JP2002128540A - Optical glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical glass which is free from Pb having adverse effect on the human body and is also free from As and which has low photoelastic constant and sufficiently low liquid phase temperature and has high transmissiveness and low in refractive index. SOLUTION: The optical glass contains glass components of 40 to 46 wt.% in P2O5, 49 to 57 w% in BaO, and 0.1 to 7 w% in Bi2O3. From the viewpoint of chemical resistance or adjustment of optical constant, one or more of glass components having Al2O3 of <=3 wt.%, La2O3 of <=3 wt.%, CaO of <=3 wt.%, SrO of <=7 wt.%, WO3 of <=3 wt.% and Nb2O5 of <=3 wt.% may be contained. Also from the viewpoint of clarifying when glass is melted, Sb2O3 may further be contained in the glass in amount of <=0.5 pts.wt. with respect to the total amount of 100 pts.wt. of the glass component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an optical glass,
More specifically, the present invention relates to an optical glass containing no Pb or As and having a small photoelastic constant.

[0002]

2. Description of the Related Art A polarizing beam splitter in a projection type display device such as a liquid crystal projector selectively transmits only a p-wave polarization component of an incident light beam and reflects an s-wave polarization component in a direction of 90 ° to form a laser beam. If an optical element that separates light into two components and an optical glass whose photoelastic constant is not sufficiently small is used for a substrate or a prism constituting such a polarizing beam splitter, the polarization characteristics of the incident beam light can be sufficiently improved. Cannot be maintained, which causes a decrease in polarization separation efficiency and transmittance. Therefore, taking into account recent trends in increasing the brightness of liquid crystal projectors, optical glasses used in such polarizing beam splitters include:
Those having a small photoelastic constant, high transmittance, and isotropic properties are desirable.

Various proposals have heretofore been made as optical glasses satisfying such characteristics. For example, JP-A-11-335135 and JP-A-11-133528
JP-A-7-215732, JP-A-8-215732
JP-A-59259 and JP-A-11-258401 propose a SiO ₂ —PbO-based low photoelastic constant glass.

[0004] However, these proposed optical glasses use PbO, which has a fear of adversely affecting the human body, in order to reduce the photoelastic constant, which goes against recent social demands for environmental safety. Was. In addition, SiO ₂ −
Since PbO-based optical glass has poor transmittance and high refractive index, a polarizing beam splitter using SiO ₂ -PbO-based optical glass requires several tens of dielectric multilayer films to be laminated on the polarizing beam splitter. Was.

[0005] Therefore, each of the optical glasses having a low photoelastic constant containing no Pb has recently been proposed but has a problem. For example, Japanese Patent Application Laid-Open No. 11-60267 proposes a BaO-containing fluorophosphate optical glass. However, since it contains fluorine, it is inferior in melting property and it is difficult to stably produce a large glass. Also, Japanese Patent Application Laid-Open
In Japanese Patent Application Laid-Open No. 1-199269, a BaO-containing phosphate optical glass is proposed, but the photoelastic constant of the optical glass proposed here does not yet provide a satisfactory performance. Furthermore, Japanese Patent Application Laid-Open No. 2000-34132 proposes a P ₂ O ₅ —BaO—Al ₂ O ₃ optical glass, but it is still difficult to stably produce a large glass having a high liquidus temperature. It is.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and is an optical glass containing no Pb or As, which is likely to have a bad influence on the human body. Small elastic constant (+ 5.0 × 10 ^-12
Pa or less), and the liquid phase temperature is sufficiently low, yet has a high transmittance, is to to provide a refractive index lower (n _d is 1.7 or less) optical glass and its purpose.

[0007]

According to the present invention, the weight%
_{In, P 2 O 5: 40~46%} , BaO: 49~57%, B
i ₂ O _3: optical glass characterized in that it contains from 0.1 to 7% of the glass ingredient.

From the viewpoint of the adjustment of chemical durability and optical constants, Al ₂ O ₃ : 3% or less, La ₂ O ₃ : 3% or less, CaO: 3% or less, SrO: 7% or less by weight%. WO ₃ : 3
% Or less, and Nb ₂ O ₅ : It is preferable to further contain one or more kinds of glass components of 3% or less.

Further, from the viewpoint of refining at the time of melting the glass, Sb is added to 100 parts by weight of the total amount of each glass component.
_It is preferable to further contain ₂ O ₃ in a range of 0.5 part by weight or less.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies to obtain optical glass having a small photoelastic constant and a sufficiently low liquidus temperature without using Pb or As which is likely to affect the human body. As a result of overlapping, at least P ₂ O ₅ and B
The present inventors have found that if the aO and Bi ₂ O ₃ are contained in a predetermined range, the above-mentioned optical glass can be obtained, and the present invention has been accomplished.

That is, the present invention is to solve the conventional problems comprehensively by selecting the type and combination of glass components and adjusting the content thereof. In particular, the liquid phase temperature increased by the addition of BaO Has an important feature in that the addition of Bi ₂ O ₃ is added in an appropriate amount.

Hereinafter, the reasons for limiting the components of the optical glass of the present invention will be described. Unless otherwise specified,% means% by weight.

First, P ₂ O ₅ is a main component forming an optical glass. When the content of P ₂ O ₅ is less than 40%, the glass tends to be devitrified. On the other hand, when the content exceeds 46%, the chemical durability is lowered and + 5.0 × 10 ⁻¹² P
It is difficult to obtain a low photoelastic constant of a or less. So, to be in the range of the content of P ₂ O ₅ of 40-46%. A more preferred content is in the range of 40-45%.

BaO has a function of reducing the photoelastic constant and stabilizing the glass. If the BaO content is less than 49%, such an effect cannot be sufficiently obtained. On the other hand, if the content exceeds 57%, the glass tends to be devitrified. Therefore, the content rate is set in the range of 49 to 57%. A more preferred content is in the range of 40-45%.

Bi ₂ O ₃ has a function of lowering the liquidus temperature of the phosphate glass. The content of Bi ₂ O ₃ is 0.1%
If it is less than this, such an effect cannot be obtained. On the other hand, when the content exceeds 7%, the light transmittance of the optical glass decreases.
Therefore, the content rate is set in the range of 0.1 to 7%. A more preferred content is in the range of 0.1-5%.

Further, Al ₂ O ₃ , La ₂ O ₃ , CaO, Sr
A specific amount of one or more glass components of O, WO ₃ , and Nb ₂ O ₅ may be further contained as necessary. The reasons for limiting to these glass components will be described below.

Al ₂ O ₃ improves the chemical durability of the phosphate glass, but if its content exceeds 3%, the tendency of the glass to become devitrified increases. Therefore, the content is preferably 3% or less. A more preferred upper limit of the content is 2.5%.

La_TwoO_ThreeIs the chemical durability of phosphate glass
In addition to the action to improve the _TwoO_ThreeOptical
Has the effect of lowering the liquidus temperature of the lath
If the amount exceeds 3%, the photoelastic constant increases. So including
The content is preferably 3% or less. Upper limit of more preferable content
Is 2.5%.

CaO and SrO have a role of adjusting optical constants, and also have a function of improving devitrification resistance. However, if the content exceeds 3% of CaO and 7% of SrO, the glass tends to be devitrified.
% Or less, and SrO is preferably 7% or less. More preferred S
The upper limit of the rO content is 6.5%.

Although WO ₃ has a role of adjusting the optical constant, if its content exceeds 3%, the light transmittance is reduced and the photoelastic constant is increased. So the content is 3%
The following is preferred. A more preferred content is 2%.

Nb ₂ O ₅ has a role of adjusting the optical constant, but if its content exceeds 3%, the photoelastic constant increases. Therefore, the content is preferably 3% or less. A more preferred content is 2%.

Further, as a fining agent, Sb ₂ O ₃ may be contained in a range of 0.5 part by weight or less based on 100 parts by weight of the total amount of the above-mentioned respective glass components. The content is set to 0.5 part by weight or less because a sufficient clarifying action can be obtained by containing 0.5 part by weight.

Furthermore, the present invention is used for adjusting the refractive index and viscosity.
As long as the light effect is not impaired, SiO _TwoAnd GeO_Two, Y
_TwoO_Three, Gd_TwoO_Three, Yb_TwoO_Three, Ga_TwoO_Three, ZrO_Two, Ta_Two
O_Five, TiO_Two, TeO_Two, Tl_TwoO_ThreeOne of the glass components of
Alternatively, two or more kinds may be combined and further contained.
No. The content of these glass components is not particularly limited, but is generally
Is preferably 5% by weight or less.

If necessary, a conventionally known additive may be added in an appropriate amount as a glass component.

The method for producing the optical glass of the present invention is not particularly limited, and a conventionally known production method can be used. For example, oxides each corresponding as a raw material of each component,
Carbonates, nitrates, hydroxides and the like are used, weighed to a desired ratio, and sufficiently mixed with powder to prepare a blended raw material. This is put into, for example, a platinum crucible in an electric furnace heated to 1,000 to 1,300 ° C., melted and clarified, stirred and homogenized, cast into a pre-heated iron mold, and gradually cooled to be manufactured. .
Alternatively, continuous production may be performed using a continuous dissolution apparatus.

The optical glass of the present invention can be used as an optical component or an optical product such as a substrate or a prism constituting a polarizing beam splitter, a spatial light modulator for performing polarization modulation, a glass substrate or a glass component for electro-optics. In particular, it can be suitably used as an optical component used in a device having a high internal temperature such as a projection display device such as a liquid crystal projector.

[0027]

EXAMPLES The present invention will be described more specifically with reference to the following examples. The present invention is not limited to these examples, and in the examples, “%” means “% by weight” unless otherwise specified.

Examples 1 to 9 and Comparative Examples 1 to 4 Oxides, carbonates, nitrates, and the like, which are glass raw materials, are mixed so as to have the target compositions shown in Tables 1 and 2, and thoroughly mixed with powder. To make a blended raw material,
Each sample was put into a platinum crucible in an electric furnace heated to 300 ° C., melted and clarified, stirred and homogenized, poured into a pre-heated iron mold, and gradually cooled to produce each sample. The photoelastic constant (β) and liquidus temperature (L.
T. ), The refractive index at the d-line (n _d), Abbe number ([nu _d), coloring degree was respectively measured as follows. The measurement results are shown in Tables 1 and 2.

(Photoelastic constant) A glass sample that has been subjected to precision annealing is processed to a light transmission thickness of 15 mm, and a complex formed when a He—Ne laser beam is transmitted between a stressed state and a non-stressed state. The photoelastic constant was calculated by measuring the optical path difference due to refraction.

(Liquid phase temperature (LT)) 650 to 1,0
Leave the glass in a furnace with a temperature gradient of
After a minute, the glass was taken out and softened, and the presence or absence of crystals was observed under a microscope. The lowest temperature at which no crystals were observed was taken as the liquidus temperature.

(Refractive index (n _d ), Abbe number (ν _d ), degree of coloring) The refractive index (n _d ) and Abbe number (ν _d ) are measured according to the test method of the Japan Optical Glass Industrial Standards (JOGIS). I went according to. The wavelength (λ ₈₀ ) at which the spectral transmittance of the sample having a thickness of 10 mm gives 80% was measured as the degree of coloring.

[0032]

[Table 1] (Unit: wt%)

Examples 1 and 2 and Comparative Examples 1 to 4 shown in Table 1
Is the relationship between the content of BaO and the photoelastic constant and Bi ₂
It is an experimental example conducted to investigate the relationship between the O ₃ content and the liquidus temperature. According to Comparative Examples 4 to 1, when the content of BaO is increased from 53.0% to 55.0%, the photoelastic constant β decreases from 0.40 to 0.32, while the liquidus temperature (L .T.) Increased from 850 ° C. to 870 ° C. On the other hand, according to Examples 1 and ₂ , Bi ₂ O ₃ was adjusted to 5.0.
% And 3.0%, the liquidus temperature (LT) becomes 7
The temperature dropped to 90 ° C. From this, BaO and Bi ₂ O ₃
It can be understood that the photoelastic constant can be reduced while maintaining the liquidus temperature low by adjusting the content of. Also Bi
_In Comparative Example 5 in which the content of ₂ O ₃ was excessively increased to 10%, the wavelength (λ ₇₀ ) at which the spectral transmittance gave 70% was 538.
nm and remarkable coloring were observed. Therefore, in Comparative Example 5, other characteristics such as the photoelastic constant and the liquidus temperature were not measured. Comparative Examples 1, 2, 3, and 4 are disclosed in
No. 34132, Examples 3, 21, 22, and 13 are cited, respectively.

[0034]

[Table 2] (Unit: wt%)

In Examples 3 to 9 shown in Table 2, P ₂ O ₅ , Ba
The content of O and Bi ₂ O ₃ was changed variously.
In all of the optical glasses of Examples 3 to 9 satisfying the glass component and content specified in the present invention, the photoelastic constant is +0.
It showed a small value of 43 × 10 ⁻¹² Pa or less, and the liquidus temperature was 830 ° C. or less, which was lower than that of the comparative example by 20 ° C.

[0036]

According to the optical glass of the present invention, by weight%, P
_{2 O 5: 40~46%, BaO} : 49~57%, Bi
₂ O ₃ : 0.1 to 7% of glass component contained,
The liquidus temperature can be sufficiently lowered while maintaining a low photoelastic constant of 5.0 × 10 ⁻¹² Pa or less, and a large-sized one can be manufactured stably, and a high transmittance and a small refractive index ( n _d is 1.7 or less) can be obtained.

Al ₂ O ₃ : 3% or less by weight, La
_When one or more glass components of ₂ O ₃ : 3% or less, CaO: 3% or less, SrO: 7% or less, WO ₃ : 3% or less, Nb ₂ O ₅ : 3% or less are further contained. In addition, the chemical durability can be improved and the optical constant can be adjusted.

Further, when Sb ₂ O ₃ is further contained in a range of 0.5 part by weight or less based on 100 parts by weight of the total amount of each of the above glass components, fining at the time of melting the glass can be further achieved.

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Claims (3)

[Claims] 1. P ₂ O ₅ : 40-46% by weight, Ba
_{O: 49~57%, Bi 2 O} 3: 0.1~7% of optical glass characterized by containing the glass component. 2. Al ₂ O ₃ : 3% or less by weight, La ₂
O _3: 3%, CaO: 3% or less, SrO: 7% or less, WO _3: 3% or less, Nb ₂ O _5: further claims containing one or more glass components 3% or less 2. The optical glass according to 1. 3. The optical glass according to claim 1, further comprising Sb ₂ O ₃ in a range of 0.5 part by weight or less based on 100 parts by weight of the total amount of each glass component.