JP2002029773A - Glass composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass composition having 1.67 to 1.72 refractive index (nd) and high water resistance and weather resistance, which does not contain lead, cadmium or the like harmful for the environment or which does not contain barium generally used for high refractive index glass and which is softened at a low temperature and suitable for mold press forming. SOLUTION: The glass composition contains by mass%, 18 to 28 SiO2, 13 to 25 B2O3, 35 to 50 (SiO2+B2O3), 5 to 15 Nb2O5, 0 to 2 Ta2O5, 5 to 15 (Nb2O5+ Ta2O5), 1 to 6 TiO2, 0 to 3 ZrO2, 3 to 8 (TiO2+Zr02), 5 to 15 La2O3, 0.5 to 3 Al2O3, 15 to 25 ZnO, 0 to 10 CaO, 0 to 8 SrO, 20 to 30 (ZnO+CaO+SrO), 0 to 10 Li2O, 0 to 8 Na2O, 0 to 5 K2O and 8 to 15 (Li2O+Na2O+K2O).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention is suitable for a material for a mold press-molded lens which does not contain, for example, lead and cadmium which may be harmful to health, and barium which is often used for optical glass having a high refractive index. It relates to a glass composition.

[0002]

2. Description of the Related Art Conventionally, a lens system comprising a large number of lenses having a concave and convex spherical surface has been used for an optical device such as a camera. For the purpose of eliminating the need for a lens polishing step and further improving the resolution, the use of mold press-molded aspherical lenses has been aimed at, and some of them have already been put to practical use. Under such a trend, development of a glass composition more suitable for non-abrasive mold press molding is being actively carried out today as well as improvement of a mold.

[0003] Regarding the glass composition for mold press molding, initially, it is possible to perform mold press molding at a low temperature while maintaining the optical constant of the glass employed in the conventional spherical lens system. A great deal of effort was put into the development of low-temperature softening glass compositions, and as a result, not a few compositions containing lead. However, recently, in consideration of the environment and health, a glass having a composition that does not contain harmful substances such as lead and cadmium and further does not contain barium has been desired.

Suitable for mold press molding, PbO and Cd
A glass composition that does not contain O (hereinafter, in the present invention, all elements and compounds are represented by elemental symbols and represented in the form of an oxide according to the convention of oxide glass) is disclosed in patent gazettes. In the present invention, the refractive index (nd)
In the range of 1.67 to 1.72, the following glass compositions are disclosed, for example, even if the composition includes SiO ₂ in the glass-forming oxide.

[0005] Japanese Patent Application Laid-Open No. 4-92834 discloses SiO
_Two-B_TwoO_Three-La_TwoO_Three-Gd_TwoO_Three− (ZrO_Two−
Nb_TwoO_Five-TiO_TwoAll of these components have 0%
System is shown, but here Gd_TwoO_ThreeAnd Ba
O plays an important role as an essential component. JP 5
No. 2017743 discloses SiO 2_Two-B_TwoO_Three-La
_TwoO_Three-ZnO-R_TwoO (R is an alkali metal element)
As shown, a large amount of La is used to increase the refractive index._TwoO
_ThreeAs an essential component, while Nb_TwoO_FiveAnd TiO _TwoIs included
Not. JP-A-6-32631 discloses that SiO 2
_Two-GeO_Two-TiO_Two-Nb_TwoO_Five-R_TwoO (R is a
Glass-forming oxidation)
The object is SiO_TwoAnd GeO_TwoAnd B_TwoO_ThreeIs not included.

Japanese Patent Application Laid-Open No. 6-107425 discloses Si
O_Two-B_TwoO_Three-TiO_Two-Nb_TwoO_Five-BaO-R_Two
O (R is an alkali metal element) type is shown, but Ba
O as an essential component (1-45%), La_TwoO_ThreeNot include
Composition. Japanese Patent Application Laid-Open No. 6-148662 discloses SiO 2
_Two-B_TwoO_Three-La_TwoO_Three-Al_TwoO_ThreeSystem, JP-A-8-
No. 59281 discloses SiO_Two-B_TwoO_Three-ZnO-based
And Nb as an essential component_TwoO_FiveAnd TiO_Two
Does not contain JP-A-8-104536 discloses that
SiO_Two-TiO_Two-ZrO_Two-K_TwoO-Li_TwoOR
O (R is a divalent metal element) system, JP-A-8-175841
The gazette states that SiO_Two-TiO_Two-Nb_TwoO_Five-WO_Three−
BaO-Na_TwoO-based compositions are shown, but these systems
Then B _TwoO_ThreeAnd La_TwoO_ThreeIs not an essential ingredient,
Besides, TiO_TwoThe amount is quite large. JP-A-8-2592
No. 57 discloses SiO_Two-B_TwoO_Three−Li_TwoO-ZnO-
La_TwoO_ThreeJP-A-11-29338 discloses SiO.
_Two-B_TwoO_Three-ZnO-RO (R is a divalent metal element)
Yes, the former is La_TwoO_ThreeThe amount of alkali and the total amount of alkali
, The latter is Nb_TwoO_Five, La_TwoO_ThreeAnd TiO
_TwoIs an extremely small content.

Although it is unknown whether it is for molding or not, it is disclosed in JP-A-10-265238 that SiO _2-
The B ₂ O ₃ —ZrO ₂ —Nb ₂ O ₅ system is shown,
Looking at the composition range, Nb ₂ O ₅ is considerably large at 31 to 50%, and La ₂ O ₃ is not an essential component. In addition, SiO ₂ —B ₂ O ₃ —TiO ₂ —Nb ₂ O ₅ —Pb
O (TiO ₂ , Nb ₂ O ₆ , and PbO all contain 0%) are reported, but B ₂ O ₃ is 5 to 11%.
% And ZnO are also limited to 0 to 8%.

[0008]

The glasses described in these publications all have the optical constants satisfying the target values, but some of the compositions having good weather resistance are difficult to mold press molding. The most important is the softening property at low temperature and the value of the sag point (temperature corresponding to the maximum point of the thermal expansion curve, the same applies hereinafter) determined from the thermal expansion curve of glass is not necessarily low enough to meet the user's requirements. On the other hand, among compositions that emphasize low-temperature softening properties, there are many compositions in which the weather resistance of molded products is difficult. One of the causes is that the composition system or composition range disclosed in the above publication has emphasized dispersion (often represented by Abbe number) as well as refractive index as an optical constant to be possessed by glass. Sometimes the system or composition range has been restricted.

However, in an optical system using laser light (effectively single-wavelength light) as a light source as in a recent optical recording apparatus, dispersion is not always important as an optical constant to be provided in the glass for a lens. Rather, it is natural that the refractive index is in a desired range, but it does not contain components that are inexpensive but may be harmful to the environment as constituent components, and has a softening temperature as low as possible to reduce the burden on the press molding mold. In addition, a glass having high water resistance and high weather resistance is desired. From this point of view, the known glass compositions are not always satisfactory.

It is an object of the present invention that the refractive index (as nd) is in the range of 1.67 to 1.72, and it is easy to be generally used for lead or cadmium which may be harmful to the environment, and also for high refractive index glass. It is an object of the present invention to provide a glass composition suitable for mold press molding which does not contain barium, has high water resistance and weather resistance, and is easily softened at low temperatures.

[0011]

Means for Solving the Problems [Configuration] To solve the above problems
As a result of intensive studies, the glass composition according to the present invention
In terms of mass, SiO_Two 18-28, B_TwoO_Three
 13-25, (SiO_Two+ B _TwoO_Three) 35-50,
Nb_TwoO_Five 5-15, Ta_TwoO_Five 0-2, (Nb_Two
O_Five+ Ta_TwoO_Five5-15, TiO_Two 1-6, Z
rO_Two 0-3, (TiO_Two+ ZrO_Two) 3-8, L
a_TwoO_Three 5-15, Al_TwoO_Three 0.5-3, ZnO
 15-25, CaO 0-10, SrO 0-8,
(ZnO + CaO + SrO) 20-30, Li_TwoO
0-10, Na_TwoO 0-8, K_TwoO 0-5, (Li
_TwoO + Na_TwoO + K_TwoO) 8-15%
Have achieved the above object.

[Effects] The glass components are limited to the above composition range for the following reasons.

[0013] SiO_TwoAnd B_TwoO_ThreeAre both glass mesh
It is a component and strengthens the glass network.
Is basically no difference between the two. Therefore a stable gas
In order to obtain a glass, both naturally have a lower limit.
You. However, the effect on the viscosity of the obtained glass is different.
With SiO_TwoTemperature increases the temperature at which the glass softens
Get higher, B_TwoO_ThreeMore easily softens at low temperatures
You. On the other hand, B_TwoO_ThreeIf the amount is too large, the water resistance of the glass
And weather resistance are impaired. Considering the effects of both
The composition range was determined after the_TwoIs 18
~ 28% by mass, B _TwoO_ThreeIs preferably from 13 to 25% by mass.
And the combined amount of both (SiO_Two+ B_TwoO_Three) Is 35-50 quality
Most preferably, the amount is limited to the range of%.

Nb ₂ O ₅ , Ta ₂ O ₅ , TiO ₂ , Zr
O ₂ and La ₂ O ₃ are so-called intermediate oxides. In the glass of the present invention, O ₂ and La ₂ O ₃ were mainly selected as components that impart a high refractive index without significantly impairing the stability of the glass against devitrification. Although it is a component, it is a component that also exerts an effect on imparting water resistance and weather resistance. The glass composition according to the present invention is limited to the above specific range for the following reason.

When the content of Nb ₂ O ₅ is less than 5% by mass, it is difficult to obtain a desired refractive index, and when it exceeds 15% by mass, Nb ₂ O ₅ is lost due to the content of other components. Not only adversely affects the permeability, but also acts to slightly inhibit the low-temperature softening property. Therefore, 5 to 15% by mass is appropriate.

Ta_TwoO_FiveIs Nb_TwoO_FiveCan be partially replaced
And contributes to increasing the refractive index and stability of the glass. I
If too much, the refractive index was too large
Damage the stability of the glass against devitrification and increase the density.
There is a possibility that it will be broken. From these points to 0 to 2% by mass
I should stop. The combined amount of both (Nb_TwoO_Five+ Ta_TwoO
_Five) Is suitably from 5 to 15% by mass.

TiO ₂ is particularly effective for imparting a high refractive index, and also has an effect of lowering the liquidus temperature of glass to suppress devitrification. However, beyond a certain limit, the glass tends to rapidly devitrify. From these points, the amount of TiO ₂ is 1
To 6% by mass.

[0018] TiO is ZrO ₂ as a trend of action effect
Similar to ₂ , but containing a small amount of ZrO ₂ has the effect of suppressing the devitrification by increasing the viscosity of the glass. However, if it is too large, there is a possibility that the low-temperature softening property may be adversely affected. Therefore, the content should be limited to 3% by mass or less. The total amount (TiO ₂ + ZrO ₂ ) is 3 to 8% by mass.
Is limited to

La ₂ O ₃ is an essential component of a high-refractive, low-dispersion optical glass.
It is a high-refractive-index-imparting component replacing aO.
It can be introduced into glass without impairing devitrification. Its content is also effective from the viewpoint of imparting water resistance, and is desirably 5% by mass or more. The upper limit is determined by the relative relationship with other high refractive index imparting components, and Nb ₂ O ₅ , Ta
_{When 2} O ₅ , TiO ₂ and ZrO ₂ are in the above range,
15% by weight is appropriate.

Al ₂ O ₃ is also an intermediate oxide, and its inclusion in a small amount is particularly effective for suppressing devitrification and increasing water resistance and weather resistance. However, when the amount is too large, the refractive index of the glass is lowered, and the low-temperature softening property is impaired. Therefore, 0.5 to 3% by mass is appropriate.

ZnO, CaO and SrO are glass network modifying oxides, and their extents vary depending on the content ratio of network forming oxides, intermediate oxides and alkali metal oxides which are typical network modifying oxides. It is generally considered to be an effective component for the water resistance and weather resistance of glass. Among them, ZnO is effective not only for enhancing the chemical durability, but also for improving the melting property and imparting a low melting property, and at the same time, also effective for preventing an increase in the thermal expansion coefficient of the obtained glass. Component. Therefore, the divalent component (ZnO, CaO
And SrO) should be used the most. However, when the amount is too large, it becomes difficult to obtain a glass having a desired refractive index, and the tendency of devitrification also increases. Therefore, the content of 15 to 25% by mass is preferable within the composition limit of components other than divalent as defined in the present invention. The effects of CaO and SrO are similar to those of ZnO, and both are considered to be complementary components of ZnO. Therefore, the content of CaO and SrO should be kept small.
O is desirably 8% by mass or less. From these viewpoints, the total amount of the divalent components (ZnO + CaO + SrO) is 20 to 30.
% By weight is preferred.

Li_TwoO, Na_TwoO and K_TwoO is not
Effective for improving the melting property of glass and softening at low temperatures
Components, and their small content is desirable. But individual
The content is high, though the degree varies depending on each component.
If broken, the water resistance and weather resistance of the glass will deteriorate,
And increase the coefficient of thermal expansion, which is undesirable.
No. From these viewpoints, Li_TwoO is 10% by mass or less, N
a_TwoO is 8% by mass or less, K_TwoO is preferably 5% by mass or less.
And their total amount (Li_TwoO + Na_TwoO + K _TwoO) is
It should be kept in the range of 8 to 15% by weight.

In addition to the above components, while maintaining the refractive index of the glass in the range of 1.67 to 1.72, a small amount (10% by mass in total) is mainly used for improving the chemical properties of the glass.
It is possible to add the following components). However, the composition change by such addition should be included in the present invention as long as the composition of the basic component is within the scope of the present invention.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, examples of the glass composition according to the present invention will be described. The glass composition according to the present invention,
It was produced as follows. A platinum crucible is charged with a predetermined amount of an oxide (B ₂ O ₃ uses H ₃ BO ₃ as well as oxide), a hydroxide, and a raw material mixture composed of a carbonate, and intermittently at 1,300 ° C. for 1.5 hours. With stirring. afterwards,
The melt was poured out onto a previously heated stainless steel plate, placed in an electric furnace set at about 30 ° C. above an assumed glass transition point, turned off, and allowed to cool in the furnace.

After cooling, the presence or absence of crystal precipitation was examined, and those having no crystal precipitation were prepared to have a sample having the same optical surface as the lens, and subjected to a weather resistance test. The refractive index was measured using the polished sample. On the other hand, a rod-shaped sample was prepared from a part of the glass, and a 5
The coefficient of thermal expansion was measured at a heating rate of ° C./min. Also,
The glass transition point and the yield point were determined from the thermal expansion curve according to a standard method. Tables 1 and 2 show composition examples and physical property examples of the glass thus implemented. Of these, the glasses in Table 1 are Examples 1 to 6 of the glass according to the present invention, and the glasses in Table 2 are Comparative Examples 7 to 10 of the glass outside the present invention. However, the present invention is limited only to the composition in Table 1. It is not something to be done.

[0026]

[Table 1]

[0027]

[Table 2]

(Remarks) (1) The numbers of each component in the composition column in Tables 1 and 2 are% by mass calculated from the batch raw materials. (2) Tg is the glass transition point and Tc is the yield point, all of which are determined from the thermal expansion curve by an ordinary method. (3) The coefficient of thermal expansion (α) is an average value between 100 ° C and 300 ° C. (4) nd is the refractive index of the d-line at room temperature. (5) The devitrification was determined by the degree of precipitation of crystals when the melt was poured out onto a heated stainless steel plate and cooled by a predetermined method. When any crystal was recognized, it was evaluated as x, and when it was not recognized, it was evaluated as ○. (6) The weather resistance of a sample having an optical surface comparable to that of a lens was placed in a thermo-hygrostat at 60 ° C. and a relative humidity of 90%.
Measure the degree of cloudiness on the surface after holding for 00 hours. Commercially available lead heavy flint glass (688/312, so-called SF8)
In comparison with 優 れ, those superior to those were evaluated as ほ ぼ, those almost equivalent to those of ○, and those clearly inferior to those of ×. Incidentally, an optical glass having good weather resistance has good water resistance in a practical sense.

[0029]

As described above, according to the glass composition of the present invention, lead and other elements which may be harmful to the environment and health, and furthermore, are frequently used in optical glasses having a high refractive index. It is possible to easily and inexpensively provide an optical glass having a refractive index (as nd) of 1.67 to 1.72 without containing barium, and also has a devitrification resistance sufficient for practical use. Optical glass material for mold press molding used for optical systems using laser light as its light source, because it has heat resistance, water resistance and weather resistance, and has a coefficient of thermal expansion of 100 × 10 ⁻⁷ / ° C. or less and softens at low temperatures. Can be suitably used.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Shoji Nakamura 1006 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. F term (reference) 4G062 AA04 BB05 DA04 DB02 DB03 DC04 DD01 DE04 DF01 EA01 EA02 EA03 EA10 EB01 EB02 EB03 EC01 EC02 EC03 ED01 EE01 EE02 EE03 EF01 EF02 EF03 EG01 FB01 FB02 FC01 FC02 FC03 FD01 FE01 FF01 FG03 FG04 FH01 FH02 FH03 FJ01 FK03 FK04 JJ01 H01H10H01 H01H10H01 KK03 KK06 KK07 KK10 MM02 NN02 NN29

Claims (1)

[Claims] 1. The method according to claim 1, wherein in mass%, SiO ₂ 18-28, B ₂
O ₃ 13-25, (SiO ₂ + B ₂ O ₃ ) 35-5
_{0, Nb 2 O 5 5~15,} Ta 2 O 5 0~2, (N
b ₂ O ₅ + Ta ₂ O ₅ ) 5 to 15, TiO ₂ 1 to
6, ZrO ₂ 0 to 3, (TiO ₂ + ZrO ₂ ) 3 to
8, La ₂ O ₃ 5 to 15, Al ₂ O ₃ 0.5 to 3, Z
nO 15-25, CaO 0-10, SrO 0
8, (ZnO + CaO + SrO) 20-30, Li ₂
O 0-10, Na ₂ O 0-8, K ₂ O 0-5,
_{(Li 2 O + Na 2 O} + K 2 O) glass composition comprising 8% to 15%.