JP2017014044A - Near infrared absorbing glass and filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a near infrared absorbing glass having excellent weather resistance and excellent bending strength, and a near infrared absorbing filter composed of the glass.SOLUTION: There is provided the near infrared absorbing glass which contains, by cation %, Pof 18 to 41%, Alof 4 to 22%, Mg, Ca, Srand Znof 8% or more in total, Naof 3 to 13%, Bof 3% or less, Cuof over 0% and 4.7% or less, and by anion %, Oof over 60% and 82% or less and Fof 18% or more and less than 40% and which has a molar ratio of the content of Oto the content of P, O/Pof 3.50 or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a copper-containing fluorophosphate glass and a filter for correcting color sensitivity of a semiconductor image sensor.

  As the near-infrared absorbing glass, a copper-containing phosphate glass has been used for a long time. However, phosphate glass has insufficient weather resistance and has a problem that it cannot withstand long-term use.

  In order to improve the weather resistance, copper-containing fluorophosphate glass has been developed and put into practice in place of phosphate glass. As such glass, there exists glass as described in patent document 1, for example.

JP 2004-83290 A

  In recent years, with the miniaturization of digital cameras and the widespread use of camera-equipped mobile phones, high-pixel and small-size imaging systems have been required. All parts such as lenses, optical filters and packages are becoming smaller and thinner. Near-infrared absorption filters are also becoming thinner, and glass for thin plates containing high concentrations of copper is required.

  However, the conventional near-infrared absorption filter made of fluorophosphate glass has excellent weather resistance, but with a thin plate having a thickness of 0.3 mm or less, there is a concern that the glass breaks during processing or cracks during a drop test. Yes.

  An object of the present invention is to solve the above-mentioned problems and to provide a near-infrared absorbing glass having excellent weather resistance and excellent bending strength, and a near-infrared absorbing filter made of this glass.

  As a result of intensive studies to achieve the above object, the present inventors have completed the present invention.

That is, the gist of the present invention is as follows.
[1] In cation% display,
P ⁵⁺ 18-41%,
Al ³⁺ 4-22%,
8% or more in total of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Zn ²⁺
3-13% Na ⁺
B ³⁺ is 3% or less,
Cu ²⁺ exceeds 0% and is 4.7% or less,
Anion% display
O ^2- exceeds 60% and is 82% or less,
F ⁻ is 18% or more and less than 40%,
Including
The molar ratio of the content of ^{O 2-} to the content of P ^{5+ O} 2- ^{/ P 5+} is 3.50 or more,
Is near infrared absorbing glass.

[2] A fluorophosphate glass containing Cu ²⁺ , wherein the O ²⁻ content is more than 60 anion% and is 82 anion% or less, and the F ⁻ content is 18 anion% or more and less than 40 anion%. Near-infrared absorbing glass having a bending strength of 50 MPa or more.

[3] A near-infrared absorbing filter comprising the near-infrared absorbing glass according to [1] or [2].

  ADVANTAGE OF THE INVENTION According to this invention, the near-infrared absorption glass which has the outstanding weather resistance and the outstanding bending strength, and the near-infrared absorption filter which consists of this glass can be provided.

1, for a glass of the glass and the comparative examples of the present embodiment, the horizontal axis F ^- taking the content of a graph plotting on the vertical axis bending strength.

  Hereinafter, modes for carrying out the present invention (hereinafter simply referred to as “embodiments”) will be described in detail. The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be implemented with appropriate modifications within the scope of the gist thereof.

1st embodiment 1st embodiment is a cation% display,
P ⁵⁺ 18-41%,
Al ³⁺ 4-22%,
8% or more in total of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Zn ²⁺
3-13% Na ⁺
B ³⁺ is 3% or less,
Cu ²⁺ exceeds 0% and is 4.7% or less,
Anion% display
O ^2- exceeds 60% and is 82% or less,
F ⁻ is 18% or more and less than 40%,
Including
The molar ratio of the content of ^{O 2-} to the content of P ^{5+ O} 2- ^{/ P 5+} is 3.50 or more,
It is a near infrared ray absorbing glass.

  When an imaging device containing a filter made of a thin near-infrared absorbing glass is dropped, the glass bends due to the impact of dropping. If the deflection of the glass is large, the glass will break. In order to prevent breakage of the glass due to bending, it is necessary to improve the bending strength of the glass.

  According to the glass of the first embodiment, it is possible to absorb near infrared rays and obtain a large bending strength.

1, F of cationic% on the horizontal axis ^- the content of bending the vertical axis represents the intensity, the glasses of Comparative Examples and each of the glass of the present embodiment, F ^- plotting the content and bending strength of It is a thing.

As is clear from FIG. 1, the glass of the comparative example having an F ⁻ content of 40 anion% has a bending strength lower than 50 MPa, whereas the bending of each glass having an F ⁻ content of less than 40 anion%. The strength is greater than 50 MPa.

Thus, by adjusting the F ⁻ content of the fluorophosphate glass, a glass having a bending strength of 50 MPa or more can be produced.

  Hereinafter, the composition of the glass according to the first embodiment will be described in detail. Unless otherwise specified, the cation component of the glass, that is, the content of the cation component, the total content is expressed in cation%, and the anion component, that is, the anion. The component content and total content are expressed in% anion.

In this specification, the cation% display, that is, the cation% display refers to a mole percentage when the total content of all cation components except Sb ³⁺ and Ce ⁴⁺ is 100%. The total content refers to the total amount of the contents of a plurality of types of cation components (including the case where the content is 0%). The cation ratio refers to the ratio (ratio) of the content of cation components (including the total content of plural types of cation components) in cation% display.

About content of Sb3 ⁺ , Ce4 ^+, the molar content with respect to 100 cation% shall be each displayed as a percentage. Such a display is referred to as an extra display.

The valence of the cation component (for example, the valence of P ⁵⁺ is +5, the valence of Al ³⁺ is ⁺³ , and the valence of Mg ²⁺ is +2) is a value determined by custom, and P, Al, Mg as glass components Is expressed as P ₂ O ₅ , Al ₂ O ₃ , MgO when expressed on an oxide basis, and similar to AlF ₃ and MgF ₂ when expressed on a fluoride basis as Al and Mg It is. Therefore, when analyzing a glass composition, it is not necessary to analyze to the valence of a cation component.

  The anion% display, that is, the anion% display refers to a mole percentage when the total content of all anion components is 100%. Further, the total content refers to the total content of a plurality of types of anion components (including the case where the content is 0%).

In addition, the valence of the anion component (for example, the valence of O ²⁻ is −2) is also a value determined by customs. As described above, the glass component on the oxide basis is, for example, P ₂ O ₅ , Al ₂ O _3. , MgO, or the glass component on the basis of fluoride, for example, AlF ₃ , MgF ₂ . Therefore, when analyzing a glass composition, it is not necessary to analyze to the valence of an anion component.

  The glass composition of the glass according to the present embodiment can be quantified by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) or ion chromatography. The analysis value obtained by ICP-AES may include a measurement error of about ± 5% of the analysis value, for example. In the present specification and the present invention, the content of the glass component is 0% or does not contain or is not introduced, which means that this component is not substantially contained. It means that it is about the impurity level or less.

[Cation component]
P ⁵⁺ is a basic component of fluorophosphate glass and an important component that brings about absorption in the infrared region. If the content of P ⁵⁺ is less than 18%, the color correction function is deteriorated and greenish. When the content of P ⁵⁺ exceeds 41%, weather resistance and devitrification resistance deteriorate. Therefore, the content of P ⁵⁺ is 18 to 41%. From the viewpoint of maintaining good devitrification resistance while maintaining the color correction function, the preferred lower limit of the P ⁵⁺ content is 20%, the more preferred lower limit is 23%, the still more preferred lower limit is 24%, and the more preferred lower limit is 25. %. In order to maintain the weather resistance and devitrification resistance of the glass well, the preferable upper limit of the content of P ⁵⁺ is 38%, the more preferable upper limit is 36%, the more preferable upper limit is 34%, and the more preferable upper limit is 33%. A more preferred upper limit is 32%.

Al ³⁺ is an important component that improves the devitrification resistance of fluorophosphate glass. If the content of Al ³⁺ is less than 4%, the devitrification resistance is lowered, the liquidus temperature becomes high, and it becomes difficult to melt and form high-quality glass. Even if the content of Al ³⁺ exceeds 22%, the devitrification resistance deteriorates. Therefore, the content of Al ³⁺ is limited to 4-22%.

From the viewpoint of maintaining good weather resistance and devitrification resistance, the preferable lower limit of the content of Al ³⁺ is 6%, the more preferable lower limit is 8%, and the further preferable lower limit is 10%. In order to maintain good devitrification resistance, the preferable upper limit of the content of Al ³⁺ is 20%, the more preferable upper limit is 18%, and the further preferable upper limit is 16%.

^{Mg 2+, Ca 2+, Sr 2+} , Zn 2+ in the fluorophosphate glass, glass devitrification resistance, durability, is a useful component for improving the processability. When the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Zn ²⁺ (Mg ²⁺ + Ca ²⁺ + Sr ²⁺ + Zn ²⁺ ) is less than 8%, the devitrification resistance and durability of the glass are lowered. Therefore, the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Zn ²⁺ is 8% or more. The preferred lower limit of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Zn ²⁺ is 12%, more preferred lower limit is 14%, and more preferred lower limit is to maintain good devitrification resistance, durability and workability. 15%.

In order to maintain the devitrification resistance of the glass well, the preferable upper limit of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Zn ²⁺ is 53%, and 45%, 40%, 35%, 30 %, 25%, 23% and 21% are preferable in this order.

From the ^standpoint of obtaining the effects and effects of Mg ²⁺ , the preferable lower limit of the content of Mg ²⁺ is 0.5%, and further preferably 1%, 1.5%, 2%, and 3%. In order to maintain good devitrification resistance, weather resistance, and workability, the upper limit of the Mg ²⁺ content is preferably 7%, and more preferably 6%, 5%, and 4% in this order.

Effect of the ^{Ca 2+,} from above to obtain the effect, the preferred lower limit of the content of ^{Ca 2+} is 1%, even 2%, 3%, 4%, preferably in the order of 5%. In order to maintain good devitrification resistance, weather resistance, and workability, the upper limit of the Ca ²⁺ content is preferably 12%, and more preferably 11%, 10%, and 9% in this order.

The action of the ^{Sr 2+,} from above to obtain the effect, the preferred lower limit of the content of ^{Sr 2+} is 1%, even 2%, preferably in the order of 3%. In order to maintain good devitrification resistance, weather resistance, and workability, the upper limit of the content of Sr ²⁺ is preferably 10%, and more preferably 8%, 7%, and 6% in this order.

The Zn ²⁺ is preferably contained for improving devitrification resistance. However, from the viewpoint of maintaining good weather resistance and devitrification resistance, the preferable range of the Zn ²⁺ content is more than 0% and 8% or less. From the viewpoint of maintaining good devitrification resistance, the preferable lower limit of the Zn ²⁺ content is 1%, and further preferably 2% and 3% in this order. From the viewpoint of maintaining good weather resistance and devitrification resistance, the upper limit of the Zn ²⁺ content is preferably 7%, more preferably 6% and 5% in this order.

Effect of Ba ^2+, from above to obtain the effect, the preferred lower limit of the content of ^{Ba 2+} is 1%, even 2%, preferably in the order of 3%. In order to maintain good devitrification resistance, weather resistance, and workability, the preferable upper limit of the Ba ²⁺ content is 7%, and further in the order of 6% and 5%.

Na ⁺ is a useful component that improves the devitrification resistance of the glass. If the Na ⁺ content is less than 3%, the effect is small, and if it exceeds 13%, the durability and workability of the glass deteriorate. Therefore, the Na ⁺ content is 3 to 13%. From the viewpoint of maintaining good devitrification resistance, a preferable lower limit of the content of Na ⁺ is 4%, and a more preferable lower limit is 5%. In order to maintain the durability and workability satisfactorily, the upper limit of the Na ⁺ content is preferably 11%, and more preferably 10%, 9%, and 8% in this order.

B ³⁺ can be appropriately used for the purpose of improving devitrification resistance, adjusting the glass viscosity, adjusting the transmittance, and clarifying. However, if the content of B ³⁺ exceeds 3%, the volatility of the molten glass becomes remarkable, and the characteristics of the glass greatly change during the glass production process, or the homogeneity of the glass decreases. Therefore, the content of B ³⁺ is 3% or less. A preferred range for the content of B ³⁺ is 2% or less, a more preferred range is 1% or less, a further preferred range is 0.5% or less, a still more preferred range is 0.1% or less, and it may be 0%.

Li ⁺ is a useful component that improves the devitrification resistance of the glass, but if it is less than 11%, there is no effect, and if it exceeds 40%, the durability and workability of the glass deteriorate. Therefore, the content of Li ⁺ is preferably 11 to 40%. From the viewpoint of improving devitrification resistance, the preferable lower limit of the content of Li ⁺ is 12%, and further preferably 15%, 18%, and 20% in this order. From the standpoint of maintaining good weather resistance and devitrification resistance, the upper limit of the Li ⁺ content is preferably 35%, more preferably 32%, 30%, 28%, and 27% in this order.

Cu ²⁺ is a component that plays an important role in light absorption characteristics. In order to obtain a near infrared absorption function, the content of Cu ²⁺ is more than 0%. On the other hand, when the content of Cu ²⁺ exceeds 4.7%, the devitrification resistance decreases, and it becomes difficult to produce high-quality glass. Therefore, the content of Cu ²⁺ is more than 0% and not more than 4.7%. In order to cope with the thinning of the filter, the preferable lower limit of the Cu ²⁺ content is 1.0%, and further preferably 1.5% and 2.0% in this order. From the viewpoint of maintaining good devitrification resistance, the upper limit of the Cu ²⁺ content is preferably 4.5%, more preferably 4.0%, 3.5%, and 3.0% in this order.

K ⁺ , Zr ⁴⁺ , La ³⁺ , Gd ³⁺ , Y ³⁺ , Si ⁴⁺ can be appropriately used for the purpose of improving devitrification resistance, adjusting the glass viscosity, adjusting the transmittance, and clarifying. At least one cation component selected from these groups can be added in a total amount of less than 5%. The total content of K ⁺ , Zr ⁴⁺ , La ³⁺ , Gd ³⁺ , Y ³⁺ and Si ⁴⁺ is preferably 4% or less, more preferably 2% or less, still more preferably 1% or less, and even more preferably 0.5%. It is as follows. The total content of K ⁺ , Zr ⁴⁺ , La ³⁺ , Gd ³⁺ , Y ³⁺ and Si ⁴⁺ can also be 0%.

Sb ³⁺ and Ce ⁴⁺ can be added as optional components. These components are effective components for improving the transmittance of the short wavelength region of glass, particularly the wavelength of 400 nm.

A preferable range of the content of Sb ³⁺ is 0 to 1%. Here, the display of the content of Sb ³⁺ is an external display by cation%. From the viewpoint of obtaining the above-described functions and effects, the preferred lower limit of the Sb ³⁺ content is 0.001%. The upper limit with preferable content of Sb3 ⁺ is 0.1%.

A preferable range of the content of Ce ⁴⁺ is 0 to 1%. Here, the display of the content of Ce ⁴⁺ is an external display by cation%. From the viewpoint of obtaining the above-described functions and effects, the preferable lower limit of the Ce ⁴⁺ content is 0.001%. A preferable upper limit of the content of Ce ⁴⁺ is 0.1%.

When Sb ³⁺ and Ce ⁴⁺ are simultaneously contained, the total content of Sb ³⁺ and Ce ⁴⁺ is preferably 1% or less. Among Sb ³⁺ and Ce ⁴⁺ , Sb ³⁺ is particularly effective in improving the transmittance in the short wavelength region, and it is preferable to contain only Sb ³⁺ from the viewpoint of obtaining a required purpose. Note that by introducing Sb ³⁺ (for example, Sb ₂ O ₃ ), it is possible to prevent a decrease in transmittance in the vicinity of a wavelength of 400 nm even if impurities such as iron are mixed in the glass raw material.

[About anion components]
O ²⁻ is a major anion component and is a component that affects the bending strength of glass. When the content of O ²⁻ is 60% or less, the bending strength of the glass decreases, and the filter is easily broken when it is thinned. When the content of O ²⁻ is more than 82%, the weather resistance is lowered. Therefore, the content of O ²⁻ exceeds 60% and is 82% or less. In order to maintain the bending strength of the glass satisfactorily, the preferable lower limit of the content of O ²⁻ is 61%, and further preferably in the order of 61.5%, 62%, 62.5%, and 63%. From the standpoint of maintaining good weather resistance, the upper limit of the content of O ²⁻ is preferably 80%, and more preferably 78%, 76%, and 75% in this order.

F ⁻ is an important anion component that lowers the melting point of the glass and improves the weather resistance, and is a component that affects the bending strength of the glass. When the content of F ⁻ is less than 18%, it becomes difficult to obtain the above-described effect. When the content of F ⁻ is 40% or more, the bending strength of the glass decreases, and it becomes difficult to maintain sufficient strength when the filter is thinned. Therefore, the content of F ⁻ is 18% or more and less than 40%.

In order to increase the bending strength of the glass, the preferable upper limit of the content of F ⁻ is 39%, the more preferable upper limit is 38.5%, the further preferable upper limit is 38%, and the more preferable upper limit is 37.5%. A preferred upper limit is 37%. From the standpoint of maintaining good weather resistance, the lower limit of the content of F ⁻ is preferably 20%, and more preferably 22%, 24%, and 25% in this order.

As an anion component, Cl ⁻ , Br ⁻ and I ⁻ may be contained. In that case, the total content of Cl ⁻ , Br ⁻ and I ⁻ is preferably 0 to 1%. The total content of Cl ⁻ , Br ⁻ and I ⁻ may be 0%.

[Molar ratio O ²⁻ / P ⁵⁺ ]
As a raw material for fluorophosphate glass, phosphate is generally used. Further, in order to increase the introduction amount of F ⁻ as an anionic component, a metaphosphate having a ratio of the number of oxygen O ²⁻ atoms to phosphorus P 5 ⁺ 1 atoms, that is, a molar ratio O ²⁻ / P ⁵⁺ of 3 is used. ing. When glass is melted using metaphosphate, it is considered that metaphosphoric acid derived from the raw material reacts with fluorine to generate highly volatile phosphoryl POF ₃ . On the other hand, when the molar ratio O ²⁻ / P ⁵⁺ of the content of O ^{2− to} the content of P ^{5+ in} the molten glass is adjusted to 3.50 or more and controlled, the amount of volatile components generated is greatly reduced. it can. This is a phosphoric acid present in the molten glass ^than metaphosphoric acid ratio of ^O number ² atoms to ^{P 5+} 1 atom is ^3, the ratio of the number of ^{O 2} atoms to ^{P 5+} 1 atom 7/2 That is, it is considered that the diphosphoric acid which is 3.50 is more stable. By setting the molar ratio O ²⁻ / P ⁵⁺ of the content of O ^{2− to} the content of P ⁵⁺ in the fluorophosphate glass to be 3.50 or more, generation of volatile components can be suppressed. As a result, the reactivity of the molten glass is also suppressed, and the erodibility can be greatly reduced.

For the above reasons, the molar ratio O ²⁻ / P ⁵⁺ is 3.50 or more. The preferable lower limit of the molar ratio O ²⁻ / P ⁵⁺ is 3.55, and further preferable in the order of 3.60, 3.65, 3.70, and 3.75. The upper limit of the molar ratio O ²⁻ / P ⁵⁺ is naturally determined from the balance with other components.

In addition, the molar ratio O ²⁻ / P ⁵⁺ can be calculated from the glass composition represented by cation% and anion% by the following calculation.
For each cation component, the value obtained by multiplying the content expressed as cation% by the valence of the cation component is totaled for all cation components. The absolute value of this total value is Σ +.
For each anion component, the value obtained by multiplying the content expressed in% anion by the valence of the anion component is totaled for all anion components. The absolute value of this total value is Σ−.
Since glass is electrically neutral, for example, the content of all anionic components is multiplied by Σ + / Σ− so that the ratio of Σ + to Σ− is 1: 1.
Next, the content of each component is normalized so that the total of the content of all cation components and the total content of all anion components multiplied by Σ + / Σ− is 100.
The content of each component obtained by normalization is a value expressed in atomic%. A value obtained by dividing the content of O ²⁻ in atomic% by the content of P ⁵⁺ is the molar ratio O ²⁻ / P ⁵⁺ .

[Substances preferably not contained]
It is preferable that the glass does not substantially contain a substance having a large environmental load such as arsenic, lead, cadmium, uranium, and thorium.

[Bending strength]
The bending strength of glass is the three-point bending strength defined in JIS R1601. Hereinafter, the bending strength means that measured by the method defined in JIS R1601. Note that the measurement sample has a flat plate shape, and two main surfaces facing each other are optically polished surfaces, and four end surfaces are surfaces subjected to sanding using No. 1000 abrasive grains. The ridge formed by the main surface and the end surface, and the ridge formed by the end surfaces are chamfered by No. 800.

  From the viewpoint of maintaining the strength when the glass is thinned, a glass having a bending strength of 50 MPa or more is preferable. The preferable lower limit of the bending strength is 51 MPa, and the more preferable lower limit is 52 MPa. The upper limit of bending strength is determined by the glass composition. As a guide, the upper limit of bending strength is 70 MPa. If the bending strength is excessively increased, other characteristics and properties such as weather resistance and devitrification resistance may be deteriorated. Therefore, the bending strength is preferably 66 MPa or less, more preferably 63 MPa or less, and further preferably 62 MPa or less.

Second embodiment The second embodiment is a ^{fluorophosphate} that contains Cu ²⁺ , the content of O ²⁻ exceeds 60 anion% and is 82 anion% or less, ^and the content of F ⁻ is 18 anion% or more and less than 40 anion%. It is glass and is a near infrared ray absorbing glass having a bending strength of 50 MPa or more according to JIS R1601.

  From the viewpoint of maintaining the strength when the glass is thinned, the preferable lower limit of the bending strength is 51 MPa, and the more preferable lower limit is 52 MPa. As a guide, the upper limit of bending strength is 70 MPa. If the bending strength is excessively increased, other characteristics and properties such as weather resistance and devitrification resistance may be deteriorated. Therefore, the bending strength is preferably 66 MPa or less, more preferably 63 MPa or less, and further preferably 62 MPa or less.

  The preferable aspect in 2nd embodiment is the glass which concerns on 1st embodiment, and is the glass which concerns on 2nd embodiment.

  The glass according to the first embodiment and the glass according to the second embodiment are suitable as materials for optical filters for correcting color sensitivity of semiconductor image sensors such as CMOS sensors and CCDs.

[Weatherability]
In order to withstand long-term use, excellent weather resistance is required. If the weather resistance is low, the glass surface will be fogged, and it will not be able to withstand applications such as optical filters.

  Both the glass according to the first embodiment and the glass according to the second embodiment have excellent transmittance characteristics and weather resistance. The weather resistance is determined by holding the optically polished glass sample in a high-temperature and high-humidity tank at 80 ° C. and 90% relative humidity for 1000 hours, and then visually observing the burned state of the optically polished surface of the sample. As a result, good weather resistance that can sufficiently withstand long-term use can be confirmed if no burnt state is observed. It has been confirmed that the glass according to the first embodiment and the glass according to the second embodiment are both not weathered under the above conditions and have good weather resistance.

[Devitrification resistance]
In a glass used for an optical filter or the like, when a crystal is generated in the glass during the manufacturing process, the crystal is scattered by the light transmitted through the glass, and the optical quality is deteriorated. Both the glass according to the first embodiment and the glass according to the second embodiment have the property that crystals are difficult to precipitate during the production process.

[Glass manufacturing method]
An example is given and demonstrated about the manufacturing method of the glass which concerns on 1st embodiment, and the glass which concerns on 2nd embodiment.

  Any of the above glasses can be produced in the same manner as conventional copper-containing fluorophosphate glasses. That is, using raw materials such as phosphates, fluorides, carbonates, nitrates, and oxides as appropriate, the raw materials are weighed and mixed to have a desired composition, and then in a platinum crucible at 800 to 1100 ° C. Melt. Although there is no problem in the melting atmosphere in the air, it is preferable to use an oxygen atmosphere in order to suppress the valence change of Cu, or to bubble oxygen into the molten glass. The glass melting temperature should not be excessively high in order to make a glass having the desired transmittance characteristics.

  The glass in the molten state becomes a homogenized molten glass containing no bubbles by stirring and clarification.

  The molten glass is poured into a mold and molded. Alternatively, the molten glass may be press-molded or roll-molded. The molded glass is placed in an annealing furnace preheated to near the glass transition temperature and slowly cooled to room temperature. After slow cooling, the glass is subjected to known mechanical processing such as slicing, grinding, and polishing to form an optical filter.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

[Examples 1-7]
Compositions shown in Table 1 include Al (PO ₃ ) ₃ , AlF ₃ , Li ₂ CO ₃ , NaF, MgF ₂ , CaF ₂ , SrF ₂ , BaF ₂ , ZnF ₂ , Sb ₂ O ₃ , and CuO as glass raw materials. The 7 types of glass were weighed and mixed, put into a platinum crucible, melted in the atmosphere at 800 ° C. to 1100 ° C., stirred, defoamed and homogenized, and then preheated mold The glass block was molded. The obtained glass block was transferred to an annealing furnace heated to near the glass transition temperature and gradually cooled to room temperature. A test piece was cut out from the obtained glass, and various properties were measured as follows. Examples 1 to 7 are all examples of glass according to the first embodiment and the second embodiment.

[Bending strength]
The bending strength was measured based on JIS R1601.

[Weatherability]
A glass sample that has been optically polished is kept in a high-temperature and high-humidity tank at 80 ° C. and a relative humidity of 90% for 1000 hours, and the glass surface is visually observed for burnt condition. Yes).

[Average linear expansion coefficient]
The average linear expansion coefficient in 100-300 degreeC measured using the thermomechanical analyzer was measured.

[Glass-transition temperature]
Using a thermomechanical analyzer, measurement was performed at a heating rate of 4 ° C./min.

[specific gravity]
Measured by Archimedes method.

  Table 2 shows the composition and characteristics of the anionic components of the glasses of Examples 1 to 7. All the glasses of Examples 1 to 7 had a bending strength of 50 MPa or more and had good weather resistance.

  Next, the glass of Examples 1 to 7 was processed into a flat plate shape, and two opposing flat surfaces were optically polished to produce an optical filter. An optical filter made of glass of Examples 1 to 7 is disposed in front of the light receiving surface of the CMOS image sensor, and an image of the subject is formed on the light receiving surface by an optical system configured using a plurality of lenses. It was confirmed. When the subject was visually observed and the image was compared, the image faithfully reproduced the color of the subject.

  About the glass of Examples 1-7, it was not damaged at the time of the process at the time of thinning glass, and the time of a drop test.

[Comparative example]
Next, in order to obtain a glass having the composition shown in Table 1 as a comparative example, the glass raw materials used in the above examples are weighed and mixed well to prepare the raw materials, which are put into a platinum crucible, After melting, stirring and defoaming and homogenizing at 1300 ° C., it was poured into a preheated mold to form a glass block. The obtained glass block was transferred to an annealing furnace heated to near the glass transition temperature and gradually cooled to room temperature. A test piece was cut out from the obtained glass and the bending strength was measured.

The measurement results are shown in Table 2. The glass of the comparative example has an F ⁻ content of 40 anion%, which is larger than the F ⁻ content of the glasses of Examples 1 to 7, and the bending strength does not reach 50 MPa.

  When this glass was used to produce an optical filter and a drop test was performed, the glass was damaged.

Claims (3)

In cation% display,
P ⁵⁺ 18-41%,
Al ³⁺ 4-22%,
8% or more in total of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Zn ²⁺
3-13% Na ⁺
B ³⁺ is 3% or less,
Cu ²⁺ exceeds 0% and is 4.7% or less,
Anion% display
O ^2- exceeds 60% and is 82% or less,
F ⁻ is 18% or more and less than 40%,
Including
The molar ratio of the content of ^{O 2-} to the content of P ^{5+ O} 2- ^{/ P 5+} is 3.50 or more,
Is near infrared absorbing glass. It is a fluorophosphate glass containing Cu ^2+, having an O ²⁻ content of more than 60 anion% and not more than 82 anion%, and an F ⁻ content of 18 anion% or more and less than 40 anion%, and bending strength according to JIS R1601 Near-infrared absorbing glass having a thickness of 50 MPa or more.   A near-infrared absorbing filter comprising the near-infrared absorbing glass according to claim 1.

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