JP4671647B2 - Optical glass with small photoelastic constant - Google Patents

Description

  The present invention is an optical glass having a small photoelastic constant (β) suitable for a polarizing optical system member, a polarization control element substrate, and the like, and various physical properties (appropriate refractive index and Abbe number, etc.) useful for optical glass applications. About.

  In recent years, an optical system using polarized light, that is, a polarizing optical system has been used in various fields including a liquid crystal projector. For example, a spatial light modulator that spatially modulates polarized light and a polarizing beam splitter that separates S-polarized light and P-polarized light are used in liquid crystal projectors. It is desired to control with high accuracy.

  Among optical components in a polarizing optical system, when a material having optical anisotropy is used for a member such as a prism or a substrate of a light polarization control element that requires polarization property maintenance such as a polarization beam splitter or a spatial light modulation element The phase difference (optical path difference) between the transmitted principal ray and the extraordinary ray orthogonal to this changes compared to before transmission through the material, and the polarization characteristics cannot be maintained. It is necessary to use an isotropic material.

  Even when conventional optical glass that has been sufficiently annealed and strain-removed and has optical isotropy is used in an optical component that requires the polarization characteristics to be maintained in a polarizing optical system, mechanical and thermal stresses are not generated. When added to such glass, if the photoelastic constant of the glass is large, the optical anisotropy due to the photoelastic effect, that is, birefringence is exhibited, and as a result, it is difficult to obtain desired polarization characteristics. There is. The mechanical stress is generated, for example, by bonding a material having a coefficient of thermal expansion different from that of glass to glass, and the thermal stress is, for example, absorbing heat generated by peripheral devices or transmitted light energy. This is caused by the heat generated by the glass itself. When these stresses are applied to the glass, the magnitude of birefringence exhibited by the glass can be indicated by an optical path difference. When the optical path difference is δ (nm), the glass thickness is d (cm), and the stress is F (Pa), the following formula (1) is established, and the larger the optical path difference is, the larger the birefringence is.

    δ = β · d · F (1)

  The proportionality constant (β) in the above formula (1) is called a photoelastic constant, and its value varies depending on the type of glass. As shown in the above formula (1), when the stress (F) applied to the glass and the glass thickness (d) are the same, the glass having a smaller absolute value of the photoelastic constant (β) has an optical path difference (δ), that is, birefringence. The nature is small.

  The discussion on the contribution of the photoelastic constant of the member used in the polarization optical system is as described in, for example, Japanese Patent Application Laid-Open Nos. 7-306314, 8-234179, and 9-127461. . As a more specific numerical analysis, for example, a member satisfying the following relational expression as disclosed in JP 2000-171770 A is desired for the polarization optical system. The right side of this equation indicates the amount of birefringence due to thermal stress.

5.00 × 10 ² ≧ K · α · E · ∫ (1-T) dλ / ρ / Cp (2)

Here, K is a photoelastic constant (nm / mm · mm ² / N), α is a linear thermal expansion coefficient (10 ⁻⁶ / K), E is a Young's modulus (10 ³ N / mm ² ), and λ is a light used. , T is the internal transmittance of the member at wavelength λ, ρ is the specific gravity of the member (g / cm ³ ), Cp is the specific heat of the member (J / g · k), The integration range is the main absorption wavelength band (420 [nm] to 500 [nm]) of the member.
As shown in Equation (2), it is clear that the amount of birefringence due to thermal stress can be reduced as the absolute value of the photoelastic constant approaches zero.

In addition, the photoelastic constant has wavelength dependence and is not constant over the entire visible region (400 nm to 700 nm). Therefore, even if the photoelastic constant at a wavelength of 546 nm, which is a representative value in the visible region of the photoelastic constant, is small, if the wavelength dependency is large, the polarization characteristics vary depending on the wavelength. For example, in a glass containing a high amount of PbO as disclosed in JP-A-11-133528, there is a wavelength dependency in which the photoelastic constant is decreased as the wavelength becomes shorter, and the change amount Δβ of the photoelastic constant from 400 nm to 700 nm. Is about 0.8 × 10 ⁻⁵ nm / cm / Pa. When such a glass is used as, for example, a polarizing beam splitter in a liquid crystal projector, even when β = 0.0 × 10 ⁻⁵ nm / cm / Pa in green (G) light (wavelength near 550 nm), blue (B ) For light (wavelength near 430 nm) and red (R) light (wavelength near 640 nm), the absolute value of β is approximately 0.4 × 10 ⁻⁵ nm / cm / Pa, and in particular, the B light has a large refractive index. Therefore, there is a problem that the optical path difference due to birefringence increases.

  In addition to the problem of birefringence described above, in applications where the temperature of the optical member varies greatly depending on the usage environment (for example, heat generated by prisms, lenses, peripheral electrical circuits, parts, etc. exposed to high-intensity irradiation light) It is desirable that the optical path length change accompanying the temperature change is small. In particular, high internal transmittance is required to suppress an increase in the temperature of the optical member due to light absorption of high intensity irradiation light.

Examples of the glass having a small photoelastic constant useful as a polarizing optical system member as described above include a B ₂ O ₃ —Al ₂ O ₃ —PbO system such as JP-A-9-48631 and JP-A-11-335135. Phosphoric glasses containing BaO and / or PbO, such as JP-A-11-199269, JP-A-2000-34132, JP-A-2002-128540, and JP-A-2002-338294. Non-containing phosphate glass, fluorophosphate glass such as JP-A-9-48633 is disclosed.

Journal of the Society of Glass Technology (1957) 353T-362T “The Effect of the Polarization of the Constituent Ions on the Photoelastic Birefringence of the Glass” by Megumi Tashiro et al. It has long been known that the effect of reducing the photoelastic constant is large. There are a wide variety of glasses with small photoelastic constants using this effect, but they contain a large amount of Pb compounds (for example, PbO, PbF ₂ etc.) that have a high environmental impact in order to significantly reduce the photoelastic constants. Since there is a concern about the adverse effect on the environment, it is not practically preferable.

In phosphate-based glasses, the photoelastic constant of P ₂ O ₅ —BaO-based glasses is relatively small, especially in the Journal of the American Ceramic Society Vo.68 (1985) P389-P391 “Photoelastic effects in Phosphate Glasses”. by Matushita et.al. However, in order to reduce the photoelastic constant (β) in the visible light region to 0.3 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ⁻¹ or less by using only the photoelastic constant lowering effect of the BaO component, Due to the limitation of the vitrification range in the P ₂ O ₅ —BaO system, a special production method such as a super-quenching method must be used, and not only the productivity is very bad, but it is also difficult to form a desired optical member. is there. Japanese Patent Application Laid-Open No. 2002-338294 discloses a method for producing a glass having a high BaO content ratio in the P ₂ O ₅ —BaO system, and has a very small photoelasticity of 0.15 × 10 ⁻¹² (1 / Pa). Examples of glasses with constants are described. However, in order to obtain these glasses, it is necessary to adopt a production method inferior in productivity, in which a plurality of gases (wet air and chlorine gas) are blown into the molten glass. In a phosphate glass not containing a Pb compound, not only the BaO component but also the La ₂ O ₃ component has the effect of reducing the photoelastic constant, as disclosed in JP-A-11-199269 and JP-A-2000-34132. Although it is disclosed in publications and the like, only the photoelastic constant lowering effect of the BaO / La ₂ O ₃ component has a photoelastic constant (β) of 0.3 × It is clear from these examples that it is difficult to produce a glass of 10 ⁻⁵ nm · cm ⁻¹ · Pa ⁻¹ or less.

Japanese Patent Application No. 2003-110394 discloses that a phosphate glass having a photoelastic constant of 0.3 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ⁻¹ or less can be produced. . However, in phosphate glass containing a large amount of PbO or BaO, platinum group ions such as platinum, palladium, and rhodium from the platinum crucible are eluted when the glass is melted in a platinum crucible essential for glass production, and the glass is colored. Is often a problem. According to Journal of the American Ceramic Society Vo.39 (1956) P173-P180 “The Colors of Platinum, Palladium, and Rhodium in simple Glasses” by GERindone et.al It has been found that it occurs remarkably at 400-500 nm. The presence of such absorbed ions means that the light absorbed when light having a wavelength of 400 to 500 nm passes through the optical member is converted into heat, which causes undesirable heat generation and increases the thermal stress in the member. . Alternatively, when used for optical components that transmit the entire visible light region (lenses, prisms, etc.), blue light of 400 to 500 nm is selectively absorbed, so the transmitted light is yellowish. End up. Although the required level differs depending on the application, it is desired that the glass has a high internal transmittance because it is possible to realize better characteristics with less unnecessary light absorption. That is, in the production of a phosphate glass containing a large amount of PbO or BaO, it is necessary to pay great attention to the elution of platinum group ions.

  On the other hand, commercially available fluorophosphate glass (S-FPL51, S-FPL52, S-FPL53: trade name of OHARA INC.), JP-A-9-48633, USP5969691, DE19631171A1, JP-A-11-60267, etc. As disclosed, in fluorophosphate glasses, the bonds in the glass are generally not covalent bonds such as Si-O but strong ionic bonds, so the deformation of the electronic structure due to stress is reduced. The photoelastic constant is relatively small. In addition, since the fluorophosphate glass can be melted at a relatively low temperature, it can be obtained from a platinum melting apparatus (a crucible or a glass stirrer) that occurs in a phosphate glass containing a large amount of BaO or the like. There is little elution of platinum group ions, and selective absorption by platinum group ions in the visible light region (especially 400 to 500 nm) is not a problem. Other than the above, although the photoelastic constant is not clearly shown, a fluorophosphate having a refractive index (nd) of around 1.60 to 1.68 and an Abbe number (νd) of around 40 to 65 Examples of the system glass include fluorophosphate glasses, which are characterized by large anomalous dispersion such as JP-A-50-50416, JP-A-57-123842, JP-A-59-18133, and JP-A-2-124740. Known are fluorophosphate glasses having excellent devitrification resistance and meltability, such as Kaihei 6-157068 and JP-A-10-53434.

As shown in JP-A-2-124740, JP-A-6-157068, and JP-A-9-48633, a general fluorophosphate glass has a refractive index (nd) of less than 1.6 or an Abbe number ( Many glasses have νd) of 65 or more. In order to increase the refractive index (nd), JP-A-50-50416, JP-A-57-123842, JP-A-59-18133, and JP-A-11-60267 increase the total amount of fluoride raw materials at most. An example is described in which the content is limited to less than 45% and the refractive index (nd) is greater than 1.6, but in this case, the introduction of fluoride is restricted, and the covalent bondability becomes stronger in the glass. There is a concern that a small photoelastic constant cannot be realized. In JP-A-10-53434, the content of Al (PO ₃ ) ₃ is as high as 21.23 to 26.35 wt%, and the MgF ₂ component is essential, so that the photoelastic constant is expected to be large.

Moreover, as a fluorophosphate glass for a filter which contains a light absorption component having a specific wavelength such as CeO ₂ or CuO, although used for different purposes, JP-A-1-219038, JP-A-3-83835 and JP-A-3-83 83834, JP-A-4-214043, and the like are disclosed. JP 1-219038, JP-A-3-83835, for JP-A _3-83834, many examples containing P 2 _{O 5} more than 20%, there is a high possibility that desired photoelastic constant can not be realized, _{P 2} In an example in which O ₅ is less than 20%, MgF ₂ that contains a relatively large photoelastic constant is contained (Example 1 of JP-A-1-219038), or B ₂ O ₃ that increases the photoelastic constant is contained. A large amount is contained (Examples 2, 4, 10 of JP-A-3-83835, Example 2 of JP-A-3-83834). In the example disclosed in JP-A-4-214043, there is a concern that not only the content of MgF ₂ is large but a desired photoelastic constant cannot be realized, and the refractive index is low.
Japanese Patent Laid-Open No. 2-124740 Japanese Patent Laid-Open No. 50-50416 JP-A-57-123842 JP 59-18133 A JP-A-6-157068 Japanese Patent Laid-Open No. 10-53434 Japanese Patent Laid-Open No. 11-60267 JP-A-7-306314 JP-A-8-234179 JP-A-9-127461 JP 2000-171770 A JP-A-11-133528 JP 9-48631 A JP 11-335135 A JP-A-11-199269 JP 2000-34132 A JP 2002-128540 A JP 2002-338294 A JP-A-9-48633 Japanese Patent Application No. 2003-110394 Specification US Pat. No. 5,969,861 German Patent Publication No. 1963171 Japanese Patent Laid-Open No. 1-219038 Japanese Patent Laid-Open No. 3-83835 JP-A-3-83834 JP-A-4-214043 Journal of The Society of Glass Technology (1957) 353T-362T “The Effect of the Polarization of the Constituent Ions on the Photoelastic Birefringence of the Glass” by Megumi Tashiro Journal of the American Ceramic Society Vo.68 (1985) P389-P391 “Photoelastic effects in Phosphate Glasses” by Matushita et.al Journal of the American Ceramic Society Vo.39 (1956) P173-P180 “The Colors of Platinum, Palladium, and Rhodium in simple Glasses” by GERindone et.al

  The present invention has been made in view of the above problems, and is suitable for a polarizing optical system member and a polarization control element substrate, and has a very small photoelastic constant (β) and various physical properties useful for optical glass applications. An optical glass having both (for example, refractive index (nd) and Abbe number (νd)) is provided. Furthermore, the present invention provides the optical glass containing no Pb compound.

  As a result of intensive studies and studies to achieve the above-mentioned goal, the present inventor realized desired physical properties by realizing a composition containing specific amounts of Ba, F and Nb among the constituent components of the optical glass. The present inventors have found that an optical glass having a can be produced relatively stably, and have reached the present invention. The configuration is shown below.

The first configuration of the present invention has a refractive index (nd) of 1.60 to 1.68 and an Abbe number (νd) of 40 or more and less than 65, and as the atoms constituting the glass,
P 5-10 mol%
Al 1-3 mol%
Ba 8-13 mol%
Gd 1-5 mol%
Nb 0.1-3 mol% and F 15-35 mol%
O 40-52 mol%
It is an optical glass containing each component in the ratio of

The second configuration of the present invention has a refractive index (nd) of 1.60 to 1.68 and an Abbe number (νd) of 40 or more and less than 65, and as the atoms constituting the glass,
P 5-10 mol%
Al 1-3 mol%
Ba 8-13 mol%
Gd 1-5 mol%
Nb 0.1-3 mol%
F 15-35 mol%
O 40-52 mol% and Y 0-2 mol% and / or La 0-2 mol% and / or Yb 0-1 mol% and / or Ta 0-1 mol% and / or Lu 0-1 mol% and / or Ti 0-1 0.5 mol% and / or Zr 0-1.5 mol% and / or W 0-1.5 mol% and / or Bi 0-1.5 mol% and / or Mg 0-2 mol% and / or Ca 0-3 mol% and And / or Sr 0-5 mol% and / or Zn 0-2 mol% and / or Li 0-2 mol% and / or Na 0-2 mol% and / or K 0-2 mol% and / or Cs 0-1 mol% and / or. Tl 0-3 mol% and / or Si 0-2 mol% and / or B 0-2 mol% and / or Sb 0-1 mol%
It is an optical glass containing each component of the ratio.

The third configuration of the present invention is:
Having a refractive index (nd) of 1.60 to 1.68 and an Abbe number (νd) of 40 or more and less than 65;
Metaphosphate compound 18.0-30.0%
_{However, Al (PO 3) 3 10.0} ~ 20.0%
_{Ba (PO 3) 2 3.0 ~} 15.0% and,
Fluoride 43.0-65.0%
_However, BaF 2 41.0 ~ _55.0%,
Gd ₂ O ₃ 8.0 ~ 25.0%
And Nb ₂ O ₅ 0.5-7.0%
It is an optical glass containing each component.

The fourth configuration of the present invention has a refractive index (nd) of 1.60 to 1.68 and an Abbe number (νd) of 40 or more and less than 65, and is expressed in mass%.
Metaphosphate compound 18.0-30.0%,
_{However, Al (PO 3) 3 10.0} ~ 20.0%
Ba (PO ₃ ) ₂ 3.0 to 15.0% and Sr (PO ₃ ) ₂ 0.0 to 10.0% and / or Ca (PO ₃ ) ₂ 0.0 to 10.0% and / or Zn (PO ₃ ) ₂ 0.0-5.0% and / or La (PO ₃ ) ₃ 0.0-5.0%
Containing
Fluoride 43.0-65.0%
However, BaF ₂ 41.0 to 55.0% and SrF ₂ 0.0 to 10.0% and / or CaF ₂ 0.0 to 10.0% and / or MgF ₂ 0.0 to 2.0% and / or Or AlF ₃ 0.0-2.0% and / or GdF ₃ 0.0-15.0% and / or YF ₃ 0.0-7.0% and / or LaF ₃ 0.0-7.0% and / or KHF ₂ 0.0 ~ 3.0%
And
Gd ₂ O ₃ 8.0 ~ 25.0%
Nb ₂ O ₅ 0.5 to 7.0% and Y ₂ O ₃ 0.0 to 10.0% and / or La ₂ O ₃ 0.0 to 10.0% and / or Yb ₂ O ₃ 0.0 to 5.0% and / or Ta ₂ O ₅ 0.0 to 5.0% and / or Lu ₂ O ₃ 0.0 to 5.0% and / or TiO ₂ 0.0 - 7.0% and / Or ZrO ₂ 0.0-5.0% and / or WO ₃ 0.0-7.0% and / or Bi ₂ O ₃ 0.0-5.0% and / or BaO 0.0-8.0 % and / or CaO 0.0 ~ 5.0% and / or SrO 0.0 ~ 10.0% and / or ZnO 0.0 ~ 5.0% and / or Li ₂ O 0.0 ~ 1.0 % and / or Na ₂ O 0.0 ~ 3.0% and / or K ₂ O 0.0 ~ 3.0% and / or Cs ₂ O 0.0 ~ 5. 0% and / or Tl ₂ O 0.0-15.0% and / or SiO ₂ 0.0-3.0% and / or B ₂ O ₃ 0.0-3.0% and / or Sb ₂ O ₃ 0.0-3.0%,
Is an optical glass.

The fifth configuration of the present invention has a refractive index (nd) of 1.60 to 1.68 and an Abbe number (νd) of 40 or more and less than 65, and expressed in mass%.
P ₂ O ₅ 12 to less than 22%,
Al ₂ O ₃ 1-5%
BaO 40-55%
Gd ₂ O ₃ 8-25% and Nb ₂ O ₅ 0.5-8% and Y ₂ O ₃ 0-10% and / or La ₂ O ₃ 0-10% and / or Yb ₂ O ₃ 0-5% and / or Ta ₂ O ₅ 0 ~ _5% and / or Lu ₂ O ₃ 0 ~ 5% and / or TiO ₂ 0 ~ 7% and / or ZrO ₂ 0 ~ 5% and / or WO ₃ 0 ~ 7% and And / or Bi ₂ O ₃₀ to 5% and / or MgO 0 to 1% and / or CaO 0 to 5% and / or SrO 0 to 10% and / or ZnO 0 to 5% and / or Li ₂ O 0 to 1% and / or Na ₂ O 0 to 3% and / or K ₂ O 0 to 3% and / or Cs ₂ O 0 to 5% and / or Tl ₂ O 0 to 15% and / or SiO ₂ 0 to 3 % and / or B ₂ O ₃ 0 ~ _3% and / or S ₂ O ₃ 0 ~ _3%
The total amount of F containing one or two or more of the above oxide-converted compositions and fluoride-substituted part or all of one or more of the above oxides is 8 to 20 weights per 100 parts by weight of the oxide-converted composition. It is an optical glass characterized by being a part.

In the sixth configuration of the present invention, the difference between the photoelastic constant at 644 nm and the photoelastic constant at 436 nm is −0.1 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ^{−1 to} 0.1 × 10 ⁻⁵ nm ·. It is the optical glass of the said structures 1-5 which is cm < ^{-1 >} * Pa < ^-1 >.

In the seventh configuration of the present invention, when the refractive index (nd) is in the range of 1.60 to 1.62, the photoelastic constant at 546 nm is −0.1 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ^−1. When the refractive index (nd) is in the range of 1.62 to 1.68, the photoelastic constant at 546 nm is −0.1.−0.3 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ⁻¹ × a ^{10 -5 nm · cm -1 · Pa} -1 ~0.5 × 10 -5 nm · cm -1 is · Pa ^-1 wherein structure 6 of the optical glass.

The eighth configuration of the present invention has a refractive index (nd) of 1.60 to 1.65, an Abbe number (νd) of less than 50 to 65, and a photoelastic constant at 546 nm of −0.1 × 10. an optical glass as defined in ^{-5 nm · cm -1 · Pa -1} ~0.3 × 10 -5 nm · cm the structure 7 is a ^-1 · Pa ^-1.

  The 9th structure of this invention is the optical glass of the said structures 1-8 which do not contain a lead compound.

  A tenth configuration of the present invention is a polarizing beam splitter for a liquid crystal projector using the optical glass of the above configurations 1 to 9.

According to the present invention, the refractive index nd suitable for a polarizing optical system member or a polarization control element substrate is 1.60 to 1.68, the Abbe number νd is less than 40 to 65, and the photoelastic constant (β) at a wavelength of 546 nm is. −0.1 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ^{−1 to} 0.5 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ⁻¹ , and the wavelength dependence of the photoelastic constant is as described above. An extremely small optical glass was obtained without using a Pb compound, and an optical member having excellent characteristics that could not be obtained in the past could be produced.

The optical glasses having configurations 1 and 2 can realize a refractive index nd = 1.60 to 1.68 which is advantageous for the production of a polarizing film because of optical design which is difficult to realize with conventional fluorophosphate glasses, and is photoelastic. For example, an optical element such as a polarizing beam splitter having a small constant and reduced birefringence due to thermal stress or mechanical stress can be produced. In addition, the optical constants such as the refractive index and the Abbe number that are realized can increase the degree of freedom in optical design and can flexibly respond to diversification of product needs.
P is a glass forming component, and if it is less than 5 mol%, it is difficult to obtain a stable glass, and if it exceeds 10 mol%, a desired photoelastic constant cannot be realized. Preferably, the lower limit is 5 mol%, more preferably 5.5 mol%, most preferably 6 mol%, preferably 10 mol%, more preferably 9.8 mol%, and most preferably 9.5 mol%.
In the glass, P is LiPO ₃ , NaPO ₃ , KPO ₃ , Al (PO ₃ ) ₃ , Ba (PO ₃ ) ₂ , Sr (PO ₃ ) ₂ , Ca (PO ₃ ) ₂ , Mg (PO ₃ ) _2. , Zn (PO ₃ ) ₂ , La (PO ₃ ) ₃ , P ₂ O ₅ , H ₃ PO ₄ , NH ₄ H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ , Li ₃ PO ₄ , K ₃ PO ₄ , Na ₃ PO ₄ · 12H ₂ O, Na ₂ HPO ₄ · 12H ₂ O, Mg ₃ (PO ₄ ) ₂ · 8H ₂ O, CaHPO ₄ · 2H ₂ O, Ba ₃ (PO ₄ ) ₂ , Zn ₃ (PO ₄ ) ₂ · 4H ₂ O, AlPO ₄ , BPO ₄ , KH ₂ PO ₄ , K ₂ HPO ₄ , KPF ₆ , Zn ₂ PO ₇ , BaHPO ₄ , Al (PO ₃ ) ₃ , Ba (PO ₃ ) ₂ , Sr (PO ₃ ) ₂ , Ca (PO ₃ ) ₂ , La (PO ₃ ) ₃ , P ₂ O ₅ , H ₃ PO ₄ , NH ₄ H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ Is preferred.
Al is required to contain at least 1 mol% in order to prevent glass from being dialyzed and to obtain a stable glass, and to increase mechanical strength and durability. However, if it exceeds 3 mol%, the desired photoelasticity is required. Constants and optical constants cannot be realized. Preferably 1 mol%, more preferably 1.3 mol%, most preferably 1.5 mol% is the lower limit, preferably 3 mol%, more preferably 2.9 mol%, most preferably 2.8 mol% is contained as the upper limit. .
In the glass, Al can be contained in the form of Al (PO ₃ ) ₃ , AlPO ₄ , Al ₂ O ₃ , Al (OH) ₃ , AlF ₃ , Na ₃ AlF ₆ , and Al (PO ₃ ) ₃ , It is preferable to use AlPO ₄ , AlF ₃ , Na ₃ AlF ₆ .
Since Ba has a high effect of reducing the photoelastic constant among the glass constituent atoms, it is necessary to contain at least 8 mol%. However, when it exceeds 13 mol%, it becomes difficult to obtain a stable glass. Preferably 8 mol%, more preferably 8.3 mol%, most preferably 8.5 mol% is the lower limit, preferably 13 mol%, more preferably 12.8 mol%, most preferably 12.5 mol% is the upper limit. . In the glass, Ba can be contained in the form of Ba (PO ₃ ) ₂ , Ba ₃ (PO ₄ ) ₂ , BaHPO ₄ , Ba (NO ₃ ) _2, BaCO ₃ , BaF ₂ , BaSiF _6. It is preferable to use PO ₃ ) ₂ , Ba (NO ₃ ) _2, BaCO ₃ , BaF ₂ .
Gd is an essential component for promoting stable glass formation and achieving a high refractive index. If the amount is less than 1 mol%, the glass becomes unstable and the desired refractive index cannot be realized. On the other hand, if it exceeds 5 mol%, melting at a high melting temperature is required, and component volatilization (especially fluorine component) during melting is promoted. Therefore, in order to realize a very small photoelastic constant, the lower limit is preferably 1 mol%, more preferably 1.2 mol%, most preferably 1.3 mol%, preferably 5 mol%, more preferably 4.5 mol%. %, And most preferably 4 mol% is contained as an upper limit.
In the glass, Gd can be contained in the form of any Gd compound, but it is preferable to use Gd ₂ O ₃ or GdF ₃ .
Nb can achieve a high refractive index with a small amount of addition and has an effect of improving chemical durability. Therefore, Nb is an essential component in the present invention, and can be added up to 3 mol%. However, if the amount is less than 0.1 mol%, the above effect is difficult to obtain, and a desired optical constant cannot be realized. Further, when the content is more than 3 mol%, the photoelastic constant is increased, so that the lower limit is preferably 0.1 mol%, more preferably 0.2 mol%, most preferably 0.3 mol%, and more preferably 3 mol%. Preferably, the content is 2.8 mol%, and most preferably 2.5 mol%.
In the glass, Nb can be contained in any form, but it is preferably contained in the form of Nb ₂ O ₅ .
F is an indispensable component for glass formation in a fluorophosphate glass, and is an essential component because it has a high effect of increasing glass meltability and reducing the photoelastic constant. If it is less than 15 mol%, it is difficult to obtain a stable glass and it is difficult to realize a desired photoelastic constant. Further, if it is contained more than 35 mol%, it becomes difficult to realize a desired optical constant. Therefore, the lower limit is preferably 15 mol%, more preferably 17 mol%, most preferably 19 mol%, preferably 35 mol%, more preferably The upper limit is 34 mol%, and most preferably 33 mol%.
In the glass, F is BaF ₂ , SrF ₂ , CaF ₂ , MgF ₂ , AlF ₃ , GdF ₃ , YF ₃ , LaF ₃ , KHF ₂ , BaSiF ₆ , LiF, NaF, KF, ZnF ₂ , KPF ₆ , ZrF _4. , K ₂ SiF ₆ , Na ₃ AlF ₆ , Na ₂ SiF ₆ , BaF ₂ , SrF ₂ , CaF ₂ , MgF ₂ , AlF ₃ , GdF ₃ , YF ₃ , LaF ₃ , KHF ₂ Is preferably used.
O is an essential component for glass formation in a fluorophosphate glass, and is an essential component for realizing a desired optical constant. If it is less than 40 mol%, it is difficult to obtain a stable glass, and it is difficult to realize a desired optical constant. Further, if it is contained in an amount of more than 52 mol%, it becomes difficult to achieve a desired photoelastic constant. Therefore, the lower limit is preferably 40 mol%, more preferably 41 mol%, and most preferably 42 mol%, preferably 52 mol%, more preferably The upper limit is 51 mol%, and most preferably 50 mol%.
The components Y, La, Yb, Ta, Lu, Ti, Zr, W, and Bi can be arbitrarily added because the refractive index and the Abbe number can be adjusted. More specifically, since the Y and La components can be increased in refractive index without increasing the photoelastic constant, preferably 2 mol%, more preferably 1.9 mol%, most preferably 1.8 mol%. Although it can be added as an upper limit, excessive addition deteriorates the devitrification stability of the glass. Yb, Ta, and Lu can effectively increase the refractive index. However, excessive addition destabilizes the glass, so 1.0 mol% is preferable, and 0.9 mol% is most preferable. Preferably 0.8 mol% can be added as an upper limit. Zr has the effect of improving the mechanical strength in accordance with the refractive index adjustment effect of the glass, but in order to add 1.5 mol% or more, since melting at high temperature is required, preferably 1.5 mol%, more The upper limit is preferably 1.45 mol%, and most preferably 1.4 mol%. Ti, W, and Bi are effective in increasing the refractive index and adjusting the Abbe number. However, excessive addition gives color to the glass, so that it is preferably 1.5 mol%, more preferably 1.45 mol%, most preferably. Can be added up to 1.4 mol%.
Each component of Y, La, Yb, Ta, Lu, Ti, Zr, W, and Bi can be contained in any form, but is preferably used in the form of an oxide or fluoride. Mg, Ca, Sr and Zn can be added as necessary because an effect of stabilizing the glass (improving devitrification resistance) can be obtained by adding an appropriate amount. However, if excessive addition, the desired photoelastic constant and refractive index can not be obtained, Ca can be preferably added 3 mol%, more preferably 2.95 mol%, most preferably 2.9 mol% as the upper limit, Sr is preferably added at an upper limit of 5 mol%, more preferably 4.5 mol%, most preferably 4 mol%, and Zn is preferably 2 mol%, more preferably 1.95 mol%, most preferably 1.9 mol%. It can be added as an upper limit. Since Mg has a high effect of increasing the photoelastic constant, it can be added preferably at an upper limit of 2 mol%, more preferably 1 mol%, and most preferably not added at all.
Each component of Mg, Ca, Sr, and Zn can be contained in any form, but is preferably used in the form of oxide, fluoride, carbonate and / or nitrate. Li, Na, K, Cs Each component of Li, Na, and K is preferably 2 mol%, more preferably 1.95 mol%, and most preferably 1.9 mol%, in order to improve glass meltability and defoaming effect. Cs is preferably 1 mol%, more preferably 0.95 mol%, and most preferably 0.9 mol% as an upper limit. Excessive addition is not preferable because the glass becomes unstable and defects such as devitrification easily occur.
Each component of Li, Na, K and Cs can be contained in any form, but is preferably used in the form of oxide, fluoride, carbonate and / or nitrate. Since there is an effect that the refractive index and the Abbe number can be adjusted while improving and reducing the photoelastic constant, it can be added arbitrarily, but if it exceeds 3 mol%, the coloring of the glass becomes remarkable, and preferably 3 mol% or less More preferably, it is 2.7 mol% or less, and most preferably 2.5 mol% or less. Each component of Tl can be contained in any form, but is preferably used in the form of an oxide. Si and B are effective in adjusting the refractive index and improving the mechanical strength, but have a photoelastic constant. In order to significantly increase the amount, the upper limit is preferably 2 mol%, more preferably 1 mol%, and most preferably no addition. Each component of Si and B can be contained in any form, but is preferably used in the form of an oxide and / or any composite salt. Known for clarification and homogenization of the optical glass of the present invention. Sb which is a defoaming component can be optionally added. Moreover, since the refractive index and photoelastic constant can be adjusted in addition to the above effects, the upper limit can be arbitrarily added as 1 mol%. However, excessive addition is preferable because it promotes excessive foaming during melting. Absent.
Sb can be contained in any form, but is preferably used in the form of an oxide.

Next, the glass constituent components described in Configuration 3 will be described.
Al (PO ₃ ) ₃ is a particularly preferable component in the glass of the present invention because it functions as a glass forming component. In order to form stable glass, it is necessary to contain 10% or more, but when it exceeds 20% by mass, a desired photoelastic constant or optical constant cannot be obtained. Accordingly, the lower limit is preferably 10% by mass, more preferably 11% by mass, and most preferably 12% by mass, preferably 20% by mass, more preferably 18% by mass, and most preferably 17% by mass with respect to the total mass of the glass. Is contained as the upper limit.

Ba (PO ₃ ) ₂ is a particularly preferable component in the glass of the present invention because it has an effect of reducing the photoelastic constant of BaO and an effect of increasing the refractive index in addition to the action as a glass forming component. In order to realize the desired characteristics, it is necessary to contain at least 3% by mass or more, but if it exceeds 15% by mass, a desired photoelastic constant cannot be obtained (P ₂ O ₅ is a photoelastic constant). Because of the effect of increasing Accordingly, the lower limit is preferably 3% by mass, more preferably 5% by mass, most preferably 6% by mass, preferably 15% by mass, more preferably 14% by mass, and most preferably 13% by mass with respect to the total mass of the glass. It is contained as an upper limit.

  When the total amount of the metaphosphate compound is less than 18% by mass, it is difficult to obtain a stable glass, and when it exceeds 30% by mass, desired characteristics (particularly, a small photoelastic constant) cannot be realized. Accordingly, the lower limit is preferably 18% by mass, more preferably 19% by mass, and most preferably 20% by mass, preferably 30% by mass, more preferably 29% by mass, and most preferably 28% by mass with respect to the total mass of the glass. Is preferably the upper limit.

BaF ₂ is an essential component in the present invention because it has a high effect of reducing the photoelastic constant and an effect of improving the meltability. If it is less than 41% by mass, a glass having a small photoelastic constant cannot be realized. On the other hand, if it exceeds 55% by mass, not only the instability of the glass becomes remarkable, but also the desired refractive index (nd) = 1.60 to 1.68 cannot be realized. Accordingly, the lower limit is preferably 41% by mass, more preferably 41.5% by mass, and most preferably 41.8% by mass, preferably 55% by mass, more preferably 50% by mass, and most preferably, based on the total mass of the glass. Is contained up to 49% by mass.

  If the total amount of fluoride is less than 43% by mass, the bonds in the glass increase the covalent bond. As a result, the photoelastic constant increases, and if it exceeds 65% by mass, the desired refractive index cannot be realized. In addition, problems such as striae are likely to occur. In order to realize a very small photoelastic constant, the lower limit is preferably 43% by mass, more preferably 43.5% by mass, and most preferably 43.8% by mass, preferably 65% by mass, based on the total mass of the glass. More preferably, it is 64% by mass, and most preferably 63% by mass.

Gd ₂ O ₃ is an essential component for promoting stable glass formation and achieving a high refractive index. If the amount is less than 8% by mass, the glass is significantly destabilized and a desired refractive index cannot be realized. On the other hand, if it exceeds 25 mass%, melting at a high melting temperature is required, and component volatilization (especially fluorine component) during melting is promoted. Therefore, in order to realize a very small photoelastic constant, the lower limit is preferably 8% by mass, more preferably 9% by mass, and most preferably 9.5% by mass, preferably 25% by mass with respect to the total mass of the glass. %, More preferably 20% by mass, most preferably 19% by mass.

Nb ₂ O ₅ is an essential component in the present invention because it can achieve a high refractive index with a small amount of addition and has an effect of improving chemical durability, and 7.0% by mass should be added to the upper limit. Is possible. However, if the amount is less than 0.5% by mass, it is difficult to obtain the above effect, and a desired optical constant cannot be realized. In addition, when it contains more than 7.0 mass%, a photoelastic constant will become large. Accordingly, the lower limit is preferably 0.5% by mass, more preferably 0.8% by mass, and most preferably 1.0% by mass, preferably 7.0% by mass, and more preferably 6.5% by mass with respect to the total mass of the glass. It is contained by mass%, most preferably 6.0 mass% as an upper limit.

  The reason for limiting the glass constituent components in Configuration 4 is as follows. In addition, components overlapping with configuration 3 are as described in configuration 3 above.

Since each component of Sr (PO ₃ ) ₂ , Ca (PO ₃ ) ₂ , Zn (PO ₃ ) ₂ , and La (PO ₃ ) ₃ has an action as a glass forming component, it may be added as necessary. Good. The Sr (PO ₃ ) ₂ component has an effect of reducing the photoelastic constant in addition to the above-described action, and therefore, the upper limit is preferably 10% by mass, more preferably 9% by mass, and most preferably 8% by mass. Ca _{(PO 3) 2} component, because of the effect of improving the stability of the glass, preferably 10 wt%, more preferably 9 mass%, and most preferably a maximum of 8% by weight. Since the Zn (PO ₃ ) ₂ component has the effect of increasing the photoelastic constant, the upper limit is preferably 5% by mass, more preferably 4% by mass, and most preferably 3% by mass. When La (PO ₃ ) ₃ component exceeds 5% by mass, the devitrification property of the glass is deteriorated. Therefore, the upper limit is preferably 5% by mass, more preferably 4% by mass, and most preferably 3.5% by mass. . In addition, the total amount of the metaphosphate compound is the same as in the configuration 3.

SrF ₂ and CaF ₂ are preferably 10% by mass, more preferably 9% by mass, and most preferably 8.5% by mass because the effect of reducing the photoelastic constant and the effect of improving the meltability are obtained in the same manner as BaF _2. % Can be added up to the upper limit. When it exceeds 10 mass%, a desired refractive index cannot be realized. MgF ₂ and AlF ₃ can improve the meltability and increase the mechanical strength of the glass. However, excessive addition significantly increases the photoelastic constant, so that it is preferably 2% by mass, more preferably 1% by mass. % Is the upper limit, most preferably not added at all.

GdF ₃ and LaF ₃ have the effect of increasing the refractive index while maintaining the photoelastic constant. Therefore, GdF ₃ is preferably 15% by mass, more preferably 14% by mass, and most preferably 13.5% by mass. Can be added as Note that addition of 15% by mass or more makes the glass unstable. LaF ₃ is preferably 7 mass%, more preferably 6 wt%, most preferably added to 5 mass% as the upper limit. Excessive addition makes the glass unstable.
YF ₃ has an effect of stabilizing the glass and the refractive index can be adjusted, so that it can be added preferably at an upper limit of 7% by mass, more preferably 6% by mass, and most preferably 5.5% by mass. Excessive addition increases the photoelastic constant.
KHF ₂ can be added with an upper limit of preferably 3% by mass, more preferably 2.5% by mass, and most preferably 2% by mass, since an improvement in glass meltability and a defoaming effect can be obtained. Excessive addition significantly reduces the refractive index, so that the desired refractive index cannot be realized. The total amount of fluoride is as described for Configuration 3.

Each metal oxide component of Y ₂ O ₃ , La ₂ O ₃ , Yb ₂ O ₃ , Ta ₂ O ₅ , Lu ₂ O ₃ , TiO ₂ , ZrO ₂ , WO ₃ , Bi ₂ O ₃ has a refractive index and an Abbe Since the number can be adjusted, it can be arbitrarily added. More specifically, the Y ₂ O ₃ and La ₂ O ₃ components can be increased in refractive index without increasing the photoelastic constant, and therefore are preferably 10.0% by mass, more preferably 8% by mass, Most preferably, the upper limit can be 7% by mass, but excessive addition deteriorates the devitrification stability of the glass. Yb ₂ O ₃ , Ta ₂ O ₅ , Lu ₂ O _3, and Bi ₂ O ₃ can effectively increase the refractive index, but since excessive addition destabilizes the glass, 5.0% by mass, more preferably 4% by mass, and most preferably 3% by mass can be added as the upper limit. ZrO ₂ has the effect of improving the mechanical strength in accordance with the refractive index adjustment effect of the glass, but in order to add 5.0% by mass or more, since melting at high temperature is required, preferably 5.0% by mass. %, More preferably 4.5% by mass, and most preferably 4% by mass. TiO ₂ and WO ₃ are effective in increasing the refractive index and adjusting the Abbe number. However, excessive addition gives color to the glass, and therefore preferably 7.0% by mass, more preferably 6% by mass, most preferably Can be added up to 5 mass%.

BaO has a large effect of reducing the photoelastic constant and, for effective adjustment of the refractive index and Abbe number, in addition to BaF _2, preferably 8 wt% or less, more preferably 7.5 wt% or less, most preferably 7 mass% or less can be arbitrarily added. In addition, when it exceeds 8 mass%, since destabilization of glass will become remarkable, it is not preferable.

  CaO, SrO, and ZnO can be added as necessary because an effect of stabilizing the glass (improving devitrification resistance) can be obtained by adding an appropriate amount. However, since excessive addition of the desired photoelastic constant and refractive index cannot be achieved, CaO and ZnO are preferably 5.0% by mass, more preferably 4.5% by mass, and most preferably 4.0% by mass. % Can be added up to the upper limit, and SrO can preferably be added up to 10.0% by weight, more preferably 9% by weight, and most preferably 8% by weight.

For each component of Li ₂ O, Na ₂ O, K ₂ O, and Cs ₂ O, Li ₂ O is preferably 1.0% by mass, more preferably 0.8%, in order to improve glass meltability and defoaming effect. Na ₂ O and K ₂ O are preferably 3.0% by weight, more preferably 2.5% by weight, most preferably 2.0% by weight, with an upper limit of 8% by weight, most preferably 0.5% by weight. As an upper limit, Cs ₂ O is preferably added in an amount of 5.0% by mass, more preferably 4% by mass, and most preferably 3% by mass. Excessive addition is not preferable because the glass becomes unstable and defects such as devitrification easily occur.

The Tl ₂ O component has an effect of adjusting the refractive index and the Abbe number while improving the glass meltability and reducing the photoelastic constant, so that it can be arbitrarily added. Since it becomes remarkable, it is preferably 15% by mass or less, more preferably 14% by mass or less, and most preferably 13% by mass or less.

SiO ₂ and B ₂ O ₃ are effective in adjusting the refractive index and improving the mechanical strength. However, in order to significantly increase the photoelastic constant, the upper limit is preferably 3.0% by mass, more preferably 2% by mass. Most preferably, no addition.

For clarifying and homogenizing the optical glass of the present invention, Sb ₂ O ₃ which is a known defoaming agent can be optionally added. In addition to the above effects, the refractive index and photoelastic constant can be adjusted, so the upper limit can be arbitrarily added at 3.0% by mass. However, excessive addition promotes excessive foaming during melting. Therefore, it is not preferable.

Configurations 4 and 5 show nearly equivalent glass component ranges. For example, Ba (PO ₃ ) ₂ decomposes into a BaO component and a P ₂ O ₅ component during glass melting at a high temperature. Configuration 4 is a description based on a composite salt or fluoride, and Configuration 5 is a description based on an oxide generated by vitrification reaction.
In composition 5, “oxide equivalent composition” means that the composite salt, fluoride, etc. used as the glass constituent of the present invention are all decomposed and changed into oxides when the glass is melted. It is the composition which described each component contained in glass by making the total weight into 100 mass%.
The reason why the glass constituent components are limited in configuration 5 is as follows. The components overlapping with configurations 1, 2, 3 and 4 are as described above.

For P ₂ O ₅ is a glass forming oxide, is an essential component in the glass of the present invention. In order to form a stable glass, it is necessary to contain 12% by mass or more, but when it is 22% by mass or more, a desired photoelastic constant cannot be obtained. Therefore, it is preferably 12% by mass, more preferably 13% by mass, most preferably 14% by mass as the lower limit, preferably less than 22% by mass, more preferably 20% by mass, and most preferably 19% by mass.

Al ₂ O ₃ is highly effective in promoting stable glass formation in a fluorophosphate glass, and it is necessary to contain 1% by mass or more in order to obtain an effect of improving mechanical strength and chemical durability. However, if it exceeds 5% by mass, a desired photoelastic constant cannot be obtained. Accordingly, it can be contained preferably 1% by mass, more preferably 1.5% by mass, and most preferably 2% by mass, preferably 5% by mass, more preferably 4.5% by mass, most preferably 4% by mass. Can be contained as an upper limit.

  BaO is an essential component because it has a large effect of reducing the photoelastic constant and is effective in adjusting the refractive index and the Abbe number. When it is less than 40% by mass, desired photoelastic constants and optical constants (refractive index, Abbe number) cannot be obtained. If it exceeds 55% by mass, destabilization of the glass, which is undesirable in production, such as out of dialysis, becomes remarkable. Accordingly, the lower limit may preferably be 40% by mass, more preferably 41% by mass, and most preferably 42% by mass, preferably 55% by mass, more preferably 54% by mass, and most preferably 53% by mass.

  The effect of F (fluorine) in the glass is as described above, but the total of F in which one or more oxides are partially or entirely substituted with respect to 100 parts by weight of the oxide equivalent composition. If the amount is less than 8 parts by weight, a stable glass cannot be obtained, and if more than 20 parts by weight is contained, the desired refractive index cannot be realized. Therefore, the lower limit is preferably 8 parts by weight, more preferably 9 parts by weight, and most preferably 10 parts by weight, preferably 20 parts by weight, more preferably 19 parts by weight, and most preferably 18 parts by weight.

MgO (MgF ₂ , Mg (PO ₃ ) ₂ , MgCO ₃ , MgO, etc. are used as the raw material form) has the effect of remarkably increasing the photoelastic constant of the glass. Therefore, it can be added up to 1% by mass as an MgO component.

  According to the configuration 6, since the wavelength dependency is small and the birefringence amount at each wavelength is uniform, it is not necessary to consider the wavelength dependency of the influence due to the birefringence of the product characteristics in the optical design.

  According to Configuration 7, since the amount of birefringence generated by mechanical and thermal stress is small, the designed optical characteristics can be faithfully realized, and an optical member (lens / prism) capable of high-precision polarization control.・ Board etc. can be realized. The wavelength dependence of the photoelastic constant is important for applications in optical members that function over the entire visible range.

  According to the configuration 8, by optimizing the photoelastic constant value and the refractive index further than the configuration 7, the effect shown in the configuration 7 can be obtained, and an optical member (lens and lens) that requires particularly high-precision polarization control is obtained. Prism, substrate, etc.).

  In the glass of the present invention, the Pb compound content is less than 0.1% by mass, preferably not contained at all, with respect to the total mass of the glass.

Examples of the present invention will be described. Tables 1 and 2 (Glass component description according to Configuration 2), Tables 3 and 4 (Glass component description according to Configuration 4) and Tables 5 and 6 (Glass component description according to Configuration 5) The rate (nd) is 1.60 to 1.68, the Abbe number νd is less than 40 to 65, and the photoelastic constant (β) at a wavelength of 546 nm is −0.1 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ^−. preferred embodiments for obtaining the optical glass ^{1 ~0.5 × 10 -5 nm · cm} -1 · Pa -1 indicating the (No.1~18). Table 7 (Configuration 2) shows the composition of comparative examples (No. A to I) of known optical glass and the refractive index (nd), Abbe number (νd), and photoelastic constant (β) of the obtained glass. Table 8 (glass component description according to configuration 4) and Table 9 (glass component description according to configuration 5). In Tables 1 to 3 and Tables 4 to 6, when the example numbers are the same, it means samples having the same composition.

  The photoelastic constant (β) is obtained by measuring the optical path difference generated at the center of the glass by applying a compressive load in a predetermined direction to a disk shape having a diameter of 25 mm and a thickness of 8 mm obtained by polishing the sample face-to-face. Sought by. The ultra-high pressure mercury lamp was used for the 436 nm and 546 nm measurement light sources, and the halogen lamp was used for the 644 nm measurement light source.

  The glasses of Examples 1 to 18 were weighed and mixed at a predetermined ratio using ordinary optical glass materials such as metaphosphate compounds, oxides, carbonates, nitrates, fluorine compounds and hydroxides, and then platinum crucibles. Is melted at a temperature of 900 to 1200 ° C. for 3 to 4 hours according to the degree of difficulty in melting the glass composition, homogenized with stirring, then cooled to an appropriate temperature, and then poured into a mold or the like and gradually cooled. Was obtained. In addition, if necessary, a lid was applied during melting to reduce the volatilization of fluorine.

In each of Examples 1 to 18, the refractive index (nd) is 1.60 to 1.68, the Abbe number (νd) is less than 40 to 65, and the photoelastic constant (β) at a wavelength of 546 nm is −0.1. was in the range of ^{× 10 -5 nm · cm -1 ·} Pa -1 ~0.5 × 10 -5 nm · cm -1 · Pa -1. In particular, in Examples 1 to 16, the photoelastic constant (β) is −0.1 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ^{−1 to} 0.3 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ^{−. An} optical glass having a very small photoelastic constant in the range of ¹ was realized.

FIG. 1 is a plot of photoelastic constant values when incident light at 644 nm and 436 nm is used in each example. As apparent from FIG. 1, the difference between the photoelastic constant at 644 nm and the photoelastic constant at 436 nm is −0.1 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ^{−1 to} 0.1 × 10 ⁻⁵ nm · cm ^{−. It} was very small at ¹ · Pa ⁻¹ .

On the other hand, in order to investigate the photoelastic constants of known fluorophosphate optical glasses, glass of Comparative Examples A to I shown in Tables 7 to 9 was prepared, and physical property acquisition was attempted. In Tables 7 to 9, when the symbols in the examples are the same, it means samples having the same composition.
Comparative Examples A and B are Examples 14 and 22 of JP-A-11-60267, Comparative Examples C and D are Examples 14 and 24 of JP-A-50-50416, and Comparative Example E is JP-A-11-60267. Example 24 of JP-A-57-123842, Comparative Examples F and G are Examples 7 and 22 of JP-A-59-18133, and Comparative Example H is Example 6 of JP-A-10-53434, Comparative Example I is Example No. 47 of USP-5969861. Table 7 is a glass component description according to Configuration 2 (they are the same as the descriptions in each publication), Table 8 is a glass component description according to Configuration 4, and Table 9 Is a glass component description according to Configuration 5. In Comparative Examples B and C, devitrification was precipitated during cooling, so that a transparent glass could not be obtained, and physical properties could not be evaluated. Other examples were optical constants close to a refractive index nd≈1.60 and an Abbe number νd≈60, except for Examples A, E, and H, the photoelastic constant was 0.5 × 10 ^{−. It} is larger than ⁵ nm · cm ⁻¹ · Pa ⁻¹ , and is far from the desired characteristics in the present invention. Considering that the photoelastic constant of general glass is about 2.0 to 3.0 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ⁻¹ , it can be said that the photoelastic constant is relatively small. In applications that require highly accurate polarization control, such as a polarizing beam splitter, it is not sufficient because it is desirably close to zero.

  In Comparative Examples A and E, the optical constants (refractive index nd and Abbe number νd) deviate significantly from the desired ranges in the present invention. For example, when a polarizing beam splitter is formed using these glasses, There are tremendous difficulties in obtaining good polarization separation characteristics in fabrication.

In Comparative Example H, when the refractive index (nd) is 1.60 to 1.62, the photoelastic constant (β) is −0.1 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ^{−1 to} 0. Since the range of 4 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ⁻¹ is more preferable, it cannot be said that it is practically sufficient. For example, when Examples 2 and 4 having the same refractive index are compared with Comparative Example H, the photoelastic constant of Comparative Example H is twice or more. Therefore, when the glass of Comparative Example E is used as an optical element, Undesirable birefringence is more likely to occur than the optical elements made in Examples 2 and 4.

Further, in the publication, the fluorophosphate glass of Comparative Example I has a refractive index nd = 1.527, an Abbe number νd = 72.8, and a photoelastic constant at a He—Ne laser wavelength (633 nm) of 0.43. Although it is described as × 10 ⁻⁸ cm / N (= 0.43 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ⁻¹ ), when additional tests were performed, fine devitrification or phase separation was observed in the glass. A transparent glass was not obtained (milky appearance). Although physical property acquisition was performed with milky white glass, as shown in Tables 7 to 9, physical property values close to the values described in the publication were not obtained.

  Although the present invention has been described in detail for the purpose of illustration, this embodiment is only for the purpose of illustration, and many modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention. Will be understood.

It is a graph which shows the photoelastic constant of each Example of this invention.

Claims (7)

As an atom constituting the glass, having a refractive index (nd) of 1.60 to 1.68 and an Abbe number (νd) of 40 or more and less than 65,
P 5-10 mol%
Al 1-3 mol%
Ba 8-13 mol%
Gd 1-5 mol%
Nb 0.1-3 mol%
F 15-35 mol% and O 40-52 mol%
In ^{0.1 × 10 -5 ~0.1 × 10 -5} nm · cm -1 · Pa -1 - for each component viewed contains a proportion, a difference between the photoelastic constant at photoelastic constant and 436nm in 644nm is Some optical glass.
As an atom constituting the glass, having a refractive index (nd) of 1.60 to 1.68 and an Abbe number (νd) of 40 or more and less than 65,
P 5 to 10 mol%
Al 1-3 mol%
B a 8 to 13 mol%
G d 1 to 5 mol%
N b 0. 1 to 3 mol%
F 15 to 35 mol%
O 40 to 52 mol% and Y 0 to 2 mol% and / or La 0 to 2 mol% and / or Y b 0 to 1 mol% and / or Ta 0 to 1 mol% and / or Lu 0 to 1 mol% and / or T i 0 to 1. 5 mol% and / or Zr0-1. 5 mol% and / or W0-1. 5 mol% and / or B i 0 to 1. 5 mol% and / or Mg 0 to 2 mol% and / or Ca 0 to 3 mol% and / or Sr 0 to 5 mol% and / or Zn 0 to 2 mol% and / or Li 0 to 2 mol% and / or Na 0 to 2 mol% and / or K 0 to 2 mol% and / or C s 0 to 1 mol% and / or T 10 to 3 mol% and / or Si 0 to 2 mol% and / or B0-2 mol% and / or Sb0-1 mol%
In ^{0.1 × 10 -5 ~0.1 × 10 -5} nm · cm -1 · Pa -1 - of viewing including the components of the percentage difference between the photoelastic constant at photoelastic constant and 436nm in 644nm is Some optical glass.
Having a refractive index (nd) of 1.60 to 1.68 and an Abbe number (νd) of 40 or more and less than 65;
P ₂ O ₅ 12 to less than 2 to 22%,
Al ₂ O ₃ 1 to 4.5 %
BaO 40-55%
_{G d 2 O 3 8 ~ 2} 5% and N _b 2 _O 5 0. 5 to 8% and Y ₂ O ₃ 0 to 10% and / or La ₂ O ₃ 0 to 10% and / or Y b ₂ O ₃ 0 to 5% and / or Ta ₂ O ₅₀ 0 to 5 % and / or _{L u 2 O 3 0 ~ 5} % and / or T i _O 2 0 ~ 7% and / or Z r _O 2 0 ~ 5% and / or W _O 3 0 ~ 7% and / or B i ₂ O ₃₀ to 5% and / or MgO 0 to 1% and / or CaO 0 to 5% and / or SrO 0 to 10% and / or ZnO 0 to 5% and / or Or Li ₂ O 0 to 1% and / or Na ₂ O 0 to 3% and / or K ₂ O 0 to 3% and / or C s ₂ O 0 to 5% and / or T l ₂ O 0 to 1 5% and / or S i _O 2 0 ~ 3% and / or _B 2 _O 3 0 ~ 3% and / or S b ₂ O ₃₀ to 3%
The total amount of F 1 containing one or two or more of the above oxide-converted compositions and fluoride-substituted part or all of one or more of the above oxides is 8 to 20 weights per 100 parts by weight of the oxide-converted composition. Optical glass having a difference between the photoelastic constant at 644 nm and the photoelastic constant at 436 nm of −0.1 × 10 ^{−5 to} 0.1 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ⁻¹ .
When the refractive index (nd) is in the range of 1.60 to 1.62, the photoelastic constant at 546 nm is −0.1 × 10 ^{−5 to} 0.3 × 10 ⁻⁵ nm · cm ⁻¹ · Pa ⁻¹ . In addition, when the refractive index (nd) is in the range of 1.62 to 1.68, the photoelastic constant at 546 nm is −0.1 × 10 ^{−5 to} 0.5 × 10 ⁻⁵ nm · cm ^−1. The optical glass according to any one of claims 1 to 3 , which is Pa- ¹ .
The refractive index (nd) is 1.60 to 1.65, the Abbe number (νd) is less than 50 to 65, and the photoelastic constant at 546 nm is −0.1 × 10 ^{−5 to} 0.3 ×. 1 0 ^-5 nm · optical glass according to any one of claims 1-4, characterized in that the cm-1 · Pa-1.
The optical glass according to any one of claims 1 to 5 containing no lead compounds.
Using the optical glass according to any one of claims 1 to 6 polarizing beam splitter for a liquid crystal projector.

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