JP6241653B2 - Optical glass - Google Patents

Description

  The present invention relates to an optical glass used for an optical element such as an infrared cut filter.

  BACKGROUND ART Conventionally, fluorophosphate glass that absorbs light of a certain wavelength in the infrared region has been widely used as infrared absorption glass used for a camera portion in a digital camera or a smartphone. For example, Patent Documents 1 to 3 disclose Cu-containing fluorophosphate glasses that cut light in the near infrared region.

International Publication No. 2012/18026 International Publication No. 2011/71157 International Publication No. 2012/20857

An infrared cut filter made of Cu-containing fluorophosphate glass utilizes the infrared absorbing ability of Cu ²⁺ . Accordingly, it is possible to obtain excellent infrared absorption characteristics by allowing Cu ions in the glass to be stably present in a divalent state. However, when Cu-containing fluorophosphate glass is melted, the glass tends to shift on the reduction side, and Cu is easily reduced to become monovalent. For this reason, desired absorption characteristics by Cu ions may not be obtained.

  In addition, since fluorophosphate glass generally has a low molding viscosity, there is also a problem that glass components volatilize during molding, causing striae and the like, which tends to be inhomogeneous.

  In view of the above, an object of the present invention is to provide an optical glass that has desired near-infrared absorption characteristics, is less likely to cause defects such as striae during molding, and can be mass-produced.

The optical glass of the present invention is cation%, P ⁵⁺ 15-50%, Al ³⁺ 7-18%, R ²⁺ 10-50% (R is at least one selected from Mg, Ca, Sr, Ba and Zn) ^{), R '+ 5~40% (} R' at least one is selected from Li, Na and ^K), Cu 2+ 2~12%, and, by ^{anionic%, F - 10~60%, O} 2- The liquid phase temperature is 700 ° C. or lower, the liquid phase viscosity is 10 ^0.5 poise or higher, and the glass transition point is 360 ° C. or lower.

The optical glass of the present invention contains cation 2%, Mg ²⁺ 2 to 20%, Ca ²⁺ 2 to 20%, Sr ²⁺ 2 to 50%, Ba ²⁺ 2 to 20%, and Zn ²⁺ 0 to 10%. preferable.

The optical glass of the present invention preferably contains Li ⁺ 5 to 40%, Na ⁺ 0 to 3% and K ⁺ 0 to 3%.

  The optical glass of the present invention preferably has a transmittance at a wavelength of 500 nm of 80% or more and a transmittance at a wavelength of 800 nm of less than 5% at a thickness at which the transmittance at 615 nm is 50%.

  The infrared cut filter of the present invention is made of any one of the above optical glasses.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the optical glass which has a desired near-infrared absorption characteristic, cannot produce troubles, such as a striae at the time of shaping | molding, and can be mass-produced.

The optical glass of the present invention is cation%, P ⁵⁺ 15-50%, Al ³⁺ 7-18%, R ²⁺ 10-50% (R is at least one selected from Mg, Ca, Sr, Ba and Zn) ^{), R '+ 5~40% (} R' at least one is selected from Li, Na and ^K), Cu 2+ 2~12%, and, by ^{anionic%, F - 10~60%, O} 2- Contains 40-90%. The reason why the glass composition is limited as described above will be described below.

P ⁵⁺ is an essential component for forming a glass skeleton. The content of P ⁵⁺ is 15 to 50%, preferably 17 to 45%, more preferably 20 to 40%, and still more preferably 23 to 37%. When there is too little content of ^{P5 +} , there exists a tendency for a liquidus temperature and a glass transition point to become high. Therefore, melting at a high temperature is required, Cu ions in the glass are reduced, and it becomes difficult to obtain desired optical characteristics. On the other hand, when there is too much content of ^{P5 +} , chemical durability will fall easily.

Al ³⁺ is a component that improves chemical durability. The content of Al ³⁺ is 7 to 18%, preferably 10 to 18%, and more preferably 12 to 16%. If the content of Al ³⁺ is too small, the above effect is difficult to obtain. On the other hand, when the content of Al ³⁺ is too large, the glass transition point tends to be high. Moreover, there exists a tendency for liquidus temperature to become high (liquidus viscosity becomes low).

R ²⁺ (R is at least one selected from Mg, Ca, Sr, Ba and Zn) is an effective component for lowering the glass transition point. Moreover, there exists an effect which improves a weather resistance. The content of R ²⁺ is 10 to 50%, preferably 20 to 45%, and more preferably 30 to 40%. If the content of R ²⁺ is too small, it is difficult to obtain the above effect. On the other hand, when there is too much content of R ^<2+> , there exists a tendency for vitrification to become unstable. When 2 or more types are contained as R ²⁺ , the total amount should satisfy the above range.

The content of each component of R ²⁺ is preferably as follows.

The content of Mg ²⁺ , Ca ²⁺ and Ba ²⁺ is preferably 2 to 20%, more preferably 3 to 15%, and still more preferably 4 to 13%. The content of Sr ²⁺ is preferably 2 to 50%, more preferably 3 to 30%, and still more preferably 4 to 20%.

The content of Zn ²⁺ is preferably 0 to 10%, more preferably 0 to 5%, and still more preferably 0 to 1.5%. Zn ²⁺ is a component that is particularly effective in stabilizing vitrification and improving weather resistance. However, when there is too much content of Zn2 ⁺ , there exists a tendency for a glass transition point to become high.

R ′ ⁺ (R ′ is at least one selected from Li, Na and K) is a component that lowers the glass transition point and the liquid phase viscosity. The content of R ′ ⁺ is 5 to 40%, preferably 10 to 35%, and more preferably 15 to 25%. If the content of R ′ ⁺ is too small, the above effect is difficult to obtain. On the other hand, when there is too much content of R ' ⁺ , while vitrification will become unstable, there exists a tendency for chemical durability to fall. When two or more types are contained as R ′ ⁺ , the total amount should satisfy the above range.

The content of each component of R ′ ⁺ is preferably as follows.

By positively containing Li ⁺ among R ′ ^+, a glass having a low glass transition point can be stably obtained. The content of Li ⁺ is preferably 5 to 40%, more preferably 10 to 25%. When there is too little content of Li ^<+> , there exists a tendency for a glass transition point to become high. On the other hand, when there is too much content of Li ⁺ , there exists a tendency for liquid phase viscosity to fall and vitrification to become unstable.

The content of Na ⁺ is preferably 0 to 3%, preferably 0 to 2%, and more preferably not contained. When there is too much content of Na ⁺ , there exists a tendency for liquid phase viscosity to fall and vitrification to become unstable.

The content of K ⁺ is preferably 0 to 3%, more preferably 0 to 1%. When there is too much content of K ⁺ , there exists a tendency for liquid phase viscosity to fall and vitrification to become unstable.

By containing Cu ²⁺ in the fluorophosphate glass of the present invention, light in the near infrared region can be sharply cut while maintaining high transmittance in the visible region. Therefore, it becomes a glass suitable as a near infrared cut filter. The content of Cu ²⁺ is 2 to 12%, preferably 3 to 10%. When there is too little content of Cu2 ⁺ , the said effect will become difficult to be acquired. On the other hand, when there is too much content of Cu2 ⁺ , vitrification tends to become unstable.

In addition, the optical glass of the present invention includes Bi ³⁺ , La ³⁺ , Y ³⁺ , Gd ³⁺ , Te ⁴⁺ , Si ⁴⁺ , Ta ⁵⁺ , Nb ⁵⁺ , Ti ⁴⁺ , Zr ⁴⁺ or Sb ³⁺ as cation components, You may make it contain in the range which does not impair the effect of this invention. Specifically, the content of these components is preferably 0 to 3%, and more preferably 0 to 1%.

Since the Pb component (Pb ²⁺ etc.) and the As component (As ³⁺ etc.) are environmentally hazardous substances, it is preferable that they are not substantially contained in the present invention. In addition, “substantially not containing” means not intentionally containing as a raw material, and objectively means that the content of each component is less than 0.1%.

When U or Th is mixed as an impurity in the glass raw material, α rays are emitted from the glass, and the α rays tend to cause defects in the signals of the CCD and CMOS. Therefore, particularly when the optical glass of the present invention is used as a visibility correction filter or a color adjustment filter, it is necessary to reduce these impurities as much as possible. Therefore, it is preferable that the contents of U and Th in the optical glass of the present invention are each 20 ppb or less. Further, the α dose emitted from the optical glass of the present invention is preferably 1.0 c / cm ² · h or less.

The composition of the anionic ^component, F - 10 to 60%, and ^contains a ^{O 2- 40~90%, F - 10~55} %, and preferably ^contains O 2-45 to 90%. If the content of F ⁻ is too small (the content of O ²⁻ is too large), variation in light transmittance between lots tends to increase. On the other hand, if the content of F ⁻ is too large (the content of O ²⁻ is too small), vitrification becomes difficult.

  The liquid phase temperature of the optical glass of the present invention is 700 ° C. or lower, preferably 680 ° C. or lower. If the liquidus temperature is too high, striae and the like occur during molding, and it becomes difficult to obtain a homogeneous glass.

The liquid phase viscosity of the optical glass of the present invention is 10 ^0.5 poise or more, preferably 10 ^0.6 poise or more. If the liquid phase viscosity is too low, striae and the like occur during molding, and it becomes difficult to obtain a homogeneous glass.

  The glass transition point of the optical glass of the present invention is 360 ° C. or lower, preferably 350 ° C. or lower, and more preferably 340 ° C. or lower. If the glass transition point is too high, the melting temperature tends to increase, and as a result, Cu ions are biased toward the reduction side, making it difficult to obtain desired infrared absorption characteristics. If the glass transition point is too low, the heat resistance tends to be inferior. When the heat resistance of glass is lowered, for example, when a film is formed on a molded glass member, the glass tends to be softened and deformed. Therefore, the glass transition point is preferably 280 ° C. or higher, more preferably 300 ° C. or higher, and further preferably 320 ° C. or higher.

  The optical glass of the present invention sharply cuts light in the near infrared region while having high transmittance in the visible light region. Specifically, the optical glass of the present invention may have a transmittance of 80% or more at a wavelength of 500 nm and a transmittance of less than 5% at a wavelength of 800 nm at a thickness where the wavelength at which the transmittance is 50% is 615 nm. preferable.

  The optical glass of the present invention is used as an optical element such as an infrared cut filter or a heat ray absorption filter after being molded or ground or polished so as to have a desired shape (for example, a flat plate shape) as necessary.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these Examples.

  Tables 1 and 2 show examples (Nos. 1 to 5) and comparative examples (Nos. 6 to 8) of the present invention.

(1) Preparation of sample First, the raw material prepared so that it might become each glass composition of Table 1 and 2 was thrown into the platinum crucible, and it fuse | melted so that it might become homogeneous at 700-850 degreeC. Next, a molten glass was poured out into a preheated mold and molded, and annealing was performed to prepare a sample.

(2) Evaluation of sample About the obtained sample, liquid phase temperature, liquid phase viscosity, a glass transition point, and the light transmission characteristic were measured. The results are shown in Tables 1 and 2.

The liquidus temperature was obtained by holding the molten glass for 2 hours in a container provided with a temperature gradient, then taking it out to room temperature, and confirming the presence or absence of crystals with a microscope. The temperature at which crystals were confirmed was defined as the liquidus temperature. The liquid phase viscosity was determined by the platinum ball pulling method at the liquid phase temperature. In the table, the value of the common logarithm (log ₁₀ η) of the liquid phase viscosity (η) is shown.

  The glass transition point was calculated | required from the intersection of the straight line of a low temperature range and the straight line of a high temperature range in the thermal expansion curve obtained with the thermal expansion measuring apparatus (dilatometer).

  The transmittance was measured as follows. About the sample which mirror-polished both surfaces, the spectral transmission characteristic in visible region-near-infrared region was measured using Shimadzu UV-3100PC, and the transmittance | permeability curve was obtained. The thickness of the sample was such that the transmittance at a wavelength of 615 nm was 50%. For the obtained transmittance curve, the transmittance at wavelengths of 500 nm and 800 nm was read.

(3) Result No. which is an example. Samples 1 to 5 had a liquidus temperature of 650 ° C. or lower, a liquidus viscosity of 10 ^0.8 poise or higher, and a glass transition point of 330 ° C. or lower. On the other hand, No. which is a comparative example. The samples 6 and 8 had a glass transition point as high as 370 ° C. or higher. No. 7 samples, the higher the liquidus temperature is 720 ° C., liquidus viscosity was as low as ^{10 0.4} poises.

  The optical glass of the present invention can be used for an infrared cut filter, a visibility correction filter, a color adjustment filter, and the like.

Claims (4)

^{Cationic%, P 5+ 15~ 29%,} Al 3+ 7~18%, R 2+ 10~50% ( at least one R is selected from Mg, Ca, Sr, Ba and Zn), R ^'+ 5~ 40% (R ′ is at least one selected from Li, Na and K), Li ^{+ 5 to} 19%, Na ⁺ 0 to 2%, K ⁺ 0 to 3%, Cu ²⁺ 2 to 12%, and
^{Anionic%, F - 42~60%, O} 2- 40~58%
Containing
An optical glass having a liquidus temperature of 700 ° C. or less, a liquidus viscosity of 10 ^0.5 poise or more, and a glass transition point of 360 ° C. or less. The cation% contains Mg ²⁺ 2-20%, Ca ²⁺ 2-20%, Sr ²⁺ 2-50%, Ba ²⁺ 2-20% and Zn ²⁺ 0-10%. The optical glass described. At a thickness where the transmittance at 615 nm is 50%,
The optical glass according to claim 1 or 2, wherein the transmittance at a wavelength of 500 nm is 80% or more and the transmittance at a wavelength of 800 nm is less than 5%.   An infrared cut filter comprising the optical glass according to any one of claims 1 to 3.