 + SiO 2 ) / (Li 2 O + Na 2 O + K 2 O + Cs 2 O)] is 1.50 or less, P 2 O 5 The mass ratio of the content of B 2 O 3 to the content of 2 O 3 / P 2 O 5 is 0.05 to 0.39, and The total content of MgO, CaO, SrO, and BaO [MgO + CaO + SrO + BaO] is 8.0 mass% or less.

2. Li 2 O, Na 2 O, K 2 O and Cs 2 The mass ratio of P 2 O 5 , B 2 O 3 and SiO 2 to the total content of [ (P 2 O 5 + B 2 O 3 + SiO 2 ) / ( Li 2 O + Na 2 O + K 2 O + Cs 2 O ) ] is 1.00 or more. The optical glass according to claim 1.

3. P 2 O 5 、B 2 O 3 、SiO 2 、Al 2 O 3 、Li 2 O、Na 2 O、K 2 O and Cs 2 The mass ratio of TiO 2 、Nb 2 O 5 、WO 3 、Bi 2 O 3 and Ta 2 O 5 to the total content of [TiO 2 +Nb 2 O 5 +WO 3 +Bi 2 O 3 +Ta 2 O 5 ) / (P 2 O 5 +B 2 O 3 +SiO 2 +Al 2 O 3 +Li 2 O+Na 2 O+K 2 O+Cs 2 O)] is 0.50 or more, the optical glass according to claim 1 or 2.

4. The average linear thermal expansion coefficient α at 100 to 300 °C is 100×10 -7 to 200×10 -7 °C -1 The optical glass according to any one of claims 1 to 3.

5. The temperature coefficient dn / dT of the relative refractive index at the wavelength of the He-Ne laser (633 nm) is -0.1×10 -6 to -13.0×10 -6 °C -1 The optical glass according to any one of claims 1 to 4.

6. An optical element made of the optical glass according to any one of Claims 1 to 5.

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