JP2019043814A - Glass for near-infrared absorption filter - Google Patents

Abstract

To provide a glass for a near-infrared absorption filter, which has good transmission characteristics for visible light and excellent polishing processability.SOLUTION: The glass for a near-infrared absorption filter has a composition comprising, in terms of mass%, at least POby 65.0% or more and 75.0% or less, AlOby 10.0% or more and 16.0% or less, BOby 1.5% or more and 7.0% or less, LiO by 1.0% or more and 3.5% or less, KO by 2.0% or more and 10.0% or less, RO by 7.0% or more and 13.5% or less, MgO by 0.5% or more and 6.0% or less, and RO by 0.5% or more and 6.0% or less, contains CuO by 4.5% or more and 9.0% or less in an external ratio, satisfies 0.78≤x≤3.00, 0.74≤y≤2.29 and 0.12≤z≤0.24, where x is RO/CuO, y is AlO/RO and z is AlO/(PO+BO).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a near-infrared absorption filter glass.

A solid imaging element is mounted on a color imaging device such as a camera or a smartphone. The spectral sensitivity of this solid-state imaging element covers a wide range from the visible range to the near infrared range, and the sensitivity is higher in the infrared range than in the visible range. Therefore, in order to make the solid-state imaging device function effectively, it is necessary to transmit light in the visible region, absorb light in the near infrared region (wavelength of about 800 to 900 nm), and correct to normal sensitivity. A near-infrared absorption filter is often used as one of the optical components that achieve such sensitivity correction.
In addition, with the recent increase in demand for downsizing and weight reduction of photographic equipment, further reduction in thickness is required for the near-infrared absorption filter.

  Here, the near-infrared absorption filter can be made of glass, and as the spectral characteristics that the glass for the near-infrared absorption filter should have, the absorption characteristic of light having a wavelength of 800 nm or more is high, and the wavelength is 400 to 700 nm. It is mentioned that the transmission characteristic of the light of a wavelength is high.

  As a glass having such spectral characteristics, for example, Patent Documents 1 to 3 include a near-infrared absorption filter that is excellent in weather resistance and satisfies a predetermined transmittance characteristic by containing CuO in a fluorophosphate glass. It is disclosed that a glass capable of producing is obtained.

In the glass disclosed in the above document, the light absorption property in the near infrared region is enhanced by controlling the valence of copper ions derived from CuO to Cu ²⁺ . Further, when further reducing the thickness, the light absorption characteristics in the near infrared region can be satisfactorily maintained by increasing the content of CuO per unit volume, and hence Cu ²⁺ .

Japanese Patent Laid-Open No. 01-219037 Japanese Patent Laid-Open No. 03-083833 Japanese Patent Laid-Open No. 03-083835

  However, the fluorophosphate glass used in the technique disclosed in the above document tends to be easily scraped by a polishing process or the like, and the fine adjustment of the thickness is difficult, in other words, the problem of poor polishing processability. there were. This problem causes a decrease in yield, and becomes particularly serious when responding to demands for further thinning.

  In addition, fluorophosphate glass is generally not suitable for mass production because fluorine volatilizes during production and the composition is not stable and the yield is low. There is also the problem of increasing the costs involved.

  On the other hand, as a countermeasure to the above-described problem relating to the polishing processability, it is conceivable to use phosphate glass instead of fluorophosphate glass in the technique disclosed in the above-mentioned document.

However, when phosphate glass is simply used instead of fluorophosphate glass, the melting temperature increases, so that the visible light transmission characteristics deteriorate and Cu ²⁺ is easily reduced to Cu ^+. The light absorption characteristics in the near infrared region deteriorate. Such deterioration of the light absorption characteristics in the near infrared region becomes more conspicuous when the content of CuO is increased to cope with further thinning.

  This invention is made | formed in view of said viewpoint, and it aims at providing the glass for near-infrared absorption filters which is excellent in the permeation | transmission characteristic of visible light, and is excellent in polishing workability.

Means for solving the above problems are as follows. That is, the near infrared absorption filter glass of the present invention is
% By mass
P ₂ O ₅ : 65.0% to 75.0% Al ₂ O ₃ : 10.0% to 16.0% B ₂ O ₃ : 1.5% to 7.0% R ¹ ₂ O: 7.0% to 13.5% Li ₂ O: 1.0% to 3.5% Na ₂ O: 0% to 4.0% K ₂ O: 2.0% to 10.0% Cs ₂ O: 0% to 3.0% R ² O: 0.5% to 6.0% CaO: 0% to 2.0% SrO: 0% to 3.0% BaO: 0% 4.0% or less ZnO: 0% or more and 3.0% or less MgO: 0.5% or more and 6.0% or less Nb ₂ O ₅ : 0% or more and 5.0% or less (provided that R ¹ ₂ O is li _{2 O,} Na 2 O, shows the sum of _{K 2} O and Cs ₂ ^O, R ₂ O is, CaO, SrO, BaO, the composition of indicating the sum of ZnO and MgO) And,
CuO is included on the outer surface at 4.5% or more and 9.0% or less, and
When R ¹ ₂ O / CuO is x, Al ₂ O ₃ / R ¹ ₂ O is y, and Al ₂ O ₃ / (P ₂ O ₅ + B ₂ O ₃ ) is z, the following formulas (1) to (1) 3):
0.78 ≦ x ≦ 3.00 (1)
0.74 ≦ y ≦ 2.29 (2)
0.12 ≦ z ≦ 0.24 (3)
It is characterized by satisfying. Such near-infrared absorption filter glass has excellent visible light transmission characteristics and excellent polishing processability.

  It is preferable that the near-infrared absorption filter glass of the present invention does not contain fluorine.

  The near infrared absorption filter glass of the present invention preferably has a degree of wear of 200 or more and 350 or less measured in accordance with the Japan Optical Glass Industry Association Standard “JOGIS10-1994”.

  The near infrared absorption filter glass of the present invention preferably has a thickness of 0.15 mm to 0.30 mm.

  According to the present invention, it is possible to provide a glass for a near-infrared absorption filter having good visible light transmission characteristics and excellent polishing workability.

It is a simulation data of the spectral transmittance with respect to the light of each wavelength about the glass sample of Example 2 and Comparative Example 2.

(Glass for near infrared absorption filter)
The glass for near-infrared absorption filters of one embodiment of the present invention (hereinafter sometimes referred to as “glass of this embodiment”) will be specifically described. The glass of the present embodiment is mass%,
P ₂ O ₅ : 65.0% to 75.0% Al ₂ O ₃ : 10.0% to 16.0% B ₂ O ₃ : 1.5% to 7.0% R ¹ ₂ O: 7.0% to 13.5% Li ₂ O: 1.0% to 3.5% Na ₂ O: 0% to 4.0% K ₂ O: 2.0% to 10.0% Cs ₂ O: 0% to 3.0% R ² O: 0.5% to 6.0% CaO: 0% to 2.0% SrO: 0% to 3.0% BaO: 0% 4.0% or less ZnO: 0% or more and 3.0% or less MgO: 0.5% or more and 6.0% or less Nb ₂ O ₅ : 0% or more and 5.0% or less (provided that R ¹ ₂ O is li _{2 O,} Na 2 O, shows the sum of _{K 2} O and Cs ₂ ^O, R ₂ O is, CaO, SrO, BaO, the composition of indicating the sum of ZnO and MgO) And,
The first feature is that CuO is included in an external ratio of 4.5% to 9.0%.

  Moreover, the glass of this embodiment may contain other components (after-mentioned) other than the component mentioned above. However, the glass of the present embodiment has a composition composed of only the above-described components from the viewpoint of more reliably improving the visible light transmission characteristics and polishing processability, and CuO is divided by 4.5% or more and 9. It is preferable to contain 0% or less.

  Hereinafter, the reason why the ratio of each component is limited to the above range in the glass of the present embodiment will be described. The “%” display means mass% unless otherwise specified, and the ratio of components other than the essential component CuO is calculated without considering the CuO.

[P ₂ O ₅ ]
P ₂ O ₅ is a main component in the glass of the present embodiment. When the proportion of P ₂ O _{5 in} the glass is less than 65.0%, it becomes difficult to form the glass. On the other hand, when the proportion of P ₂ O ₅ in the glass exceeds 75.0%, the degree of wear increases remarkably and the polishing processability deteriorates. Therefore, the ratio of P ₂ O ₅ in the glass of this embodiment is set to 65.0% or more and 75.0% or less. From the same viewpoint, the proportion of P ₂ O ₅ in the glass of the present embodiment is preferably 68.0% or more, more preferably 70.0% or less, and 69.5% or less. It is more preferable.

[Al ₂ O ₃ ]
Al ₂ O ₃ is an essential component in the glass of the present embodiment, and is a component that can reduce the degree of wear. When the proportion of Al ₂ O _{3 in} the glass is less than 10.0%, the effect of reducing the degree of wear is not sufficient, and the polishing processability cannot be improved. On the other hand, if the ratio of Al ₂ O ₃ in the glass exceeds 16.0%, the melting temperature rises, the visible light transmission characteristics deteriorate, and the stability of the melt during melting deteriorates. It becomes difficult. Therefore, the ratio of Al ₂ O ₃ in the glass of this embodiment is set to 10.0% or more and 16.0% or less. From the same viewpoint, the proportion of Al ₂ O ₃ in the glass of the present embodiment is preferably 11.0% or more, more preferably 12.0% or more, and 15.0% or less. It is preferable that it is 14.0% or less.

[B ₂ O ₃ ]
B ₂ O ₃ is an essential component in the glass of this embodiment and is a component that forms a network structure of glass. If the proportion of B ₂ O _{3 in} the glass is less than 1.5%, it becomes difficult to form the glass. On the other hand, if the proportion of B ₂ O ₃ in the glass exceeds 7.0%, the degree of wear increases and the polishing processability deteriorates. Therefore, the ratio of B ₂ O ₃ in the glass of the present embodiment is set to 1.5% to 7.0%. From the same viewpoint, the ratio of B ₂ O ₃ in the glass of the present embodiment is preferably 2.0% or more, more preferably 3.0% or more, and 6.5% or less. Preferably, it is preferably 5.5% or less.

[Li ₂ O]
Li ₂ O is an essential component in the glass of this embodiment, and is a component that can effectively lower the melting temperature of the glass. If the proportion of Li ₂ O in the glass is less than 1.0%, the effect of lowering the melting temperature of the glass is not sufficient. On the other hand, when the proportion of Li ₂ O in the glass exceeds 3.5%, the degree of wear increases and the polishing processability deteriorates. Therefore, the ratio of Li ₂ O in the glass of the present embodiment is set to 1.0% or more and 3.5% or less. From the same viewpoint, the ratio of Li ₂ O in the glass of the present embodiment is preferably 2.5% or less, and more preferably 1.75% or less.

[Na ₂ O]
Na ₂ O is a component that can lower the melting temperature of the glass in the glass of this embodiment. When the ratio of Na ₂ O in the glass exceeds 4.0%, the degree of wear increases and the polishing processability deteriorates. Therefore, the ratio of Na ₂ O in the glass of the present embodiment is set to 0% to 4.0%. From the same viewpoint, the ratio of Na ₂ O in the glass of the present embodiment is preferably 1.5% or less, and more preferably 1.0% or less. From the viewpoint of reducing further the melting temperature of the glass, the proportion of Na 2 _O in the glass of the present embodiment is preferably 0.4% or more.

[K ₂ O]
K ₂ O is an essential component in the glass of this embodiment, and is a component that can lower the melting temperature of the glass. If the ratio of K ₂ O in the glass is less than 2.0%, the effect of lowering the melting temperature of the glass is not sufficient. On the other hand, when the proportion of K ₂ O in the glass exceeds 10.0%, the degree of wear increases and the polishing processability deteriorates. Therefore, the ratio of K ₂ O in the glass of this embodiment is set to 2.0% or more and 10.0% or less. From the same viewpoint, the proportion of K ₂ O in the glass of the present embodiment is preferably 5.0% or more, more preferably 9.0% or less, and 7.0% or less. Is more preferable.

[Cs ₂ O]
Cs ₂ O is a component that can lower the melting temperature of the glass in the glass of this embodiment. When the ratio of Cs ₂ O in the glass exceeds 3.0%, the degree of wear increases and the polishing processability deteriorates. Therefore, the ratio of Cs ₂ O in the glass of this embodiment is set to 0% or more and 3.0% or less. From the same viewpoint, the proportion of Cs ₂ O in the glass of this embodiment is preferably 1.5% or less, and more preferably 1.0% or less. Moreover, from the viewpoint of further reducing the melting temperature of the glass, the Cs ₂ O ratio in the glass of the present embodiment is preferably 0.3% or more, and more preferably 0.4% or more.

[R ¹ ₂ O (Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O)]
Here, in the glass of this embodiment, the ratio of R ¹ ₂ O indicating the total of Li ₂ O, Na ₂ O, K ₂ O, and Cs ₂ O was set to 7.0% or more and 13.5% or less. . This is because the melting temperature of the glass cannot be sufficiently lowered when the ratio of R ¹ ₂ O in the glass is less than 7.0%. Moreover, if the ratio of R ¹ ₂ O in the glass exceeds 13.5%, the degree of wear increases and the polishing processability deteriorates. From the same viewpoint, the ratio of R ¹ ₂ O in the glass of this embodiment is preferably 8.0% or more, and more preferably 12.0% or less.

[CaO]
CaO is a component that can reduce the degree of wear in the glass of the present embodiment. When the proportion of CaO in the glass exceeds 2.0%, the melting temperature rises and the visible light transmission characteristics deteriorate. Therefore, the CaO ratio in the glass of this embodiment is set to 0% or more and 2.0% or less. From the same viewpoint, the CaO ratio in the glass of the present embodiment is preferably 1.0% or less. Further, from the viewpoint of further reducing the degree of wear, the CaO ratio in the glass of the present embodiment is preferably 0.5% or more.

[SrO]
SrO, like CaO, is a component that can reduce the degree of wear in the glass of this embodiment. If the SrO ratio in the glass exceeds 3.0%, the melting temperature rises and the visible light transmission characteristics deteriorate. Therefore, the ratio of SrO in the glass of this embodiment is set to 0% or more and 3.0% or less. From the same viewpoint, the SrO ratio in the glass of the present embodiment is preferably 1.0% or less. Further, from the viewpoint of further reducing the degree of wear, the ratio of SrO in the glass of the present embodiment is preferably 0.5% or more.

[BaO]
BaO, like CaO and SrO, is a component that can reduce the degree of wear in the glass of this embodiment. If the proportion of BaO in the glass exceeds 4.0%, the melting temperature increases and the visible light transmission characteristics deteriorate. Therefore, the ratio of BaO in the glass of the present embodiment is set to 0% to 4.0%. From the same viewpoint, the ratio of BaO in the glass of the present embodiment is preferably 1.0% or less. Further, from the viewpoint of further reducing the degree of wear, the ratio of BaO in the glass of the present embodiment is preferably 0.5% or more.

[ZnO]
ZnO is a component that can lower the degree of wear in the glass of this embodiment, similarly to CaO, SrO, and BaO. When the proportion of ZnO in the glass exceeds 3.0%, the melting temperature increases and the visible light transmission characteristics deteriorate. Therefore, the ratio of ZnO in the glass of this embodiment is set to 0% or more and 3.0% or less. From the same viewpoint, the ZnO ratio in the glass of the present embodiment is preferably 1.0% or less. Further, from the viewpoint of further reducing the degree of wear, the proportion of ZnO in the glass of the present embodiment is preferably 0.5% or more.

[MgO]
MgO is an essential component in the glass of the present embodiment, and is a component that can reduce the degree of wear, like CaO, SrO, BaO, and ZnO. When the proportion of MgO in the glass is less than 0.5%, the effect of reducing the degree of wear is not sufficient, and the polishing processability cannot be improved. On the other hand, if the MgO ratio in the glass exceeds 6.0%, the melting temperature rises, the visible light transmission characteristics deteriorate, and the stability of the melt during melting deteriorates, making mass production difficult. . Therefore, the MgO ratio in the glass of this embodiment is set to 0.5% or more and 6.0% or less. From the same viewpoint, the MgO ratio in the glass of the present embodiment is preferably 2.0% or more, and is preferably 4.5% or less.

[R ² O (CaO + SrO + BaO + ZnO + MgO)]
Here, in the glass of this embodiment, the ratio of R ² O indicating the sum of CaO, SrO, BaO, ZnO, and MgO was set to 0.5% to 6.0%. This is because if the ratio of R ² O in the glass is less than 0.5%, the effect of reducing the degree of wear is not sufficient, and the polishing processability cannot be improved. Moreover, when the ratio of R ² O in the glass exceeds 6.0%, the melting temperature increases, and the visible light transmission characteristics deteriorate. From the same viewpoint, the ratio of R ² O in the glass of the present embodiment is preferably 2.0% or more, more preferably 5.0% or less, and 4.5% or less. Is more preferable.

[Nb ₂ O ₅ ]
Nb ₂ O ₅ is a component that can improve the stability of the melt during melting in the glass of the present embodiment. When the ratio of Nb ₂ O _{5 in} the glass exceeds 5.0%, the melting temperature increases and the visible light transmission characteristics deteriorate. Therefore, the ratio of Nb ₂ O ₅ in the glass of this embodiment is set to 0% or more and 5.0% or less. From the same viewpoint, the ratio of Nb ₂ O ₅ in the glass of the present embodiment is preferably 2.5% or less. Further, from the viewpoint of further improving the stability of the melt during melting, the ratio of Nb ₂ O ₅ in the glass of the present embodiment is preferably 0.25% or more.

[CuO]
CuO is a component capable of imparting near-infrared absorption characteristics to glass, and the ratio can be appropriately selected depending on the thickness and spectral characteristics of the target near-infrared absorption filter. However, if the glass contains only less than 4.5% of CuO, the effect of absorbing near-infrared light is not sufficient. On the other hand, if CuO is included in the glass exceeding 9.0% on an external basis, the melting temperature rises and the visible light transmission characteristics deteriorate. For this reason, the glass of the present embodiment is required to contain CuO in an external ratio of 4.5% to 9.0%. From the same point of view, the CuO ratio (external division) in the glass of the present embodiment is preferably 5.9% or more, and preferably 7.8% or less.

[Other ingredients]
The glass of the present embodiment may optionally contain other components other than the components described above, unless departing from the object of the present invention. Examples of other components include Fe ₂ O ₃ , TiO ₂ , Cr ₂ O ₃ , MnO, Co ₃ O ₄ , NiO, SnO ₂ , Nd ₂ O ₃ , Yb ₂ O _{3 and the} like. However, it is preferable not to include other components because they can be inevitable impurities in the glass of the present embodiment.
In particular, the glass of this embodiment preferably does not contain fluorine. By not containing fluorine, deterioration of polishing processability can be suppressed and high mechanical strength can be maintained.

In the glass of the present _{embodiment, Al 2 O 3, B 2} O 3 in accordance with the ^{_{above, R 1 2 O, R 2}} O, by achieve an appropriate content of such CuO, reduction and polishing of the melting temperature Can be improved. However, in practice, such optimization alone may not provide sufficient melt stability during melting. Therefore, in the glass of this embodiment, the mass ratio represented by R ¹ ₂ O / CuO is x, the mass ratio represented by Al ₂ O ₃ / R ¹ ₂ O is y, and Al ₂ O ₃ / (P ₂ O ₅ When the mass ratio represented by + B ₂ O ₃ is z, the following formulas (1) to (3):
0.78 ≦ x ≦ 3.00 (1)
0.74 ≦ y ≦ 2.29 (2)
0.12 ≦ z ≦ 0.24 (3)
The second feature is to satisfy the above. By satisfying these equations, the glass of the present embodiment can realize improved visible light transmission characteristics and polishing processability more reliably than in the prior art.

Here, when the mass ratio (x) indicated by R ¹ ₂ O / CuO in the glass is less than 0.78, the amount of CuO increases and the amount of R ¹ ₂ O decreases, so the melting temperature increases. In addition, the visible light transmission characteristics deteriorate. Further, when the mass ratio (x) exceeds 3.00, the amount of R 1 ² _O increases, the degree of wear is increased, polishing is deteriorated.

Further, the mass ratio represented by ^{_{Al 2 O 3 / R 1 2}} O in the glass (y) is less than ^0.74, the more the amount of ^R _{1 2} O, the amount of _Al 2 _{O 3} is less The degree of wear increases and the polishing processability deteriorates. On the other hand, if the mass ratio (y) exceeds 2.29, the amount of Al ₂ O ₃ increases and the amount of R ¹ ₂ O decreases, so the stability of the melt during melting deteriorates and mass production It becomes difficult.

When the mass ratio represented by _{Al 2 O 3 / (P 2} O 5 + B 2 O 3) in the glass (z) is less than _0.12, many total amount of P 2 _{O 5} and _B 2 _{O 3} Thus, since the amount of Al ₂ O ₃ decreases, the degree of wear increases and the polishing processability of the glass decreases. Further, when the mass ratio (z) exceeds 0.24, the amount of Al ₂ O ₃ increases, and the total amount of P ₂ O ₅ and B ₂ O ₃ decreases, so that the stability of the melt during melting is reduced. The quality deteriorates and mass production becomes difficult.

Since the glass of this embodiment has the first and second characteristics described above, it is at least excellent in polishing processability. In this regard, the glass of the present embodiment preferably has a degree of wear measured in accordance with Japan Optical Glass Industry Association Standard “JOGIS10-1994” of 200 or more and 350 or less.
Moreover, since the glass of this embodiment is excellent in polishing workability as mentioned above, it can achieve thickness reduction. Specifically, the glass of this embodiment can have a thickness of 0.15 mm to 0.30 mm while having good near-infrared light absorption characteristics and visible light transmission characteristics.

The glass of this embodiment should just satisfy the requirements regarding the component mentioned above, About the manufacturing method, it can manufacture according to the conventional manufacturing method, without being specifically limited.
For example, first, as a raw material of each component that can be included in the glass of the present embodiment, normal compounds such as phosphoric acid compounds such as orthophosphoric acid, diphosphorus pentoxide, and metaphosphate, carbonate, nitrate, hydroxide, etc. Prepare general raw materials used for optical glass. Next, this raw material is put into a crucible made of platinum or the like and melted at a temperature of about 1000 to 1250 ° C. Then, the obtained melt is poured into a mold and annealed (strain removal) in the vicinity of the glass transition temperature, whereby a stable near-infrared absorption filter glass can be obtained.

  And since the glass of this embodiment efficiently absorbs light in the near infrared region (wavelength of about 800 to 1000 nm) and has high transmission characteristics with respect to light in the visible region, it is mainly used for cameras and smartphones. It can be used as a filter for sensitivity correction in a color photographing apparatus such as the above. In addition, the glass of the present embodiment can be used for a band-pass filter that absorbs infrared light and transmits only a specific wavelength during in-situ observation during processing using near-infrared laser light.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and the glass for near infrared absorption filters of this invention is demonstrated concretely, this invention is not limited to these Examples.

(Examples 1-24, Comparative Examples 1-23)
As a raw material of each component described in Tables 1-4, the corresponding metaphosphate, oxide, carbonate, nitrate, etc. are prepared, and the composition after vitrification is as shown in Tables 1-4. Were weighed and mixed to prepare a blended raw material. This prepared raw material was put into a platinum crucible and melted at a temperature of 1000 to 1350 ° C. for several hours to several tens of hours in an electric furnace. Then, after homogenization and clarification by stirring, the mixture was poured into a mold and subjected to strain removal to obtain a homogeneous glass.

(Comparative Examples 24-26)
As a raw material of each component described in Table 5, the corresponding metaphosphate, oxide, carbonate, nitrate, fluoride, etc. are prepared, and the composition after vitrification is as shown in Table 5 Weighed, mixed, and used as a blended raw material. This prepared raw material was put into a platinum crucible and melted in an electric furnace at a temperature of 800 to 900 ° C. for several hours to several tens of hours. Then, after homogenization and clarification by stirring, the mixture was poured into a mold and subjected to strain removal to obtain a homogeneous glass.

(Evaluation)
When glass was obtained according to the above, the melting temperature was measured and the stability of the melt was evaluated according to the procedure shown below, and the degree of wear was measured for the obtained glass according to the procedure shown below. These results are shown in Tables 1-5. Furthermore, the transmittance | permeability was measured about the glass of Example 2 and the comparative example 2 according to the procedure shown below.

<Melting temperature>
The melting temperature was set to a platinum crucible that had been set in an electric furnace in which the temperature was set, and after 1 hour had passed, a uniform liquid level (crystals were not precipitated and no film was formed) The temperature of the electric furnace when the state was observed.

<Stability of melt>
After the blended raw material was melted in an electric furnace, the entire platinum crucible was taken out of the furnace, and the time from when the melt was stirred until devitrification occurred was measured. Then, stability was evaluated according to the following criteria.
Less than 1 minute ... ×
1 minute to less than 2 minutes ... △
2 minutes or more and less than 3 minutes ... ○
More than 3 minutes ... ◎

<Degree of wear>
Using the obtained glass, the degree of wear was measured in accordance with the Japan Optical Glass Industry Association Standard “JOGIS10-1994 (Measurement Method of Abrasion Level of Optical Glass)”.

<Transmissivity>
The obtained glass was processed into a length of 20 mm × width of 20 mm × thickness of 0.15 to 0.30 mm, and both surfaces were optically polished to obtain a sample. Then, two glass samples having different thicknesses were measured, and the internal transmittance was calculated by simulation. FIG. 1 shows the spectral transmittance simulation data when the glass samples of Example 2 and Comparative Example 2 were used.

  As can be seen from Tables 1 and 2, since the glasses according to Examples 1 to 24 can be melted at a relatively low temperature (1250 ° C. or lower), deterioration of the transmittance of visible light is suppressed. Also, from Tables 1 and 2, the glasses according to Examples 1 to 24 have excellent melt processability because the melt stability is good and the degree of wear is relatively small (200 to 350). I understand.

  On the other hand, it can be seen that the glasses according to Comparative Examples 1 to 26 shown in Tables 3 to 5 are not good in at least one of the melting temperature, the stability of the melt, and the degree of wear. This result is considered as follows.

Since the glass according to Comparative Example 1 has a large amount of P ₂ O ₅ , the degree of wear is large.
Since the glass according to Comparative Example 2 has a small amount of P ₂ O ₅ , the melting temperature is high and the melt stability is also poor. When attention is paid to FIG. 1, it can be seen that in Comparative Example 2, the light transmission characteristics in the visible region (in particular, the wavelength of about 400 to 450 nm) are worse than those in Example 2 where the melting temperature is low.
Glass according to Comparative Example 3, since the amount of Al ₂ O ₃ is too large, melting temperature is high, poor stability of the melt.
The glass according to Comparative Example 4 has a high degree of wear because the amount of Al ₂ O ₃ is too small.
The glass according to Comparative Example 5 has a high degree of wear because the amount of B ₂ O ₃ is too large.
The glass according to Comparative Example 6 has a poor melt stability because the amount of B ₂ O ₃ is too small.
The glass according to Comparative Example 7 has a high degree of wear because the amount of Li ₂ O is too large.
Glass according to Comparative Example 8, since the amount of Li 2 _O is too small, melting temperature is high, poor stability of the melt.
The glass according to Comparative Example 9 has a high degree of wear because the amount of K ₂ O is too large.
The glass according to Comparative Example 10 has a high melting temperature because the amount of K ₂ O is too small.
Since the glass which concerns on the comparative example 11 has too much amount of MgO, melting temperature is high and stability of a melt is not good.
The glass according to Comparative Example 12 has a high degree of wear because the amount of MgO is too small.
The glass according to Comparative Example 13 has a high melting temperature because the amount of CuO is too large.
The glass according to Comparative Example 14 has a high degree of wear because the amount of R ¹ ₂ O is too large.
Glass according to Comparative Example 15, since the amount of R 1 ² _O is too small, melting temperature is high.
The glass according to Comparative Example 16 has a high melting temperature because the amount of R ² O is too large.
The glass according to Comparative Example 17 has a high degree of wear because the amount of R ² O is too small.
Since the glass according to Comparative Example 18 has too many values of x (exceeds 3.0), the degree of wear is high.
The glass according to Comparative Example 19 has a high melting temperature because the value of x is too small (less than 0.78).
Since the glass according to Comparative Example 20 has too many values of y (exceeds 2.29), the melting temperature is high and the melt stability is poor.
The glass according to Comparative Example 21 has a high degree of wear because the value of y is too small (less than 0.74).
Since the glass which concerns on the comparative example 22 has too much value of z (exceeds 0.24), melting temperature is high and stability of a melt is bad.
The glass according to Comparative Example 23 has a high degree of wear because the value of z is too small (less than 0.12).
The glasses according to Comparative Examples 24-26 have a very high degree of wear because the amount of Al ₂ O ₃ is too small and a relatively large amount of fluorine is contained.

  According to the present invention, it is possible to provide a glass for a near-infrared absorption filter having good visible light transmission characteristics and excellent polishing workability.

Claims (4)

% By mass
P ₂ O ₅ : 65.0% to 75.0% Al ₂ O ₃ : 10.0% to 16.0% B ₂ O ₃ : 1.5% to 7.0% R ¹ ₂ O: 7.0% to 13.5% Li ₂ O: 1.0% to 3.5% Na ₂ O: 0% to 4.0% K ₂ O: 2.0% to 10.0% Cs ₂ O: 0% to 3.0% R ² O: 0.5% to 6.0% CaO: 0% to 2.0% SrO: 0% to 3.0% BaO: 0% 4.0% or less ZnO: 0% or more and 3.0% or less MgO: 0.5% or more and 6.0% or less Nb ₂ O ₅ : 0% or more and 5.0% or less (provided that R ¹ ₂ O is li _{2 O,} Na 2 O, shows the sum of _{K 2} O and Cs ₂ ^O, R ₂ O is, CaO, SrO, BaO, the composition of indicating the sum of ZnO and MgO) And,
CuO is included on the outer surface at 4.5% or more and 9.0% or less, and
When R ¹ ₂ O / CuO is x, Al ₂ O ₃ / R ¹ ₂ O is y, and Al ₂ O ₃ / (P ₂ O ₅ + B ₂ O ₃ ) is z, the following formulas (1) to (1) 3):
0.78 ≦ x ≦ 3.00 (1)
0.74 ≦ y ≦ 2.29 (2)
0.12 ≦ z ≦ 0.24 (3)
The glass for near-infrared absorption filters characterized by satisfy | filling.   The glass for near-infrared absorption filters according to claim 1 which does not contain fluorine.   The near-infrared absorption filter glass according to claim 1 or 2, wherein the abrasion degree measured in accordance with the Japan Optical Glass Industry Association Standard "JOGIS10-1994" is 200 or more and 350 or less.   The near-infrared absorption filter glass according to any one of claims 1 to 3, wherein the thickness is 0.15 mm to 0.30 mm.

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