Process for producing a near infrared cut filter glass

1. A process for producing a near infrared cut filter glass, the process comprising:

mixing a glass material and an oxidant for oxidizing Sb, thereby obtaining a raw material mixture; and

melting the raw material mixture, thereby obtaining the near infrared cut filter glass,

wherein:

the glass material comprises, by mass based on a total amount of the raw material mixture:

P 2 O 5 : from 30 to 55%,

AlF 3 : from 5 to 15%,

at least one alkaline earth metal fluoride selected from the group consisting of MgF 2 , CaF 2 , SrF 2 and BaF 2 : from 1 to 50% in terms of a total amount of MgF 2 +CaF 2 +SrF 2 +BaF 2 ,

ZnF 2 : from 0 to 20%,

at least one alkaline metal fluoride selected from the group consisting of LiF, NaF and KF: from 1 to 16% in terms of a total amount of LiF+NaF+KF,

CuO: from 5 to 14%, and

Sb 2 O 3 : from 0.1 to 3%;

up to 70% of fluorides based on a total amount of the fluorides in the glass material are optionally substituted by oxides;

the oxidant for oxidizing Sb is in an amount of from 0.1 to 5% by mass based on the total amount of the raw material mixture; and

the oxidant for oxidizing Sb comprises at least one compound selected from the group consisting of a nitrate compound, a sulfate compound, a peroxide, a perchlorate and chloric acid.

2. The process according to claim 1 , wherein the glass material comprises P 2 O 5 of from 35 to 45% by mass based on the total amount of the raw material mixture.

3. The process according to claim 1 , wherein the glass material comprises AlF 3 of from 8 to 12% by mass based on the total amount of the raw material mixture.

4. The process according to claim 1 , wherein the glass material comprises the at least one alkaline earth metal fluoride of from 10 to 40% by mass based on the total amount of the raw material mixture.

5. The process according to claim 1 , wherein the glass material comprises ZnF 2 of from 0 to 15% by mass based on the total amount of the raw material mixture.

6. The process according to claim 1 , wherein the glass material comprises the at least one alkaline metal fluoride of from 5 to 12% by mass based on the total amount of the raw material mixture.

7. The process according to claim 1 , wherein the glass material comprises CuO of from 8 to 12% by mass based on the total amount of the raw material mixture.

8. The process according to claim 1 , wherein the glass material comprises Sb 2 O 3 of from 0.3 to 2% by mass based on the total amount of the raw material mixture.

9. The process according to claim 1 , wherein the oxide for oxidizing Sb is in an amount of from 0.3 to 3% by mass based on the total amount of the raw material mixture.

10. The process according to claim 1 , wherein

the near infrared cut filter glass has a transmittance of 50% at an infrared-side wavelength of from 590 to 650 nm and a transmittance of at least 84% at a wavelength of 400 nm, and

the transmittances are calculated as transmittances of a glass plate with a thickness of 0.15 mm.

11. The process according to claim 1 , wherein said melting occurs at a temperature of from 750 to 1,000° C.

12. The process according to claim 1 , wherein the oxidant for oxidizing Sb is at least one selected from the group consisting of LiNO 3 , KClO 4 , NaClO 3 , MgSO 4 , BaO 2 , NaNO 3 , KNO 3 and Na 2 SO 4 .

13. A near infrared cut filter glass produced by a process comprising:

mixing a glass material and an oxidant for oxidizing Sb, thereby obtaining a raw material mixture; and

melting the raw material mixture, thereby obtaining the near infrared cut filter glass,

wherein:

the glass material comprises, by mass based on a total amount of the raw material mixture:

P 2 O 5 : from 30 to 55%,

AlF 3 : from 5 to 15%,

at least one alkaline earth metal fluoride selected from the group consisting of MgF 2 , CaF 2 , SrF 2 and BaF 2 : from 1 to 50% in terms of a total amount of MgF 2 +CaF 2 +SrF 2 +BaF 2 ,

ZnF 2 : from 0 to 20%,

at least one alkaline metal fluoride selected from the group consisting of LiF, NaF and KF: from 1 to 16% in terms of a total amount of LiF+NaF+KF,

CuO: from 5 to 14%, and

Sb 2 O 3 : from 0.1 to 3%;

up to 70% of fluorides based on a total amount of the fluorides in the glass material are optionally substituted by oxides;

the oxidant for oxidizing Sb is in an amount of from 0.1 to 5% by mass based on the total amount of the raw material mixture; and

the oxidant for oxidizing Sb comprises at least one compound selected from the group consisting of a nitrate compound, a sulfate compound, a peroxide, a perchlorate and chloric acid.

14. The near infrared cut filter glass according to claim 13 , wherein

the near infrared cut filter glass has a transmittance of 50% at an infrared-side wavelength of from 590 to 650 nm and a transmittance of at least 84% at a wavelength of 400 nm, and

the transmittances are calculated as transmittances of a glass plate with a thickness of 0.15 mm.

15. The process according to claim 13 , wherein the oxidant for oxidizing Sb is at least one selected from the group consisting of LiNO 3 , KClO 4 , NaClO 3 , MgSO 4 , BaO 2 , NaNO 3 , KNO 3 and Na 2 SO 4 .