JP2021014377A - Optical glass - Google Patents

Abstract

To provide an optical glass free from fusing to a mold during press molding, capable of preventing degradation of mold in press molding, while satisfying properties required for optical glass.SOLUTION: An optical glass contains 30 to 80 mol% of TeO2, 5 to 50 mol% of MoO3, 0.1 to 30 mol% of Li2O+Na2O+K2O, 0 to 10 mol% of TiO2+Al2O3, 0 to 10 mol% of CaO+BaO+SrO, and 0 to 10 mol% of SiO2+B2O3.SELECTED DRAWING: None

Description

The present invention relates to optical glass.

Optical glass with a high refractive index has been conventionally used for optical communication lenses such as optical modules, optical pickup lenses for various optical disk systems such as CDs and DVDs, and imaging lenses for camera-equipped mobile phones, digital cameras, film cameras, etc. Has been done.

These optical glasses can be obtained by forming a molten glass into an ingot and then cutting and polishing a glass material cut into an appropriate size to obtain a desired shape, or by polishing the above glass material and then applying it to the surface. A method of transferring the surface of a mold to glass by placing a glass material on a precision-processed mold and heat-pressing it (mold press), or a glass material formed into droplets by dropping molten glass from the tip of a nozzle. Is produced by a method of molding and pressing after polishing or without polishing.

The optical glass produced by the above method is sealed and fixed to a metal holder such as a Ni—Fe alloy or stainless steel via a sealing glass, or adhered and fixed to a plastic holder via a resin. Used for various lens applications.

By the way, in recent years, optical elements have tended to have higher functionality and smaller size, and optical glass is required to have a higher refractive index (specifically, a refractive index nd of 1.60 or more).

Further, the optical glass is required to have the following characteristics in addition to the refractive index.
(1) Do not devitrify when forming molten glass into ingots or droplets (specifically, the liquidus temperature is low).
(2) The glass transition point is low in order to reduce the deterioration of the die during mold pressing.
(3) The glass should not be fused to the die during mold pressing.
(4) The glass surface has weather resistance that does not deteriorate even when used for a long period of time.

As an optical glass satisfying the above required characteristics, a glass system containing B ₂ O _3- La ₂ O _3- ZnO as a main component has been proposed. (See Patent Document 1)

Japanese Unexamined Patent Publication No. 2005-015302

The glass transition point of the B ₂ O _3- La ₂ O _3- Zno O-based glass is 598 ° C. or higher, and it is necessary to further lower the glass transition point in order to extend the life of the die by the mold press. For example, if the glass transition point is lowered to 400 ° C. or lower, it can be expected that the life of the mold will be dramatically extended and the productivity of the optical glass will be improved.

However, Li ₂ O, Na ₂ O, K ₂ O and the like, which are alkali metal oxides (R ₂ O) having an effect of lowering the glass transition point, are added to the B ₂ O ₃ −La ₂ O ₃ − ZnO based glass. When a certain amount or more is contained, alkali metal ions (R ⁺ ) in the glass diffuse into the inside of the mold in contact from the glass surface during mold pressing, and a strong reaction layer is formed by mutual reaction. This causes a problem that the glass is fused to the mold.

Further, in order to reduce the melting cost, glass that can be melted at a lower temperature is desired. However, the liquidus temperature of the glass is 850 ° C. or higher, and in order to lower the melting temperature, it is necessary to further lower the liquidus temperature. For example, if the liquidus temperature is lowered to 800 ° C. or lower, the melting cost can be significantly reduced.

From the above, it is possible to achieve both the extension of the life of the mold for the mold press by lowering the glass transition point and the prevention of fusion between the glass and the mold while satisfying the required characteristics of the optical glass. At the same time, it is to provide an optical glass capable of reducing the melting cost.

As a result of diligent efforts, the present inventor, if the glass composition range is regulated as follows, even if the glass transition point is lowered by containing an alkali oxide, the glass surface and the mold surface due to the alkali oxide It has been found that the reaction layer due to the mutual reaction of the above is less likely to be formed, and the glass and the mold are less likely to be fused, and the present invention is proposed. That is, the optical glass of the present invention, in molar _{percentages, TeO 2 30~80%, MoO 3} 5~50%, Li 2 O + Na 2 O + K 2 O 0.1~30%, TiO 2 + Al 2 O 3 0~10 %, CaO + BaO + SrO 0 to 10%, SiO ₂ + B ₂ O _{30 to} 10%. Here, "Li ₂ O + Na ₂ O + K ₂ O" means the total amount of Li ₂ O, Na ₂ O and K ₂ O. "TiO ₂ + Al ₂ O ₃ " means the total amount of TiO ₂ and Al ₂ O ₃ . "CaO + BaO + SrO" means the total amount of CaO, BaO and SrO. “SiO ₂ + B ₂ O ₃ ” means the total amount of SiO ₂ and B ₂ O ₃ .

The interaction not clear the details of the mechanism of the reaction layer is hardly caused by, but is intensive investigation, at the moment, the main component forming a skeleton of glass, from the ionic radius of small B ₂ O ₃ mainly ions It is presumed that this is because the movement of alkali metal ions, which can move relatively freely inside the glass, can be hindered by changing to a combination of TeO ₂ and MoO ₃ having a large radius.

The optical glass of the present invention is characterized in that the main component forming the skeleton of the glass is a combination of TeO ₂ and MoO ₃ (TeO _2- MoO ₃ system glass).

Specifically, the optical glass of the present invention contains both TeO ₂ , which is a component that increases the refractive index and lowers the glass transition point, and MoO ₃ , which is a component that lowers the glass transition point, as essential components. It is possible to significantly reduce the glass transition point while maintaining a high refractive index, and it is possible to achieve a long life of the mold during mold pressing. Further, by using a combination of TeO ₂ and MoO ₃ having a large ionic radius as the main component forming the skeleton of the glass, the movement of alkali metal ions that can move relatively freely inside the glass is hindered and the alkali oxide is formed. It is characterized in that the glass and the mold are hard to be fused without forming a reaction layer due to the mutual reaction between the glass surface and the mold surface.

That is, the optical glass of the present invention, in molar _{percentages, TeO 2 30~80%, MoO 3} 5~50%, Li 2 O + Na 2 O + K 2 O 0.1~30%, TiO 2 + Al 2 O 3 0~10 %, CaO + BaO + SrO 0 to 10%, SiO ₂ + B ₂ O _{30 to} 10%. The reason for limiting the glass composition range of the optical glass of the present invention as described above will be described. In addition, the following% display means that it is mol% unless otherwise specified.

TeO ₂ is a component that significantly expands the vitrification range by forming a glass skeleton, remarkably suppresses the precipitation of devitrified particles, and increases the refractive index. It is also a component that lowers the transition point of glass. The content of TeO ₂ is 30 to 80%, preferably 35 to 70%, more preferably 40 to 65%, still more preferably 45 to 60%. When the content of TeO ₂ is large, it becomes difficult to obtain glass having high hardness and high transmittance. On the other hand, when the content of TeO ₂ is small, it becomes difficult to obtain the above effect and it becomes difficult to vitrify.

MoO ₃ is a component that greatly expands the vitrification range by forming a glass skeleton. It is also a component that lowers the glass transition point. The content of MoO ₃ is 5 to 50%, preferably 10 to 40%, more preferably 15 to 35%, still more preferably 20 to 30%. When the content of MoO ₃ is large, the glass becomes unstable and devitrified particles are likely to precipitate. On the other hand, when the MoO ₃ content is low, the glass transition point rises and the life of the mold press die is shortened. In addition, it becomes difficult to hinder the movement of alkali metal ions that can move relatively freely inside the glass, and the glass and the mold are easily fused.

Li ₂ O, Na ₂ O and K ₂ O are components that lower the glass transition point, but are also components that significantly lower the refractive index. The content of Li ₂ O + Na ₂ O + K ₂ O is 0.1 to 30%, preferably 1 to 25%, more preferably 5 to 20%, still more preferably 10 to 15%. As the content of Li ₂ O + Na ₂ O + K ₂ O increases, the weather resistance deteriorates.

Li ₂ O is a component that lowers the glass transition point without increasing the coefficient of thermal expansion. The content of Li ₂ O is preferably 0 to 30%, more preferably 0.1 to 25%, still more preferably 1 to 20%, and particularly preferably 5 to 15%. If the content of Li ₂ O is too high, the weather resistance will deteriorate.

Na ₂ O is a component that lowers the glass transition point. The Na ₂ O content is preferably 0.1 to 30%, more preferably 1 to 25%, still more preferably 3 to 20%, and particularly preferably 5 to 15%. If the Na ₂ O content is too high, the weather resistance will deteriorate.

K ₂ O is a component that lowers the glass transition point. The K ₂ O content is preferably 0% to 20% is more preferably 0.1% to 15%, more preferably 1-10%, particularly preferably 1-5%. When the content of K 2 _O is too large, weather resistance is deteriorated.

TiO ₂ and Al ₂ O ₃ are components that significantly enhance weather resistance. The content of TiO ₂ + Al ₂ O ₃ is 0 to 10%, preferably 0.1 to 8%, more preferably 1 to 6%, still more preferably 2 to 4%. If the content of TiO ₂ + Al ₂ O ₃ is too high, the glass transition point rises.

TiO ₂ is a component that significantly enhances weather resistance and also significantly enhances the refractive index. However, it is also a component that significantly precipitates devitrified substances caused by TiO ₂ and lowers the transmittance. Therefore, the content of TiO ₂ is preferably 0 to 10%, more preferably 0.1 to 8%, still more preferably 1 to 6%, and particularly preferably 2 to 4%.

Al ₂ O ₃ is a component that improves the hardness and weather resistance of glass. However, it is a component that significantly reduces the refractive index. Therefore, the content of Al ₂ O ₃ is preferably 0 to 10%, more preferably 0.1 to 8%, still more preferably 1 to 6%, and particularly preferably 2 to 4%.

CaO, BaO and SrO are components that widen the vitrification range, but are also components that reduce the refractive index. Therefore, the content of CaO + BaO + SrO is 0 to 10%, preferably 0.1 to 8%, and more preferably 1 to 5%. The contents of CaO, BaO and SrO are preferably 0 to 10%, more preferably 0.1 to 8%, and further preferably 1 to 5%, respectively.

SiO ₂ and B ₂ O ₃ are components that form the skeleton of glass, but are poorly compatible with TeO ₂ and MoO _3, and are components that raise the liquidus temperature. Further, it is a component that improves the hardness and weather resistance of glass, but is a component that remarkably lowers the refractive index and remarkably raises the glass transition point. Therefore, the content of SiO ₂ + B ₂ O ₃ is 0 to 10%, preferably 0.1 to 8%, more preferably 1 to 6%, still more preferably 2 to 5%.

SiO ₂ is a component that forms the skeleton of glass, but has poor compatibility with TeO ₂ and MoO _3, and is a component that raises the liquidus temperature. Further, it is a component that remarkably improves the hardness and weather resistance of glass, but is a component that remarkably lowers the refractive index and remarkably raises the glass transition point. Therefore, the content of SiO ₂ is preferably 0 to 10%, more preferably 0.1 to 8%, still more preferably 1 to 6%, and particularly preferably 2 to 5%.

B ₂ O ₃ is a skeleton component of glass, but has poor compatibility with TeO ₂ and MoO _3, and is a component that raises the liquidus temperature. Furthermore, it is a component that raises the glass transition point. Therefore, the content of B ₂ O ₃ is preferably 0 to 10%, more preferably 0.1 to 8%, still more preferably 1 to 6%, and particularly preferably 2 to 5%.

In addition to the above components, other components may be introduced as optional components. The content of the components other than the above components is preferably 10% or less, more preferably 5% or less, still more preferably 3% or less, in total amounts, from the viewpoint of accurately enjoying the effects of the present invention. Particularly preferably, it is 1% or less.

ZnO is a component that forms the skeleton of glass. The ZnO content is preferably 0 to 5%, more preferably 0 to 3%, still more preferably 0 to 1%, and particularly preferably 0 to 0.1%. When the content of ZnO is increased, devitrified particles due to ZnO are likely to be precipitated, and as a result, the liquidus temperature rises and the melting cost rises.

La ₂ O ₃ is a component that forms the skeleton of glass. The content of La ₂ O ₃ is preferably 0 to 5%, more preferably 0 to 3%, and even more preferably 0 to 1%. When the content of La ₂ O ₃ is increased, devitrification lumps caused by La ₂ O ₃ are likely to be deposited.

Nb ₂ O ₅ is a component that significantly increases the refractive index. The Nb ₂ O ₅ content is preferably 0 to 5%, more preferably 0 to 3%, still more preferably 0 to 1%, and particularly preferably 0 to 0.1%. As the content of Nb ₂ O ₅ increases, devitrification lumps caused by Nb ₂ O ₅ tend to precipitate. In addition, it becomes difficult to obtain glass having high transmittance.

WO ₃ is a component that increases the refractive index and suppresses the precipitation of devitrified particles caused by Nb ₂ O ₅ and TiO ₂ . However, it is also a component that significantly precipitates devitrified substances caused by WO ₃ and lowers the transmittance. Therefore, the content of WO ₃ is preferably 0 to 5%, more preferably 0 to 3%, still more preferably 0 to 1%, and particularly preferably 0 to 0.1%.

P ₂ O ₅ is a component that stabilizes glass, but is a component that deteriorates water resistance. Therefore, the content of P ₂ O ₅ is preferably 0 to 10%, more preferably 0.1 to 5%, and even more preferably 1 to 3%.

The glass having the above composition can have a refractive index nd of 1.60 or more, a glass transition point of 400 ° C. or less, and a liquid phase temperature of 800 ° C. or less. In addition, it is difficult to fuse with the mold, and good weather resistance can be obtained.

The refractive index nd is preferably 1.60 or more, more preferably 1.70 or more, still more preferably 1.80 or more. If the refractive index is low, it becomes difficult to obtain a more sophisticated and compact optical element.

The glass transition point is preferably 400 ° C. or lower, more preferably 350 ° C. or lower, still more preferably 320 ° C. or lower, and particularly preferably 300 ° C. or lower. If the glass transition point is high, mold press molding at a low temperature becomes difficult, and it becomes difficult to suppress deterioration of the mold.

The liquidus temperature is preferably 800 ° C. or lower, more preferably 750 ° C. or lower, and even more preferably 700 ° C. or lower. When the liquidus temperature is high, the glass tends to be devitrified during the molding process. In addition, the melting temperature becomes high.

Hereinafter, the optical glass of the present invention will be described in detail based on examples.

Tables 1 and 2 show Examples (Samples Nos. 1 to 11) and Comparative Examples (Samples Nos. 12 to 14) of the present invention, respectively.

Each sample in Tables 1 and 2 was prepared as follows.

First, a glass raw material was prepared so as to have the composition shown in the table, and melted at 1000 ° C. for 2 hours using a platinum crucible. After melting, the melt was poured onto a carbon plate to prepare a glass bulk, and after annealing, a sample suitable for each measurement was prepared.

The obtained sample was evaluated for refractive index nd, liquidus temperature, glass transition point, fusion of glass and mold, and weather resistance. The results are shown in Tables 1 and 2.

The refractive index nd is indicated by a measured value with respect to the d line (587.6 nm) of the helium lamp using a refractive index meter.

The liquidus temperature was measured as follows. First, each sample is crushed and washed to a size of 300 to 500 μm, placed in a platinum boat, transferred to a temperature gradient furnace at 700 to 1200 ° C., held for 1 hour, and made of platinum from the temperature gradient furnace. I took out the boat. After that, the glass was taken out of the platinum boat. The sample thus obtained was observed with a polarizing microscope, the precipitation point of the crystal was measured, and this was taken as the liquidus temperature.

The glass transition point was obtained by extending the straight lines of the low temperature region and the abnormal expansion region of the expansion curve obtained by the linear expansion coefficient measuring device (TMA), and determining the temperature corresponding to the intersection as the glass transition point.

Whether or not the glass and the mold were fused was determined as follows. Each columnar sample with a diameter of 5 mm and a thickness of 5 mm is sandwiched between two tungsten carbide (WC) molds with a diameter of 15 mm and a thickness of 5 mm, and while heating at a glass transition point of + 50 ° C., a load of 20 KPa is used for 10 Pressed for minutes. On the surface of the mold after pressing, the adhesion state of the glass component was observed, and the one in which the adhesion of the glass component was not observed was evaluated as "◯", and the one in which the adhesion of the glass component was observed was evaluated as "x".

For weather resistance, prepare a sample with one side mirror-polished, leave the sample in a high temperature and high humidity environment of 60 ° C. and 90% for 1000 hours, and then observe the sample surface with a stereomicroscope to see if there is any deterioration. Was evaluated. Those with no alteration were marked with "○", and those with alteration were marked with "x".

As is clear from Tables 1 and 2, the sample No. In each of the samples 1 to 11, the refractive index nd was as high as 1.612 or more, the liquidus temperature was as low as 752 ° C. or less, and the glass transition point was as low as 309 ° C. or less. In addition, no fusion between the glass and the mold was observed, and no deterioration was observed on the sample surface after the high temperature and high humidity test, so that the weather resistance was also excellent.

On the other hand, sample No. No. 12 had a refractive index of 1.583, and the weather resistance of the glass was poor.

In addition, sample No. In No. 13, the glass transition point was 510 ° C., and the liquidus temperature was 840 ° C.

Furthermore, the sample No. In No. 14, fusion of the glass and the mold was observed.

Claims (3)

In molar _{percent, TeO 2 30~80%, MoO 3} 5~50%, Li 2 O + Na 2 O + K 2 O 0.1~30%, TiO 2 + Al 2 O 3 0~10%, CaO + BaO + SrO 0~10%, SiO An optical glass characterized by containing ₂ + B ₂ O _{30 to} 10%. The optical glass according to claim 1, wherein the refractive index nd is 1.60 or more. The optical glass according to claim 1 or 2, wherein the glass transition point is 400 ° C. or lower.