JP7134396B2 - optical glass - Google Patents

Description

The present invention relates to optical glasses.

In recent years, electronic parts and the like have been miniaturized. As a result, high-precision ultraviolet cameras used for quality control of electronic circuits, optical fibers, and semiconductor materials, and ultraviolet lasers that form electronic circuits on silicon wafers are required. ing. 2. Description of the Related Art Conventionally, silica glass, which has a high transmittance for ultraviolet rays (wavelengths of approximately 350 nm or less), has been used for lenses used in ultraviolet lasers and the like (see, for example, Patent Document 1).

JP-A-4-305035

However, since silica glass has a high glass transition point and a high softening point, there is a problem that it is inferior in press moldability and it is difficult to obtain a desired lens shape.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide an optical glass having high ultraviolet transmittance and excellent press-moldability.

The optical glass of the present invention contains, in mass %, SiO ₂ 40 to 75%, B ₂ O ₃ 1 to 30%, Al ₂ O ₃ 0 to 15%, RO 0.1 to 10% (R is Mg, Ca, at least one selected from Sr, Ba and Zn), Li ₂ O 0.1 to 10%, Na ₂ O + K ₂ O 0.5 to 15%, ZrO ₂ 0 to 3%, F ₂ 0 to 5% It contains Sb ₂ O ₃ and does not substantially contain Sb 2 O 3 . Here, " _Na2O +K2O" means the _total content of _Na2O and _K2O . In the present invention, a high UV transmittance is achieved by limiting the content of _SiO2 , which increases the UV transmittance, to 40% by mass or more, and the total content of alkali components, which reduce the UV transmittance, to 25% by mass or less. is doing. In addition, the content of RO (R is at least one selected from Mg, Ca, Sr, Ba and Zn) that lowers the glass transition point is 0.1% by mass or more, and the total content of alkali components is 0. Excellent press moldability is achieved by restricting the content to 6% by mass or more. Note that "substantially free of Sb ₂ O ₃ " means that it is not intentionally contained as a raw material, and objectively, the content of Sb ₂ O ₃ is less than 0.1%. Say.

The optical glass of the present invention preferably further contains La ₂ O ₃ +Nb ₂ O ₅ +Bi ₂ O ₃ +WO ₃ from 0 to 0.05% by mass. Here _, " _{La2O3 + Nb2O5 +} Bi2O3 _{+ WO3} " means the _total content of _{La2O3 , Nb2O5 , Bi2O3} and _WO3 .

The optical glass of the present invention preferably further contains TiO ₂ of 100 ppm or less and Fe ₂ O ₃ of 50 ppm or less by mass %.

The optical glass of the present invention preferably has a refractive index (nd) of 1.45 to 1.55. Note that "nd" is the refractive index for the d-line.

The optical glass of the present invention preferably has a glass transition point of 550° C. or lower.

The optical glass of the present invention preferably has a softening point of 700° C. or lower.

The optical glass of the present invention preferably has a thickness of 1 mm and a transmittance of 50% or more at a wavelength of 270 nm.

The optical glass of the present invention preferably has a thickness of 1 mm and a transmittance of 80% or more at a wavelength of 300 nm.

The optical glass of the present invention is preferably for press molding.

An optical glass lens of the present invention is characterized by comprising the optical glass described above.

ADVANTAGE OF THE INVENTION According to this invention, an optical glass with high ultraviolet transmittance and excellent press-moldability can be provided.

The optical glass of the present invention contains SiO ₂ 40-75%, B ₂ O ₃ 1-30%, Al ₂ O ₃ 0-15%, RO 0.1-10% (R is Mg, Ca, Sr, Ba and Zn), Li ₂ O 0.1 to 10%, Na ₂ O + K ₂ O 0.5 to 15%, ZrO ₀ to 3%, F ₀ to 5%, substantially essentially free of Sb ₂ O ₃ . The reasons for specifying the content of each component as described above will be described in detail below. In addition, unless otherwise specified, the following "%" means "% by mass".

SiO ₂ has the effect of improving the ultraviolet transmittance and weather resistance, lowering the refractive index, and increasing the liquidus viscosity. The content of SiO ₂ is 40-75%, preferably 45-70%, in particular 50-65%. If the SiO ₂ content is too low, it may become difficult to lower the refractive index, and the UV transmittance tends to be lowered. On the other hand, if the content of SiO ₂ is too high, the glass transition point tends to rise and the press moldability tends to deteriorate. In addition, the solubility of the glass deteriorates, and devitrification substances containing SiO ₂ are likely to precipitate.

B ₂ O ₃ has the effect of lowering the refractive index, increasing the liquidus viscosity, and improving the weather resistance. The content of B ₂ O ₃ is 1-30%, preferably 3-26%, especially 5-22%. If the content of B ₂ O ₃ is too small, it becomes difficult to lower the refractive index. On the other hand, if the content of B ₂ O ₃ is too high, the weather resistance is deteriorated, and striae are likely to occur due to the tendency to evaporate during molding.

Al ₂ O ₃ has the effect of lowering the refractive index, increasing the liquidus viscosity, and improving the weather resistance. The content of Al ₂ O ₃ is 0-15%, preferably 1-13%, 2-11%, especially 3-9%. If the content of Al ₂ O ₃ is too high, the solubility of the glass is deteriorated, and devitrification substances containing Al ₂ O ₃ are likely to precipitate.

In addition, SiO ₂ /B ₂ O ₃ is preferably 10 or less, 7.5 or less, 5 or less, 4 or less, particularly 3 or less. If the ratio of SiO ₂ /B ₂ O ₃ is too large, the solubility of the glass deteriorates, and devitrification substances containing SiO ₂ tend to precipitate. Moreover, the lower limit of SiO ₂ /B ₂ O ₃ is not particularly limited, but in reality, it is preferably 1 or more. _In addition _, " _SiO2 / _B2O3 " refers to the value obtained by dividing the content of _SiO2 by the content of _B2O3 .

Also, SiO ₂ /Al ₂ O ₃ is preferably 10 or less, 7.5 or less, 5 or less, 4 or less, particularly 3 or less. If the SiO ₂ /Al ₂ O ₃ ratio is too large, the solubility of the glass deteriorates, and devitrification substances containing SiO ₂ are likely to precipitate. Also, the lower limit of SiO ₂ /Al ₂ O ₃ is not particularly limited, but in reality, it is preferably 1 or more. _In addition _, " _SiO2 / _Al2O3 " refers to the value obtained by dividing the content of _SiO2 by the content of _Al2O3 .

RO (R is at least one selected from Mg, Ca, Sr, Ba and Zn) is a component that lowers the glass transition point and high-temperature viscosity of the glass. The content (total amount) of RO is 0.1 to 10%, preferably 1 to 8%, more preferably 2 to 5%. If the RO content is too low, it will be difficult to lower the glass transition point. On the other hand, if the RO content is too high, the glass tends to devitrify, making it difficult to vitrify, and the glass tends to fuse to the press mold during press molding. The content of each component of RO is also preferably within the above range.

Li ₂ O is a component that lowers the glass transition point and the high-temperature viscosity of the glass. The content of Li ₂ O is 0.1 to 10%, preferably 1 to 8%, particularly 2 to 6%. If the content of Li ₂ O is too small, it becomes difficult to lower the glass transition point. On the other hand, if the content of Li ₂ O is too large, the ultraviolet transmittance tends to decrease and the weather resistance tends to deteriorate. In addition, the glass is easily fused to the press mold during press molding.

Na ₂ O and K ₂ O are components that lower the glass transition point and lower the high-temperature viscosity of the glass. The content of Na ₂ O+K ₂ O is 0.5-15%, preferably 1-10%, 1-8%, 2-7%, especially 3-6%. If the content of Na ₂ O+K ₂ O is too small, the above effect will be difficult to obtain. On the other hand, if the content of Na ₂ O+K ₂ O is too large, the UV transmittance will be lowered and the weather resistance will tend to deteriorate.

In addition, the preferable range of content of _Na2O and _K2O is as follows.

The content of Na ₂ O is preferably 0-10%, 0.5-8%, 1-7%, especially 2-6%.

The content of K ₂ O is preferably 0-10%, 0.5-8%, 1-7%, especially 2-6%.

The content of Li ₂ O+Na ₂ O+K ₂ O is preferably 0.6-25%, 2-18%, especially 5-12%. When the content of Li ₂ O+Na ₂ O+K ₂ O is too small, it becomes difficult to lower the glass transition point. On the other hand, when the content of Li ₂ O+Na ₂ O+K ₂ O is too large, the ultraviolet transmittance tends to decrease and the weather resistance tends to deteriorate. note that. "Li2O _{+ Na2O +} K2O" means the _total content of Li2O, _Na2O and _K2O .

Li ₂ O/(Na ₂ O+K ₂ O) is preferably 10 or less, 5 or less, 3 or less, 2 or less, particularly 1 or less. If Li ₂ O/(Na ₂ O+K ₂ O) is too large, the glass tends to fuse with the press mold during press molding. The lower limit of Li ₂ O/(Na ₂ O+K ₂ O) is preferably 0.01 or more. In addition, "Li2O/( _{Na2O + K2O} )" refers to the value obtained by dividing the content of Li2O by the content of _{Na2O + K2O} .

(Li ₂ O+Na ₂ O+K ₂ O)/RO is preferably 100 or less, 50 or less, 30 or less, 25 or less, particularly 20 or less. If (Li ₂ O+Na ₂ O+K ₂ O)/RO is too large, the UV transmittance tends to decrease and the weather resistance tends to deteriorate. The lower limit of (Li ₂ O+Na ₂ O+K ₂ O)/RO is preferably 0.1 or more. In addition, "(Li ₂ O+Na ₂ O+K ₂ O)/RO" indicates a value obtained by dividing the content of Li ₂ O+Na ₂ O+K ₂ O by the content of RO.

ZrO ₂ has the effect of improving weather resistance. The content of ZrO ₂ is 0-3%, preferably 0-2%, especially 0.1-2%. If the content of ZrO ₂ is too large, the UV transmittance is lowered, and the liquidus viscosity is lowered, making devitrification more likely.

_F2 is a component that increases the ultraviolet transmittance. The content of F ₂ is 0-5%, preferably 0.5-3%, especially 1-2%. If the content of F ₂ is too high, evaporation during melting increases, causing striae and the like, which tends to make the glass non-homogeneous. In addition, the glass is easily fused to the press mold during press molding.

Since Sb ₂ O ₃ tends to lower the ultraviolet transmittance, it is preferably not substantially contained.

In addition to the above components, various components shown below can be contained.

La ₂ O ₃ , Nb ₂ O ₅ , Bi ₂ O ₃ and WO ₃ are components that enhance weather resistance and chemical weather resistance. Moreover, the refractive index can be adjusted by including these components. The content of La ₂ O ₃ +Nb ₂ O ₅ +Bi ₂ O ₃ +WO ₃ is preferably 0-0.05%. If the content of these components is too high, problems such as a decrease in devitrification resistance, an increase in melting temperature, or a decrease in ultraviolet transmittance are likely to occur. The content of each component of La ₂ O ₃ , Nb ₂ O ₅ , Bi ₂ O ₃ and WO ₃ is also preferably within the above range.

Since TiO ₂ tends to lower the UV transmittance, it is preferable that its content be as small as possible. Specifically, the content of TiO ₂ is preferably 100 ppm or less, particularly 50 ppm or less.

Since Fe ₂ O ₃ , which is easily mixed as an impurity, tends to lower the ultraviolet transmittance, the content thereof is preferably as small as possible. Specifically, the content of Fe ₂ O ₃ is preferably 50 ppm or less, particularly 30 ppm or less.

1% or less of a component such as carbon or metallic tin that serves as a reducing agent when the glass is melted may be added.

In addition, since Cu, Ag, Pr, and Br are components that color the glass, it is preferable not to substantially contain them. Considering the impact on the environment, Cd is preferably not substantially contained. The phrase "substantially does not contain Cu, Ag, Pr, Br, and Cd" means that it is not intentionally contained as a raw material, and objectively, Cu, Ag, Pr, Br, and Cd are not contained. It means that the amount is less than 0.1%.

The optical glass having the above composition preferably has a refractive index nd of 1.45 to 1.55, 1.48 to 1.53, particularly 1.49 to 1.52. Further, the Abbe number is preferably 50-65, 52-63, particularly 54-60.

Since the optical glass of the present invention has a relatively low refractive index as described above, it has a high light incidence efficiency. Therefore, there is practically no problem even if the antireflection film is not provided. However, if necessary, an antireflection film may be formed.

The optical glass of the present invention preferably has a glass transition point of 550° C. or lower, 530° C. or lower, particularly 500° C. or lower. Although the lower limit of the glass transition point is not particularly limited, it is practically 400° C. or higher. Also, the softening point is preferably 700° C. or lower, 680° C. or lower, particularly 650° C. or lower. Although the lower limit of the softening point is not particularly limited, it is practically 550° C. or higher. Since the glass transition point and softening point are low, the press molding temperature is low, and it is easy to suppress the deterioration of the press mold.

The optical glass of the present invention preferably has a difference between the glass transition point and the softening point of 245° C. or less, 220° C. or less, particularly 200° C. or less. If the difference between the glass transition point and the softening point is small, the glass tends to solidify quickly during press-molding and cooling, making it difficult for the glass to fuse to the press die.

The optical glass of the present invention has a thermal expansion coefficient of 40×10 ⁻⁷ /° C. or more, 50×10 ⁻⁷ /° C. or more, 60×10 ⁻⁷ /° C. or more, particularly 70×10 ^{− 7} /°C or more is preferable. If the coefficient of thermal expansion is too low, it will be difficult to release the glass from the press mold after press molding and cooling. Although the upper limit of the coefficient of thermal expansion is not particularly limited, it is practically 150×10 ⁻⁷ /° C. or less.

The optical glass of the present invention has good light transmittance in the deep ultraviolet region with a wavelength of approximately 350 nm or less. Specifically, the optical glass of the present invention preferably has a thickness of 1 mm and a light transmittance at a wavelength of 270 nm of 50% or more, 60% or more, particularly 70% or more. Further, it is preferable that the thickness is 1 mm and the light transmittance at a wavelength of 300 nm is 80% or more, 85% or more, particularly 90% or more.

Next, a method for manufacturing the optical glass lens of the present invention will be described.

First, glass raw materials are blended so as to have a desired composition, and then melted in a glass melting furnace. The melting temperature of the glass is preferably 1150° C. or higher, 1200° C. or higher, particularly 1250° C. or higher. The melting temperature is preferably 1450° C. or lower, 1400° C. or lower, 1350° C. or lower, particularly 1300° C. or lower, from the viewpoint of preventing glass coloring due to Pt melting from the platinum metal constituting the melting vessel.

Also, if the melting time is too short, there is a possibility that sufficient defoaming will not be possible, so the melting time is preferably 2 hours or more, particularly 3 hours or more. However, from the viewpoint of preventing glass coloring due to Pt melting from the melting vessel, the melting time is preferably within 8 hours, particularly within 5 hours.

Next, the molten glass is dripped from the tip of the nozzle to prepare droplet-shaped glass, and optical glass is obtained. Alternatively, molten glass is rapidly cooled and cast to form a glass block, which is then ground, polished, and washed to obtain optical glass.

Subsequently, the optical glass is placed in a precision-machined mold and press-molded while being heated until softened, thereby transferring the surface shape of the mold to the optical glass. Thus, an optical glass lens can be obtained.

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

Tables 1 and 2 show examples of the present invention (Sample Nos. 1 to 12) and Comparative Example (Sample No. 13).

Each sample was produced as follows.

First, glass raw materials prepared to have the compositions shown in Tables 1 and 2 were placed in a platinum crucible and melted at 1300° C. for 2 hours. Next, the molten glass was poured onto a carbon plate, cooled and solidified, and then annealed to produce a glass block. After that, it was ground, polished and washed to obtain an optical glass. Various properties of the optical glass thus obtained were evaluated. Results are shown in each table. After that, the optical glass was placed in a precision-machined mold and pressure-molded while being heated at the softening point. The surface shape of the mold was transferred to the optical glass. A convex lens, a plano-convex lens with a front curvature radius of 10 mm and a center thickness of 0.5 mm, and a biconvex lens with a front curvature radius of 10 mm, a back curvature radius of 10 mm and a center thickness of 0.5 mm were obtained.

The refractive index nd was shown as a measured value at the d-line (wavelength: 587.6 nm) using a refractometer.

The glass transition point was measured using a dilatometer.

Softening points were measured using the fiber elongation method.

The coefficient of thermal expansion was measured in a temperature range of 30 to 300°C using a dilatometer.

The light transmittance was measured with a spectrophotometer (UV-3100 manufactured by Shimadzu Corporation).

The contents of TiO ₂ and Fe ₂ O ₃ were analyzed by an inductively coupled plasma mass spectrometer (ICP-MS).

As is clear from the table, No. 1, which is an example of the present invention. Each sample of 1 to 12 has a refractive index nd of 1.46 to 1.54, a glass transition point of 440 to 540 ° C., a softening point of 600 to 699 ° C., and a thermal expansion coefficient of 42 to 90 × 10 ^-7 / ° C. , the light transmittance (270 nm) was 55 to 78%, and the light transmittance (300 nm) was 81 to 94%. On the other hand, No. 1, which is a comparative example. Sample No. 13 was found to have a high glass transition point of 630°C and a high softening point of 785°C, indicating poor press formability.

Claims (7)

% by mass, SiO ₂ 55.0-75%, B ₂ O ₃ 1-30%, Al ₂ O ₃ 0-13%, RO 0.1-10% (R is Mg, Ca, Sr, Ba and Zn at least one selected from), Li ₂ O 0.1 to 1.5 %, Na ₂ O + K ₂ O 0.5 to 4.0 %, ZrO ₂ 0 to 3%, F ₂ 0 to 5% It does not substantially contain Sb ₂ O ₃ , has a refractive index (nd) of 1.45 to 1.55, has a thickness of 1 mm, a transmittance of 50% or more at a wavelength of 270 nm, and a softening point. is 700° C. or lower . The optical glass according to claim 1, further comprising 0 to 0.05% by mass of La ₂ O ₃ +Nb ₂ O ₅ +Bi ₂ O ₃ +WO ₃ . 3. The optical glass according to claim 1, further comprising TiO ₂ of 100 ppm or less and Fe ₂ O ₃ of 50 ppm or less in mass %. The optical glass according to any one of claims 1 to 3, which has a glass transition point of 550°C or lower. The optical glass according to any one of claims 1 to 4 , which has a thickness of 1 mm and a transmittance of 80% or more at a wavelength of 300 nm. 6. The optical glass according to any one of claims 1 to 5 , which is for press molding. An optical glass lens comprising the optical glass according to any one of claims 1 to 6 .