JP2004107198A - Glass for laser beam machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide glass for laser beam machining which is capable of being machined to extend to the inside of the glass such as to be penetrated by the laser machining using ablation or vaporization by absorbed laser beam energy with precision machining and has small thermal expansion coefficient. <P>SOLUTION: The glass for laser beam machining contains titanium in an atomic, colloidal or ionic form and has a composition in the following range. That is, 60-79 mol% in total of net work-forming oxides (SiO<SB>2</SB>, B<SB>2</SB>O<SB>3</SB>), 5-20 mol% in total of intermediate oxides (Al<SB>2</SB>O<SB>3</SB>, TiO<SB>2</SB>) and 5-20 mol% in total of modifying oxides (Li<SB>2</SB>O, Na<SB>2</SB>O, K<SB>2</SB>O, Rb<SB>2</SB>O, Cs<SB>2</SB>O, MgO, CaO, SrO, BaO). Where, it is essential to contain 5-20 mol% TiO<SB>2</SB>. It is preferable that total amount of the intermediate oxides is ≤90% of total amount of the modifying oxides. <P>COPYRIGHT: (C)2004,JPO

Description

【００３０】
上記組成のレーザ加工用ガラス試料に、照射エネルギーを変えながら波長２６６ｎｍ、３５５ｎｍのレーザ光をそれぞれ照射した。この結果、得られた加工しきい値を表１に示す。
両波長の場合とも、ＴｉＯ_２の濃度が増大するほど、加工しきい値が顕著に減少していることがわかる。しかし、網目形成酸化物や修飾酸化物の組成には殆ど依存しない。
【００３１】
図２は発明者らが試験した各種組成について、Ａｌ_２Ｏ_３およびＴｉＯ_２の総量とＮａ_２Ｏの量との関係をプロットし、各組成のガラス化状態を示している。図よりＮａ_２Ｏに代表される修飾酸化物の量を少なくし過ぎると分相、失透が発生してしまうため、均一なガラスが作製できなくなることがわかる。すなわち、均一なガラスを作製するためには、Ａｌ_２Ｏ_３およびＴｉＯ_２の総量と修飾酸化物の総量とは、
（Ａｌ_２Ｏ_３＋ＴｉＯ_２）／（Ｌｉ_２Ｏ＋Ｎａ_２Ｏ＋Ｋ_２Ｏ＋Ｒｂ_２Ｏ＋Ｃｓ_２Ｏ＋ＭｇＯ＋ＣａＯ＋ＳｒＯ＋ＢａＯ）≦０．９　　　　　（１）
の関係が成り立つことが好ましい。
【００３２】
上記のように、レーザによる加工しきい値を下げるためには、ＴｉＯ_２を多く含ませることが必要だが、その場合、前記式（１）の条件を満たすためには修飾酸化物の濃度を増加させる必要がある。しかし、修飾酸化物の濃度を増加させると、一般に熱膨張係数は大きくなるので、加工しきい値を下げることと熱膨張係数を下げることはトレードオフの関係になっていることがわかる。
【００３３】
［比較例］
比較例１は通常の窓ガラスなどに用いられる、いわゆるソーダライムガラスである。実施例と同様に加工しきい値を求めると、レーザ光の波長が２６６ｎｍのときの最大パワー１．１０Ｗ、レーザ光の波長が３５５ｎｍのときの最大パワー２．１０Ｗのどちらにおいても、アブレーションもしくは蒸発を起こさず、試料に変化はなかった。ＴｉＯ_２の濃度が極めて低いか、もしくはＴｉＯ_２を含まない組成では、加工しきい値は極めて高くなる。
【００３４】
比較例２は表１に示すように、中間酸化物のＴｉＯ_２と修飾酸化物のＮａ_２Ｏをともに２０モル％を越える高濃度で含む材料である。実施例と同様に加工しきい値を求めると、レーザ光の波長が２６６ｎｍで１５ｍＷ、レーザ光の波長が３５５ｎｍで２００ｍＷと極めて低い値であった。しかし、上述した実施例の各ガラス組成の熱膨張係数が１００×１０^−７℃^−１より小さくなっているのに対して、比較例２の組成のガラスでは熱膨張係数が１１８×１０^−７℃^−１と大きくなっている。
【００３５】
以上の実施例と比較例を勘案すると、熱膨張係数ができるだけ小さく、かつ加工しきい値が低いガラスとしては、実施例１１、１２に代表される組成、すなわち（１）の条件を満たしたうえで、次の範囲の組成がもっとも好ましいことがわかる。
７０≦（ＳｉＯ_２＋Ｂ_２Ｏ_３）≦７９モル％
１０≦ＴｉＯ_２≦１５モル％
１０≦Ｎａ_２Ｏ≦１５モル％
【００３６】
【発明の効果】
本発明により、レーザ照射による加工しきい値が低く、かつ熱膨張係数の小さいレーザ加工用ガラスを提供できる。すなわち、本発明のレーザ加工用ガラスは、加工に必要なレーザ光エネルギーが少なくて済み、かつ熱による影響が少ないため、より精密な加工をすることができる。
【図面の簡単な説明】
【図１】レーザ照射による加工しきい値測定用光学系を示す模式図である。
【図２】均一なガラスが作製できる組成範囲を示す図である。
【符号の説明】
１　レーザ光照射装置
１０　レーザ光
１２　レーザ光源
２０　ガラス試料
２２　試料ホルダ
２４　試料ステージ
３０　照射シャッタ
４０　パワーメータ
５０　アッテネータ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a glass for laser processing, and more particularly to a glass having a glass composition suitable for laser processing.
[0002]
[Prior art]
In recent years, the material processing technology using the energy of laser light has been advanced to the area of fine processing.
In the processing technology using a mask pattern, due to the development of the patterning technology and the shortening of the wavelength of the laser, the processable length has entered the region of nanometers, which is shorter than micrometer.
On the other hand, in direct processing using a laser, as a result of shortening the pulse width and shortening the wavelength of laser light, processing of organic substances such as polyimide and metal has been advanced in the micrometer range.
[0003]
Processing such as drilling using a laser has progressed from thermal processing to ablation processing. Ablation is a phenomenon in which a laser beam having an extremely narrow pulse width is irradiated, so that the material at the irradiated portion is changed from melting to evaporation in a short time. Depending on the length of the pulse width, the degree of thermal influence on the periphery of the beam irradiation site differs. In the processing using an ultrashort pulse laser in which the irradiation of the beam is completed before the thermal diffusion occurs, it is possible to form a precise and fine hole with almost no heat-affected layer.
[0004]
However, most lasers used for actual processing have a pulse width of the order of nanoseconds or more, and in this case, the influence of heat cannot be avoided. Therefore, a photochemical reaction using ultraviolet light is used. Since short-wavelength laser light such as an excimer laser has a large energy per photon, a chemical bond forming a molecular skeleton can be cut.
[0005]
As described above, conventionally, fine processing has been enabled by selecting the wavelength, pulse width, and the like of the laser to be irradiated. However, much attention has not been paid to improving the material to be irradiated with the laser. Processing of glass, which is a transparent material, is important for optical applications. For example, in order to provide a glass suitable for laser processing, a technology has been disclosed in which silver is introduced into glass by ion exchange to reduce the laser processing threshold and provide a glass that is less likely to crack. (For example, see Patent Document 1).
[0006]
[Patent Document 1]
JP-A-11-217237
[Problems to be solved by the invention]
However, in a glass containing many alkali metals, although silver ions can be introduced into the inside by silver ion exchange, a phenomenon occurs in which silver ions are reduced near the glass surface and diffusion into the glass is inhibited. For this reason, the effective laser processing region is limited to the vicinity of the glass surface, and it is still difficult to process the inside of the glass by making a through hole in the glass plate. There is also a problem that the ion exchange rate is low and it is difficult to make the ions reach the inside of the glass.
[0008]
Further, there is a problem that the glass for laser processing manufactured by silver ion exchange has a large thermal expansion coefficient because it contains a large amount of alkali metals and alkaline earth metals. In laser processing, since heat is generated in the laser irradiation part, stress occurs due to a difference in thermal expansion between the laser irradiation part and the vicinity thereof, and deformation occurs. If the coefficient of thermal expansion of the glass is large, the size of the processed part changes during and after laser irradiation, so that the dimensional accuracy of the processed part may deteriorate.
[0009]
Further, it is generally desirable that the optical element has a small dimensional change caused by a temperature change. There is also a problem that the dimensional change as described above causes a characteristic change of the optical element.
In order to solve the above-mentioned problems, an object of the present invention is to provide a laser processing glass capable of laser processing down to the inside of the glass so as to penetrate the glass and having a smaller coefficient of thermal expansion as compared with the related art. .
[0010]
[Means for Solving the Problems]
The glass of the present invention can be processed by ablation or evaporation by the absorbed laser light energy.
The glass composition of the present invention satisfies the following conditions.
60 ≦ (SiO ₂ + B ₂ O ₃ ) ≦ 79 mol%
5 ≦ (Al ₂ O ₃ + TiO ₂ ) ≦ 20 mol%
5 ≦ (Li ₂ O + Na ₂ O + K ₂ O + Rb ₂ O + Cs ₂ O + MgO + CaO + SrO + BaO) ≦ 20 mol%
However, 5 ≦ TiO ₂ ≦ 20 mol%.
This glass for laser processing preferably contains titanium in the form of atoms, colloids or ions.
[0011]
In the glass having the above composition, SiO ₂ and B ₂ O ₃ are oxides for forming a network of glass and form a skeleton as glass. If the total amount of SiO ₂ and B ₂ O ₃ exceeds 79 mol%, it becomes difficult to melt the glass. Therefore, the total amount is preferably 79 mol% or less.
Further, the modified oxides Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O, Cs ₂ O, MgO, CaO, SrO, and BaO partially destroy the network structure of glass, and It is used to weaken the viscosity of water and to reduce the temperature gradient of viscosity. In order to facilitate this effect, the total amount of the modified oxide is preferably at least 5 mol%.
[0012]
Al ₂ O ₃ and TiO ₂ are intermediate oxides, and SiO ₂ and B ₂ O ₃ as network-forming oxides, and Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O as modifying oxides, Depending on the balance of Cs ₂ O, MgO, CaO, SrO, and BaO, both a network-forming oxide and a modifying oxide can be present in the glass. In particular, TiO ₂ is a component necessary for lowering the processing threshold value by laser, and is preferably 5 mol% or more.
If the total amount of Al ₂ O ₃ and TiO ₂ exceeds the total amount of the modified oxide, it is difficult to vitrify. Therefore, the total amount of Al ₂ O ₃ and TiO ₂ is preferably set to 20 mol% or less.
[0013]
Further, in the glass having the above composition, the components of SiO ₂ and B ₂ O ₃ which are network forming oxides are increased, and Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O, and Cs which are modified oxides are used. _By minimizing ₂ O, MgO, CaO, SrO, and BaO as much as possible, it was possible to reduce the coefficient of thermal expansion.
Thus, in order to increase the components of SiO ₂ and B ₂ O ₃ , which are network forming oxides, the total amount of SiO ₂ and B ₂ O ₃ is set to 60 mol% or more. In order to minimize the amount of the modified oxides Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O, Cs ₂ O, MgO, CaO, SrO, and BaO, the total amount thereof is 20 mol%. It was as follows.
[0014]
Within the above composition range,
(Al ₂ O ₃ + TiO ₂ ) / (Li ₂ O + Na ₂ O + K ₂ O + Rb ₂ O + Cs ₂ O + MgO + CaO + SrO + BaO) ≦ 0.9
Is desirable to obtain a more uniform glass by a general melting method.
[0015]
Further, the following range 70 ≦ (SiO ₂ + B ₂ O ₃ ) ≦ 79 mol%
10 ≦ TiO ₂ ≦ 15 mol%
10 ≦ Na ₂ O ≦ 15 mol%
A glass composition that satisfies the above condition is most desirable from the viewpoints of both reducing the coefficient of thermal expansion and improving laser workability.
[0016]
Here, the thermal expansion coefficient is further reduced by setting the total amount of SiO ₂ and B ₂ O ₃ as network forming oxides to 70 mol% or more and Na ₂ O as a modification oxide to 15 mol% or less. Can be done.
Further, by setting TiO ₂ , which is a component necessary for lowering the processing threshold value by laser, to 10 mol% or more, laser workability can be further improved. However, since the TiO ₂ is less likely to many vitrification than Na ₂ O is a modifying oxide, TiO ₂ is preferably 15 mol% or less.
In addition, since the total amount of SiO ₂ and B ₂ O ₃ that are network-forming oxides is 70 mol% or more, it is preferable that Na ₂ O that is a modification oxide is 10 mol% or more. This is because, by increasing the number of the modified oxides, the viscosity at a high temperature is reduced and the temperature gradient of the viscosity is reduced.
[0017]
When the laser beam is absorbed, a change in the glass structure or a change in the absorptance occurs, resulting in ablation or evaporation. The glass having the composition of the present invention has a low processing threshold because the energy required to cause the phenomenon and perform processing is small. In addition, the glass for laser processing of the present invention does not modify the glass by ion exchange or the like and obtains a necessary composition by melting, so that the glass can be made substantially uniform in the thickness direction. For this reason, it is possible to easily perform not only processing near the glass surface but also processing that reaches the inside of the glass, such as forming a through hole in the glass plate. Here, “substantially uniform in the thickness direction” means that the glass composition is uniform to such an extent that laser processing can be performed inside the glass.
[0018]
Further, the glass of the present invention preferably has a coefficient of thermal expansion of 100 × 10 ⁻⁷ ° C. ⁻¹ or less.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
An object of the present invention is to improve the laser workability of glass, and to perform processing with low energy from the glass surface to the inside. Therefore, it is necessary to produce a uniform glass. However, whether or not a uniform glass was produced was confirmed by actually performing melting, casting, and slow cooling.
[0020]
(Glass manufacturing method)
The raw materials were blended so that the glass to be produced was 200 g. After transferring this to a platinum crucible, it was thrown into a melting furnace heated to about 1500 ° C. and held for 6 hours. During the 6 hours, stirring was performed several times. Casting was carried out by pouring glass onto an iron plate, immediately put into a lehr where the temperature was raised to about 500 ° C., kept at a predetermined temperature for 30 minutes, and gradually cooled to room temperature over 16 hours. The glass block thus obtained was cut and polished by a general method to prepare a glass sample for laser processing having a plate-like and smooth surface.
[0021]
(Measurement of processing threshold value by laser irradiation)
Processing of the glass substrate by laser light irradiation was performed as follows using a laser light irradiation apparatus 1 as shown in FIG.
The laser light 10 emitted from the laser light source 12 is squeezed by a lens (not shown) and irradiates a glass sample 20 fixed to a sample holder 22 on a sample stage 24. The attenuator 50 is a device that changes the energy of the laser light passing therethrough, and can adjust the energy of the passing laser light 10 by operating a micrometer (not shown). The glass sample 20 is irradiated with the laser beam 10 whose energy has been adjusted by the attenuator 50.
[0022]
The sample stage 24 is a stage that can be freely moved three-dimensionally with one axis in a direction parallel to the optical axis of the laser light 10 and two axes in a plane perpendicular to the optical axis of the laser light 10. The movement of the sample stage 24 can be performed by an electric signal, and can be controlled as predetermined.
[0023]
Further, the sample holder 22 can be freely inclined with respect to the optical axis direction of the laser beam 10. By changing the laser light source 12, the type of the laser light 10 can be selected from the third harmonic (wavelength 355 nm), the fourth harmonic (wavelength 266 nm), and the KrF excimer laser (wavelength 248 nm) of the Nd: YAG laser. can do. The diameter or size of the laser beam was changed by inserting a mask (not shown) on the optical axis near the glass sample 20 as necessary.
[0024]
The processing threshold value was measured by a laser as follows. As the laser light 10, ultraviolet light of 266 nm and 355 nm wavelength of Nd: YAG laser was used. This laser has a repetition frequency of 20 Hz and a pulse width of 5 to 8 nm. The laser beam 10 was condensed by a lens (not shown) having a focal length of 100 mm, and was applied to a glass sample 20 fixed to a sample holder 22 on a sample stage 24. The irradiation time was controlled by the irradiation shutter 30 and was 2 seconds.
[0025]
The energy of the laser light 10 was measured by putting the power meter 40 in the optical path of the laser light 10 with the irradiation shutter 30 closed. This energy was variously changed by the attenuator 50 and the sample was irradiated.
[0026]
Since the laser light source 12 generates a high-energy beam, it is preferable that the laser light source 12 can be remotely operated to ensure safety, and the power supply / cooling water supply device 14 for the laser light source 12 is operated by the remote controller 16. Although not particularly shown, the laser light source 12 itself has a built-in shutter, which can also be remotely controlled. The laser light transmitted through the glass sample 20 is absorbed by the beam damper 18.
[0027]
(Measurement of thermal expansion coefficient)
The measurement of the thermal expansion coefficient was performed according to JIS R3103 of Japanese Industrial Standard.
[0028]
Hereinafter, examples using the present invention will be described, but the present invention is not limited to these examples.
[Example]
The compositions of Examples 1 to 12 of the glass for laser processing of the present invention are as shown in Table 1. The composition of each component is in the following range.
Network-forming oxide (SiO ₂ , B ₂ O ₃ ): 60 to 79 mol%
And intermediate oxide _{(Al 2 O 3, TiO 2} ): 5~20 mol%
However, TiO ₂ is essential to contain 5 to 20 mol%.
· Modifying oxides _{(Li 2 O, Na 2 O} , K 2 O, MgO, CaO, SrO, BaO): 5~20 mol%
The glass for laser processing according to the present invention is preferably substantially composed of only the above-described composition except for inevitable trace impurities.
[0029]
[Table 1]

[0030]
A laser beam having a wavelength of 266 nm or 355 nm was irradiated to the laser processing glass sample having the above composition while changing the irradiation energy. Table 1 shows the obtained processing threshold values.
It can be seen that in both cases, as the concentration of TiO ₂ increases, the processing threshold value decreases significantly. However, it hardly depends on the composition of the network forming oxide and the modifying oxide.
[0031]
FIG. 2 plots the relationship between the total amount of Al ₂ O ₃ and TiO _{2 and} the amount of Na ₂ O for various compositions tested by the inventors, and shows the vitrified state of each composition. From the figure, it can be seen that if the amount of the modified oxide typified by Na ₂ O is too small, phase separation and devitrification occur, so that a uniform glass cannot be produced. That is, in order to produce a uniform glass, the total amount of Al ₂ O ₃ and TiO _{2 and} the total amount of the modified oxide are:
(Al ₂ O ₃ + TiO ₂ ) / (Li ₂ O + Na ₂ O + K ₂ O + Rb ₂ O + Cs ₂ O + MgO + CaO + SrO + BaO) ≦ 0.9 (1)
Is preferably established.
[0032]
As described above, in order to lower the processing threshold value by laser, it is necessary to include a large amount of TiO _{2. In} such a case, the concentration of the modified oxide is increased to satisfy the condition of the above formula (1). Need to be done. However, when the concentration of the modified oxide is increased, the thermal expansion coefficient generally increases. Therefore, it can be seen that there is a trade-off between lowering the processing threshold value and lowering the thermal expansion coefficient.
[0033]
[Comparative example]
Comparative Example 1 is a so-called soda lime glass used for a normal window glass or the like. When the processing threshold value is obtained in the same manner as in the embodiment, it is found that the ablation or the evaporation occurs at both the maximum power of 1.10 W when the wavelength of the laser beam is 266 nm and the maximum power of 2.10 W when the wavelength of the laser beam is 355 nm. No change occurred in the sample. When the concentration of TiO ₂ is extremely low or the composition does not include TiO ₂ , the processing threshold becomes extremely high.
[0034]
As shown in Table 1, Comparative Example 2 is a material containing both TiO ₂ as an intermediate oxide and Na ₂ O as a modified oxide at a high concentration exceeding 20 mol%. When the processing threshold value was determined in the same manner as in the example, the laser light wavelength was extremely low, 15 mW at 266 nm, and 200 mW at 355 nm. However, the thermal expansion coefficient of each glass composition of the above-described embodiment is smaller than 100 × 10 ⁻⁷ ° C. ⁻¹ , whereas the glass of the composition of Comparative Example 2 has a thermal expansion coefficient of 118 × 10 ^−7. C- ¹ .
[0035]
In consideration of the above Examples and Comparative Examples, as a glass having a coefficient of thermal expansion as small as possible and having a low processing threshold, the glass satisfies the composition represented by Examples 11 and 12, ie, the condition of (1). It can be seen that the composition in the following range is most preferable.
70 ≦ (SiO ₂ + B ₂ O ₃ ) ≦ 79 mol%
10 ≦ TiO ₂ ≦ 15 mol%
10 ≦ Na ₂ O ≦ 15 mol%
[0036]
【The invention's effect】
According to the present invention, a laser processing glass having a low processing threshold value by laser irradiation and a small thermal expansion coefficient can be provided. In other words, the glass for laser processing of the present invention requires less laser light energy for processing and is less affected by heat, so that more precise processing can be performed.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an optical system for measuring a processing threshold value by laser irradiation.
FIG. 2 is a view showing a composition range in which a uniform glass can be produced.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 laser light irradiation device 10 laser light 12 laser light source 20 glass sample 22 sample holder 24 sample stage 30 irradiation shutter 40 power meter 50 attenuator

Claims (4)

In laser processing glass that can be laser processed by ablation or evaporation by absorbed laser light energy,
A glass for laser processing, wherein the composition of the glass satisfies the following conditions.
60 ≦ (SiO ₂ + B ₂ O ₃ ) ≦ 79 mol%
5 ≦ (Al ₂ O ₃ + TiO ₂ ) ≦ 20 mol%
5 ≦ (Li ₂ O + Na ₂ O + K ₂ O + Rb ₂ O + Cs ₂ O + MgO + CaO + SrO + BaO) ≦ 20 mol%
However, 5 ≦ TiO ₂ ≦ 20 mol%. The laser processing glass according to claim 1, wherein the composition satisfies the following condition.
(Al ₂ O ₃ + TiO ₂ ) / (Li ₂ O + Na ₂ O + K ₂ O + Rb ₂ O + Cs ₂ O + MgO + CaO + SrO + BaO) ≦ 0.9 The glass for laser processing according to claim 1, wherein the composition satisfies the following condition.
70 ≦ (SiO ₂ + B ₂ O ₃ ) ≦ 79 mol%
10 ≦ TiO ₂ ≦ 15 mol%
10 ≦ Na ₂ O ≦ 15 mol% The glass for laser processing according to claim 1, wherein a thermal expansion coefficient of the glass is 100 × 10 ⁻⁷ ° C. ⁻¹ or less. 5.

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