JP2011132077A - Near-infrared light absorbing glass, near-infrared light absorbing filter, and imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide near-infrared light absorbing glass having excellent weather resistance, excellent transmission characteristics in a visible region, while having few striae and foreign substances, and to provide a near-infrared absorbing filter and an imaging device equipped with the filter. <P>SOLUTION: The near-infrared light absorbing glass includes Cu-containing fluorophosphate glass, which contains 20-45 cation% of P<SP>5+</SP>, 1-25 cation% of Al<SP>3+</SP>, 10-30 cation% of Li<SP>+</SP>, and 0-15 cation% of Na<SP>+</SP>, and 14-50 cation% of the sum of Mg<SP>2+</SP>, Ca<SP>2+</SP>, Sr<SP>2+</SP>and Ba<SP>2+</SP>, and 0.1-10 cation% of Cu<SP>2+</SP>, 0.005-2 cation% of the sum of Ce<SP>4+</SP>and Sb<SP>3+</SP>relative to 100 cation% plus the sum of Ce<SP>4+</SP>and Sb<SP>3+</SP>, 50-75 anion% of O<SP>2-</SP>, 25-50 anion% of F<SP>-</SP>, and 0.001-1 anion% of the sum of Cl<SP>-</SP>, Br<SP>-</SP>and I<SP>-</SP>relative to 100 anion% plus the sum of Cl<SP>-</SP>, Br<SP>-</SP>and I<SP>-</SP>. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a near-infrared light absorbing glass, a near-infrared light absorbing filter using the glass as a material for a color sensitivity correction filter of a semiconductor image sensor, and an imaging device including the filter.

  The spectral sensitivity of semiconductor image sensors such as CCDs and CMOSs used in digital cameras and VTR cameras ranges from the visible range to the near infrared range near 1100 nm. For this reason, a filter that absorbs light in the near infrared region is used to approximate human visual sensitivity. As such a near infrared light absorbing glass, there is a glass in which CuO is added to a phosphate glass. However, the weather resistance is poor, and there is a disadvantage that the glass surface becomes rough or cloudy when exposed to high temperature and high humidity for a long time. .

  In order to solve these problems, near-infrared light absorbing filter glass based on fluorophosphate glass containing fluorine as a main anion component and exhibiting excellent weather resistance has been developed and marketed.

  As this type of glass, for example, CuO-containing fluorophosphate glasses disclosed in Patent Document 1, Patent Document 2, and the like are known.

JP 2004-137100 A JP 2007-099604 A

  However, CuO-containing fluorophosphate glass also has the following problems.

  Fluorophosphate glass containing copper ions has a low melting temperature and is easy to melt, but the viscosity of the glass melt is low and the volatilization of the fluorine component is large. Due to the convection promoted by being, it tends to cause inhomogeneous defects called striae. In particular, when a glass or platinum alloy nozzle made of platinum or platinum alloy is used to avoid contamination of molten glass, the glass melt wets the outer peripheral surface of the nozzle, and the wet glass is altered by volatilization. There was a problem that it was easy to make sense.

  Furthermore, when glass is melted in a platinum or platinum alloy container, the oxidation of the container becomes significant at the boundary between the glass melt surface and the container, and the minute platinum piece or platinum alloy piece peels off and enters the glass. There was a problem that it was easy.

Furthermore, it is desired that the near-infrared light absorbing filter has a high visible light transmittance. In order to increase the transmittance in the visible range, it is necessary that the copper ion is not Cu ⁺ (monovalent) but Cu ²⁺ (bivalent). When the glass melt is in a reduced state, Cu ²⁺ becomes Cu ⁺ , and as a result, the transmittance near a wavelength of 400 nm decreases. When such glass is used as a filter, blue is strongly absorbed. In the case of a digital camera or the like, it is possible to amplify the wavelength at which the light amount is reduced by correcting the electric signal, but there is a disadvantage that the S / N ratio is deteriorated because noise is also amplified thereby.

  The present invention has been made in order to solve the above problems, and has a near infrared light absorbing glass having little striae and foreign matter, excellent weather resistance and excellent transmission characteristics in the visible range, and near infrared light absorption. It aims at providing a filter and an imaging device provided with the said filter.

As a means for solving the above problems, the present invention provides:
(1) In a near-infrared light absorbing glass made of Cu-containing fluorophosphate glass,
The content of P ⁵⁺ is 20 to 45 cation%,
Al ³⁺ content is 1-25 cation%,
Li ⁺ content is 10-30 cation%,
Na ⁺ content 0-15 cation%,
The total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is 14-50 cation%,
Cu ²⁺ content is 0.1 to 10 cation%,
Ce ⁴⁺ and Sb ^{3+ have} an external total content of 0.005 to 2 cation%,
The content of O ²⁻ is 50 to 75 anion%,
The content of F ⁻ is 25-50 anion%,
Cl ⁻ , Br ⁻ and I ^{− have} an outer total content of 0.001 to 1 anion%,
Near infrared light absorbing glass,
⁽²⁾ the molar ratio of the content of ^{O 2-} to the content of ^{P 5+ (O} 2- ^{/ P 5+)} is near-infrared light absorbing glass according to the above item (1) is 3.5 or more,
(3) The near-infrared light absorbing glass according to (1) or (2) above, containing 0.01 to 2 cations of Ce ²⁺ ;
(4) A near-infrared light absorption filter using the near-infrared light absorption glass according to any one of the above items (1) to (3),
(5) An imaging device including the near-infrared light absorption filter according to (4) above and a semiconductor image sensor,
Is to provide.

  According to the present invention, a near-infrared light absorbing glass having little striae and foreign matter, excellent weather resistance and excellent transmission characteristics in the visible range, a near-infrared light absorbing filter, and an imaging device including the filter Can be provided.

  Hereinafter, the present invention will be described in detail.

[Near-infrared absorbing glass]
The near-infrared light absorbing glass is based on fluorophosphate glass and added with Cu ²⁺ having a near-infrared light absorbing action.

  Fluorophosphate glass has the property that when the glass melt flows out from the glass outflow nozzle and is molded, the melt wets the outer peripheral surface of the nozzle, and the wet high temperature glass melt is exposed to the outside air. Deterioration occurs, and the deteriorated melt is mixed into the glass melt newly flowing out from the nozzle, and the problem that the optical homogeneity is lowered due to striae in the formed glass is likely to occur.

By adding Cl ⁻ , Br ⁻ , and I ⁻ to the glass, an effect of suppressing the glass melt from wetting from the nozzle tip to the outer peripheral surface can be obtained. A nozzle made of platinum, a platinum alloy, or a gold or a gold alloy is used as the glass outflow nozzle. However, an oxide film is formed on the nozzle surface, and this film promotes the wetting of the glass melt. . When a glass melt containing Cl ⁻ , Br ⁻ , and I ⁻ touches the oxide film on the nozzle surface, an effect of removing the film is obtained, and as a result, an effect of suppressing the wetting of the glass melt is obtained.

However, Cl ⁻ , Br ⁻ , and I ⁻ reduce Cu ²⁺ and reduce the transmittance near the wavelength of 400 nm, and the glass melt forms platinum, platinum alloy, gold, gold alloy, and the like that constitute the glass manufacturing apparatus. Causes the problem of easy erosion. Ce ²⁺ and Sb ³⁺ have a function of solving such problems.

That is, Ce ²⁺ and Sb ³⁺ have the effect of suppressing the reduction of Cu ²⁺ , preventing a decrease in transmittance near the wavelength of 400 nm, and the effect of suppressing the corrosion of the metal or alloy constituting the glass manufacturing apparatus by the glass melt. .

The present invention is to allow visible light transmission in a predetermined fluorophosphate glass by coexisting Cu ²⁺ , at least one halogen of Cl ⁻ , Br ⁻ and I ⁻ , and at least one additive of Ce ²⁺ and Sb ^3+. Provided is a near-infrared light absorbing glass having excellent optical homogeneity while maintaining a high rate.

That is, the present invention is a near-infrared light absorbing glass made of Cu-containing fluorophosphate glass,
The content of P ⁵⁺ is 20 to 45 cation%,
Al ³⁺ content is 1-25 cation%,
Li ⁺ content is 10-30 cation%,
Na ⁺ content 0-15 cation%,
The total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is 14-50 cation%,
Cu ²⁺ content is 0.1 to 10 cation%,
Ce ⁴⁺ and Sb ^{3+ have} an external total content of 0.005 to 2 cation%,
The content of O ²⁻ is 50 to 75 anion%,
The content of F ⁻ is 25-50 anion%,
Cl ⁻ , Br ⁻ and I ^{− have} an outer total content of 0.001 to 1 anion%,
It is characterized by being.

P ⁵⁺ is a basic component of fluorophosphate glass and a component that brings about absorption of Cu ^{2+ in} the near infrared region. When the content of P ⁵⁺ is less than 20 cation%, the near-infrared light absorption effect tends to decrease, and when it exceeds 45 cation%, weather resistance and devitrification resistance tend to decrease. Therefore, the content of P ⁵⁺ is preferably in the range of 20 to 45 cation%. A more preferable range of the content of P ⁵⁺ is 20 to 40 cations n%, a further preferable range is 23 to 36%, and a more preferable range is 25 to 35 cations%.

Al ³⁺ is a component having an effect of improving devitrification resistance, heat resistance, thermal shock resistance, mechanical strength, and chemical durability. When the content of Al ³⁺ is less than 1 cation%, the above effect tends to decrease, and when it exceeds 25 cation%, devitrification resistance tends to deteriorate. Therefore, the content of Al ³⁺ is preferably in the range of 1 to 25 cation%. A more preferable range of the content of Al ³⁺ is 5 to 23 cation%, a further preferable range is 8 to 23 cation%, a more preferable range is 10 to 22 cation%, and an even more preferable range is 10 to 20 cation%.

Li ⁺ is a component that has the effect of improving the meltability and devitrification resistance of glass and improving the transmittance in the visible region. If the Li ⁺ content is less than 10 cation%, it is difficult to obtain the above effect sufficiently, and if it exceeds 30 cation%, the durability and workability of the glass tend to deteriorate. Therefore, the Li ⁺ content is preferably in the range of 10 to 30 cation%. A more preferable range of the content of Li ⁺ is 15 to 25 cation%.

Na ⁺ is an effective component for improving the meltability and devitrification resistance. In order to obtain the above effect, the Na ⁺ content is preferably 0.1% or more. However, when the content exceeds 15%, the weather resistance, devitrification resistance, and workability tend to be lowered. . Therefore, the Na ⁺ content is preferably in the range of 0.1 to 15%, more preferably in the range of 2 to 13%, still more preferably in the range of 3 to 11%. A range of 10 cation% is more preferable.

Mg ²⁺ and Ca ²⁺ are useful components that improve the devitrification resistance, durability, and workability of the glass. Sr ²⁺ and Ba ²⁺ are useful components that improve the devitrification resistance and meltability of the glass. When the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is less than 14 cation%, the devitrification resistance tends to deteriorate, and even when it exceeds 50 cation%, the devitrification resistance tends to deteriorate. Indicates. Therefore, the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is preferably in the range of 14 to 50 cation%. A more preferable range of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is 14 to 35 cation%, a further preferable range is 14 to 30 cation%, a more preferable range is 16 to 28 cation%, and an even more preferable range. Is 17-27 cation%.

In order to further improve the devitrification resistance, durability, and workability, the Mg ²⁺ content is preferably in the range of 0.1 to 10 cation%, and is preferably in the range of 0.5 to 8 cation%. More preferably, the range is 0.5 to 7 cation%, still more preferably 0.5 to 6 cation%, and even more preferably 1 to 5 cation%. preferable.

For the same reason, the Ca ²⁺ content is preferably in the range of 0.1 to 20 cation%, more preferably in the range of 2 to 15 cation%, and in the range of 3 to 14 cation%. More preferably, it is more preferably in the range of 4 to 12 cation%, and still more preferably in the range of 5 to 11 cation%.

In order to further improve devitrification resistance and meltability, the content of Sr ²⁺ is preferably in the range of 0.1 to 20 cation%, more preferably in the range of 1 to 10 cation%. More preferably, it is in the range of 2-9 cation%, more preferably in the range of 3-8 cation%, still more preferably in the range of 4-8 cation%.

For the same reason, the Ba ²⁺ content is preferably in the range of 0.1 to 20 cation%, more preferably in the range of 1 to 10 cation%, and in the range of 3 to 10 cation%. More preferably, it is more preferably in the range of 4-9 cation%.

Cu ²⁺ has an effect of absorbing near infrared light. When the content of Cu ²⁺ is less than 0.1 cation%, the absorption effect of near infrared light necessary as a near infrared light absorption filter is not sufficient, and when the content exceeds 10 cation%, devitrification resistance Sex worsens. Therefore, the Cu ²⁺ content is set to 0.1 to 10 cation%. The preferable range of the content of Cu ²⁺ is 1 to 10 cation%, the more preferable range is 2 to 7 cation%, and the more preferable range is 3 to 6 cation%.

Ce ²⁺ and Sb ³⁺ suppress the reduction of Cu ²⁺ by Cl ⁻ , Br ⁻ , and I ⁻ , prevent the transmittance from being lowered near 400 nm, and metals such as platinum alloys and gold alloys constituting the glass manufacturing apparatus. Or an effect of suppressing the erosion of the glass melt into an alloy such as a platinum alloy or a gold alloy. When the total content of Ce ²⁺ and Sb ³⁺ is less than 0.01 cation%, it is difficult to sufficiently obtain a transmittance lowering suppression effect near a wavelength of 400 nm and an erosion suppression effect of metals and alloys, and when it exceeds 2 cation%. , Ce ²⁺ , Sb ³⁺ itself increases light absorption in the visible range. Therefore, the total content of Ce ²⁺ and Sb ³⁺ is in the range of 0.005 to 2 cation%. A preferable range of the total content of Ce ²⁺ and Sb ³⁺ is 0.008 to 1 cation%, a more preferable range is 0.008 to 0.1 cation%, a further preferable range is 0.008 to 0.08 cation%, A more preferable range is 0.008 to 0.06 cation%, and an even more preferable range is 0.009 to 0.05 cation%.

Of Ce ²⁺ and Sb ³⁺ , Ce ²⁺ functions to increase the transmittance of blue light, suppresses a decrease in blue transmittance in the visible short wavelength region, and functions to flatten the transmittance in the visible region. Such a function is preferable from the viewpoint of color sensitivity correction of the semiconductor image sensor. Ce is less burdened on the environment than Sb. For reasons such ^becomes, Ce 2+, it is preferable to use the ^{Ce 2+} of ^{Sb 3+.} The preferable range of the content of Ce ²⁺ is 0.005 to 2 cation%. The preferable range of the content of Ce ²⁺ is 0.008 to 1 cation%, the more preferable range is 0.008 to 0.1 cation%, the still more preferable range is 0.008 to 0.08 cation%, and the more preferable range is 0. 0.008 to 0.06 cation%, and an even more preferable range is 0.009 to 0.05 cation%. The Sb ³⁺ content is preferably reduced for the above reasons, and the Sb ³⁺ content is preferably 0 to 1 cation%, more preferably 0 to 0.1 cation%, and still more preferably 0 to 0. 08 cation%, an even more preferred range is 0 to 0.05 cation%. Although the content of Sb ³⁺ may be a 0 cation%, In the case of obtaining the effect of ^{Sb 3+} addition, the content of ^{Sb 3+} in the above range, preferably to 0.008 or more cationic% , More preferably 0.009 cation% or more, and still more preferably 0.01 cation% or more.

^{Incidentally,} Ce 2+, the content of each ^{Sb 3+,} the content of ^{Ce 2+} and ^{Sb 3+} is the total amount of cationic components other than ^{Ce 2+} and ^{Sb 3+} as 100%, is calculated values outside split.

Other cationic components that can be included include Zn ²⁺ . Zn ²⁺ is an effective component for improving the meltability and devitrification resistance. When the content of Zn ²⁺ exceeds 6 cation%, the devitrification resistance tends to decrease. Therefore, the content of Zn ²⁺ is preferably in the range of 0 to 6 cation%, and in the range of 0 to 4 cation%. More preferably, it is more preferably in the range of 0 to 2 cation%, still more preferably in the range of 0 to 1 cation%, and it can also be 0 cation%.

In order to solve the problems of the invention, the total content of P ⁵⁺ , Al ³⁺ , Li ⁺ , Na ⁺ , Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Cu ²⁺ is 95 cation% or more. Preferably, it is 97 cation% or more, more preferably 98 cation% or more, still more preferably 99 cation% or more, even more preferably 99.8 cation% or more, 100 Even more preferred is cation%.

O ²⁻ and F ⁻ are both major anion components.

When the content of O ²⁻ is less than 50 anion%, the weather resistance of the glass is lowered. Moreover, the viscosity of the glass at the time of manufacture becomes too high, and shaping becomes difficult. In order to bring the viscosity of the glass into a range suitable for molding, the melting temperature must be increased, and there is a problem that Cu ^{2+ in} the glass is reduced and the transmittance near a wavelength of 400 nm is lowered. On the other hand, if the content of O ²⁻ exceeds 75 anion%, in order to obtain a homogeneous glass, the melting temperature has to be increased, and Cu ^{2+ in} the glass is reduced, and the transmittance in the vicinity of a wavelength of 400 nm is obtained. The problem of deteriorating arises. Therefore, the content of O ²⁻ is in the range of 50 to 75 anion%. A preferable range of the content of O ²⁻ is 50 to 70 anion%, a more preferable range is 50 to 65 anion%, and a further preferable range is 50 to 63 anion%.

When the content of F ⁻ is less than 25 anion%, in order to obtain a homogeneous glass, the melting temperature has to be increased, and Cu ^{2+ in} the glass is reduced, resulting in a decrease in transmittance in the vicinity of a wavelength of 400 nm. The problem arises. On the other hand, when the content of F ⁻ exceeds 50 anion%, the weather resistance of the glass decreases. Moreover, the viscosity of the glass at the time of manufacture becomes too high, and shaping becomes difficult. Therefore, the content of F ⁻ is in the range of 25 to 50 anion%. A preferred range for the content of F ⁻ is 30-50 anion%, a more preferred range is 35-50 anion%, a further preferred range is 37-50 anion%, and a more preferred range is 38-49 anion%.

The functions of Cl ⁻ , Br ⁻ and I ⁻ are as described above. When the total content of Cl ⁻ , Br ⁻ and I ⁻ is less than 0.001 anion%, it is difficult to obtain a sufficient effect of suppressing the wetting of the glass melt, and when it exceeds 1 anion%, Cu ²⁺ is reduced. It becomes Cu ⁺ , and the transmittance near a wavelength of 400 nm is reduced, or the corrosion of the material such as platinum, platinum alloy, gold, and gold alloy constituting the nozzle or the glass melting vessel is increased, and the material becomes a foreign matter. It causes problems such as mixing into glass. Therefore, the total content of Cl ⁻ , Br ⁻ and I ⁻ is in the range of 0.001 to 1 anion%. A preferable range of the total content of Cl ⁻ , Br ⁻ and I ⁻ is 0.005 to 0.5 anion%, a more preferable range is 0.008 to 0.1 anion%, and a further preferable range is 0.008 to 0.00. 07 anion%, a more preferable range is 0.008 to 0.06 anion%, and an even more preferable range is 0.009 to 0.05 anion%.

Incidentally, ^Cl -, Br ^- and I ^- the content of, ^Cl -, Br ^- and I ^- the total content of, ^Cl -, Br ^- and I ^- the total amount of anionic components other than the 100 anionic%, It is a value calculated by extra-dividing.

Among Cl ⁻ , Br ⁻ and I ⁻ , the most excellent effect is Cl ⁻ , and therefore it is preferable to add only Cl ⁻ out of Cl ⁻ , Br ⁻ and I ⁻ . The preferred range of the Cl ⁻ content is 0.005 to 0.5 anion%, more preferred range is 0.008 to 0.1 anion%, further preferred range is 0.008 to 0.07 anion%, and even more preferred range. Is 0.008 to 0.06 anion%, and an even more preferable range is 0.009 to 0.05 anion%.

The near-infrared light absorbing glass of the present invention is a fluorophosphate glass, and O ²⁻ and F ⁻ occupy most of the anionic component. That is, the total content of O ²⁻ and F ⁻ can be a guideline of 95 anion% or more. In order to achieve excellent weather resistance, maintenance of high transmittance in the vicinity of a wavelength of 400 nm, and excellent devitrification resistance, the total content of O ²⁻ and F ⁻ is preferably 96 anion% or more, and 97 anions % Or more, more preferably 98 anion% or more, and even more preferably 100 anion%. In order to achieve the object of the invention, the anion component is preferably composed of O ²⁻ , F ⁻ , and at least one halogen component selected from Cl ⁻ , Br ⁻ and I ⁻ .

  Next, components that are not preferably contained in the near-infrared light absorbing glass of the present invention will be described. Pb, As, Cd, Cr, U, and Th are preferably not included in consideration of an environmental load.

Ag is difficult to melt, lowers the homogeneity of the glass, and becomes a light scattering source. Therefore, the content of Ag should be reduced to less than 0.1% by mass in terms of Ag ₂ O. In the above indication method, the preferable range of the Ag content is less than 0.05% by mass, the more preferable range is less than 0.01% by mass, the still more preferable range is less than 0.005% by mass, and the more preferable range is 0.001. It is more preferable that the content is less than mass% and Ag is not contained.

V has the effect of reducing the transmittance near the wavelength of 400 nm. Therefore, the V content should be reduced to less than 0.02% by mass in terms of V ₂ O ₅ . In the above display method, the preferable range of the V content is 0.01% by mass or less, the more preferable range is 0.005% by mass or less, the further preferable range is 0.001% by mass or less, and V is not contained. Is more preferable.

  Co has the effect of increasing absorption in the visible region and decreasing the transmittance near the wavelength of 400 nm. Therefore, the content of CoO is preferably less than 0.01% by mass in terms of CoO, more preferably 0.008% by mass or less, and more preferably 0.005% by mass or less. More preferably, it is more preferable to make it 0.001 mass% or less, and it is still more preferable not to contain Co.

  Fluorophosphate glass exhibits remarkable volatility in addition to the property of being easily wetted to the outer peripheral surface of the nozzle in a molten state. Due to this volatility, part of the glass melt is altered, causing striae in the formed glass. Further, in the process of continuously flowing out and forming the glass melt, there is a problem that the glass composition changes with time due to volatilization, and accordingly, the characteristics of the glass also change with time.

In order to solve such problems, a glass in which the volatility in the melt state is suppressed is desired. From suppressing the volatility of the near-infrared light absorbing glass consisting of fluorophosphate ^glass, is the molar ratio of ^{O 2-} content to the content of ^{P 5+} and ^(O 2- ^{/ P 5+)} to 3.5 or more It is preferable. Here, the content of P ^{5+ and} the content of O ²⁻ are both a cation component and an anion component, the content ratio of P ⁵⁺ when the total content of all glass components is 100%, O ^{2. -Means} the content ratio.

When the molar ratio (O ²⁻ / P ⁵⁺ ) is less than 3.5, phosphonyl fluoride having remarkable volatility is generated during glass melting, and the volatility of the glass becomes remarkable, but the molar ratio (O ^{2 −} / P ⁵⁺ ) of 3.5 or more suppresses the formation of phosphonyl fluoride, suppresses the volatility of the glass, changes the glass composition due to volatilization, and various characteristics such as optical characteristics due to the composition change. Change can be suppressed. Moreover, generation of striae can be prevented by suppressing volatility, and a homogeneous glass can be easily obtained. For these reasons, the preferred range of the molar ratio (O ²⁻ / P ⁵⁺ ) is 3.5 or more, the more preferred range is 3.53 or more, and the more preferred range is 3.55 or more. On the other hand, in order to maintain the thermal stability of the glass well, the molar ratio (O ²⁻ / P ⁵⁺ ) is preferably in the range of 4.0 or less, more preferably in the range of 3.8 or less. Preferably, it is more preferably 3.7 or less.

  In the manufacture of the glass, metaphosphates, oxides, carbonates, nitrates, fluorides, chlorides, bromides, iodides, etc. are appropriately used, and the raw materials are weighed and mixed so as to have a desired composition. Heating and melting at 800 to 900 ° C. in a heat-resistant crucible, for example, a platinum or platinum alloy crucible. At this time, it is desirable to cover the crucible with a heat-resistant lid such as platinum in order to suppress volatilization of the fluorine component. The molten glass is agitated and clarified, and a homogeneous glass melt that does not contain bubbles is poured from a platinum, platinum alloy, gold, or gold alloy nozzle for glass outflow to be molded.

A phenomenon in which glass melt flowing out from the nozzle tip wets from the nozzle tip to the nozzle outer peripheral surface due to at least one or more halogen components of Cl ⁻ , Br ⁻ and I ⁻ contained in the glass melt when the glass flows out. The effect which suppresses is acquired. As a result, it is possible to reduce or prevent a phenomenon in which the wet glass melt is altered and taken into the glass melt that flows out after the alteration, resulting in defects such as striae and devitrification.

In addition to providing a near-infrared light absorbing filter for constituting a compact imaging system including a semiconductor image sensor, the near-infrared light-absorbing glass of the present invention has an external transmittance of 50% at a wavelength of 615 nm. Glass having a thickness of 0.5 mm or less is preferable, glass having a thickness of 0.4 mm or less is more preferable, and glass having a thickness of 0.35 mm or less is more preferable. The external transmittance to a light ray perpendicular to the intensity I _in respect of two parallel surfaces of the glass, when the intensity of light transmitted through the glass was I _out, the ratio of I _out for I _in (I _out / I _in ).

  A filter for correcting color sensitivity of a semiconductor image sensor is required to maintain a high visible light transmittance while enhancing the function of cutting near infrared light. From such a viewpoint, in a glass having a thickness at which the external transmittance at a wavelength of 615 nm is 50%, the external transmittance at a wavelength of 400 nm is preferably 80% or more, more preferably 83% or more, and 85 % Or more is more preferable. Regarding the absorption of near infrared light, in the glass having the above thickness, the external transmittance at a wavelength of 1200 nm is preferably 25% or less, more preferably 22% or less, and more preferably 20% or less. More preferably, it is more preferably 19% or less.

  In the near-infrared light absorbing glass of the present invention, the external transmittance suddenly monotonously decreases at a wavelength longer than the wavelength of 615 nm, and cuts near-infrared light. Further, when the wavelength becomes longer, the external transmittance starts to increase slightly. However, if the external transmittance at a wavelength of 1200 nm is 25% or less, the near infrared light absorption effect is not hindered.

  As the glass forming method, conventionally used methods such as casting, pipe outflow, roll, and press can be used.

  The near-infrared light absorbing glass of the present invention is excellent in weather resistance. 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 near infrared light absorption filters. The weather resistance is determined by holding an optically polished glass sample for 1000 hours at 60 ° C. and a relative humidity of 80%, 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. Under the above conditions, the near infrared light absorbing glass of the present invention is not observed to be burnt, and has been confirmed to have good weather resistance.

[Near-infrared absorption filter]
The near-infrared light absorption filter of the present invention is a filter using the above-mentioned near-infrared light absorption glass.

  A production example of the near-infrared light absorption filter is as follows.

  First, a clarified and homogenized molten glass is melted so as to obtain the above glass, and it flows out from a pipe and flows into a mold to form a large glass block having a large plate thickness. For example, a mold composed of a flat and horizontal bottom surface, a pair of side walls facing each other across the bottom surface, and a weir plate closing one opening located between the pair of side walls is prepared. A molten glass homogenized at a constant outflow speed from a platinum alloy pipe is cast into a mold. The cast molten glass spreads in the mold and is formed into a sheet glass that is regulated to a certain width by a pair of side walls. The formed glass sheet is continuously drawn out from the opening of the mold. Here, a large and thick glass block can be formed by appropriately setting molding conditions such as the shape and dimensions of the mold and the outflow speed of the molten glass.

  The formed glass block is transferred to an annealing furnace that has been heated in the vicinity of the glass transition temperature in advance, and is gradually cooled to room temperature. The glass block from which distortion has been removed by slow cooling is subjected to accurate slicing, grinding and polishing, and a glass plate having both surfaces optically polished can be obtained. This glass plate can also be used as a near-infrared light absorption filter, but a near-infrared light absorption filter can also be made by laminating the glass plate. A plate-like crystal that has been optically polished on both sides is bonded to one side of a plate-like near-infrared light absorbing glass that has been optically polished on both sides, and a plate-like crystal that transmits visible light to one side of the crystal and is optically polished on both sides. Optical glass, for example, BK-7 (borosilicate optical glass) is bonded. Such a structure constitutes a near-infrared light absorption filter, but another plate-like optical glass that transmits visible light and is optically polished on both sides (for example, BK-7). ) May be pasted together. An optical multilayer film is formed on the surface of the filter as necessary.

  As described above, the case where the glass block is processed into the glass plate has been described. However, the glass block can be ground and polished to produce a lens, or processed into other shapes.

  The near-infrared light absorbing glass of the present invention is a fluorophosphate glass and has a low glass transition temperature. Therefore, the optical functional surface is not subjected to mechanical processing such as grinding or polishing after molding by precision press molding (mold molding). Optical elements such as lenses and diffraction gratings can also be molded. For example, a molding surface of a known press molding material such as SiC or cemented carbide is processed with high accuracy into a shape obtained by inverting the lens surface of an aspheric lens, and upper and lower dies are produced. If necessary, a glass preform made of the near-infrared light absorbing glass of the present invention is heated and precision press-molded using a known barrel type or upper and lower type guide members. In this way, the molding surface can be precisely transferred to glass to produce an aspheric lens. Such an aspheric lens is also a near infrared light absorption filter of the present invention. The aspherical lens thus obtained can constitute part or all of the optical system for forming an image of the subject on the light receiving surface of the semiconductor image sensor, and the number of optical components in the imaging device can be reduced. It can be reduced, and it is effective for space saving and cost reduction.

  With a diffraction grating, the upper and lower molds are processed with high precision by processing the inverted shape of the diffraction grating on the molding surface of the press mold material, and the glass preform is precision press-molded in the same manner as above. It can also be used as a near infrared light absorption filter.

  The near-infrared light absorption filter with a diffraction grating functions as an optical low-pass filter for light incident on the semiconductor image sensor. Therefore, since the near-infrared light absorption filter and the optical low-pass filter can be formed as one element, the number of optical components in the imaging apparatus can be reduced, and space saving and cost reduction can be achieved.

The molding surface of the press mold material is precisely processed into a shape in which the groove of the diffraction grating is inverted while the lens surface (for example, the lens surface of an aspherical lens) is inverted. If molded, a near-infrared light absorption filter having a near-infrared light absorption function, an optical low-pass filter function, and a lens function can be produced.
A known release film may be formed on the press mold surface as necessary. In addition, various conditions for precision press molding may be appropriately determined according to specific specifications of the target near-infrared light absorption filter while applying known ones.

By producing near-infrared light absorption filters by precision press molding in this way, aspherical lenses, optical low-pass filters with diffraction gratings, aspherical lenses equipped with diffraction gratings that function as optical low-pass filters, etc. are obtained by grinding and polishing. Elements that are not suitable for mass production can also be manufactured with high productivity.
If necessary, an optical multilayer film such as an antireflection film may be formed on the surface of the near infrared light absorption filter.

  According to the near-infrared light absorption filter of the present invention, the visible light transmittance is high and the near-infrared light absorption is large, so that the color sensitivity correction of the semiconductor imaging device can be performed satisfactorily. Moreover, it can also be set as a filter with high optical homogeneity.

[Imaging device]
The imaging device of the present invention is an imaging device including the near-infrared light absorption filter of the present invention and a semiconductor image sensor.

  Here, what was illustrated previously can be used as a near-infrared light absorption filter. A semiconductor image sensor has a semiconductor image sensor such as a CCD or CMOS mounted in a package, and a light receiving portion is covered with a translucent member. The translucent member can also serve as a near infrared light absorption filter, or the translucent member can be separate from the near infrared light absorption filter.

  The imaging apparatus of the present invention can also include an optical element such as a lens or a prism for forming an image of a subject on the light receiving surface of the semiconductor image sensor.

  According to the imaging device of the present invention, the near-infrared light absorption filter having excellent optical homogeneity, high transmittance in the visible region, and large absorption in the near-infrared region is mounted, so that the color sensitivity correction is excellent. Thus, an imaging apparatus capable of obtaining an image with excellent image quality can be provided.

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

(Examples 1-6)
Metaphosphate, oxide, carbonate, nitrate, fluoride, chloride, etc. are appropriately used to weigh and mix the raw materials so as to have the composition shown in Table 1, and then a heat-resistant crucible such as platinum or a platinum alloy Heat and melt in a crucible at 800-900 ° C. At that time, in order to suppress volatilization of the fluorine component, the crucible was covered with a heat-resistant lid such as platinum. A glass melt in a molten state is agitated and clarified, and a homogeneous glass melt that does not contain bubbles is poured from a platinum, platinum alloy, gold, or gold alloy glass outlet nozzle into a mold. A near-infrared light-absorbing glass was obtained by forming into a block and annealing to room temperature.

  When the glass melt was allowed to flow out from the glass outflow nozzle, the tip of the nozzle was observed, and almost no glass melt wetted on the outer peripheral surface of the nozzle was observed.

  Moreover, when the shape | molded glass was observed, striae and devitrification were not recognized about the glass of Examples 1, 2, 4, and 5, and it confirmed that the optically homogeneous glass was obtained. Moreover, no foreign matter such as platinum foreign matter or gold foreign matter was observed in the glass.

  For the glasses of Examples 3 and 6, slight striae that were thought to have occurred due to volatilization in the melt state were observed in the glass surface layer, but the inside was optically homogeneous, and the entire glass was devitrified. No foreign matter such as platinum foreign matter or gold foreign matter was observed.

  Next, samples for various measurements were cut out from the glass blocks obtained using the various glasses, and the light transmittance was determined as follows.

  Using a glass that was optically polished on both sides to the thickness shown in Table 1 (thickness at which λ50 was 615 nm), the spectral transmittance at a wavelength of 200 to 1200 nm was measured using a spectrophotometer. From the above measurement results, the external transmittance at wavelengths of 400 nm and 1200 nm was determined. The measurement results are shown in Table 1.

  Each glass of Examples 1 to 6 has sufficient transmission of visible light and absorption of near-infrared light, and color sensitivity of a semiconductor image sensor such as CCD or CMOS without forming a near-infrared light blocking coat. It has a transmittance characteristic that can correct well.

  A glass sample made of each glass of Examples 1 to 6 and having the surface optically polished was prepared, and these samples were held at 60 ° C. and a relative humidity of 80% for 1000 hours, and then the burned state of the optically polished surface was visually observed. Observed. As a result, no burn condition was observed on the surface of any sample, and it was confirmed that the sample had good weather resistance.

(Comparative Example 1)
Glasses having the same composition as the glasses of Examples 1 to 6 were produced in the same manner as in Examples 1 to 6, except that none of Cl ⁻ , Br ⁻ and I ⁻ was included. When the glass melt was caused to flow out from the glass outflow nozzle, the tip of the nozzle was observed, and a remarkable wetting of the glass melt to the outer peripheral surface of the nozzle was observed. Further, when the molded glass was observed, striae more marked than those of the above-described examples were observed.

(Comparative Example 2)
Except for not including Ce ⁴⁺ and Sb ³⁺ , glasses having the same composition as the glasses of Examples 1 to 6 were produced in the same manner as in Examples 1 to 6. When the glass melt was allowed to flow out of the nozzle for glass outflow, the nozzle tip was observed, but no glass melt wetted on the outer peripheral surface of the nozzle and no striae was observed in the molded glass. As in Examples 1 to 6, when the spectral transmittance at a wavelength of 200 to 1200 nm was measured using glass that was optically polished on both sides to a thickness at which λ50 was 615 nm, the external transmittance at a wavelength of 400 nm was less than 80%. .

  When the molded glass was observed, a slight amount of platinum foreign matter was observed.

(Example 7)
In the same manner as in Examples 1 to 6, glass was melted, clarified and homogenized, and cast into a mold to form a plate glass made of glass having the same composition as in Examples 1 to 6. After slicing this plate-like glass, optical polishing was performed on both sides to obtain a glass plate having a desired thickness. This glass plate was diced to obtain a near-infrared light absorbing glass plate having a desired size having the above thickness. The glass plate had a thickness of 50% transmittance (thickness corresponding to the measured thickness in Table 1) at a wavelength of 615 ± 10 nm, and the size was 10 mm × 10 mm to 30 mm × 30 mm. Next, a thin plate glass made of a crystal processed into a plate shape and two optical glasses (BK-7) was prepared, and optical polishing was performed on both surfaces. And each thin plate is bonded together in the surface optically polished so that it laminates in order of the glass plate which consists of near-infrared light absorption glass, a crystal | crystallization, and two sheet | seats made from BK-7, and an antireflection film is formed on the outermost surface. A near infrared light absorbing element having a near infrared light absorbing filter function was prepared. As a result of observing an image taken by arranging this element on the front side of the light receiving surface of a semiconductor image sensor such as a CCD or CMOS, it was confirmed that good color correction was performed.

(Example 8)
In the same manner as in Examples 1 to 6, the glass was melted, clarified, and homogenized to obtain a glass melt, which was allowed to flow down from a platinum nozzle. Then, an appropriate amount of glass melt was received in a mold, and a spherical glass preform was formed. The molded preform was once cooled to room temperature, reheated and softened again in a non-oxidizing atmosphere such as nitrogen gas or a mixed gas of nitrogen and hydrogen, and pressed with a press mold. The molding surface of the press mold was precisely processed in advance into a shape obtained by inverting the shape of the target optical element, and these molding surfaces were precisely transferred to glass in the pressing step. After cooling to a temperature at which the glass does not deform in the press mold, the press-molded optical element was removed from the mold and annealed. Thus, an optical element such as an aspheric lens or a diffraction grating could be obtained. An element having a diffraction grating on the lens surface can also be made by precision press molding.

In addition, the glass block which consists of each glass of Examples 1-6 is produced similarly to Example 7, a distortion is reduced, a spherical glass preform is produced by cutting, grinding, and polishing, Similarly, an optical element such as an aspherical lens or a diffraction grating, or a near-infrared light absorption filter having a diffraction grating on the lens surface can be produced by a precision press molding method.
Various lens shapes such as a convex meniscus shape, a concave meniscus shape, a biconvex shape, a biconcave shape, a plano-convex shape, and a plano-concave shape can be made, but depending on the distance from the lens optical axis, It is preferable that constant near-infrared light absorption is obtained regardless of the distance from the lens optical axis by making the distances through which the light beams traveling through the lens pass as much as possible. For this purpose, it is desirable that the lens shape be a convex meniscus shape or a concave meniscus shape.

The near-infrared light absorbing glass of the present invention is a near-infrared light-absorbing element such as a near-infrared light-absorbing filter having excellent visible light region high transmittance, excellent near-infrared region absorption characteristics, excellent homogeneity, etc. Is preferably used. The near-infrared light absorption filter is particularly suitable for correcting the color sensitivity of an image sensor such as a CCD or CMOS used in a digital camera, a VTR camera, or the like.

Claims (5)

In the near-infrared light absorbing glass made of Cu-containing fluorophosphate glass,
The content of P ⁵⁺ is 20 to 45 cation%,
Al ³⁺ content is 1-25 cation%,
Li ⁺ content is 10-30 cation%,
Na ⁺ content 0-15 cation%,
The total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ is 14-50 cation%,
Cu ²⁺ content is 0.1 to 10 cation%,
Ce ⁴⁺ and Sb ^{3+ have} an external total content of 0.005 to 2 cation%,
The content of O ²⁻ is 50 to 75 anion%,
The content of F ⁻ is 25-50 anion%,
Cl ⁻ , Br ⁻ and I ^{− have} an outer total content of 0.001 to 1 anion%,
The near-infrared light absorbing glass characterized by being. Near-infrared light absorbing glass as claimed in claim 1 molar ratio of the content of ^{O 2-} to the content of ^{P 5+ (O 2- / P 5+} ) is 3.5 or more. The near-infrared light-absorbing glass according to claim 1, comprising 0.01 to 2 cations of Ce ²⁺ .   The near-infrared light absorption filter using the near-infrared light absorption glass as described in any one of Claims 1-3. An imaging apparatus comprising the near-infrared light absorption filter according to claim 4 and a semiconductor image sensor.