JPS58181740A - Glass composition for light converging lens - Google Patents

Abstract

PURPOSE:To manufacture a glass composition having reduced chromatic aberration and a large difference in refractive index by adding specified amounts of Cs and Li to an SiO2-base glass composition for a light converging lens and by subjecting the composition to ion exchange in molten KNO3. CONSTITUTION:A glass composition for a light converging lens contg. Cs as ion for providing a refractive index and Li as a metal for forming a refractive index distribution is refined. The principal components of the glass composition are 50-68% SiO2, 0-10% B2O3 (SiO2+B2O3=50-72%), 0-7% Al2O3, 0-20% ZnO, 0-15% MgO, 4'20% Cs2O, 2-12% Li2O, 0-18% K2O, 0-18% Na2O (Cs2O+ Li2O+K2O+Na2O=15-30%) and 0-7% PbO, and CaO, SrO, BaO, La2O3, TiO2, ZrO2, SnO2, As2O3 and Sb2O3 are also contained. The glass composition is subjected to ion exchange in molten KNO3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a glass composition for a light-focusing lens that is suitable for obtaining a large refractive index difference with low chromatic aberration by an ion exchange method.

It is said that the light focusing lens can be obtained by the ion exchange method. A component capable of ion exchange is contained in 0 glass described in Japanese Patent Publication No. J/-2/39'1, etc., and the ions are ion-exchanged in a molten salt containing potassium nitrate or sodium nitrate, etc. The refractive index changes from the surface toward the depths.

When a thin glass rod with radius r is immersed in molten salt, the heptavalent cations in the glass and the monovalent cations in the molten salt exchange ions with each other, resulting in a cylindrical shape as shown in Figure 1. A refractive index distribution based on the concentration gradient is generated from the center of the thin glass rod to the periphery, and the refractive index at a point at a distance of r from the center is /rL fL.

Arc - Oki (/-arc) (1): Refractive index at a point r from the center m: Refractive index a at the center Expressed by a constant determined by glass and molten salt.

Also, the brightness of the light focusing lens is as shown in Figure 2, where the maximum incident angle is θ, IC) CK -R2・θ2...
(-) K: constant, R: given by the radius of the light-focusing lens, and the larger the maximum incident angle, the brighter the light-focusing lens becomes.

Further, θ is determined mainly by adjusting the refractive index difference caused by ion exchange, as shown below.

θoc Mete-7・・・・・・・・・・・・・・・(3) It is known that thallium, cesium, or lithium is effective as the valent metal included in the glass for forming the refractive index distribution. ing. Glass containing these metals is ion-exchanged with K or Na in a molten salt. Conventionally, in order to obtain a high refractive index difference (Δ4), Tl glass, which has a high refractive index contribution due to one ion-exchanged molecule, is effective, and Tl glass has been preferably used. For example, with glass containing Tl, a bright lens with a refractive index difference of J#x1o-3 and a maximum angle of incidence of about 0o0 can be obtained by ion exchange.

However, due to the large chromatic aberration, the light source was limited to monochromatic light, and its uses were also limited.

On the other hand, conventional glass containing Os has chromatic aberration compared to Tl.
Since the refractive index λ is extremely small, about 10, it is possible to use white light as a light source, but the difference in refractive index λ is 4-. 3. ! ; 9×10 −3 , and the maximum incident angle is extremely small, at most 0, so the brightness is not necessarily sufficient, and its uses are also limited. The reason for this is that a large refractive index difference cannot be obtained unless a large amount of Os is contained in the glass due to ion exchange/because the refractive index contribution rate per molecule is low. This is because even if a large amount of aS is contained in glass, it is not necessarily possible to obtain a light-focusing lens with a refractive index difference commensurate with the content, as shown in FIG. Also, there is a large amount of a in the glass.
Inclusion of S causes problems in terms of durability of the glass, raw material cost, and occurrence of devitrification during melting.

More specifically, when only aS for forming a refractive index distribution is included as the alkali metal, the ion exchange rate is extremely slow and a practical lens cannot be produced.

Next, even if aS is included for forming the refractive index and 20 is included as another alkali oxide, it is also not possible to make a light-focusing lens with a high refractive index difference as shown in Comparative Examples/ and C in Table 1. . When aS is included as a refractive index forming ion and Na2O is included as another alkali metal (20
Although the refractive index difference obtained is slightly larger than in the case of >, no significant effect can be expected.

Glass containing Li as a refractive index distribution forming metal is also considered to have almost the same characteristics as Os.

The present invention provides a glass composition that simultaneously contains aS and Ll as refractive index distribution forming components, improves the above-mentioned drawbacks, and produces a bright light-focusing lens with low chromatic aberration and a high refractive index difference.

With Cjs as the refractive index distribution forming component, L within a certain range
By incorporating K and performing ion exchange in a molten salt of potassium nitrate, it was possible to produce a light-focusing lens with small chromatic aberration and a large difference in refractive index.

The glass composition range defined in the present invention is as follows (unit: mo1%) Si02: 30-61, B2O3: 0-10
e5i020B2O3: 30~72, Al
2O3: 0~7, ZnO: 0~-〇, Mg
O: 0~/j.

pbo: o to 7 is the main component, and the following components can be included as stabilizing components within a range that does not impair the basic properties of the glass.

CaO: O~λ, SrO: 0-2, BaO:
O~λ.

La2O3: ON2, TiO2: 0~ko.

zrO2: 0~/, SnO2:0A-l, As2O3
;O~/, 5b203: 0~/ The reason for this limitation will be explained below.

becomes more likely to occur. If it exceeds 6 g%, other components necessary for glass formation will be limited, making it impossible to obtain the necessary refractive index difference.

Further, the melting temperature is 11,160° C. or higher, resulting in defects such as undissolved matter, bubbles, and striae during melting. Preferably 52~
It is 67%.

B2O3 is also a glass-forming substance and is the most effective flux for lowering the melting temperature of glass, but it tends to volatilize during melting, which increases the variation in glass composition and reduces the shape of the refractive index distribution due to ion exchange. It is necessary to keep it at 70% or less, and preferably 7% or less, since it causes defects such as deterioration or reduction of the ion exchange rate and generation of cracks on the glass surface during ion exchange.

The preferred range of 5i020B2O3 is 52 to 70%.Okl2o3 improves the durability and devitrification of the glass, and can be contained in a range of 7% or less.

ZnO is effective in improving the durability of the glass, facilitating its melting, and improving the refractive index profile shape of the lens. However, if it exceeds 20%, devitrification increases. The preferred range is 5-76%.

MgO is also used for the same reason as ZnO, but it has a higher melting temperature than ZnO and is more likely to devitrify, so it is 73%
It is necessary to keep it below.

Preferably it is 73% or less.

R20 greatly influences the ion exchange rate. The ion exchange rate increases as the content increases.

It is also effective in improving the tendency of glass to devitrify.

However, if it exceeds 11%, other components contributing to the refractive index will be suppressed and durability will decrease, so in the present invention, it is specified to be 11% or less. 0Cs20, which is preferably O~/O%, is a main component forming the refractive index distribution, and in order to obtain a large refractive index difference, it is necessary to contain a large amount of C15BO. 1
If it is less than %, the necessary refractive index difference cannot be obtained. Also, if it exceeds -0%, the total R20 content including cs2o will increase and the durability will decrease! -, 10%. The preferred range is 3-#%.

When L120 is contained in combination with C620, it acts synergistically to further increase the difference in refractive index of Cs2O obtained by ion exchange. Therefore, naturally Cs2O
As the content increases, it is preferable to increase the Li2O content accordingly.

L120 required for Cs2041% is 2%. CF3
It is preferable to increase L120 as the R20 content increases, but if the total amount of R20 increases significantly, the durability of the glass will decrease, so Li2O should be increased by /-%.
It is necessary to do the following.

Preferably it is 2 to 77%.

Although Na2O does not particularly affect the refractive index difference or the refractive index distribution shape, it is effective in lowering the melting temperature of glass and lowering the ion exchange temperature.

Therefore, the content can be up to 71% without deteriorating the durability, but it is preferably 0 to 1%.

As mentioned above, if the total amount of K R2C1 is too large, the durability of the glass will decrease, so in the present invention, C1520
t Li2Op R20, Nano (7) The total amount is /
! ; C must be selected within the range of ~36%, and an additional 20%
It is desirable that it be within the range of ~3t1%.

PbO is an effective component that improves the devitrification of glass7.
% can be contained as a limit.

Exceeding this will reduce the ion exchange rate and deteriorate the refractive index distribution shape.

In addition, glass stabilizing components can be included within the following ranges that do not change the basic properties of the glass.

CaO: 0-j, SrO: ON2, BaO
: ONJLa203: 0-2, TiO2:
0~jZr02: 0~/r5n02: 0~
/ + As2O3: 0~/.

5b2o3: o~/ Example 2 gg of silicon dioxide, 1 g of zinc oxide, 2 t of potassium carbonate. Weighed 9 g of cesium nitrate and 26 l g of lithium carbonate, mixed them homogeneously in a 2071 plastic container, and then melted them in a 7400°C melting furnace using a 21 quartz crucible. Perform 7 melts, striae,
After becoming a homogeneous glass without bubbles, the temperature was lowered to 1030''C at a rate of 100cl) for 7 hours.

Then vertical 230mm, horizontal 00mm, height 25m
It was cast into a mold of 1.5 m and slowly cooled to room temperature in a slow cooling furnace.

The glass that had been slowly cooled was cut out using a diamond cutter to obtain a round bar with a diameter of about 0 mm.

Next, use a spinning furnace to spin this round rod into a thin glass rod with a diameter of about 1/2 mm! Melting potassium nitrate at 70"C After ion exchange for 2g hours in a Buddhist altar, period length -J, 7mm
We were able to obtain a light focusing lens with a good refractive index distribution.

After cutting and polishing this lens to j, j mm, the maximum angle of incidence was measured and found to be /J, da0.

Similarly, the center refractive index, the difference in refractive index between the center and the periphery, and the maximum angle of incidence of light-focusing lenses obtained with various glass compositions were measured.

As a comparative example, a light-focusing lens was manufactured by melting, molding, and spinning glass that did not contain Li, 20 in the same manner as above, and then ion-exchanging the glass.

The results are shown in Table 1.

In addition, Example B in the table was melted at 1330°C and cast into a mold at 7020°C.

As is clear from Table 1, when cs2o and Li2O coexist in a glass within a certain amount range, a bright lens containing 0820 alone and with a much larger difference in refractive index than a glass that does not contain L120 can be produced. I can do it.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a light-focusing lens according to the present invention and its refractive index distribution, and FIG. 2 is a side sectional view showing a state in which a light ray travels through the light-focusing lens according to the present invention. . Table 1 (1) Ion exchange time is 1n diameter/value for processing Onon glass rod - Table 1 (2) 1II Figure 2

Claims (1)

[Claims]: 3 Si02: so-+, r, in mol%. B2O3: 0~10°5i02+B2O3: ! ;0~72 A1203:0~7°zno: o~-〇. MgO: 0~/3°as2o; ll-ro. Li2O: 2~/, 2°K2O: O~/za. Na2O: 0~/g. 0820+L120+ to 20+Na2O: /! ;
-31゜pbo: o ~ 7 as one essential component [97, and further as a stabilizing component 7 as OaO
: 0~. 2, SrO: 0-. 2. BaO:
0-2. La2O3: 0~ko, TlO2: O-2, ZrO2:
0~/+5n02: 0~/, AS203:
A glass composition suitable for a light-focusing lens manufactured by an ion exchange method, comprising O~/, 5b20s: 0~l.