TW201841850A - Optical glass and optical element wherein the optical glass is composed of fluoride phosphate glass having a great partial dispersion rate and is capable of suppressing an increase in specific gravity - Google Patents

Abstract

The present invention provides an optical glass and an optical element. In the optical glass, the content of P5+ is 3-45 cation%; the content of Al3+ is 5 to 40 cation%, and includes at least one component selected from the group consisting of Ti4+, Nb5+ and W6+; the total content of Y3+, Gd3+, La3+, Yb3+, Lu3+ and Ba2+ is less than 35 cation%; the content of O2- is 5 to 85 anion%; the content of F- is 15 to 95 anion%; and the molar ratio (O2- / P5+) of the content of O2- with respect to the content of P5+ is more than 3.33.

Description

Optical glass and optical components

The invention relates to an optical glass and an optical element.

Fluorophosphate glass is a low-dispersion optical glass and is used as a material for various optical elements.

Low-dispersion optical glass generally refers to optical glass with a large Abbe number (νd). The Abbe number νd is the refractive index nd using the d-line (wavelength 587.56nm), the refractive index nF of the F-line (wavelength 486.13nm), and the refractive index nC of the C-line (wavelength 656.27nm), and is expressed by the following formula (1) . νd = (nd-1) / (nF-nC)… (1)

In lens optical systems such as cameras, in order to reduce chromatic aberration, although it is effective to use optical glass with a large νd, in order to correct higher-order chromatic aberrations, not only νd is large, but also the partial dispersion ratio Pg, F is also large. . The partial dispersion ratios Pg, F are the refractive indices ng using the nF, nC, and g-line (wavelength 435.84 nm) described above, and are expressed by the following formula (2). Pg, F = (ng-nF) / (nF-nC)… (2)

Examples of fluorophosphate glass having a high partial dispersion ratio are described in Patent Documents 1 to 3. The effects of various components on the physical properties of optical glass are described in Non-Patent Document 1. [Prior technical literature]

[Patent Literature] Patent Literature 1: Japanese Patent Application Laid-Open No. 2010-235429. Patent Document 2: Japanese Patent Application Laid-Open No. 2011-037637. Patent Document 3: Japanese Patent Application Laid-Open No. 5-208842.

[Non-Patent Documents] Non-Patent Documents 1: Tetsuya Izumi "Optical Glass" co-published, published November 1, 1949, 21-71 pages.

[Problems to be solved by the invention]

In Patent Documents 1 to 3, as components that contribute to the improvement of the partial dispersion ratios Pg and F of fluorophosphate glass, rare earth components such as La and Gd and Ba are cited. However, specific reasons why these components increase the partial dispersion ratio are not disclosed in Patent Documents 1 to 3. On the other hand, according to the contents described in Non-Patent Document 1, it is considered that the rare earths, Ba fluorides or oxides have any one or both of the following properties, and therefore have a tendency to exhibit low dispersion: (a) ultraviolet The intrinsic absorption peak wavelength in the region (wavelength 200 nm or less) is far from the wavelength region (400 nm to 800 nm) of visible light that is a target of chromatic aberration. (B) The intrinsic vibration absorption intensity in the infrared region (wavelength 1 μm or more) is small. Therefore, according to the above formula (2), it is considered that the rare-earth component and Ba contribute to the improvement of the partial dispersion ratios Pg and F by reducing the refractive index difference nF-nC of the F line and the C line.

However, it is known from the atomic size of rare earth elements and Ba that the specific gravity of glass can be increased. Therefore, if a single lens is made of a large amount of fluorophosphate glass containing rare earth elements and Ba, and the single lens is mounted on an autofocus imaging lens, the power of the single lens will increase due to the high quality of the single lens. Increase battery consumption. In addition, from the viewpoint of lens portability, an increase in lens quality is also undesirable.

Therefore, one aspect of the present invention is to provide an optical glass formed of a fluorophosphate glass that suppresses an increase in specific gravity and has a large partial dispersion ratio. [Means for solving problems]

In the course of intensive research on the fluorophosphate glass which suppresses the increase in specific gravity and has a large partial dispersion ratio, the present inventors focused on three components: Ti, Nb, and W. It is known that the intrinsic absorption wavelength in the ultraviolet region of the fluorides and oxides of Ti, Nb, and W is close to the visible light region, and the absorption intensity is also large. Therefore, the wavelength dispersion of the refractive index tends to have high dispersion. That is, the refractive index difference nF-nC of the F-line and the C-line becomes larger, and νd tends to become smaller. On the other hand, the refractive index difference ng-nF of the g-line and the F-line also becomes large. Here, if the effect of increasing ng-nF exceeds the effect of increasing nF-nC, it is clear from the expression (2) that Pg, F becomes large. The present inventors focused on the above aspects and conducted intensive studies. As a result, they found that they contained one or more of Ti, Nb, and W, and maintained low dispersion (large νd) in the same range as the conventional fluorophosphate glass And the glass composition range of fluorophosphate glass with greatly increased partial dispersion ratio Pg, F. In addition, it has been found that Ti, Nb, and W have the effect of greatly increasing the partial dispersion ratio even with a small amount compared with the rare earth component, and do not increase the specific gravity much like conventional glass with a high partial dispersion ratio. However, it has also been newly discovered that during the melting process of fluorophosphate glass containing Ti, Nb, and W, the Ti, Nb, and W components are easily volatilized from the molten glass liquid. In order to stably produce glass with fixed optical characteristics, it is desirable to suppress a large amount of Ti, Nb, and W from volatilizing during the melting process. Therefore, the present inventors conducted further research, and as a result, obtained the following new insights. The value obtained by dividing the volatile contents of the Ti, Nb, and W components and the O content in the glass composition by the P content (Molar ratio O ^2- / P ⁵⁺ ) are closely related. Based on this knowledge, the present inventors made further in-depth research, and as a result, found out that the optical glass according to one embodiment of the present invention.

That is, one embodiment of the present invention relates to an optical glass. The content of P ⁵⁺ is 3 to 45 cation%, and the content of Al ³⁺ is 5 to 40 cation%. It is selected from the group consisting of Ti ⁴⁺ and Nb ⁵⁺ And at least one of the components of W ⁶⁺ , the total content of Y ³⁺ , Gd ³⁺ , La ³⁺ , Yb ³⁺ , Lu ³⁺ and Ba ²⁺ is 35 cation% or less, and the content of O ^2- is 5 to 85 anionic%, F ^- content of 15 to 95 anionic%, O ^2- content relative to the content of P ⁵⁺ molar ratio of O ^2- / P ⁵⁺ 3.33 or more.

In one embodiment, the total content of Ti ⁴⁺ , Nb ⁵⁺ and W ⁶⁺ in the optical glass is 0.1 cation% or more.

In one embodiment, the total content of Ti ⁴⁺ , Nb ⁵⁺ and W ⁶⁺ in the optical glass is 4 cation% or less.

Another aspect of the present invention relates to an optical element formed of the above-mentioned optical glass. [Inventive effect]

According to an aspect of the present invention, it is possible to provide an optical glass formed of a fluorophosphate glass that can suppress an increase in specific gravity, has a large partial dispersion ratio, and can be stably produced. Furthermore, according to one aspect of this invention, the optical element formed from the said optical glass can be provided.

Hereinafter, one embodiment of the present invention will be described. In the present invention and the present specification, the content and total content of the cationic component are expressed as cationic% unless otherwise specified, and the content and total content of the anionic component are expressed as anionic% unless otherwise specified. Here, “cation%” is a value calculated according to “(number of cations of interest / total number of cations in glass component) × 100”, and means a mole percentage of the amount of cations of interest with respect to the total amount of cation components . In addition, “anion%” means “(the number of anions of interest / total number of anions in the glass component) × 100”, and means a mole percentage of the amount of anions of interest with respect to the total amount of the anion components. The content of the glass component can be quantified by known methods, such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), and ion chromatography.

(P ⁵⁺ ) P ⁵⁺ is an essential component for forming a network structure of glass. In order to maintain the thermal stability well, the content of P ⁵⁺ in the optical glass is 3% or more. In order to maintain good chemical durability, low dispersion, and abnormal partial dispersion, the content of P ⁵⁺ in the optical glass is 45% or less. According to the above viewpoint, the preferred lower limit of the content of P ⁵⁺ is 4%, the more preferred lower limit is 5%, and the further preferred lower limit is 6%. In addition, a preferable upper limit of the content of P ⁵⁺ is 40%, and a more preferable upper limit is 35%.

(Al ³⁺ ) Al ³⁺ is an essential component, and plays a role of improving thermal stability, chemical durability, and workability, and a role of increasing refractive index. Therefore, the content of Al ³⁺ in the optical glass is in the range of 5 to 40%. From the above viewpoints, the preferred lower limit of the content of Al ³⁺ is 7%, a more preferred lower limit is 9%, and a further preferred lower limit is 11%. From the above viewpoints, the preferable upper limit of the content of Al ³⁺ is 38%, the more preferable upper limit is 36%, and the more preferable upper limit is 34%.

From the viewpoint of ensuring good thermal stability of the glass, the total content of P ⁵⁺ and Al ³⁺ (P ⁵⁺ + Al ³⁺ ) is preferably 30% or more, more preferably 33% or more, and even more preferably More than 35%. Maintaining the good chemical durability, maintaining low dispersion property and anomalous partial view dispersibility viewpoint, the total content of Al ^3+, and P ⁵⁺ (P ⁵⁺ + Al ³⁺⁾ is preferably 55% or less, more preferably 53% or less, more preferably 50% or less.

(Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ ) Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ can effectively improve the partial dispersion ratio. Although the rare earth component also shows the effect of increasing the partial dispersion ratio, in terms of the effect of improving the partial dispersion ratio per unit content expressed by cationic%, Ti ⁴⁺ , Nb ⁵⁺ , and W ^{6+ are} more than the rare earth component. Big. Therefore, by Ti ⁴⁺ , Nb ⁵⁺ , and W ⁶⁺ , it is possible to suppress the increase in the specific gravity of the glass and increase the partial dispersion ratio. Therefore, in order to suppress an increase in specific gravity and improve a partial dispersion ratio, the optical glass contains at least one component selected from the group consisting of Ti ⁴⁺ , Nb ⁵⁺ and W ⁶⁺ . From the viewpoint of further improving the partial dispersion ratio, the total content of Ti ⁴⁺ , Nb ⁵⁺ and W ⁶⁺ (Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ ) is preferably 0.1% or more. On the other hand, when the total content of Ti ^4+, Nb ^5+, and W ⁶⁺ is too large, the thermal stability decreases, volatile or increase the melt during the presence of molten glass, thus resulting in streaks in the homogeneity of the glass drop Wait for the case where the characteristics of the glass deviate from the expected value. Therefore, from the viewpoint of suppressing the volatility of the molten glass liquid, the total content of Ti ⁴⁺ , Nb ⁵⁺ and W ⁶⁺ is preferably 4% or less, more preferably 3.5% or less, and even more preferably 3% or less.

From the viewpoint of suppressing an increase in specific gravity and increasing a partial dispersion ratio, the preferable contents of Ti ⁴⁺ , Nb ⁵⁺ , and W ⁶⁺ are as follows. The preferred lower limit of the content of Ti ⁴⁺ is 0.1%, the more preferred lower limit is 0.5%, the further preferred lower limit is 1%, the preferred upper limit of the content of Ti ⁴⁺ is 4%, and the preferred upper limit is 3.5%. The best upper limit is 3%. The preferred lower limit of the content of Nb ⁵⁺ is 0.1%, the more preferred lower limit is 0.5%, the further preferred lower limit is 1%, the preferred upper limit of the content of Nb ⁵⁺ is 4%, and the preferred upper limit is 3.5%. The best upper limit is 3%. The preferred lower limit of the content of W ⁶⁺ is 0.1%, the more preferred lower limit is 0.5%, the further preferred lower limit is 1%, the preferred upper limit of the content of W ⁶⁺ is 4%, and the preferred upper limit is 3.5%. The best upper limit is 3%.

(Rare earth component, Ba ²⁺ ) In order to suppress the increase in specific gravity, in the above-mentioned optical glass, the content of the rare earth component (Y ³⁺ , La ³⁺ , Gd ³⁺ , Yb ³⁺ , Lu ³⁺ ) and Ba The total content of ²⁺ , that is, the total content of Y ³⁺ , Gd ³⁺ , La ³⁺ , Yb ³⁺ , Lu ³⁺ and Ba ²⁺ is 35% or less. Since the optical glass contains at least one component selected from the group consisting of Ti ⁴⁺ , Nb ⁵⁺ and W ⁶⁺ , it is possible to suppress the total content of the rare-earth component which can increase the partial dispersion ratio but also causes an increase in specific gravity. From the viewpoint of improving the partial dispersion ratio, the lower limit of the total content of Y ³⁺ , Gd ³⁺ , La ³⁺ , Yb ³⁺ , Lu ^3+, and Ba ²⁺ is preferably 5%, and the more preferable lower limit is 10%. From the viewpoint of suppressing an increase in specific gravity, a preferable upper limit of the total content of Y ³⁺ , Gd ³⁺ , La ³⁺ , Yb ³⁺ , Lu ^3+, and Ba ²⁺ is 30%, and a more preferable upper limit is 25%. . Y ³⁺ , Gd ³⁺ , La ³⁺ , Yb ^3+, and Lu ³⁺ are relatively insoluble components when melting glass, so the melting temperature is increased in order to dissolve these components. However, if the melting temperature is increased, the volatility of the molten glass liquid is increased, components such as Ti ⁴⁺ , Nb ⁵⁺ , and W ⁶⁺ are volatilized, the characteristics of the glass are changed, or streaks are generated, which deteriorates the homogeneity of glass. From the viewpoint of suppressing the increase of the glass melting temperature and the volatility of the molten glass liquid, the preferred upper limit of the total content of Y ³⁺ , Gd ³⁺ , La ³⁺ , Yb ³⁺ and Lu ³⁺ is 5%, more The best upper limit is 3%. The other part, from the viewpoint of improving dispersion ratio of the starting portion, the Y ^3+, the preferred lower limit of Gd ^3+, La ^3+, Yb ³⁺ and Lu ³⁺ total content of 0%, the lower limit is more preferably 1%. Moreover, the said rare earth component has the tendency for the component which is difficult to color glass even in a rare earth.

Next, the above-mentioned five kinds of rare earth components (Y ³⁺ , Gd ³⁺ , La ³⁺ , Yb ³⁺ , Lu ³⁺ ) will be described one by one. Y ³⁺ has the effect of maintaining thermal stability and increasing the refractive index, but if it is contained too much, the specific gravity increases and the thermal stability tends to decrease. Therefore, the content of Y ³⁺ is preferably in the range of 0 to 5%, more preferably in the range of 0 to 4%, even more preferably in the range of 0 to 3%, and may also be 0%. Gd ³⁺ plays a role of increasing the refractive index, but if it is contained too much, it tends to increase specific gravity and decrease thermal stability. Therefore, the content of Gd ³⁺ is preferably in the range of 0 to 5%, more preferably in the range of 0 to 4%, still more preferably in the range of 0 to 3%, and may also be 0%. La ³⁺ plays a role of increasing the refractive index, but if it is contained too much, it tends to increase specific gravity and decrease thermal stability. Therefore, the content of La ³⁺ is preferably in the range of 0 to 5%, more preferably in the range of 0 to 4%, even more preferably in the range of 0 to 3%, and may also be 0%. Yb ³⁺ plays a role of increasing the refractive index, but if it is contained too much, it tends to increase specific gravity and decrease thermal stability. Therefore, the content of Yb ³⁺ is preferably in the range of 0 to 5%, more preferably in the range of 0 to 4%, still more preferably in the range of 0 to 3%, and may also be 0%. Lu ³⁺ plays a role of increasing the refractive index, but if it is contained too much, it tends to increase the specific gravity and decrease the thermal stability. Therefore, the content of Lu ³⁺ is preferably in the range of 0 to 5%, more preferably in the range of 0 to 3%, still more preferably in the range of 0 to 4%, and may also be 0%.

Ba ²⁺ plays a role in increasing the refractive index and a partial dispersion ratio, and also plays a role in improving devitrification resistance. However, if the content of Ba ²⁺ is too large, the specific gravity of the glass increases. From the viewpoints of increasing the refractive index, the partial dispersion ratio, and improving the devitrification resistance, a preferable lower limit of the content of Ba ²⁺ is 3%, a more preferable lower limit is 5%, and a further preferable lower limit is 8%. On the other hand, from the viewpoint of suppressing an increase in the specific gravity of glass, a preferable upper limit of the content of Ba ²⁺ is 25%, a more preferable upper limit is 23%, and a more preferable upper limit is 20%.

(O ^2- ) O ^2- is an essential component and plays a role in maintaining thermal stability. In order to maintain thermal stability and high refractive index, the content of O ^2- in the optical glass is 5 to 85%. From the viewpoint described above, the content of O ^2- is preferably 10% or more, more preferably 15% or more, and still more preferably 20% or more. On the other hand, in order to maintain low dispersion and abnormal partial dispersibility, the content of O ^2- is preferably 80% or less, and more preferably 75% or less.

(F ^-) F ^- as essential components, in imparting low dispersion property, is an important component of the abnormal partial dispersion. In addition, it also plays a role of reducing the glass transition temperature. F ^- upper limit of the content is 95%. In order to maintain a low dispersion property and anomalous partial dispersion property, F ^- is the lower limit of the content of 15%. According to the above reasons, F ^- preferred upper limit of the content is 90%, the upper limit is more preferably 85%, more preferred upper limit is 80%. A preferable lower limit of the content of F- is 25%.

(Molar ratio O ^2- / P ⁵⁺ ) The optical glass includes at least one component selected from the group consisting of Ti ⁴⁺ , Nb ^5+, and W ⁶⁺ that exhibit volatility during melting. In order to suppress the volatility of the glass melting process, in the above optical glass, the content of O ^2- with respect to the content of P ⁵⁺ molar ratio of O ^2- / P ⁵⁺ is set to 3.33 or more. By setting the molar ratio O ^2- / P ⁵⁺ to 3.33 or more, the volatility of the fluorophosphate glass during melting can be suppressed, and the erosion and reactivity can be further suppressed. The state in which the molar ratio O ^2- / P ⁵⁺ is 3.33 or more corresponds to a tripolyphosphate structure or a diphosphate structure. In the molten glass, if O ^2- and P ⁵⁺ are present at a ratio corresponding to a tripolyphosphoric acid structure or a diphosphoric acid structure, the volatility, aggressiveness, and reactivity of the molten glass can be reduced. Among them, if the molar ratio O ^2- / P ⁵⁺ is 7/2 or more, that is, 3.50 or more, the existence ratio of O ^2- and P ⁵⁺ in the molten glass corresponds to the diphosphoric acid structure, and the volatility of the molten glass can be made. , Erosion and reactivity are further reduced. In the glass composition of the above-mentioned optical glass, by reducing the molar ratio O ^2- / P ⁵⁺ to 3.33 or more, it is possible to suppress the decrease in Ti ⁴⁺ , Nb ⁵⁺ , and W ⁶⁺ when the glass is melted. As a result, it is possible to suppress variations in characteristics due to composition changes, and further suppress generation of streaks due to volatilization, and obtain a glass having high homogeneity. In addition, since the corrosiveness of glass at the time of melting can also be suppressed, it is possible to suppress the erosion of the melting vessel and the stirring rod used when homogenizing the glass. Therefore, it is possible to prevent the platinum or the platinum alloy constituting the melting vessel or the stirring rod from being mixed into the glass due to erosion and becoming foreign matter, thereby deteriorating the quality of the glass. The lower limit of the molar ratio O ^2- / P ⁵⁺ is 3.50. Further, the glass from the viewpoint of easy, molar ratio of O ^2- / preferred upper limit of P ⁵⁺ 4.00. The better upper limit for Mohr's ratio O ^2- / P ⁵⁺ is 3.80.

(Alkaline earth metal component) Ba ²⁺ , Sr ²⁺ , Ca ²⁺ , and Mg ^{2+ which} are alkaline earth metal components are cation components that adjust the viscosity of glass, adjust the refractive index, and improve the thermal stability. In order to obtain the above effect, the total content of alkaline earth metal ions R ²⁺ (Ba ²⁺ + Sr ²⁺ + Ca ²⁺ + Mg ²⁺ ) is preferably 25% or more, more preferably 30% or more, and even more preferably 35 % Or more, more preferably 40% or more.

On the other hand, if the total content R ^{2+ of the} alkaline earth metal ions is too large, the thermal stability is reduced. Therefore, the total content R ²⁺ of the alkaline earth metal ions is preferably 60% or less. The more preferable upper limit of R ²⁺ is 55%, the more preferable upper limit is 53%, and the more preferable upper limit is 50%.

As mentioned above, from the viewpoint of suppressing the increase of specific gravity, the total content of Ba ^{2+ and} the content of rare earth components (Y ³⁺ , Gd ³⁺ , La ³⁺ , Yb ³⁺ , Lu ³⁺ ) is limited to 35. %the following. Hereinafter, a preferable content of the alkaline earth metal components other than Ba ^{2+ and} a preferable range of the total content of these components will be described. From the viewpoint of adjusting the viscosity and refractive index of glass to obtain the effect of improving the thermal stability, the total content of Sr ²⁺ , Ca ²⁺ and Mg ²⁺ is R´ ²⁺ (Sr ²⁺ + Ca ²⁺ + Mg A preferred lower limit of ²⁺ ) is 15%, a more preferred lower limit is 18%, and a further preferred lower limit is 20%. On the other hand, from the viewpoint of maintaining the thermal stability of the glass ^{starting, R'2+ (Sr 2+ + Ca} 2+ + Mg 2+) preferred upper limit is 55%, the upper limit is more preferably 50%, more preferably The upper limit is 45%. The preferable contents of Sr ²⁺ , Ca ²⁺ , and Mg ²⁺ are as follows. From the viewpoint of maintaining the thermal stability of the glass, the preferable range of the content of Sr ²⁺ is 0 to 30%, a more preferable upper limit is 25%, a more preferable upper limit is 20%, and a more preferable lower limit is 5%. The lower limit is 10%. From the viewpoint of maintaining the thermal stability of the glass, the preferable range of the content of Ca ²⁺ is 0 to 30%, a more preferable upper limit is 25%, a more preferable upper limit is 20%, a more preferable lower limit is 5%, The lower limit is 10%. From the viewpoint of maintaining the thermal stability of the glass, a preferable range of the content of Mg ²⁺ is 0 to 15%, a more preferable range is 0 to 10%, and a more preferable range is 0 to 5%.

(Zn ²⁺ ) Zn ²⁺ maintains the refractive index and improves the thermal stability. However, if it is contained too much, the dispersion tends to be high, and it is difficult to obtain the required optical characteristics. Therefore, the content of Zn ²⁺ in the optical glass is preferably in the range of 0 to 5%. In order to obtain the above effect, a more preferable upper limit of the content of Zn ²⁺ is 4%, and a more preferable upper limit is 3%.

(Alkali metal component) The alkali metal component is a cationic component which functions to adjust the viscosity of glass and to improve thermal stability. On the other hand, if the total content R ^{+ of} alkali metal ions is too large, the thermal stability tends to decrease. Therefore, a preferable range of the total content R ⁺ of the alkali metal ion is 1 to 25%. From the above viewpoint, a more preferable upper limit of R ⁺ is 25%, a further preferable upper limit is 20%, a more preferable lower limit of R ⁺ is 1%, and a further preferable lower limit is 3%. The total content of alkali metal ions may be the total content of Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ and Cs ⁺ . That is, the alkali metal component can be expressed as Li ⁺ , Na ⁺ , K ⁺ , Rb ⁺ , and Cs ⁺ . Among these alkali metal components, Rb ⁺ and Cs ⁺ are more likely to cause the specific gravity of glass to be increased compared to other alkali metal components. Therefore, the content of Rb ⁺ is preferably 0 to 5%, more preferably 0 to 4%, still more preferably 0 to 3%, and may also be 0%. The content of Cs ⁺ is preferably 0 to 5%, more preferably 0 to 4%, still more preferably 0 to 3 cationic%, and may also be 0 cationic%. From the viewpoint of maintaining the thermal stability of the glass, a preferable range of the content of Li ⁺ is 0 to 25%, a more preferable range is 1 to 20%, and a more preferable range is 3 to 15%. From the viewpoint of maintaining the thermal stability of the glass, a preferable range of the content of Na ⁺ is 0 to 25%, a more preferable range is 0 to 20%, and a more preferable range is 0 to 15%. From the viewpoint of maintaining the thermal stability of the glass, the preferable range of the K ⁺ content is 0 to 5%, a more preferable range is 0 to 4%, and a more preferable range is 0 to 3%.

(Si ⁴⁺ ) Si ⁴⁺ can be contained in a small amount, but if it is contained too much, melting properties and thermal stability tend to decrease. Therefore, the content of Si ⁴⁺ in the optical glass is preferably in the range of 0 to 3%, more preferably in the range of 0 to 2%, even more preferably in the range of 0 to 1%, and may also be 0%.

(B ³⁺ ) B ³⁺ can also be contained in a small amount, but if it is contained too much, the meltability and thermal stability tend to decrease. Therefore, the content of B ³⁺ in the optical glass is preferably in the range of 0 to 3%, more preferably in the range of 0 to 2%, and even more preferably in the range of 0 to 1%. The presence of B ³⁺ in the glass results in a significant increase in the volatility of the molten glass, so it is better that the glass does not contain B ³⁺ .

(Cl ^-) in order to suppress the glass from the tube flowing molten glass wetting the outer periphery of the tube, resulting in suppressing quality degradation due to infiltration glass contains Cl ^- is effective. The preferable range of the content of Cl ^- is 0 to 1%, the more preferable range is 0 to 0.5%, and the more preferable range is 0 to 0.3%. Cl ^- has an effect as a refining agent.

(Other components) In addition to the above components, the optical glass may further contain Sb ³⁺ , Ce ⁴⁺ and the like as a clarifier in a small amount. The total amount of the clarifying agent is preferably 0% or more and less than 1%. Pb, Cd, As, and Th are components that may cause an environmental burden. Therefore, the content of Pb ²⁺ is preferably from 0 to 0.5%, more preferably from 0 to 0.1%, even more preferably from 0 to 0.05%, and it is particularly preferred that Pb ²⁺ is not substantially contained. The content of Cd ²⁺ is preferably 0 to 0.5%, more preferably 0 to 0.1%, still more preferably 0 to 0.05%, and particularly preferably not substantially containing Cd ²⁺ . The content of As ³⁺ is preferably from 0 to 0.1%, more preferably from 0 to 0.05%, even more preferably from 0 to 0.01%, and particularly preferably, As ³⁺ is not substantially contained. The content of Th ⁴⁺ is preferably from 0 to 0.1%, more preferably from 0 to 0.05%, even more preferably from 0 to 0.01%, and particularly preferably not substantially including Th ⁴⁺ . Furthermore, the above-mentioned optical glass can obtain a high transmittance in a wide range of the visible light region. In order to utilize such a feature, it is preferable not to contain a coloring agent. Examples of the colorant include Cu, Co, Ni, Fe, Cr, Eu, Nd, and Er. Regarding the range of the content of Cu, Co, Ni, Fe, Cr, Eu, Nd, and Er represented by cation%, any element is preferably less than 100 cationic ppm, more preferably 0 to 80 cationic ppm, and even more preferably It is 0 to 50 cationic ppm or less, and it is particularly preferable that it is substantially not contained. In addition, Hf, Ga, Ge, Te, Tb and the like are components that do not need to be introduced and are expensive. Therefore, regarding the range of the content of Hf, Ga, Ge, Te, and Tb represented by the cation%, each element is preferably 0 to 0.1%, more preferably 0 to 0.05%, and still more preferably 0 to 0.01. %, More preferably 0 to 0.005%, still more preferably 0 to 0.001%, particularly preferably not substantially included.

[Abbe Number νd, Refractive Index nd] From the viewpoint of utilizing the dispersibility of the abnormal portion, the optical glass preferably has an Abbe number νd in a range of 55 or more. The Abbe number νd is a value indicating properties related to dispersion, and each refractive index nd, nF, and nC of the d-line, F-line, and C-line is expressed as "νd = (nd-1) / (nF-nC)" ( (Formula (1) above). A preferable upper limit of the Abbe number νd is 98, and a more preferable upper limit is 95. On the other hand, in order to make use of the low dispersion, a preferable lower limit of the Abbe number νd is 55, a more preferable lower limit is 58, and a further preferable lower limit is 60. Furthermore, by setting the refractive index nd to be in the following range, the absolute value of the curvature of the optical functional surface of the lens can be reduced (the curve of the optical functional surface of the lens can be made slower) with the same focusing power. Since the curve of the optical functional surface of the lens is slower and easier to make, whether in the case of precision press molding or in the case of grinding and polishing, the use of high refractive index glass can improve the optical component. productivity. Furthermore, by increasing the refractive index, it is possible to provide a glass material suitable for an optical element used in a highly functional and compact optical system. In the optical glass described above, a more preferable range of the refractive index nd is a range that satisfies the following formula (3). nd≥1.66900-0.00254 × νd… (3)

[Partial dispersion property] The partial dispersion property of glass is quantitatively expressed by the partial dispersion ratios Pg, F. Pg and F are expressed as "Pg, F = (ng-nF) / (nF-nC)" using the respective refractive indices ng, nF, and nC of the g-line, the F-line, and the C-line (the above formula (2)). As commercially available low-dispersion glass having an Abbe number νd of 55 or more, for example, FCD1 and FCD705 manufactured by HOYA are known. In the graph with the abscissa νd on the horizontal axis and the partial dispersion ratio Pg, F on the vertical axis, FCD705 is plotted at coordinates (75.50, 0.54), and FCD1 is plotted at coordinates (81.61, 0.5388). 2 point straight line L. This straight line L is roughly expressed as "Pg, F = -0.0002νd + 0.5548". Regarding the commercially available low-dispersion glass having an Abbe number νd of 55 or more, in the graph of the Abbe number νd-partial dispersion ratio Pg, F, the partial dispersion ratio Pg, F is located on the line of or compared to the line L. Side, or high specific gravity. In a preferred embodiment of the optical glass described above, the Abbe number νd and the partial dispersion ratios Pg, F satisfy the following formula (4). Pg, F ＞ -0.0002νd + 0.5548… (4) The optical glass having an Abbe number νd of 55 or more and satisfying the above formula (4) has a large partial dispersion ratio Pg, F with respect to a specific Abbe number νd, which is suitable for high-order Chromatic aberration correction with optical glass.

[Transmittance] The above-mentioned optical glass can be used as an optical glass with little coloration. This optical glass is suitable as a material of an optical element for imaging such as a camera lens and a projection optical element such as a projector. A preferred embodiment of the optical glass is an optical glass having an internal transmittance of 96.5% or more in a thickness of 10 mm in a range of wavelengths from 400 nm to 700 nm. The preferable range of the above-mentioned internal transmittance is 97.0% or more, a further more preferable range is 98.0% or more, and a further more preferable range is 99.0% or more. In addition, glass containing laser ions such as Nd, Eu, and Er, for example, has absorption in the visible light region, and is therefore not suitable for materials for imaging optical elements such as camera lenses and projection optical elements such as projectors.

[Glass Transition Temperature Tg] A preferred aspect of the optical glass is an optical glass having a glass transition temperature Tg of 500 ° C or lower. If the glass transition temperature is low, the heating temperature when the glass is reheated, softened, and press-molded can be reduced. As a result, it is easy to suppress fusion between the glass and the press mold. In addition, since the heating temperature can be lowered, it is also possible to reduce the heat loss of a glass heating device, a press molding die, and the like. Furthermore, since the annealing temperature of glass can also be reduced, the life of an annealing furnace can be extended. The more preferable range of the glass transition temperature is 450 ° C or lower, the more preferable range is 440 ° C or lower, and the more preferable range is 430 ° C or lower.

[Liquid Phase Temperature] A preferred embodiment of the optical glass is an optical glass having excellent thermal stability and a liquid phase temperature of 850 ° C or lower. When the liquidus temperature is low, the melting and molding temperature of the glass can be reduced. As a result, the volatility of the glass during melting and molding can be reduced, and the occurrence of streaks and variations in optical characteristics can be suppressed. A more preferable range of the liquidus temperature is 800 ° C or lower, a further more preferable range is 750 ° C or lower, still more preferably 730 ° C or lower, and still more preferably 700 ° C or lower.

[Specific gravity] The preferred aspect of the optical glass is an optical glass having a specific gravity of 4.0 or less. The more preferable range of the specific gravity is 3.9 or less, and the more preferable range is 3.8 or less.

[Application] The preferred aspect of the optical glass is optical glass for optical lenses or optical glass for prisms.

[Manufacturing method] The above-mentioned optical glass can be obtained, for example, by blending, melting, and molding glass raw materials so that required characteristics can be obtained. As a glass raw material, a phosphate, a fluoride, an alkali metal compound, an alkaline-earth metal compound, etc. can be used, for example. As a glass melting method and a molding method, a known method can be used.

[Glass raw material for press molding, method for manufacturing the same, and method for manufacturing glass molded body] According to an embodiment of the present invention, it is possible to provide a glass raw material for pressing formed from the optical glass, and a glass molded body formed from the optical glass. , And their manufacturing methods. The glass raw material for press molding means a glass block which is heated for press molding. Examples of glass raw materials for press molding include precision press molding preforms, glass raw materials (press glass frit) for press molding of optical element blanks, and the like. Quality glass blocks. The glass raw material for press molding can be manufactured through the process of processing a glass molded object. The glass molded body can be produced by heating and melting the glass raw material as described above, and molding the obtained molten glass. Examples of the processing method of the glass molded body include cutting, grinding, and polishing.

[Optical element blank and manufacturing method thereof] According to an embodiment of the present invention, it is possible to provide an optical element blank made of the above-mentioned optical glass. The optical element blank is a glass molded body having a shape similar to that of an optical element to be manufactured. The optical element blank can be produced by a method such as molding glass into a shape that adds a processing amount removed by processing to the shape of the optical element to be manufactured. For example, it is possible to press-mold by heating and softening the glass material for press-molding (secondary hot-pressing method); and to press-mold the molten glass block by a known method (directly) Pressing method) and the like to produce an optical element blank.

[Optical element and manufacturing method thereof] According to an embodiment of the present invention, an optical element formed of the above-mentioned optical glass can be provided. Examples of the types of optical elements include lenses such as spherical lenses and aspheric lenses; prisms; diffraction gratings, and the like. Examples of the shape of the lens include many shapes such as a lenticular lens, a plano-convex lens, a bi-concave lens, a plano-concave lens, a convex-concave lens, and a meniscus lens. The optical element can be manufactured by a method including a step of processing a glass molded body formed of the optical glass. Examples of the processing include cutting, cutting, rough grinding, fine grinding, and polishing. When such processing is performed, damage can be reduced by using the above glass, and a high-quality optical element can be stably supplied.

Examples Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the embodiments shown in the examples.

(Example 1) In order to have the glass composition shown in Table 1, the corresponding raw materials, such as phosphate, fluoride, oxide, etc., were used as raw materials to introduce each component, and the raw materials were weighed and sufficiently mixed to form a blended raw material. This blended raw material was put into a crucible made of platinum, and heated and melted. After melting, the molten glass is poured into a mold, and it is left to cool to near the glass transition temperature, and then immediately placed in an annealing furnace, and annealed in the glass transition temperature range for about one hour, and then cooled in the furnace to room temperature, thereby obtaining Each optical glass of No. 1 to No. 75 shown in Table 1. The optical glass obtained was magnified and observed using an optical microscope, and no precipitation of crystals, foreign matter such as platinum particles from the platinum crucible, bubbles, and streaks were not observed. The characteristics of the optical glass obtained in this manner are shown in Table 1.

Each characteristic of optical glass is measured by the method shown below. (i) Refractive index nd, ng, nF, nC, and Abbe number νd The refractive index nd was measured on a glass obtained by cooling at a cooling rate of -30 ° C / hour using a refractive index measurement method developed by the Japan Optical Glass Industry Association , Ng, nF, nC, and the Abbe number νd is calculated according to the formula (1). (ii) Partial dispersion ratio Pg, F Based on the refractive indexes ng, nF, and nC measured in the above (i), the partial dispersion ratio Pg, F was calculated according to the formula (2). (iii) Glass transition temperature Tg was measured using a differential scanning calorimeter (DSC3300) manufactured by NETZSCH at a temperature increase rate of 10 ° C / min. (iv) Liquid phase temperature LT Weigh 50 g of glass in a platinum crucible, melt it at 1000 ° C for 20 minutes with a lid made of platinum, hold it at a predetermined temperature for 2 hours, and then cool to room temperature. The surface and the inside of the glass were observed visually and magnified with a light microscope (100 times magnification), and the presence or absence of crystal precipitation was checked. In all the optical glasses of No. 1 to No. 75 shown in Table 1, no precipitation of crystals was observed in the glass that was cooled after being held at 850 ° C for 2 hours. In this way, it was confirmed that the liquidus temperature LT of all the optical glasses of No. 1 to No. 75 shown in Table 1 was 850 ° C or lower. (v) Specific gravity is measured by the Archimedes method. (vi) Evaluation of the amount of reduction of volatilization of glass components before and after melting. A batch of glass raw materials were prepared so that the yield W was 150 to 200 g. The batches of raw materials were added to a platinum crucible, covered with a platinum lid, and the batch was measured. Weight of raw materials, platinum crucible and lid. Then, the platinum crucible containing the batch of raw materials was capped, and the batch of raw materials and the crucible were placed in a glass melting furnace, and the glass was melted by heating at 1,050 ° C for 1.5 hours. After 1.5 hours, the weight of the platinum crucible was measured together with the contents (fused glass) in a state covered with a platinum lid. The total mass of the platinum crucible, the lid made of platinum, and the batch of raw materials before melting the glass is X, the mass of the mass of the raw material is set to Y, and the mass of the platinum crucible after melting the glass, the lid of platinum, and the mass of the molten glass When the total is set to Z, the mass of the glass component lost from the molten glass in the crucible due to volatilization during melting is {X- (YW)}-Z. YW is the mass of a gas generated by thermally decomposing a batch of raw materials. This gas is not a glass component, but, for example, when carbonates, nitrates, sulfates, and hydroxides are used in batch raw materials, CO ₂ , NO ₂ , SO ₂ , H ₂ O, and the like generated during these thermal decompositions. The amount of these gases generated can be calculated by a known method. The amount of reduction in volatilization of glass components before and after melting is the value of the glass component mass ({X- (YW)}-Z) lost from the molten glass in the crucible due to volatilization during melting, which can be calculated as [{ X- (YW)}-Z] / WA is calculated as a percentage. In Table 1, the magnitude of the amount of reduction in volatilization of the glass component before and after melting is indicated by A, B, and C for each glass of the examples. Glass with less than 3% reduction of volatilization before and after melting is A, glass with less than 3% volatility reduction before and after melting is B, and glass with volatility reduction before and after melting is 5 % Or more of glass is C. In addition, for each of the optical glasses numbered 1 to 75 shown in Table 1, the internal transmittance of 10 mm in thickness was measured in accordance with JOGIS 17-2012 "Measurement Method of Internal Transmittance of Optical Glass" by the Japan Optical Glass Industry Association. As a result, all the optical glasses had an internal transmittance of 96.50% or more.

[Table 1-1] Table 1

[Table 1-2] Table 1 (continued)

[Table 1-3] Table 1 (continued)

[Table 1-4] Table 1 (continued)

[Table 1-5] Table 1 (continued)

[Table 1-6] Table 1 (continued)

[Table 1-7] Table 1 (continued)

[Table 1-8] Table 1 (continued)

[Table 1-9] Table 1 (continued)

[Table 1-10] Table 1 (continued)

[Table 1-11] Table 1 (continued)

[Table 1-12] Table 1 (continued)

[Table 1-13] Table 1 (continued)

[Table 1-14] Table 1 (continued)

[Table 1-15] Table 1 (continued)

In FIG. 1, the Abbe number νd and the partial dispersion ratios Pg, F are used as coordinates to describe the optical characteristics of the above-mentioned optical glasses. In FIG. 1, each of the above-mentioned optical glasses is distributed in a range where the partial dispersion ratio Pg, F is larger than the straight line L.

(Comparative Examples 1 to 4) As Comparative Examples 1 to 4, four types of glasses shown in Table 2 were evaluated. Comparative Example 1 is Example 9 described in Table 4 of Japanese Patent Application Laid-Open No. 2005-112717. In Comparative Example 1, the total content of Y ³⁺ , Gd ³⁺ , La ³⁺ , Yb ³⁺ , Lu ^3+, and Ba ²⁺ exceeded 35 cation%, which was a specific gravity. Comparative Example 2 is Example 4 described in Japanese Patent Application Laid-Open No. 2011-037637 (Patent Document 2). In Comparative Example 2, the molar ratio O ² / P ^{5+ was} smaller than 3.33, and more volatilization occurred during glass melting. [{X- (YW)}-Z] / W was 9.70%. Comparative Example 3 is a composition example in which the molar ratio O ^2- / P ^{5+ is} smaller than 3.33. In Comparative Example 3, the molar ratio O ² / P ^{5+ was} smaller than 3.33, and the glass was more volatile during melting, and [{X- (YW)}-Z] / W was 5.20%. Comparative Example 4 is a composition example not including any of Ti ⁴⁺ , Nb ⁵⁺ , and W ⁶⁺ . In Comparative Example 4, the partial dispersion with respect to the Abbe number νd was smaller than Pg and F.

[Table 2]

(Example 2) Using each optical glass produced in Example 1, a lens blank was produced by a known method, and the lens blank was processed by a known method such as polishing to produce various lenses. The produced optical lenses are various lenses such as a lenticular lens, a lenticular lens, a plano-convex lens, a plano-concave lens, a concave-convex meniscus lens, and a convex-convex meniscus lens. Each lens has a small specific gravity and a large partial dispersion ratio Pg, F relative to the Abbe number νd, and is therefore suitable for high-order chromatic aberration correction. In the same manner, a prism was produced using various optical glasses produced in Example 1.

It should be understood that the embodiments disclosed this time are illustrative and not restrictive in all respects. The scope of the present invention is shown by the scope of the patent claim, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the scope of the patent claim. For example, the glass composition exemplified above can be produced by adjusting the composition described in the specification to produce an optical glass according to an embodiment of the present invention. It is needless to say that two or more matters described in the description as examples or preferable ranges can be arbitrarily combined.

no.

FIG. 1 shows the Abbe number νd on the horizontal axis and the partial dispersion ratio Pg on the vertical axis, F, the Abbe number νd and the partial dispersion ratio Pg on each optical glass of Examples, Comparative Examples, and commercially available products. F drawing.

Claims (4)

An optical glass in which: the content of P ⁵⁺ is from 3 to 45 cation%; the content of Al ³⁺ is from 5 to 40 cation%; and the content is selected from the group consisting of Ti ⁴⁺ , Nb ⁵⁺ and W ⁶⁺ At least one of the components; the total content of Y ³⁺ , Gd ³⁺ , La ³⁺ , Yb ³⁺ , Lu ^3+, and Ba ²⁺ is less than 35 cationic%; the content of O ^2- is 5 to 85 anionic%; F ^- an amount of 15 to 95 anionic%; O ^2- content relative to the content of P ⁵⁺ molar ratio of O ^2- / P ⁵⁺ 3.33 or more. The optical glass according to item 1 of the scope of patent application, wherein the total content of Ti ⁴⁺ , Nb ⁵⁺ and W ⁶⁺ is 0.1 cation% or more. The optical glass according to item 1 or 2 of the scope of patent application, wherein the total content of Ti ⁴⁺ , Nb ⁵⁺ and W ⁶⁺ is 4 cation% or less. An optical element is formed of the optical glass described in any one of claims 1 to 3 of the scope of patent application.