JP2005067908A - Glass for laser beam machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide glass for laser beam machining, which is laser beam-machined not only to the vicinity of the surface but to the inside of the glass in the laser beam machining using ablation or the vaporization induced by the absorption of the laser beam. <P>SOLUTION: Glass containing at least one kind of an element of iron, cerium and tin is suitable as the glass for leaser beam machining which is laser beam machined up to the inside of the glass. In the glass having such a compositional feature, glass having 0.5-9 mol% expressed in terms of Fe<SB>2</SB>O<SB>3</SB>in the composition, glass having 1-9 mol% cerium expressed in terms of CeO<SB>2</SB>or glass having 1-5 mol% SnO<SB>2</SB>expressed in terms of SnO<SB>2</SB>in the composition are particularly suitable for the laser beam machining. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００１８】
【表２】

【００１９】
【表３】

【００２０】
〔試料の作製〕
作製するガラスが約４００ｇになるように原材料の調合を行った。これを白金製の坩堝に移した後、１４５０℃に昇温した溶融炉内に投入し、融液の攪拌を適宜行いながら５〜６時間保持した。この後、融液を鉄板上の型内に流し出し、これを直ちに５３０℃前後に昇温した徐冷炉に投入し、１６時間かけて室温まで徐冷した。このようにして得られたガラスブロックを一般的な方法にて切断、研磨し、両表面が平滑なガラス板をレーザ加工試験用のガラス試料とした。
【００２１】
なお、組成中のＮａ_２Ｏの原料としてはＮａ_２ＣＯ_３試薬を用いたが、試料の一部は、Ｎａ_２ＣＯ_３総量の一部を酸化剤であるＮａＮＯ_３およびＮａ_２ＳＯ_４試薬に置換し、酸化雰囲気下において作製した（実施例３、５、７、１１）。また、バッチに少量のカーボンを加え、溶融条件を還元雰囲気とした試料も作製した（実施例４、６、９、１３）。
【００２２】
〔レーザ照射実験〕
試料へのレーザ照射は図１に示すレーザ加工用装置１００を用いて行った。照射レーザ光１として、Ｎｄ：ＹＡＧレーザの第４高調波（波長：２６６ｎｍ）を用いた。レーザ光源２から繰り返し周波数２０Ｈｚ，パルス幅５〜８ｎｓのレーザ光を供給した。
【００２３】
試料１２へのレーザ光未照射時にはミラー３を光路内に挿入し、レーザ光１を反射させてダンパー４により吸収させた。一方向の偏光のみを通すグランレーザプリズム５は、第４高調波とは異なる偏光方向を持つ第２高調波（５３２ｎｍ）を除去するために挿入している。レーザ光強度を調節するためのアッテネータ６を通過したレーザ光１の強度をパワーメータ７により測定した。
【００２４】
試料１２に対してレーザ光１を照射する際は、パワーメータ７は光路から除く必要がある。遠隔操作可能なレーザビームシャッタ８は、試料１２へのレーザ照射開始時に開、照射終了時に閉とする。シャッタ８が開のときにこれを通過したレーザ光１は、焦点距離１０ｃｍのレンズ９で集光され、ＸＹＺステージ１０に連結された試料ホルダ１１に固定された試料１２の表面に対して、垂直方向に照射された。
【００２５】
〔加工速度および加工しきい値の算出〕
レーザフルエンスを加工しきい値Ｆ_ｔｈ以上に設定し、図１に示すＸＹＺステージ１０を光軸に垂直な平面内において一定速度で直線的に移動させながら試料１２にレーザ光を照射させることにより、試料表面に溝が形成される。レーザ繰り返し周波数、ステージ移動速度、およびレーザスポット径は既知であるから、これらの値より、溝の任意の箇所あたりのレーザショット数を算出することができる。
【００２６】
ここに、レーザ繰り返し周波数およびレーザスポット径は、レーザパワー等その他実験諸条件に拘わらず、このレーザ加工実験を通じて一定である。このため、ステージ移動速度の異なる条件下でレーザ照射実験を繰り返すことにより、一箇所あたりレーザショット数の異なる溝を試料表面に形成することができる。
【００２７】
所定のレーザフルエンス条件の下、ステージ移動速度を様々に変化させた上記溝加工実験を行えば、加工深さ（溝深さ）のレーザショット数依存性を知ることができる。ここに、通常、加工深さはレーザショット数にほぼ比例するため、この傾きから、１ショットあたりの加工深さ、すなわち加工速度Δｈが求められる。なお、本実施例では、１本の溝に対して数十箇所の断面形状を三次元形状測定器により測定し、それらの平均を加工深さとした。
【００２８】
上記方法により、様々なレーザフルエンス条件において加工速度Δｈが求められれば、加工速度のレーザフルエンス依存性を知ることができる。同依存性は、理論上、次の（１）式に従うことが知られている。
Δｈ＝α^−１×ｌｎ（Ｆ／Ｆ_ｔｈ） （１）
ここに、Δｈは加工速度であり、レーザパルス１ショットあたりの加工深さに相当する。αは照射レーザ波長における物質の吸収係数である。本実施形態では、測定結果に対して（１）式を適用し、最小２乗法によるフィッティングを行って、物質固有の吸収係数αおよび未知数である加工しきい値Ｆ_ｔｈを算出した。
【００２９】
〔評価結果〕
図２、図３および図４に、加工速度のＦｅ_２Ｏ_３、ＣｅＯ_２およびＳｎＯ_２含有量依存性を示す。加工速度はレーザフルエンスが７．８Ｊ／ｃｍ^２での値である。
【００３０】
図２より明らかなように、Ｆｅを含有するガラスにおいて最も速い加工速度を得るには、Ｆｅ_２Ｏ_３の含有量を１〜２モル％程度とすることが望ましい。
【００３１】
一方、Ｃｅを含有するガラスの場合は、図３より、加工速度がＣｅＯ_２含有量の増加と共に単調に増大することが分かる。したがって、Ｃｅを含有するガラスの加工においてより速い加工速度を得るには、できるだけＣｅＯ_２含有量の多いガラスを被加工物として用いることが望ましく、具体的には、含有量９モル％程度のガラスを用いることが望ましい。
【００３２】
Ｓｎを含有するガラスでは、図４より、ＳｎＯ_２含有量の増加と共に加工速度は徐々に減少することが分かる。ＦｅあるいはＣｅを含有するガラスと比較してＳｎ含有ガラスの加工速度は遅いが、Ｓｎ含有ガラスにおいてできるだけ速い加工速度を得るためには、ＳｎＯ_２含有量を１モル％程度とすることが望ましい。
【００３３】
図５、図６および図７に、加工しきい値のＦｅ_２Ｏ_３、ＣｅＯ_２およびＳｎＯ_２含有量依存性を示す。
【００３４】
Ｆｅを含有するガラスでは、図５より、Ｆｅ_２Ｏ_３の含有量を１〜２モル％程度としたガラスにおいて最も低い加工しきい値が得られる。したがって、最も低い加工しきい値、最も速い加工速度という両特性を得るためには、望ましくはＦｅ_２Ｏ_３の含有量を１〜２モル％程度に調整することが好ましい。
【００３５】
Ｃｅを含有するガラスの場合は、図６より、加工しきい値がＣｅＯ_２含有量の増加と共にほぼ単調に増大することが分かる。したがって、Ｃｅを含有するガラスの加工においてより低い加工しきい値を得るには、できるだけＣｅＯ_２含有量の少ないガラスを被加工物として用いることが望ましく、具体的には、含有量１モル％程度のガラスを用いることが望ましい。
【００３６】
なお、図３から、より速い加工速度を得るためには、より高濃度にＣｅＯ_２を含有したガラスを用いることが望ましいことが分かっている。このように、Ｃｅを含有するガラスでは、加工速度を最速とするＣｅＯ_２含有量条件と、加工しきい値を最低とするＣｅＯ_２含有量条件が異なることに注意する必要がある。当然のことながら、加工目的や加工仕様に合わせて、適当なＣｅＯ_２含有量を有するガラスを選択することに何ら問題はない。例えば、加工速度が遅くとも弱いレーザパワーで加工したい場合には、ＣｅＯ_２をできるだけ１モル％近くまで低濃度に含有するガラスを用いるとよい。また、中程度の加工しきい値、中程度の加工速度を必要とするならば、例えば、ＣｅＯ_２含有量を５モル％程度に調整してもよい。
【００３７】
ＦｅあるいはＣｅを含有するガラスと比較して、図７より、Ｓｎ含有ガラスの加工しきい値は比較的低いことが分かる。また、Ｓｎ含有ガラスの加工しきい値は、ＳｎＯ_２含有量に対して大きくは変化しない。図４より、加工速度のＳｎＯ_２含有量依存性も比較的小さいため、Ｓｎ含有ガラスを用いる場合には、屈折率や光透過率、熱膨張係数など、特にレーザ加工性以外の物性に注目して、より望ましいガラス組成を選択することもできる。
【００３８】
以上のように、表１〜表３に示した全てのガラスでレーザ加工が可能なことを確認した。すなわち、Ｆｅ、Ｃｅ、Ｓｎのうち、少なくとも一種類の元素が含有されたガラスは、レーザ照射により加工が可能なことが分かった。この際のＦｅ、Ｃｅ、Ｓｎの含有量は、それぞれ、Ｆｅ_２Ｏ_３換算で０．５〜９モル％、ＣｅＯ_２換算で１〜９モル％、ＳｎＯ_２換算で１〜５モル％である。
【００３９】
なお、ガラス中では、鉄は２価と３価の両状態が存在し、その割合は、組成や溶融条件によって変化することが知られている。一般に、２価鉄の主な吸収は１μｍ付近にあるので、２価鉄の存在は紫外レーザ光の吸収に寄与しない、あるいは寄与が少ないと考えられる。このことを考慮すれば、加工しきい値と加工速度は、３価鉄の量にのみ左右されると予想できる。
【００４０】
ホストガラスに加えられた全ての酸化鉄をＦｅ_２Ｏ_３としたときの全鉄量（一般にＴ−Ｆｅ_２Ｏ_３と表される）から、分析によって得られたＦｅＯ量を差し引き、ガラス中の三酸化二鉄Ｆｅ_２Ｏ_３のモル比を算出した。この値と加工速度および加工しきい値との相関を調べた結果を、それぞれ図８および図９に示す。これらをそれぞれ図２および図５と比較すると、両者の傾向はそれ程大きくは変わらないことが分かる。
【００４１】
すなわち、原理的には、加工しきい値および加工速度は、ガラス中の三酸化二鉄Ｆｅ_２Ｏ_３の量に依存すると考えられるが、実用上は、全鉄量Ｔ−Ｆｅ_２Ｏ_３から、加工しきい値あるいは加工速度を近似的に予想して組成設計しても問題がないといえる。ただし、溶融条件をコントロールすることによって２価鉄と３価鉄量の割合を変化させ、レーザ加工性の微調整を行うような組成設計を行ってもよい。
【００４２】
【発明の効果】
本発明により、ガラス表面近傍のみならず、ガラス内部に至るレーザ加工をも行うことが可能なレーザ加工用ガラスが提供できる。これらは低い加工しきい値を有するため、レーザ加工に要するレーザエネルギー投入量を小さくすることができる。
【図面の簡単な説明】
【図１】レーザ加工用の装置を示す模式図。
【図２】加工速度のＦｅ_２Ｏ_３含有量依存性を示す図。
【図３】加工速度のＣｅＯ_２含有量依存性を示す図。
【図４】加工速度のＳｎＯ_２含有量依存性を示す図。
【図５】加工しきい値のＦｅ_２Ｏ_３含有量依存性を示す図。
【図６】加工しきい値のＣｅＯ_２含有量依存性を示す図。
【図７】加工しきい値のＳｎＯ_２含有量依存性を示す図。
【図８】加工速度の三酸化二鉄Ｆｅ_２Ｏ_３含有量依存性を示す図。
【図９】加工しきい値の三酸化二鉄Ｆｅ_２Ｏ_３含有量依存性を示す図。
【符号の説明】
１ レーザ光
２ レーザ光源
３ ミラー
４ ダンパー
５ グランレーザプリズム
６ アッテネータ
７ パワーメータ
８ シャッタ
９ レンズ
１０ ＸＹＺステージ
１１ 試料ホルダ
１２ 試料
１００ レーザ加工用装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a glass for laser processing, and particularly to a glass composition suitable for laser processing.
[0002]
[Prior art]
When a solid material is irradiated with laser light having a pulse width of nanoseconds or less, the decomposition product evaporates with strong light emission and impact sound. This phenomenon is called laser ablation or simply ablation. Since this phenomenon is induced within an extremely short laser irradiation time, that is, within the time of the pulse width of the laser, when applied as a material processing process, it is possible to suppress processing roughness due to thermal damage around the laser irradiation portion. For this reason, in recent years, it has been widely used especially for precision fine processing of metals and organic substances.
[0003]
Glass as a workpiece is a material that is generally difficult to precisely process by ablation due to its brittleness. However, in recent years when the importance of glass materials in optical communication systems, such as optical fibers, planar optical waveguides, and microlenses, has been widely recognized, the need for precision microfabrication technology for glass is increasing.
In order to ablate transparent glass in a wide wavelength region, it is generally desirable to use a pulsed laser that oscillates ultraviolet light. This is because the ablation process requires an efficient interaction (absorption of laser light) between light and a substance. Ultraviolet pulse lasers currently include excimer lasers, third and fourth harmonic lasers of Nd: YAG lasers, and the like. Various properties of these laser light sources for processing, such as pulse width, intensity stability, output, beam shape, and the like greatly affect the workability of the material. In this regard, the recent performance improvement of laser light sources has been remarkable, and at present, stable and high-power nanosecond pulses can be obtained even in relatively small devices.
[0004]
As described above, the performance improvement of the “machining laser” has been remarkable in recent years, but on the other hand, “improvement of glass workability” has hardly been studied from the viewpoint of “improvement of the workpiece”. However, it can be processed even with a weak laser power (that is, the processing threshold is low), it can be processed quickly, it is not broken by the impact of a pulse laser, and the periphery of the processed part is not rough. Will be widely applied to optical components with precise and fine structures. In addition, since “laser processing glass” has higher laser processability than general glass, the same processing can be performed at low cost.
[0005]
From the above viewpoint, the present inventors have started research and development aimed at providing glass suitable for laser processing, and so far have invented a glass in which silver is introduced in the vicinity of the glass surface by ion exchange. (For example, refer to Patent Document 1). This ion exchange glass is produced by immersing the glass in a molten salt containing silver and exchanging silver ions in the molten salt with ions in the glass. Since silver ions or silver colloids introduced in the vicinity of the glass surface efficiently absorb ultraviolet light, good ablation processing can be performed even with a relatively low power laser.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-217237
[Problems to be solved by the invention]
However, the ion exchange glass has the following problems when considered as a material for laser processing.
[0008]
That is, with ion exchange glass, it is difficult to process the inside of the glass, such as through holes. This is because the absorption center of ultraviolet light such as silver ions and silver colloid is concentrated in the vicinity of the glass surface, so that the effective laser processing region is limited to the vicinity of the glass surface. In order to distribute the ultraviolet light absorption component to the inside of the glass, although it depends on the ion exchange rate and the thickness of the mother glass, usually an extremely long ion exchange treatment is required. Therefore, in order to meet such processing requirements, it is desirable to provide a glass in which components that absorb ultraviolet light are uniformly distributed throughout the glass.
[0009]
The present invention has been made paying attention to such conventional problems. The object is to provide a glass for laser processing that is easy for laser processing not only in the vicinity of the glass surface but also into the inside of the glass. Here, the glass for laser processing in the present invention is a glass in which a component that absorbs ultraviolet light is uniformly dispersed throughout the glass, and does not include the above-described ion exchange glass. For this reason, laser processing not only near the glass surface but also into the glass can be easily performed.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the invention described in claim 1 is a glass for laser processing used for laser processing utilizing ablation or evaporation induced by absorption of laser light.
The gist of the invention is that the glass contains at least one element of iron, cerium, and tin.
[0011]
As described above, when at least one element of iron, cerium, and tin is contained in the glass, the energy of the laser beam is absorbed by the element, so that laser processing that reaches the inside of the glass can also be performed. .
[0012]
The gist of the invention of claim 2 is that, in the laser processing glass of claim 1, the iron content is 0.5 to 9 mol% in terms of Fe ₂ O ₃ .
[0013]
According to a third aspect of the invention, the glass for laser processing according to claim 1, and summarized in that the content of the cerium is 1-9 mol% in terms of CeO _2.
[0014]
According to a fourth aspect of the invention, the glass for laser processing according to claim 1, and summarized in that the content of the tin is from 1 to 5 mol% in terms of SnO _2.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail.
As a composition of the host glass, 74SiO ₂ + 10CaO + 16Na ₂ O, which is one of typical compositions of soda lime glass, was used as an example. Here, the numerical values in the composition are expressed in mol%. This was doped with either Fe ₂ O ₃ , CeO ₂ or SnO ₂ as a light absorbing component to obtain a glass sample for laser processing.
[0016]
Table shows 1 in the _Fe 2 _{O 3} content of the glass samples doped with _Fe 2 _{O 3} in mole percent. Similarly, the CeO ₂ content of the glass samples doped with CeO ₂ in Table 2 shows the content of SnO ₂ in the glass sample doped with SnO ₂ in Table 3. As shown in Tables 1 to 3, each content is 0.5 to 9.1 mol% Fe ₂ O ₃ , 1.0 to 9.1 mol% CeO ₂ , and 1.0 to SnO _2. 4.8 mol%.
[0017]
[Table 1]

[0018]
[Table 2]

[0019]
[Table 3]

[0020]
[Sample preparation]
The raw materials were mixed so that the glass to be produced was about 400 g. After transferring this to a platinum crucible, it was put into a melting furnace heated to 1450 ° C. and held for 5 to 6 hours while appropriately stirring the melt. Thereafter, the melt was poured into a mold on an iron plate and immediately put into a slow cooling furnace heated to around 530 ° C., and gradually cooled to room temperature over 16 hours. The glass block thus obtained was cut and polished by a general method, and a glass plate having smooth surfaces was used as a glass sample for a laser processing test.
[0021]
Although Na ₂ CO ₃ reagent was used as a raw material for Na ₂ O in the composition, a part of the total amount of Na ₂ CO ₃ was used as an oxidizing agent for NaNO ₃ and Na ₂ SO ₄ reagents. Substitution was made in an oxidizing atmosphere (Examples 3, 5, 7, and 11). Samples were also prepared in which a small amount of carbon was added to the batch and the melting conditions were reduced (Examples 4, 6, 9, and 13).
[0022]
[Laser irradiation experiment]
Laser irradiation of the sample was performed using a laser processing apparatus 100 shown in FIG. As the irradiation laser beam 1, a fourth harmonic (wavelength: 266 nm) of an Nd: YAG laser was used. Laser light having a repetition frequency of 20 Hz and a pulse width of 5 to 8 ns was supplied from the laser light source 2.
[0023]
When the sample 12 was not irradiated with the laser beam, the mirror 3 was inserted into the optical path, and the laser beam 1 was reflected and absorbed by the damper 4. The Glan laser prism 5 that passes only polarized light in one direction is inserted to remove the second harmonic (532 nm) having a polarization direction different from the fourth harmonic. The intensity of the laser beam 1 that passed through the attenuator 6 for adjusting the laser beam intensity was measured by a power meter 7.
[0024]
When irradiating the sample 12 with the laser beam 1, the power meter 7 needs to be removed from the optical path. The remotely operable laser beam shutter 8 is opened at the start of laser irradiation of the sample 12 and closed at the end of irradiation. The laser beam 1 that has passed through the shutter 8 when it is open is collected by a lens 9 having a focal length of 10 cm, and is perpendicular to the surface of the sample 12 fixed to the sample holder 11 connected to the XYZ stage 10. Irradiated in the direction.
[0025]
[Calculation of machining speed and machining threshold]
By setting the laser fluence to be equal to or greater than the processing threshold _Fth and irradiating the sample 12 with laser light while linearly moving the XYZ stage 10 shown in FIG. 1 in a plane perpendicular to the optical axis, Grooves are formed on the sample surface. Since the laser repetition frequency, stage moving speed, and laser spot diameter are known, the number of laser shots per arbitrary location in the groove can be calculated from these values.
[0026]
Here, the laser repetition frequency and the laser spot diameter are constant throughout the laser processing experiment regardless of other experimental conditions such as the laser power. For this reason, by repeating the laser irradiation experiment under conditions with different stage moving speeds, grooves having different numbers of laser shots per location can be formed on the sample surface.
[0027]
If the groove processing experiment is performed with the stage moving speed varied under a predetermined laser fluence condition, the dependency of the processing depth (groove depth) on the number of laser shots can be known. Here, since the processing depth is generally proportional to the number of laser shots, the processing depth per shot, that is, the processing speed Δh is obtained from this inclination. In this example, several tens of cross-sectional shapes with respect to one groove were measured with a three-dimensional shape measuring instrument, and the average of them was taken as the processing depth.
[0028]
If the processing speed Δh is obtained under various laser fluence conditions by the above method, the dependency of the processing speed on the laser fluence can be known. It is known that the dependence depends on the following equation (1) in theory.
Δh = α ⁻¹ × ln (F / F _th ) (1)
Here, Δh is a processing speed and corresponds to the processing depth per one shot of the laser pulse. α is the absorption coefficient of the substance at the irradiation laser wavelength. In this embodiment, the equation (1) is applied to the measurement result, and fitting by the least square method is performed to calculate the absorption coefficient α specific to the substance and the processing threshold F _th that is an unknown.
[0029]
〔Evaluation results〕
2, 3 and 4 show the dependence of the processing speed on the content of Fe ₂ O ₃ , CeO ₂ and SnO ₂ . The processing speed is a value at a laser fluence of 7.8 J / cm ² .
[0030]
As is clear from FIG. 2, in order to obtain the fastest processing speed in the glass containing Fe, it is desirable that the content of Fe ₂ O ₃ is about 1 to 2 mol%.
[0031]
On the other hand, in the case of glass containing Ce, it can be seen from FIG. 3 that the processing speed monotonously increases with an increase in CeO ₂ content. Therefore, in order to obtain a higher processing speed in processing of Ce-containing glass, it is desirable to use glass having a CeO ₂ content as high as possible as a workpiece, and specifically, a glass having a content of about 9 mol%. It is desirable to use
[0032]
In the glass containing Sn, it can be seen from FIG. 4 that the processing speed gradually decreases as the SnO ₂ content increases. Although the processing speed of Sn-containing glass is slower than that of glass containing Fe or Ce, in order to obtain the highest possible processing speed in Sn-containing glass, the SnO ₂ content is preferably about 1 mol%.
[0033]
5, FIG. 6 and FIG. 7 show the dependence of the processing threshold on the content of Fe ₂ O ₃ , CeO ₂ and SnO ₂ .
[0034]
In the glass containing Fe, the lowest processing threshold value is obtained in FIG. 5 in the glass in which the content of Fe ₂ O ₃ is about 1 to 2 mol%. Therefore, in order to obtain both characteristics of the lowest processing threshold and the fastest processing speed, it is preferable to adjust the content of Fe ₂ O ₃ to about 1 to 2 mol%.
[0035]
In the case of glass containing Ce, it can be seen from FIG. 6 that the processing threshold increases almost monotonously with an increase in CeO ₂ content. Therefore, in order to obtain a lower processing threshold in the processing of glass containing Ce, it is desirable to use a glass having as low a CeO ₂ content as possible as a work piece. Specifically, the content is about 1 mol%. It is desirable to use this glass.
[0036]
Note that FIG. 3 shows that it is desirable to use glass containing CeO ₂ at a higher concentration in order to obtain a higher processing speed. Thus, in the glass containing Ce, and CeO ₂ content conditions to the machining speed and the fastest, CeO ₂ content condition for the processing threshold and minimum need to note different. As a matter of course, there is no problem in selecting a glass having an appropriate CeO ₂ content in accordance with the processing purpose and processing specifications. For example, when it is desired to process with a weak laser power even if the processing speed is low, it is preferable to use a glass containing CeO ₂ as low as possible to as close as 1 mol%. Further, if an intermediate processing threshold and an intermediate processing speed are required, for example, the CeO ₂ content may be adjusted to about 5 mol%.
[0037]
It can be seen from FIG. 7 that the processing threshold of the Sn-containing glass is relatively low as compared with the glass containing Fe or Ce. Further, the processing threshold value of the Sn-containing glass does not change greatly with respect to the SnO ₂ content. As shown in FIG. 4, since the dependency of processing speed on SnO ₂ content is relatively small, when using Sn-containing glass, pay attention to physical properties other than laser workability, such as refractive index, light transmittance, and thermal expansion coefficient. Thus, a more desirable glass composition can be selected.
[0038]
As described above, it was confirmed that laser processing was possible with all the glasses shown in Tables 1 to 3. That is, it was found that glass containing at least one element among Fe, Ce, and Sn can be processed by laser irradiation. The contents of Fe, Ce, and Sn at this time are 0.5 to 9 mol% in terms of Fe ₂ O ₃ , 1 to 9 mol% in terms of CeO ₂ , and 1 to 5 mol% in terms of SnO ₂ , respectively. .
[0039]
In glass, iron is known to have both divalent and trivalent states, and the ratio is known to vary depending on the composition and melting conditions. In general, since the main absorption of divalent iron is in the vicinity of 1 μm, it is considered that the presence of divalent iron does not contribute to the absorption of ultraviolet laser light or contributes little. In consideration of this, it can be expected that the processing threshold and the processing speed depend only on the amount of trivalent iron.
[0040]
From the total iron amount (generally expressed as T-Fe ₂ O ₃ ) when all the iron oxide added to the host glass is Fe ₂ O ₃ , the FeO amount obtained by the analysis is subtracted, The molar ratio of ferric trioxide Fe ₂ O ₃ was calculated. The results of examining the correlation between this value and the machining speed and the machining threshold are shown in FIGS. 8 and 9, respectively. When these are compared with FIG. 2 and FIG. 5, respectively, it turns out that the tendency of both does not change so much.
[0041]
That is, in principle, the processing threshold and processing speed are considered to depend on the amount of ferric trioxide Fe ₂ O _{3 in} the glass, but in practice, from the total iron amount T-Fe ₂ O ₃ It can be said that there is no problem even if the composition is designed by approximating the processing threshold or processing speed. However, the composition design may be performed such that the ratio of the amount of divalent iron and the amount of trivalent iron is changed by controlling the melting condition to finely adjust the laser workability.
[0042]
【The invention's effect】
According to the present invention, it is possible to provide a glass for laser processing capable of performing not only the vicinity of the glass surface but also laser processing reaching the inside of the glass. Since these have a low processing threshold, the amount of laser energy input required for laser processing can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an apparatus for laser processing.
FIG. 2 is a graph showing the dependency of processing speed on the content of Fe ₂ O ₃ .
FIG. 3 is a graph showing the CeO ₂ content dependency of processing speed.
FIG. 4 is a graph showing the dependency of processing speed on SnO ₂ content.
FIG. 5 is a graph showing dependence of processing threshold on Fe ₂ O ₃ content.
FIG. 6 is a graph showing the CeO ₂ content dependency of the processing threshold.
FIG. 7 is a diagram showing the SnO ₂ content dependency of the processing threshold.
FIG. 8 is a graph showing the dependency of processing speed on the content of ferric trioxide Fe ₂ O ₃ .
FIG. 9 is a graph showing the dependence of the processing threshold on the content of ferric trioxide Fe ₂ O ₃ .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser light 2 Laser light source 3 Mirror 4 Damper 5 Glan laser prism 6 Attenuator 7 Power meter 8 Shutter 9 Lens 10 XYZ stage 11 Sample holder 12 Sample 100 Laser processing apparatus

Claims (4)

In laser processing glass used for laser processing utilizing ablation or evaporation induced by absorption of laser light,
The glass for laser processing, wherein the glass contains at least one element of iron, cerium, and tin. The glass for laser processing according to claim 1, wherein the iron content is 0.5 to 9 mol% in terms of Fe ₂ O ₃ . Glass for laser processing according to claim 1, wherein the content of the cerium is 1-9 mol% in terms of CeO _2. The glass for laser processing according to claim 1, wherein the tin content is 1 to 5 mol% in terms of SnO ₂ .

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