JP2003252647A - Optical glass for mold press - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical glass for mold press, which has a refractive index (nd) of 1.75-1.85 and an Abbe's number (υd) of ≥35, has a high transmittance in a short wavelength range, and has an improved devitrification property. <P>SOLUTION: The optical glass has a composition of, by mass%, B<SB>2</SB>O<SB>3</SB>of 5-25%, La<SB>2</SB>O<SB>3</SB>of 15-35%, ZnO of 10-30%, Ta<SB>2</SB>O<SB>5</SB>of 15.5-25%, Li<SB>2</SB>O of 0-3.5%, Na<SB>2</SB>O of 0-10%, K<SB>2</SB>O of 0-9%, R'<SB>2</SB>O (R' is one kind or more of Li, Na, and K) of 0-10%, SiO<SB>2</SB>of 0-20%, Al<SB>2</SB>O<SB>3</SB>of 0-15%, MgO of 0-10%, CaO of 0-7%, BaO of 0-12%, SrO of 0-5%, RO (R is one kind or more of Mg, Ca, Ba, and Sr) of 0-15%, ZrO<SB>2</SB>or 0-10%, Gd<SB>2</SB>O<SB>3</SB>of 0-20%, Bi<SB>2</SB>O<SB>3</SB>of 0-5%, Sb<SB>2</SB>O<SB>3</SB>of 0-1%, TiO<SB>2</SB>of 0-0.5%, and Nb<SB>2</SB>O<SB>5</SB>of 0-0.3%. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical glass for mold press molding.

[0002]

2. Description of the Related Art Higher refractive index and lower dispersion are required as optical properties of glass used for optical lenses such as optical pickup lenses for various optical disk systems such as CDs, MDs, DVDs, and photographing lenses for video cameras and general cameras. More often than not. For these applications, B ₂ O ₃ —La ₂ O ₃ based glass having a refractive index (nd) of 1.75 to 1.85 and an Abbe's number (νd) of 35 or more has been conventionally used.

As a method for producing an optical pickup lens or a lens for photographing, a molten glass is once molded into an ingot, and a glass material cut into an appropriate size is polished and then mold pressed. A method is known in which a glass material formed by so-called droplet formation by dropping from a tip to form a droplet is polished or mold-pressed without polishing.

[0004]

[Patent Document 1] Japanese Unexamined Patent Publication No. 8-26765

[Patent Document 2] Japanese Patent Application Laid-Open No. 8-26766

[0005]

However, B ₂ O ₃ -La
_{Since 2} O ₃ based glass has a strong devitrification tendency, mass productivity is poor when a molten glass is rapidly cast to produce an ingot. Further, in the droplet forming, molten glass is dropped from the tip of the nozzle, and the forming viscosity of glass capable of forming droplets is 10
^The lower limit is about ^0.8 poise, and if dropped below this viscosity, droplets cannot be formed and fibers are formed. Therefore, it has a high devitrification tendency, that is, 10
B ₂ O ₃ -La ₂ devitrification due to low viscosity below ^0.8 poise
O ₃ type glass was not suitable for droplet formation. B ₂ O _3-
Although the devitrification resistance has been improved by the La ₂ O ₃ —Y ₂ O ₃ system composition, the refractive index is lowered in this system.

B ₂ O ₃ -La ₂ O ₃ type glass generally has a high softening point (Ts) and exceeds 700 ° C. In the mold press molding method, the softening point (T
Since it is heated and molded in the vicinity of s), the press die is heated to a temperature close to Ts. When the Ts of the glass material is high, the temperature of the mold also becomes high, which promotes deterioration such as oxidation of the mold, leading to a decrease in mass productivity. B ₂ O _3- for the purpose of lowering Ts
It has been proposed to add R ′ ₂ O (R ′ is one or more of Na, K and Li) to the La ₂ O ₃ based glass, but R ′ ₂
The devitrification property of containing a large amount of O increases. In addition, there also arises a problem that it is easily fused with the mold.

In recent years, a short wavelength (390 to 440n) laser such as a blue laser has been used as a laser for an optical pickup.
As a result, the lens of m) has come to be used, and it is required to improve the transmittance of a lens even at a short wavelength.

An object of the present invention is to have a refractive index (nd) of 1.7.
It is an object of the present invention to provide an optical glass for mold press molding having an Abbe number (νd) of 5 to 1.85 and 35 or more, high transmittance at a short wavelength, and improved devitrification.

[0009]

The optical glass for mold press molding of the present invention has a refractive index (nd) of 1.75 to 1.
85, Abbe number (νd) is 35 or more, softening point is 700 ° C
The following lead-free optical glass for mold press molding, wherein ΔT = {molding temperature (temperature at 10 ^0.8 poise)
-Liquid phase temperature} of 20 ° C or higher, Japan Optical Glass Industry Standard J
OGIS powder method water resistance weight loss less than 0.10%, powder method acid resistance weight loss less than 0.35%, 40
Internal transmittance (t = 10 mm) at a wavelength of 0 nm is 90.0
% Or more and the basicity of the glass is 11 or less.

The optical glass for mold press molding of the present invention contains B ₂ O ₃ 5 to 25% by mass and La ₂ O ₃ 1 in mass%.
5 to 35%, ZnO 10 to 30%, Ta ₂ O ₅ 15.
_{5~25%, Li 2 O 0~3.5%} , Na 2 O 0~1
_{0%, K 2 O 0~9%} , R '2 O (R' is Li, Na,
1 or more of K) 0-10%, SiO ₂ 0-20%,
Al ₂ O ₃ 0-15%, MgO 0-10%, CaO
0-7%, BaO 0-12%, SrO 0-5%, R
O (R is one or more of Mg, Ca, Ba and Sr) 0 to 15
%, ZrO ₂ 0 to 10%, Gd ₂ O ₃ 0 to 20%, B
i ₂ O ₃ 0 to 5%, Sb ₂ O ₃ 0 to 1%, TiO ₂ 0
0.5%, and having a composition of Nb ₂ O ₅ 0~0.3%.

[0011]

The optical glass for mold press molding of the present invention is
Refractive index (nd) is 1.75 to 1.85, Abbe number (ν
d) is a glass of 35 or more. The softening point is 700 ° C
It is below, and the glass component is hard to volatilize. Also, the working temperature range (ΔT = {molding temperature (temperature at 10 ^0.8 poise) −
Since the liquidus temperature}) is 20 ° C. or higher, devitrification spots and striae, which are problems in the glass material melting and molding processes, do not occur, and mass production by droplet molding is possible. Furthermore, the weight loss by the powder method water resistance according to the Japan Optical Glass Industry Association standard JOGIS is less than 0.10%, and the weight loss by the powder method acid resistance is 0.35.
%, And has high weather resistance. And 400 nm
Has an internal transmittance (t = 10 mm) of 90.0% or more, and short wavelength absorption is small. Furthermore, the basicity is 11
It is below (preferably 9.5 or less), and it is possible to prevent fusion between the glass and the press die during molding by the mold press.

In the present invention, the basicity means (sum of moles of oxygen atoms / field of cation Field Str).
It is defined as the sum of length) × 100. Field Strength (hereinafter referred to as F.S.) in the formula is obtained by the following formula.

F. S. = Z / r ² Z is the ionic valence and r is the ionic radius. The numerical values of Z and r in the present invention are “Chemical Handbook Basic Edition, Revision 2”.
Edition (Published by Maruzen Co., Ltd. in 1975) ". According to the knowledge of the present inventor, the lower the basicity, the more difficult it is to fuse with the mold. The mechanism in which the basicity of glass governs fusion will be described below.

The basicity of glass is an index showing how the electrons of oxygen in the glass are attracted to the cations in the glass. In a glass with a high degree of basicity, the cations in the glass are weak in attracting oxygen electrons. Therefore, when a glass having a high basicity is in contact with a cation (mold component) having a strong tendency to seek electrons, cations easily enter from the mold into the glass as compared with a glass having a low basicity. . When cations, which are mold components, penetrate (diffuse) into the glass, the mold component concentration in the glass phase near the interface increases. As a result, the difference in composition between the glass phase and the mold phase is reduced, so that the affinity between the two is increased and the glass easily wets the mold. It is considered that the glass and the mold are fused by such a mechanism. Therefore, as the basicity becomes lower, it becomes more difficult for mold components to penetrate into the glass,
The glass and mold will not fuse together.

Specifically, the basicity of the glass is 11 or less,
It is considered that fusion will not occur if it is preferably 9.5 or less. If the basicity of the glass exceeds 9.5, the glass tends to be fused with the mold, and if it exceeds 11, the glass and the mold are fused and the surface accuracy of the product is impaired, resulting in a marked deterioration in mass productivity. .

A specific composition system of glass having the above-mentioned characteristics
As B₂O₃-La₂O₃-ZnO-Ta₂O_FiveSystem glass
Is preferred. More specifically, in mass%, B₂O₃  5
~ 25%, La₂O₃  15-35%, ZnO 10-3
0%, Ta₂O_Five  Has a basic composition of 15.5 to 25%
It is preferably made of glass. Generally B₂O₃-La ₂
O₃In order to obtain a high refractive index, La-based glass₂O₃To
It contains a large amount of this glass, and the glass of this system
It is a cause. Therefore, in the glass of the present invention, La₂O₃
Part of Ta₂O_FiveAnd replace it with B₂O₃And Zn
While maintaining a high refractive index by optimizing the amount of O
Have improved devitrification. Also improved devitrification
R'which is a component that lowers the softening point by₂Need O
It is possible to add a quantity.

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

B ₂ O ₃ is a skeleton component of glass and is effective in improving devitrification resistance. It is also a component that increases the Abbe number and can lower the softening point. B ₂ O ₃ also has the effect of lowering the basicity of the glass, and is also effective in preventing fusion between the glass and the mold in mold press molding. Its content is 5 to 25%, preferably 10 to 21.5%, more preferably 10 to 20%. If the content of B ₂ O ₃ exceeds 25%, the amount of volatiles formed by B ₂ O ₃ —R ′ ₂ O at the time of melting the glass increases, which promotes the formation of striae. In addition, volatilization also occurs during molding, which contaminates the mold and greatly shortens the life of the mold. Further, the weather resistance is significantly deteriorated. If it is less than 5%, the devitrification resistance is lowered and the working temperature range cannot be sufficiently secured.

La₂O₃Ensure a sufficient working temperature range
It is a component for reducing the Abbe number.
It has the effect of increasing the refractive index. Further suppress the rise in softening point
It also has the effect of improving weather resistance. However, high yield
When added in a large amount to obtain the folding ratio, devitrification was increased.
So Ta₂O_FiveIt is necessary to replace a part of it by
La₂O₃Content of 15-35%, preferably 15-2
It is 9.5%. La ₂O₃Devitrification is
Workability is significantly reduced due to higher temperature and higher liquidus temperature.
Down. If it is less than 15%, the refractive index will decrease and
Symptoms worsen.

ZnO enhances the refractive index, and at the same time B ₂ O ₃
An effect of suppressing high devitrification of -la ₂ O ₃ based glass. Its content is 10 to 30%, preferably 15 to 25
%. If ZnO exceeds 30%, the phase separation tendency of the glass becomes strong, and it becomes difficult to obtain a homogeneous glass. If it is less than 10%, the refractive index is lowered, and the devitrification suppressing effect cannot be obtained.
The liquidus temperature rises, making it impossible to secure a sufficient working temperature range.

Ta ₂ O ₅ has the effect of increasing the refractive index without lowering the Abbe number. Therefore, the devitrification resistance can be improved by substituting with La ₂ O ₃ . Further, by adding an appropriate amount, it is effective in suppressing the phase separation that tends to occur in the B ₂ O ₃ —La ₂ O ₃ —ZnO glass. Further, since the absorption in the ultraviolet region is small, the transmittance hardly decreases even if it is contained in a large amount, and there is no problem even when it is used for a lens for a short wavelength laser. Its content is 15.5-25
%, Particularly preferably 15.5 to 20%. Ta
_{When 2} O ₅ exceeds 25%, devitrification becomes high and the working temperature range becomes narrow. If it is less than 15.5%, the phase separation tendency of the glass becomes strong as the refractive index decreases, making it difficult to obtain a homogeneous glass.

The glass of the present invention, in order to lower the softening point, R _'2 O (R' is Li, Na, one or more of K) may be contained. In the present invention, La ₂ O ₃
The devitrification is improved by substituting a part of Ta ₂ O ₃ for the devitrification, so that even if a large amount of R ′ ₂ O is contained, the devitrification is difficult.

[0023] R _'2 O is a component for lowering the softening point, the total amount 0 to 15 percent, preferably 0 to 10
%, And more preferably 0.1 to 5%. R _'2 O is more than the liquidus temperature rises and the working temperature range narrows significantly for 15%, an adverse effect on productivity. Further, the weather resistance is significantly deteriorated.

Among R ′ ₂ O, Li ₂ O is most effective in lowering the softening point. Its content is 0-3.5%,
It is preferably 0 to 3%, more preferably 0.1 to 3%. However, Li ₂ O has a high devitrification property, and its liquidus temperature tends to be high, which tends to deteriorate workability. S. Is low, the basicity of the glass is increased, and fusion with the mold is caused during press molding, so it is limited to 3.5% or less.

Na ₂ O and K ₂ O have the effect of lowering the softening point, but if contained in a large amount, the volatiles formed by B ₂ O ₃ -R ' ₂ O during melting will increase, and striae will be formed. Promotes. In addition, volatilization also occurs during molding, which contaminates the mold and greatly shortens the life of the mold. Therefore, Na
The content of ₂ O is limited to 0 to 10%, preferably 0 to 5%. Similarly, the content of K ₂ O is limited to 0-9%, preferably 0-5%.

Further, the glass of the present invention comprises SiO ₂ , Al ₂
O ₃ , MgO, CaO, BaO, SrO, ZrO ₂ , Gd
Can include _{2 O 3, Bi 2 O 3} , Sb 2 O 3, TiO 2, Nb 2 O 5 or the like.

The above components will be described in detail below.

SiO ₂ is a component constituting the skeleton of glass, and has the effect of improving devitrification resistance and expanding the working range. It also has the effect of improving weather resistance. Its content is 0 to 10%, preferably 0.5 to 8%. SiO ₂
Is more than 10%, the refractive index may be remarkably lowered or the softening point may exceed 700 ° C.

Al ₂ O ₃ is a component that constitutes the glass skeleton together with SiO ₂ , and has the effect of improving weather resistance.
Its content is 0-15%, especially 0-10%, and even 0
It is preferably ˜5%. Al ₂ O ₃ tends to increase the devitrification tendency, but if it is 15% or less, it is difficult to devitrify, and since the meltability does not deteriorate, striae and bubbles do not remain in the glass and the glass for lenses is used. Can meet the required quality.

RO (R is Mg, Ca, Ba, Sr) acts as a flux and B ₂ O ₃ --La ₂ O ₃ --ZnO
In -ta ₂ O ₅ based glass, an effect of increasing the refractive index without lowering the Abbe number. The total amount is 0 to 15%, preferably 0 to 10%. If the total amount of RO exceeds 15%, devitrification lumps are likely to precipitate during the melting and forming steps of the preformed glass, the liquidus temperature rises, the working temperature range narrows, and mass production becomes difficult. Further, the elution from the glass into the polishing cleaning water and various cleaning solutions becomes severe, and the glass surface is remarkably deteriorated in a high temperature and high humidity state, so that the weather resistance is significantly deteriorated.

MgO is a component for increasing the refractive index, but since it strengthens the phase separation tendency of the glass, its content is preferably limited to 10% or less, particularly 5% or less.

CaO is a component for increasing the refractive index, but M
As with gO, in order to strengthen the phase separation tendency of the glass, its content is preferably limited to 7% or less, particularly 6% or less, and further 5% or less.

BaO is a component that raises the refractive index, and in this glass system, it also has the effect of lowering the liquidus temperature and improving workability. However, in the high temperature and high humidity state, the amount of precipitation from the glass surface is significantly larger than that of other RO components,
If contained in a large amount, the weather resistance of the final product will be significantly impaired. Therefore, its content is 0-12%, especially 0-
It is preferably 11%, more preferably 0 to 10%.

SrO is a component for increasing the refractive index, and has an effect of lowering the liquidus temperature as compared with other RO components, so that the working temperature range can be widened. Further, compared to BaO, the degree of precipitation from the glass surface in a high temperature and high humidity state is small, and a product having excellent weather resistance can be obtained. However, S
Similar to MgO and CaO, if rO is contained in a large amount, the phase separation tendency of the glass becomes strong and it becomes difficult to obtain a homogeneous glass. The content of SrO is preferably 0 to 5%, particularly preferably 0 to 4.5%.

ZrO ₂ is a component which increases the refractive index and improves the weather resistance. Further, since glass is formed as an intermediate oxide, it also has an effect of improving devitrification resistance. However, Zr
When the content of O ₂ increases, the softening point rises and the press formability deteriorates. The content of ZrO ₂ is 0 to 10%, preferably 0 to 9.5%, more preferably 0.1 to 9%.

Gd ₂ O ₃ is a component that increases the refractive index and improves the weather resistance. Further, like ZrO ₂ , it is a component that has the effect of improving devitrification resistance and can extend the working temperature range, but if it is contained in a large amount, the phase separation tendency of the glass becomes strong, and it is difficult to obtain a homogeneous glass. Become. The content of Gd ₂ O ₃ is 0 to 20%, preferably 5 to 15%.

Bi ₂ O ₃ is a component that raises the refractive index and is effective in preventing fusion between the glass and the mold in mold press molding, but since it tends to be colored by heating during molding, its content is high. The amount is preferably 5% or less, particularly 3% or less.

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

TiO ₂ is used as a component for adjusting the optical constants from 0 to
0.5% can be contained. When TiO ₂ exceeds 0.5%, the Abbe number is lowered, devitrification is increased, the liquidus temperature is raised, and the workability is lowered. Further, since the absorption in the ultraviolet region is large, the transmittance at 390 nm to 440 nm is reduced, which hinders its use as a short-wavelength lens. Therefore, in the present invention, it is desirable that the content is not included as much as possible.

Nb ₂ O ₅ is 0 to 0 as a component for adjusting the optical constant.
The content can be 0.3%, preferably 0 to 0.2%. When Nb ₂ O ₅ exceeds 0.3%, the devitrification becomes high, the liquidus temperature rises, and the workability deteriorates remarkably. Also, like TiO ₂ , it has a large absorption in the ultraviolet region, and has a 0.3%
If it exceeds, the transmittance at short wavelengths decreases. Therefore, in the present invention, like TiO ₂ , it is desirable not to contain it as much as possible.

In addition to the above, other components such as WO ₃ and P ₂ O ₅ may be added within the range not impairing the features of the present invention.

Since WO ₃ forms glass as an intermediate oxide, it has an effect of improving devitrification resistance and is also a component for increasing the refractive index. Its content is 0 to 10%, preferably 0 to 8%, more preferably 0.1 to 5%.

P ₂ O ₅ is effective in preventing fusion between the glass and the mold and lowering the liquidus temperature in mold press molding, but the tendency of the glass to phase-separate becomes stronger and the water resistance tends to lower. Therefore, it is desirable to limit the content to 5% or less, particularly 3% or less.

Since PbO and As ₂ O ₃ are environmentally unfavorable, and Ag and halogens serve as photoreversible color change carriers, they should not be used in the present invention. When Y ₂ O ₃ is added, the devitrification becomes high, the liquidus temperature rises, and the workability deteriorates. If TeO ₂ is contained in a large amount, the tendency to absorb short-wavelength light such as a blue laser becomes strong and the transmittance decreases, so the content is preferably limited to 5% or less. Lu ₂ O ₃ strengthens the devitrification tendency of glass, like Y ₂ O ₃ . Moreover, since it is extremely expensive, it is not suitable for industrial use. Therefore, it should not be included in the present invention.

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

First, a glass raw material prepared so as to have a desired composition is melted to obtain a molten glass. Next, molten glass is dripped from the tip of the nozzle and shaped into a droplet (droplet shaping) to obtain a glass material. Further, the molded glass material is polished or mold-pressed without polishing to obtain a lens having a predetermined shape.

It is also possible to adopt a method of molding molten glass into an ingot, polishing a glass material cut into an appropriate size from this, and then performing mold pressing, instead of performing droplet molding.

[0048]

EXAMPLES The present invention will be described below based on examples.

Tables 1 to 3 show examples of the present invention (Sample No. 1).
13 to 13), and Table 4 shows comparative examples (Sample Nos. 14 and 15), respectively.

[0050]

[Table 1]

[0051]

[Table 2]

[0052]

[Table 3]

[0053]

[Table 4]

Each sample was prepared as follows. First, glass raw materials were prepared so as to have the composition shown in the table, and melted at 1400 ° 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 prepared.

With respect to the obtained sample, the refractive index (nd),
Abbe number (νd), softening point (T _S ), molding temperature (T _W ),
Liquidus temperature (T _L ), working temperature range (ΔT), water resistance and acid resistance, internal transmittance at wavelength 400 nm (t = 10 m)
m) was measured. The basicity was also calculated. The results are shown in each table.

As is apparent from the table, No. 1 which is an example of the present invention is used. Each of the samples 1 to 13 has a refractive index of 1.7755.
~ 1.8315, Abbe number 41.3 or more, softening point 6
It is 67 ° C or lower. Further, the working temperature range is 21 ° C. or higher, and the workability is excellent. Moreover, the water resistance has a weight loss of 0.
08% or less, acid resistance is 0.20% or less weight loss,
Good weather resistance. Internal transmittance (t
= 10 mm) is 91% or more, which is excellent in transmitting light of short wavelength. Further, since the basicity is 10.97 or less, it is considered that fusion with the mold is unlikely to occur.

On the other hand, in Comparative Example No. 14, 1
No. 5 could not secure the working temperature range.

The refractive index (nd) is a value measured with respect to the d line (587.6 nm) of a helium lamp.

For the Abbe number (νd), the values of the refractive index of the d line and the F line (486.1 nm) of the hydrogen lamp and the C line (656.3 nm) of the hydrogen lamp are used, and the Abbe number ( νd) = [(nd-1) / (nF-nC)] formula.

The softening point T _S is based on Japanese Industrial Standard R-3104.
It was measured by the fiber elongation method based on.

The working temperature range ΔT was determined as follows.
First, the molding temperature T _W was measured by the platinum ball pulling method, and 10
^It was determined as a temperature corresponding to ^0.8 poise. The liquid phase temperature T _L is 297 to 500 μm, and the sample is crushed and classified so that the sample is put in a platinum boat, kept in an electric furnace having a temperature gradient for 24 hours, and then left to cool in air. It was measured by determining the position of devitrification precipitation with an optical microscope. The difference between the molding temperature _TW and the liquidus temperature _TL thus obtained was defined as the working temperature range ΔT.

The water resistance and the acid resistance of the glass sample are 420 according to the Japan Optical Glass Industry Association Standard 06-1975.
Crushed to ˜590 μm, weighed the specific gravity of the gram, put it in a platinum basket, put it in a flask containing the reagent and treat it in a boiling water bath for 60 minutes to reduce the mass reduction (wt%) of the powder glass after treatment. It is calculated. The reagent used for water resistance evaluation was pure water adjusted to pH 6.5 to 7.5,
The reagent used for the acid resistance evaluation is a nitric acid aqueous solution adjusted to 0.01N.

The transmittance of glass is shown as an internal transmittance that does not include reflection loss. Internal transmittance is thickness t = 3m
It was calculated from the transmittance including reflection loss of m and 10 mm samples using the following formula.

Internal transmittance = EXP [(lnT _{3 mm} −lnT _{10 mm} ) / Δt × L] T _{3 mm} : transmittance of a sample of t = 3 mm (including reflection loss) T _{10 mm} : transmittance of a sample of t = 10 mm ( (Including reflection loss) Δt: thickness difference (mm) of sample L: 10 mm

The measurement was carried out using a glass sample of 30 × 30 × 3 mm.
And 30 × 30 × 10 mm were processed into two types of thickness, and the incident surface and the outgoing surface of the transmitted light beam were mirror-polished.

The basicity is (sum of oxygen atom moles / total
The sum of the cation Field Strength) × 1
It is calculated based on the formula of 00. Note that F in the formula
The field strength (hereinafter referred to as FS) is calculated by the following equation.

F. S. = Z / r ² Z is the ionic valence and r is the ionic radius. The numerical values of Z and r in the present invention are “Chemical Handbook Basic Edition, Revision 2”.
Edition (Published by Maruzen Co., Ltd. in 1975) ".

[0068]

As described above, the optical glass of the present invention is used as an optical lens such as an optical pickup lens for various optical disk systems such as CDs, MDs, DVDs, and a photographing lens for video cameras and general cameras. 1.75
~ 1.85 refractive index (nd), 35 or more Abbe number (ν
d). In addition, since the softening point is low and the glass component is hard to volatilize, the molding accuracy is not deteriorated and the mold is not deteriorated or contaminated. In addition, since the working temperature range is wide, the preform glass is excellent in mass productivity, and the weather resistance is good, physical properties are not deteriorated and surface deterioration is not caused during the manufacturing process or use of the product. In addition, since it has little absorption in the ultraviolet region, it has excellent short-wavelength transmittance. Further, since the basicity is low, there is no fusion with the mold during pressing, and mass productivity is very good. Therefore, it is suitable as an optical glass for mold press molding.

Continued front page    F-term (reference) 4G062 AA04 BB08 DA01 DA02 DA03                       DB01 DB02 DB03 DB04 DC03                       DC04 DD01 DE04 DF01 EA01                       EB01 EC01 ED01 ED02 ED03                       ED04 EE01 EE02 EE03 EE04                       EF01 EF02 EF03 EF04 EG01                       EG02 EG03 EG04 FA01 FB01                       FB02 FC01 FC02 FC03 FD01                       FE01 FF01 FG01 FG02 FH04                       FH05 FJ01 FK04 FK05 FL01                       GA01 GA02 GA03 GB01 GC01                       GD01 GE01 HH01 HH03 HH05                       HH07 HH09 HH11 HH13 HH15                       HH17 JJ01 JJ03 JJ04 JJ05                       JJ07 KK01 KK03 KK04 KK05                       KK07 MM02 NN02 NN03 NN29                       NN32 NN34

Claims (9)

[Claims] 1. A refractive index (nd) of 1.75 to 1.85,
An optical glass for mold press molding having an Abbe number (νd) of 35 or more and a softening point of 700 ° C. or less, wherein ΔT = {molding temperature (temperature at 10 ^0.8 poise) −liquidus temperature} 20 ° C or higher, Japan Optical Glass Industry Association standard JOG
Weight loss by powder method water resistance by IS is less than 0.10%,
Weight loss with acid resistance of the powder method is less than 0.35%, 400n
An optical glass for mold press molding, which has an internal transmittance (t = 10 mm) at a wavelength of m of 90.0% or more and a basicity of glass of 11 or less. 2. The optical glass for mold press molding according to claim 1, which is made of B ₂ O ₃ —La ₂ O ₃ —ZnO—Ta ₂ O ₅ based glass. 3. By mass%, B ₂ O ₃ 5 to 25%, La _{2
O 3 15~35%, 10~30% ZnO} , Ta 2 O 5
The optical glass for mold press molding according to claim 2, which has a composition of 15.5 to 25%. 4. The optical glass for mold press molding according to claim 3, further comprising R ′ ₂ O (R ′ is L in mass%).
Optical glass for mold press molding, which has a composition of 0 to 10%. 5. The optical glass for mold press molding according to claim 3, further comprising Li ₂ O 0 to 3.5 in mass%.
%, Na ₂ O 0 to 10%, K ₂ O 0 to 9%, and an optical glass for mold press molding. 6. The optical glass for mold press molding according to claim 3, further comprising SiO ₂ 0 to 10 in mass%.
%, Al ₂ O ₃ 0 to 15%, MgO 0 to 10%, Ca
O 0 to 7%, BaO 0 to 12%, SrO 0 to 5
%, ZrO ₂ 0 to 10%, Gd ₂ O ₃ 0 to 20%, Bi _{2
O 3 0~5%, Sb 2 O} 3 0~1% of the mold for press molding an optical glass characterized by having a composition. 7. The optical glass for mold press molding according to claim 3, further comprising RO (R is Mg, C) in mass%.
a, Ba, Sr one or more) Optical glass for mold press molding, which has a composition of 0 to 15%. 8. The optical glass for mold press molding according to claim 3, further comprising TiO ₂ 0 to 0.
_{5%, Nb 2 O 5 0~0.3} % of mold press molding an optical glass characterized by having a composition. 9. By mass%, B ₂ O ₃ 5 to 25%, La _{2
O 3 15~35%, 10~30% ZnO} , Ta 2 O 5
_{15.5~25%, Li 2 O 0~3.5%} , Na 2 O
_{0~10%, K 2 O 0~9%} , R '2 O (R' is L
i, Na, one or more of K) 0 to 10%, SiO ₂ 0
_{~20%, Al 2 O 3 0~15} %, MgO 0~10
%, CaO 0-7%, BaO 0-12%, SrO
0-5%, RO (R is one or more of Mg, Ca, Ba, Sr) 0-15%, ZrO ₂ 0-10%, Gd ₂ O ₃
0-20%, Bi ₂ O ₃ 0-5%, Sb ₂ O ₃ 0-1
%, TiO ₂ 0 to 0.5%, Nb ₂ O ₅ 0 to 0.3%
An optical glass for mold press molding, which has the composition of