JP2006256944A - Method and device for cutting brittle material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To cut a material only with a scribing ranging the overall thickness of a brittle material through generating thermal stress caused by heating with laser beam irradiation and cooling with cooling liquid spraying. <P>SOLUTION: An absorption coefficient to a laser beam for the brittle material is controlled and the laser beam is penetrated through the overall thickness of the material or penetrated to a sufficient depth even if not penetrated to a back face and then a scribing face occurs with the thermal stress through the overall thickness of the material. The control of a laser wavelength is realized by a procedure that the laser wavelength is selected for the optimum absorption intensity of the material in the range of an electron transition or a lattice vibration absorption zone or a procedure that a low absorption zone is selected and the material is heated by absorbing a laser light and impurities for absorbing the irradiated laser light without influencing to the transmission property in a visible region and without deteriorating the displaying property of glass for a display device are added. Impurities for quenching are added for preventing fluorescent light emission. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a brittle material, especially a method for cleaving brittle materials such as glass, and an apparatus for the same. In the specification of the present application, description is made specifically for glass, but in addition to glass, the present invention can be applied to brittle materials such as quartz, ceramic, and semiconductor.

  Brittle materials have conventionally been cleaved by a mechanical method using a carbide tool such as a diamond tip. The application of this method to glass is also a method that has been used for a long time over the past century.

  However, these mechanical methods have the following drawbacks. The first is that small pieces called cullet are generated at the time of cleaving, and the work surface is soiled. Secondly, there is a risk that a microcrack is generated in the vicinity of the fractured surface and the workpiece is cracked starting from the crack. Third, there is a cutting margin of about several hundred microns at the minimum, and the existence of this cutting margin cannot be ignored at present when the workpiece size is miniaturized without limit. In addition to this, there are other disadvantages that cannot be ignored in the industry, such as the limit of processing speed and the cost of tools that are consumables.

  Breaking window glass, etc., is not a problem with the use of conventional technology, but in the case of fine glass cleaving used for liquid crystal displays, plasma displays, etc., the broken section is polished to prevent microcracks, and then cleaned. Subsequent processes are required.

  On the other hand, the laser cleaving method, which has been expected to be promising recently, has the following advantages and may eliminate the drawbacks of the diamond chip method. First, the mass loss is zero (no cullet generation), and no post-process such as cleaning is required. Second, since a high-strength cross section is obtained without the occurrence of fracture defects such as microcracks in the vicinity of the split cross section, a post-process such as polishing is unnecessary. Third, a mirror surface having a surface roughness of 1 μm or less is obtained. Fourth, the product external dimension accuracy is ± 25 μm or less. Fifth, it can be used for glass plates with a thickness of up to 0.2 mm and can be used for future liquid crystal TV glass.

Next, the principle of this method will be described. When glass is irradiated with a high energy density CO ₂ laser beam, the laser beam is generally absorbed at the irradiation spot, and as a result of rapid heating, radial cracks are generated, and the cleaving proceeds only in the traveling direction. I can't do that. However, if the energy density of the laser beam is set to be sufficiently lower than that which generates such cracks, the glass is only heated and neither melting nor cracking occurs. At this time, the glass tends to thermally expand, but it cannot expand due to local heating, and compressive stress is generated around the irradiation point. This local heating source is moved in the direction in which it is desired to cleave. When cooling is performed by spraying a cooling liquid after heating, a tensile tension is generated on the contrary. As shown in FIG. 1, when the cross-sectional shape of the laser beam is formed into an appropriate one, tensile tension is generated only in the direction perpendicular to the light moving direction. In the figure, 1 is a heating laser beam, 2 is a compressive stress inside the glass, 3 is a cooling liquid, and 4 is a tensile tension inside the glass. The cleavage crack 5 is generated by the action of the tensile tension. In the glass plate 6 shown in FIG. 2, if a trigger crack 8 is attached to the starting point by a mechanical method, the cleaving crack 5 is generated from the trigger crack and can be advanced along the moving direction 7 of the laser beam. In order for such a phenomenon to occur ideally, the energy distribution of the irradiated laser beam needs to be optimal in order to generate such tension. These optimal distributions have been studied in various glass cuttings. The heating laser beam 1 shown in FIGS. 1 and 2 has been optimized.

Regarding the method of realizing such an optimal distribution, the following patent application has been filed by one of the inventors.
Patent application number 2003-363855
Patent application number 2004-156891
This laser application for glass cleaving is indispensable in the processing of fine glass in general, for which demand will increase rapidly.

In the thermal stress cleaving of glass by CO ₂ laser beam irradiation, as shown in FIG. 3, the CO ₂ laser beam is absorbed only by the glass surface layer and does not transmit through the entire thickness of the glass. This is due to the extremely large absorption coefficient of glass at the CO ₂ laser wavelength. The depth of cleaving with laser (referred to as laser scribe) is usually about 100 μm. In the figure, 9 is a laser scribe surface. Making the surface deeper than this is not possible even if the laser power is increased as long as a CO ₂ laser beam is used. However, it has been demonstrated that if the laser output is increased, the heat source can penetrate into the glass by heat conduction, and the scribe depth can be increased somewhat. However, the mechanical scribe surface shown in FIG. 4 is also usually of a similar depth, and glass is highly brittle and it is easy to mechanically cleave by applying stress according to this scribe line. The increase in depth has not been required so far. This process of cleaving with the application of mechanical stress is called a break.

  Conventionally, glass is broken by a combination of mechanical scribe and break. In the case of mechanical scribing, as shown in FIG. 4, since there are a large number of microcracks near the scribe line, the break is relatively easy. However, as shown in FIG. 12, the break surface after mechanical scribing does not necessarily constitute one plane orthogonal to the glass surface. In the case of mechanical scribing, since the fractured surface is polished and cleaned after the break, high quality was not required for the break itself.

  In the case of laser scribing, it is necessary to use a break in combination with the conventional method. For this reason, while having the advantages of the above-mentioned folding angle, the spread to production sites is restricted. Even in the case of fine glass for liquid crystal televisions, whose advantages are relatively appreciated, it has not yet been put to practical use on an actual production line. For practical use, break surface position accuracy, angle accuracy, and cleanliness are required. Of course, the cullet is not allowed to adhere. Unfortunately, break technology that solves these problems is not yet complete. In particular, in the case of microwork, curve, multi-layer glass, thick glass, tempered glass cleaving, etc., the application of laser cleaving technology is strongly desired, but no solution has been provided. The present invention relates to a technique in which laser scribing is realized over the entire plate thickness and all these problems are solved. Such a scribe is hereinafter referred to as a full cut. The present invention relates to a technique for realizing a full cut.

  In the present invention, laser beam transmission to a brittle material is realized to a sufficient depth, and in many cases, the entire plate thickness from the front surface to the back surface. For this reason, the conventional laser split heat insulation source is a linear heat source that exists only on the surface and penetrated by heat conduction in the depth direction of the material, whereas in the present invention, the surface heat source reaches from the front to the back from the beginning. Is used. This difference is shown in FIG. FIGS. 2A and 2B show a conventional heat source and a heat source according to the present invention, respectively. For this reason, the scribe depth extends over the entire thickness, so that the break process is unnecessary.

  Such transmission of the laser beam can be performed by optimizing the absorption coefficient of the material with respect to the laser beam.

According to the present invention, the conventional laser / glass cleaving consisting of both laser scribe and break processes can be made into one process only for scribe. Laser glass breaking, while having many great technical advantages, has failed to replace the diamond cutter system that has been used over the past century. The present invention transforms that situation. The direct effects include the following only in the liquid crystal television production process.
1) The cleaving position accuracy is high.
2) The fractured surface is a mirror surface and the surface roughness is good.
3) The fractured surface is sufficiently perpendicular to the glass surface.
4) There is no adhesion of cullet on the cut surface and it is clean.
5) Cleavage can be automated.
6) Cleaving can be performed at high speed.
7) Subsequent processes such as polishing and cleaning can be largely omitted.

In addition to the above merits, there are the following general merits.
1) Curve cutting is possible. This is comparable to laser metal processing.
2) It is possible to cleave the multilayer structure board. Applicable to liquid crystal display and plasma display glass.
3) Microwork can be cleaved. Applicable to IC tag.
4) The tempered glass can be cleaved. Applicable to architectural glass.
5) The curved glass can be cleaved. Applicable to automotive glass.
As described above, if the glass cleaving by the laser spreads to various fields of the industry, the effects cannot be measured in the processing speed, the processing quality, the economy, the difficulty, and the like.

In general, how much light passes through a material depends on absorption by the material. If the series coefficient of the material is α (cm ⁻¹ ), the propagation distance is x (cm), and the light intensities before and after propagating the distance x are I and I ₀ , the following relational expressions are established.
I = I ₀ · e ^−αx (1)
From this equation, if the required value of the transmission distance is known, the necessary absorption coefficient can be obtained. Next, the upper limit value, optimum value, and lower limit value of the absorption coefficient are obtained.

As a lower limit value, consider a case where the laser beam is transmitted through the glass plate thickness L by 90%. At this time, a part of the energy is wasted, but a full cut can be realized sufficiently. If I / I ₀ = 0.9 in (1), then α = 0.105 / L. This is the lower limit of the absorption coefficient. As the upper limit, according to the experience of the inventors, full scribing often occurs when scribing to 1/4 of the plate thickness. Substituting I / I ₀ = 0.99 and x = L / 4 into the equation (1) yields α = 18.42 / L. This is the upper limit of the absorption coefficient. The optimum value is the case where 50% of the laser beam is absorbed by the glass plate, and α = 0.593 / L in the same manner from the equation (1).

Upper and lower limits and optimum values for three typical glass plate thicknesses of 0.02 cm (future liquid crystal TV), 0.07 cm (current liquid crystal TV), and 0.28 cm (current plasma TV) When the value is displayed, it is as shown in the table below.
α lower limit (cm ⁻¹ ) optimum value (cm ⁻¹ ) α upper limit (cm ⁻¹ )
Thickness 0.02cm 5.25 34.65 921
0.07cm 1.50 9.90 263
0.28cm 0.38 2.48 65.8
In the following embodiment, a control technique of α for realizing these numerical values will be described.

FIG. 6 shows the absorption characteristics of quartz glass as a function of wavelength. The vertical axis represents the attenuation constant κ, and the absorption coefficient α has a relationship of α = 4πκ / λ, where λ is the wavelength. From the figure, the absorption coefficient α of quartz glass with respect to a CO ₂ laser beam with a wavelength of 10.6 μm is about 12600 cm ⁻¹ . In this case, according to the equation (1), when propagating from the surface of the glass plate to a depth of 3.7 μm, 99% of the laser beam intensity is absorbed. This will only penetrate the surface layer. Nevertheless, in practice, a scribe depth of about 100μ is possible, and it can be seen that heat conduction is useful for this.
Glass differs in composition from structure to structure, and differs in composition from manufacturer to manufacturer. However, the approximate absorption characteristics can be referred to those in FIG. In the figure, the absorption coefficient is determined as a function of wavelength. According to this, as described above, the absorption coefficient was excessive at the CO ₂ laser wavelength of 10.6 μm. In order to change the absorption coefficient, it is necessary to change the wavelength. However, it is not possible to select all wavelengths continuously. Typical laser wavelengths that can provide high-power lasing are as follows.
10.6μ (CO ₂ laser)
5μ band (CO laser)
2.94μ (E _r : YAG laser)
2.09μ (H ₀ : YAG laser)
1. 06μ (N _d : YAG laser)
1. 03μ (Y _b : YAG laser)
0. 515μ (same as above)
0. 343μ (3rd harmonic)
0. 258μ (4th harmonic)
0.206μ (5th harmonic)
The wavelength can only be selected from these.

  Another method of controlling the absorption coefficient is to change the absorption characteristic itself of FIG. For this purpose, impurities may be added in the glass. However, it is necessary to select an impurity that does not affect the transmission characteristics in the visible range and does not deteriorate the display characteristics of the glass for flat panel display. In this case, since wavelength selection becomes free, the laser to be used can be selected from existing high-power lasers.

First, an example of the effectiveness of wavelength selection is shown. Consider using a CO laser beam having a strong oscillation wavelength in the 5μ band instead of the CO ₂ laser. The CO laser can be oscillated only by changing the gas composition and the wavelength of the output mirror in the CO ₂ laser. The laser oscillates in the 4.9-5.7 μ band in terms of gain. In FIG. 6, the absorption coefficient of quartz glass at 5 μ is about 62.85 cm ⁻¹ . In this case, according to the equation (1), 99% of the laser beam is absorbed with a glass plate thickness of 0.7 mm. Although it is desirable that the absorption coefficient is lower, if the CO laser beam is used instead of the CO ₂ laser beam, a full cut of the glass can be realized.

Next, consider an example of impurity addition. An appropriate amount of water (H ₂ O) having absorption characteristics with respect to Er: YAG laser or Ho, Tm: YAG laser light is added to the glass, and then these laser lights are irradiated to realize a full cut. be able to. This is because of the infrared absorption of water, using an absorption band with wavelengths of about 2 μm and about 3 μm, Ho, Tm: YAG laser light oscillating at a wavelength of 2.091 μm, or Er: YAG oscillating at a wavelength of 2.94 μm. It absorbs laser light.

  When glass is exposed to water vapor at high temperature and high pressure, it will be in a state containing a certain amount of stable water. In addition, when left for a long time under such conditions, water is taken in to form a gel in a colloidal solution, or a state called a water-like ceramic is formed. Roger F. Bartholomew published a paper entitled “High-water containing glasses” in Journal of Non-Crystalline Solids, Volume 56 (1983), pages 331 to 342, discussing the properties of glass with high concentrations of water. He cited the result of Scholze in the same paper. The absorption due to the bending vibration of H—O—H was observed at a wavelength of 6.2 μm, and the absorption due to hydrogen bonding was observed at a wavelength range of 4.2 to 3.6 μm. There is absorption due to stretching vibration of Si—OH and H—OH in the wavelength region of −2.7 μm, and overtone absorption due to combined vibration of stretching and bending of Si—OH at 2.22 μm. It was shown that the overtone absorption of the combined vibration of O—H stretching and bending was absorbed by the overtone of the stretching vibration of Si—OH and H—OH at 1.4 μm. Since these absorptions are due to expansion and contraction between the bonded atoms and bending vibration, all the infrared rays absorbed in the respective wavelength regions become heat and raise the temperature of the glass.

  Furthermore, these absorption coefficients are proportional to the concentration of water mixed in the glass. A heat source with a constant temperature can be realized by realizing a moisture concentration distribution that achieves uniform absorption and heat generation in the thickness direction according to the thickness of the glass plate to be fully cut with laser light. . As an irradiation laser capable of full-cutting glass by light absorption by water, there is a Ho, Tm: YAG laser that oscillates at a wavelength of 2.091 μm, and this laser beam is mainly a combined vibration of expansion and contraction of HO-H. Can be absorbed by the overtone.

  Another candidate is an Er: YAG laser that oscillates at a wavelength of 2.94 μm. In the case of this laser, it can be absorbed mainly by the stretching vibration of Si—OH and H—OH. As described above, when water is mixed into the glass, absorption in the infrared region occurs, but there is no effect on the transmission characteristics in the visible light region, so that the display characteristics of the liquid crystal or PDP display glass are deteriorated. Absent. Moreover, the hardness of the glass decreases as the water content increases, which is convenient because cracks are less likely to occur.

  At the oscillation wavelength of the rare earth laser (Nd, Yb, Ho, Er laser), an appropriate amount of rare earth ions (Nd, Yb, Ho, Er ions for the laser, respectively) are added to the glass, and the corresponding respective Full cutting can be performed by irradiating laser light. Also in this case, as described above, it is preferable that the added ions have a concentration gradient so that uniform absorption occurs in the depth direction.

  Rare earth atoms are surrounded by a group of electrons in the O shell, which is the outer shell of f electrons in the N shell. And has an energy level suitable for laser oscillation. Such lasers include Nd: YAG laser, Yb: YAG laser, Ho, Tm: YAG laser, Er: YAG laser, and the like.

  In the laser light absorption for realizing the full cut, one of these rare earth atoms used for laser oscillation, for example, Yb is added to the glass, and the laser light using the same rare earth atom, in this case Yb: YAG This glass is irradiated with laser light to be absorbed.

H. L. Smith and A.M. J. et al. Cohen et al. Published a paper entitled “Absorption spectra of relations in alkaline-silicate glasses of high ultra-violet transmission” on page 18 of Physics and Chemistry, page 17 of Vol. Absorption coefficient was measured when Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, and U atoms were doped in the glass. 7 as an example, a thickness of 4.92mm doped with 3.7% of Yb _Na 2 O. 3SiO ₂ shows the absorption coefficient of the glass. Na ₂ O. doped with Yb (or Nd) The 3SiO ₂ glass has absorption in the vicinity of 1 μm, which corresponds to 1.03 μm which is the oscillation wavelength of the Yb: YAG laser or 1.06 μm which is the oscillation wavelength of the Nd: YAG laser. Similarly, Na ₂ O. doped with Ho or Tm. The 3SiO ₂ glass has absorption in the vicinity of 2 μm, which corresponds to 2.091 μm, which is the oscillation wavelength of the Ho, Tm: YAG laser.

  There is a concern that the absorption wavelength and oscillation wavelength of these rare earth atoms have a deviation of about 100 nm. This is a collection of small crystals of glass, which is a shift in absorption wavelength due to the difference in crystal field size for each of these crystals, which is a so-called non-uniform absorption wavelength spread. Fuxi's book “Optical and spectroscopic properties of glass” (Springer-Verlag), page 158, FIG. 7.6 is shown in FIG. In this figure, an unevenly broadened line is indicated by an inhomogeneously broadened line. The lasing wavelength is absorbed because it exists in the absorption of these non-uniform spreads in the glass.

  Accordingly, it is possible to control the absorption coefficient of the glass by using a rare earth laser for processing and adding an appropriate amount of the same rare earth atom as the laser in the glass. With this principle, the purpose of this patent can be realized. However, rare earth atoms excited by light absorption have a high probability of emitting fluorescence and returning to the ground state. In this case, the absorbed laser energy does not become heat and the object of this patent cannot be achieved. Therefore, it is necessary to quench the fluorescence. As a quenching method, it is conceivable to add rare earth atoms having many energy levels smaller than that between the fluorescent energy levels as a quencher.

  G. E. Peterson and P.M. M.M. Bridenbaugh is "Study of relaxation process in Nd using pulsed excitation". It was shown that doping with rare earth atoms such as Sm and Dy is effective. Therefore, Nd-doped glass that has absorbed Nd: YAG laser light is quenched by adding these rare earth atoms to the same glass, and the energy of the absorbed laser light is released as heat by non-radiative transition due to phonons. And can achieve the objectives of this patent. Since these quenching rare earth atoms are close to the laser oscillation lines of Nd and Yb, it is considered that they are also effective for glass doped with Yb laser and Yb as an absorber. In the case of a combination of Ho, Tm: YAG laser and glass doped with Ho or Tm, the oscillation wavelength is 2.091 μm, and rare earth atoms such as Pr, Nd, Eu, etc. having many energy levels smaller than this energy gap. Is considered effective. Furthermore, in this case, since the energy gap itself that contributes to light emission is smaller than that of Nd or Yb, G.I. As Fuxi writes in his book “Optical and spectroscopic properties of glass” (Springer-Verlag), page 192, the probability of non-radiation increases.

  FIG. 9 shows the 156 page of FIG. Although 7.4 is quoted, the probability Wnr of non-radiative transition increases when the energy gap is small. As another method of quenching, there is concentration quenching or concentration quenching that occurs when the addition amount for absorption is increased, and this method is effective in all the combinations described here. However, in the case of this patent, concentration quenching can only be employed under these conditions because the amount of absorbing impurities added must be optimized to produce the required heat generation for a given glass thickness. .

  In summary, in the case of Nd: YAG laser and Yb: YAG laser, Nd and Yb are respectively added as impurities for glass absorption, and Pr, Sm, Dy are added for quenching, or the concentrations are Nd and Yb. Quench the light. When a Ho, Tm: YAG laser is used, Ho or Tm is added as an impurity for absorption, and Pr, Nd, Eu is added as a quencher for quenching, or Ho or Tm is within the optimum absorption range. Add to quench the concentration.

  In order to realize light absorption in the ultraviolet wavelength region due to the transition from the full band to the conduction band of bound electrons in the glass depending on the state of oxygen ions constituting the glass to be fully cut, the third harmonic, A full cut can be performed by selectively irradiating from harmonics and fifth harmonics.

  The present embodiment uses absorption that occurs in the ultraviolet wavelength region from the full band of bound electrons in the glass to the conduction band, and the laser that generates this absorption is the third harmonic, the fourth harmonic of the rare earth laser, It is selected from the fifth harmonics, irradiated, and fully cut. The absorption of ultraviolet rays by glass is due to oxygen ions in the glass. When these oxygen ions are strongly bound, the glass becomes transparent to a shorter wavelength.

FIG. 10 quotes FIG. 108, page 233, “Glass Nature, structure, and properties” (Springer-Verlag) by Host Scholze, where 1 curve is for highly pure SiO ₂ glass, 2 for normal state SiO 2. _{2 of} glass ₂ is highly pure Na ₂ O. In the 3SiO ₂ glass, 4 is an ordinary Na ₂ O.O. The transmission wavelength characteristic of 10 mm thickness of 3SiO ₂ glass is shown. From the figure, it can be seen that in the case of a glass having a thickness of 10 mm, the wavelength at which the transmittance is 50 percent ranges from 160 nm to 320 nm. Therefore, the laser to be used also needs to be in this wavelength range. In the case of this patent, optimum absorption can be obtained from the third, fourth and fifth harmonics of the laser doped with rare earth atoms in the solid. Select the wavelength and irradiate. These wavelengths are the third, fourth, and fifth harmonics of 353 nm, 265 nm, and 212 nm of the Nd: YAG laser, and the third, fourth, and fifth harmonics of the Yb: YAG laser are 343 nm, 258 nm, and 206 nm. The third harmonics of the Nd: YLF laser are 349 nm and 440 nm, the fourth harmonics are 262 nm and 330 nm, the fifth harmonics are 209 nm and 264 nm, and the like. A full cut can be performed by selecting a wavelength from which optimum absorption is obtained from the thickness and composition of a given glass.

  When the laser beam passes through the glass while being absorbed, the amount of heat generation decreases exponentially in the depth direction of the glass, as is apparent from equation (1). Although full cutting may be possible as it is, it is desirable that the amount of heat generation be a constant value regardless of the depth for high-quality processing. For this purpose, the impurity concentration is preferably distributed in an inverse exponential manner from the front surface to the back surface, and heat generation is preferably made uniform in the depth direction.

  If the laser beam penetrates to a sufficient depth in the material, as in the present invention, the heat source is a thin surface heat source and no further heat conduction is required. Since it is desirable that the laser output be as low as possible, the cross-sectional structure of the irradiation beam is desirably a linear shape having a narrow width. In this case, it is desirable to use a disk laser having excellent beam characteristics as the laser oscillator.

Even with a CO ₂ laser beam with strong surface absorption, the heat source penetrates in the depth direction of the material due to heat conduction if the output is somewhat high. In particular, this method will also deepen the scribe when the material thickness is thin. In this case, heat conduction is transmitted to the surface direction of the material simultaneously with the depth direction. Desirably, heat conduction should be concentrated in the depth direction of the material. As an extreme example, when the cross section of the irradiation laser beam is equal to the entire surface of the material, heat conduction occurs only in the depth direction. Of course, this cannot be selected because the scribe position cannot be specified. Even so, it is desirable that the irradiation laser beam has a wide cross-sectional shape so that the ratio in the depth direction is increased as much as possible.

  The heating method has been described above. In order to realize a full cut, it is necessary to efficiently perform cooling in the thickness direction. For this purpose, it is more effective to perform cooling not only on the glass surface but also on the back surface.

  What has been described above are some embodiments for realizing the functions of the present invention, and it goes without saying that the spirit of the present invention can be realized in many other ways.

  Cutting flat glass used for flat panel displays such as liquid crystal displays and plasma displays, mobile and car navigation displays, and IR filters for optical devices is currently performed with a diamond cutter, and the need for a cleaning process after cutting. And the presence of microcracks. Such a problem can be solved by the laser cutting according to the present invention. The present invention can also be applied to processing of microchips such as IC chip cover glass and IC dougs. Since the cutting length is longer than in the case of a large workpiece, the effect of the present invention is great.

  Since glass parts for automobiles are often curved, they are now mechanically cut after linear cutting. For this reason, there is a great expectation for laser processing that requires only glass cleaving.

  Furthermore, the processing of tempered glass as a building material can contribute to the solution of the problem demanded by modern society for crime prevention. Cutting of tempered glass is difficult by a mechanical method, and use of a laser is expected.

  Thus, the advent of laser technology for improving glass breaking is a solution to various problems demanded by modern society.

FIG. 3 is a diagram showing the principle of generation of compressive stress and tensile tension in glass by laser light heating and cooling. Glass cutting principle using laser. Glass laser scribe. Glass mechanical scribe. Heat generation inside the glass according to the conventional method and the present invention. Light absorption spectrum of quartz glass. The optical absorption spectrum of Na ₂ O.3SiO ₂ glass to which Yb and Lu are added. Light absorption spectrum and oscillation spectrum of rare earth atoms. Radiative transition and non-radiative transition. UV light absorption spectra of various glasses.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating laser beam 2 Compressive stress inside glass 3 Cooling liquid 4 Tensile tension inside glass 5 Cleavage crack generated in glass 6 Glass plate 7 Moving direction of laser beam 8 Trigger crack 9 Laser scribe surface 10 Break surface 11 after laser scribe Scribe surface 12 Break surface after mechanical scribing 13 Heat source 14 by heat conduction Heat source 15 by transmission laser beam absorption Optical absorption spectrum (4.92 mm thickness) of Na ₂ O.3SiO ₂ glass added 3.7% Y _b
Optical absorption spectrum (2.43 mm thickness) of Na ₂ O.3SiO ₂ glass added with 9.0% of 16 L _u
17 rare earth atoms in the oscillation spectrum 18 rare earth atoms of the light absorption spectrum 19 emitted transition 20 radiationless transition 21 highly pure _S i _{O 2} glass (10mm thick)
22 S _i O ₂ glass in the normal state (same as above)
23 Highly pure Na ₂ O.3S _i O ₂ glass (same as above)
24 Normal state Na ₂ O.3S _i O ₂ glass (same as above)

Claims (12)

Brittleness that breaks down the entire thickness of the material by generating cracks (laser scribing) due to thermal stress in brittle materials such as glass, quartz, ceramics, and semiconductors by using laser light irradiation that moves in advance and subsequent cooling means In the material cleaving apparatus, when the material thickness is L (cm) and the material absorption coefficient is α (cm ⁻¹ ), α satisfies the inequality 0.105 / L <α <18.42 / L. Selected one.   Control of (alpha) in Claim 1 is performed by wavelength selection of irradiation laser light. In claim 2, the irradiation laser light is a laser light from a CO ₂ laser, a CO laser, an Er: YAG laser, a Ho: YAG laser, an Nd: YAG laser, a Yb: YAG laser, or a harmonic of these laser lights. What to choose from.   The control of α in claim 1, wherein an optimum amount of light is absorbed with respect to the irradiated laser light, the absorbed energy is converted into heat without emitting fluorescence, and the visible region affecting the display characteristics of the display glass By adding impurities that do not have absorption and fluorescence characteristics to brittle materials.   5. The method according to claim 4, wherein water is used as an additive impurity for absorbing the irradiation laser light, and an Er: YAG laser or a Ho: YAG laser is used as the irradiation laser.   5. The rare earth atom such as Nd, Yb, Ho, Er or the like is used as an additive impurity for absorbing the irradiation laser beam, and the irradiation laser is Nd: YAG laser, Yb: YAG laser, Ho: YAG laser, in each case. Using an Er: YAG laser.   In Claim 4, the rare earth atom which has many energy levels with a gap smaller than between fluorescence energy levels is added as an additive impurity for fluorescence quenching, and fluorescence emission is prevented.   8. The method according to claim 7, wherein rare earth atoms such as Pr, Sm, Dy, Nd, and Eu are used as an additive impurity for fluorescence quenching.   In Claim 6, fluorescence emission is prevented by concentration quenching with increased additive impurity concentration.   5. The additive impurity concentration for absorbing laser light and / or the additive impurity concentration for quenching fluorescence is increased or decreased exponentially with respect to the depth direction of the material. The heat generated by the irradiated laser beam is made uniform in the depth direction.   In Claim 1, the cooling means to a brittle material is made from both the front and back surfaces of the same material.   3. The disk laser according to claim 2, wherein when the irradiation laser is a solid-state laser, the disk laser has excellent beam characteristics.

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