JP2017165641A - Near-infrared absorption filter glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide near-infrared absorption filter glass which has desirable near-infrared absorption properties and excellent weather resistance and vitrification stability and furthermore is less susceptible to cracks or fractures in an annealing step after being formed.SOLUTION: The near-infrared absorption filter glass contains, in mass%, POof 65 to 80%, SiOof 1 to 10%, AlOof 7 to 25%, RO of 0.1 to 14% (R is at least one element selected from Li, Na and K), R'O of 1.5 to 20% (R' is at least one element selected from Mg, Ca, Sr, Ba and Zn), MgO of 1.5 to 20%, and CuO of 1 to 15%, and has a mass ratio PO/SiOof 10 to 80.SELECTED DRAWING: Figure 1

Description

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

  A near-infrared absorption filter is used in a camera portion of a digital camera or a smartphone for correcting the visibility of a solid-state imaging device such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). As glass used as a near-infrared absorption filter, what consists of phosphate type glass containing CuO is known, for example (for example, refer to cited reference 1). By containing a predetermined amount of CuO, the above glass can sharply cut near-infrared light having a wavelength in the vicinity of 700 to 1000 nm.

  In general, near infrared absorption filter glass is obtained by melting raw material powder, clarification and homogenization, casting and then slowly cooling and processing into a predetermined shape by cutting and polishing.

JP 2011-121792 A

  In general, the thermal expansion coefficient of phosphate glass is high, and cracks and cracks are likely to occur in the slow cooling step after molding. Further, such cracks and cracks are also likely to occur during so-called redraw molding in which a base glass plate is heated to form a thin plate during heat processing. Further, phosphate glass has a problem that weather resistance (particularly water resistance) is low. On the other hand, when component adjustment is performed to improve weather resistance, vitrification may become unstable.

  In view of the above, the present invention has the desired near-infrared absorption characteristics, is excellent in weather resistance and vitrification stability, and is unlikely to generate cracks or cracks during the slow cooling step after molding or thermal processing. It aims at providing the glass for near-infrared absorption filters.

Near infrared absorbing glass filter of the present invention, in _{mass%, P 2 O 5 65~80%} , SiO 2 1~10%, Al 2 O 3 7~25%, R 2 O 0.1~14% ( R is at least one selected from Li, Na and K), R′O 1.5-20% (R is at least one selected from Mg, Ca, Sr, Ba and Zn), MgO 1.5 20%, containing 1 to 15% CuO, characterized in that it is a _P 2 _O 5 _/ SiO 2 _10~80 mass ratio.

As a result of intensive studies by the present inventors, it has been found that the above-described problems can be solved by a near infrared absorption filter glass comprising a phosphate glass having the above composition. Note that near-infrared absorption filter glass of the present invention to contain a relatively large amount of P ₂ O _5, it has a characteristic that higher near infrared absorption by CuO ions. When the content of P ₂ O ₅ increases, the weather resistance tends to decrease, but in the glass of the present invention, by controlling the ratio of P ₂ O ₅ / SiO ₂ as described above, the decrease in weather resistance is suppressed. ing. “P ₂ O ₅ / SiO ₂ ” means the ratio of P ₂ O ₅ content to SiO ₂ content.

The near infrared absorption filter glass of the present invention preferably has a mass ratio of P ₂ O ₅ / R ₂ O of 9.2 or more. If it does in this way, it will become possible to improve vitrification stability.

The near-infrared absorption filter glass of the present invention is preferably% by mass, and Cr ₂ O ₃ 1% or less and NiO 1% or less. Cr ₂ O ₃ and NiO are components that reduce the light transmittance in the visible range. Therefore, by regulating these contents as described above, it becomes easy to obtain a glass excellent in light transmittance in the visible region.

It is preferable that the near infrared absorption filter glass of the present invention has a thermal expansion coefficient of 110 × 10 ⁻⁷ / ° C. or less in the range of 30 to 300 ° C. If it does in this way, generation | occurrence | production of the crack at the time of shaping | molding and a crack can be suppressed.

  The near infrared absorption filter glass of the present invention preferably has a crystal precipitation temperature of 1300 ° C. or lower. If it does in this way, it will become the glass excellent in vitrification stability. If the crystal precipitation temperature is low, the melting temperature can be lowered accordingly. When the melting temperature is increased, Cu ions are reduced, the near-infrared absorption characteristics (spectral characteristics) are lowered, and the light transmittance in the visible range is easily lowered. Therefore, the occurrence of the problem can be suppressed by lowering the melting temperature. In the present invention, “crystal precipitation temperature” refers to the temperature at which crystals begin to precipitate when the temperature of the homogeneous molten glass is lowered and held for 18 hours.

The near-infrared absorption filter glass of the present invention has a light transmittance of 30% or less at a wavelength of 1200 nm and a light transmittance at a wavelength of 500 nm at a thickness where the wavelength λ ₅₀ is 50% and the wavelength λ ₅₀ is 615 nm. It is preferably 84% or more.

  The near-infrared absorption filter of the present invention is characterized by comprising the glass for the near-infrared absorption filter described above.

  The near-infrared absorbing filter of the present invention preferably has a thickness of 0.1 to 1 mm.

  The glass for near-infrared absorption filters of the present invention has excellent weather resistance and vitrification stability while having desired near-infrared absorption characteristics. In addition, since it is difficult for cracks and cracks to occur in the slow cooling step after molding, it is possible to stably produce a sheet glass.

No. in Table 1 3 is a graph showing a light transmittance curve of a sample of 3.

Near infrared absorbing glass filter of the present invention, in _{mass%, P 2 O 5 65~80%} , SiO 2 1~10%, Al 2 O 3 7~25%, R 2 O 0.1~14% ( R is at least one selected from Li, Na and K), R′O 1.5-20% (R is at least one selected from Mg, Ca, Sr, Ba and Zn), MgO 1.5 20%, containing 1 to 15% CuO, characterized in that it is a _P 2 _O 5 _/ SiO 2 _10~80 mass ratio. The reason why the content range of each component is defined in this way will be described below.

P ₂ O ₅ is an essential component for forming a glass skeleton, and has an effect of lowering the crystal precipitation temperature. The content of P ₂ O ₅ is 65 to 80%, preferably 68 to 80%, 70 to 80% (but not including 70%), 71 to 78%, particularly 71 to 76%. When the content of P ₂ O ₅ is too small, there is a tendency for vitrification tends to be unstable. On the other hand, when the content of P ₂ O ₅ is too large, the weather resistance is lowered, there is a tendency that the coefficient of thermal expansion is increased.

SiO ₂ is a component that reinforces the glass skeleton. Moreover, it has the effect of reducing the thermal expansion coefficient and improving the weather resistance. The content of SiO ₂ is 1 to 10%, preferably 1.8 to 10%, 2.2 to 10%, 2.2 to 8%, and particularly preferably 2.5 to 6%. If the content of SiO ₂ is too small, the above effect is difficult to obtain. On the other hand, if the content of SiO ₂ is too large, rather weather resistance tends to lower. Also, vitrification tends to be unstable.

P ₂ O ₅ / SiO ₂ (weight ratio) is 10 to 80, 10～70,10～50,10～31, particularly preferably 10 to 29. If it does in this way, it will become easy to acquire the effect of the improvement of a weather resistance, and the fall of crystal precipitation temperature.

Al ₂ O ₃ is a component that improves weather resistance and lowers the thermal expansion coefficient. The content of Al ₂ O ₃ is 7 to 25%, preferably 8 to 23%, particularly preferably 10 to 20%. When the content of Al ₂ O ₃ is too small, the effect is difficult to obtain. On the other hand, when the content of Al ₂ O ₃ is too large, vitrification tends to be unstable. Moreover, there exists a tendency for visible region transmittance | permeability to fall.

R ₂ O (R is at least one selected from Li, Na, and K) is a component that enhances the stability of vitrification. In addition, there is an effect that the chain P ₂ O ₅ network is cut to increase the oxygen coordination number of Cu ions. Since the near-infrared absorption characteristics of Cu ions increase according to the oxygen coordination number, the light transmittance in the near-infrared region can be easily reduced by containing R ₂ O. However, R ₂ O is a component that remarkably increases the thermal expansion coefficient and lowers the weather resistance. Furthermore, when there is too much the content, an alkali phosphoric acid type crystal | crystallization will become easy to precipitate. In view of the above, the content of R ₂ O is 0.1 to 14%, preferably 1 to 14%, 1.5 to 12%, 2 to 10%, and particularly preferably 2 to 8%.

The preferable range of the content of each component of R ₂ O is as follows.

Among R ₂ O, Na ₂ O is a particularly effective component for vitrification stability. The content of Na ₂ O is preferably 0.1 to 14%, 1 to 14%, 2 to 12%, particularly 5 to 9%. If the Na ₂ O content is too small, the above effect is difficult to obtain. On the other hand, when the content of Na 2 _O is too large, sodium phosphate crystals are precipitated, rather tends to vitrification tends to be unstable. In addition, the weather resistance tends to decrease.

Li ₂ O and K ₂ O have the effect of increasing the meltability and lowering the melting temperature, but on the other hand, they are components that destabilize vitrification and greatly reduce the weather resistance. Therefore, it is preferable that the contents of Li ₂ O and K ₂ O are 0 to 7% each, 0 to 5% each, and particularly not substantially contained. In the present specification, “substantially not containing” means not intentionally containing as a raw material, and does not exclude inevitable impurities. More objectively, it means less than 0.1%.

_{Incidentally, P 2 O 5 / R 2} O ( mass ratio) 9.2 or more, and particularly preferably 10 or more. In this way, precipitation of alkali phosphate crystals can be suppressed.

  R′O (R ′ is at least one selected from Mg, Ca, Sr, Ba, and Zn) is a component that stabilizes vitrification and suppresses phase separation. It also has the effect of improving weather resistance. The content of R′O is 1.5 to 20%, and particularly preferably 2 to 12%. If the content of R′O is too small, it is difficult to obtain the above effect. On the other hand, when the content of R′O is too large, vitrification tends to be unstable.

  The preferred range of the content of each component of R′O is as follows.

  Among R'O, MgO is a particularly effective component for improving the weather resistance. The content of MgO is preferably 1.5 to 20%, 2 to 15%, particularly 4 to 9%. If the MgO content is too small, the above effect is difficult to obtain. On the other hand, if the content of MgO is too large, magnesium phosphate crystals are precipitated and the vitrification tends to be unstable.

  CaO, SrO, BaO, and ZnO are effective for stabilizing vitrification, but if their content is too large, vitrification tends to be unstable. Therefore, the content of these components is preferably 0 to 10%, particularly preferably 0 to 5%.

  CuO is an essential component for absorbing near infrared rays. The CuO content is 1 to 15%, preferably 1 to 10%, particularly preferably 3 to 9%. When there is too little content of CuO, it will become difficult to obtain a desired near-infrared absorption characteristic. On the other hand, when there is too much content of CuO, it exists in the tendency for the light transmittance of an ultraviolet-visible range to fall. Also, vitrification tends to be unstable. The near-infrared absorption amount of the near-infrared absorption filter glass depends on the CuO content and the glass thickness. Therefore, it is preferable to appropriately adjust the CuO content in accordance with the thickness of the near infrared absorption filter glass. For example, in order to achieve a desired near infrared absorption characteristic while reducing the thickness of the glass, it is preferable to increase the content of CuO.

  In addition to the above components, the glass for near infrared absorption filter of the present invention may contain the following components.

CeO ₂ and Sb ₂ O ₃ have the effect of suppressing the reduction of Cu ²⁺ ions and improving the near-infrared absorption characteristics. However, when there is too much content of these components, there exists a tendency for vitrification to become unstable. Therefore, it is preferable that the content of CeO ₂ and Sb ₂ O ₃ is 0 to 0.5%, 0 to 0.3%, particularly not substantially contained in total.

Nb ₂ O ₅ is a component that improves weather resistance. The content of Nb ₂ O ₅ is preferably 0 to 3%, particularly preferably 0 to 2%. When the content of Nb ₂ O ₅ is too large, there is a tendency that the melting temperature becomes higher meltability decreases. As a result, Cu ²⁺ ions are easily reduced, making it difficult to obtain desired spectral characteristics.

Y ₂ O ₃ , La ₂ O ₃ and Ta ₂ O ₅ are components that stabilize vitrification. The contents of Y ₂ O ₃ , La ₂ O ₃ and Ta ₂ O ₅ are each preferably 0 to 3%, particularly preferably 0 to 2%. When Y ₂ O _3, the content of _La 2 _{O 3} and _Ta 2 _{O 5} is too large, it tends to be devitrified during molding. In addition, the refractive index increases, surface reflection increases, and the light transmittance in the visible range tends to decrease.

B ₂ O ₃ is a component that makes vitrification unstable, and in order to reduce the visible transmittance, its content is preferably 3% or less, 2% or less, and particularly preferably 0.5% or less.

TiO ₂ , WO ₃ , MnO ₂ , CeO ₂ , Cr ₂ O ₃ and NiO are components that significantly reduce the light transmittance in the visible range. Therefore, it is preferable that the content of these components is 1% or less, particularly not substantially contained.

Bi ₂ O ₃ is preferably not substantially contained since Bi ₂ O ₃ reduces Cu ions so that the glass exhibits a metallic color and as a result tends to adversely affect the spectral characteristics.

Nd ₂ O ₃ and V ₂ O ₅ are preferably not substantially contained because they adversely affect the spectral characteristics. Considering the influence on the human body, the Cl component is preferably not substantially contained. Further, SnO, since _SnO 2, Ag ₂ O is capable of affecting the valence of Cu element is preferably not substantially contained.

Since Fe ₂ O ₃ absorbs visible light (for example, 500 nm), its content is preferably 0.01% or less.

Since Dy ₂ O ₃ and Ho ₂ O ₃ lead to an increase in raw material costs, it is preferable that they are not substantially contained.

Note that α-rays are emitted from the glass when a large amount of U and Th components are contained as impurities in the raw material. For this reason, in applications of the visibility correction filter and the color adjustment filter, there is a possibility of causing troubles in CCD and CMOS signals due to α rays. Therefore, it is preferable that the contents of U and Th in the near-infrared absorption filter glass of the present invention are 1 ppm or less, 100 ppb or less, particularly 20 ppb or less, respectively. Further, the α dose emitted from the near infrared absorption filter glass of the present invention is preferably 1.0 c / cm ² · h or less.

The thermal expansion coefficient in the range of 30 to 300 ° C. of the near infrared absorption filter glass of the present invention is 110 × 10 ⁻⁷ / ° C. or less, 105 × 10 ⁻⁷ / ° C. or less, particularly 100 × 10 ⁻⁷ / ° C. or less. It is preferable. If the thermal expansion coefficient is too large, cracks and cracks are likely to occur during molding.

  The crystal precipitation temperature of the glass for near-infrared absorption filter of the present invention is preferably 1300 ° C. or lower, particularly 1250 ° C. or lower. If the crystal precipitation temperature is too high, the stability of vitrification tends to decrease. In addition, since the melting temperature needs to be increased, Cu ions are reduced, the near-infrared absorption characteristics are lowered, and the light transmittance in the visible region is easily lowered.

The near-infrared absorption filter glass of the present invention can sufficiently cut light in the near-infrared region while maintaining high light transmittance in the visible region. Specifically, the light transmittance at a wavelength of 1200 nm is 30% or less (further 18% or less) and the light transmittance at a wavelength of 500 nm in a thickness at which the wavelength λ ₅₀ having a light transmittance of 50% is 615 nm. Is preferably 84% or more (more preferably 86% or more).

  The thickness of the near-infrared absorption filter made of the near-infrared absorption filter glass of the present invention is preferably 0.1 to 1 mm, particularly preferably 0.3 to 0.9 mm. If the thickness is too small, it tends to break. On the other hand, if the thickness is too large, it tends to be difficult to reduce the thickness and weight of the optical device.

  The near-infrared absorption filter glass of the present invention can be produced as follows.

First, a raw material batch is prepared so as to have a desired composition. Next, the raw material batch is heated to obtain molten glass. The melting temperature is preferably 1100 to 1350 ° C, more preferably 1100 to 1300 ° C, and further preferably 1100 to 1250 ° 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 ²⁺ ions are easily reduced, making it difficult to obtain desired spectral characteristics.

  The molten glass is molded and slowly cooled, and then subjected to post-processing such as cutting and polishing as necessary to obtain the near-infrared absorption filter glass of the present invention. Here, by adopting a method of directly forming molten glass (for example, a downdraw method, a rollout method, a direct press method, a float method, etc.) or a method of stretching a base glass while heating (redraw method), It is possible to efficiently produce a glass for a near infrared absorption filter having a small thickness. As described above, the glass for near-infrared absorption filter of the present invention has a low coefficient of thermal expansion, so that cracks and cracks can be suppressed even if molded by the above method.

  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 10) and comparative examples (Nos. 11 to 14) of the present invention.

  Each sample was produced as follows. First, the raw material batch prepared so that it might become the glass composition of a table | surface was thrown into the platinum crucible, and it fuse | melted so that it might become homogeneous at 1200-1300 degreeC. As the raw material, metaphosphate, oxide, sulfate, nitrate, carbonate and the like were used. Next, the molten glass was poured out on the carbon plate, cooled and solidified, and then annealed to prepare a sample.

  The obtained sample was measured or evaluated for crystal precipitation temperature, light transmittance, thermal expansion coefficient, and weather resistance. The results are shown in Tables 1 and 2. No. The light transmittance curve of the sample No. 3 is shown in FIG.

  The crystal precipitation temperature was measured as follows. A 50 g sample was heated in a platinum crucible to form a melt, and held in the range of 1000 to 1350 ° C. in increments of 50 ° C. for 18 hours. Thereafter, the glass melt was poured onto the carbon plate, and the temperature at which crystals were observed was defined as the crystal precipitation temperature.

  The light transmittance was measured as follows. The sample was cut into a size of 25 mm × 30 mm, and both surfaces were mirror-polished so as to have the thickness shown in the table. About the sample after a process, the light transmittance in each wavelength was measured using the spectroscopic analyzer (Shimadzu UV3100).

  The thermal expansion coefficient was measured using a dilatometer in the range of 30 to 300 ° C.

  The weather resistance was determined by an unsaturated pressure cooker test. Specifically, a sample surface having a size of 25 mm × 30 mm × 0.5 mm and mirror-polished on both sides is prepared, and the sample surface is left in an environment of a temperature of 120 ° C. and a humidity of 80% for 8 hours. Was observed. “A” indicates that no change was observed on the sample surface by visual observation and microscopic observation (× 100), “B” indicates that no change was observed in the sample surface by visual observation, but no change was observed by microscopic observation. The sample whose change on the surface of the sample was confirmed visually was evaluated as “C”.

As apparent from Table 1 and FIG. Samples 1 to 10 had desired spectral characteristics and a low coefficient of thermal expansion of 100 × 10 ⁻⁷ / ° C. or less and good weather resistance. On the other hand, as is apparent from Table 2, the comparative example No. Samples 11 and 13 had a heterogeneous layer formed on the surface in the weather resistance test, and were evaluated as C. No. Sample 11 had a high coefficient of thermal expansion of 150 × 10 ⁻⁷ / ° C. No. Samples 12 and 14 did not vitrify.

Claims (8)

By _{mass%, P 2 O 5 65~80%} , SiO 2 1~10%, Al 2 O 3 7~25%, R 2 O 0.1~14% (R is selected from Li, Na and K At least one), R′O 1.5-20% (R is at least one selected from Mg, Ca, Sr, Ba and Zn), MgO 1.5-20%, CuO 1-15% and near infrared absorption filter glass, which is a _P 2 _O 5 _/ SiO 2 _10~80 mass ratio. The glass for near-infrared absorption filters according to claim 1, wherein P ₂ O ₅ / R ₂ O is 9.2 or more by mass ratio. By _mass%, Cr _{2 O} 3 1% or less, and near infrared absorption filter glass of claim 1 or 2, characterized in that NiO is 1% or less. The thermal expansion coefficient in the range of 30-300 degreeC is 110x10 < ^-7 > / degrees C or less, The glass for near-infrared absorption filters as described in any one of Claims 1-3 characterized by the above-mentioned.   The glass for near-infrared absorption filters according to any one of claims 1 to 4, wherein the crystal precipitation temperature is 1300 ° C or lower. The light transmittance at a wavelength of 1200 nm is 30% or less and the light transmittance at a wavelength of 500 nm is 84% or more at a thickness where the wavelength λ ₅₀ is 50% and the wavelength λ ₅₀ is 615 nm. Item 7. The near infrared absorption filter glass according to any one of Items 1 to 6.   A near-infrared absorption filter comprising the glass for a near-infrared absorption filter according to any one of claims 1 to 6.   The near-infrared absorption filter according to claim 7, wherein the thickness is 0.1 to 1 mm.