JP7071608B2 - Near infrared absorber glass - Google Patents

Description

The present invention relates to a near-infrared absorbing glass capable of selectively absorbing near-infrared rays.

In general, near-infrared absorbing glass is used for the camera portion in an optical device such as a digital camera or a smartphone for the purpose of correcting the visual sensitivity of a solid-state image sensor such as a CCD or CMOS. For example, Patent Document 1 discloses a phosphoric acid-based near-infrared absorbing glass containing fluorine. Since fluorine has a high effect of improving weather resistance, the near-infrared absorbing glass described in Patent Document 1 has excellent weather resistance.

Japanese Unexamined Patent Publication No. 2004-83290

Since the fluorine component is an environmentally hazardous substance, its use has been restricted in recent years. However, when it does not contain a fluorine component, it is difficult to improve the weather resistance, and when trying to improve the weather resistance, problems such as devitrification resistance and deterioration of optical characteristics are likely to occur. Further, in recent years, it is strongly desired to make the optical device thinner, and it is necessary to make the near-infrared absorbing glass thinner. However, in order to produce a thin near-infrared absorbing glass, higher devitrification resistance is required.

In view of the above, the present invention provides a near-infrared absorbing glass that can be made thinner and has excellent weather resistance, devitrification resistance, and optical characteristics even when it does not contain fluorine. The purpose is.

The near-infrared absorbing glass of the present invention has _{P2O 5 20} to 80% by mass, RO (where R is at least one selected from Mg, Ca, Sr and Ba) 1 to 50%, MgO 0. It is characterized by containing 1 to 30%, Na ₂ O 0 to 15%, K ₂ O 0 to less than 14%, and CuO 0.1 to 30%, and having a thickness of 0.25 mm or less.

The near-infrared absorbing glass of the present invention regulates RO for improving devitrification resistance to 1% or more, Na ₂ O for reducing devitrification resistance to 15% or less, and K ₂ O to less than 14%. Achieves high devitrification resistance. Therefore, it can also be applied to molding methods such as a down draw method and a redraw method, which can efficiently manufacture infrared absorbing glass having a small thickness, which are likely to cause devitrification.

The near-infrared absorbing glass of the present invention further preferably contains Al _{2O 30} to 19% and ZnO 0 to 13% in mass%.

The near-infrared absorbing glass of the present invention preferably does not contain a fluorine component. Here, "does not contain a fluorine component" means that it is intentionally not contained, and does not exclude the inclusion of unavoidable impurities. Specifically, it means that the content of the fluorine component is 1000 ppm or less.

According to the present invention, it is possible to provide a near-infrared absorbing glass having excellent weather resistance, devitrification resistance and optical characteristics even when the optical device can be made thinner and does not contain fluorine. It will be possible.

The near-infrared absorbing glass of the present invention has _{P2O 5 20-80} %, RO (where R is at least one selected from Mg, Ca, Sr and Ba) 1-50%, MgO 0.1-30%. , Na _{2O 0-15} %, K2O 0-14%, and CuO 0.1-30%. The reason for limiting the glass composition as described above will be described below. In the following description of the content of each component, "%" means "mass%" unless otherwise specified.

P ₂ O ₅ is an indispensable component for forming a glass skeleton. The content of P ₂ O ₅ is 20 to 80%, preferably 31 to 73%, particularly preferably 45 to 67%. If the content of P ₂ O ₅ is too low, vitrification tends to be unstable. On the other hand, if the content of P ₂ O ₅ is too large, the liquidus viscosity is lowered, the devitrification resistance is lowered, and the weather resistance is likely to be lowered.

RO (where R is at least one selected from Mg, Ca, Sr and Ba) is a component that improves devitrification resistance and weather resistance. The total content of RO is 1 to 50%, preferably 3 to 34%, particularly preferably 6 to 20%. If the content of RO is too small, it is difficult to obtain the above effect. On the other hand, if the RO content is too high, the devitrification resistance is lowered and crystals due to the RO component are likely to precipitate.

The preferred range of the content of each component of RO is as follows.

MgO is a component that improves devitrification resistance and weather resistance. The content of MgO is preferably 0.1 to 30%, particularly preferably 0.4 to 13%. If the content of MgO is too small, it is difficult to obtain the above effect. On the other hand, if the content of MgO is too large, the stability of vitrification tends to decrease.

Like MgO, CaO is a component that improves devitrification resistance and weather resistance. The CaO content is preferably 0 to 15%, particularly preferably 0.4 to 7%. If the CaO content is too high, the stability of vitrification tends to decrease.

Similar to MgO, SrO is also a component that improves devitrification resistance and weather resistance. The content of SrO is preferably 0 to 12%, particularly preferably 0.3 to 6%. If the content of SrO is too high, the stability of vitrification tends to decrease.

Like MgO, BaO is also a component that improves devitrification resistance and weather resistance. The content of BaO is preferably 0 to 30%, 1 to 25%, and particularly preferably 3 to 20%. If the BaO content is too high, crystals due to BaO are likely to precipitate during molding.

As described above, RO has an effect of improving devitrification resistance, and it is easy to enjoy the effect especially when P ₂ O ₅ is low.

Na ₂ O is a component that lowers the melting temperature. The content of Na ₂ O is 0 to 15%, particularly preferably 0.1 to 10%. If the content of Na ₂ O is too high, the devitrification resistance tends to decrease.

Like Na ₂ O, K ₂ O is also a component that lowers the melting temperature. The content of K2O is less than ₀ to 14%, particularly preferably 0.1 to 12%. If the content of K ₂ O is too large, crystals derived from K ₂ O tend to precipitate during molding, and the devitrification resistance tends to decrease.

CuO is an essential component for absorbing near infrared rays. The content of CuO is preferably 0.1 to 30%, 0.3 to 20%, 2 to 15%, and particularly preferably 3 to 13%. If the CuO content is too low, it becomes difficult to obtain the desired near-infrared absorption characteristics. On the other hand, if the content of CuO is too large, the light transmittance in the ultraviolet to visible region tends to decrease. In addition, the devitrification resistance tends to decrease.

In addition to the above components, various components shown below can be contained.

Al ₂ O ₃ is a component that improves weather resistance, increases liquid phase viscosity, and improves devitrification resistance. The content of Al ₂ O ₃ is preferably 0 to 19%, 2 to 19%, 3 to 14%, and particularly preferably 3 to 9%. If the content of Al ₂ O ₃ is too large, the meltability tends to decrease and the melting temperature tends to rise. When the melting temperature rises, Cu ions are reduced and it becomes easy to shift from Cu ²⁺ to Cu ⁺ , so that it becomes difficult to obtain desired optical characteristics. Specifically, the light transmittance in the near-ultraviolet to visible region tends to decrease, and the near-infrared absorption characteristic tends to decrease.

ZnO is a component that improves devitrification resistance and weather resistance. The ZnO content is preferably 0 to 13%, 0.1 to 12%, and particularly preferably 1 to 10%. If the ZnO content is too high, the meltability is lowered and the melting temperature is raised, and as a result, it becomes difficult to obtain desired optical characteristics. In addition, crystals caused by ZnO tend to precipitate during molding, and the devitrification resistance tends to decrease.

Li ₂ O is a component that lowers the melting temperature. The content of Li ₂ O is 0 to 15%, particularly preferably 0.1 to 10%. If the content of Li ₂ O is too high, the devitrification resistance tends to decrease.

In addition to the above components, B ₂ O ₃ , Nb ₂ O ₅ , Y ₂ O ₃ , La ₂ O ₃ , Ta ₂ O ₅ , CeO ₂ , Sb ₂ O ₃ and the like are within the range that does not impair the effects of the present invention. It may be contained in. Specifically, the content of each of these components is preferably 0 to 3%, particularly preferably 0 to 2%. Since the fluorine component is an environmentally hazardous substance, it is preferable not to contain it.

The near-infrared absorbing glass of the present invention is usually used in the form of a plate. The thickness is 0.25 mm or less, preferably 0.2 mm or less, 0.15 mm or less, and particularly preferably 0.1 mm or less. If the thickness is too large, it becomes difficult to reduce the thickness of the optical device. The lower limit of the thickness is not particularly limited, but is preferably 0.01 mm or more from the viewpoint of mechanical strength.

By having the above-mentioned composition, the near-infrared absorbing glass of the present invention can achieve both high light transmittance in the visible region and excellent light absorption characteristics in the near-infrared region. Specifically, the light transmittance at a wavelength of 500 nm is preferably 75% or more, particularly preferably 77% or more. On the other hand, the light transmittance at a wavelength of 700 nm is preferably 30% or less, particularly preferably 28% or less, and the light transmittance at a wavelength of 1200 nm is preferably 40% or less, particularly preferably 38% or less.

The liquidus viscosity of the near-infrared absorbing glass of the present invention is preferably 10 ^1.6 dPa · s or more, particularly preferably 10 ^1.9 dPa · s or more. If the liquidus viscosity is too low, it tends to devitrify during molding.

The near-infrared absorbing glass of the present invention can be produced by melting and molding a raw material powder batch prepared to have a desired composition. The melting temperature is preferably 900 to 1200 ° C. If the melting temperature is too low, it will be difficult to obtain homogeneous glass. On the other hand, if the melting temperature is too high, Cu ions are reduced and it becomes easy to shift from Cu ²⁺ to Cu ⁺ , so that it becomes difficult to obtain desired optical characteristics.

After that, the molten glass can be formed into a predetermined shape, subjected to necessary post-processing, and used for various purposes. In addition, in order to efficiently produce a near-infrared absorbing glass having a small thickness, it is preferable to apply a molding method such as a down draw method or a redraw method. Since these molding methods are liable to cause devitrification, it is easy to enjoy the effect of the near-infrared absorbing glass of the present invention having excellent devitrification resistance.

Hereinafter, the near-infrared absorbing glass of the present invention will be described in detail based on examples, but the present invention is not limited to these examples.

Table 1 shows Examples (Samples Nos. 1 to 8) and Comparative Examples (Samples Nos. 9 and 10) of the present invention.

(1) Preparation of Each Sample First, a glass raw material prepared to have the composition shown in Table 1 was put into a platinum crucible and melted at a temperature of 1000 to 1200 ° C. Next, the molten glass was poured onto a carbon plate and cooled and solidified. Then, annealing was performed to obtain a sample.

(2) Evaluation of each sample The light transmission characteristics, weather resistance and liquid phase viscosity of each obtained sample were measured or evaluated by the following methods. The results are shown in Table 1.

As for the light transmittance, the transmittances of the samples having the thickness shown in Table 1 with both sides mirror-polished were measured at wavelengths of 500 nm, 700 nm and 1200 nm using a spectroscopic analyzer (UV3100 manufactured by Shimadzu Corporation). When the transmittances at wavelengths of 500 nm, 700 nm and 1200 nm are 77% or more, 28% or less, and 38% or less, respectively, it can be determined that the light transmission characteristics are good.

The weather resistance was determined by the presence or absence of a change in appearance of the sample whose both sides were mirror-polished after being held for 24 hours under the conditions of a temperature of 120 ° C. and a relative humidity of 100%. Specifically, those showing no change in appearance after the test were evaluated as "○", and those showing no change in appearance such as white discoloration were evaluated as "x".

The liquid phase viscosity was determined as follows. A sample coarsely crushed to a particle size of 300 to 600 μm was placed in a platinum container and kept in a temperature gradient furnace for 24 hours. The maximum temperature at which interfacial crystals were deposited on the bottom surface of the platinum container was defined as the liquidus temperature. Then, the viscosity of the sample was measured, and the viscosity at the liquid phase temperature was taken as the liquid phase viscosity.

As is clear from Table 1, No. 1 which is an embodiment of the present invention. The samples 1 to 8 had high light transmittance in the visible region and large absorption in the near infrared region. In addition, no change was observed before and after the test in the weather resistance evaluation, the liquidus viscosity was 10 ^1.6 dPa · s or more, and the devitrification resistance was also excellent. Since the thickness is 0.23 mm or less, it is easy to make the optical device thinner.

On the other hand, No. The sample of No. 9 was inferior in weather resistance and inferior in devitrification resistance because the liquid phase viscosity was 10 ^1.2 dPa · s. No. Since the liquid phase viscosity of 10 samples was 10 ^1.3 dPa · s, the devitrification resistance was inferior.

Claims (2)

By mass%, P ₂ O ₅ 20 to 55.3 %, RO (where R is at least one selected from Mg, Ca, Sr and Ba) is 8.2 to 50% in total, MgO 2.1. ~ 30%, CaO 0.4 ~ 15%, BaO 4.6 ~ 30%, Na ₂ O 0 ~ 10%, K ₂ O 0.1 ~ less than 14%, Al ₂ O ₃ 4.5 ~ 19% and A near-infrared absorbing glass characterized by containing 6.6 to 30% of CuO , containing no fluorine component, and having a thickness of 0.25 mm or less. The near-infrared absorbing glass according to claim 1, further comprising 0 to 13% of Z nO in mass%.