Glass article and light guide

1. A glass article comprises a glass which includes from 1 mass ppm to 80 mass ppm of total iron oxide (t-Fe 2 O 3 ) in terms of Fe 2 O 3 , has a redox of iron of from 0% to 50% and includes from 0.01 mass ppm to 4.0 mass ppm of NiO, characterized in that the A value of the internal transmittance spectrum flatness of the glass article obtained by the following formula (1) is at least 0.83:

A =min( X,Y,Z )/max( X,Y,Z )  Formula(1)

wherein using the color matching functions x (λ), y (λ) and z (λ) in the XYZ color system described in JIS Z8701, and an internal transmittance S (λ) at 600 mm length of the glass article, X=Σ(S (λ)×x (λ)), Y=Σ(S (λ)×y (λ)) and Z=Σ(S (λ)×z (λ)) are defined.

2. The glass article according to claim 1 , wherein the content of NiO in the glass is within the range defined by the lower and upper limits of NiO as determined by the following formulae (7) and (8) by mass ppm expressed on an oxide basis:

Lower limit of NiO=−2.7−0.035 F+ 0.01 R+ 0.0025 FR   Formula (7)

Upper limit of NiO=2.4−0.055 F+ 0.01 R+ 0.002 FR   Formula (8)

wherein F (mass ppm) is the content of total iron in terms of Fe 2 O 3 , and R (%) is the redox of iron and is a value of the proportion of the content of Fe 2+ in terms of Fe 2 O 3 to the content of total iron in terms of Fe 2 O 3 .

3. The glass article according to claim 1 , wherein the contents of NiO and Cr 2 O 3 in the glass satisfy the following formula (9) by mass ppm expressed on an oxide basis:

0.1≤[NiO]+2[Cr 2 O 3 ]≤5.0  Formula (9)

wherein [NiO] is the content (ppm) of NiO, and [Cr 2 O 3 ] is the content (ppm) of Cr 2 O 3 .

4. The glass article according to claim 1 , wherein in the glass, the content of Cr 2 O 3 is at most 5 ppm by mass ppm expressed on an oxide basis.

5. The glass article according to claim 1 , wherein in the glass, the content of MnO 2 is at most 50 ppm by mass ppm expressed on an oxide basis.

6. The glass article according to claim 1 , wherein in the glass, the content of CeO 2 is at most 1,000 ppm by mass ppm expressed on an oxide basis.

7. The glass article according to claim 1 , wherein the matrix composition of the glass, which excludes the total iron oxide in terms of Fe 2 O 3 , NiO, CeO 2 , and other trace components, a content of the other trace components being at most 1,000 ppm, comprises, by mass percentage expressed on an oxide basis, substantially from 60 to 80% of SiO 2 , from 0 to 7% of Al 2 O 3 , from 0 to 10% of MgO, from 0 to 20% of CaO, from 0 to 15% of SrO, from 0 to 15% of BaO, from 3 to 20% of Na 2 O, and from 0 to 10% of K 2 O.

8. The glass article according to claim 1 , wherein the matrix composition of the glass, which excludes the total iron oxide in terms of Fe 2 O 3 , NiO, CeO 2 , and other trace components, a content of the other trace components being at most 1,000 ppm, comprises, by mass percentage expressed on an oxide basis, substantially from 45 to 80% of SiO 2 , more than 7% and at most 30% of Al 2 O 3 , from 0 to 15% of B 2 O 3 , from 0 to 15% of MgO, from 0 to 6% of CaO, from 0 to 5% of SrO, from 0 to 5% of BaO, from 7 to 20% of Na 2 O, from 0 to 10% of K 2 O, and from 0 to 10% of ZrO 2 .

9. The glass article according to claim 1 , wherein the matrix composition of the glass, which excludes the total iron oxide in terms of Fe 2 O 3 , NiO, CeO 2 , and other trace components, a content of the other trace components being at most 1,000 ppm, comprises, by mass percentage expressed on an oxide basis, substantially from 45 to 70% of SiO 2 , from 10 to 30% of Al 2 O 3 , from 0 to 15% of B 2 O 3 , from 5 to 30% in total of at least one alkaline earth metal oxide selected from the group consisting of MgO, CaO, SrO and BaO, and at least 0% and less than 3% in total of at least one alkali metal oxide selected from the group consisting of Li 2 O, Na 2 O, and K 2 O.

10. A light guide using the glass article as defined in claim 1 .