JP2003342036A - Glass for wdm light filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide glass for a WDM light filter which does not need a long- time heating at a high temperature in its production and has a good processibility even after vitrified. <P>SOLUTION: This glass for a WDM light filter having an optical multi-layer film for band pass formed on its surface comprises 50-65 wt.% SiO<SB>2</SB>, 5-25 wt.% Na<SB>2</SB>O, 4-20 wt.% K<SB>2</SB>O, 0-20 wt.% CaO, 0-10 wt.% MgO, 0-10 wt.% BaO, 0-10 wt.% Al<SB>2</SB>O<SB>3</SB>, and 0-10 wt.% TiO<SB>2</SB>and has an average thermal expansion coefficient at 50-150°C of 110-130×10<SP>-7</SP>/°C, a Young's modulus of 80 GPa or lower, and a density of 2.8 g/cm<SP>3</SP>or lower. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical wavelength division multiplexing in the field of optical communication.
(ion multiplexing, abbreviated WDM)
W that requires a high coefficient of thermal expansion as a material of a WDM optical filter used for
The present invention relates to glass for DM optical filters.

[0002]

2. Description of the Related Art Optical filters include those that cut a specific wavelength, those that allow transmission, and those that reduce the light intensity regardless of the wavelength. The former optical filters include a bandpass filter that passes only specific wavelengths, a notch pass filter that cuts only certain wavelengths, a highpass filter that passes only wavelengths shorter or longer than a certain wavelength, and a lowpass filter. , The latter optical filter has N
There is a D filter.

Among these filters, in wavelength division multiplexing optical communication, in order to combine lights having slightly different wavelengths, or conversely, to selectively extract light of a specific wavelength from light containing a plurality of wavelength components. Demultiplexing is performed and a bandpass filter is used.

A narrow band bandpass filter according to the development of such a wavelength division multiplexing (WDM) system is a WDM
It is called an optical filter and is disclosed in Japanese Patent Application Laid-Open No. 10-339825 and Japanese Patent Application Laid-Open No. 10-512975, and the structure thereof is SiO ₂ , TiO ₂ , T on a quartz substrate.
A dielectric multilayer film made of a ₂ O ₅ or the like is formed.

In order to carry out higher-density wavelength-division-multiplexed optical communication in accordance with the higher precision of the wavelength-division multiplexing (WDM) system, the WDM optical filter is required to have a narrow transmission wavelength bandwidth. Therefore, the temperature stability of the central wavelength of the band is important. That is, it is required to avoid the fluctuation of the refractive index due to the fluctuation of the operating temperature of the WDM optical filter member and to make the temperature shift of the wavelength equal to zero. It is known that the temperature shift depends on the thermal expansion coefficient of the glass and the dielectric multilayer film.

In order to make the temperature shift equal to zero, a glass having a thermal expansion coefficient close to that of the dielectric multilayer film is disclosed in Japanese Patent Laid-Open No.
It is disclosed in JP-A 1-89184, JP 2001-48584 A, and JP 2001-66425 A.

[0007]

[Patent Document 1] Japanese Unexamined Patent Application Publication No.
The glass having the composition described in Japanese Patent Application Laid-Open No. 001-89184 has a problem that the glass is fragile, and when cutting it into chips by dicing with a diamond cutter, the ends are chipped and the yield is poor.

Further, Japanese Patent Laid-Open No. 2001-48584,
In Japanese Unexamined Patent Publication No. 2001-66425, glass ceramics, that is, crystallized glass is used. However, there is a problem in that heat treatment for a long time is required for crystallization, which results in high cost.

[0009]

In order to solve such a problem, a soda-lime glass which does not require heating at a high temperature for a long time at the time of production and has good workability even after being made into glass, is used in the present invention. The present inventors have diligently studied the type of the composition and the glass composition, have obtained a glass having physical properties suitable for a WDM optical filter, and have completed the glass for a WDM optical filter of the present invention.

That is, the present invention is a glass for a WDM optical filter which has an optical multi-layer film for band pass formed on its surface,
Expressed in wt%, the glass composition is SiO ₂ , 50-
65%, Na ₂ O, 5 to 25%, K ₂ O, 4 to 20%, C
aO, 0-20%, MgO, 0-10%, BaO, 0
10%, Al ₂ O ₃ , 0-10%, TiO ₂ , 0-10%
Is a glass for WDM optical filters.

Further, the present invention is the above-mentioned optical filter glass, which has an average coefficient of thermal expansion of 110 to 130 × 10 ^-7 / ° C. and a Young's modulus of 80 GPa at 50 to 150 ° C.
The glass for a WDM optical filter is characterized by having a density of 2.8 g / cm ³ or less.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION It is known that there is an optimum range for the coefficient of thermal expansion in glass for WDM optical filters. That is, if it is too low, sufficient compressive stress cannot be applied to the optical multilayer film, and the temperature shift of the center wavelength of the filter increases in the positive direction. Further, if it is too high, the temperature shift becomes large in the negative direction, and at the same time, there arises a problem that the multilayer film is peeled off.

The inventor of the present invention has found that SiO ₂ / Ta ₂
When an O ₅ -based 3-cavity bandpass filter was produced and the center wavelength was confirmed, a preferable average thermal expansion coefficient at 50 to 150 ° C. was 110 to 130 × 10 ⁻⁷ /
It was found to be in the range of ° C. Within the range, an appropriate compressive stress can be applied to the multilayer film, and the temperature dependence of the filter characteristics is infinitely 0 depending on the film forming method.
Can be approached to. Therefore, the preferable average thermal expansion coefficient of the glass for WDM optical filter of the present invention is 50 to
It is 110 to 130 × 10 ⁻⁷ / ° C. at 150 ° C.

Further, the glass for WDM optical filter needs to be cut into chips by a cutting process such as dicing process when it is used as a filter, and it is required that it is not brittle.

Regarding the Young's modulus, it is generally known that the material becomes brittle as the Young's modulus increases. Even with brittle materials such as glass, it is a fact recently revealed that the material tends to become brittle when the Young's modulus increases.

The inventor of the present invention dice-processes a plurality of substrates having different Young's moduli actually formed with a multi-layered film under the same conditions,
By evaluating the degree of chipping of the obtained chip edge, it was found that if the Young's modulus is 80 GPa or less, good workability is exhibited. Young's modulus is 80 GPa
Below, if it is preferably 75 GPa or less, it is possible to suppress the warpage of the glass during the formation of the multilayer film within an allowable range. Therefore,
The preferred Young's modulus of the glass for WDM optical filter of the present invention is as follows:
It is 80 GPa or less.

Regarding the density, if the glass type is the same, the glass tends to become brittle as the density increases.
Therefore, the preferable density of the glass for WDM optical filter of the present invention is 2.8 g under the working temperature during cutting.
/ Cm ³ or less.

The present inventor has confirmed that SiO ₂ and Na are essential components.
₂ O, K ₂ O, and CaO, MgO, B as additional components
aO where, using the Al ₂ O _3, TiO _2, to produce a respective adjusting glass glass composition of each component, 50 to 15
The average coefficient of thermal expansion at 0 ° C is 110 to 130 × 10 ^-7
/ ° C, Young's modulus is 80 GPa or less, and density is 2.8 g
/ Cm ³ or less of the glass for a soda-lime glass-based WDM optical filter of the present invention was obtained, and the present invention was completed.

The role of each component and the glass composition will be described in detail below.

SiO ₂ is an essential component of the glass for a WDM optical filter of the present invention, which is introduced into glass to form a glass skeleton. The glass composition of SiO ₂ is 50 wt.
If it is less than%, the glass state becomes unstable and devitrification and the like are likely to occur. On the other hand, when it exceeds 65 wt%, the coefficient of thermal expansion becomes low, that is, the average coefficient of thermal expansion at 50 to 150 ° C.,
It is difficult to obtain a temperature of 110 × 10 ⁻⁷ / ° C. or higher. Therefore, SiO
The preferable glass composition range of ₂ is 50 to 65 wt%.

Na ₂ O is an essential component of the glass for a WDM optical filter of the present invention, which is introduced into the glass in order to increase the coefficient of thermal expansion of the glass. That is, in the glass for a WDM optical filter of the present invention, in order to obtain an average thermal expansion coefficient at 50 to 150 ° C. of 110 × 10 ⁻⁷ / ° C. or more, the glass composition of Na ₂ O needs to be 5 wt% or more,
If it is less than 5 wt%, the desired coefficient of thermal expansion cannot be obtained.
On the other hand, when the glass composition of Na ₂ O exceeds 25 wt%, the glass state becomes unstable and devitrification is likely to occur. Therefore, the preferable glass composition range of Na ₂ O is 5 to 25 wt.
%.

Like Na ₂ O, K ₂ O is an essential component of the glass for WDM optical filters of the present invention, which is introduced into the glass in order to keep the coefficient of thermal expansion of the glass high. That is,
In the glass for WDM optical filter of the present invention, 50 to
Average thermal expansion coefficient at 150 ℃, 110 × 10 ^-7 / ℃
In order to obtain the above, the glass composition of K ₂ O must be 4 wt% or more, and if it is less than 4 wt%, the desired thermal expansion coefficient cannot be obtained. On the other hand, the glass composition of K ₂ O is 20 wt%
If it exceeds, the glass state becomes unstable and devitrification is likely to occur. Therefore, the preferable glass composition range of K ₂ O is 4
~ 20 wt%.

CaO is an additional component of the glass for a WDM optical filter of the present invention, which is incorporated into glass because the coefficient of thermal expansion, Young's modulus and density of the glass can be adjusted by adjusting the glass composition. That is, in the glass for WDM optical filter of the present invention, the average coefficient of thermal expansion at 50 to 150 ° C., 110 × 10 ⁻⁷ / ° C. or more and Young's modulus, 8
In order to obtain 0 GPa or less, the glass composition of CaO is 2
It should be 0 wt% or less. On the other hand, when the glass composition of CaO exceeds 20 wt%, the glass state becomes unstable and devitrification and the like are likely to occur. Therefore, the preferable glass composition range of CaO is 0 to 20 wt%.

MgO and BaO are additional components of the glass for a WDM optical filter of the present invention, which are introduced into the glass in order to adjust the coefficient of thermal expansion and Young's modulus of the glass like CaO described above. The thermal expansion coefficient and Young's modulus of the glass can be adjusted by substituting a part of CaO described above in the range of 10 wt% or less for each of MgO and BaO with respect to the total weight of the glass. On the other hand, when the glass compositions of MgO and BaO exceed 10 wt%, the glass state becomes unstable and devitrification and the like are likely to occur. Therefore, MgO, Ba
The preferable glass composition range of O is 0 to 10 wt%.

Al₂O₃Inclusion of stabilizes the glass state
In addition to being effective, thermal expansion can be achieved by adjusting the glass composition.
Introduced in glass to be able to adjust modulus and Young's modulus
Which is an additional component of the glass for WDM optical filter of the present invention
Is. However, Al ₂O₃Glass composition of 10w
If it exceeds t%, the coefficient of thermal expansion becomes too low, that is, 5
Average thermal expansion coefficient at 0 to 150 ° C., 110 × 10
^-7It is difficult to obtain less than / ° C. Therefore, Al₂O₃Preferred
The glass composition range is 0 to 10 wt%.

TiO ₂ is incorporated into the glass because the Young's modulus can be adjusted by adjusting the content thereof.
It is an additional component of optical filter glass. Said Si
The Young's modulus can be adjusted by substituting a part of O ₂ in the range of up to 10 wt% with respect to the total weight of the glass. However, when the glass composition of TiO ₂ exceeds 10 wt%, the glass state becomes unstable and devitrification and the like are likely to occur. Further, the Young's modulus becomes 80 GPa or more, and the glass becomes brittle. Therefore, the preferable glass composition range of TiO ₂ is 0 to 10 wt%.

Also, with respect to Li ₂ O, B ₂ O ₃ and ZrO ₂ , up to 5% by weight of each of the total weight of the glass within the range that does not impair the preferable physical properties of the glass as the WDM optical filter glass. Can be introduced.

In the manufacture of WDM optical filters, the center wavelength of the bandpass of the filter can be corrected to some extent by heating and holding the chip for WDM optical filter at an appropriate temperature below the glass transition temperature, There is a process of actually correcting.

In this adjustment, if the glass has a low glass transition point (Tg), it cannot be heat-treated at a temperature sufficient for the adjustment. In the WDM optical filter glass of the present invention, by setting the glass transition temperature to 500 ° C. or higher, it was possible to perform heat treatment at a temperature up to 500 ° C. to correct the central wavelength.

[0030]

EXAMPLES Oxides, carbonates, nitrates, etc. corresponding to the respective raw materials of the respective components of glass were used, and the obtained glass was described in Examples 1 to 9 in Table 1 and Comparative Examples 1 to 5 in Table 2. The mixture was weighed and mixed at a predetermined ratio so as to obtain the composition.

The mixed raw materials were mixed in a volume of 2000 ml,
Put in a platinum crucible containing 10 wt% rhodium,
After melting for 5 hours in an electric furnace heated to 1300 ° C., it was poured into a graphite mold and placed in an electric furnace that had been held near the glass transition point in advance, and then held for 2 hours. By cooling to room temperature, a glass block having a thickness of 30 mm and a size of 200 mm × 300 mm was obtained.

Next, after thinly slicing the glass block, it is ground into a cylindrical shape, both sides are further polished, and Ta ₂ O ₅ and SiO ₂ are alternately deposited on one polished surface by a vapor deposition method to form a dielectric multilayer film. Got Then, grinding and polishing were performed from the side where no film was formed until the thickness became 1 mm. Further, an antireflection film was formed on the polishing surface opposite to the multilayer film.

The dielectric multi-layer film and the antireflection film can be produced by a method used for forming an ordinary optical thin film, for example,
Examples include various ion plating methods and sputtering methods.

Then, while rotating a diamond cutter in which diamond powder is adhered to a metal disk, the glass substrate on which the dielectric multilayer film has been formed is applied from the non-deposited surface side, and a thickness of 1 mm is obtained by so-called dicing processing. ,size,
The chips were cut into 1.5 mm square chips.

Table 1 relates to the WDM optical filter of the present invention, in which the composition and the glass composition of each composition are expressed by weight%, SiO ₂ , 50 to 65%, Na ₂ O, 5 to _{2
5%, K 2 O, 4~20} %, CaO, 0~20%, Mg
O, 0~10%, BaO, 0~10 %, Al 2 O 3, 0~
10%, TiO ₂ , Example 1 in the range of 0-10%
9 glass composition, its glass composition expressed in% by weight,
It shows the evaluation of physical properties, devitrification and processability.

[0036]

[Table 1]

Table 2 shows the compositions and the compositions of the glasses of Comparative Examples 1 to 5, which are out of the glass composition range, the glass compositions expressed in% by weight, the physical properties, the presence or absence of devitrification, and the processability. It is a thing.

[0038]

[Table 2]

As the physical properties, the average coefficient of thermal expansion at 50 to 150 ° C., Young's modulus, glass transition point and density were measured.

Regarding the devitrification property, the prepared glass was put into a platinum crucible containing 100 wt% of rhodium and having a volume of 100 ml, and the glass viscosity (η) was logη = 2,3.
Alternatively, it was evaluated for the presence or absence of devitrification after holding for 1 hour at each temperature of 4 dPa · s.

Regarding workability, the above-mentioned thickness of 1 mm,
This is an evaluation as to whether or not chipping, that is, chipping, has occurred in a chip of 1.5 mm square size, and is not chipped to the extent that it cannot be used as a WDM optical filter when viewed with a magnifying glass after dicing. Is indicated by ◯, the produced one is indicated by Δ, and the one in which the chip is not cut out by the dicing process and the substrate is damaged is indicated by x.

As shown in Table 1, the compositions of the glass for WDM optical filters of the present invention were used, and the glass of Examples 1 to 9 in which the glass composition of each composition was within the above range was 50 to 1
Average thermal expansion coefficient at 50 ° C is 110 to 130 × 10
^-7 / ° C, Young's modulus of 80 GPa or less, and density of 2.8
The content was g / cm ³ or less, and the devitrification property and workability were satisfactory.

In comparison, as shown in Table 2, Comparative Examples 1 to 1 in which the glass composition of each composition was out of the above composition range
The glass of No. 5 has an average coefficient of thermal expansion of 110 to 130 × 10.
^{If it is} out of the range of ⁻⁷ / ° C. (Comparative Examples 1 and 3) and the Young's modulus is out of the range of 80 GPa or less (Comparative Example 5), even if it is in these ranges, devitrification and workability are satisfactory. I couldn't get it.

[0044]

EFFECT OF THE INVENTION The glass for WDM optical filter of the present invention is soda lime glass which is easy to process, and therefore, the dicing process by the diamond cutter hardly causes the end portion to be processed when the chip is processed, and is excellent in processability. Unlike the crystallized glass, the heat treatment for a long time for crystallization is not required, and the price can be kept low.

In the composition of soda-lime glass,
By making the composition such that the coefficient of thermal expansion can be adjusted in the region where the glass is stable, an effective coefficient of thermal expansion was obtained for reducing the temperature dependence of the central wavelength of the WDM optical filter.

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[Procedure amendment]

[Submission date] May 13, 2003 (2003.5.1)
3)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0025

[Correction method] Change

[Correction content]

Al₂O₃Inclusion of stabilizes the glass state
In addition to being effective, thermal expansion can be achieved by adjusting the glass composition.
Introduced in glass to be able to adjust modulus and Young's modulus
Which is an additional component of the glass for WDM optical filter of the present invention
Is. However, Al ₂O₃Glass composition of 10w
If it exceeds t%, the coefficient of thermal expansion becomes too low, that is, 5
Average thermal expansion coefficient at 0 to 150 ° C., 110 × 10^-7
/ ° Cthat's allIs difficult to obtain. Therefore, Al₂O₃The preferred moth
The lath composition range is 0 to 10 wt%.

Continuation of front page (51) Int.Cl. ⁷ Identification symbol FI theme code (reference) G02B 6/293 G02B 6/28 CF term (reference) 2H048 GA04 GA09 GA33 GA60 GA62 4G062 AA04 BB01 DA06 DB01 DB02 DB03 DC01 DD01 DE01 DF01 EA01 EB03 EB04 EC03 EC04 ED01 ED02 ED03 EE01 EE02 EE03 EE04 EF01 EG01 EG02 EG03 FA01 FA10 FB01 FB02 FB03 FC01 FD01 FE01 FF01 FG01 FH01 FJ01 FK01 FL01 GA01 GA10 GB01 GC01 GD01 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH17 HH20 JJ01 JJ03 JJ05 JJ07 JJ10 KK01 KK03 KK05 KK07 KK10 MM04 NN29 NN33 NN40

Claims (2)

[Claims] 1. A glass for a WDM optical filter having an optical multi-layer film for bandpass formed on the surface thereof, wherein the glass composition is represented by weight%, and the glass composition is SiO ₂ , 50 to 65%, Na _{2.
O, 5~25%, K 2 O} , 4~20%, CaO, 0~2
0%, MgO, 0-10%, BaO, 0-10%, Al
₂ O ₃ , 0-10%, TiO ₂ , 0-10% WDM
Glass for optical filters. 2. The glass for WDM optical filter according to claim 1, wherein the average thermal expansion coefficient at 50 to 150 ° C. is 110 to 130 × 10 ⁻⁷ / ° C. and the Young's modulus is 80 GP.
Glass for WDM optical filters, characterized in that the density is a or less and the density is 2.8 g / cm ³ or less.