JPS6024060B2 - Optical fiber core glass for endoscopes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in the core glass of optical fibers for endoscopes.

When optical fibers East are used as image guides, the optical fibers East must be arranged in a one-to-one correspondence with their ends.

Particularly when the image guide optical fiber east is used as an endoscope, it is often required that the optical fiber east be fixed to each other at both ends and that the intermediate portion be flexible. . Further, it is necessary that the coloring of each of the above-mentioned optical fibers be as little as possible and uniform.
Even if each optical fiber is very slightly colored, if there is uneven coloring among the optical fibers, color unevenness will occur in the field of view of the endoscope, resulting in defects. The present invention relates to a core glass necessary for improving the yield of optical fibers for endoscopes by reducing the non-uniformity of each optical fiber.

By the way, optical fiber bundles having fixed end portions and a flexible intermediate portion as described above have conventionally been manufactured by the following method. For example, in a double platinum vortex, a core glass with a relatively high refractive index is placed in the inner platinum vortex, and a covering glass with a relatively low refractive index is placed in the outer platinum vortex. Heating the glass to a temperature (for example, about 1000 pm), pull both glasses through the bottom hole of the platinum vortex, coat the core glass with the coated glass, and wind the obtained optical fiber into a row of loops without gaps. Fix the hole with adhesive, wrap it in a line in a loop shape without any gaps in the same way as before, fix with adhesive at the fixed part of the loop formed before, and repeat this operation until the desired thickness is reached. Obtain a loop-shaped optical fiber,
A flexible optical fiber bundle for an image guide is produced by cutting approximately the center of the fixed portion of the looped optical fiber at a right angle to the length of the optical fiber, and polishing these two cut surfaces. It will be done. In this method, the core glass is flint glass [weight composition: Si02 = 44.3%, POO =
45.7%, K20=6.3%, Na20=3.1%,
AI203=about 0.2%, AS203=0.3%, specific gravity=3.61, nd=1.6200, Vd=36.3, dislocation point=44〆C, bending point=482℃, expansion coefficient 97× 1
Crown glass [weight composition: Si02 = 65.6%, Ca○ = 5.0%] was used as the coating glass.
0%, Mg0=3.8%, K20=1.5%, Na20
=16.1%, N203=2.3%, Ba○=2.3%
, B203=2.2%, Pine 203=0.4%, Specific gravity=2
．． 55, nd=1.5212, Vd=59. Dislocation point=
528qo, bending point: 570℃, expansion coefficient 98×10-
7 (skin/skin temperature)] is used. As mentioned above, when a flint glass containing a large amount of P is melted in a platinum vortex as a core glass, a small amount of platinum is splintered into the glass and colors the glass. The degree of this coloring is very irregular, sometimes being large and sometimes being small. Moreover, even if the optical fibers are inspected one by one, it is almost impossible to find any differences, but when assembled as optical fibers, the fibers are rejected due to uneven coloring. In order to eliminate the above-mentioned drawbacks, the present invention replaces Pb○ in the core glass with Zn0, Ba0, etc. to reduce the drawback of coloring due to P, and prevent a decrease in refractive index due to a decrease in P. Further, the present invention provides a core glass for optical fibers for endoscopes that reduces the deterioration of workability due to a decrease in POO and has a high yield. Furthermore, when the optical fiber Higashi having specularity is used as an endoscope or the like, the endoscope is inserted into the body and the observation site is irradiated with X-rays from outside the body. In this case, a core glass with a high P content is much more likely to be colored than a core glass with a low Pb0 content and becomes unusable in a relatively short period of time. One purpose of the present invention is to solve the above-mentioned drawbacks by converting the POO of the core glass into Ba.
○ etc. to reduce the content of POO, and create a core glass for endoscope optical fibers that is not easily colored by X-ray irradiation and can be used for a relatively long period of time (for example, the lifespan is about 20% longer). This is what we provide. Furthermore, when optical fibers with condensable properties are used as light guides in endoscopes, etc., a high-intensity xenon lamp is used as the light source, and more of the radiation from the xenon lamp is focused on the end face of the optical fibers. It is necessary to illuminate the subject as brightly as possible through the optical fiber east. Recently, there has been a need to make the diameter of the optical fiber as small as possible and to provide as much illumination as possible. As a result, the light source becomes even brighter, and the temperature of the east end of the optical fiber that receives the light becomes high (for example, 500 to 600
During long-term use, the optical fiber's east end face becomes deformed or devitrified, resulting in a decrease in brightness. Another object of the present invention is to reduce the Pbo content by replacing P in the core glass with Bao or the like, in order to eliminate the above-mentioned drawbacks.
The purpose of the present invention is to provide a core glass for an endoscope optical fiber east which has a heat resistance temperature higher by, for example, about 100 qo, has less deformation and devitrification of the end face of the optical fiber east, and can be used for a long time. JP-A-53-60240 and JP-A-54-872 have already discussed improving the transmittance of optical fibers by reducing the P content to zero.
36, but the content of Pbo is set to zero,
When Ca○ is used as an essential component, the viscosity changes greatly with respect to temperature, resulting in poor workability, and it is extremely difficult to produce optical fibers with small seats and strict dimensional accuracy, such as optical fibers for endoscopes. The present invention relates to a core glass for optical fibers in endoscopes, which is characterized by having the following composition in terms of weight ratio.

35.0%<Sj○2ku47.0% 1.0%ku21.5% 1.0%kuPb○ <21.5% 7.0%<Zn○ <30.0% 8 .0 (total of one or more of Na20, K20, Li20)<13.9% If Si02 is 35.0% or less, water resistance and acid resistance deteriorate and it becomes practically unusable.

When Si02 is 47.0% or more, the refractive index nd becomes too small. The core glass of the optical fiber for endoscopes must have a refractive index of at least 1.55 due to the numerical aperture. If the value of ○ is 1.0% or less, the refractive index nd becomes too small. When the value of ○ is 21.5% or more, the change in viscosity with respect to temperature becomes too large. When Pb0 is 1.0% or less, the refractive index nd becomes small and the workability deteriorates.

When Pb0 is 21.5% or more, uneven coloring tends to occur. Furthermore, it is easy to be colored by X-ray irradiation, and the heat resistance temperature of the east end of the optical fiber is lowered. When Zm0 is 7.0% or less, the refractive index nd becomes too high as 4. Zn○ is 30.0%
In the above cases, the tendency to devitrify increases. Na2, K20, L
If the sum of one or more i20 is less than 8.0%, the coefficient of thermal expansion becomes too small.

If the total of one or more of Na20, K20, and Li20 is 13.9% or more, the coefficient of thermal expansion becomes too large and the weathering resistance of the glass decreases. Furthermore, if (range ○ 10 Pb ○ 10 Zn ○) is less than 28.0%, the refractive index nd becomes too small, which is undesirable. If necessary, part or most of the mother ○ may be replaced with S. AI203,
B203 and the like can be added in an amount of about 5.0% without impairing the features of the present invention.

Also, a small amount of As203, Sb203, etc. is added as a clarifying agent. Tables 1 and 2 show examples of the present invention.

In the table, the transition point is the temperature at which the viscosity is approximately 1 to 3 poise, the inflection point is the temperature at which the viscosity is approximately 1 to 2 poise, and the water resistance and acid resistance (powder method) are determined by pulverizing the sample to a particle size of 420 to 59 cape. Wash with methyl alcohol and dry. Then, the specific gravity gram of this powder sample is placed in a platinum cage for elution. Next, this was placed in a quartz glass round-bottomed flask containing the test solution, treated in a boiling water bath for 60 minutes, and then dried.The value is the weight loss of the sample after drying in %. For water resistance, use distilled water (pH = 6.5 to 7.5) as the test solution, and for acid resistance, use 1/10 plate nitric acid (
pH=approximately 2.2). The examples described above mainly use glass with a relatively high refractive index as the core glass,
Double Optical Fiber East uses glass with a relatively low refractive index for the coating glass, but regarding the core glass of Triple Optical Fiber East, the outermost layer of the double optical fiber is coated with a glass layer that is easily eroded by chemicals. also has exactly the same effect.

Table 1 Composition is shown by weight Table 2 Composition is shown by weight

Claims (1)

[Claims] 1. A core glass for an optical fiber for an endoscope, characterized by having the following composition by weight: 35.0%<SiO_2<47.0% 1.0%<B_aO<21.5% 1.0%<PbO<21.5% 7.0%<ZnO<30.0% 8.0%<( Total of one or more of Na_2O, K_2O, Li_2O)<13.9%0%≦Al_2O_
3<5.0% 0%≦B_2O_3<5.0% 0%≦SrO<10.0%