JPS6042245A - Directly moldable optical glass - Google Patents

Abstract

PURPOSE:To obtain directly moldable B2O3-RO-La2O3 glass (R is bivalent element) having high viscosity, a high refractive index and a low degree of dispersion by providing a specified composition. CONSTITUTION:This optical glass consists of, by weight, 12-35% SiO2, 9-29% B2O3 (SiO2/B2O3=1.1-3), 20-48% BaO and 31-50% La2O3, and it has 1.65- 1.82 refractive index nd and 40-60 Abbe's number nud. Oxides, hydroxide or nitroxide or nitrates corresponding to said components are mixed in the prescribed ratio, and the mixture is vitrified by melting at about 1,300-1,500 deg.C and mixing to manufacture said glass. Since the glass has high viscosity, direct molding can be carried out, and a glass article having stability to devitrification and superior chemical durability can be formed.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a high refractive index, low dispersion optical glass that has high viscosity and is directly moldable.

(Background of the Invention) Conventionally, optical products such as lenses and prisms are manufactured by (1) melting optical glass in a crucible and gradually cooling it to room temperature [7] to obtain a glass lump, and (2) melting this glass lump. After cutting into an appropriate size and shape according to the shape of the desired lens, prism, etc., (3) using a @-type, hot Soles l,
(4) Anneal to remove distortion (~, (51'4-) Grind the lens and prism material into the desired spherical or flat surface, and (after 6H-, sand or polish) It is manufactured after

In response, a direct molding method was developed to simplify the manufacturing process and save energy. This direct molding method uses molten glass to ) The glass is poured into a mold without cooling and press-formed before the glass solidifies. In this case, continuity of the manufacturing process is also being considered, and for this reason, the molten glass taken out from the continuous melting furnace directly below is divided into a certain amount by a set of shear brakes on the way down, and this divided , the glass is successively poured into the molds directly below. Therefore,
If the viscosity of the molten glass is low, it will be difficult to quantitatively divide it with a shear blade. In addition, if the viscosity is low, sink marks and other molding defects are likely to occur in the molded product.

The most important optical properties for glass are refractive index and dispersion, and when determining the glass composition to satisfy these properties, the viscosity is also determined, and it is extremely difficult to find a composition with particularly high viscosity. That's true. In fact, the type of glass that has low viscosity and is directly molded is S
i02-R20-PbO series, 5102・-R20-R
It is limited to classical optical glasses such as O-BaO system.

It (B gives an optical glass with high refractive index and low dispersion compared to C)
203-RO-La2O3-based glass has a low viscosity of 20 poise or less when taken out from the furnace, and is difficult to mold directly.

(Object of the Invention) Therefore, the first object of the present invention is to
OLa, 03 series glasses have high viscosity and therefore can be directly molded to provide roughness.

Further, the second object of the present invention is to
2. To provide an optical glass with a high refractive index and low dispersion of Sid-40 to Sid-60.

(Summary of the Invention) The present inventors have discovered that B203-RO-La containing 5I02
As a result of intensive research on 203 series glass, conventional SiO
,,As the content increases, the vitrification area decreases and the liquidus temperature increases, but in particular, the weight ratio of 5i02/B2O3 is selected between 11 and 30, and the proportions of each component are limited as shown below. By doing so, we discovered that it was possible to obtain a glass that had the desired high viscosity and optical constants, had a not too high liquidus temperature, was stable against devitrification, and had excellent chemical durability. He came up with an invention.

The component composition of the glass according to the present invention will be shown below on a weight basis.

5i02: 12-35% B2O3° 9-29% S i02 / B2O3: 1. t~ 3BaO2
0-48% La2O3: 31-50% (preferably 35-50%) The reason why the composition range of each component of the optical lath according to the present invention is limited as described above is as follows.

If 5102 exceeds 35%, the desired optical performance cannot be obtained, and if it is less than 12%, the high viscosity targeted by the present invention cannot be obtained.

If B2O31d exceeds 29%, the desired optical performance cannot be obtained, and if it is less than 9%, the tendency for devitrification increases and a stable glass cannot be obtained.

If BaO exceeds 48%, the desired optical performance cannot be obtained.
If it is less than 20%, unmelted substances will occur and a homogeneous glass cannot be obtained.

When La2O31d exceeds 50%, the liquidus temperature becomes high and at the same time it becomes unstable against devitrification. If it is less than 31%, the desired optical performance cannot be obtained and chemical durability deteriorates.

When the 5in2/B2O3 ratio exceeds 3, the meltability of the glass deteriorates7, the liquidus temperature increases, and it becomes difficult to obtain a homogeneous glass.

Conversely, if it is less than 11, a sufficiently high viscosity for direct molding, which is the object of the present invention, cannot be obtained.

In addition to the above-mentioned four essential components, the optical glass of the present invention may contain Az, o3. Ga
203s Ir+203. Y2O3, Yb20: 1°G
d2O3, TlO2, ZrO2, GeO2, Nb2O5
,'ra2o6,WO2,MgO,Cab, 8rO,
ZnO1pbo, R20, Na2O, L+20, As
20'3.5b203, F, etc. can be contained.

In particular, when Y2O3, ZrO2 or Nb2O5 is contained in a total of 3 to 30%, nd=1. '75~1.82
A glass is obtained which exhibits a refractive index of .nu.d=40 and a dispersion of .nu.d=40 to 50.

The glass according to the present invention uses corresponding oxides, hydroxides, carbonates, nitrates, fluorides, etc. as raw materials for each component, weighs them out in the desired proportions, adds a fining agent if necessary,
Thoroughly mix the powder to form a blended raw material, and heat it at 1300°.
It can be produced by placing it in an electric furnace heated to 1500'C to 1500'C, melting it, and stirring the fining agent to make it uniform.The resulting molten glass is poured into a mold of a specific shape, directly press-molded, and then slowly cooled. . Of course, glass gobs can also be obtained using conventional methods.

(Example) shows.

Table 1 (Effects of the Invention) According to the present invention, the viscosity during molding is as high as 40 poise or more, the optical constants are nd = 1.65 to 1.82, Vd = 40-60, and devitrification is achieved. Optical glass is obtained which is stable against water and has excellent chemical durability.

Applicant: Nippon Kogaku Kogyo Co., Ltd. Agent Takao Watanabe

Claims (1)

[Claims] Consists of the following composition on a weight basis, and has a refractive index nd of 165 to 1.
82. A directly moldable optical glass characterized by having an Abbe number νd of 40 to 60. 5l (J2: 12-35% 1320, ° 9-29% 5iCI2/B2O3: 1.1-3 BaO: 20-48% La20.: 31-50%