JPS58125632A - Glass composition suitable for manufacture of light converging lens - Google Patents

Abstract

PURPOSE:To provide the titled glass composition capable of controlling the concentration distribution of ions produced in the course of ion exchange diffusion process, giving a proper refractive index distribution, and containing Li2O, Na2O, K2O, Al2O3, B2O3, TiO2, SiO2 and ZrO2 at specific ratios. CONSTITUTION:The objective composition contains 3-16mol% Li2O, 0-20mol% Na2O, 0-22mol% K2O, 0-10mol% Al2O3, 0-25mol% B2O3, 2-25mol% TiO2, 45-65mol% SiO2 and 0-10mol% ZrO2, provided that Na2O+K2O is 5-22mol%, Al2O3+1/2B2O3+TiO2 is 2-25mol% and Al2O3+B2O3+ TiO2+SiO2+ZrO2 is 70-83mol%. The composition may further contain 0-3mol% CaO, 0-3mol% MgO, 0-3mol% SrO, 0-3mol% BaO, 0-3mol% ZnO, 0-5mol% PbO, 0-4mol% La2O3, 0-2mol% Sb2O3, 0-2mol% As2O3, and 0-2mol% WO3 as stabilizing additives.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses an ion exchange diffusion method, for example, to exchange cations in a glass composition with cations in a molten salt by immersing the glass composition in a high humidity molten salt bath. The present invention relates to glass compositions suitable for diffusion to create refractive index gradients in the glass composition.

It is well known that ion exchange diffusion is used as a manufacturing method for light focusing lenses. This method uses, for example, elements that relatively increase the refractive index in the glass composition (for example, heptavalent alkali metal ions such as O8+++Li+).
containing an element (for example, KINa) that, when replaced with the above element, relatively reduces the refractive index
) containing /71 by immersing it in molten salt (e.g. KNO3, NaNO3).
Exchange and dispersion of seeds takes place. This method causes the refractive index in the glass to change continuously (in the niJ example, the refractive index decreases from the center to the outside).
We can obtain the elements A' and A with -9 parts.

This kind of cumulative moon has the shape of a round bar, ? t.

A material with a parabolic refractive index distribution expressed as refractive index at distance (refractive index of optical axis, r: distance from optical axis, A: refractive index distribution constant) is used as a light-focusing lens. be done. The performance of these lenses is similar to that of spherical lenses, allowing images to propagate through the lens. In order to increase the brightness of the lens, it is desirable that the maximum angle of incidence of light θmaX (hereinafter referred to as the aperture angle) with respect to the optical axis be large.

Its opening 1] Angle θmax is sinθmax
(nO: refractive index of the optical axis Δn: difference in refractive index between the optical axis and the outermost shell).

Therefore, in order to detect the aperture 1-1 angle, the refractive index difference △n(
3) A large value is considered a must-trade. In addition, when used as a lens with an aperture (1 angle or more), the focusing characteristics are very important, so even if △n is large, a lens with a thick parabolic distribution of refractive index is used. It is said that

As a light-focusing lens that is currently not being produced commercially, Kalast Tokuko Sho 5 /-2/, which contains T10 in the color of Tokko Sho 1 @, 1'-37737,! ;9 'lノYOK
There is also glass containing CS+. The glass that obtains the refractive index distribution using Te is open] I angle (θmax) is J00
It is extremely large at ~30' and has the advantage of widening the light collection area. Because of the large difference, white light is not focused on seven points. Therefore, it has the disadvantage that its use is limited to 1lj-wavelength light.

Glasses that use Os to obtain a refractive index gradient have the advantage that they have smaller chromatic aberrations and can be used with white light compared to lenses that contain Tl, but the aperture [-1 angle is small ( It has the disadvantage of being less than 0.It is difficult to incorporate a large amount of CS+ into the glass, and even if it is included in a large amount, it does not necessarily provide a light year (Il) refractive index distribution that is good as a flux lens. This is because glass containing C80 cannot be obtained.
It has the second disadvantage of being very expensive due to the high cost of raw materials.

It is easier to include a large amount of L1+ in glass than to include C80 in large quantities in glass, and
]”- and C80 have the possibility of obtaining a larger Δn than the equivalent molar glass in the glass.

However, just like glass containing a large amount of aS+, glass containing a large amount of Li+ does not necessarily have △n
However, it is not always possible to obtain a lens that is attractive and has a good refractive index distribution.

The refractive index distribution during ion exchange diffusion is a function of the ion exchange diffusion conditions (preparation time, salt composition) and the diffusion coefficient (composition, temperature).

Therefore, it is necessary to control ion exchange diffusion in order to obtain an appropriate refractive index distribution. However, what has the greatest influence on the distribution of ions related to the refractive index distribution (<3) is the change in the interdiffusion coefficient due to the change in the glass composition accompanying ion exchange diffusion.

Therefore, even if ion exchange diffusion is performed on a glass composition that is not suitable for the composition of light focusing lens +11, it will still have a high △n and a good refractive index distribution for focusing light to the periphery. cannot be obtained. Of course, by changing the ion exchange treatment conditions, it is possible to obtain a refractive index distribution that satisfies the light focusing conditions to some extent at the center of the cylinder.

However, in the case of a glass composition having a composition suitable for a light focusing lens, the glass composition is limited to a small part of the center of the cylindrical rond. It becomes necessary to remove the peripheral portion of the cylinder with poor optical properties by etching with a hydrofluoric acid solution or the like.

This operation not only complicates the production process, but also reduces the refractive index difference n between the center and the outer grain.
It has the disadvantage of reducing the divergence aperture angle.

For example, a glass for manufacturing optical elements having a refractive index gradient using a concentration gradient of Ll+ is disclosed in Japanese Patent Application Laid-open No. 3-1-1998. According to experiments conducted by the inventors of the present invention, as shown in Comparative Example A/ in Table 1, a glass having the composition mentioned above, for example, L120Na20 M containing /2 mJ% of L120.
gO-8i02 thread glass /mmφ glass rod Il
Perform ion exchange diffusion with NaNO3 molten salt at O''C (1)
When the immersion time is 1.5 hours, a refractive index difference of △n-/39×10-4 is obtained between the optical axis and the blood on the surface of the glass, but the refractive index distribution is Since the glass rod is not concentrated, it is not possible to obtain a refractive index distribution that can be used as a condensing lens.
When the molten salt is subjected to ion exchange diffusion for several hours, a part of the center of the cylinder can have a refractive index distribution that can be used as a light focusing lens. However, if the peripheral portion of the lens is reduced to a point where it can be used as a light converging lens and cannot be used as a condensing lens, it decreases to Δn=30×10−4, and the angle of the opening is 7.00. Moreover, this operation is 7 times the diameter of the glass rod.
It is an operation that removes more than 10% of the total amount, so it has the disadvantage of poor production efficiency.

(7) As mentioned above, the distribution of ions related to the refractive index during ion exchange diffusion changes depending on the diffusion coefficient of the exchanged ions in the glass composition.

Up until now, cations with a valence of 2 or more have little to do with the rate of change in the overall refractive index distribution during ion exchange diffusion)
It was expected that it would be slightly ineffective against. This is because the influence of these ions is secondary to ion-exchange diffusion, since the concentration distribution of those ions themselves in the diffusion zone is absent or negligible if present. This is because it was thought to be a natural trait.

For example, divalent alkaline earth metal ions enter the glass and slow down the overall diffusion. Glass containing alkaline earth metals has the disadvantage of poor production efficiency because it takes a long time to obtain an appropriate refractive index distribution through ion exchange diffusion.

However, it was surprisingly found that certain multivalent ions have a large effect on the concentration distribution generated by -3 diffusion of alkali ions (Li+).

(Z) The present invention includes Li2O and TlO2 in the glass composition, and essentially does not contain divalent alkali +--1- metal ions, so that Li2O and TlO2 are generated during ion exchange diffusion. The purpose is to control the concentration distribution of ions and obtain a suitable refractive index distribution.

Another object of the present invention is to provide a light-focusing lens that uses inexpensive raw materials and has less chromatic aberration than a glass lens containing Tl+.

The present invention has the following composition Li2O3~/z in mol%.

Na2O0-22, K2O0~, 2- or 205-. 22, B2O30~, 23, Al2
O30-10, TiO2, 2-25 and Al2O3+/
/-2B203-1-Ti022~. 25゜ZrO20
~10,5102 lS~OtsuSka-) B2030 Al2
Ion exchange KJ characterized by containing O3+ZrO2+TiO2+5j-0270-43:
,-.

The gist of this invention is a glass composition suitable for manufacturing a light-focusing lens.

Next, the reasons for limiting the glass composition of the present invention will be described.

As a refractive index distribution forming ion, Ll+ is present in the glass as L1
It can be contained in the form of 20 UH in the range 3 to 1%/zmO. If the content is less than 3 m01% in the form of L120, the difference in refractive index obtained by ion exchange diffusion will be too small to be of practical use. If the Li2O content exceeds /1 moe%, the devitrification of the glass will be severe, resulting in poor millet productivity.

Na, 20, or 20 is a necessary component to facilitate the melt-forming of glass and to increase the ion exchange rate by -1-. If the Na2O content is less than 3 m01%, the ion exchange rate will be significantly reduced, and if it exceeds 2.2 m01%, the chemical durability will be low. Therefore, Na2O is 20 to 10! ;-,! Contains -2m01%. but,
It is better that 20 not coexist with Na2O, but it may coexist to some extent. This means that the glass containing both is NaNO3
When performing ion exchange diffusion treatment with Na + salt, the content should be 20
However, if KNO3 or the like is subjected to ion exchange diffusion treatment with a + salt, the Na2O contained will have an adverse effect on the ion exchange.

Therefore, it is preferable that Na2O or Ni2O as the glass component be under the same pressure as the cations in the ion exchange medium.

B2O3 can be contained up to 23m01% to facilitate melting of the glass, but if it exceeds this, the chemical durability will be reduced.

Al2O3 can be contained up to 1%/Om to suppress the phase separation characteristics of the glass, but if it exceeds this, it becomes difficult to melt the glass.

ZrO2 can be contained in order to suppress the phase separation characteristics and improve the chemical durability of the glass in the same way as Al2O3. However, exceeding this value makes it difficult to melt the glass.

Although the reason for this is not well understood, TlO2 is an important component in forming an appropriate refractive index gradient, and it is desirable to optimally adjust its content by adjusting the amount of L120 and its Shinkin Bank.
When Li2O content is 3 m01%, TlO2 is 2 m01
% is necessary, and as the Li2O content increases, Tl
It is also good to increase the O2 content, and the ratio of both is TiO2
It is desirable that /LiO2≧0.3.

It is possible to contain TiO2 at a maximum of 23 m01%, but if this is exceeded, devitrification becomes severe, making it difficult to mold the glass. Also, glass containing TlO2 is B2
When it coexists with O3 and Al2O3 in large quantities, it tends to devitrify easily. Therefore, the amount of TiO2 that can be contained when coexisting with B2O3 and Al2O,5 is TiO2 + Al2
O3+//, 2B203 is 2~. 2smo1% range u
++ Toru.

5i02 is the main component forming glass, ljmo
If it is less than e%, the devitrification property and chemical durability will be significantly lowered. Again≦! If m01% is exceeded, the content of the refractive index gradient forming oxide and other oxides will be limited, and the refractive index difference that can be obtained will be small, making it difficult to obtain a lens with a 1-angle aperture that is sufficient for practical use. becomes impossible.

B2O3+Al2O3+TiO2+ZrO2+5i02
is a composition that forms a network,” 810 of 2.
70~g3mO1 for the same reason as the upper and lower content limits in 2.
% range.

In addition, stabilizing additives can be added within a range that does not impair the characteristics of the present invention. The reason for this limitation of the composition range will not be explained in detail, but if the addition is within the above range, it will not adversely affect the properties of the focusing lens obtained using the composition of the present invention.

Embodiment F will be described below.

Examples Table 1 shows the following raw materials: silica sand, lithium carbonate, sodium carbonate (or potassium carbonate), titanium dioxide, boric acid, boric acid, Zirconium oxide, alumina, and magnesium carbonate were weighed and mixed to give 3 kg each as glass, melted in a platinum crucible at 230'C for 76 hours without leaving any bubbles or striae, and cast into blocks. It got cold. Use a hollow drill to drill 7J from this glass block.
After hollowing out a glass shell with a diameter of 1/2 mm and polishing it, 1. IJum (or nitric acid)
IJum) They were immersed in molten salt for a predetermined period of time and subjected to ion exchange diffusion to obtain light-focusing lenses of practical examples /~// and comparative examples/~. The effective visual field area ratio and aperture angle of these lenses were measured. As is clear from Table 7, the lenses of the examples in which the glass having the composition of the present invention was ion-exchanged were almost equivalent to or better than the lenses of the comparative examples after a short ion exchange treatment, compared to the lenses of the comparative examples. It has performance.

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Claims (1)

[Scope of Claims] (]) A glass composition suitable for manufacturing a light-focusing lens, characterized in that it contains a composition in the following range in mol%. LigO3~/Otsu Na2O0-22 20 0~22 and Na2O+ 205N22 A12030~10 B2'03 0~. 2S Ti02 2~2yokatsuAlz03+//, 2B203+TiO22~, 1
tS102 DaS-Otsu5 zro2 o~10 and Al2O3+Bp03+Tj-02+5j-02+
Zr0270-Z3 (1) (2) Glass composition Ca00-31Mg00-3. according to claim 1, wherein the following composition is further added as a stabilizing additive in mol% to the above composition. SrOO~3. Ba0O
~3゜ZnOO~J, PbOO~j+La2O30-1
1,8b2030~-2 + A3203 0~ノ+W
03 0~. 2