TW200948736A - Optical glass, preform for precision press molding using the optical glass, and optical element using the optical glass - Google Patents

Abstract

Disclosed is an optical glass comprising, by mass based on the following oxides, B2O3: 18 to 30%, SiO2: 3 to 12%, La2O3: 15 to 30%, Gd2O3: 20.5 to 30%, ZnO: 20 to 30%, Li2O: 0.1 to 2%, and ZrO2: 0.1 to 5% as indispensable components, the total contents of ZnO and Li2O being 20 to 30%. The optical glass has a refractive index (nd) of 1.73 to 1.76, an Abbe number (vd)

Description

[Technical Field] The present invention relates to an optical glass having high refractive index and low dispersion, a preform for precision press molding using the same, and an optical element using the same. [Prior Art] In recent years, with the popularization of high-definition and small-sized digital cameras or mobile phones with cameras, the demand for lightweight and miniaturization of optical systems is rapidly increasing. In response to these demands, optical design using high-performance glass aspheric lenses is becoming mainstream. In particular, a large-diameter aspherical lens using a glass exhibiting a high refractive index and a low dispersion property is becoming an important component in optical design. Further, as a method of manufacturing an aspherical lens, in consideration of productivity and manufacturing cost, a precision press molding method which does not require a polishing step is becoming mainstream. The precision press forming method is roughly classified into a direct pressing method in which molten glass is directly dropped into a mold and pressed in this state, and a glass having a specific quality and shape is formed at a time by self-melting the glass drop φ. The molded body (hereinafter referred to as "glass preform formation"), and the obtained glass preform is placed in a mold to be reheated and press-formed by reheat pressing. In the latter reheat pressing method, press formability is important, but it is also important to produce a high-precision glass preform (glass preform forming property) from molten glass. As a glass which exhibits a high refractive index and a low dispersion property, a glass mainly composed of B2?3_La2?3 is known. However, the focus is on the improvement of chemical durability, devitrification resistance or press formability, and the preparation of the glass is 139318.doc 200948736 ^ Forming! Raw, that is, the liquidus temperature is low, the devitrification is not easy (devitrification resistance), and the suitable viscosity (the viscosity at the liquidus temperature, for example, 6 to 15 x dPa.s) is not necessarily sufficient. . On the other hand, as the optical glass, the lower the press forming temperature, the more durable the mold, the shorter the forming cycle and the higher the productivity, and therefore the lower the forming temperature. In order to solve the above problems, in the patent literature, a glass having B2〇3_Si〇2_La2〇3-Gd2〇3-ZnO as a main component has been proposed. Further, in Patent Document 1, the optical glass composition having a refractive index of 1.73 or more and an Abbe number of 48 or more is not particularly sufficient. Further, in Patent Document 2, it is proposed that B2〇3-La2〇3_ZnO-Li2〇 is used as a component, nd=1.66 to 1.77, vd=43 to 55, and a deformation point of 620. (The following is a glass which exhibits a high refractive index and a low dispersion characteristic. Similarly, in Patent Document 3, it is proposed that B2〇3_La2〇3_Gd2〇3_Zn〇Li2〇 is an essential component, nd=1.68~1.8, Vd= 44 to 53, a glass having a deformation point of 63 〇 ° C or less and exhibiting high refractive index and low dispersion characteristics. However, the optical glass of Patent Document 2 and Patent Document 3 contains La 2 〇 3 or [seven ... and Gd 2 〇 3 The two components are not optimal because of the ratio of LasO3 to Gd2〇3, so the liquidus temperature is very high, and the formability of the glass preform is not necessarily sufficient. Further, in Patent Document 4, B203-SiO2-La203 is proposed. -Gd203-Zn〇-Zr02 as an essential component, nd = 1.72 to 1.83, vd = 45 to 55, glass having a glass transition temperature of 63 (TC and exhibiting high refractive index and low dispersion characteristics. However, Patent Document 4 In the optical glass proposed in the present invention, the total content of Li2〇 and ZnO which are components which contribute to lowering the forming temperature is less than 20%. Therefore, the glass transition point is high, and the press formability is not necessarily sufficient. [Patent Document 1] Japanese Patent Laid-Open No. 2006-111482 [Patent Document 2] Japanese Patent No. 3,554,461 [Patent Document 3] Japanese Patent Laid-Open No. 3,548,462 [Patent Document 4] Japanese Patent Laid-Open Publication No. 2002-249337 Problem]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical glass which has high refractive index, low dispersion and steep optical characteristics, is not easily devitrified, is excellent in mold formability, and has a low molding temperature and is excellent in press formability. [Technical means for solving the problem] The present invention provides an optical glass containing the following components as an essential component based on the following oxides: B2〇3: 18 to 3 0%,

Si〇2 : 3 to 12%,

La2〇3: 15~30%, Gd2〇3:20.5~300/〇, Zn〇: 20~3 0%, Li2〇: 0.1~2%, and Zr〇2: 0.1~5%, 1 with WO The total content is 2 〇 to 3 〇%, the refractive index & heart is 1.76, the Abbe number (Vd) is 48 to 51, and the glass transition temperature is 58 〇t or less. In the case of Ma Shou-Ben, the glass preform is provided for the press-molding of the optical glass, and the optical glass is based on the oxide and is expressed by mass%, and contains the following components as essential components: B2〇3: 18~3Q%, Sic>2: 3~12%, La2〇3: 15~30%, Gd2〇3: 22~3〇%, Zn〇·20~30%, Li2〇: (Μ 〜2%, and 〇2 : , and the total content of Zn(^Li2〇 is 20 to 30%, and the refractive index of the optical glass (η〇 is 1.73 to 1.76, and the Abbe number (vd) is 48 to 51). The glass transition temperature (Tg) is 580 ° C or less. [Effects of the Invention] The optical glass of the present invention (hereinafter referred to as the present glass) has a high refractive index of the refractive index nd=1.73 to 1_76 and an Abbe number Vd=48. ～M has low dispersion and thus has better optical properties for use as a large-diameter lens for aspherical surfaces. Since the glass has a glass transition temperature (Tg) as low as 58 〇 or less, the press forming temperature is low and it is used for press forming. The durability of the mold is improved, and since the molding cycle can be shortened, the productivity of press molding is also excellent. Further, the glass is more excellent. The mass ratio is 〇.4~〇.6, and it is better that the liquidus temperature (1\) is 1000. (: The following. By this, the glass has excellent resistance to devitrification and liquidus temperature. The lower viscosity is 8 1 5 dPa s 'The preform is also excellent in moldability. Therefore, the glass is used as a large aspherical π (four) mirror glass, and is balanced in optical properties, glass preform formability, and press formability. [Embodiment] The reason for setting each component of the glass is described below. In the glass, B2〇3 forms a glass skeleton and is a component which lowers the liquidus temperature TL. In this glass, The content of b is ^(tetra) quality 139318.doc 200948736 quantity % (the mass % is simplified to %). If the content of b2〇3 is less than 8%, it is difficult to vitrify, or the liquidus temperature TL will become high. The phase temperature Tl is preferably 疋 such that the B2〇3 content is 18.5°/. or more. If the b2〇3 content is 19% or more, the liquidus temperature is lowered and the Abbe number is increased to 48 to 51, thereby being better. The content of B2〇3 is 19.5% or more. On the other hand, if the content of B2〇3 of the glass exceeds 30°/, Further, there is a decrease in the refractive index nd or a decrease in chemical durability such as water resistance. In the present invention, ❹ in view of the refractive index, it is preferred that the content of 1〇3 is 28% or less, and more preferably B2〇3. The content is 27% or less, and particularly preferably, the b2〇3 content is 26% or less. In the present glass, S1〇2 is the same as B2〇3, which forms a glass skeleton to stabilize the glass, and suppresses glass preforming. The component that is devitrified during body formation is an essential component. In the present glass, the Si〇2 content is 3 to 12%. From the viewpoint of suppressing devitrification or viscosity adjustment at the time of forming the glass preform, it is preferable that the content of Si〇2 is 35% or more, and more preferably, the content of 8丨〇2 is 4%. on. For the same reason, it is particularly preferable to make the Si〇2 content 4.5% or more. On the other hand, if the content of Sl 2 exceeds 12%, the press forming temperature may become too high, and the refractive index nd may become too low. (4) The content of (10) is - ιι·5% or less, and more preferably the Si〇2 content is 11% or less. For the same reason, it is particularly preferable that the Si〇2 content is 1% or less. In the present glass, La2〇3 is an essential component for increasing the refractive index nd and improving chemical durability. In the present glass, the content of La2〇3 is such that if the content of La2〇3 does not reach 5%, the refractive index will become 139318.doc 200948736. It is preferred that the La2〇3 content is 18. /. More preferably, the La2〇3 content is 19% or more. Particularly preferably, the Lkh content is 2% or more. On the other hand, if the La2〇3 content exceeds 30°/. However, it is difficult to vitrify and the temperature becomes high, and the liquidus temperature T1 becomes high. It is preferred that ["Ο; content is 27% or less, more preferably, the content of La2〇3 is 26% or less. Particularly preferably, the content of La203 is 25% or less. In the present glass, 'Gd2〇3 and La2〇3 In the same manner, the component which increases the refractive index and improves the long-term property is an essential component. In the present glass, the Gd2〇3 content is 20·5 to 30%. If the Gd203 content is less than 20.5%, the refractive index nd In order to increase the refractive index, it is preferred to make the Gd2〇3 content 21% or more, and more preferably, the Gd2〇3 content is 22% or more, and particularly preferably, the Gd2〇3 content is 22· On the other hand, when the content of Gd2〇3 exceeds 30%, it is difficult to vitrify, the molding temperature becomes high, and the liquidus temperature 1 becomes high. Preferably, the Gd2〇3 content is 29% or less. More preferably, the Gd2〇3 content is 28% or less. Particularly preferably, the Gd2〇3 content is 27% or less. In the present glass, the liquid phase temperature TL can be obtained by containing two components of La2〇3 and Gd203. The effect of optimizing the ratio of La2〇3 to Gd203' has the effect of greatly reducing the liquidus temperature Tl. That is, from the viewpoint of the liquidus temperature TL, it is preferable. It is a relationship that satisfies the mass ratio of La2〇3/(La2〇3 + Gd2〇3) (hereinafter referred to as the ratio of La) to 〇.4 to 0.6. More preferably, the ratio of La is 〇·41 to 55, especially Preferably, the La ratio is 0.42 to 0.54. In the present glass, the 'Zn 〇 system stabilizes the glass, and the component which lowers the molding temperature or the melting temperature' is an essential component. In the present glass, the Zn 〇 content is 139318.doc 200948736 20 ~301⁄4. Further 'the content of Zn〇 is expressed as % of molybdenum as 29 5~4〇 mol%. If the content of Zn0 is less than 20%', the glass will become unstable and the chemical durability will be lowered. Self-forming temperature and melting In terms of temperature, it is better to make

The Zn 〇 content is 20% or more, and more preferably, the ZnO content is 21.0% or more. For the same reason, it is particularly preferable to make the 211 〇 content to be 21.6% or more. On the other hand, in the present glass, when the ZnO content exceeds 3 Å/0, the stability of the glass is deteriorated, and devitrification is likely to occur. It is preferred that the Zn 〇 content is 27 〇 /. The following is more preferable because the Zn 〇 content is 26% or less. From the viewpoint of financial devitrification, it is particularly preferable to make the ZnO content 25% or less. In the present glass, the component which stabilizes the glass by the LhO system and lowers the molding temperature and the melting temperature is an essential component. In the present glass, the Li2〇 content is 0.1 to 2%. If the Li2〇 content is less than 0.1%, the forming temperature or the melting temperature may become too high. It is preferred that the LhO content is 0.2% or more, and more preferably the LhO content is 0.3% or more. For the same reason, it is particularly preferable to make the Li20 content 4% or more. On the other hand, when the LhO content exceeds 2%, the devitrification is likely to occur, and the chemical durability is lowered or the volatilization of the components at the time of melting becomes severe. It is preferred that the LhO content is 18% or less, and more preferably the Li2? content is less than 96%. Particularly preferably, the Li2 bismuth content is 1.5% or less. In the present glass, both the composition of LizO and ZnO are required as an essential component in order to achieve both the moldability and the press formability of the glass preform. In the present glass, the total content of ZnO and LhO (hereinafter referred to as znLi combined amount) is 20 to 30%. If the amount of ZnLi is less than 20%, the decrease in the glass transition temperature may become unfilled. On the other hand, if the amount of ZnLi is more than 30%, the viscosity at the liquidus temperature may be lowered. In the present glass, the amount of ZnLi is preferably 20.3% or more, more preferably the amount of ZnLi is 20.5% or more, and particularly preferably, the amount of ZnLi is 21% or more. On the other hand, it is preferred that the amount of ZnLi is 28% or less, more preferably the amount of ZnLi is 27% or less, and particularly preferably, the amount of ZnLi is 26% or less. In the present glass, ZrOj^, which stabilizes the glass, raises the refractive index nd, and suppresses the devitrification component in the formation of the glass preform, is an essential component. In the present glass, the ZrO 2 content is 0.1 to 5%. When the ZrO 2 content exceeds 5%, the forming temperature becomes too high and the Abbe number vd becomes too small. It is preferred that the 21*02 content is 4.5% or less, and more preferably the 21*02 content is 4% or less. Particularly preferably, the ZrO 2 content is 3.5% or less. On the other hand, in order to obtain the effect of addition, it is preferred that the ZrO 2 content is 0.2% or more, and more preferably the ZrO 2 content is 0.3% or more. For the same reason, it is particularly preferable that the Zr〇2 content is 0.4% or more. In the present glass, Ta205 is not an essential component, but stabilizes the glass, increases the refractive index nd, and suppresses the devitrification component in the formation of the glass preform, and may contain 〇~5%. When the content of Ta205 exceeds 5%, the forming temperature becomes too high, and the Abbe number 乂 (5 becomes too small. Further, Ta205 is a component having a higher original price than other components, so when it is added, More preferably, the content is 4% or less, and particularly preferably the content is 3% or less. In the present glass, wo3 is not an essential component, but stabilizes the glass, raises the refractive index nd, and suppresses the glass preform. The component that is devitrified during molding may also contain 0 to 5% of 139318.doc -10- 200948736. If the content of WO exceeds 5%, the forming temperature will become high, and the Abbe number 乂 (1 becomes smaller). It is preferable that the content of w〇3 is 4% or less. w〇3 is also easy to be colored and has a lower transmittance than other components. Therefore, in the case of addition, it is preferred to make the content 3% or less. It is particularly preferable to make the content 2.5% or less.

In the present invention, the glass is not an essential component. However, in order to stabilize the glass, the refractive index nd is increased, and the devitrification of the glass preform during molding is suppressed, and it may be 0 to 5%. If the Nb2〇5 content exceeds 5%, there is an Abbe number... which may become too small or the transmittance may decrease. More preferably, the Nth content is 5% or less. Particularly preferably, the Nb205 content is 4% or less. In the present glass, Y2〇3 and Yb2〇3 are not essential components, but in order to increase the refractive index nd and suppress devitrification during molding of the glass preform, 〇20 may be contained. /◦. However, if the content exceeds 2% by weight, the glass may become unstable and the molding temperature may become too high. More preferably, the content of Ys〇3 or Yb2〇3 is 19% or less, and particularly preferably, the content of γ2〇3 or Yt>2〇3 is respectively less than 18.8%. In the present invention, Al2〇3 is not an essential component, but it may contain 〇~5% for the purpose of stabilizing the glass, adjusting the refractive index, and the like. If the content of Al2〇3 exceeds 5%, the Abbe number... will become too low. More preferably, the content of 乂2〇3 is 4% or less, and particularly preferably the content of octagonal 〇3 is 3% or less. In the present glass, 〇 2% 讥 2 〇 3 may also be contained for purposes such as clarification. The human broken glass substantially contains the above-mentioned components, and if the total content of the essential component and the optional component is 95% or more, the balance of each characteristic is good, and it is more preferable if the total content of 139318.doc 200948736 is 96% or more. If the above total content is 97. / 〇 is especially good. Further, other components may be contained in accordance with the respective characteristics without departing from the object of the present invention. When the other components are contained, the total content of the components is preferably 5% or less. In addition to the above-mentioned components, for example, in order to make the glass more stable, adjust the refractive index nd, adjust the specific gravity, and lower the melting temperature, it is also possible to contain 〇, 5%, IQ, 〇2〇 or Cs2 in a total amount of 5%~5%. The ingredients of 〇. If

When the total amount of each component of Na2〇, K2〇, Rb2〇 or Cs2〇 exceeds 5%, the glass becomes unstable, the refractive index is lowered, the hardness is decreased, or the chemical durability is lowered. Further, in the case of attaching importance to hardness or chemical durability, it is preferred that each component of NaW, ho, milk 2, or Cs2 is not contained. Similarly, the life j can also contain up to 44% of 811〇2 as much as the horse's refractive index~ and the glass transition point^. Similarly, when the high refractive index is emphasized, it may contain 〇6 to 6% of 丁6". If the content of the scratch exceeds 6%, the glass becomes unstable and the transmittance is remarkably lowered. However, When it is desired to increase the Abbe number by %, it is preferable not to contain (10). In the present glass, it is preferable to reduce the environmental load.

Bl2〇3, Pb〇, T1〇2, F, and As2〇3 are not substantially contained. If it contains gas, it will increase the (four) expansion coefficient, which will adversely affect the extraction and formability. In addition, the components are also easily volatilized, so the composition of the optical glass tends to become uneven. Problems such as reduced durability. In the present glass, it is preferable to prevent the coloring or the like from being contained in 139318.doc 200948736% 〇3, but it is usually inevitably mixed from the raw material. It is preferable to set an amount in the glass. · Two = Next. . As the optical characteristics of the present glass, the refractive index 〜 is %. If the refraction • 帛nd is 1.735 or more, then @ is suitable for miniaturization and thinning of the lens. Therefore, it is preferable that the refractive index is (3) or more. On the other hand, if the refractive index nd of the present glass exceeds 176, the Abbe number is too small and adversely affects the thermal physical property f of Φ, which is not preferable. It is preferred that the refractive index nd is 1.755 or less. The Abbe number Vd of the glass is 48 to 51. When the Abbe number of the present glass is Μ $ or more, it is preferably more suitable for the miniaturization and thinning of the lens, and the Abbe number is 49 or more. The glass transition point of this glass is 58 〇. (: The following. Since the glass transfer point is 5 80 C or less, the press forming temperature can be lowered, and the durability of the protective film formed on the surface of the mold can be improved. It is preferable that the glass transfer point & Ο 575 c or less is More preferably, the glass transition point is 57 〇β (: The following. The liquidus temperature TL of the glass is preferably 丨〇〇〇1 or less. If the liquidus temperature TL exceeds 1000 C, there is a glass preform. When the molding is formed, the molded article becomes easy to devitrify, and the formability of the preform is deteriorated. More preferably, the liquidus temperature Tl ' is 995 C or less, and particularly preferably the liquidus temperature Ti^99〇〇c In the present specification, the liquidus temperature Tl is defined as the maximum temperature at which a crystal solidified material is not formed from the glass melt when a certain temperature is maintained. If it is less than 6 dPa·s, there is a glass preform 139318.doc •13· 200948736 Bubble shape from the bottom of the glass preform—in the case of the formation of the body when the residue is cut at the liquidus temperature When the gas is injected, the gas enters the inside and causes a defect. When the viscosity of the glass exceeds 15 dPa.s, the quality of the glass deteriorates. Therefore, the viscosity of the glass at the liquidus temperature is preferably 6 to 15 dPa*s. The glass is dissolved in a dissolution tank to which a discharge nozzle is attached. After the middle melt, the preform for press molding having a specific mass can be formed by dropping and cooling from the discharge nozzle. The obtained preform is placed in a mold for precision press molding (as a representative structure including the upper mold) The lower mold and the blow mold are heated to a deformable temperature, and then pressed, cooled, and taken out to form an optical element. As an optical element using the glass, it can be used for a digital camera or a digital camera. Various lenses, such as aspherical lenses, for forming a telephone with a camera are attached. [Embodiment] Hereinafter, the present invention will be described by way of examples, but the present invention is not limited thereto. Further, Example 16 is the present case. In the examples, Examples 17 to 19 are comparative examples of the present invention. Example 17 is Example 4 of Patent Document 1. Example 18 is Example 7 of Patent Document 2. Example 19 is Embodiment 7 of Patent Document 3. Further, In the experiments of the inventors, Examples 17 and 18 were devitrified and failed to vitrify, so that the physical properties of the glass could not be measured. As a raw material preparation method, the following raw materials were blended and placed in a cast steel plate at 1100 to 1300 C. The melt was melted for 1 hour to obtain a glass of the composition shown in the table. At this time, the glass was stirred by a mixer for 46 hours for 5 hours to homogenize the molten glass, and the homogenized molten glass was flowed out to be formed into After the plate shape, it was kept at a temperature of Tg + 10 ° C for 4 hours, and then slowly cooled to room temperature at a cooling rate of -60 ° C / h. Further, in the chemical composition of the table, the portion indicated by "-" Indicates that the corresponding ingredients are not included. As a raw material, a special grade reagent manufactured by Kanto Chemical Co., Ltd. is used as boron oxide, aluminum oxide, lithium carbonate, zirconium dioxide, zinc oxide, cerium oxide, sodium carbonate, cesium carbonate, and arsenic oxide. As cerium oxide, cerium oxide, and cerium oxide, a reagent having a purity of 99.9% manufactured by Shin-Etsu Chemical Co., Ltd. was used. As cerium oxide, cerium oxide, tungsten oxide, cerium oxide, and cerium oxide, a reagent having a purity of 99.9% or more manufactured by High Purity Chemical Research Co., Ltd. is used. For the obtained glass, the refractive index nd at a wavelength of 587.6 nm (d line), the refractive index nc at a wavelength of 656·3 nm (C line), and the refractive index at a wavelength of 486.1 nm (F line) were measured. nF, Abbe number vd, glass transition point Tg (unit: °C), deformation point At (unit: °C), liquidus temperature TL (unit: °C), and viscosity of molten glass at liquidus temperature. The assays described above are described below. φ Optical constant (refractive index nd, Abbe's number vd): A sample of a rectangular parallelepiped shape having a side of 20 mm and a thickness of 10 mm was processed using a precision refractometer (manufactured by Kalnew Optics Co., Ltd., trade name: KPR-2). The measurement was carried out. Folding rate • The sample obtained by measuring the slow cooling rate of -60 ° C / h is measured. In addition, the Abbe number" (! is obtained by the calculation formula { (nd-l) / (nF-nc) }. Thermal characteristics (glass transition point Tg): using a thermomechanical analysis device (manufactured by Macscience Corporation, Product name: DILATOMETER 5000) The column sample was processed to a diameter of 5 mm and a length of 20 mm at a temperature of 5 ° C / min. 139318.doc -15- 200948736 column sample. Liquid phase temperature TL: 10 times optical The sample which was processed into a cube shape having a side of J 〇mm was placed in a platinum dish and allowed to stand in an electric furnace set to a fixed temperature for 1 hour, and then taken out, and no precipitation of crystals was observed. The maximum temperature is taken as the liquidus temperature t1. The viscosity measurement under the liquidus temperature t1 is measured according to JIS Z8803 using a coaxial double cylindrical rotary viscometer. The results are shown in Tables 1 to 4. 1] Example 1 Example 2 Case 3 Case 4 Case 5 Case 6 B203 23.3 23.3 24.9 24.7 Bu 24.6 24.3 Si02 6.3 4.7 5.7 5.6 5.6 6.5 La2〇3 h 22.4 22.5 22.3 23.1 20.6 23.1 〇d2〇3 22.4 22.5 22.3 23.0 25.4 23.1 ZnO 22.1 22.1 23.1 22.1 22.0 21.0 ΰ2ο 0.8 0.8 1.0 1.0 1.0 1.2 Zr02 1.6 1.6 0.8 0.4 0.8 0.8 ai2〇3 1.4 - - - ra2〇5 1.1 1.1 - - - La ratio 0.50 0.50 0.50 0.50 0.45 0.50 ZnLi mass 22.9 22.9 24.1 23.1 23.0 22.2 n<i 1.74969 1.75147 1.74098 1.74207 1.74346 1.74138 Vd 49.1 48.9 49.8 50.1 49.8 49.9 T/c 574 568 564 566 565 563 Tl/°C 960 980 980 990 1000 980 Viscosity under Tl/dPa-s 15 9 10 9 8 11 139318.doc 16- 200948736 [Table 2] Example 7 cases 8 cases 9 cases 10 cases 11 cases 12 B203 22.9 22.7 22.4 22.9 23.3 22.2 Si〇2 8.1 7.2 7.2 7.2 6.3 6.2 La2〇3 22.7 22.5 22.7 22.3 23.6 22.2 Gd2〇3 22.7 22.5 22.7 23.2 21.2 22.0 ZnO 21.8 21.6 22.9 22.4 22.1 21.6 U2〇1.0 1.0 1.2 1.1 0.8 0.8 Zr02 0.8 2.5 0.8 0.8 1.6 2.3 AI2O3 - - - - - - Ta2〇5 - - - - 1.1 2.7 La ratio 0.50 0.50 0.50 0.49 0.53 0.50 ZnLi mass 22.8 22.6 24.1 23.5 22.9 22.4 Rid 1.74047 1.74951 1.74459 1.74319 1.74977 1.75942 Vd 49.5 49.2 49.2 49.7 49.3 48.1 Tg/°C 571 570 559 563 571 568 Tl/0C 980 980 990 980 990 990 Stickiness under Tl/dPa*s 14 13 11 13 10 10

[Table 3] Example 13 Example 14 Example 15 Example 16 B2〇3 24.7 20.5 24.5 20.8 Si〇2 6.1 9.5 5.6 9.3 L&2〇3 18.4 21.7 18.0 21.1 Gd2〇3 26.9 22.6 28.2 22.2 ZnO 22.1 24.0 21.9 24.3 Li2o 1.0 0.9 1.0 0.9 Zr02 0.8 0.8 0.8 1.5 Y2O3 - - - - Yb203 - - - - BaO - - - - Na20 - - - - Al2〇3 - - - - Ta205 - - - - W03 - - - - Sb203 - - - - As2 〇3 - - - - La ratio 0.41 0.49 0.39 0.49 ZnLi mass 23.1 24.9 22.9 25.2 tld 1.73893 1.74295 1.74294 1.74296 Vd 49.9 49.2 49.8 49.3 T/c 569 570 570 571 TL/°C 1000 990 1020 980 Viscosity under TL / dPa*s 9 13 6 13 139318.doc •17· 200948736 [Table 4] Example 17 Example 18 Example 19 B2〇3 25.5 29.9 26.0 Si02 2.0 - - La2〇3 10.0 12.0 22.5 Gd2〇3 22.0 20.0 20.6 ZnO 21.5 24.0 5.7 Li20 3.0 0.1 1.9 Zr02 - - 6.8 Y2O3 8.0 - - Yb2〇3 - 10.0 2.0 BaO - - 1.1 Na2〇- 3.0 - AI2O3 3.0 - - Ta205 - - 13.3 W03 7.0 - - Sb203 - 1.0 - As2〇3 - - 0.2 La Ratio of 0.31 0.38 0.52 ZnLi 24.5 24.1 7.6 nd - _ 1.79254 Vd - - 45.2 T/c - - 583 Tl/°C - - 1110 Tack of viscosity / dP The present invention has been described in detail with reference to the specific embodiments thereof, and it is obvious to those skilled in the art that various changes or modifications may be added without departing from the spirit and scope of the invention. The present application is based on the application of the patent application No. 2008-073 691, filed on March 21, 2008, the content of which is hereby incorporated by reference. [Industrial Applicability] The present invention can provide an optical glass suitable for use as an optical component such as a digital camera, in particular, a large-diameter aspherical lens. 139318.doc -18-

Claims (1)

200948736 VII. Application for Patent Park: 1. An optical glass containing the following components as an essential component based on the following oxides and expressed in mass%. B2〇3 : 18-3〇0/〇' si〇 2: 3~120/〇, La203: 15-30% 'Gd2〇3: 20.5-30〇/〇, ZnO: 2〇~30〇/〇, Li2〇: 〇·1~2%, and Zr°2 · 0.1-5% ? The total content of Zn〇 and Li20 is 20-30%, the refractive index (nd) is i·73~1.76, the Abbe number (vd) is 48~51, and the glass transition temperature (Tg) is 58. Below 〇 °C. 2. The optical glass of claim 1 which comprises the following ingredients as an optional component: Al2〇3 : 〇~5%, Υ2〇3 : 〇~20% ' Yb2〇3 : 0-20% ' Sb2〇3 : 0-2% ' Nb^〇5 : 0~5〇/〇. Ta2〇 5 : 〇~5〇/〇, and W〇3: 0~5%, the total content of essential components and optional components is in mass °/. Calculated as 95% or more 0 139318.doc 200948736 3. As explained in the optical break, it does not contain Bi2〇3, PbO, τΐ〇2, F and As203. 4. As requested! The optical glass has a mass ratio of La2〇3/(La2〇3+Gd2〇3) of 0.4 to 0.6. 5. The optical glass of claim 1, wherein the liquidus temperature (τ 〇 is 1 〇〇〇. 〇 below. 6. A preform for press forming, comprising any one of claims 5 to 5 Optical glass. 7. The optical element's fault is obtained by precision press forming of optical glass as required in item m. Months 1 to 5. 139318.doc 200948736 IV. Designated representative figure: (1) The representative representative of this case is: (none) (2) The symbol of the symbol of the representative figure is simple: 5. If there is a chemical formula in this case, please disclose the chemical formula that best shows the characteristics of the invention: (none) 139318.doc