TW201912600A - Near infrared absorbing glass - Google Patents

Abstract

Provided is a near-infrared radiation absorption glass, the use of which enables a reduction in the thickness of an optical device and which demonstrates excellent weather resistance, devitrification resistance, and optical properties even without the inclusion of fluorine. The near-infrared radiation absorption glass is characterized by the inclusion, in percentages by mass, of 20 to 80% P2O5, 1 to 50% RO (where R represents at least one selected from among Mg, Ca, Sr and Ba), 0.1 to 30% MgO, 0 to 15% Na2O, 0 to less than 14% K2O, and 0.1 to 30% CuO, and by the thickness thereof being 0.25 mm or less.

Description

Near infrared absorbing glass

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

Generally speaking, in order to realize the visibility correction of solid-state imaging devices such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), cameras in optical devices such as digital cameras or smart phones Some use near-infrared absorbing glass. For example, Patent Document 1 discloses a fluorine-containing phosphoric acid-based near-infrared absorbing glass. Since fluorine has a high effect of improving the weather resistance, the near-infrared absorbing glass described in Patent Document 1 is excellent in weather resistance. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2004-83290

[Problems to be solved by the invention]

Since the fluorine component is an environmentally hazardous substance, its use has been restricted in recent years. However, when the fluorine component is not contained, it is difficult to improve the weather resistance, and if the weather resistance is to be improved, problems such as devitrification resistance and degradation of optical characteristics are liable to occur. In addition, in recent years, the industry has strongly desired to reduce the thickness of optical devices, and it is necessary to make the near-infrared absorbing glass thin. However, when making thinner near-infrared absorbing glass, higher devitrification resistance is required.

In view of the foregoing, an object of the present invention is to provide a near-infrared absorbing glass that can reduce the thickness of an optical device and is excellent in various characteristics of weather resistance, devitrification resistance, and optical characteristics even when fluorine is not contained. [Technical means to solve the problem]

The near-infrared absorbing glass of the present invention is characterized in that it contains 20 to 80% of P ₂ O ₅ and RO (wherein R is at least one selected from the group consisting of Mg, Ca, Sr, and Ba) in terms of mass 1 to 50. %, MgO 0.1 to 30%, Na ₂ O 0 to 15%, K ₂ O 0 to 14%, and CuO 0.1 to 30%, and the thickness is 0.25 mm or less.

The near-infrared absorbing glass of the present invention limits the RO which improves the devitrification resistance to 1% or more, the Na ₂ O which reduces the devitrification resistance to 15% or less, and the K ₂ O limitation to less than 14%. And achieve higher devitrification resistance. Therefore, it can also be applied to forming methods that are likely to be accompanied by devitrification, such as a down-draw method and a retraction method, which can efficiently produce a small thickness of infrared absorbing glass.

The near-infrared absorbing glass of the present invention preferably further contains Al ₂ O ₃ 0 to 19% and ZnO 0 to 13% in terms of mass%.

The near-infrared absorbing glass of the present invention is preferably free of a fluorine component. Here, "fluorine-free component" means that it is contained inadvertently and does not exclude the inevitable mixing of impurities. Specifically, it means that the content of the fluorine component is 1000 ppm or less. [Effect of the invention]

According to the present invention, it is possible to provide a near-infrared absorbing glass that can reduce the thickness of an optical device and is excellent in various characteristics of weather resistance, devitrification resistance, and optical characteristics even when fluorine is not included.

The near-infrared absorbing glass of the present invention contains 20 to 80% of P ₂ O ₅ , RO (wherein R is at least one selected from Mg, Ca, Sr, and Ba) 1 to 50%, MgO 0.1 to 30%, and Na ₂ O 0 to 15%, K ₂ O 0 to 14%, and CuO 0.1 to 30%. The reason for limiting the glass composition to the above is explained below. In addition, in the following description regarding the content of each component, unless otherwise specified, "%" means "mass%".

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%, and particularly preferably 45 to 67%. When the content of P ₂ O ₅ is too small, the glass transition tends to become unstable. On the other hand, when the content of P ₂ O ₅ is too large, the liquid phase viscosity decreases, the devitrification resistance decreases, or the weather resistance decreases.

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

In addition, the preferable range of 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 from 0.1 to 30%, particularly preferably from 0.4 to 13%. When the content of MgO is too small, it is difficult to obtain the above effects. On the other hand, if the content of MgO is too large, the stability of glass transition tends to decrease.

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

SrO is a component that improves devitrification resistance and weather resistance similarly to MgO. The content of SrO is preferably from 0 to 12%, particularly preferably from 0.3 to 6%. When the content of SrO is too large, the stability of glass transition is liable to decrease.

BaO is a component that improves devitrification resistance and weather resistance similarly to MgO. The content of BaO is preferably 0 to 30%, 1 to 25%, and particularly preferably 3 to 20%. If the content of BaO is too large, crystals due to BaO are easily precipitated during the forming process.

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

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

K ₂ O is a component that lowers the melting temperature similarly to Na ₂ O. The content of K ₂ O is preferably from 0 to 14%, particularly preferably from 0.1 to 12%. If the content of K ₂ O is too large, crystals due to K ₂ O tend to precipitate during the forming process, 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 content of CuO is too small, it is difficult to obtain the desired near-infrared absorption characteristics. On the other hand, if the content of CuO is too large, the transmittance in the ultraviolet to visible light region tends to decrease. Moreover, there exists a tendency for devitrification resistance to fall.

In addition to the above-mentioned components, various components shown below may 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%. When the content of Al ₂ O ₃ is too large, there is a tendency that the melting property decreases and the melting temperature increases. Furthermore, if the melting temperature rises, Cu ions are reduced, and it is easy to convert from Cu ²⁺ to Cu ⁺ , so it is not easy to obtain the required optical characteristics. Specifically, the light transmittance in the near-ultraviolet to visible light range is likely to decrease or the near-infrared absorption characteristic is likely to decrease.

ZnO is a component that improves devitrification resistance and weather resistance. The content of ZnO is preferably 0 to 13%, 0.1 to 12%, and particularly preferably 1 to 10%. If the content of ZnO is too large, the melting property will decrease and the melting temperature will increase. As a result, it will be difficult to obtain the required optical characteristics. In addition, crystals due to ZnO tend to precipitate during the forming process, which tends to reduce the devitrification resistance.

Li ₂ O is a component that lowers the melting temperature. The content of Li ₂ O is preferably 0 to 15%, particularly preferably 0.1 to 10%. If the content of Li ₂ O is too large, 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 , and Sb ₂ O may be contained within a range that does not impair the effects of the present invention. ₃ etc. Specifically, the contents of these components are preferably 0 to 3%, particularly preferably 0 to 2%. In addition, since the fluorine component is an environmentally hazardous substance, it is preferably not contained.

The near-infrared absorbing glass of the present invention is generally used in a plate shape. 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 is 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 composition, the near-infrared absorbing glass of the present invention can achieve both high transmittance in the visible light 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, and 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 liquid-phase 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 liquid phase viscosity is too low, devitrification is liable to occur during molding.

The near-infrared absorbing glass of the present invention can be produced by melting and forming a raw material powder batch prepared in such a manner as to have a desired composition. The melting temperature is preferably 900 to 1200 ° C. If the melting temperature is too low, it is difficult to obtain a homogeneous glass. On the other hand, if the melting temperature is too high, Cu ions are reduced, and it is easy to convert from Cu ²⁺ to Cu ⁺ , so it is not easy to obtain the required optical characteristics.

Thereafter, the molten glass is formed into a specific shape, and subsequent processing can be performed as necessary, and it can be used for various purposes. Furthermore, in order to efficiently manufacture a near-infrared absorbing glass having a small thickness, it is preferable to apply a forming method such as a down-draw method and a retraction method. Since these forming methods are liable to be accompanied by devitrification, it is easy to enjoy the effect of the near-infrared absorbing glass of the present invention having excellent devitrification resistance. [Example]

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

[Table 1]

(1) Preparation of each sample First, a glass raw material prepared so as 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. Thereafter, annealing was performed to obtain a sample.

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

The light transmission characteristics were measured using a spectroscopic analysis device (UV3100 manufactured by Shimadzu Corporation), and the transmittances at 500 nm, 700 nm, and 1200 nm were measured on samples having the thicknesses described in Table 1 on both sides by mirror polishing. Furthermore, as long as the transmittances at wavelengths of 500 nm, 700 nm, and 1200 nm are 77%, 28%, and 38%, respectively, it can be judged that the light transmission characteristics are good.

The weather resistance is determined by the presence or absence of changes in the appearance of the specimens that have been mirror-polished on both sides for 24 hours at a temperature of 120 ° C and a relative humidity of 100%. Specifically, those who did not see a change in appearance after the test were evaluated as "○", and those who saw a change in appearance such as whitening were evaluated as "x".

The liquid phase viscosity is obtained as follows. The sample obtained by coarsely pulverizing so that the particle size became 300 to 600 μm was placed in a platinum container and kept in a temperature gradient furnace for 24 hours. The highest temperature at which the interface crystals are precipitated on the bottom surface of the platinum container is set as the liquidus temperature. Then measure the viscosity of the sample, and set the viscosity at the liquidus temperature to the liquidus viscosity.

According to Table 1, it is clear that the samples No. 1 to No. 8 in the examples of the present invention have high transmittance in the visible light region and large absorption in the near-infrared region. Moreover, in the evaluation of weather resistance, no change was observed before and after the test, the liquid phase viscosity was also 10 ^1.6 dPa · s or more, and the devitrification resistance was also excellent. Furthermore, since the thickness is 0.23 mm or less, it is easy to reduce the thickness of the optical device.

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

Claims (3)

A near-infrared absorbing glass characterized by containing 1 to 50% by mass% of P ₂ O ₅ 20 to 80% and RO (wherein R is at least one selected from the group consisting of Mg, Ca, Sr, and Ba) , MgO 0.1 to 30%, Na ₂ O 0 to 15%, K ₂ O 0 to less than 14%, and CuO 0.1 to 30%, and the thickness is 0.25 mm or less. For example, the near-infrared absorbing glass of claim 1 further contains Al ₂ O ₃ 0 to 19% and ZnO 0 to 13% in terms of mass%. If the near-infrared absorbing glass of claim 1 or 2 does not contain fluorine.