JP2007169086A - Optical glass for mold press forming - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide optical glass for mold press forming, which satisfies characteristics to be requested as the optical glass for mold press forming and has, in particular, 1.585-1.595 refractive index (nd) and ≥59 Abbe number (υd) and is excellent in weather resistance and in which lead and fluorides are not contained. <P>SOLUTION: The optical glass for mold press forming consists of the glass expressed by SiO<SB>2</SB>-B<SB>2</SB>O<SB>3</SB>-R"<SB>2</SB>O<SB>3</SB>-RO (wherein R" is one or more elements selected from La and Gd; and R is one or more elements selected from Mg, Ca, Sr and Ba) containing 39-60 mass% SiO<SB>2</SB>, 19-35 mass% B<SB>2</SB>O<SB>3</SB>, 59-75 mass% (SiO<SB>2</SB>+B<SB>2</SB>O<SB>3</SB>), 0.1-25 mass% R"<SB>2</SB>O<SB>3</SB>, 1.5-4.8 mass% Al<SB>2</SB>O<SB>3</SB>, 12-23 mass% RO and 15-27 mass% (RO+R"<SB>2</SB>O<SB>3</SB>). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical glass for mold press molding.

Refractive index (nd) is 1.585 to 1.595, Abbe number (νd) for optical lenses such as optical pickup lenses for CD, MD, DVD, and other various optical disk systems, video cameras and photographing lenses for general cameras. ) Of 59 or more is used. Conventionally, lead glass and glass containing fluoride based on SiO ₂ —PbO—R ′ ₂ O (R ′ ₂ O is an alkali metal oxide) have been widely used as such glass. In view of environmental problems, non-lead glass such as SiO ₂ —B ₂ O ₃ —RO (RO is an alkaline earth metal oxide) —R ′ ₂ O glass is being switched. (For example, see Patent Documents 1 to 3)
JP-A-6-107425 JP 2000-302479 A JP 2002-249341 A

  These optical pickup lenses and photographing lenses are manufactured as follows.

  First, molten glass is dropped from the tip of a nozzle to once produce a droplet glass, which is then ground, polished and washed to obtain a preform glass. Alternatively, a molten glass is quenched and cast to produce a glass block, which is then ground, polished and washed to obtain a preform glass. Next, the preform glass is heated until it is in a softened state in a precision-processed mold, and pressure-molded to transfer the surface shape of the mold to the glass. This molding method is called a mold press molding method and is widely used. In this way, an optical pickup lens and a photographing lens are manufactured.

  Therefore, the optical glass for mold press molding not only satisfies the required optical constants (refractive index, Abbe number), but also has a low softening point so as not to deteriorate the mold, Therefore, it is required that the material is not easily fused and has high weather resistance.

  However, conventional lead-free glass as shown in the patent literature does not have sufficient weather resistance. Therefore, the surface of the glass is altered by elution of the glass components in the glass cutting, polishing, and cleaning processes into the polishing and cleaning water and various cleaning solutions. There arises a problem that the quality deteriorates and the reliability is impaired.

  In particular, none of the glasses having a refractive index (nd) of 1.585 to 1.595 and an Abbe number (νd) of 59 or more has good weather resistance.

  The object of the present invention is to satisfy the properties required for optical glass for mold press molding, and in particular, the refractive index (nd) is 1.585 to 1.595, the Abbe number (νd) is 59 or more, and the weather resistance Furthermore, the present invention provides an optical glass for mold press molding which is excellent in the above and does not contain lead and fluoride.

The optical glass for mold press molding of the present invention is SiO ₂ —B ₂ O ₃ —R ″ ₂ O ₃ (R ″ is one or more of La and Gd) —RO (R is one or more of Mg, Ca, Sr and Ba). ) Based glass, SiO ₂ 39-60%, B ₂ O ₃ 19-35%, SiO ₂ + B ₂ O ₃ 59-75%, R " ₂ O ₃ 0.1-25%, Al ₂ O ₃ 1.5 to 4.8%, RO 12 to 23%, RO + R ″ ₂ O ₃ 15 to 27%.

  The optical glass for mold press molding of the present invention is used for optical lenses such as optical pickup lenses for CD, MD, DVD, and other various optical disk systems, and photographing lenses for video cameras and general cameras. It has a refractive index (nd) of 595 and an Abbe number (νd) of 59 or more. In addition, since the weather resistance is good, the physical properties are not deteriorated or the surface is not deteriorated during the production process or use of the product. In addition, since the softening point is low and the glass component is difficult to volatilize, the molding accuracy is not lowered and the mold is not deteriorated or contaminated. Therefore, it is suitable as an optical glass for mold press molding.

The optical glass for mold press molding of the present invention is SiO ₂ —B ₂ O ₃ —R ″ ₂ O ₃ (R ″ is one or more of La and Gd) —RO (R is one or more of Mg, Ca, Sr and Ba). ) A glass having a basic composition and containing no lead and fluoride. More _{specifically, SiO 2 39~60%, B 2} O 3 19~35%, SiO 2 + B 2 O 3 59~75%, R "2 O 3 0.1~25%, Al 2 O 3 1 0.5 to 4.8%, RO 12 to 23% (R is one or more of Mg, Ca, Sr and Ba), and RO + R " ₂ O ₃ 15 to 27%. In general, lead-free glass contains a large amount of RO, which is an alkaline earth metal oxide, in order to obtain a high refractive index, which causes a decrease in the weather resistance of this glass. Therefore, the glass of the present invention contains R " ₂ O ₃ that is a component that increases the refractive index and Al ₂ O ₃ that is a component that improves weather resistance, and suppresses the content of RO, thereby reducing the refractive index. While maintaining, the weather resistance of the glass is improved. Also, when R " ₂ O ₃ is contained, the Abbe number tends to decrease, but by containing B ₂ O ₃ , the Abbe number is decreased. Is preventing.

  By doing so, an optical glass for mold press molding having excellent weather resistance, a refractive index (nd) of 1.585 to 1.595, and an Abbe number (νd) of 59 or more can be obtained. It can be used as an optical lens for small optical elements with little dispersion and high functionality.

  When the refractive index (nd) is lower than 1.585, it is necessary to enlarge the optical lens, which makes it difficult to use as an optical lens for a small optical element. On the other hand, if it is higher than 1.595, it becomes difficult to adjust the optical axis. On the other hand, when the Abbe number is smaller than 59, the chromatic dispersion of the optical lens increases, making it difficult to use the optical lens.

  Moreover, the optical glass for mold press molding of the present invention preferably has a glass softening point of 650 ° C. or lower (preferably 640 ° C. or lower, more preferably 630 ° C. or lower). When the softening point of the glass is lowered, press molding at a low temperature becomes possible, and mold oxidation and mold contamination due to volatilization of glass components and fusion between the glass and the mold can be suppressed.

  Furthermore, in order to more effectively prevent the fusion between the glass and the mold at the time of mold press molding, in addition to the above characteristics, the basicity of the glass should be 11 or less (preferably 9.5 or less). desirable.

  In the present invention, the basicity is defined as (total number of moles of oxygen atoms / total number of cation field strength) × 100, and Field Strength (hereinafter referred to as FS) is expressed by the following formula: Is required.

F. S. = Z / r ²
Z represents an ionic valence, and r represents an ionic radius. The values of Z and r in the present invention are the values in Table 1 (values described in “Science Manual Basic Bias Revised 2nd Edition (1975 Maruzen Co., Ltd.)”). According to the knowledge of the present inventor, the lower the basicity, the harder it is to fuse with the mold. The mechanism by which the basicity of the glass controls the fusion will be described below.

Here, taking SiO ₂ as an example, how to determine the basicity of the glass will be described.

First, the number of moles of oxygen atoms is obtained. In 1 mol of SiO ₂ , 2 mol of oxygen atoms are contained. Therefore, the number of moles of oxygen atoms possessed by SiO ₂ in the glass can be obtained by multiplying the number of moles of oxygen by ₂ mol by the mole percentage of SiO ₂ in the glass composition. Similarly, the number of moles of oxygen atoms of each component is obtained, and the sum is defined as “total number of moles of oxygen atoms”.

Next, F. S. Ask for. Since the cation Si ⁴⁺ is Z = 4 and r = 0.4, F.I. S. = 25. Since 1 mol of Si ⁴⁺ is contained in SiO ₂ , F. S. Is calculated as 25 × 1 (mol) × (mol% of SiO _{2 in} the composition).

  This is calculated | required about each component and let the sum total be "the sum total of FS of a cation."

  Then, the value obtained by multiplying the value obtained by dividing the “total number of moles of oxygen atoms” by the “total number of FS of cation” by 100 is defined as “basicity of glass”.

  Next, a mechanism in which the basicity of the glass controls the fusion will be described.

  The basicity of the glass is an index indicating how much oxygen electrons in the glass are attracted to the cations in the glass. In a glass having a high basicity, the attraction of oxygen electrons by cations in the glass is weak. Therefore, when a glass having a high basicity is in contact with a cation (mold component) that has a strong tendency to demand electrons, a cation from the mold is more likely to enter the glass than a glass having a low basicity. . When the cation which is a mold component penetrates (diffuses) into the glass, the mold component concentration in the glass phase near the interface increases. Thereby, since the difference in composition between the glass phase and the mold phase is reduced, the affinity between the two is increased, and the glass is easily wetted by the mold. It is considered that the glass and the mold are fused by such a mechanism. Therefore, as the basicity is lowered, the mold components are less likely to enter the glass, and the glass and the mold are not fused.

  Specifically, if the basicity of the glass is 11 or less, preferably 9.5 or less, it is considered that fusion does not occur. If the basicity of the glass exceeds 9.5, a tendency to fuse with the mold appears, and if it exceeds 11, the glass and the mold are fused to deteriorate the surface accuracy of the product, and the mass productivity is remarkably deteriorated. There is a tendency.

  The reason why the range of each component is limited as described above is as follows.

SiO ₂ is a component constituting the skeleton of the glass and has an effect of improving weather resistance. When the content is more than 60%, the refractive index tends to be remarkably lowered and the softening point tends to be high. In addition, the meltability deteriorates and striae and bubbles remain in the glass, so that the required quality as lens glass is not satisfied. On the other hand, if it is less than 39%, the weather resistance tends to deteriorate. The preferred range of SiO ₂ is 40 to 55%, more preferably 41 to 48%.

B ₂ O ₃ is a skeletal component of glass and is effective in improving devitrification resistance. In addition, it is a component that increases the Abbe number or decreases the softening point. It also has the effect of reducing the basicity of the glass, and is effective in preventing the fusion between the glass and the mold in mold press molding. When the content exceeds 35%, the chemical durability of the glass is lowered and the weather resistance is remarkably deteriorated. On the other hand, if it is less than 19%, the devitrification resistance is lowered, and the working temperature range cannot be sufficiently secured. Moreover, it becomes difficult to obtain a desired Abbe number. A preferable range of B ₂ O ₃ is 19 to 29%, more preferably 19 to 25%.

Further, in order to obtain a desired refractive index and Abbe number without deteriorating the devitrification resistance, weather resistance, and meltability of the glass, the total amount of SiO ₂ and B ₂ O ₃ needs to be 59 to 75%. There is. When the total amount exceeds 75%, the refractive index decreases. Moreover, there exists a possibility that devitrification resistance and a meltability may deteriorate. On the other hand, if it is less than 59%, the Abbe number and weather resistance may be lowered. The preferable range of SiO ₂ + B ₂ O ₃ is 59 to 72%, more preferably 59 to 68%.

R " ₂ O ₃ (R" is one or more of La and Gd) is a component that increases the refractive index in SiO ₂ -B ₂ O ₃ -R " ₂ O ₃ -RO-based glass. This eliminates the need for inclusion, and is effective in improving weather resistance. R " ₂ O ₃ is also effective in improving weather resistance. When R ″ ₂ O ₃ exceeds 25%, the Abbe number tends to be remarkably reduced. On the other hand, when it is less than 0.1%, the weather resistance is lowered and it is difficult to obtain a desired refractive index. The preferable range of ₂ O ₃ is 0.5 to 20%, more preferably 0.5 to 15%.

La ₂ O ₃ is a component having a large effect of increasing the refractive index without reducing the Abbe number among R ″ ₂ O _{3. Further} , La ₂ O ₃ has an effect of suppressing an increase in softening point and improving weather resistance. However, it becomes likely to undergo phase separation and a large amount is added in order to obtain a high refractive index, it is preferable to substitute a part of the Gd ₂ O _3. its content is 0.1 to 20% .la ₂ If O ₃ is more than 20%, phase separation tends to occur and the liquidus temperature tends to be high and workability tends to be deteriorated, while if it is less than 0.1%, the refractive index is lowered and the weather resistance is low. The preferable range of La ₂ O ₃ is 0.5 to 15%, more preferably 4 to 9%.

Gd ₂ O ₃ is a component that increases the refractive index. It also has the effect of improving weather resistance, suppressing devitrification of glass, and extending the working temperature range. However, when the content exceeds 6%, the Abbe number tends to decrease remarkably. The preferable range of Gd ₂ O ₃ is 0 to 4%, more preferably 0 to 3%.

Al ₂ O ₃ is a component constituting the skeleton and has an effect of improving weather resistance. Moreover, the effect which suppresses the selective elution to the water of the alkali component in glass is remarkable. When the content is more than 4.8%, the devitrification resistance is lowered and the working temperature range cannot be sufficiently secured. In addition, the meltability deteriorates and striae and bubbles remain in the glass, so that the required quality as lens glass is not satisfied. On the other hand, when the content is less than 1.5%, the amount of alkali components eluted increases and the weather resistance tends to deteriorate. The preferable range of Al ₂ O ₃ is 1.7 to 4.8%, more preferably 2 to 4.8%.

RO (R is Mg, Ca, Ba, Sr) acts as a flux and increases the refractive index without reducing the Abbe number in SiO ₂ —B ₂ O ₃ —R ″ ₂ O ₃ —RO glass. If RO exceeds 23%, devitrification will easily precipitate during the melting and forming process of the preform glass, the liquidus temperature will rise, the working temperature range will be narrowed, and mass production will be difficult. Elution into the abrasive cleaning water and various cleaning solutions becomes severe, and the surface of the glass changes significantly in high temperature and high humidity conditions, and the weather resistance is significantly deteriorated, whereas if it is less than 12%, the refractive index of the glass decreases. The range of RO is preferably 13 to 22%, more preferably 13 to 20%.

  MgO is a component that increases the refractive index, and also has the effect of lowering the softening point in this glass system. However, when the content is more than 10%, the phase separation property becomes strong, and the liquidus temperature tends to be remarkably high and the workability tends to be deteriorated. The preferable range of MgO is 0 to 5%, more preferably 0 to 3%.

  CaO is a component that increases the refractive index, and also has the effect of lowering the softening point in this glass system. However, when the content exceeds 10%, phase separation is likely to occur, and the liquidus temperature may be increased to deteriorate workability. The preferable range of CaO is 0 to 7%, more preferably 3 to 7%.

  BaO is a component that increases the refractive index, and also has the effect of lowering the liquidus temperature and widening the working temperature range in this glass system. However, if the content exceeds 10%, precipitation from the glass surface in a high-temperature and high-humidity state becomes significantly larger than other RO components, and the weather resistance of the final product is significantly impaired. The preferable range of BaO is 0 to 9%, more preferably 6 to 9%, and particularly preferably 7 to 9%.

  SrO is a component that increases the refractive index. Further, since the amount of precipitation from the glass surface is smaller than that of BaO, a glass having excellent weather resistance can be obtained by positively using SrO. However, if the content exceeds 14%, the liquidus temperature becomes high and the workability tends to deteriorate. The preferable range of SrO is 0.1 to 10%, more preferably 0.1 to 7%.

Further, in order to obtain a desired refractive index and Abbe number, RO and R " ₂ O ₃ must be 15 to 27% in total. When the total amount exceeds 27%, the Abbe number decreases. There is a risk that devitrification deposits may precipitate during the melting and forming process of the preform glass. On the other hand, if it is less than 15%, the refractive index is remarkably lowered. The preferred range of RO + R " ₂ O ₃ is 16 to 27%. More preferably, it is 17 to 26%.

The glass of the present invention can contain R ′ ₂ O (R ′ is one or more of Li, Na and K) in order to lower the softening point. In the present invention, by introducing R " ₂ O ₃ , it becomes possible to suppress the RO content and the weather resistance is improved, so that R ' ₂ O, which is a component that reduces weather resistance, is contained. Also, the weather resistance that can be used practically can be maintained.

R ′ ₂ O is a component for lowering the softening point. When R ′ ₂ O exceeds 14%, the weather resistance is remarkably deteriorated, or R ′ ₂ O is volatilized from the glass at the time of mold press molding, and the glass and the mold are easily fused. In addition, the liquidus temperature is remarkably increased and the working temperature range is narrowed, which adversely affects mass productivity. On the other hand, if it is less than 3%, it is difficult to obtain the effect of lowering the softening point of the glass. The preferable range of R ′ ₂ O is 5 to 14%, more preferably 5 to 9%.

Among R ′ ₂ Os, Li ₂ O has the greatest effect of lowering the softening point. When the content exceeds 9%, volatiles formed by B ₂ O ₃ —R ′ ₂ O at the time of melting increase, and striae easily occur. In addition, volatilization occurs during molding, which contaminates the mold and greatly shortens the life of the mold. Moreover, it is easy to phase-separate and there exists a tendency for liquid phase temperature to become high and to worsen workability | operativity. Further, F.R. S. Is a component that increases the basicity of the glass and causes fusion with the mold during press molding. On the other hand, if it is less than 3%, it is difficult to obtain the effect of lowering the softening point of the glass. Li ₂ O The preferred range is from 4 to 9%, more preferably 5 to 9%.

Na ₂ O is a component that lowers the softening point. When the content exceeds 9%, volatiles formed by B ₂ O ₃ —R ′ ₂ O at the time of melting increase, and striae easily occur. In addition, volatilization occurs during molding, which contaminates the mold and greatly shortens the life of the mold. The preferable range of Na ₂ O is 0 to 7%, more preferably 0 to 3.5%.

K ₂ O is a component that lowers the softening point. When the content exceeds 5%, volatiles formed by B ₂ O ₃ —R ′ ₂ O at the time of melting increase, and striae easily occur. In addition, volatilization occurs during molding, which contaminates the mold and greatly shortens the life of the mold. K ₂ O in the preferred range is 0-4%, more preferably 0 to 2.5%.

  ZnO is a component that increases the refractive index and improves the weather resistance. It also has the effect of suppressing the devitrification of the glass and extending the working temperature range. However, when its content exceeds 10%, the Abbe number tends to decrease. The preferable range of ZnO is 0 to 5%, more preferably 0 to 2%.

Ta ₂ O ₅ is a component that increases the refractive index and improves the weather resistance. It also has the effect of suppressing the devitrification of the glass and extending the working temperature range. However, when the content exceeds 7%, the Abbe number tends to decrease remarkably. The preferable range of Ta ₂ O ₅ is 0 to 5%, more preferably 0 to 3%.

TiO ₂ has the effect of greatly improving chemical durability and improving weather resistance. If the content exceeds 0.2, the Abbe number tends to decrease. The preferred range of TiO ₂ is 0 to 0.1%, more preferably from 0 to 0.05%.

ZrO ₂ has the effect of improving water resistance and improving weather resistance. If the content exceeds 5%, the Abbe number tends to decrease. The preferable range of ZrO ₂ is 0 to 3%, more preferably 0 to 0.5%.

Sb ₂ O ₃ can also be added as a fining agent. In order to avoid excessive coloring to the glass, the content of Sb ₂ O ₃ is 1% or less.

In addition to the above, other components such as P ₂ O ₅ and WO ₃ can be added as long as the characteristics of the present invention are not impaired. P ₂ O ₅ is effective in preventing fusion between glass and a mold and lowering the liquidus temperature in mold press molding, but has a strong phase separation and tends to lower the water resistance. In particular, it is desirable to limit it to 2% or less. WO ₃ has the effect of increasing the refractive index, but if added in a large amount, the Abbe number tends to decrease, so it is desirable to limit it to 5% or less, particularly 2% or less.

In addition, PbO, fluoride and As ₂ O ₃ are used for reasons of adverse effects on the environment and the human body, and Ag and halogens are photoreversible discoloration carriers. Is desirable.

  Next, a method for producing an optical pickup lens, a photographing lens, etc. using the glass of the present invention will be described.

  First, after preparing a glass raw material so that it may become a desired composition, it fuse | melts in a glass melting furnace. Subsequently, the glass melt is formed into preform glass, and then the preform glass is placed in a precision-worked mold and heated until it becomes softened (mold press molding). The surface shape of the mold is transferred to glass. In this way, an optical pickup lens and a photographing lens can be obtained. The preform glass molding method is not particularly limited, but it is preferable to employ a droplet molding method in which molten glass is dropped from the tip of a nozzle to produce droplet glass. The reason is that the glass obtained by the droplet forming method has a spherical shape, so that grinding, polishing, and cleaning steps are almost unnecessary.

  EXAMPLES Hereinafter, the optical glass for mold press molding of this invention is demonstrated in detail based on an Example.

  Tables 2 to 4 show Examples (Sample Nos. 1 to 9) and Comparative Examples (Sample Nos. 10 to 12) of the present invention.

  Each sample was prepared as follows. First, glass raw materials were prepared so as to have the composition shown in the table, and were melted at 1350 ° C. for 3 hours using a platinum crucible. After melting, the melt was poured onto a carbon plate, and after annealing, a sample suitable for each measurement was produced.

  The obtained sample was evaluated for refractive index (nd), Abbe number (νd), weather resistance and softening point (Ts). The basicity was calculated. The results are shown in each table.

  As is apparent from the table, No. 1 as an example of the present invention. Each of the samples 1 to 9 had a refractive index of 1.5850 to 1.5894 and an Abbe number of 59.9 to 62.4. Further, the change in transmittance before and after the exposure test in a high temperature and high humidity state was as small as 1.8% or less, and the weather resistance was also good. Moreover, it has a softening point of 644 ° C. or lower and a basicity of 7.8 or lower, which enables press molding at a low temperature, contamination of the mold due to oxidation of the mold and volatilization of the glass component, and between the glass and the mold. It is thought that fusion can be suppressed.

  On the other hand, No. which is a comparative example. In each of the samples 10 and 12, the change in transmittance before and after the exposure test was as large as 2.5% or more, and the weather resistance was low. Sample No. 11 had an Abbe number as low as 57.5.

  The refractive index (nd) is indicated by the measured value for the d-line (587.6 nm) of the helium lamp.

  The Abbe number (νd) is obtained by using the refractive index of the d-line and the refractive index of the F-line (486.1 nm) of the hydrogen lamp and the C-line (656.3 nm) of the hydrogen lamp. = [(Nd-1) / (nF-nC)].

  The weather resistance was evaluated by measuring the transmittance of the glass before and after the exposure test in a high-temperature and high-humidity state with a spectrophotometer, and evaluating the difference in the transmittance of the glass at a wavelength of 400 nm where the difference is large in the visible wavelength range. When the difference in transmittance was 2% or less, “◯” was assigned, and when the difference was 2% or more, “X” was given. The exposure test was performed under the conditions of a temperature of 60 ° C., a humidity of 90%, and 168 hours, and a glass sample having a size of 30 × 25 mm and optically polished on both sides to a thickness of 5 mm was used.

  The softening point (Ts) was measured by a fiber elongation method based on Japanese Industrial Standard R-3104.

  The basicity is calculated based on the formula: (total number of moles of oxygen atoms / total number of cation field strength) × 100. The field strength (hereinafter referred to as FS) in the formula was determined by the following formula.

F. S. = Z / r ²
Z represents the ionic valence, r represents the ion radius, and the values in Table 1 were used for the numerical values of Z and r.

Claims (8)

SiO ₂ —B ₂ O ₃ —R ″ ₂ O ₃ (R ″ is one or more of La and Gd) —RO (R is one or more of Mg, Ca, Sr and Ba) based glass, _{2 39~60%, B 2 O 3} 19~35%, SiO 2 + B 2 O 3 59~75%, R "2 O 3 0.1~25%, Al 2 O 3 1.5~4.8% , RO 12-23%, RO + R " ₂ O ₃ 15-27% glass for molding press, characterized by containing. By _{mass%, La 2 O 3 0.1~20%} , Gd 2 O 3 0~6% mold press molding an optical glass of claim 1, characterized in that it contains.   The optical glass for mold press molding according to claim 1 or 2, characterized by containing, in mass%, 0 to 10% MgO, 0 to 10% CaO, 0 to 10% BaO, and 0 to 14% SrO. The optical glass for mold press molding according to any one of claims 1 to 3, comprising 3 to 14% by mass of R ' ₂ O (R' is one or more of Li, Na, and K). . By _{mass%, Li 2 O 3~9%,} Na 2 O 0~9%, optical mold press forming according to any one of claims 1 to 4, characterized in that it contains K ₂ O 0 to 5% Glass. % By _{mass, 0~10% ZnO, Ta 2 O} 5 0~7% containing mold press molding an optical glass according to any one of claims 1 to 5, characterized in that. The optical glass for mold press molding according to any one of claims 1 to 6, comprising 0 to 0.2% of TiO _{2 and} 0 to 5% of ZrO _{2 in} mass%.   The optical glass for mold press molding according to any one of claims 1 to 7, which has a softening point of 650 ° C or lower.