JP2002265234A - Crystallized glass for optical filter substrate and optical filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide crystallizing glass which can be used for a substrate for a bandpass filter of wavelength splitting multiplexed optical communication system, is high in Young's modulus and enables film forming under the same conditions with conventional glass substrates. SOLUTION: In the crystallized glass for optical filter substrates, a crystal or a slid solution of which the averaged coefficient of linear expansion at a temperature of -30 deg.C to 70 deg.C is 95×10<-7> / deg.C to 130×10<-7> / deg.C and the chemical formula is Na4-x Kx Al4 Si4 O16 (0<=x<=1) is precipitated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a crystallized glass and an optical filter used for a substrate of an optical filter such as a band pass filter used in a wavelength division multiplexing (WDM) optical communication system.

[0002]

2. Description of the Related Art In a WDM optical communication system, a bandpass filter for selectively transmitting light of a specific wavelength range, for example, light of a specific wavelength of 1530 to 1620 nm, is required. A bandpass filter in which a dielectric multilayer film is formed on a substrate such as a substrate or a crystallized glass substrate is used.
The dielectric multilayer film is a film in which thin films of a high-refractive-index dielectric such as TiO ₂ and Ta ₂ O ₅ and thin films of a low-refractive-index dielectric such as SiO ₂ are alternately laminated. Is a multilayer film of about 100 layers.

A substrate used in such a band-pass filter has a temperature range of -30.degree. C. to 70.degree. C. in order to compensate for a temperature change in the refractive index of the dielectric multilayer film and to suppress a temperature change in the wavelength passing through the band-pass filter. the average coefficient of linear expansion alpha _L is required to be in the range of ^{95 × 10 -7 / ℃ ~130 ×} 10 -7 / ℃ in.

The composition expressed in mol% is SiO ₂ : 47.3.
%, TiO ₂ : 24.2%, Na ₂ O: 15.6%, K _{2
O: 6.3%, Li 2 O} : 4.6%, BaO: 1.8
%, And MgO: 0.2% (“conventional glass”) has α _L of 101 × 10 ⁻⁷ / ° C. and is used as a substrate of a bandpass filter.

However, the glass substrate made of the above-mentioned conventional glass has a problem that the warpage of the substrate during film formation is large. This is considered to be because the Young's modulus E (= 83 GPa) of the conventional glass is small, and a substrate having a larger E is required. As a substrate that solves this problem, the composition expressed in mol% is SiO ₂ : 74.1%, Al ₂ O ₃ : 4.0%,
ZrO ₂ : 0.6%, K ₂ O: 1.2%, Li ₂ O: 1
8.1%, MgO: 1.1%, ZnO: 0.4%, P ₂
There has been proposed a crystallized glass substrate made of crystallized glass in which O ₅ : 0.4% and lithium disilicate crystals are precipitated (“conventional crystallized glass”). Α _L of this conventional crystallized glass is 111 × 10 ⁻⁷ / ° C., and E is 96 GPa.

[0006]

The conventional crystallized glass substrate made of crystallized glass solves the problems relating to α _L and E. However, compared with the case where a multilayer film is formed on a glass substrate made of conventional glass. There was a problem that it was difficult to adjust the film forming conditions. An object of the present invention is to provide crystallized glass for an optical filter substrate and an optical filter that solve the above problems.

[0007]

According to the present invention, a temperature range of -30.degree.
The average linear expansion coefficient α _{L at} 0 ° C. is 95 × 10 ⁻⁷ / ° C.
130 × 10 ⁻⁷ / ° C., Na _4-x K _x Al ₄ Si ₄ O
Provided is a crystallized glass for an optical filter substrate on which a crystal or solid solution satisfying ₁₆ (0 ≦ x ≦ 1) is precipitated. Further, the present invention provides an optical filter characterized in that a dielectric multilayer film is formed on an optical filter substrate made of the crystallized glass for an optical filter substrate.

The present inventor has argued that it is difficult to adjust the film forming conditions on a crystallized glass substrate made of a conventional crystallized glass because the expansion characteristic at 70 ° C. or more is different between the conventional crystallized glass and the conventional glass. Think that
The present invention has been reached.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The crystallized glass in the present invention is one in which a crystal or a solid solution exists in the glass, and the existence of the crystal or the solid solution can be examined by a known X-ray diffraction method. The crystallized glass for an optical filter substrate of the present invention (“crystallized glass of the present invention”) is crystallized glass used for a substrate of an optical filter such as a bandpass filter.

The α _L of the crystallized glass of the present invention is 95 × 10
⁻⁷ / ° C. to 130 × 10 ⁻⁷ / ° C., whereby the crystallized glass of the present invention can be applied to a substrate such as a bandpass filter for WDM optical communication. α _L is preferably 100 × 1
0 ⁻⁷ / ° C. to 120 × 10 ⁻⁷ / ° C. or more.

The average linear expansion coefficient α _{70 at 70 to} 100 ° C. of the crystallized glass of the present invention is 95 × 10 ⁻⁷ / ° C. to 12
It is preferably 5 × 10 ⁻⁷ / ° C. The α ₇₀ of the conventional glass is 105 × 10 ⁻⁷ / ° C. Average linear expansion coefficient α at 100 to 140 ° C. of the crystallized glass of the present invention
₁₀₀ is preferably from 110 × 10 ⁻⁷ / ° C. to 135 × 10 ⁻⁷ / ° C. The α ₁₀₀ of the conventional glass is 127
× 10 ^-7 / ° C. 140- of the crystallized glass of the present invention
The average linear expansion coefficient α _{140 at} 190 ° C. is 115 × 1
It is preferably from 0 ⁻⁷ / ° C. to 140 × 10 ⁻⁷ / ° C.
Note that α ₁₄₀ of the conventional glass is 135 × 10 ⁻⁷ / ° C.

The crystallized glass of the present invention has a temperature of 190 to 220 ° C.
Mean linear expansion coefficient α_HIs preferably 80 × 10
^-7/ ℃ ～ 150 × 10^-7/ ° C, more preferably 110 ×
10 ^-7/ ° C-145 x 10^-7/ ° C, particularly preferably 12
0x10^-7/ ℃ ～ 140 × 10^-7/ ° C. Note that
Coming glass α_HIs 137 × 10^-7/ ℃, conventional crystallized glass
Α_HIs 65 × 10^-7/ ° C.

The crystallized glass of the present invention has a typical temperature at which a film is formed at the time of manufacturing a bandpass filter for WDM optical communication, that is, 190 to 200, as compared with a conventional crystallized glass.
The expansion characteristic at 20 ° C. is closer to the expansion characteristic of the conventional glass, and therefore, it is easy to adjust the film forming conditions.

In the crystallized glass of the present invention, Na _4-x
Precipitation of a crystal or a solid solution of K _x Al ₄ Si ₄ O ₁₆ (0 ≦ x ≦ 1) (hereinafter collectively referred to as “nepheline-based crystal”) is essential. When the nepheline-based crystal is not precipitated, the expansion characteristic at 70 ° C. or more, particularly α _H
It is difficult to bring the glass closer to the conventional glass. In the crystallized glass of the present invention, other crystals or solid solutions may be precipitated as long as the object of the present invention is not impaired.

[0015] The E of the crystallized glass of the present invention is preferably 85 GPa or more. If it is less than 85 GPa, the warpage of the substrate during film formation may increase.

Vickers hardness H of the crystallized glass of the present invention
_V is preferably 650 or more. If it is less than 650, cracking or chipping may occur during polishing or cutting.

The crystallized glass of the present invention has a wavelength of 1550 n.
The extinction coefficient μ ₁₅₅₀ for the light of m is preferably 0.03 mm ⁻¹ or less. If it exceeds 0.03 mm ⁻¹ , there is a possibility that application to a bandpass filter for WDM optical communication becomes difficult. More preferably 0.02 mm ^-1 or less, particularly preferably 0.01 mm ^-1 or less, most preferably 0.005 m ^-1
m ⁻¹ or less. The extinction coefficient is calculated from, for example, the transmittance of samples having different thicknesses, and includes a term due to loss without energy absorption such as scattering.

The crystallized glass of the present invention is typically produced as follows. That is, the raw materials are mixed and mixed, and then melted to obtain a molten glass. After the molten glass is formed into a desired shape and cooled, heat treatment is performed to precipitate crystals such as nepheline-based crystals or solid solutions.

The crystallized glass of the present invention is represented by the following oxide-based mol%, SiO ₂ 30 to 65%, Al ₂ O ₃ 5 to 35%, TiO ₂ + ZrO ₂ 1 to 15%, Na ₂ O 5 _{~40%, K 2 O 0~20%} , Li 2 O 0~15%, 0~15% MgO, CaO 0~15%, SrO 0~15%, BaO 0~15%, 0~15% ZnO, _{B 2 O 3 0~15%, P} 2 O 5 0~15%, Y 2 O 3 0~15%, preferably consists essentially of.

In terms of mol% based on the following oxides, SiO ₂ 44 to 55%, Al ₂ O ₃ 15 to 25%, TiO ₂ + ZrO _{2 2 to} 10%, Na ₂ O 10 to 20%, K ₂ O 0 _{~10%, Li 2 O 0~5%} , 0~10% MgO, CaO 0~10%, SrO 0~10%, BaO 0~10%, 0~10% ZnO, B 2 O 3 0~10% , P ₂ O ₅ 0 to 5%, and Y ₂ O ₃ 0 to 10%.

Next, regarding the above preferred embodiment, mol%
Is simply described as%. SiO ₂ is a network former and a main component of nepheline-based crystals, and is essential. If it is less than 30%, devitrification tends to occur, or dense nepheline-based crystals cannot be obtained. It is preferably at least 35%, more preferably at least 40%, particularly preferably at least 44%. If it exceeds 65%, expansion coefficients (hereinafter simply referred to as expansion coefficients) or E such as α _L and α _H become small. It is preferably at most 60%, more preferably at most 55%.

Al ₂ O ₃ is a component for improving the chemical durability, and is a main component of nepheline-based crystals and is essential. If it is less than 5%, nepheline-based crystals are not easily precipitated. It is preferably at least 10%, more preferably at least 13%, particularly preferably at least 15%. If it exceeds 35%, melting of the glass becomes difficult. It is preferably at most 30%, more preferably at most 27%, particularly preferably at most 25%.

TiO ₂ and ZrO ₂ are nucleating agents for nepheline crystal precipitation, and at least one of them is essential. If the total content of TiO ₂ and ZrO ₂ is less than 1%, it becomes difficult to precipitate nepheline-based crystals. It is preferably at least 2%. If the total is more than 15%, melting of the glass becomes difficult or the glass tends to be devitrified. Preferably it is 10% or less.

TiO ₂ is preferably at most 10%, more preferably at most 8%. ZrO ₂ is preferably 1
0% or less, more preferably 6% or less, particularly preferably 4% or less.
% Or less.

Na ₂ O is a main component of the nepheline-based crystal, a component that increases the expansion coefficient and improves the solubility of glass, and is essential. If it is less than 5%, it becomes difficult to precipitate nepheline-based crystals, the expansion coefficient becomes small,
Or it becomes difficult to melt the glass. It is preferably at least 8%, more preferably at least 10%. At over 40%
E becomes small, or chemical durability decreases. It is preferably at most 35%, more preferably at most 30%, particularly preferably at most 25%, most preferably at most 20%.

K ₂ O is not essential, but may be contained up to 20% in order to improve the solubility of the glass or to increase the expansion coefficient. If it exceeds 20%, E becomes small or the chemical durability decreases. Preferably 1
It is at most 5%, more preferably at most 10%. When K ₂ O is contained, its content is preferably 1% or more. It is more preferably at least 2%, particularly preferably at least 3%. When E is to be increased or chemical durability is to be further improved, it is preferable that K ₂ O is not substantially contained.

Although Li ₂ O is not essential, in order to improve the solubility of the glass and to increase the expansion coefficient,
Alternatively, it may be contained up to 15% in order to increase E. If it exceeds 15%, devitrification tends to occur. Preferably 10%
Or less, more preferably 5% or less. When Li ₂ O is contained, its content is preferably 0.5% or more. It is more preferably at least 1%, particularly preferably at least 2%.

MgO is not essential, but may be added to improve the solubility of the glass or increase E.
%. If it exceeds 15%, devitrification tends to occur. It is preferably at most 12%, more preferably at most 10%. When MgO is contained, its content is preferably 1% or more. It is more preferably at least 2%.

Although CaO, SrO and BaO are not essential, they may each be contained up to 15% in order to improve the solubility of the glass or to increase the expansion coefficient. If it exceeds 15%, devitrification tends to occur, or nepheline-based crystals hardly precipitate. Preferably 12
%, More preferably 10% or less. CaO, S
When rO or BaO is contained, its content is preferably 1% or more. It is more preferably at least 2%.

ZnO is not essential, but may be added to improve the solubility of the glass or to increase E.
%. If it exceeds 15%, devitrification tends to occur. It is preferably at most 12%, more preferably at most 10%. When ZnO is contained, its content is preferably 1% or more. It is more preferably at least 2%.

B ₂ O ₃ is not essential, but may be contained up to 15% in order to improve the solubility of glass. 15%
If it is more than E, E becomes too small or the chemical durability decreases. Preferably it is 10% or less. When B ₂ O ₃ is contained, its content is preferably 0.1% or more. It is more preferably at least 1%, particularly preferably at least 3%. Also, if you want to further improve chemical durability,
It is preferable that B ₂ O ₃ is not substantially contained.

P ₂ O ₅ is not essential, but may be contained up to 15% to promote nucleation for nepheline-based crystal precipitation. If it exceeds 15%, E may be too small, the solubility of glass may be reduced, or the glass may be easily devitrified. It is preferably at most 10%, more preferably at most 5%. When P ₂ O ₅ is contained, its content is preferably 1% or more. It is more preferably at least 2%, particularly preferably at least 3%. When it is desired to further improve the solubility of glass or to increase E, it is preferable that P ₂ O ₅ is not substantially contained.

Although Y ₂ O ₃ is not essential, in order to improve the melting property of glass or to increase E, 1 2
You may contain up to 5%. If it exceeds 15%, devitrification tends to occur. Preferably it is 10% or less. When Y ₂ O ₃ is contained, its content is preferably at least 0.1%.
It is more preferably at least 1%, particularly preferably at least 3%.

In the preferred embodiment, the crystallized glass of the present invention consists essentially of the above components, but may contain other components as long as the object of the present invention is not impaired. The total content of the other components is preferably 15% or less,
It is more preferably at most 10%, particularly preferably at most 5%.

The other components will be described below. E
To increase V_TwoO_Five, Cr_TwoO_Three, MnO, Fe
_TwoO_Three, CoO, NiO, CuO, Ga_TwoO_Three, GeO_Two,
Nb_TwoO_Five, MoO_Three, La_TwoO_Three, CeO_Two, Pr_TwoO_Three, N
d_TwoO_Three, Pm_TwoO_Three, Sm_TwoO_Three, Eu_TwoO_Three, Gd_TwoO_Three, T
b_TwoO_Three, Dy _TwoO_Three, Ho_TwoO_Three, Er_TwoO_Three, Tm_TwoO_Three, Y
b_TwoO_Three, HfO_Two, Ta_TwoO_FiveAnd WO_ThreeGroup consisting of
This group is hereinafter referred to as Group A. One or more components selected from)
May be contained. Note that the total content of the components of Group A is
It is preferably at most 15%. Above 15%, devitrification
Or the coefficient of expansion may be reduced.
You. More preferably 10% or less, particularly preferably 5% or less.
Below, most preferably 3% or less. Also, the components of group A
When containing, the sum of their contents is preferably
0.1% or more, more preferably 1% or more, particularly preferably
Is 2% or more.

As fining agents, SO ₃ , As ₂ O ₅ ,
It may contain Sb ₂ O ₅ , F, Cl and the like. The total content of the fining agent is preferably not more than 2%, especially S
The total content of O ₃ , As ₂ O ₅ , Sb ₂ O ₅ , F and Cl is preferably not more than 1.9%. Also, PbO
Is preferably not substantially contained.

The crystallized glass of the preferred embodiment of the present invention is produced, for example, as follows. That is, the glass is melted, formed into a plate shape, and then cooled to obtain a glass plate. Next, after cutting the glass plate to a desired size, the cut glass plate is heated to 500 to 750 ° C. for 1 hour to
Hold for 5 hours to generate crystal nuclei.
Heat treatment for growing crystals while maintaining the temperature at 00 ° C. for 1 to 5 hours is performed to obtain crystallized glass.

The optical filter of the present invention is manufactured by forming a dielectric multilayer film on the optical filter substrate made of the crystallized glass of the present invention by a vapor deposition method, a sputtering method or the like. The dielectric multilayer film is a film in which thin films of a high-refractive index dielectric such as TiO ₂ and Ta ₂ O ₅ and thin films of a low-refractive index dielectric such as SiO ₂ are alternately laminated. Is a multilayer film of about 100 layers.

The optical filter of the present invention is suitable for a band-pass filter, an edge filter, a gain flattening filter, a beam splitter, and the like used in a WDM optical communication system, but the application is not limited thereto.

[0040]

EXAMPLES Examples 1 to 4 shown in the table are examples, and
Example 6 is a commercially available conventional crystallized glass and conventional glass, and is a comparative example. The compositions shown in the columns of SiO _{2 to} P ₂ O _{5 in} the table are compositions expressed in mol%. For Examples 1-4, the ingredients were mixed and placed in a platinum crucible at 1650 ° C.
And melted for 5 hours. At this time, the molten glass was homogenized by stirring with a platinum stirrer for 2 hours. Next, the molten glass was poured out, formed into a plate shape, and then gradually cooled to obtain a glass plate. The glass plate is heated from room temperature to 500 ° C. at 300 ° C. /
The heat treatment was performed by raising the temperature at a rate of time from 500 to 750 ° C. at a rate of 50 ° C./hour and from 750 to 900 ° C. at a rate of 300 ° C./hour, and maintaining the temperature at 900 ° C. for t hours. The t (unit: time) is shown in the table.

For Examples 1 to 6, the density d (unit: g /
cm), E (unit: GPa), expansion coefficient α_L, Α₇₀, Α
₁₀₀, Α₁₄₀, Α_H(Unit: 10^-7/ ° C), μ₁₅₅₀(single
Rank: mm ^-1), Internal transmittance T at a thickness of 1 mm (unit:
%), H_V, The precipitated crystals, are measured or
Specified. The results are shown in the table. "-" In the table indicates that the data
Indicates no.

D: Measured by Archimedes' method. E: The thickness polished so that both surfaces are parallel to 10 to 2
0mm, about a 4cm x 4cm plate sample,
It was measured by the ultrasonic pulse method.

Α _L , α ₇₀ , α ₁₀₀ , α ₁₄₀ , α _H : diameter 5 m
m, about a sample processed into a cylindrical shape with a length of 20 mm,
Thermomechanical analyzer (trade name: TMA81, manufactured by Rigaku Corporation)
40) at a rate of 5 ° C./min from −50 ° C. to +230
° C. to obtain an expansion curve showing a temperature-elongation relationship,
It was calculated from the expansion curve.

Μ ₁₅₅₀ : For each of a plate-shaped sample having a size of 4 cm × 4 cm and a thickness of 1 mm, both surfaces of which are mirror-polished, and a plate-shaped sample which is the same as the above-mentioned plate-shaped sample except that the thickness is 4 mm The transmittance for light having a wavelength of 1550 nm was measured using a spectrophotometer (trade name: U-3500, manufactured by Hitachi, Ltd.). From the transmittance T ₁ at a thickness of ₁ mm and the transmittance T _{4 at a} thickness of 4 mm obtained by the measurement, it was calculated by the following equation. μ ₁₅₅₀ = −log _e (T ₄ / T ₁ ) / 3.

T: Calculated by the following equation. T = 100 × exp (−μ ₁₅₅₀ ).

H _V : A plate-like sample having a thickness of 4 mm and a size of 4 cm × 4 cm polished so that both surfaces are parallel to each other,
The measurement was performed by pressing a Vickers indenter with a load of 1N.

Precipitated crystals: The precipitated crystals were identified by X-ray diffraction.
Specified. In Examples 1 to 4, Na was used. _ThreeKAl_FourSi_FourO₁₆
Crystals (nepheline) were precipitated. Example 6
I did not check.

In connection with Example 3, Sample 3a was prepared in the same manner as in Example 3 except that the temperature was not held at 900 ° C. for 1 hour, and the precipitated crystal was identified by X-ray diffraction. As a result, crystals of magnesium-titanium oxide (MgTi ₂ O ₅ ) and magnesium-aluminum-titanium oxide (Mg ₄ Al ₂ Ti ₉ O ₂₅ ) were found to precipitate in sample 3a. That is, these crystals are considered to be the crystal nuclei in Example 3.

[0049]

[Table 1]

[0050]

According to the present invention, in manufacturing a bandpass filter used in a WDM optical communication system, a film can be formed in the same manner as on a glass substrate made of conventional glass, and the temperature change of the wavelength passing through the bandpass filter can be suppressed. And an optical filter substrate having a large E can be provided. further,
An optical filter substrate having a small extinction coefficient, that is, a large internal transmittance, or an optical filter substrate having a large hardness can be provided.

Since the crystallized glass of the present invention has a large E, the warpage of the substrate after film formation can be reduced, and as a result, polishing and cutting of the substrate after film formation become easy. Further, since the crystallized glass of the present invention has a high hardness, cracking or chipping of the substrate during polishing or cutting is reduced.

The optical filter of the present invention can provide an optical communication filter having a small temperature dependence of the passing wavelength, a small wavelength interval, and a large multiplicity.

Continued on front page F-term (reference) 2H048 GA04 GA09 GA33 GA62 4G062 AA04 AA11 BB01 CC01 CC09 CC10 DA05 DA06 DB03 DB04 DB05 DC01 DC02 DC03 DC04 DD01 DD02 DD03 DD04 DE01 DE02 DE03 DE04 DF01 EA01 EA02 EA03 EA04 EC03 EC03 EB04 EC03 EC03 ED01 ED02 ED03 ED04 EE01 EE02 EE03 EE04 EF01 EF02 EF03 EF04 EG01 EG02 EG03 EG04 FA01 FB03 FB04 FC03 FC04 FD01 FD02 FD03 FD04 FF01 F02 F03 F01 F02 F03 F01 F02 F03 F01 F02 F03 F01 F02 F03 F01 F02 F03 F01 F02 F03 F01 F02 GB01 GB02 GB03 GC01 GD01 GE01 GE02 GE03 HH01 HH03 HH04 HH05 HH06 HH07 HH08 HH09 HH11 HH12 HH13 HH15 HH17 HH18 HH20 JJ01 JJ03 JJ04 JJ05 JJ06 JJ07 JJ10 KK01 KK02 KK03 KK03 KK03 KK03 KK04 KK03 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK03 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK04 KK01

Claims (7)

[Claims] An average linear thermal expansion coefficient α _{L at} −30 ° C. to 70 ° C. is 95 × 10 ⁻⁷ / ° C. to 130 × 10 ⁻⁷ / ° C., and Na _4-x K _x Al ₄ Si ₄ O ₁₆ A crystallized glass for an optical filter substrate on which crystals or solid solutions satisfying (0 ≦ x ≦ 1) are precipitated. 2. The crystallized glass for an optical filter substrate according to claim 1, wherein the average linear expansion coefficient α _{H at} 190 to 220 ° C. is 80 × 10 ⁻⁷ / ° C. to 150 × 10 ⁻⁷ / ° C. Wherein alpha _H is ^{110 × 10 -7 / ℃ ~145 ×} 10
3. The crystallized glass for an optical filter substrate according to claim 1, which has a temperature of ^-7 / ° C. 4. The crystallized glass for an optical filter substrate according to claim 1, wherein the Young's modulus is 85 GPa or more. 5. The crystallized glass for an optical filter substrate according to claim ^{1, wherein the} extinction coefficient for light having a wavelength of 1550 nm is 0.03 mm ⁻¹ or less. 6. The following oxide-based mol% representation: SiO ₂ 30-65%, Al ₂ O ₃ 5-35%, TiO ₂ + ZrO ₂ 1-15%, Na ₂ O 5-40%, K ₂ O 0-20%, Li ₂ O 0-15%, MgO 0-15%, CaO 0-15%, SrO 0-15%, BaO 0-15%, ZnO 0-15%, B ₂ O ₃ 0 _{15%, P 2 O 5 0~15} %, Y 2 O 3 0~15%, optical filter substrate for crystallized glass according to any one of claims 1 to 5 consisting essentially of. 7. An optical filter, wherein a dielectric multilayer film is formed on an optical filter substrate made of crystallized glass for an optical filter substrate according to claim 1.