CN110204198B

CN110204198B - Phosphate optical glass

Info

Publication number: CN110204198B
Application number: CN201810167230.5A
Authority: CN
Inventors: 王自力; 邓和平
Original assignee: Chengdu Youlite Photoelectric Technology Co ltd
Current assignee: Chengdu Youlite Photoelectric Technology Co ltd
Priority date: 2018-02-28
Filing date: 2018-02-28
Publication date: 2022-04-05
Anticipated expiration: 2038-02-28
Also published as: CN110204198A

Abstract

The invention relates to a phosphate optical glass which is free of TiO₂Phosphate optical glass having a high transmittance, and a preform suitable for precision press molding and a production method thereof. And to provide a manufacturing method for producing an optical element under the condition of molding a preform using such a glass. The phosphate optical glass has a refractive index (nd) of 1.83 or more and an Abbe number (vd) of 23 to 28. Mole% ratio based on oxides: relative to P₂O₅Content, B₂O₃The content ratio is more than 0.15, or less than 0.3, P₂O₅、B₂O₃The total content is 30-50%; nb₂O₅The content is 15-30%; ta₂O₅The content is 1-5%; li₂O content of 5-15%, ZrO₂0.1-5% of WO₃The content is 0.5-10%; bi₂O₃0 to 3 percent; the ratio of the total content RO to the total content ZnO of MgO, CaO, SrO and BaO is less than 0.2; and further contains Na₂O、K₂The total content of O is 1-15%; the KF content is more than 0 to less than 1.0 percent.

Description

Phosphate optical glass

Technical Field

The present invention relates to a phosphate optical glass and a method for producing a preform for precision press molding. More specifically, the present invention relates to a glass having a specific optical constant and excellent high transmittance and low softening property, and a preform and a method for producing an optical element each comprising the glass.

Background

In recent years, with rapid popularization and continuous improvement and improvement of functions of digital cameras, particularly camera phones, rapid development of high integration and high functionality of optical systems has been promoted. At the same time, demands for higher precision, lighter weight, and smaller size of optical systems have been increasing.

To achieve the above requirements, the use of aspherical lenses has become the mainstream in optical design. Therefore, the high-functional glass aspheric lens is widely used in a large amount at low cost, and is rapidly popularized and applied by a precision press molding technique of directly molding the aspheric lens into an optical functional surface without cutting and grinding. A large number of low-softening glasses with high refractive index, in particular with a refractive index (nd) of more than 1.83 and an Abbe number (vd) of 30, are used in the art todayThe following phosphate optical glass having low-temperature softening properties suitable for press finishing. As such high refractive phosphate optical glass, a large number of glass materials have been shown in the early patent documents, and most of them are suitable for precision press molding. Such as: patent documents CN1298651C, CN1669965A, CN101134641A, CN101041553A and CN 101318770A. However, the glass compositions of these patent documents contain TiO for improving refractive index and dispersion₂Component (B) of a large amount of TiO₂The components are introduced into the phosphate glass, so that the coloring of the glass is deepened, the transmittance is reduced, and the color center of the glass is formed, and the phenomenon needs to be subjected to long-time heat treatment to weaken and eliminate the color center. When the glass after heat treatment is exposed to the irradiation of natural light (ultraviolet ray), the color center eliminated inside the glass will be recovered and deepened, and the glass needs to be treated by adopting a complicated process flow. Even if the color center is eliminated, the glass itself is deeply colored, and thus the glass cannot achieve a high transmittance.

Not only that, TiO₂The composition also increases the PgF value of the glass, which is not favorable for achieving anomalous dispersion of the glass.

For example, a great amount of Bi is also introduced into CN1298651C and CN101134641A₂O₃Components to increase the refractive index and dispersion to achieve low softening of the glass, which further worsens the coloration and transmission of the glass.

Furthermore, CN101134641A, CN1298651C and CN101041553A also contain expensive GeO₂Ingredients and highly toxic As₂O₃And (3) components.

Therefore, it is highly desirable to prepare a phosphate glass having high permeability, low softening properties, and low cost, without involving highly toxic components.

Disclosure of Invention

The content of the invention is as follows: provides a catalyst which does not contain TiO₂A high refractive index phosphate glass as a component, an optical element obtained by forming a preform for precision press-molding from the above optical glass which does not require heat treatment and which does not have a "color center", precision press-molding the above optical glass or a preform, and a method for producing the above optical glass and the above precision press-moldingA method of press-molding a blank and the above optical element. Wherein the optical glass can realize specific phosphate optical glass with high refraction, high dispersion and low relative partial dispersion, and can realize high permeability, high stability and precise moldability.

In the invention, Nb is used respectively₂O₅、Ta₂O₅、WO₃The components are equal to improve the refractive index and the dispersion value, and TiO is avoided₂The coloring caused by the introduction of the component can realize high permeability and stability of the glass by the introduction of the RO component.

By introducing Li₂O component and a small amount of Bi introduced₂O₃Composition, not introducing Bi in large quantity₂O₃The components realize low softening property, and can accelerate the clarification of molten glass, thereby shortening the smelting time.

Sb can be replaced by selecting a trace amount of F component₂O₃Component (b) to achieve the effect of clarifier and further reduce Sb content₂O₃Introducing further deepening of the glass coloration.

Specifically, in order to achieve the purpose, the invention adopts the following technical scheme:

the present invention provides a phosphate optical glass, which has a refractive index (nd) of 1.83 or more and an Abbe number (vd) of 23 to 28:

mole% ratio based on oxides: relative to P₂O₅Content, B₂O₃The content ratio is more than 0.15, or less than 0.3, P₂O₅、B₂O₃The total content is 30-50%; nb₂O₅The content is 15-30%; ta₂O₅The content is 1-5%;

Li₂o content of 5-15%, ZrO₂0.1-5% of WO₃The content is 0.5-10%; bi₂O₃0 to 3 percent; the ratio of ZnO content to the total content RO of MgO, CaO, SrO and BaO is 0.2 or less; and further contains Na₂O、K₂The total content of O is 1-15%; containing KF of > 0- <1.0％。

Furthermore, the total content RO of MgO, CaO, SrO and BaO is 10-45%, wherein the content of ZnO is 0.1-5%.

Further, the CaO content is 0.5-8%, and the MgO content is 0-5%.

Further, the ratio of the content of BaO in the total content RO of MgO, CaO, SrO and BaO is 1.3 or more.

Further, with respect to P₂O₅、B₂O₃Total content of Li2O, Na₂O、K₂The total content ratio of O is less than 1.

Further, the transmission value (. tau.) of spectral transmission (wavelength 400nm) without surface reflection loss was 0.77 or more for a sample piece having a thickness of 10mm in the glass.

Further, the relative partial dispersion (PgF) of the glass is 0.605 or less.

Further, the glass has a softening temperature (Tf) of 620 ℃ or lower and a glass devitrification temperature (LT) of 900 ℃ or lower.

The optical glass is formed into a preform for precision press molding.

A method for producing a preform for precision press molding, in which a uniform glass state flows out of a filler pipe and is molded into a preform in a mold, characterized in that:

a preform for precision press molding comprising the above optical glass is produced and molded.

The invention has the beneficial effects that:

the invention does not contain TiO₂On the premise of components, the characteristics of high refraction, large dispersion and low relative partial dispersion can still be achieved through the optimized design of the components.

The invention has the characteristics of light coloring and high transmission, and the original glass has no color center and light coloring, thereby avoiding fussy heat treatment to eliminate the color center and deepen the color tone after being irradiated by ultraviolet rays again.

In addition, the provided glass with low-temperature softening property can not only reduce the coining temperature, but also prolong the service life of the die (in the case of arranging the demoulding film on the molding surface of the pressure molding die, the service life of the demoulding film is prolonged), realize high-efficiency production and simultaneously reduce the manufacturing cost of the optical element.

Further, the present invention has higher stability in a high temperature state, can increase the glass state forming viscosity, and can efficiently produce a high-quality preform by a method of forming the glass into a preform in a process of separating the glass state flowing out through each specification mold to obtain a cooled glass body.

Obviously, many modifications, substitutions, and variations are possible in light of the above teachings of the invention, without departing from the basic technical spirit of the invention, as defined by the following claims.

The present invention will be described in further detail with reference to the following examples. This should not be understood as limiting the scope of the above-described subject matter of the present invention to the following examples. All the technologies realized based on the above contents of the present invention belong to the scope of the present invention.

Detailed Description

As mentioned above, the phosphate glass of the present invention is solved by not containing TiO₂On the premise of composition, the characteristics of high refraction, high dispersion and low relative partial dispersion are realized. Selection of P₂O₅And B₂O₃As a constituent of the glass network formed, its single P₂O₅The resultant body has poor stability and is difficult to satisfy the stability problem during low-temperature molding, especially when TiO is not introduced₂This is particularly true of the composition of the ingredients.

With P₂O₅、B₂O₃As a component for forming a glass network, B₂O₃And P₂O₅Compared with the prior art, the glass not only can improve the stability of the glass, but also has the effect of reducing relative partial dispersion. But if B is excessively increased₂O₃/P₂O₅The content ratio, glass, in turn, will present a problem of poor stability. In the present inventionIn the plain will B₂O₃/P₂O₅The content ratio is set to 0.15 or more and 0.3 or less.

To compensate for the absence of TiO₂The component causes loss of refractive index and dispersion, including Nb₂O₅、Ta₂O₅、WO₃、Bi₂O₃Etc. as components for increasing the refractive index and dispersion of the glass. To further solve the problem of no coloration, WO₃+Bi₂O₃/Nb₂O₅+Ta₂O₅The content ratio is set to 0.45 or less.

Does not contain TiO₂The composition can eliminate the color center formed by Ti ions in the middle of the glass, and does not need to be subjected to complicated and long-time heat treatment. The high transmission can be realized, and the problem that the glass does not change color again under the irradiation of natural light (ultraviolet rays) is solved.

The low temperature softening property suitable for the coining molding is required to be satisfied, and the high temperature stability and the proper glass viscosity of the high-quality preform can be directly molded from the uniform glass state on the premise of stable mass production. In order to meet the requirements at the same time, the invention combines Nb in the composition₂O₅Ta with the same function is used as the preferred component₂O₅The components are used for improving the stability of the glass and further reducing the devitrification temperature of the glass, and good manufacturability is realized.

To achieve the low softening properties of the invention, R₂O introduced, containing Li₂O、Na₂O、K₂O and Bi₂O₃And the like.

RO is introduced as MgO, CaO, SrO and BaO components for improving the stability and transmittance of the glass, but a part of the total amount of RO introduced may be replaced with ZnO for further improving the stability of the glass, but the ratio of ZnO/RO content introduced is set to 0.3 or less.

The action, the composition range and the limitation factor of each component of the above optical glass will be explained below. The introduced content, the total content and the content ratio of each component are expressed by a molar ratio.

In the phosphate glass of the present invention, P₂O₅Is a mandatory component to form the glass network, since P₂O₅Has the following characteristics: compared with silicate glass, the glass can be melted at a low temperature and has high transmittance in a visible light region. Furthermore, P₂O₅It also has the effects of improving stability and resisting devitrification. However, if the content is too high, the refractive index and dispersion value will be lowered, and the desired specific optical constants will not be obtained. Therefore, the content is 40% at most, preferably 22 to 38%, more preferably 24 to 37%, and particularly preferably 26 to 37%.

B₂O₃The phosphate glass is also a component forming a glass network, and has the functions of adjusting refractive index, dispersion and relative partial dispersion and improving glass stability, and when the phosphate glass contains P in a proper amount₂O₅、Nb₂O₅And Ta₂O₅When the glass is introduced, the devitrification resistance of the glass can be improved. Thus, B₂O₃The appropriate amount is preferably 5%, but if it exceeds 10%, it will be difficult to obtain desired optical properties. Thus, B₂O₃Preferably 5 to 9%, more preferably 5 to 8%.

P is preferred from the viewpoint of glass stability, resistance to devitrification and optical properties₂O₅、B₂O₃The total content of (A) is preferably 31 to 45%. Relative to B₂O₃/P₂O₅The content ratio of (b) is preferably 0.15 or more and 0.3 or less. In the glass of the present invention, Nb₂O₅Is an important component with high refractive index and high dispersibility. If the content of the incorporated compound is too small, the desired specific optical constant cannot be obtained, and if the content of the incorporated compound is too high, the solubility of the glass is deteriorated, the stability is lowered, the coloring of the glass is increased, the internal permeability is lowered, and the softening temperature is increased, so that the precision press molding is difficult to be performed. When the content is too small, it is difficult to obtain the desired specific optical constants, and the stability is lowered. Thus, Nb₂O₅The content of (c) is preferably 15 to 30%, more preferably 16 to 29%, still more preferably 17 to cA range of 28%.

In the glass of the present invention, Ta₂O₅The glass has the advantages of greatly improving the stability of the glass, reducing the devitrification temperature, improving the refractive index and enabling the optical constant to reach a specific range. If Ta₂O₅If the amount of (A) is too small, the glass will have a low refractive index and a low dispersion value, and will have poor stability. However, if the amount of the glass is excessively introduced, the refractive index and dispersion ratio of the glass become unstable, and the density and cost of the glass increase. Thus, Ta₂O₅Preferably in the range of 0.5 to 5%, the lower limit in the above range is preferably 1.5% or less, the upper limit is preferably 5% or less, more preferably 4% or less, Ta₂O₅The content is particularly preferably in the range of 1 to 3%.

ZrO₂The glass of the present invention has the effects of improving the stability and resistance to devitrification and adjusting the optical constants, and when it is excessively introduced, not only the refractive index is lowered and the Abbe number is increased, but also the solubility of the glass is deteriorated and the softening temperature is increased. Thus, ZrO is oxidized₂The content of (b) is limited to 5%, and the content is preferably 0.1 to 5%, more preferably 0.5 to 4%, and further preferably 0.5 to 3.5% or less.

BaO not only has the functions of improving the solubility and stability of glass and reducing devitrification, but also has the function of inhibiting WO₃、Bi₂O₃The components have the function of increasing the coloring tendency of the glass, are also favorable for adjusting the optical constant and the low relative partial dispersion, and are necessary components of the phosphate glass. However, if the amount of the glass is excessively increased, the refractive index and dispersion of the glass are decreased, and the glass devitrification is also deteriorated, so that the softening temperature is increased, which is disadvantageous for precision press-molding. Therefore, the BaO content is preferably 10 to 25%, more preferably 11 to 24%, and further preferably 12 to 22%.

CaO component is in a range of from P2O5 and Nb₂O₅The coexisting components of the components can adjust and reduce the relative partial dispersion and softening temperature. Therefore, the amount of CaO incorporated is preferably 0.5% or more, more preferably 0.5 to 8%, still more preferably 1 to 7%, particularly preferably 1 to 5.5%。

The MgO and SrO components having the same family as BaO and CaO also have the effects of adjusting the refractive index and relative partial dispersion, and P is the content of₂O₅、Nb₂O₅The composition in which the components coexist also has an effect of lowering the softening temperature. However, if the amount of the glass is excessively increased, the stability of the glass is deteriorated, the refractive index is lowered, and the high-temperature viscosity of the glass is reduced, so that it is difficult to satisfy the requirements of molding and coining. Therefore, the total content of the two components is preferably 0 to 10%, more preferably 0 to 8%, and still more preferably 0 to 6%.

ZnO has the effects of improving devitrification resistance and reducing softening temperature, and particularly has the effect of improving the stability compared with divalent oxides, while BaO is a component for improving the refractive index and the stability but reduces the stability. Thus, a portion of the BaO may be replaced with ZnO to improve the conditioning effect of the ZnO. The content of ZnO is preferably 0.1-5%, more preferably

Preferably 0.5 to 5%, and more preferably 0.5 to 4%.

The total content RO of MgO, CaO, SrO and BaO is set to a ZnO content ratio (Zn/RO) of 0.4 or less, preferably 0.35 or less, and more preferably 0.3 or less.

Li₂O and Na₂O、K₂The alkali metal oxide of the same group as O is a glass having a glass softening temperature greatly reduced, a glass melting property improved, and a glass viscosity increased during molding. In the present invention, Li₂If the amount of O as an essential component of the present invention is too small, it is difficult to lower the softening temperature, but if it is excessively introduced, not only the refractive index and dispersion value are lowered, but also the glass devitrification is deteriorated, and the surface is made opaque in glass molding and precision press molding. Therefore, in the present invention, Li₂The O content is controlled to be 5 to 15%, preferably 6 to 14%, and more preferably 6 to 13.5%.

In the presence of Na₂O、K₂While taking Li into account in the composition of O₂The above-mentioned effects of O, Li₂O content and Na₂O、K₂O content (Li)₂O/Na₂O+K₂O) ratio is preferably greater than 1.0, more preferably greater than 1.5, particularly preferably greater than 2.0.

K₂O and Li₂And the same O also has the effects of reducing softening temperature, improving the solubility of the glass and lightening the coloring of the glass. Especially in P₂O₅And Nb₂O₅The composition of (A) is introduced excessively, so that the refractive index of the glass is reduced, the glass processing performance is deteriorated, the relative partial dispersion is increased, and the forming and precision die pressing are not facilitated. Therefore, the amount of incorporation thereof is preferably 1 to 10%, more preferably 1 to 8%, and particularly preferably 1 to 7%.

Na₂O and K₂O is the same as the above-mentioned component(s), and has an effect of improving the glass stability, lowering the softening temperature and devitrification temperature, suppressing the adhesion of a press mold in precision press molding, improving the mold release, and improving the solubility. However, if the content is too large, the refractive index is lowered, the viscosity of the glass is decreased, and the stability is remarkably deteriorated. Therefore, the content thereof is preferably 0 to 5%, more preferably 0 to 3%, and further preferably 0 to 2% or less.

WO₃Is an important component for imparting high refraction and high dispersion to glass, and also has the effects of resistance to devitrification, increase in viscosity of glass at the time of molding, suppression of wettability between glass gob and mold in precision press molding, and improvement of mold releasability. However, when WO is used₃If the amount is too large, the coloration of the glass is also increased by the glass according to the invention. Thus, WO₃The content is controlled in the range of 0.5 to 10%, preferably 1 to 8%, more preferably 1 to 7% or less.

Bi₂O₃Has the functions of improving refractive index and dispersion, reducing softening temperature of glass, and improving stability and chemical stability. However, when Bi₂O₃When the content of (A) is excessively large, the coloring of the glass becomes remarkably deep and the density increases. Thus, Bi₂O₃The content of (b) is preferably 0 to 3%, more preferably 0 to 2.5%, and further preferably 0 to 2%.

KF is useful not only as a fining agent, but also as an effective additive for controlling and reducing glass coloration, particularly when containing Bi₂O₃、WO₃The glass with high content is an effective component for controlling and lightening the coloring of the glass. However, if the content of the additive is too high, the refractive index of the glass is lowered, the surface volatilization of the molten glass during melting is increased, the stability is deteriorated, and the surface volatilization streaks are likely to be formed during molding. Therefore, the content is preferably 0.1 to 1%, more preferably 0.1 to 0.5%, and particularly preferably 0.1 to 0.3% or less. The invention has the composition consisting of the essential components and optional components. In the glass of the present invention, P₂O₅、B₂O₃、Nb₂O₅、Ta₂O₅、ZrO₂、MgO、CaO、SrO、BaO、Li₂O、Na₂O、K₂O、

ZnO、WO₃、Bi₂O₃The total content of KF is preferably 95%, more preferably 97%, still more preferably 99%, and still more preferably 100%. It is desirable for clarification and lightening of coloration as a trace addition of KF for clarification.

Characteristics of the optical glass of the present invention

The properties of the optical glass of the present invention will be explained below, and in the present invention, the following desired properties can be achieved depending on the glass composition set, and particularly, the various components introduced within the above preferred ranges:

the optical glass of the present invention has an optical characteristic in which the refractive index (nd) is 1.83 or more and the Abbe number (vd) is within a range of 23 to 28, preferably the refractive index (nd) is 1.84 or more and the Abbe number (vd) is within a range of 24 to 27.

The relative partial dispersion (PgF) at its state point is preferably 0.605, more preferably 0.595, particularly preferably 0.59 or less.

Because TiO is not contained₂The component (B) is preferably 0.77 or more, more preferably 0.78 or more, in terms of the internal transmittance of the present invention, without a color center or coloration. And no special heat treatment is required.

The optical glass of the present invention has a low-temperature softening property suitable for press molding, and the softening temperature ((Tf) of the glass is preferably 620 ℃ or lower, more preferably 600 ℃ or lower, and particularly preferably 590 ℃ or lower in the state point.

In the optical glass, as the softening temperature is lowered, not only the heating temperature at the time of press molding can be lowered, but also the time required for temperature rise and temperature decrease can be shortened, thereby improving the productivity of press-molded products. Therefore, the service life of the coining forming die is prolonged along with the reduction of the heating temperature.

The optical glass of the present invention, in order to achieve a high-temperature state of the glass solution without devitrification and with a large molding viscosity, preferably has a devitrification temperature (LT) of 900 deg.C, more preferably 890 deg.C or less at its state point.

Has stability in a high temperature state, and has a high temperature viscosity suitable for good molding. Therefore, a preform for press molding can be molded directly from a molten glass state and, in the course of cooling, molded.

The optical glass of the present invention is suitable for precision press-molding and is excellent also in the production of optical elements by cutting, grinding, polishing and secondary press-molding.

Examples optical glasses according to the invention

Hereinafter, the present invention will be described in further detail with reference to examples given without being limited thereto.

In examples, physical properties of glass were measured by the following methods

(1) The glass sample obtained after cooling at a cooling rate of-4.0 ℃ per hour was measured for the refractive index (nd) Abbe number (vd) versus the partial dispersion (PgF).

(2) The softening temperature (Tf) was measured by a thermal analyzer according to GB/7962016-.

(3) The internal transmission is a transmission at which reflection loss on the sample surface is not included, and is measured by a measurement method specified in GB/T7962.12. The spectral transmission is determined by measuring samples with a thickness of 10mm at a wavelength of 400 nm.

(4) Glass devitrification temperature (LT): the glass frit is placed in a 100ml platinum crucible, placed in a test furnace set at intervals of 10 ℃, and kept at different temperatures for 2 hours to obtain a sample, whether devitrified particles appear or not is observed by a microscope, and the lowest temperature at which no crystal particles are confirmed is taken as a devitrification temperature (LT).

Examples 1 to 14

The optical glasses of examples 1 to 14 were prepared by a conventional compounding method to have glass compositions shown in the following items 1 and 2. In various examples, various metaphosphates were used as P₂O₅The raw materials used are other raw materials such as various oxides, carbonates, nitrates and the like, and the raw materials are weighed and mixed, then the raw materials are added into a melting furnace at 1100-1250 ℃, the raw materials are melted, clarified and stirred, the formed uniform glass state is poured into a mould, and then a glass sample is obtained after annealing and cooling, or the glass sample without bubbles is obtained by changing process conditions and adjusting process parameters.

Tables 1 and 2 optical physical Properties of glasses thus obtained

As shown in tables 1 and 2, in examples 1 to 14, the measured values of internal transmission are measured values of internal transmission (. tau.) obtained without heat treatment.

Comparative examples a to e in Table 3 also obtained optical glasses having the compositions shown by the same production methods as in examples 1 to 14, and optical physical properties of the optical glasses are shown.

The color centers present in comparative examples a-e, shown in Table 3, were processed to give internal transmission (. tau.) measurements after a slow heat treatment of each of the comparative samples.

TABLE 1 examples (mol%)

TABLE 2 examples (mol%)

TABLE 3 comparative example (mol%)

Optical properties in the examples of the present invention: the refractive index (nd) is 1.83-1.88, the Abbe number (vd) is 23-27, and the relative partial dispersion (PgF) is 0.605 or less.

The comparative examples had refractive indices (nd) close to those of the above examples, but had Abbe numbers (vd) of less than 23 and relative partial dispersions (PgF) of 0.619 or more.

The examples of the present invention do not contain TiO₂Component (c) has an internal transmission (. tau.) value of 0.77 or more because it has no color center and no color depth problem.

In contrast, the phosphate glasses of the type in the comparative examples, which contain not only TiO₂Component (B) and most of the component (B) also introduces high content of Bi₂O₃The component (D) is not only a glass having a deep coloring and a color center, but also a glass having a deep coloring itself and having a maximum internal transmission (. tau.) of only 0.722, though it is subjected to a heat treatment.

As comparative example a, it contains not only TiO₂Contains at least one component selected from GeO and GeO₂Component (b), not suitable for mass production, and Na introduced in large amount₂The O component also deteriorates the glass stability.

Comparative example d in the presence of TiO₂At the same time of the components, and also introduces a large amount of WO₃Ingredients, even more accentuate glass staining and lower in-vivo penetration.

In summary, the present invention provides optical glass and various optical elements for precision press molding, which have high refractive index, high dispersion and low relative partial dispersion, are free from coloring and color centers, have high transmittance, do not require complicated heat treatment, and have low softening properties.

The present invention can provide a preform formed of the above optical glass, and can produce various lenses such as aspherical lenses, spherical lenses, microlenses, prisms having a lens function, optical filters, and the like.

Claims

1. A phosphate optical glass characterized by: a refractive index of 1.83 or more, an Abbe number of 23 to 28, a relative partial dispersion of the glass of 0.605 or less, and a molar percent ratio based on oxides:

P₂O₅、B₂O₃the total content is 30-47%; p₂O₅22-38% of B₂O₃The content of P is 5-9%₂O₅Content of B₂O₃The content ratio is more than 0.15 and less than 0.3,

Nb₂O₅the content is 15-30%; ta₂O₅The content is 1-5%;

ZrO₂0.1-5% of WO₃The content is 0.5-10%; bi₂O₃0 to 3 percent; and WO₃+Bi₂O₃/Nb₂O₅+Ta₂O₅The content ratio is set to be less than 0.45;

Li₂o content of 5-15%, K₂O content of 1-10%, Na₂O content is 0-5% relative to P₂O₅、B₂O₃Total content of (B), Li₂O、Na₂O、K₂The total content proportion of O is less than 1; while Li₂O content and Na₂O、K₂The ratio of the O content is more than 1.0;

the BaO content is 10-25%; the CaO content is 0.5-8%, and the MgO content is 0-5%; the total content of MgO and SrO is 0-10%;

ZnO content is 0.1-5%, and the ratio of ZnO content to total content RO of MgO, CaO, SrO and BaO is less than 0.2;

and KF is more than 0 to less than 1.0%.

2. The optical glass according to claim 1, wherein: the internal transmission of the glass is 0.77 or more in terms of a sample piece having a thickness of 10mm and a spectral transmission value not including surface reflection loss at a wavelength of 400 nm.

3. The optical glass according to claim 1 or 2, characterized in that: the softening temperature of the glass is below 620 ℃, and the devitrification temperature of the glass is below 900 ℃.

4. A preform for precision press molding made of the optical glass according to claim 1 or 2.

5. A method for producing a preform for precision press molding, in which a uniform glass state flows out of a filler pipe and is molded into a preform in a mold, characterized in that: a preform for precision press molding comprising the optical glass according to claim 1 or 2 is produced and molded.