Glass for light guide fiber

1. A glass for a light guide fiber that is used in a core of a fiber of a light guide, wherein the glass has a refractive index nd between 1.56 and 1.74 and has a composition described hereunder:

(A) SiO 2 : 20 to 55 wt %,

(B11) B 2 O 3 : 0 to 2.0 wt %,

(B2) does not contain P 2 O 5 and GeO 2 ,

(C1) (BaO+SrO+La 2 O 3 +Lu 2 O 3 +Ta 2 O 5 +Gd 2 O 3 +WO 3 ): 39 to 46 wt %,

(D1) ZnO: 4 to 16 wt %,

(E) does not contain Al 2 O 3 ,

(F) does not contain ZrO 2 ,

(G) does not contain PbO and As 2 O 3 ,

(H1) (Na 2 O+K 2 O): 4 to 10 wt %,

(I) Sb 2 O 3 : 0 to 0.050 wt %, and

(J1) (Na 2 SO 4 +K 2 SO 4 ): 0.32 to 0.78 wt %.

2. The glass for a light guide fiber according to claim 1 ,

wherein a content of Fe is 3 ppm or less, a content of Cr is 0.03 ppm or less, a content of Co is 0.01 ppm or less, a content of Ni is 0.02 ppm or less, and a content of Pt is 0.2 ppm or less.

3. The glass for a light guide fiber according to claim 2 ,

wherein a transmittance of a light of a wavelength between 380 and 750 nm of the fiber is 96%/m or more, and a transmittance of a light of a wavelength of 400 nm of the fiber is 90%/m or more.

4. The glass for a light guide fiber according to claim 3 ,

wherein after an X-ray resistance test is performed that implements a recovery process in which an illuminating light of 64 lumen/mm 2 is guided through the fiber for 600 minutes after the fiber is exposed to X-ray irradiation of 2.5 Gy, a transmittance of a light of a wavelength between 380 and 750 nm of the fiber recovers to 90% or more relative to a transmittance thereof before exposure to the X-ray irradiation.

5. The glass for a light guide fiber according to claim 4 ,

wherein raw materials are melted in a quartz crucible.