JPS6054249B2 - Optical glass for light path - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has a refractive index (nd) of 1.55 or more and an Abbe number (ν
d) is 50 or more, specific gravity is 2.80 or less, and has excellent chemical durability.

Various elements such as lenses, prisms, and mirrors are used in general optical systems.

There are various materials for these materials, but optical glass is often used as a material, not only for those that require high precision, but also for those that require high precision. Most of these optical glasses are designed to be used as lenses, taking into consideration refractive index, dispersion, etc. A lens can be thought of as a light conversion element that takes advantage of the refractive index and spherical surface of glass, but a prism is also a light conversion element. This uses a flat surface rather than a spherical surface, and often reflects or transmits light inside the glass, and is considered to be an element for adjusting the optical path length, converting the axis of symmetry, etc. Optical glass conventionally used to adjust the optical path length, such as prism glass for binoculars, is an optical glass originally designed for lenses, and is not an optical glass developed for prisms. Therefore, when optical glass for lenses is used for prisms, there are advantages and disadvantages. For example, optical glasses commonly referred to as BK7 and BaK4 are commonly used as prism glasses for conventional binoculars, and their performance is shown in Table 1. However, the acid resistance is based on the "Method for Measuring Chemical Durability of Optical Glass (Powder Method)" specified by the Japan Optical Glass Industry Association. As shown in Table 1, BK7 has the advantage of having a low specific gravity and relatively good chemical durability, and the disadvantage of having a low refractive index.

BaK4 has the advantage of a high refractive index and the disadvantages of poor chemical durability and high specific gravity. Conventionally, four prisms have been used in binoculars, and the weight of the binoculars is largely determined by the weight of the prisms. Therefore, when using heavy prisms, efforts are made to make the metal parts of the binoculars lighter, but when processing light metal, there is a possibility of encountering dangers such as ignition. Therefore, it is advantageous in various aspects to use a prism that is as light as possible. If the refractive index of the prism is low, the pupil diameter of the produced binoculars will be small, resulting in a narrow field of view and a dark feeling, so a prism with a moderately high refractive index will be effective. However, it is also more effective to make the aperture number of the prism as large as possible in consideration of chromatic aberration. The better the chemical durability of the prism, the better; if the chemical durability is poor, discoloration will occur during the prism polishing process, making the prism's retention extremely poor, and resulting in higher product costs. Connect. Taking into consideration the various points mentioned above, the present inventors have developed a prism with a refractive index of 1.55 or more, an Atpe number of 50 or more, a specific gravity of 2.80 or less, and an optical path with extremely excellent chemical durability. As a result of intensive research into the development of optical glass for
It has been found that O--TiO2 and/or ZrO2 systems are suitable for the purpose.

That is, the present invention This is an optical glass for an optical path consisting of the above.

The reason why each compounded component is limited as described above is as follows.

SiO2 is an essential blending component, but if SiO2 is less than 55% by weight, glass with excellent chemical durability cannot be obtained.
If it exceeds 65% by weight, the viscosity of the glass increases and it becomes difficult to obtain a homogeneous glass.

CB2O3 is an essential compounding component and is used to improve the stability and meltability of glass, but B2
If O3 is less than 1% by weight, it will have little effect on improving the stability of the glass and the meltability of the glass, and if it exceeds 1% by weight, it will be difficult to obtain a glass with excellent chemical durability. TiO
2 and/or ZrO2 are essential ingredients, but TiO
If 2+ZrO2 is less than 1% by weight, it will have little effect of increasing the refractive index of the glass or improving chemical durability. If it exceeds 5% by weight, the glass's number will be small, causing problems with chromatic aberration, and increasing the specific gravity. This is not preferable because it increases the size.

Regarding each limitation, if TiO2 exceeds 5% by weight, the Abbes number of the glass will become small and problems of chromatic aberration will occur, which is undesirable, and if ZrO2 exceeds 5% by weight, the specific gravity will increase, which is undesirable. CaO is an essential blending component, but if CaO is less than 1% by weight, it not only lowers the refractive index but also causes difficulties in melting the glass, which is undesirable, and if it exceeds 2% by weight, the chemical durability of the glass deteriorates. Sexuality becomes worse.

ZnO is an essential blending component, but if ZrlO is less than 3% by weight, it will have little effect on increasing the refractive index, improving the stability of the glass, and improving chemical durability, and if it exceeds 15% by weight, it will not melt the glass. This is not preferable because it causes problems. R2O
(Li2O, Na2O, K2O) are essential blending components, and the reason why one or more types of R2O is limited to 5 to 1% by weight is that less than 5% by weight causes difficulties in melting the glass, so it is preferable. This is because if the filtration amount exceeds 1%, the chemical durability of the glass deteriorates.

Al2O3 is an optional component, but if Al2O3 exceeds 4% by weight, it is difficult to obtain a homogeneous glass.

AS2O3 is an optional compounding component, but since AS2O3 acts as a defoaming agent for bubbles when glass is melted, it is better to use it in an amount of 1% by weight or less. In the present invention, for convenience in manufacturing the glass, up to several percent of MgO, SrO, BaO, etc. may be included in the composition of the optical glass for optical path of the present invention.

Examples according to the present invention are shown in Table 2.

As described above, it is possible to obtain an optical glass for optical paths having a refractive index of 1.55 or more, an Abbé number of 50 or more, a specific gravity of 2.80 or less, and excellent chemical durability.

Claims (1)

[Claims] 1 SiO_255-65 wt% B_2O_31-10 wt% TiO_2+ZrO_21-5 wt% TiO_20-5 wt% ZrO_20-5 wt% CaO10-20 wt% ZnO3-15 wt% R_2O (Li_2O, Na_2O, K_2O ) Optical glass for optical path comprising 5-12% by weight of one or more of the following: 30-4% by weight of Al_2O_30-1% by weight of As_2O_.