JP4072596B2 - Method and apparatus for cleaving brittle materials - Google Patents

Description

The present invention relates to a method for cleaving a brittle material such as glass used for a flat panel display for display, a cleaving apparatus used for the cleaving method, and a brittle material suitable for the cleaving method . In the specification of the present application, description is mainly made on a non-alkali glass for a display. However, in addition to glass , the present invention can be applied to brittle materials such as quartz, ceramic, and semiconductor .

  Conventionally, glass plate materials have been cleaved by a mechanical method using a carbide tool such as a diamond chip. The application of this method to glass is 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 μm 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 fractured surface is polished to prevent microcracks and then washed, etc. Subsequent processes are required.

On the other hand, the laser cleaving method that has recently been expected to have the future 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, post-processing 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 the laser cleaving method will be described. When glass is irradiated with a high energy density CO2 laser beam, absorption of the laser beam generally takes place at the irradiation spot, and cracks are generated radially as a result of rapid heating, and cleaving proceeds only in the traveling direction. I can't. 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.
This is shown in FIG. As shown in FIG. 1, when the cross-sectional shape of the laser beam 1 is formed into an appropriate one, a tensile tension 4 is generated only in a direction orthogonal to the moving direction of the laser beam 1 . The cleavage crack 5 is generated by the action of the tensile tension. In FIG. 1 , 2 is a compressive stress inside the glass, 3 is a coolant, and 6 is a glass plate. Note that the tensile tension 4 is generated even if the glass plate 6 is naturally cooled without spraying the cooling liquid 3 after heating by the laser beam 1, and the fracture crack 5 can be generated by the action of the tensile tension 4.
In the glass plate 6 shown in FIG. 2, when a trigger crack 8 is formed by a mechanical method at the starting point, the cleaving crack 5 is generated from the trigger crack 8 and can be advanced along the moving direction 7 of the laser beam 1. it can. 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 the tensile tension 4 . 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.
Japanese Patent Application No. 2003-363855 Japanese Patent Application No. 2004-156871 It can be said that the laser application to this glass cleaving is indispensable in processing of fine glass in general, for which demand will increase rapidly.

In the thermal stress cleaving of the glass with a CO2 laser beam irradiation, CO ₂ laser beam as shown in FIG. 3 it is absorbed only by the surface layer of the glass plate 6, not transmitted over the entire thickness of the glass plate 6. This is because the light absorption coefficient α of the glass at the CO 2 laser wavelength (10.6 μ) is remarkably large. The depth of cleaving with laser (referred to as laser scribe) is usually about 100 μm. In FIG. 3 , 9 is a laser scribe surface, and 10 is a break surface after laser scribe . Be made deeper than this Rezasukurai blanking plane 9, as long as the use of CO2 laser beam, is not possible even if though increasing the laser output. 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, as shown in FIG. 4 , the mechanical scribe surface is also usually of the same depth, and the glass is highly brittle and it is easy to mechanically cleave by applying stress according to this scribe line. Therefore, the increase in the scribe depth has not been required so far. This process of cleaving with the application of mechanical stress is called a break.

Thus, conventionally, the 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, the break surface 12 after mechanical scribing in FIG. 4 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 has been made to solve all of these problems, and a method for cleaving a brittle material for realizing laser scribe over the entire thickness (such scribe is hereinafter referred to as full cut), An object of the present invention is to provide a cleaving apparatus used for the cleaving method and a brittle material suitable for the cleaving method.

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, a surface heat source that reaches from the front to the back from the beginning. Is used. This difference is shown in FIG. 5 (a) and 5 ( b) show a conventional heat source and a heat source according to the present invention, respectively. In the conventional heat source of FIG. 5A, the heat conduction 13 by the laser beam 1 penetrates in the depth direction of the material but does not reach the back surface. On the other hand, in the present invention, by adding an impurity to the brittle material with respect to the wavelength of the irradiation laser light, the light absorption coefficient α of the brittle material is 0.105 / L <α <18. Since it is set so as to satisfy 42 / L, as shown in FIG. 5B, the laser beam 1 is absorbed into the brittle material and heated by the surface heat source 14 by the transmission laser beam absorption. For this reason, the scribe depth extends over the entire thickness, so that the break process is unnecessary.

Such transmission of the laser beam 1 can be performed by optimizing the absorption coefficient α for the laser beam of the brittle material .

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) Cutting 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) The cleaving 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) The multilayer structure board can be cleaved. 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. When the absorption coefficient of the material is α (cm−1), the propagation distance is x (cm), and the light intensity before and after propagating the distance x is I and I ₀ , the following relational expressions are established.
I = I ₀ × exp (−αx) (1)
If the required value of the transmission distance is known from the equation (1) , the necessary absorption coefficient α can be obtained. Next, the upper limit value, optimum value, and lower limit value of the absorption coefficient α are determined.

As a lower limit, a case where the laser beam 1 is transmitted through the glass plate thickness L by 90% is considered. At this time, a part of the energy is wasted, but a full cut can be realized sufficiently. In the formula (1) , if I / I ₀ = 0.9, α = 0.105 / L. This is the lower limit value of the absorption coefficient α .
As the upper limit, according to the inventors' experience, scribing up to 1/4 of the glass plate thickness often results in a full cut, so the upper limit is the condition for scribing up to 1/4 of the glass plate thickness. And set . Substituting I / I ₀ = 0.99 and x = L / 4 into the equation (1) yields α = 18.42 / L. This is the upper limit value of the absorption coefficient α .
The optimum value is the case where 50% of the laser beam 1 is absorbed by the glass plate 6 , and α = 0.963 / L in the same manner from the equation (1). As a result, it is understood that the glass plate 6 is fully cut when the light absorption coefficient α in the glass plate 6 is irradiated so as to satisfy 0.105 / L <α <18.42 / L.

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), the upper limit of this absorption coefficient α , The lower limit value and the optimum value are displayed 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
Plate thickness 0.07cm 1.50 9.90 263
Plate thickness 0.28cm 0.38 2.48 65.8
In the following embodiment, a technique for controlling the light absorption coefficient 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 FIG. 6 , 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 100 μm is possible, and it can be seen that heat conduction is helpful.

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 FIG. 6 , the absorption coefficient α is determined as a function of the wavelength λ . According to this, as described above, the absorption coefficient α was excessive at the CO 2 laser wavelength of 10.6 μm. In order to change the absorption coefficient α , the present invention adds impurities into the glass. However, it is necessary to select impurities that do not affect the transmission characteristics in the visible region and do not deteriorate the display characteristics of the glass for flat panel displays .
For this purpose, one embodiment of the present invention uses Yb, which is one of rare earth atoms, as an impurity. Since the energy level of the Yb atom consists of a ground level consisting of multiple sub-levels and one upper level, when glass is doped with Yb , it shows several peaks of absorption in the infrared of the wavelength range 900 to 1050 nm. In other wavelength regions, there is no absorption including visible light. For this reason, the glass doped with Yb is not colored and the display characteristics are not deteriorated when this glass is used for display. Yb atoms are stable elements because the f electrons in the N shell are surrounded by the electron group of the O shell, which is the outer shell. Therefore, the physical properties of the glass are not impaired for many years.

Rudiger et al. Published a paper entitled “Ytterbium-doped fiber amplifiers” that the absorption occurring in germanosilicate glass doped with Yb shows a peak at a wavelength of 975 nm and the absorption cross section is about 2.7 × 10 ⁻²⁰ cm ² . Announced from page 1049 to page 1056 of Vol. 33 (1997) issue 7 of the IEEE Journal of quantum electronics. FIG. 7 shows the wavelength characteristics of the emission cross section (dotted line) and the absorption cross section (solid line) 15 . In one embodiment of the present invention , among the absorptions that occur in the wavelength range of 900 to 1050 nm of Yb doped in the glass, the absorption cross-sectional area in which absorption occurs almost uniformly in the thickness direction in the glass of any thickness, and at this time The wavelength and further the Yb concentration are obtained by experiment and calculation, and the above-mentioned absorption is obtained by irradiating the glass doped with Yb with the InGaAs semiconductor laser light whose component ratio is adjusted so as to oscillate at this wavelength. Full cut is generated by generating uniform tensile stress.

Next, when Yb is mixed into the alkali-free glass in the form of Yb ₂ O ₃ , an expression is introduced that gives the above-mentioned optimum absorption coefficient α for the given glass thickness L. It is assumed that Yb ₂ O ₃ is added to the alkali-free glass at a weight ratio of 1%, and the component ratio and density of the glass are assumed as follows.
Component _{ratio: SiO 2: 60%, Al} 2 O 3: 20%, B 2 O 3: 19%, Yb 2 O 3: 1%

Density: ρ = 2.51g / cm ³
In case of this component ratio 1molg = 0.6 × (28 + 16 × 2) + 0.2 × (27 × 2 + 16 × 3) + 0.19 × (10.8 × 2 + 16 × 3) + 0.01 × (173 × 2 + 16 × 3) = 85g Therefore, the concentration of Yb atoms in the alkali-free glass is calculated as follows.
Yb concentration [pieces / cm ³ ] = number of Yb in 1 mol g × Avocado number × density / 1 mol g
= 3.56 × 10 ²⁰ / cm ³ (2)
Since there is no data on the absorption cross section of Yb atoms in alkali-free glass, the absorption coefficient α in the case of mixing 1% weight ratio of Yb ₂ O ₃ by using the above data at Rudiger et al. ^{= 3.56 × 1020 (cm- 3)} × 2.7 × 10-20 (cm 2) = a 9.6 (cm- ^1). When Yb ₂ O ₃ having a low weight ratio of 1 to 4% is mixed in non-alkali glass, even if it is assumed that 1 mol g does not change within this range, the component ratio does not change greatly. From the above, when the weight ratio for obtaining the optimum absorption coefficient α at which the transmittance in the case of the glass of thickness L (cm) is 50% is x%, α = 0.653 / L = 9.6 × x is obtained. The following equation is obtained as a relational expression between the optimum weight ratio x (%) of Yb ₂ O ₃ mixed for full cutting of an alkali-free glass of L (cm).
x x L = 0.072 (3)

The weight ratio x (%) of the mixed Yb ₂ O _{3 from which} the optimum absorption coefficient for full-cutting the alkali-free glass of each plate thickness described above from Formula (3) is calculated as follows.
Optimum weight ratio x (%) of mixed Yb ₂ O ₃ for full cut
Thickness 0.02cm 3.6
Plate thickness 0.07cm 1.0
Plate thickness 0.28cm 0.26

Above for the using absorption cross-section given in the literature in the absorption coefficient a germanate silicate glass InGaAs semiconductor laser according Yb ions mixed in alkali-free glass, the thickness of the glass a given L (cm) transparent The weight ratio x (%) of Yb ₂ O ₃ was determined so that the rate was 50%. If this process is generalized by the following procedure, a cleaving apparatus using a semiconductor laser can be configured. That is, (A) the transmittance which can be cleaved in the case of an arbitrary glass thickness L (cm) and the absorption cross section of the impurity Yb ₂ O ₃ for absorption in the wavelength range of 900 to 1,050 nm in the glass Find by experiment. Next, (B) the absorption coefficient that can achieve this transmittance is obtained from the mixing weight ratio x% of the impurity Yb ₂ O ₃ and the absorption cross section, and the former mixing weight ratio is concentration-quenched as described below. There is a lower concentration. Since Yb atoms are rare and expensive, considering the cost of the glass for display, it is preferable to determine the concentration around this lower limit. Therefore, (C) the wavelength of the absorption cross section where the above-mentioned absorption coefficient can be obtained at this concentration is selected from the experimental data of the wavelength versus absorption cross section, and the component ratio of InGaAs is determined so as to oscillate at this wavelength, and the cleaving semiconductor laser It is an oscillator. In summary of the above, the concentration of Yb ₂ O ₃ to be mixed with respect to the thickness of the glass to be cleaving L (cm) x (%) is determined by equation (4), (4) constant in the right-hand side of Equation Is determined by the above procedure from the absorption coefficient when the weight ratio of Yb ₂ O ₃ is 1% as the lower limit concentration obtained from the wavelength-dependent data of transmittance and absorption cross section for cleaving.
x × L = constant (4)

In the configuration of one embodiment of the present invention , the 4f electrons of Yb ions in the alkali-free glass are excited by absorbing the InGaAs semiconductor laser light, but the excited electrons are thermally emitted by non-radiative transition without emitting fluorescence. If it is not relaxed, thermal stress cannot be generated in the glass and it cannot be cleaved. R. Paschotta et al. “Lifetime quenching in Yb-doped
A paper entitled “fibers” was published in Optics Communications, Vol. 136 (1997), pages 375-378, and the Yb ion electrons doped in the glass were excited when the Yb concentration exceeded 1% by weight. It states that even if the defect (capture) concentration is low due to the rapid energy transfer between them, it is quenched and becomes a non-radiative transition. In the Yb ₂ O ₃ weight ratio x (%), the excited Yb ions do not fluoresce but relax by a non-radiative transition to increase the glass temperature and contribute to cleaving. It is not preferable to mix Yb ₂ O3 at a low concentration because it wastes rare and expensive rare earth Yb atoms and increases the cost of the final display device. An example of a combination of an impurity that can be desiredly cleaved with a limited impurity concentration and a laser absorbed by this is a Yb atom and an InGaAs semiconductor laser, and the addition of Yb atoms is a misch that contains Yb in addition to Yb ₂ O _3. Metal can also be used.

  As described above, the optimum combination is Yb atoms and InGaAs semiconductors, but the spirit of the present invention can also be realized by a combination of rare earth atoms such as Nd, Ho, and Eb and a semiconductor laser.

An example of a full-cut cleaving apparatus for realizing the present invention is shown in FIG. In FIG. 8 , reference numeral 16 denotes a laser stack composed of a large number of semiconductor laser elements, and reference numeral 17 denotes a fiber bundle in which fibers for guiding a laser beam from each element are bundled into one. The incident end 18 of the fiber bundle 17 is detachable as a connector. At the emission end 19, the fiber bundles 17 are arranged so that the laser beam cross-sectional shape can take various shapes. In FIG. 8 , the linear cross-sectional shape 20 is optimal for linear cleaving. For circular cutting with different diameters, the fiber exit ends are arranged in an arcuate arrangement 21 as shown in FIG. 9, but for the diameter control, an enlargement / reduction optical system as shown in FIG. 10 is provided between the exit end and the glass surface. System 22 is installed. For cleaving an arbitrary shape other than a straight line or an arc, an optimal fiber arrangement may be performed.

FIG. 11 shows another embodiment. In FIG. 11 , laser light is guided from the semiconductor laser stack 16 to one fiber using the coupling optical system 23. One laser beam that has passed through the fiber is converted into a cross-sectional shape optimum for cleaving by the cross-sectional shape control optical system 24. As such a cross-sectional shape controlling optical system 24 , the one described in Patent Document 1 or Patent Document 2 can be used.

When the laser beam passes through the glass while being absorbed, as is apparent from the equation (1), the heat generation amount decreases in an exponential manner in the depth direction of the glass. 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 increased and distributed exponentially from the front surface to the back surface, and heat generation is preferably made uniform in the depth direction. In order to increase the impurity concentration exponentially from the front surface to the back surface, as is well known in semiconductor technology, the concentration of a doping gas containing impurities during the doping of impurities can be increased exponentially with respect to the doping time. Good. (For example, refer to Japanese Patent Laid-Open No. 10-41549.)

  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 laser having excellent beam characteristics as the laser oscillator.

Even with a CO ₂ laser beam with strong surface absorption, if the output is increased to some extent, the heat source penetrates in the depth direction of the material by heat conduction. 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 high-speed and efficient full cut, as described with reference to FIG. 1, it is necessary to use cooling together and efficiently perform this cooling in the thickness direction. For that purpose, it is more effective to perform cooling not only on the glass surface but on both the front and back surfaces .

  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.

Conceptual diagram for explaining the principle of generation of compressive stress and tensile tension in glass by laser light heating and cooling used in the present invention Conceptual perspective view for explaining the glass breaking principle by the laser used in the present invention Conceptual perspective view explaining laser scribing of conventional glass Conceptual perspective view illustrating conventional glass mechanical scribe It is a conceptual perspective view explaining the state of heat generation inside the glass , (a) is a conventional method, (b) is a diagram according to the present invention. Optical absorption spectrum diagram of quartz glass for explaining the full-cut cleaving method of brittle material according to the present invention Wavelength characteristic diagram of absorption and emission cross sections of Yb ions in germanosilicate glass for explaining the full-cut cleaving method of brittle materials according to the present invention BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual perspective view showing a first embodiment of a full-cut cleaving apparatus for brittle materials according to the present invention. The conceptual perspective view which shows the 2nd Example of the full cut cleaving apparatus of a brittle material by this invention. The conceptual perspective view which shows the 3rd Example of the full cut cleaving apparatus of a brittle material by this invention. The conceptual perspective view which shows the 4th Example of the full-cut cleaving apparatus of a brittle material by this invention.

Explanation of symbols

1 laser beam
2 Compressive stress in glass 3 Coolant 4 Tensile tension in glass 5 Cleavage crack in glass 6 Glass plate 7 Laser beam moving direction 8 Trigger crack 9 Laser scribe surface 10 Break surface after laser scribe
11 Mechanical scribing surface 12 Break surface after mechanical scribing 13 Heat source by heat conduction
14 Heat source 15 by absorption of transmitted laser beam 15 Absorption cross section of Yb ions in germanosilicate glass 16 Semiconductor laser stack 17 Fiber bundle 18 Fiber bundle incident end 19 Fiber bundle exit end 20 Irradiation laser light 21 from linear array fiber exit end 21 Arc Irradiation laser light 22 from array fiber exit end Enlargement / reduction optical system 23 Fiber coupling optical system 24 Cross-sectional shape control optical system

Claims (7)

A brittle material cleaving method in which a brittle material is moved while being irradiated with laser light to generate a crack due to thermal stress in the brittle material, and the brittle material is cleaved over a sufficient thickness. From rare earth atoms selected so as to satisfy the inequality 0.105 / L <α <18.42 / L, where L (cm) is the thickness of the brittle material and α (cm ⁻¹ ) is the absorption coefficient. obtained by adding a laser beam-absorbing impurities by controlling the laser light absorption, cleaving method for brittle material and performing this by generating thermal stress by phonons generated when it breaking. The phonon is generated by exciting 4f electrons in ions of rare earth atoms , which are laser light absorbing impurities, with semiconductor laser light, and relaxing the excited 4f electrons to a ground state. A method for cleaving brittle materials.   The brittle material cleaving method according to claim 2, wherein the rare earth atom is Yb and the semiconductor laser is an InGaAs laser.   The method for cleaving a brittle material according to claim 2, wherein the rare earth atom is any one selected from Nd, Ho, and Er. The method for cleaving a brittle material according to any one of claims 1 to 4, wherein the concentration of the laser light absorbing impurity is a constant product of the weight ratio x and the thickness L of the brittle material. The method for cleaving a brittle material according to any one of claims 1 to 4, wherein the laser light absorbing impurity concentration is increased exponentially with respect to the depth direction of the material. The method for cleaving a brittle material according to claim 1, further comprising a step of cooling the brittle material after irradiating it with laser light.

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