JPS5891044A - Glass composition for light converging lens - Google Patents

Abstract

PURPOSE:To obtain a glass composition with small chromatic aberration and a favorable refractive index distribution suitable for a light converging lens by adding SiO2, Li2O and K2O as basic components and by restricting the Na2O content to a very small amount. CONSTITUTION:A glass composition contg. 45-68% SiO2, 2-12% Li2O, 6- 20% K2O (Li2O+K2O=12-26%), 1-12% TiO2, 0-18% MgO, 0-14% CaO, 0-15% ZnO, 0-14% SrO, 0-11% PbO (MgO+CaO+ZnO+SrO+PbO=8-18%), 0-12% B2O3, 0-5% Na2O and a specified amount of BaO, Al2O3, La2O3, Y2O3, Sb2O3, As2O3 or ZnO2 as a stabilizer is melted to inexpensively obtain a glass composition for a light converging lens.

Description

[Detailed description of the invention] The present invention relates to glass compositions suitable for light-focusing lenses.

Methods for manufacturing light-focusing lenses by ion exchange are widely known.

This involves kneading glass containing specific cations and immersing it in a molten salt containing ions that can modify the glass with different ions, allowing ion exchange between the ions in the glass and the ions in the molten salt. It is something you can do.

Depending on the combination of glass and molten salt, along with ion exchange, the refractive index of the periphery may be higher or lower than the initial glass.

In the case of general light-focusing lenses, hindsight is preferred. That is, when the glass to be ion-exchanged is immersed in molten salt, the refractive index of the glass gradually decreases from the deep part toward the periphery. The most common shapes of glasses for ion exchange are flat and cylindrical. Especially for cylindrical lenses, the shape of the refractive index distribution is formed by ion exchange (3) n=no(/-ar2) (no=
refractive index at the center of the glass, r: distance from the center, a: constant)
A good lens can be obtained if the above conditions are satisfied. In order to form such a refractive index distribution, the ions contained in the glass include heptavalent cations such as Tl, Rb, Cs,
Lj- etc. are used. Typically, glasses containing such cations are ion-exchanged in a molten salt containing K or Na.

The shape of the refractive index distribution of the glass ion-exchanged in this way does not necessarily satisfy the above-mentioned formula, and for a certain range of appropriately chosen glass compositions, distribution is obtained.

Regarding the conventional glass composition, the glass containing Tl has a difference in refractive index between the center and the periphery (△n
), but it has the disadvantage that it has large chromatic aberration and is limited to use with monochromatic light if the lens length is long.

The chromatic aberration of glass containing O8 is much greater than that of Tl (4'
) Although it is small and can be used with white light, it has the disadvantage that it is difficult to obtain a material with a large difference in refractive index, and its raw material is very expensive.

The chromatic aberration of glass containing Ll is even smaller than that of glass containing 06tt@, and its usefulness has been noted from an early stage, but it has not yet been possible to obtain a practical composition necessary for light-focusing lenses. ) There was no. The reason for this is that it is difficult to obtain a good refractive index distribution shape and that it is difficult to mold the glass.

That is, conventional glass containing Ll contains a relatively large amount of NagO, which is ion-exchanged in a molten salt containing Ha or K, which causes the glass to become cloudy (devitrification) during glass molding.
However, it was extremely difficult to produce it industrially.0 To be more specific, the production of glass for light-focusing lenses involves weighing predetermined raw materials,
Mix / 300 ~ / 4 (quartz B at 30'C, acupoint 11
The coarse-grained glass obtained is transferred to a platinum lumbo and main melting process is carried out. In this melting step, stirring is performed to prevent the melt from becoming homogeneous.

The temperature of the sufficiently homogeneously molten glass is slowly lowered to a flow rate that makes it easy to pour it into the mold. Normal descent time is 7
It takes around 0 hours, and the flow rate of pouring into the mold is qoo~
1000"C. During this cooling process, the glass that was homogeneous at high temperatures may precipitate opaque crystals as the flow descends. This is called devitrification, and the glass that has undergone such devitrification may cannot be used as a glass for light-focusing lenses.

This tendency is especially strong in glasses containing Ll, and it has been difficult to manufacture them industrially.

An object of the present invention is to provide a glass that is suitable as a material for light-focusing lenses and that can be manufactured without devitrification.

Another object of the present invention is to provide a light-focusing lens glass with small chromatic aberration.

Another object of the present invention is to provide a glass that can obtain a large difference in refractive index by ion exchange.

Another object of the present invention is to provide a glass that provides a good refractive index distribution.

Another object of the present invention is to provide a light-focusing lens glass with good durability.

Still another object of the present invention is to provide a glass with which a light-focusing lens can be manufactured at a lower cost.

The glass of the present invention has 5102 r L as a basic component]
-20+ contains 20, and Na 20 is not included at all, or even if added, it is limited to a very small amount.

In detail, the glass of the present invention has a mol% of L1202~/
2, K2Oz~20 However, Li2O10/20//
, ~2A, B2O30~/,2, MgOO~
/J', Ca00~i, ZnOO~/j,
SrOO~l, PbOO~//, where MgO
10aO+ZnO+SrO+PbOza~/za, 5i0
2 11! r~6g, Tio2 /~/-? Consists of.

In addition to the main components listed above, the glass of the present invention contains Na2O0 to 5% by mole in order to stabilize the properties of the glass. , Ba00
□/ + A12030~0.3 + Lapo3 0
~0-3 ry2o3 o~O,j, 5b203
o~0. ! ; , AS2030~o,s,zro2
Components such as o to 1 can be added.

(7) Next, the reason for limiting the composition of the glass of the present invention will be described.

5102 is a glass network structure forming component, and Ge! ;m
If o is less than 1%, the weather resistance of the glass decreases, the viscosity decreases, and the devitrification increases. If the gmO content exceeds 1%, the melting temperature of the glass will increase, making it difficult to obtain a homogeneous glass. Therefore, in the present invention, the content is set within the range of 75 to gmoe%.

B2O3 is an effective component that lowers the viscosity of glass. Up to 1% of /J m0 can be introduced into the glass by replacing it with 5i02 without losing the features of the present invention. 12
When m01% is exceeded, the glass viscosity decreases, which adversely affects the refractive index distribution, which is also suitable for ion exchange reactions.

TlO2 is a necessary component to improve the refractive index distribution shape obtained by ion exchange and to obtain a refractive index difference corresponding to the contained L ]-20N. This content is 72m0
If it exceeds 1%, the devitrification property increases and the phase separation tendency of the glass also increases. At least /mol1% or more is required, but the upper limit is /J m01% (J') In particular, if it is 1'mO1% or more F, it is stable against the devitrification phase separation property of glass.

Among divalent metal oxides, MgO, Zn○l SrOI
PbO can be contained alone or in combination of two or more types as a glass component.

These oxides are used to raise the melting point of the glass, but if the total amount is less than 01%, the shape of the refractive index distribution will be distorted. Moreover, when the total amount exceeds /Irm01%, the devitrification property of the glass increases. Mg for devitrification.

is the seventh most stable and can be contained up to /gmoe%, but SrO and CaO contain /l1moe%,
zno is/! ;mo1% is the limit of content.

PbO can be used to improve devitrification, but //m
If O exceeds 1%, the diffusion rate of ions in the glass will slow down, causing deformation of the glass during the ion exchange diffusion reaction.
gOI The total of OaO, ZnO, SrO, and PbO is g~
/ f m01% is necessary from the viewpoint of devitrification of the glass.

L120 is a component that determines the refractive index difference. Normally, the refractive index difference required for a light-focusing lens is 30×l0-4 or more.”
In order to achieve this, it is necessary to contain 2 moe% or more of Li2O. However, Li2O is i
If the content exceeds 2 moe%, the devitrification and phase separation of the glass will increase, making molding difficult. Preferably 3 mo1
%~lrmOe%te.

K2O is an important component of the present invention. It is preferable to include a large amount of K2O from the viewpoint of devitrification and bipartite phase. 4 m0
If it is less than 1%, the devitrification property of the glass is poor, and the diffusion rate of ions in the glass is also slowed down, which has an adverse effect on the refractive index distribution. However, if it exceeds 20 moe%, the chemical durability of the glass will deteriorate significantly, so it must be within the range of 20 moe%.

Preferably, it is /　/　m01% to 20m01%.

The total J1 amount of L120 and 20 is #-2tmO1%, preferably /za~, 2tmO1%.

When the amount of L i 20 + K 20 is less than 1% of lmO, the phase separation property of the glass increases rapidly. Moreover, if it exceeds 23 mo1%, the chemical durability of the glass will deteriorate.

In addition to these basic glass components, for the purpose of defoaming properties and refractive index adjustment during glass melting, Na2OO~s (preferably H O~3), Ba0o~/, A12o30~0-,
j+La2O30~0.3+Y2O30-0-! ;
+5b203 0-0. ,! ; , A, 5203 (
1-0,3, ZrO20~/ can be contained either singly or in combination of two or more.

Example: Approximately 7 kg of pickled silica sand for optical glass, lithium carbonate, potassium carbonate, magnesium fermentation, and titanium oxide were used as test grade, and other raw materials were used as reagent grade, so as to have the composition shown in Table 1. After weighing, grinding, stirring, and mixing to obtain a glass of The mixture was melted for 3 hours while stirring in a platinum crucible. Afterwards/up to 100°C approx./°C
The temperature was slowly lowered at a rate of 1/min, and the mixture was poured into a mold and slowly cooled.

A glass iron with a diameter of 7 mm was made from the obtained glass lump, and ion exchange diffusion was performed by immersing it in 5go''C potassium nitrate.Ion exchange diffusion treatment was performed for about 7.20 hours. In order to evaluate the characteristics of the glass rondo as a light focusing lens, the effective image transmission area ratio and the difference in refractive index between the central axis and the outer periphery of the lens were measured.

In addition, the original glass lump was crushed to create small pieces of glass with a size of 70 to 47 Meson Yuno, placed in a platinum boat, heated at 200'C for 70 minutes, and cooled down to 700°C. Hold in a thermal gradient furnace at ~/100″C for 2 hours,
The growth rate of the devitrification was determined by observing the devitrification generated on the glass surface using an optical microscope. The results of these measurements are shown in column F of Table 7.

In addition, as a comparative example, a relatively large amount of M
Regarding conventional lithium glass contained in
A light-focusing lens was obtained by immersing "Iit' of C" in an acid potassium salt bath for 7.20 hours, and the refractive index difference, effective transmission area ratio of image, and maximum devitrification growth rate were determined in the same manner as in "-". It was measured. The results are shown in the right column of Table 1.

As is clear from the results in Table 1, (/2
) Part / Table No. / Table (Continued) Lithium-containing glass with the composition is much more devitrified than conventional lithium glass, and therefore has superior formability.
Moreover, it can be seen that it is not possible to obtain lens performance equivalent to or better than that of conventional lenses.

(/S)

Claims (1)

[Claims] ]) The following composition in mol%, 5io2: ps-Og% Li, 2o: , 2 to 72% to 20: Oto to 20% L120 10 to 20: /Otsu to 2t% Tj- 02:
/~/, 2% MgO: 0~7g% CFj, O: O~/q% zno: o~/S% 5rO70~/g% pbo: o~7% Mgo+cao+zno+sro+pbo: J'
A glass composition suitable for a light focusing lens, characterized in that it has ~/g% B2O3: 0~/-% Na2O: 0~5%. 2. In claim 1, the composition in mol% is: Li2O: 3~g% to 20: //~+20% MgO: 70~/za% TiO2: 2~g% 5102: ,93~ A glass composition characterized in that the ratio of Niza% Li2O+ is within the range of 20:/lr to 1. 3) In claim 1, the stabilizing additives include the following oxides (4% lucidity): BaQ: 0-7% Ae2o3: o-o, s% La2o3: 0-0. j% Y20.3: 0-0.3% 5b2o3F o-o, s% AS203: 0-0. ! % ZrO2: 0 to 7%.