JP2003160356A - Optical glass and optical part - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical glass with low density having an abnormal part dispersion characteristic suitable for optical parts such as a lens, and optical parts using the same. <P>SOLUTION: The optical glass with ≥1.54 to <1.60 refractive index (nd), 70 to 80 Abbe's number (νd) and <4.1 specific gravity containing P, Al and Ba as cationic components and oxygen and fluorine as anionic components or the optical glass with ≥1.54 to <1.60 refractive index (nd) and 70 to 80 Abbe's number (νd) which is obtained from a batch composition comprising as cationic components, in terms of cationic % expression, 20 to 60% P, 10 to 30% Al, 10 to 50% Ba, 0 to 25% Sr, 0 to 20% Ca, 0 to 15% Y and 0 to 15% La, and as anionic components, oxygen and fluorine are illustrated. The optical parts comprise these optical glasses. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical glass and an optical component. More specifically, the present invention relates to an optical glass having low specific gravity having anomalous partial dispersion characteristics, and an optical component such as a lens using the optical glass.

[0002]

2. Description of the Related Art Optical glass exhibiting anomalous partial dispersion in a region of low refractive index and low dispersion is used for various optical parts such as camera lenses. As such an optical glass, for example, the refractive index (nd) is 1.54 to
A fluorophosphate optical glass having an optical constant of 1.60, an Abbe number (νd) of 68 to 75, and an abnormal partial dispersion having a partial dispersion ratio of 0.537 or more is disclosed (JP-A-2-124740). Issue).

Lenses made from extraordinary partial dispersion glass are effective for chromatic aberration correction. In particular, a telephoto lens, in which chromatic aberration is more problematic, is originally composed of a large number of lenses, and if each lens is heavy, the total weight becomes heavy and the operability deteriorates. Further, when a telephoto lens having a small F-number is produced, a lens having a large aperture is required, and the total weight becomes heavy even if the lens is made large. In the telephoto lens, a lens made of anomalous partially dispersed glass is often used in the front group. Therefore, a lens made of anomalous partially dispersed glass often has a large aperture, and the weight of one lens also becomes heavy. With such a telephoto lens,
In addition to the problem of total weight, the tip of the lens becomes heavy and the balance is not good.
There are also problems that the focus speed becomes slow, a large torque is required, and the battery of the camera is significantly consumed. In order to overcome such problems, low specific gravity anomalous partially dispersed glass is required.

However, in general, glass tends to have a higher specific gravity as the refractive index increases. This is because a high valence component having a large molecular weight is used to increase the refractive index. Therefore, if an attempt is made to increase the refractive index while keeping the Abbe number within a certain range, the specific gravity of the glass also increases, and it is not easy to obtain an abnormal partially dispersed glass having a low specific gravity.

[0005]

Under the circumstances, the present invention uses a low specific gravity optical glass having anomalous partial dispersion characteristics suitable for optical parts such as lenses, and the optical glass. The object is to provide an optical component such as a lens having a low specific gravity.

[0006]

As a result of intensive studies to develop an optical glass of low specific gravity having anomalous partial dispersion characteristics, the present inventor has a specific cationic component and an anionic component, and It has been found that the above object can be achieved by an optical glass having an optical constant and a specific gravity, or an optical glass having a specific optical constant obtained from a batch composition having a cationic component and an anionic component of a specific composition. The present invention has been completed based on the above.

That is, according to the present invention, (1) P, Al and Ba are contained as a cationic component, and oxygen and fluorine are contained as an anionic component, and the refractive index (nd) is 1.54 or more and less than 1.60 and the Abbe number. (Νd) is 70 ~
80 and an optical glass having a specific gravity of less than 4.1 (hereinafter referred to as optical glass 1), and (2) at least one selected from Sr, Ca, Y and La as a cationic component. The optical glass according to the above item (1), including

(3) As the cationic component, P is 20 to 60% and Al is 10 to 30 in the cationic% display.
%, Ba 10 to 50%, Sr 0 to 25%, Ca 0
-20%, Y 0-15% and La 0-15%, and a glass containing oxygen and fluorine as an anionic component, having a refractive index (nd) of 1.54 or more and less than 1.60, An optical glass having an Abbe number (νd) of 70 to 80 (hereinafter referred to as optical glass 2),

(4) In mol% display, P is 5 to 20%, A
1 to 15%, Ba to 1 to 18%, Sr to 0 to 10
%, Ca 0-10%, Y 0-5%, La 0-5
%, O of 20 to 55% and F of 18 to 48%, the refractive index (nd) is 1.54 or more and less than 1.60, and the Abbe number (νd) is 70 to 80. Characteristic optical glass (hereinafter referred to as optical glass 3),
(5) The above (3) or (4) having a specific gravity of less than 4.1
And (6) an optical component made of the optical glass according to any one of (1) to (5) above.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In completing the present invention, the rate of increase in specific gravity with respect to the refractive index was predicted to some extent by the composition system. The rate of increase is fluorophosphate glass, silicate glass (but containing Pb), phosphate glass,
It becomes smaller in the order of silicate glass (however, it does not contain Pb). The composition system of glass having a low refractive index and extraordinary partial dispersibility is fluorophosphate glass, which has a high specific gravity with respect to the refractive index.

On the other hand, the present inventors have found that P-Al-Ba
In the system fluorophosphate glass, the object of the present invention can be achieved, and by defining the content ratio of each component of P, Al, Ba, O and F in a specific range, low specific gravity,
It was discovered that an optical glass that simultaneously realizes a low refractive index, anomalous partial dispersion characteristics, and devitrification resistance can be obtained. The optical glass of the present invention has three modes, that is, optical glass 1, optical glass 2 and optical glass 3. Each optical glass will be described below.

First, the optical glass 1 of the present invention contains P, Al and Ba as a cationic component, oxygen and fluorine as an anionic component, and has a refractive index (n
An optical glass having d) of 1.54 or more and less than 1.60, Abbe number (νd) of 70 to 80, and specific gravity of less than 4.1. If desired, S may be added as a cationic component.
at least 1 selected from r, Ca, Y and La
Species can be included, and Mg, Zn, Li, Na, K, Gd, and the like can be included as optional cationic components. In addition, Pb, As, Te
It is preferable to exclude toxic components such as, and also to exclude Sn.

The optical glass 1 has an optical constant whose refractive index (nd) and Abbe's number (νd) are in the above ranges, and exhibits anomalous partial dispersion characteristics in such a low refractive index and low dispersion region. The glass shown has a specific gravity of 4.1.
It has low and low characteristics. The action of each component will be described in the following optical glass 2 and optical glass 3.

Next, in the optical glass 2 of the present invention, P is 20 to 60 as a cationic component in a cationic percentage display.
%, Al 10 to 30%, Ba 10 to 50%, Sr 0 to 25%, Ca 0 to 20%, Y 0 to 15% and La 0 to 15%, and as an anionic component, A glass containing oxygen and fluorine, having a refractive index (nd) of 1.54 or more and less than 1.60 and an Abbe number (ν
d) is an optical glass of 70 to 80, while the optical glass 3 is 5 to 20% of P and 1 to 1 of Al in mol% display.
5%, 1-18% Ba, 0-10% Sr, 0 Ca
-10%, Y 0-5%, La 0-5%, O 20-
A glass containing 55% and F of 18 to 48%, an optical glass having a refractive index (nd) of 1.54 or more and less than 1.60 and an Abbe number (νd) of 70 to 80.

The reason for limiting the content of each component in the optical glasses 2 and 3 will be described. P (phosphorus)
Ions act as a glass-forming oxide and are an essential component for stabilizing the glass structure, that is, increasing the stability against devitrification. When the content of P ions is less than the lower limit of the above range, the stability of the glass against devitrification deteriorates, and when the content of P ions exceeds the upper limit of the above range, the dispersion becomes large, so the content of P ions is within the above range. In the optical glass 2, the preferable content of P ions is 30 to 55%, more preferably 40 to 50% in Cationic, and in the optical glass 3, 10 to 16% in mol%, more preferably 12 to 15%.
%.

Al (aluminum) ion is an essential component for imparting stability against devitrification of glass and optical characteristics of low refraction and low dispersion, and has an effect of increasing hardness of glass and improving workability. If the Al ions are less than the lower limit of the above content, the stability of the glass against devitrification deteriorates, and if it exceeds the upper limit, the refractive index becomes low,
The content of Al ions is within the above range. In the optical glass 2, a preferable Al ion content is 13 to 28%, more preferably 15 to 25% in Cationic, and in the optical glass 3, 3 to 10% in mol%, more preferably 4 to 8%. %.

Ba (barium) ion is an essential component for improving the stability against devitrification of glass and the refractive index, but if added too much, the dispersion becomes large. So Ba
The content of ions is within the above range. The preferable Ba ion content in the optical glass 2 is 15 to 42%, more preferably 25 to 35%, and further preferably 27 to 33% in terms of cationic ratio. In the optical glass 3,
The mol% is 5 to 12%, and more preferably 8 to 12%.

Ca (calcium) ions and Sr (strontium) ions are optional components that reduce the influence of Ba ions on the specific gravity, and if added too much, it becomes difficult to obtain a desired optical constant. Therefore, Sr ions and C
The content of a-ions is in the above range. The preferred Sr ion content in the optical glass 2 is 0 to 15%, more preferably 0 to 3% in terms of cationic, and in the optical glass 3, 0 to 6% in mol%, more preferably 0 to 2%. %. The preferable Ca ion content in the optical glass 2 is from 0 to 10 in terms of cationic.
%, More preferably 0 to 2%, in the optical glass 3,
The mol% is 0 to 3%, more preferably 0 to 1%.

Y (yttrium) ions and La (lanthanum) ions are optional components that contribute to the stability of the glass against devitrification, the refractive index and the chemical durability, and the glass hardness, but if added too much, the specific gravity will increase. Will be higher. Therefore, the contents of Y ions and La ions are each in the above range. In the optical glass 2, the preferable content of Y ion and La ion is 0-8% of Y ion and 0 to 8% of La ion in Cationic%.
2%, more preferably 0 to 5% Y ions and 0 to 1% La ions, and in the optical glass 3, Y in mol%.
Ions are 0 to 3%, La ions are 0 to 2%, more preferably Y ions are 0 to 2%, and La ions are 0 to 1%.

F (fluorine) ions are an essential component that gives a glass exhibiting anomalous partial dispersion characteristics, and in the optical glass 3, if the F ions are less than the lower limit of the above content, sufficient anomalous partial dispersion characteristics will not be exhibited. If the content exceeds the above range, the stability against devitrification deteriorates. Therefore, the content of F ions is within the above range. The preferred F ion content in the optical glass 3 is 20 to 40 mol%.
%, More preferably 22 to 38%, even more preferably 2
It is 5 to 30%. Also in the optical glass 2, the F ion content is 25 in terms of anionic% for the above reason.
-60% is preferable, 30-55% is more preferable, and 32-40% is further preferable.

O (oxygen) ion is an essential component for the cationic component to form an oxide, and its content is automatically controlled within the above range depending on the composition of the cationic component and the amount of F ion. Depends on. The content of O ions in the optical glass 2 is preferably 37 to 78% as anionic%, more preferably 45 to 70%, and further preferably 55 to 68%. The preferred O ion content in the optical glass 3 is 30 to 48 mol%.
%, More preferably 38 to 48%, even more preferably 4
0 to 48%.

In the optical glass 2 of the present invention, the preferable composition is P30-55%, Al13-28%, Ba1 as the cationic component in the cationic% display.
5 to 42%, Sr 0 to 15%, Ca 0 to 10%, Y
0 to 8% and La 0 to 2%, and oxygen and fluorine as an anionic component.
A more preferable composition is P40 to 50%, Al 15 to 25 in terms of cationic% as a cationic component.
%, Ba 25-35%, Sr 0-3%, Ca 0-
2%, Y 0 to 5% and La 0 to 1%, and oxygen and fluorine as an anionic component. Among them, those containing Ba 27 to 33% are more preferable.

On the other hand, in the optical glass 3 of the present invention, the preferable composition is P10 to 16%, Al in terms of mol%.
3-10%, Ba 5-12%, Sr 0-6%, Ca
0-3%, Y 0-3%, La 0-2%, O 30-
48% and F 20 to 40%, and a more preferable composition is P 12 to 15%, Al 4 to 8%, and Ba 8.
-12%, Sr 0-2%, Ca 0-1%, Y 0-
2%, La 0 to 1%, O 38 to 48% and F 2
2-38%. Above all, O 40-48%, F 25
Even more preferred are those containing ~ 30%.

In the optical glasses 2 and 3, as optional components, Mg, Zn, Li, Na, K, La and G are used.
d, etc. can be included. However, since Gd is a component that increases the specific gravity of glass, it is preferable to control it to less than 1.5 mol%. In addition, P
It is preferable to exclude toxic components such as b, As and Te, and also to exclude Sn.

The optical glasses 2 and 3 of the present invention can be made to have a low specific gravity of less than 4.1, and the optical index and refractive index (nd) and Abbe number (νd) are within the above ranges. It has a constant number and exhibits anomalous partial dispersion characteristics in such a low refractive index and low dispersion region. Optical glass 1
Particularly preferred glasses in any of 3 to 3 are P, Al, Ba,
It is composed of Sr, Ca, Y, La, O and F.

Optical glass of the present invention (optical glasses 1 to 3)
Is transparent because of its high transmittance in the visible range. The optical glass of the present invention exhibits anomalous partial dispersion, has a small specific gravity, a large hardness, and is excellent in workability (grinding workability, polishing workability, etc.). It is suitable as a material for lenses for use.

The fact that the optical glass of the present invention has anomalous partial dispersion characteristics can be confirmed as follows. Refractive index ng at wavelength 435.84 nm,
Refractive index nF at wavelength 486.13 nm, wavelength 6
The refractive index nc at 56.27 nm was measured, and the partial dispersion ratio PgF on the short wavelength side = (ng-nF) / (nF-n
Find c). The graph of Abbe number νd on the X axis and PgF (both axes on the linear scale) on the Y axis shows νd of the glass.
And PgF are plotted. Also, νd = 60.49, P
The point of gF = 0.5393 and vd = 36.30, PgF =
If the plot deviates from the straight line passing through the point of 0.5829, it means that it has an abnormal partial dispersion characteristic.

In order to obtain a glass having low specific gravity and excellent devitrification resistance among the optical glasses 1 to 3, it is desirable to set the partial dispersion ratio PgF to 0.53 to 0.56, and 0.535 to 0.535.
It is more desirable to set it to 0.555.

Next, the method for molding the optical glass of the present invention will be described. As a forming method, there can be used a method in which molten glass is poured into a mold, cooled, and then the cooled glass is subjected to processing such as cutting, grinding and polishing to obtain a desired shape and a desired surface. Among them, the molten glass continuously discharged from the outflow pipe is poured into a mold having one end opened, drawn out from the open end of the mold while being cooled, and a method for molding a long glass plate having a constant width and a constant thickness. Are suitable. It is also possible to cut the glass plate produced by this method in the vertical and horizontal directions to produce glass pieces called cut pieces, and barrel polish these cut pieces to obtain a glass lump of a certain weight. These glass gobs can be used as a glass material for press molding. This press-molding glass material is softened by reheating and press-molded using a press mold to produce a press-molded product such as a lens blank (an intermediate product for obtaining a lens). An optical component such as a lens can be created by subjecting this press-formed product to grinding and polishing. The optical parts include
If necessary, an optical thin film such as an antireflection film may be formed.

The optical component of the present invention thus obtained is made of glass having a low specific gravity and anomalous partial dispersion characteristics, and is a lightweight chromatic aberration correcting optical component, such as a lightweight chromatic aberration correcting lens. Can be provided.

[0031]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. Examples 1 to 14 and Comparative Example 1 The glass composition is the cationic% shown in Table 1, and Table 2
Each glass raw material component was prepared so as to have a mol% as shown in (1), melted, clarified, stirred, and cast into a mold to prepare an optical glass. The specific gravity, refractive index (nd) of this glass,
Abbe number (νd) and abnormal partial dispersion characteristics were measured according to the methods described below. The results are shown in Table 3. (1) It was measured by the Archimedes method using specific gravity distilled water. (2) Refractive index (nd) and Abbe's number (νd) The optical glass obtained by setting the slow cooling rate to -30 ° C / h was measured. (3) Anomalous partial dispersion characteristics From the optical refractive indexes ng, nF, and nc of (2) above, PgF
Was confirmed, and the values of PgF and νd were plotted and confirmed on the PgF-νd graph.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

[Table 3]

As shown in Table 3, each of the optical glasses obtained in the examples has an nd of 1.54 or more and less than 1.60,
νd is 70 to 80, specific gravity is less than 4.1, and anomalous partial dispersion characteristics are provided. The results of plotting the partial dispersion ratio (PgF) and the Abbe's number (νd) of each glass of Examples 1 to 14 are shown in FIG. 1 (the numbers in the figure are those of Example N).
o. Is). It is on the upper side of the straight line along with the plots of the glass of each example, and it can be clearly seen that the glass is an abnormal partially dispersed glass.

Example 15 A molten glass was prepared from the compounding raw materials having the glass compositions of Examples 1 to 14, continuously cast into a mold having one end open, and while cooling, a glass plate having a constant width and a constant thickness. Was drawn from the open end of the mold at a constant speed, and the drawn glass plate was annealed. After annealing, the glass plate cooled to room temperature was cut into a certain size to prepare a rectangular parallelepiped cut piece. The edges of these cut pieces were removed by barrel polishing to obtain a glass material for press molding having a certain weight. This glass material for press molding,
It was softened by reheating in the atmosphere, and press-molded with a press mold having an upper mold and a lower mold to produce a lens blank. These lens blanks were annealed to remove distortion, and then ground and polished to give lenses. An antireflection film may be formed on the surfaces of these lenses, if necessary. These lenses can be used as chromatic aberration correction lenses. As described above, by using the optical glass of Examples 1 to 14, it is possible to reduce the weight by 10% as compared with the case of using the conventional glass.

[0037]

According to the present invention, the refractive index (nd) is 1.
54 or more and less than 1.60, Abbe number (νd) is 70 to 80
It is possible to obtain an optical glass having a low specific gravity while having an optical constant of 1. By using the optical glass of the present invention, it is possible to reduce the weight of an optical component, and thus it is possible to reduce the total weight of an optical device incorporating this component, for example, a camera lens, particularly a telephoto lens. Various performances such as portability and operability of the device can be improved.

[Brief description of drawings]

FIG. 1 is a partial dispersion ratio (P of each glass of Examples 1 to 14).
It is a figure which shows the result of having plotted gF) and Abbe's number ((nu) d).

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Claims (6)

[Claims] 1. A compound containing P, Al and Ba as a cationic component and oxygen and fluorine as an anionic component, having a refractive index (nd) of 1.54 or more and less than 1.60 and an Abbe number (νd) of 70 to 80. And specific gravity is 4.1
Optical glass characterized by being less than. 2. Sr, Ca, as a cationic component,
The optical glass according to claim 1, containing at least one selected from Y and La. 3. As a cationic component, P is 20 to 60%, Al is 10 to 30%, and B is expressed as a cationic%.
a is 10 to 50%, Sr is 0 to 25%, Ca is 0 to 20%
%, Y of 0 to 15% and La of 0 to 15%, and a glass containing oxygen and fluorine as an anionic component and having a refractive index (nd) of 1.54 or more and 1.6 or more.
An optical glass having an Abbe number (νd) of 70 to 80, which is less than 0. 4. In mol% display, P is 5 to 20%, Al is 1 to 15%, Ba is 1 to 18%, Sr is 0 to 10%, and C.
A glass containing 0 to 10% of a, 0 to 5% of Y, 0 to 5% of La, 20 to 55% of O and 18 to 48% of F, and having a refractive index (nd) of 1.54 or more. An optical glass having an Abbe number (νd) of 70 to 80, which is less than 1.60. 5. The optical glass according to claim 3, which has a specific gravity of less than 4.1. 6. An optical component made of the optical glass according to claim 1.