JP2008001595A - Glass for laser beam machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein silver ions are difficult to diffuse into the inside of glass since the silver ions are reduced in the vicinity of a glass surface in an attempt to lower a laser beam machining threshold value by introducing the silver ions into glass containing an alkali metal by silver ion exchange so that an effective laser beam machining region is restricted within the vicinity of the glass surface to make the processing of the inside of the glass, such as formation of through-holes in the glass, difficult. <P>SOLUTION: The glass for a laser beam machining substantially has the following composition in terms of mol%: 20≤SiO<SB>2</SB>+B<SB>2</SB>O<SB>3</SB>≤50 (provided that 10≤B<SB>2</SB>O<SB>3</SB>≤50), 25≤TiO<SB>2</SB>≤40, 5≤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≤40. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to laser processing of glass by laser light irradiation, and particularly to a glass composition suitable for laser processing.

  A member obtained by finely processing a glass substrate such as an optical component used for optical communication or a microlens incorporated in a display device is used in a wide range of fields. As a method for finely processing such a glass substrate, conventionally, wet etching (chemical etching) using an etching solution such as hydrofluoric acid or dry etching (physical etching) such as reactive ion etching is generally used. Met.

  However, wet etching has problems of etching solution composition management and waste liquid treatment. In addition, dry etching requires a vacuum facility and the like, and has a problem that it is not efficient because it requires a complicated process such as forming a pattern mask or the like by a photolithography technique.

  On the other hand, direct processing technology that uses physical changes such as heating, melting, evaporation, and ablation by irradiating a material with laser light has also been developed. Since the laser beam can be focused to an extremely small spot, it is suitable for fine processing. Since it is a complete physical process, there is no problem like wet etching, and since it can be processed in the air or by scanning with laser light, there is no problem like conventional dry etching.

  With the development of laser technology, shortening of the laser pulse width and shortening of the wavelength have been realized, and processing of organic matter such as polyimide and metal can be performed on the order of micrometers. However, since glass is a brittle material, cracks are likely to occur during processing. Therefore, it has not been easy to use laser processing for fine processing for glass materials.

  For example, in Japanese Patent Laid-Open No. 11-217237, in order to solve such a problem, by introducing silver into the glass by ion exchange, a laser processing threshold value is reduced, and a glass that is not easily cracked is produced. Techniques to provide are disclosed.

  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. In addition, there is a problem that the ion exchange rate is slow and it is difficult to stably reach the ions inside the glass.

  In order to solve the above problems, an object of the present invention is to provide a laser processing glass containing an element that can be introduced into a glass at the time of melting without ion exchange and lowers a processing threshold. To do.

The glass for laser processing used for laser processing utilizing ablation or evaporation by absorbed laser beam energy of the present invention has a composition substantially consisting of the following oxides.
Displayed in mol%
20 ≦ SiO ₂ + B ₂ O ₃ ≦ 50 (where 10 ≦ B ₂ O ₃ ≦ 50),
25 ≦ TiO ₂ ≦ 40,
5 ≦ Li ₂ O + Na ₂ O + K ₂ O + Rb ₂ O + Cs ₂ O + MgO + CaO + SrO + BaO ≦ 40

The laser processing glass of the present invention may have a composition substantially consisting of the following oxides.
Displayed in mol%
20 ≦ SiO ₂ + B ₂ O ₃ ≦ 50 (where 10 ≦ B ₂ O ₃ ≦ 50),
25 ≦ TiO ₂ ≦ 40,
5 ≦ Li ₂ O + Na ₂ O + K ₂ O + Rb ₂ O + Cs ₂ O ≦ 40
Moreover, you may have a composition which consists of the following oxides substantially.
Displayed in mol%
20 ≦ SiO ₂ + B ₂ O ₃ ≦ 50 (where 10 ≦ B ₂ O ₃ ≦ 50),
25 ≦ TiO ₂ ≦ 40,
5 ≦ Li ₂ O + Na ₂ O + K ₂ O ≦ 40

  In the glass having the above composition, when the laser beam is absorbed, the glass structure changes or the absorptance changes, and ablation or evaporation occurs. If this phenomenon is utilized, the process which removes the specific part of glass can be performed, and the low process threshold glass with little energy required for a process is obtained. Further, the laser processing glass of the present invention is not limited to processing in the vicinity of the glass surface, and processing that extends to the inside of the glass, such as opening a through hole in a glass plate, can be easily performed.

  The object of the present invention is to improve the laser processability of glass, and the essence is that processing with lower energy can be performed from the glass surface to the inside. As an index for evaluating such laser processability, processing threshold values on the glass surface and inside were used.

  The processing threshold was measured using the optical system shown in FIG. As the laser light source 10, ultraviolet light of the third harmonic (wavelength: 355 nm) and the fourth harmonic (wavelength: 266 nm) of an Nd: YAG laser was used. The repetition frequency of this laser light source was 20 Hz, and the pulse width was 5 to 8 ns. The laser beam was condensed by a lens (not shown) having a focal length of 100 mm, and irradiated to the glass sample 40 fixed to the sample holder 30 on the sample stage 20. The irradiation time was controlled by the irradiation shutter 50 and set to 2 seconds.

  The energy of the laser beam was measured by putting a power meter in the optical path of the laser beam with the irradiation shutter closed. The sample was irradiated with this energy in various ways, the limit energy at which ablation occurred was determined and used as the processing threshold.

  Since the laser light source 12 generates a high energy beam, it 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. The laser light transmitted through the sample 20 is absorbed by the beam damper 18.

  The glass for laser processing was produced by mixing predetermined raw materials, melting in an electric furnace, and then slowly cooling. The obtained glass block was cut and polished by a general method to prepare a glass sample for experimental laser processing having a plate shape and a smooth surface. Examples of the present invention will be described below, but the present invention is not limited to these examples.

[Example]
Table 1 shows the compositions of Examples 1 to 11 and Reference Examples 1 to 7 of the laser processing glass of the present invention. Reference Examples 1 to 4 and Example 1 are compositions in which the amount of the intermediate oxide is changed. Reference Example 5 and Examples 2-3 are examples in which the network-forming oxide was changed without changing the amount of TiO _{2 in} the composition of Example 1. Examples 4 and 5 are examples in which the amount of the modified oxide added was changed without changing the amount of TiO _{2 in} the composition of Example 1. Reference examples 6 and 7 have compositions in which the amounts of network-forming oxide SiO ₂ and intermediate oxide TiO ₂ are greatly changed. Examples 6 to 11 are examples in which the type of the modified oxide was changed without changing the amount of TiO _{2 in} the composition of Example 1.

The composition range of each component is in the following range with the unit as mol%.
Network-forming oxide (SiO ₂ , B ₂ O ₃ ): 20.0 to 50.0
However, and the B ₂ O ₃ containing 10.0 to 50.0 mol%.
Intermediate oxide (TiO _2): 25.0~40.0
Modified oxides (Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O, Cs ₂ O, MgO, CaO, SrO, BaO): 5.0 to 40.0
The laser-processed glass of the present invention consists essentially of the above composition except for a small amount of impurities. Moreover, as long as the composition range is satisfied except for TiO ₂ and B ₂ O ₃ , each component may not be contained.

In the glass having the above composition, the skeleton as glass can be maintained by containing 20 to 79 mol% of SiO ₂ or B ₂ O ₃ which is a network-forming oxide of glass. The modified oxides LiO ₂ , Na ₂ O, K ₂ O, Rb ₂ O, Cs ₂ O, MgO, CaO, SrO, or BaO partially destroy the glass network structure. It is a component used to weaken or loosen the temperature gradient of viscosity. A glass can be produced within an addition range of 5 to 60 mol%. Al ₂ O ₃ or TiO ₂ is an intermediate oxide, and is a network-forming oxide SiO ₂ or B ₂ O ₃ and modified oxides LiO ₂ , Na ₂ O, K ₂ O, Rb ₂ O, Cs Depending on the balance of ₂ O, MgO, CaO, SrO, or BaO, both network oxides and modified oxides can be present in the glass. In particular, TiO _{2 as an} intermediate oxide is an essential component for lowering the laser processing threshold as will be described later.

  The laser beam having a wavelength of 266 nm was irradiated to the glass sample for laser processing melted in the above composition while changing the irradiation energy. Table 2 shows the surface processing threshold values obtained as a result. Next, the same experiment was performed with the wavelength of the laser beam set to 355 nm. Table 3 shows the surface processing threshold values obtained as a result.

  In addition, the minimum power measurable with the power meter at the time of laser beam irradiation with a wavelength of 266 nm is 15 mW, and superiority or inferiority below that value cannot be compared. Further, when irradiating a laser beam having a wavelength of 355 nm, 100 mW or less could not be accurately measured due to a problem of laser stability.

In Reference Examples 1 to 4 and Example 1 in which the amount of the intermediate oxide is changed, as shown in FIG. 1, the processing threshold decreases as the amount of TiO ₂ increases. ₂ : 25 mol%), the processing threshold is lowered to the measurement limit. In Reference Example 5 and Examples 2 to 3 in which the network-forming oxide was changed without changing the amount of TiO _{2 in} the composition of Example 1, the ratio of SiO ₂ and B ₂ O ₃ which are network-forming oxides was changed. Even if it is changed, the threshold value does not change below the measurement limit. In Examples 4 and 5 in which the amount of the modified oxide added was changed without changing the amount of TiO _{2 in} the composition of Example 1, the threshold was changed even when the amount of Na ₂ O as the modified oxide was changed. The value did not change below the measurement limit. In the compositions of Reference Examples 6 and 7 in which the amounts of the network forming oxide SiO ₂ and the intermediate oxide TiO ₂ are greatly changed, the processing threshold is lower than those of Comparative Examples 1 and 2 even in these compositions. The effect is working. In Examples 6 to 11 in which the type of the modified oxide was changed without changing the amount of TiO _{2 in} the composition of Example 1, the threshold value was below the measurement limit even if the type of the modified oxide was changed. It didn't change.

[Comparative Example 1]
Raw materials were prepared with the composition (mol%) shown in Table 4 to prepare glass samples. This glass sample has a composition very similar to that of Examples 1 to 5. However, when the processing threshold is obtained in the same manner as in Examples, the maximum power is 1100 mW when the wavelength of the laser beam is 266 nm, and the wavelength of the laser beam is At either of the maximum powers of 2100 mW at 355 nm, no ablation or evaporation occurred, and the sample did not change.

[Comparative Example 2]
As a comparative example, a material having a composition (mol%) shown in Table 5 was used. This is so-called soda lime glass used for ordinary window glass and the like. When the processing threshold is obtained in the same manner as in the example, ablation or evaporation does not occur in either of the maximum power 1100 mW when the wavelength of the laser beam is 266 nm and the maximum power 2100 mW when the wavelength of the laser beam is 355 nm, There was no change in the sample.

  From the above, it can be seen that the laser processing threshold in ultraviolet light is significantly reduced by adding titanium to the oxide glass. Further, the processing threshold value decreases as the amount of titanium added increases. However, it hardly depends on the composition of the network forming oxide or the modified oxide. In the above, titanium is expressed in the form of its oxide, but the effect is the same even if titanium is in the form of atoms, colloids or ions.

  Since titanium can be added when the glass is melted, the amount added is easy to control, and therefore the laser processing threshold can be easily controlled. Further, since it is added at the time of melting, the concentration of titanium in the glass is uniform. For this reason, the laser processing threshold is constant in the glass body to be processed, and processing that extends into the glass, for example, formation of through holes, can be easily performed.

  According to the present invention, a low processing threshold glass with less energy required for processing can be obtained. Furthermore, since titanium can be introduced into the glass by melting, the processing threshold can be easily controlled by changing the amount of titanium added, and a material having uniform workability can be obtained.

It is a figure which shows the processing characteristic of the glass for laser processing of this invention. It is a schematic diagram which shows the optical system for laser processing threshold value measurement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Laser beam 12 Laser beam 20 Glass sample 22 Sample holder 24 Sample stage 30 Irradiation shutter 40 Power meter

Claims (3)

In laser processing glass used for laser processing using ablation or evaporation by absorbed laser light energy,
A laser processing glass characterized by having a composition substantially consisting of the following oxides.
Displayed in mol%
20 ≦ SiO ₂ + B ₂ O ₃ ≦ 50 (where 10 ≦ B ₂ O ₃ ≦ 50),
25 ≦ TiO ₂ ≦ 40,
5 ≦ Li ₂ O + Na ₂ O + K ₂ O + Rb ₂ O + Cs ₂ O + MgO + CaO + SrO + BaO ≦ 40 The glass for laser processing according to claim 1, wherein the composition is substantially composed of the following oxide.
Displayed in mol%
20 ≦ SiO ₂ + B ₂ O ₃ ≦ 50 (where 10 ≦ B ₂ O ₃ ≦ 50),
25 ≦ TiO ₂ ≦ 40,
5 ≦ Li ₂ O + Na ₂ O + K ₂ O + Rb ₂ O + Cs ₂ O ≦ 40 The glass for laser processing according to claim 1, wherein the composition is substantially composed of the following oxide.
Displayed in mol%
20 ≦ SiO ₂ + B ₂ O ₃ ≦ 50 (where 10 ≦ B ₂ O ₃ ≦ 50),
25 ≦ TiO ₂ ≦ 40,
5 ≦ Li ₂ O + Na ₂ O + K ₂ O ≦ 40

Images