JP4405761B2 - Laser processing glass - Google Patents

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、ＴｉＯ₂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、Ａｌ₂Ｏ₃およびＴｉＯ₂の総量とＮａ₂Ｏ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Ｎａ₂Ｏ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、Ａｌ₂Ｏ₃およびＴｉＯ₂の総量と修飾酸化物の総量とは、
（Ａｌ₂Ｏ₃＋ＴｉＯ₂）／（Ｌｉ₂Ｏ＋Ｎａ₂Ｏ＋Ｋ₂Ｏ＋Ｒｂ₂Ｏ＋Ｃｓ₂Ｏ＋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、ＴｉＯ₂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。ＴｉＯ₂の濃度が極めて低いか、もしくはＴｉＯ₂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ＴｉＯ₂と修飾酸化物のＮａ₂Ｏ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。
【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]
BACKGROUND OF THE INVENTION
The present invention relates to a laser processing glass, and more particularly to a glass having a glass composition suitable for laser processing.
[0002]
[Prior art]
In recent years, material processing technology using the energy of laser light has been advanced to the area of fine processing.
In the processing technology using the mask pattern, the processable length is in the nanometer range, which is shorter than the micrometer, due to the development of the patterning technology and the shortening of the laser wavelength.
On the other hand, in direct processing using a laser, the pulse width of a laser beam is shortened and the wavelength is shortened. As a result, processing of an organic substance such as polyimide or metal is performed in a micrometer region.
[0003]
Further, processing such as drilling using a laser has progressed from thermal processing to ablation processing. Ablation is a phenomenon in which the material at the irradiated region is shifted from melting to evaporation within a short time by irradiating laser light with an extremely narrow pulse width. The degree of thermal influence on the periphery of the beam irradiation site varies depending on the length of the pulse width. In processing using an ultrashort pulse laser in which irradiation of the beam is finished before thermal diffusion occurs, precise and fine drilling can be performed with almost no heat-affected layer.
[0004]
However, most of lasers used in actual processing have a pulse width of nanosecond order or more, and the influence of heat is unavoidable. Therefore, photochemical reaction using ultraviolet light is used. A short-wavelength laser beam such as an excimer laser has a large energy per photon, and thus can break a chemical bond forming a molecular skeleton.
[0005]
As described above, conventionally, fine processing has been made possible by selecting the wavelength of the laser to be irradiated, the pulse width, and the like. However, in view of improving the material to be irradiated with the laser, less studies have been made. 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 technique is disclosed in which silver is introduced into the glass by ion exchange, thereby reducing the laser processing threshold and providing a glass that is less susceptible to cracking. (For example, refer to Patent Document 1).
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 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, silver ions are reduced in the vicinity of the glass surface and diffusion into the glass is inhibited. For this reason, an 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 such as making a through hole in the glass plate. Moreover, there was also a problem that the ion exchange rate was slow and it was difficult to make ions reach the inside of the glass.
[0008]
Moreover, the glass for laser processing produced by silver ion exchange has a problem that its thermal expansion coefficient is large because it contains a large amount of alkali metals and alkaline earth metals. In laser processing, since heat is generated in the laser irradiation portion, a stress due to a difference in thermal expansion occurs in the laser irradiation portion and the vicinity thereof, and deformation occurs. If the thermal expansion coefficient of glass is large, the size of the processed part changes during and after the laser irradiation, and the dimensional accuracy of the processed part may deteriorate.
[0009]
In addition, it is generally desirable for the optical element to have a small dimensional change caused by a temperature change. There is also a problem that the dimensional change as described above causes the characteristic variation of the optical element.
In order to solve the above problems, an object of the present invention is to provide a glass for laser processing capable of laser processing leading to the inside of the glass so as to penetrate through the glass and having a smaller thermal expansion coefficient than the conventional one. .
[0010]
[Means for Solving the Problems]
The glass of the present invention can be processed by ablation or evaporation with absorbed laser light energy.
The glass composition of the present invention satisfies the following conditions.
70 ≦ (SiO ₂ + B ₂ O ₃ ) ≦ 75 mol%
60 ≦ SiO ₂ ≦ 65 mol%
12.5 ≦ TiO ₂ ≦ 15 mol%
12.5 ≦ Na ₂ O ≦ 15 mol%
This laser processing glass 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 glass network-forming oxides 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.
In addition, Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O, Cs ₂ O, MgO, CaO, SrO, or BaO, which are modified oxides, partially destroy the glass network structure. It is used to weaken the viscosity of the glass and to loosen the temperature gradient of the viscosity. In order to make this effect appear easily, the total amount of the modified oxide is preferably 5 mol% or more.
[0012]
Al ₂ O ₃ and TiO ₂ are intermediate oxides, network forming oxides SiO ₂ and B ₂ O ₃ , and modified oxides Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O, Depending on the balance of Cs ₂ O, MgO, CaO, SrO and BaO, both network-forming oxides and modified oxides can be present in the glass. In particular, TiO ₂ is a component necessary for lowering the processing threshold by the laser, and is preferably 5 mol% or more.
Further, since the Al ₂ O ₃ and the total amount of TiO ₂ is less likely to total more than the amount the glass of the modifying oxide, the total amount of Al ₂ O ₃ and TiO ₂ is preferably 20 mol% or less.
[0013]
Further, in the glass having the above composition, the components of the network forming oxides SiO ₂ and B ₂ O ₃ are increased, and the modified oxides Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O, Cs. _{By making 2} O, MgO, CaO, SrO, and BaO as small as possible, it was possible to reduce the thermal expansion coefficient.
In order to increase in this manner components of SiO ₂ and B ₂ O ₃ is a network forming oxide, the total amount of SiO ₂ and B ₂ O ₃ was 60 mol% or more. Further, in order to minimize 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 of these 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
It is desirable to satisfy the above condition in order 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 satisfying the above conditions is most desirable from the viewpoints of both reducing the thermal expansion coefficient and improving laser processability.
[0016]
Here, by making the total amount of SiO ₂ and B ₂ O ₃ which are network forming oxides 70 mol% or more and Na ₂ O which is a modified oxide 15 mol% or less, the thermal expansion coefficient is further reduced. Can be made.
Further, the laser workability can be further improved by setting TiO ₂ , which is a component necessary for lowering the laser processing threshold, to 10 mol% or more. However, if the amount of TiO ₂ is larger than that of Na ₂ O, which is a modified oxide, it is difficult to vitrify, so TiO ₂ is preferably 15 mol% or less.
Further, since the total amount of SiO ₂ and B ₂ O ₃ which are network forming oxides is 70 mol% or more, it is preferable that Na ₂ O which is a modified oxide is 10 mol% or more. This is because by increasing the amount of the modified oxide, the viscosity at high temperature is weakened and the temperature gradient of the viscosity is relaxed.
[0017]
When the laser beam is absorbed, the glass structure changes or the absorption rate changes, resulting in ablation or evaporation. The glass of the composition of the present invention has a low processing threshold because the energy required to cause the phenomenon and to perform processing is small. Further, the glass for laser processing of the present invention can be made substantially uniform in the thickness direction because it does not modify the glass by ion exchange or the like, and obtains a necessary composition by melting. For this reason, it is not limited to processing near the glass surface, and processing extending to the inside of the glass such as opening a through hole in the glass plate can be easily performed. Here, “substantially uniform in the thickness direction” means that the glass composition is uniform to such an extent that laser processing can be performed up to the inside of the glass.
[0018]
The glass of the present invention preferably has a thermal expansion coefficient of 100 × 10 ⁻⁷ ° C. ⁻¹ or less.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
An object of the present invention is to improve the laser processability of glass, and further, processing with low energy can be performed from the glass surface to the inside. Therefore, it is necessary to produce a uniform glass, but whether or not a uniform glass can be produced was confirmed by actually melting, casting and slow cooling.
[0020]
(Glass manufacturing method)
The raw materials were mixed so that the glass to be produced was 200 g. After transferring this to a platinum crucible, it was put into a melting furnace heated to about 1500 ° C. and held for 6 hours. Stirring was performed several times during these 6 hours. Casting was performed by pouring glass onto an iron plate, and immediately putting into a slow cooling furnace heated to about 500 ° C., maintaining at a predetermined temperature for 30 minutes, and then gradually cooling to room temperature over 16 hours. The glass block thus obtained was cut and polished by a general method to prepare a plate-shaped glass sample for laser processing having a smooth surface.
[0021]
(Measurement of processing threshold 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 focused by a lens (not shown) and irradiated onto the glass sample 20 fixed to the sample holder 22 on the sample stage 24. The attenuator 50 is a device that changes the energy of the laser beam that passes through the attenuator 50. The energy of the laser beam 10 that passes through the attenuator 50 can be adjusted by operating a micrometer (not shown). The glass sample 20 is irradiated with the laser beam 10 whose energy is adjusted by the attenuator 50.
[0022]
The sample stage 24 is a stage that can be freely moved three-dimensionally in one axis in a direction parallel to the optical axis of the laser beam 10 and two axes in a plane perpendicular to the optical axis of the laser beam 10. The movement of the sample stage 24 can be performed by an electric signal and can be controlled as determined in advance.
[0023]
The sample holder 22 can be freely tilted with respect to the optical axis direction of the laser beam 10. The type of laser beam 10 is selected by changing the laser light source 12 to select the third harmonic (wavelength 355 nm), fourth harmonic (wavelength 266 nm) and KrF excimer laser (wavelength 248 nm) of the Nd: YAG laser. can do. Further, the diameter or size of the laser beam was changed by putting a mask (not shown) on the optical axis near the glass sample 20 as required.
[0024]
Measurement of the processing threshold by laser was performed as follows. As the laser light 10, ultraviolet light having a wavelength of 266 nm and 355 nm of an Nd: YAG laser was used. The repetition frequency of this laser is 20 Hz, and the pulse width is 5 to 8 nm. The laser beam 10 was collected by a lens (not shown) having a focal length of 100 mm, and irradiated onto the glass sample 20 fixed to the sample holder 22 on the sample stage 24. The irradiation time was controlled by the irradiation shutter 30 and was 2 seconds.
[0025]
The energy of the laser beam 10 was measured by putting the power meter 40 in the optical path of the laser beam 10 with the irradiation shutter 30 closed. The energy was variously changed by the attenuator 50, and the sample was irradiated. The energy at the limit at which ablation occurred was obtained and used as a processing threshold.
[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 / cooling water supply device 14 to the laser light source 12 is operated by the remote controller 16. Although not specifically shown, the laser light source 12 itself has a built-in shutter, which can also be remotely operated. Further, the laser light transmitted through the glass sample 20 is absorbed by the beam damper 18.
[0027]
(Measurement of thermal expansion coefficient)
The thermal expansion coefficient was measured according to JIS R3103 of Japanese Industrial Standard.
[0028]
Examples of the present invention will be described below, but the present invention is not limited to these examples.
[Example]
Les chromatography The machining reference examples 1 to 10 of the glass, the composition of Examples 1 and 2 are shown in Table 1.
The composition of each component is in the following range.
- network-forming oxides _{(SiO 2, B 2 O 3} ): 60~79 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): 5~2
0 mol%
The glass for laser processing is preferably substantially composed of the above composition except for unavoidable trace amounts of impurities.
[0029]
[Table 1]

[0030]
The laser processing glass sample having the above composition was irradiated with laser beams having wavelengths of 266 nm and 355 nm while changing the irradiation energy. Table 1 shows the processing threshold values obtained as a result.
It can be seen that for both wavelengths, the processing threshold decreases significantly as the concentration of TiO ₂ increases. However, it hardly depends on the composition of the network-forming oxide or the modified 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 vitrification 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 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)
It is preferable that this relationship is established.
[0032]
As described above, in order to lower the processing threshold by laser, it is necessary to contain a large amount of TiO _{2. In} this case, the concentration of the modified oxide is increased to satisfy the condition of the above formula (1). It is necessary to let However, when the concentration of the modified oxide is increased, the coefficient of thermal expansion generally increases, so it can be seen that there is a trade-off relationship between lowering the processing threshold and lowering the coefficient of thermal expansion.
[0033]
[Comparative example]
Comparative Example 1 is so-called soda lime glass used for ordinary window glass and the like. When the processing threshold value is obtained in the same manner as in the example, the ablation or evaporation is performed at both the maximum power of 1.10 W when the laser beam wavelength is 266 nm and the maximum power of 2.10 W when the laser beam wavelength is 355 nm. The sample did not change. When the TiO ₂ concentration is very low or the composition does not contain TiO ₂ , the processing threshold is 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 was determined in the same manner as in the example, the laser light wavelength was 266 nm and 15 mW, and the laser light wavelength was 355 nm and 200 mW, which were extremely low values. However, the thermal expansion coefficient of each glass composition of the above-described example 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 ℃ ^-1 and larger.
[0036]
【The invention's effect】
According to the present invention, it is possible to provide a glass for laser processing having a low processing threshold by laser irradiation and a low thermal expansion coefficient. That is, the glass for laser processing according to the present invention requires less laser light energy for processing and is less affected by heat, and therefore can perform more precise processing.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an optical system for measuring a processing threshold by laser irradiation.
FIG. 2 is a diagram showing a composition range in which uniform glass can be produced.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser beam irradiation apparatus 10 Laser beam 12 Laser light source 20 Glass sample 22 Sample holder 24 Sample stage 30 Irradiation shutter 40 Power meter 50 Attenuator

Claims (3)

In laser processing glass that can be laser processed by ablation or evaporation with absorbed laser light energy,
A glass for laser processing, wherein the glass composition satisfies the following conditions.
70 ≦ (SiO ₂ + B ₂ O ₃ ) ≦ 75 mol%
60 ≦ SiO ₂ ≦ 65 mol%
12.5 ≦ TiO ₂ ≦ 15 mol%
12.5 ≦ Na ₂ O ≦ 15 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 Laser processing glass according to claim 1 or 2, wherein the thermal expansion coefficient of the glass is 75 × 10 ^-7 ℃ ^-1 or less.

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