CN103145331B - High dioptrics glass and manufacture method thereof - Google Patents

Abstract

High-refractive optical glass and its manufacturing method. The invention discloses an optical glass with high refraction and high dispersion, which has high transmission and low glass density, and also has the characteristics of good devitrification resistance and is suitable for repeated pressing in the secondary hot pressing process . The above optical glass is characterized in that it contains SiO ₂ , B ₂ O ₃ , Gd ₂ O ₃ , Nb ₂ O ₅ , TiO ₂ , BaO, CaO, Ta ₂ O ₅ , ZnO, Li ₂ O, ZrO ₂ as mandatory Components do not contain specific Bi2O3 components and expensive raw material components. This glass has a refractive index (nd) above 1.88, an optical constant with an Abbe number (Vd) of 23-26, a glass density below 4.2, and a transition temperature (Tg) below 610°C.

Description

High refraction optical glass and manufacturing method thereof

technical field

The invention relates to a high refraction and high dispersion optical glass and a method for manufacturing the optical glass. More specifically, the present invention particularly relates to a specific range of optical constants with a refractive index (nd) above 1.88 and an Abbe number (vd) in the range of 23 to 26, and has high transmission and low density , Optical glass with good stability.

Background technique

In recent years, with the rapid popularization of SLR cameras and their widespread use in people's lives, the optical materials used in the optical system of SLR cameras have been widely used, especially as high refractive index and high dispersion glass, which not only meets the requirements of The design requirements of the optical system of high-performance digital cameras need to meet the requirements of large-size lenses and high-definition requirements of the optical system of SLR cameras.

Developing an optical glass with a low Abbe number is very useful for the design of the optical system of a SLR camera. By combining two groups of optical lenses with different Abbe numbers or a larger difference, the chromatic aberration of the two-color light can be reduced or eliminated, thereby improving the imaging quality of the lens.

As this type of optical glass in the field of high refraction and high dispersion, no matter in terms of refractive index or Abbe number, there are currently many types, such as phosphate series glass, or such series with high content of Bi ₂ O ₃ glass. However, this kind of glass will bring deep coloring and low transmittance of the glass, and with the irradiation of ultraviolet light, the coloring of the glass will deepen. High transmission requirements for optical systems.

In the manufacturing process of optical glass, as the refractive index increases, the coloring tendency of the glass is intensified, especially for optical glass with high refraction and high dispersion, as the dispersion value increases, the coloring will be more serious. In particular, when the glass with aggravated tinting tendency is used, the sensitivity to blue light on the short-wavelength side of the primary color in the optical imaging system of the camera will decrease, which will seriously affect the clarity of the imaging quality.

Not only that, for this kind of optical glass with high refraction and high dispersion, in the process of secondary hot pressing, the stability of the glass and good resistance to devitrification are achieved after repeated hot pressing. The key to avoid fogging and devitrification on the surface.

As for such high-refraction and high-dispersion optical glass with a refractive index (nd) above 1.88 and an Abbe number (vd) of 23-26, there is no known optical glass with optical characteristics in this range. The early patent document CN1204073C introduced the refractive index of the glass within this range, but the glass Abbe number (vd) is greater than 27, and the glass density is high and the resistance to devitrification is poor; CN101012103A, its refractive index (nd) belongs to the scope of the present invention, But the dispersion value is low, the Abbe number is greater than 26 or larger, and as CN1835895A, CN101318769A, although the Abbe number (vd) is 26 or lower, the refractive index (nd) is less than 1.88, which is relatively different from the optical constant of the present invention Large, can not meet the design requirements of the current new SLR camera optical system; In terms of satisfying repeated and repeated hot pressing, no defects appear on the surface of the blank, CN1204073C, CN101012103A, CN1835895A are difficult to overcome the secondary heat due to their high devitrification temperature Fog spots and opacities formed on the surface of molded parts do not appear during pressing. In addition, improving the stability of glass penetration and manufacturing, and low-cost operation must also be considered, so the above-mentioned defects are obvious.

Contents of the invention

The purpose of the present invention is not only to provide optical constants having the above range and meeting the requirements of the optical system design of the camera, but also to achieve good devitrification resistance without introducing expensive components, and to achieve stable, low Quantification of cost production and achieving good secondary hot pressing. At the same time, it also realizes the lightweight of the lens with low density, reducing the weight of the whole machine. With a low transition temperature (Tg), it is suitable for the drawing of preforms for precision molding. And overcome above-mentioned deficiency and defective.

Not only that, but another purpose of the present invention is to realize the high transmission of the optical lens and meet the design requirements of the optical system of the SLR camera to the greatest extent.

The optical glass of the present invention contains: SiO ₂ , B ₂ O ₃ , Gd ₂ O ₃ , Nb ₂ O ₅ , TiO ₂ , BaO, CaO, Ta ₂ O ₅ , ZnO, Li ₂ O, ZrO ₂ as essential components , the optical glass has an optical constant whose refractive index nd is greater than 1.88 and Abbe's number vd is 23-26.

Wherein, when expressed in (wt%), the optical glass contains the following components:

10-25% SiO ₂

1～11% B ₂ O ₃ condition is: (SiO2/B2O3) weight ratio is greater than 2

5～15% Gd ₂ O ₃

15～30% Nb ₂ O ₅

5~22% TiO ₂ condition is: (Nb2O5/TiO2) weight ratio is greater than 1

10-30% BaO

3~15% CaO

Greater than 0 but less than 5% Ta ₂ O ₅

Greater than 0～but less than 5% ZnO

The condition of Li ₂ O greater than 0 but less than 6% is: (ZnO+Li2O) weight ratio is less than 1

Less than 5% ZrO ₂

0~5% of WO ₃

0～ ₅ %K2O

0～5%SrO

0～2% SnO ₂

0 or more but less than 1% Sb ₂ O ₃ .

Preferably, when expressed in (wt%), the optical glass contains the following components:

12～22% SiO ₂

2~8% B ₂ O ₃ condition is: (SiO2/B2O3) weight ratio is greater than 2

6～12% Gd ₂ O ₃

16～28% Nb ₂ O ₅

7~20% TiO ₂ condition is: (Nb2O5/TiO2) weight ratio is greater than 1

12～28% BaO

4~11% CaO

Greater than 0 but less than 4% Ta ₂ O ₅

More than 0～but less than 4% ZnO

The condition of Li ₂ O greater than 0 but less than 5% is: (ZnO/Li2O) weight ratio is less than 1

Less than 4% ZrO ₂

0~4% of WO ₃

0～3% K ₂ O

0～3%SrO

0~1% SnO ₂

0 or more but less than 0.5% Sb ₂ O ₃ .

Preferably, the optical glass contains the following components:

SiO ₂ 14.5～21.5%;

B ₂ O ₃ 2.7～6.9%;

Gd ₂ O ₃ 6.1～10.9%;

Nb ₂ O ₅ 19.2～26.7%;

TiO ₂ 11.3～18.3;

BaO12.5～26.0%;

CaO3.0～9.2%;

_Ta2O5 0.6～3.8% _;

ZnO0.6～2.8%;

_Li2O1.6 ～3.5%;

ZrO ₂ 0.7～3.2%;

WO30～3.1%;

K ₂ O0～1.0%;

SrO0～1.0%;

SnO ₂ 0～0.4%;

Sb ₂ O ₃ 0.1%.

Wherein, the internal transmission of the glass is less than 412.

Wherein, the density of the glass is not higher than 4.2g/cm ³ .

Wherein, the glass transition temperature Tg is not higher than 610°C, and the liquidus temperature L _T is not higher than 1080°C.

The manufacturing method of the optical glass of the present invention includes the following steps: including flowing from a uniform glass liquid state through a leaking device into a specific molding mold to cool and solidify to a constant thickness and width, and to manufacture a blank formed of the aforementioned optical glass.

The method for manufacturing secondary hot-pressed parts of the present invention is to cut and process the aforementioned blanks into required specifications and weights, then heat and soften them, and press them in the softened state to obtain pressed blanks of different shapes. .

The method of the present invention for manufacturing the preform of precision pressing includes the following steps: softening the aforementioned optical glass by heating, and pulling down in the softened state to make a prefabricated rod.

In order to meet the above-mentioned requirements, the present invention finds through repeated studies that SiO ₂ , B ₂ O ₃ , Gd ₂ O ₃ , Nb ₂ O ₅ , TiO ₂ , BaO, CaO, Ta ₂ O ₅ , ZnO, Li ₂ O, etc., the optimal ratio of necessary components and the introduction and adjustment of optional components such as WO ₃ , SrO, K ₂ O, and when Bi ₂ O ₃ components and expensive rare earth components are not introduced, not only achieve In order to have the optical constants in the above specific range, and also have high transmission, low glass density and low transition temperature, it is not only suitable for secondary hot pressing, but also suitable for drawing precision pressed preforms.

As a result of the present invention, it is also found that the ratio of SiO2/B2O3 content is adjusted to be greater than 2 or greater, the weight ratio of ZnO/Li2O is less than 1, and the adjustment and proportioning are optimized to make a glass with specific optical constants, low glass density and In addition to the low transition temperature, the transmission is further improved, the devitrification resistance is further optimized, and the optical glass has good stability, thus completing the present invention.

The glass components of glasses 1 to 10 included in the optical glass of the present invention will be described in detail below, and the content of each component and the percentage (%) of the total content of each group are expressed in Wt% respectively:

In order to realize the above-mentioned performances, the optical glass of the present invention comprises SiO2 and B2O3 as the necessary components for forming the glass network, Gd2O3, Nb2O5, TiO2 as the necessary components for increasing the refractive index, and includes Gd2O3, Nb2O5, TiO2 as the components for lowering the transition temperature ZnO and Li2O must be selected components, wherein the introduction of alkaline earth metal oxides BaO, CaO, SrO at least two or more, while limiting the introduction of SnO2, K2O.

In the high-refraction and high-dispersion glass of the present invention, SiO2 is an essential component of the glass network forming component, and is also the most effective component for increasing the viscosity of the glass liquid and enhancing the devitrification resistance. When the introduced amount of SiO2 is too low, the viscosity of the glass decreases, the devitrification becomes worse, and also the coloring of the glass is aggravated, and it is difficult to form a stable, high-quality glass. If the amount introduced is too large, the melting solubility becomes poor, the optical constant decreases, and it is difficult to obtain ideal refractive index and dispersion values. Therefore, it is preferably 10 to 25%, more preferably 11 to 24%, and even more preferably 12 to 22%.

B2O3 is the most effective component for forming a glass network, and is effective for reducing solubility and lowering melting temperature. However, in the glass of the present invention, if the amount introduced is too large, the coloring of the glass will be aggravated. Therefore, the amount introduced is controlled below 11%, preferably below 10, more preferably 8% or less.

One object of the present invention is to achieve high transmittance, and when the ratio of content SiO2/B2O3 content, that is, SiO2 content/B2O3 content is less than 2.0, the coloring tendency of the glass is increased, and the devitrification resistance is reduced and the stability is changed. Difference. When the SiO2/B2O3 weight ratio is greater than 2.0 or greater, the coloring of the glass is gradually weakened, the transmittance is increased, and the stability of the glass is also improved. Therefore, it is necessary to increase the specific gravity of SiO2 appropriately, and the SiO2/B2O3/weight ratio is preferably greater than 2.0 to reduce glass coloring and increase transmittance. The above SiO2/B2O3/ ratio is preferably at least 2.0, more preferably at least 2.5 or greater.

Gd2O3 is the same as La2O3, and both have components to realize high refractive index. However, when the amount introduced is too large, it is difficult to achieve the required optical constants, and the stability of the glass will also decrease, but when the amount introduced is too low, the devitrification resistance of the glass will also deteriorate. Therefore, in the present invention, the introduction amount of Gd2O3 is controlled at 5-15%, preferably 5-13%, more preferably 6-12%.

In the present invention, Nb2O5 is an important necessary component to achieve high refractive index and high dispersion, and can significantly improve the anti-devitrification performance of the glass and improve the stability of the glass. However, when its introduction is less than 15%, then It is difficult to obtain the above effects. If it is greater than 30%, the opposite will occur, the devitrification resistance and stability of the glass will decrease, and the Abbe number will exceed the set range. Therefore, the preferred range thereof is 15 to 30%, and the more preferred range is 19 to 32%. Change it to 17~28% here

In the present invention, TiO2 is an essential component for increasing the refractive index and dispersion value. However, if the introduced amount is less than 5%, it will be difficult to achieve the set optical constants of high refraction and high dispersion, and the density of the glass will also increase. However, the introduction of more than 22% will intensify the absorption of the short-wavelength side and long-wavelength bands, aggravate the coloring of the glass, and at the same time reduce the devitrification resistance and solubility of the glass. Therefore, its introduction amount is controlled at 5-22%, preferably 6-21%, more preferably 8-19%, most preferably 10-19%.

In order to meet the above set optical characteristics and achieve high transmission, it is preferable that the amount of Nb2O5 introduced is greater than that of TiO2, more preferably that the weight ratio of Nb2O5/TiO2 is greater than 1.0, and even more preferably that the weight ratio of Nb2O5/TiO2 is greater than 1.2.

In the present invention, BaO not only has the function of improving the transmission of the glass to the end of the short wavelength in the visible light region, but also has the function of improving the stability and resistance to devitrification of the glass, especially when the amount of TiO2 introduced is too much, the effect of BaO will be even stronger. obvious. However, when the amount of BaO introduced exceeds 30%, not only the refractive index of the glass will decrease, but also the stability of the glass will decrease accordingly. Therefore, the introduction amount of BaO is controlled at 10-30%, preferably 12-28%, more preferably 14-26%.

When the amount of CaO introduced is more than 3%, it can significantly increase the transmittance of the short-wavelength side segment and reduce the glass density, and can maintain a good anti-devitrification state and accelerate the clarification of the glass liquid. However, when the introduction amount exceeds 15%, its excessive introduction will reduce the refractive index of the glass, especially the obvious reduction of the dispersion value, and make the glass viscosity smaller, devitrification resistance and stability decrease. Therefore, its introduction amount is 3-15%, preferably 4-13%, more preferably 4-11%, further preferably 5-9%.

Ta2O5 is an important component to increase the refractive index, increase the dispersion value and make the optical constant reach the set range, and can significantly improve the stability of the glass. When Ta2O5 is less than 0.5%, its effect is not obvious. When it exceeds 5%, it not only reaches If the dispersion value is less than the set value, the glass density will be increased, and the cost of the glass will also be greatly increased, which is not conducive to low-cost operation. Therefore, its introduction amount is controlled to be 1-5%, preferably 1-4%, more preferably 1-3%.

In the present invention, ZnO is a component that lowers the transition temperature and improves the stability of the glass, especially when the amount of Nb2O5 introduced is too large, it can play a more stable role. However, if its content is too much, it will be difficult to achieve the expected refractive index and dispersion value, and the coloring of the glass will also be aggravated. Therefore, in order to achieve the set optical constants of the glass and reduce the coloring of the glass, the introduction amount is controlled at 1-5%, preferably 1-4%, more preferably 1-3%.

Compared with other alkali metal oxides, Li2O has the effect of increasing the refractive index and reducing the glass transition temperature the most, and also has the effect of improving glass solubility, increasing glass molding viscosity, and reducing glass coloring. It is a must for the present invention. components. However, when introduced in excess, the devitrification resistance of the glass will be reduced, and the optical constant will also be greatly reduced. When the improvement of glass solubility and transition temperature is preferably considered, the introduction amount is controlled at 1-6%, preferably 1-5%, more preferably 1-4%.

By adjusting the ratio of ZnO/Li2O content, in order to obtain a low transition temperature by achieving the required specific optical constants and at the same time maintaining a balance point between significantly reducing the transition temperature (Tg) and improving glass stability (Tg) and achieve good solubility of the glass. Preferably, the introduced amount of ZnO is less than that of Li2O, more preferably the weight ratio of ZnO/Li2O is less than 1, and further preferably the weight ratio of ZnO/Li2O is less than 0.5.

ZrO2 has the effect of increasing the refractive index and the devitrification resistance of the glass without aggravating the coloring of the glass. However, when the introduction amount is greater than 5%, not only the solubility will be deteriorated, but also the refractive index and dispersion value will be reduced. Therefore, its introduction amount is preferably 0.5 to 5%, more preferably 1 to 4%, and even more preferably 1 to 3%.

WO3 has a remarkable effect on increasing the refractive index and dispersion value, and improving devitrification. However, when the introduction amount exceeds 5%, the light absorption on the short-wavelength side of the visible light region will increase, and the tendency of glass coloring will increase. Therefore, as an optional component, its introduction amount is 0-5%, preferably 0-4%, more preferably 0-3% or less.

Like Li2O, K2O, as a congener, helps to improve the melting performance, lower the melting temperature, and reduce the glass coloring aggravated by the introduction of excess TiO2. However, if the introduction amount exceeds 5%, the devitrification resistance of the glass will be deteriorated sharply, and the refractive index and dispersion value will also be significantly reduced. Therefore, its introduction amount is 0 to 5%, preferably 0 to 4%, more preferably 0 to 3% or less.

As an optional component, SrO can improve the glass meltability and increase the short-wavelength side segment transmittance. However, when the introduced amount is too high, the refractive index and stability of the glass will decrease, so the introduced amount is adjusted to 0-5%, preferably 0-4%, more preferably 0-3%.

SnO2 has the same effect as ZrO2, but when the amount introduced is too much, the glass meltability will be deteriorated, the refractive index and dispersion value will also be reduced, and the glass transition temperature (Tg) will rise rapidly. Therefore, its introduction amount is preferably 0 to 2%, more preferably 0 to 1.5% or less.

Sb2O3 is an arbitrary additive used as a clarifying agent. If it is added or introduced in excess, it will deepen the coloring of the glass and reduce the transmittance. At the same time, it will also deteriorate the melting stability and the internal quality of the glass. Therefore, its introduction amount is 0 to 1%, preferably 0 to 0.6%, more preferably 0 to 0.5% or less.

As mentioned above, in order not only to improve the stability of manufacturing, but also to increase the transmittance in the visible light region and reduce the glass density, while realizing the specific optical constant and low transition temperature of the present invention, SiO2, B2O3, Gd2O3, Nb2O5 are preferred , TiO2, Ta2O5, BaO, CaO, ZnO, Li2O,, ZrO2, the introduction amount of components is 95% or more, the introduction amount of WO3, K2O, SrO, SnO2 and other components is 5% or less, the total The amount introduced was 100%.

The optical glass of the present invention will be described below with its physical and chemical properties

The optical glass of the invention has a refractive index (nd) greater than 1.88 and an Abbe number (vd) less than 26. When the refractive index is gradually increased, the devitrification resistance of the glass decreases, however, the optical glass of the present invention can achieve excellent devitrification resistance and achieve high transmittance, thus further increasing the refractive index (nd). Therefore, the refractive index (nd) of the present invention is preferably at least 1.88, more preferably 1.90 or 1.91. To achieve manufacturing stability, it is desirable to limit the refractive index (nd) to 1.92 or less, more desirably to 1.91 or less.

Furthermore, the Abbe's number (vd) of the optical glass of the present invention is preferably 24-26 in order to realize the stability of production and reduce glass coloration.

The optical glass of the present invention is mainly used to obtain a secondary shape through secondary heating, softening and pressing or repeated pressing, and then processed into an optical lens. Or it can be softened by secondary heating and drawn into a prefabricated bar suitable for precision pressing. Therefore, its low transition temperature and good devitrification resistance are the key to the manufacture of both.

According to the optical glass of the present invention, the internal transmission (wavelength λ70) is controlled to be below 412nm, preferably 410nm or less, through component optimization and process modification. Control internal transmission (wavelength λ5) below 371nm, preferably 370nm or less. Since the optical glass of the present invention has a transmission of 70% or higher in the λ70 wavelength range and λ5 is more shifted to the short-wave direction, it is suitable as various high-pixel, high-resolution optical lenses.

When the glass density is excessively reduced, the stability of its manufacture is reduced, and the coloring tendency of the glass will also be aggravated. Therefore, the glass density of the optical glass of the present invention is controlled within a range greater than 4.0 but less than 4.2.

The premise of realizing the stability of manufacturing is to have a low liquidus temperature. When the devitrification resistance of the glass decreases, the liquidus temperature rises sharply, and the glass stability becomes poor. Therefore, the liquidus temperature of the optical glass of the present invention is controlled below 1080°C, more preferably 1070°C or lower.

The optical glass of the present invention has a high refractive index (nd) of 1.88 or more, an Abbe number (vd) of 26 or less, is a high refractive index optical glass with a low transition temperature suitable for precision molding, and when It has good stability when it is directly formed into a blank from a glass liquid state. During the secondary hot pressing process, repeated secondary hot pressing does not cause devitrification, and can be used to make prefabricated bars for precision pressing.

The optical glass of the present invention has a glass internal transmission not higher than 412, a density of 4.17 or less, and a transition temperature (Tg) of 610°C or lower. In addition, compared with the existing high-refraction and high-dispersion optical glass, It also has good devitrification resistance and low cost, and can realize low-cost operation and mass production in a stable state.

Apparently, according to the above content of the present invention, according to common technical knowledge and conventional means in this field, without departing from the above basic technical idea of the present invention, other various forms of modification, replacement or change can also be made.

The above-mentioned content of the present invention will be further described in detail below through specific implementation in the form of examples. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following examples. All technologies realized based on the above contents of the present invention belong to the scope of the present invention.

detailed description

Embodiment 1 The properties of the optical glass of the present invention

Tables 1 and 2 show the glass compositions of Examples No. 1 to No. 10 of the optical glass of the present invention and the compositions of Comparative Examples No. a to No. d of the same type of glass as the glass of the present invention. The optical glass obtained by annealing at -4.0/h and cooling in each example and comparative example is measured below, the refractive index (nd), Abbe number (vd), internal transmission (λ70) and (λ5), The measurement results of density (ρ), transition temperature (Tg) and liquidus temperature (LT) are given in Tables 1 and 2.

The raw materials of each component are weighed and mixed according to the composition ratio of each embodiment and comparative example to make a batch, which is put into a specific platinum container, melted, stirred, and clarified at a temperature of 1150 ° C to 1300 ° C, and then again After stirring evenly, it is poured or leaked into the mold to form, and it can be annealed.

The properties of the above-mentioned glasses were determined by the following methods:

(1) Refractive index (nd) and Abbe number (vd) measurements Glass samples were obtained at an annealing rate of -4.0/h.

(2) Measure the internal transmission of 5mm and 10mm samples with two parallel polished surfaces, that is, the wavelength (nm) at 70% is determined to be λ70, and the wavelength (nm) at 5% is determined to be λ5. (Transmittance when internal transmission does not include reflection loss on the surface of the sample)

(3) Determination of density (ρ) is measured by Archimedes method.

(4) Glass transition temperature (Tg) was measured with a thermal analyzer device at a heating rate of 4.0°C/min.

(5) Liquidus temperature (L _T ): Add 500g of glass samples into a small platinum container, set the furnace at 10°C intervals, keep warm at different temperatures for 2 hours, and cool the samples, and observe each piece through a microscope Crystallization inside the glass sample to determine the liquidus temperature.

Table 1 Melting Examples (% by weight)

Table 2 Melting Examples (% by weight)

As shown in Tables 1 and 2, the optical glasses №1 to №10 of the embodiments of the present invention have specific ranges of optical constants, that is, the refractive index (nd) is 1.8812 to 1.9261 and the Abbe number (vd) is 24.13 to 25.92. The upper limit of transmission is less than 412, the lower limit is less than 371, the specific gravity is lower than 4.2, and its transition temperature (Tg) is lower than 610°C. Due to the low liquidus temperature, it can not only achieve good reproduction of secondary hot pressing, but also be suitable for precision Preforms for molding. And can achieve stable mass production.

On the contrary, as shown in the comparative example in Table 2, although the refractive index (nd) of case a reaches 1.90, the Abbe number (vd) exceeds 26, which is no longer an optical constant of the present invention. At the same time, the density of the glass is also higher than the density of this range, its liquidus temperature is high, and it also contains expensive GeO ₂ components, which is not suitable for stable and low-cost mass production.

In case b, although the Abbe number (vd) is less than 26, the refractive index (nd) is less than 1.88, which is not an optical constant in this category. Therefore, the design requirements of the optical system of the single-lens reflex camera cannot be met. Not only that, the glass liquidus temperature is high, making it difficult to achieve stable mass production.

The optical constants of example c are lower than the specific optical constants of the present invention, both the refractive index (nd) and the Abbe number (vd), and the glass transition temperature is high and the resistance to devitrification is poor, so it is not suitable for precision pressing preforms The production of materials and the realization of secondary hot pressing.

In example d, although the refractive index (nd) also reaches 1.90, the Abbe number (vd) is greater than 30, and does not have the specific optical constant of the present invention. At the same time, due to the composition of Bi ₂ O ₃ , the glass transmittance is poor and the glass density is high.

In summary, the optical glass of the present invention has a high refractive index (nd) of 1.88 or greater, an Abbe number (vd) of 26 or less, and a high refractive index optical glass with a low transition temperature suitable for precision molding , and it has good stability when it is directly formed into a blank from a glass liquid state. During the secondary hot pressing process, repeated secondary hot pressing does not cause devitrification, and can be made into a prefabricated bar for precision pressing.

Claims (9)

1. An optical glass containing: SiO ₂ , B ₂ O ₃ , Gd ₂ O ₃ , Nb ₂ O ₅ , TiO ₂ , BaO, CaO, Ta ₂ O ₅ , ZnO, Li ₂ O, ZrO ₂ as mandatory Components, the optical glass has an optical constant with a refractive index nd greater than 1.88 and an Abbe number vd of 23 to 26; when expressed in (wt%), the optical glass contains the following components: 10-25% SiO ₂ 1～11% B ₂ O ₃ condition is: (SiO2/B2O3) weight ratio is greater than 2 5～15% Gd ₂ O ₃ 15～30% Nb ₂ O ₅ 5～22% TiO ₂ condition is: (Nb2O5/TiO2) weight ratio is greater than 1 10-30% BaO 3~15% CaO Greater than 0 but less than 5% Ta ₂ O ₅ Greater than 0 but less than 5% ZnO More than 0 but less than 6% Li ₂ O condition is: (ZnO+Li2O) weight ratio is less than 1 Less than 5% ZrO ₂ 0~5% WO ₃ 0~5% K ₂ O 0~5% SrO 0~2% SnO ₂ 0 or more but less than 1% Sb ₂ O ₃ . 2. The optical glass according to claim 1, characterized in that: when expressed in (wt%), said optical glass contains the following components: 12～22% SiO ₂ 2～8% B ₂ O ₃ condition is: (SiO2/B2O3) weight ratio is greater than 2 6～12% Gd ₂ O ₃ 16～28% Nb ₂ O ₅ 7～20% TiO ₂ condition is: (Nb2O5/TiO2) weight ratio is greater than 1 12-28% BaO 4~11% CaO Greater than 0 but less than 4% Ta ₂ O ₅ Greater than 0 but less than 4% ZnO Greater than 0 but less than 5% Li ₂ O condition is: (ZnO/Li2O) weight ratio is less than 1 Less than 4% ZrO ₂ 0-4% WO ₃ 0~3% K ₂ O 0~3% SrO 0~1% SnO ₂ 0 or more but less than 0.5% Sb ₂ O ₃ . 3. The optical glass according to claim 1, characterized in that: the optical glass contains the following components: 4. The optical glass according to any one of claims 1-3, characterized in that: the internal transmission of the glass is less than 412. 5. The optical glass according to claim 4, characterized in that: the density of the glass is not higher than 4.2 g/cm ³ . 6. The optical glass according to claim 4, characterized in that: the glass transition temperature Tg is not higher than 610°C, and the liquidus temperature L _T is not higher than 1080°C. 7. The optical glass according to any one of claims 1-3, characterized in that the density of the glass is not higher than 4.2 g/cm ³ . 8. The optical glass according to claim 7, characterized in that: the glass transition temperature Tg is not higher than 610°C, and the liquidus temperature L _T is not higher than 1080°C. 9. The optical glass according to any one of claims 1-3, characterized in that: the glass transition temperature Tg is not higher than 610°C, and the liquidus temperature L _T is not higher than 1080°C.