JP2010100495A - Scribing method of thin sheet glass substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a scribing method which can ensure a scribe processing even if a thin sheet glass substrate has a sheet thickness of a substrate of a range of 0.1-0.4 mm. <P>SOLUTION: The scribing method of a thin sheet glass substrate comprises: computing the relation among a sheet thickness of a substrate when forming a scribe line, a processing condition of a scan rate, and a deformation state of a substrate by stress immediately after performing laser heating and cooling, based on a thermoelastic analysis by a finite element method; and performing laser irradiation and cooling in a state that the substrate is made to be adsorbed on a table equipped with a substrate adsorption mechanism when a scribe line is formed in a processing condition of a sheet thickness and a scan rate in which a substrate is deformed to form a concave on a laser irradiation face side. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser scribing method for a glass substrate, and more particularly to a scribing method for a very thin glass substrate having a plate thickness of 0.1 mm to 0.4 mm.

In the present invention, “scribe” refers to processing in which a crack not penetrating the substrate is advanced in the surface direction along a scribe line set on the substrate. A crack that progresses in the surface direction by scribing forms a scribe line.
“Scribe” is a process that forms a crack where the tip in the depth direction of the crack (the deepest part of the crack) remains in the substrate, causing a full cut (a state where the substrate is completely divided). The processing (called full cut processing) in which a crack penetrating from the front surface to the back surface of the substrate is not included.
Therefore, in order to completely divide the substrate along the scribe line formed by scribing, a break process for extending the crack in the depth direction is performed later.

  For convenience of explanation, “progress of crack” means that the crack grows in the surface direction of the substrate. Further, the penetration of cracks in the thickness direction (depth direction) of the substrate is referred to as “crack progress”.

When the glass substrate is irradiated with a laser beam while being scanned, a compressive stress is generated in a region heated by passing the beam spot of the laser beam. And a cooling stress is produced in the cooled area | region (cooling spot) by spraying a refrigerant | coolant to the position immediately after a beam spot passes, and cooling. Thus, a stress gradient is formed by forming a region where compressive stress is generated on the substrate and a region where tensile stress is generated close to each other.
In recent years, by using this stress gradient to form a crack in a glass substrate, a processing technique for performing scribing on the surface of the substrate (see, for example, Patent Document 1) or performing full-cut processing of a glass substrate has been used. (For example, refer to Patent Documents 2 and 3).

  When the glass substrate is divided by forming a stress gradient in the substrate by heating with laser irradiation and cooling immediately after the heating, as described above, the scribing process that requires the breaking process after the scribe line is formed, and the breaking There is a full cut process in which the substrate is divided without processing.

  Of these, full-cut processing is preferable in that the process can be simplified because the substrate can be divided without performing break processing, but when compared with the processing quality such as straightness of the processing end face that is finally obtained, compared to scribe processing It is inferior.

On the other hand, in the scribing process, the quality of the formed end face is very excellent. Moreover, since it is possible to perform a cross-scribing process that can be completely divided after forming a scribe line vertically and horizontally on the substrate, in a process of cutting a rectangular small substrate from a large area substrate in a liquid crystal panel manufacturing process, etc. Scribing is often used.
International Publication Number WO 03/008352 Japanese Patent Laid-Open No. 2004-155159 JP 2001-170786 A

In the field of manufacturing liquid crystal panels, glass substrates having a thickness of 1 mm or more have been used so far, but it is required to use as thin a substrate as possible in order to reduce the weight of the product. Specifically, the thickness of the substrate to be used is required to be 0.7 mm or less, more preferably in the range of 0.1 mm to 0.4 mm.
Therefore, in the glass substrate dividing processing technique, it is required to process such a thin plate substrate having a thickness of 0.4 mm or less by scribe processing instead of full cut processing.

  Whether scribe processing or full cut processing is achieved by laser irradiation depends on processing condition parameters such as heating conditions (irradiation time, irradiation power, scanning speed, etc.) and cooling conditions (refrigerant temperature, spray amount, spray position, etc.) In addition, it depends on the thickness of the glass substrate.

  Generally, when the glass substrate is thick, scribe processing can be established easily and reliably, but it is uncertain whether scribe processing will be established as the plate thickness becomes thinner than 0.7 mm. become. Furthermore, when the thickness is 0.4 mm or less, scribing becomes difficult, and when forcibly processed, there is a tendency that a full cut process is formed as a through crack. Hereinafter, the relationship between the thickness of the substrate and the processing mode will be described with reference to schematic diagrams.

<Thick board>
First, the case of a glass substrate having a large plate thickness will be described. The case where the plate thickness is thick here means that the substrate is sufficiently thick when the laser beam is irradiated on the upper surface of the substrate and the heat (heat) generated near the upper surface is transferred into the substrate. When the crack is formed on the surface, the heat transfer is stopped inside the substrate and the heat is not transferred to the lower surface of the substrate. Specifically, in the case of a glass substrate, heat transfer tends to stay inside the substrate when the thickness is 1 mm or more.

FIG. 9 is a schematic diagram for explaining a stress distribution generated in a substrate when a crack is developed and advanced by performing laser irradiation and cooling on a thick substrate having a plate thickness of 1 mm or more. FIG. 9A is a perspective view, and FIG. 9B is a plan view thereof.
10 (a), 10 (b), and 10 (c) show the temperature distribution and stress distribution in the AA ′, BB ′, and CC ′ sections of FIG. 9, respectively. It is a schematic diagram for demonstrating. From another viewpoint, FIGS. 10 (a), 10 (b), and 10 (c) show the time of temperature distribution and stress distribution at the same point due to the passage of the beam spot BS and the cooling spot CS. This represents a typical change.

  In FIG. 9, an elliptical beam spot BS is formed by a laser beam irradiated from a laser beam irradiation mechanism (not shown). An elliptical cooling spot CS is formed behind the beam spot BS by the refrigerant blown from a cooling mechanism (not shown). The beam spot BS and the cooling spot CS are scribed on the thick substrate GA from one end side where the initial crack TR is formed in advance toward the other end side while maintaining a positional relationship with a slight distance. Scan along the planned line SL.

  At this time, a compressive stress (indicated by a broken-line arrow in the figure) is generated in the vicinity of the upper surface of the thick substrate GA in the vicinity of the region heated by the passage of the beam spot BS due to the expansion due to heating. Next, a tensile stress (indicated by a solid arrow in the figure) due to the temperature distribution formed in the thick plate substrate GA is generated in the vicinity of the region cooled by the passage of the cooling spot CS.

Next, the stress and strain generated in the thick substrate GA will be described with reference to FIG.
In the thick substrate GA, the heating part HR is formed inside the substrate as shown in FIG. 10 (a) by heating due to the passage of the beam spot BS of the laser beam, and the heating part HR expands locally, thereby compressing. Stress (indicated by broken arrows in the figure) is generated.

Subsequently, the cooling part CR is formed in the vicinity of the surface as shown in FIG. 10 (b) due to the cooling by the passage of the cooling spot CS after a little delay, and the cooling part CR locally contracts, whereby the tensile stress ( (Indicated by solid arrows in the figure) occurs.
In the case of the thick substrate GA, the heating portion HR is gradually transmitted to the inside of the substrate, but since the substrate is thick, it does not reach the back surface when the crack is formed, and the heating portion HR stays inside the substrate. .

  Then, as shown in FIG. 10C, when the cooling heat is gradually transmitted from the surface layer of the thick substrate GA by forming the cooling portion CR, the cooling portion CR exists in the vicinity of the upper surface of the substrate, and the heating portion is located below the cooling portion CR. HR comes to exist. Since the heating part HR is a part where compressive stress is generated, it can be rephrased as an internal compressive stress field Hin existing inside the substrate.

  The internal compressive stress field Hin is formed on the thick substrate GA, and the tensile stress is formed near the upper surface of the substrate. As a result, the thick substrate GA is locally strained upward, and tensile stress is generated. A force (indicated by a one-dot chain line arrow in the figure) that bends the substrate in the same direction is generated on the upper surface of the substrate. In FIG. 10C, in order to show the direction of bending, the deformation due to the distortion generated in the thick substrate GA is exaggerated for convenience.

  As a result, a vertical crack C is formed on the upper surface of the thick substrate GA in the thickness direction (depth direction) from the upper surface of the substrate by a tensile stress and a force that causes the substrate to be convex upward. The This crack C forms a scribe line.

  In this case, since the internal compressive stress field Hin is formed in the thick plate substrate GA as described above, when the crack C reaches the internal compressive stress field, the progress is hindered, and the thick plate substrate The progress of crack C in GA stops in the vicinity of the internal compressive stress field.

  Therefore, in the thick substrate GA, it becomes difficult for the crack C to progress until it reaches the back surface, and the scribing process is performed in which a crack that does not penetrate near the upper surface of the substrate is formed. In other words, the scribe processing mode is a processing mode in which a crack is developed by a stress gradient caused by a temperature gradient between hot and cold formed in the thickness direction of the substrate.

<Thin board>
Next, the case of a thin glass substrate will be described. The case where the plate thickness is thin here means that the plate thickness of the substrate is sufficiently thin when the laser beam is irradiated on the upper surface of the substrate and the heat (thermal heat) generated near the upper surface of the substrate is transmitted into the substrate. When the substrate surface is cooled and cracks are formed, the heat reaches the lower surface. Specifically, when the plate thickness is 0.7 mm or less, particularly 0.4 mm or less, the heat applied to the upper surface of the substrate reaches the lower surface.

FIG. 11 is a schematic diagram for explaining a stress distribution generated in a substrate when a crack is developed and advanced by performing laser irradiation and cooling on a thin glass substrate having a thickness of 0.7 mm or less. FIG. 11A is a perspective view, and FIG. 11B is a plan view.
FIGS. 12A, 12B, and 12C illustrate the temperature distribution and stress distribution after laser irradiation in the DD ′, section EE ′, and section FF ′ sections of FIG. 11, respectively. It is a schematic diagram for doing.

  In FIG. 11, an elliptical beam spot BS is formed by a laser beam irradiated from a laser beam irradiation mechanism (not shown). An elliptical cooling spot CS is formed behind the beam spot BS by the refrigerant blown from a cooling mechanism (not shown). The beam spot BS and the cooling spot CS are scheduled to be divided from the one end side where the initial crack TR has been formed in advance toward the other end side while maintaining the positional relationship at a slight distance. Scan along line SL.

At this time, a compressive stress (indicated by a broken-line arrow in the figure) is generated in the vicinity of the upper surface of the thin substrate GB in the vicinity of the region heated by the passage of the beam spot BS due to the expansion due to the heating. Next, tensile stress (indicated by solid arrows in the figure) is generated in the vicinity of the region cooled by the passage of the cooling spot CS due to the shrinkage due to cooling.
As a result, a stress gradient is generated in the vicinity of the upper surface of the thin substrate GB, with the front (back side) being compressive stress and the rear (front side) being tensile stress.
In this case, the stress distribution near the upper surface of the thin substrate GB is less likely to cause a temperature difference in the vertical direction of the substrate due to the thin plate thickness, and as a result, cracks that tend to progress in the plane direction are likely to be formed. Become. The reason for this will be described based on the stress generated in the substrate.

FIG. 12 is a schematic diagram for explaining the stress and strain generated in the thin substrate GB.
In the thin substrate GB, the heating part HR is formed inside the substrate as shown in FIG. 12A by heating by passing the beam spot BS of the laser beam irradiated on the upper surface of the substrate, and the heating part HR expands locally. As a result, compressive stress (indicated by broken line arrows in the figure) is generated. In this case, since the thickness of the substrate is thin, the heated portion HR immediately reaches the lower surface of the substrate GB.

Next, the cooling region CR is formed in the vicinity of the surface as shown in FIG.
In the case of the thin substrate GB, the cold part CR immediately reaches the center of the substrate GB.

  When the cooling heat is further transmitted, the cooling portion CR reaches the lower surface of the thin plate substrate GB as shown in FIG. As described above, in the thin substrate GB, the heat and cold are quickly transmitted from the upper surface to the lower surface of the thin substrate GB, so that it is difficult to maintain the stress gradient caused by the temperature gradient in the thickness direction of the substrate. Therefore, scribing is difficult to achieve with a thin substrate. Even if it is true, the process window becomes narrow and stable machining is difficult.

  For this reason, in the thin-plate substrate GB, the substrate is caused by a stress gradient caused by a temperature difference generated in the front-rear direction along the planned dividing line due to the existence of the region heated to the lower surface by the beam spot BS and the region cooled to the lower surface by the cooling spot. The crack will progress. That is, in the state where the heating part HR and the cooling part CR are present from the upper surface to the lower surface of the thin plate substrate GB, tensile stress is generated from the upper surface to the lower surface of the thin plate substrate GB in the vicinity of the boundary between the heating site HR and the cooling site CR. It will be. As a result, cracks reaching from the upper surface to the lower surface of the thin plate substrate proceed in the direction from the cooling region CR to the heating region HR. Therefore, the full cut processing mode is easily established.

As described above, scribing is performed when the thickness of the substrate is large. However, as the thickness of the substrate is decreased, full-cut processing is likely to occur, and scribing becomes difficult.
Therefore, it is necessary to increase the thickness of the glass substrate in order to enter a scribe processing mode in which a scribe line can be reliably formed while avoiding full cut processing. For the processing of very thin substrates with a plate thickness of 0.4 mm or less, slicing by scribing should either select processing conditions from a narrow process window range, or give up because scribing is difficult. It was premised on cutting by cutting.

Therefore, the present invention can surely scribe even a thin glass substrate having a thickness of 0.1 mm to 0.4 mm, which has been thought to be impossible to scribe until now. An object is to provide a scribing method.
Another object of the present invention is to widen the process window under the processing conditions capable of performing the scribe processing in the thin glass substrate having the above thickness.

When the substrate is heated by laser irradiation and then cooled, tensile stress is generated on the laser irradiation surface (substrate upper surface) side in the substrate at the time when a crack is formed immediately after cooling. For this reason, it has been considered that the substrate after being heated and cooled is deformed upward (convex to the laser irradiation surface side).
However, laser scribing of a plurality of glass substrates with different plate thicknesses was performed to experimentally determine the effect of the plate thickness, and a two-dimensional thermoelastic analysis by a finite element method based on the experimental results was performed. As a result, when the thickness of the substrate is thinner than 0.4 mm and the scanning speed of the laser beam is slow (that is, when the time difference between heating and cooling becomes large), the substrate may be recessed upward depending on the processing conditions. It was discovered that it was deformed (concave on the laser irradiation surface side). And if it becomes such processing conditions, since it is thought that a crack progress and a crack progress are suppressed and a crack is no longer formed, in the present invention, the following scribing methods were devised.

  The glass substrate scribing method of the present invention made to solve the above-mentioned problems does not cause thermal damage to the substrate against the scribe line on the thin glass substrate having a plate thickness of 0.1 mm to 0.4 mm. By irradiating along the scribe line while relatively moving the laser beam so as to be heated at a temperature, and then cooling, a crack that does not penetrate the substrate proceeds on the scribe line to form a scribe line. A scribing method for a thin glass substrate, based on thermoelastic analysis by a finite element method, immediately after the substrate thickness when forming a scribe line, processing conditions for scanning speed, and laser heating and cooling Calculate the relationship with the deformation state of the substrate due to the stress of the plate, and add the plate thickness and scanning speed at which the substrate deforms to become concave on the laser irradiation surface side. When forming a scribe line in the condition, the substrate on the table with a substrate suction mechanism in a state of being adsorbed, to perform the cooling and the laser irradiation.

Here, the “temperature not causing thermal damage” refers to a temperature that is excessively heated when the beam spot passes and remains damaged such as deformation and melting that can be visually confirmed. Specifically, for example, in a soda glass substrate, it may be lower than 500 ° C. (see FIG. 5) obtained experimentally as described later.
According to the present invention, when processing a thin glass substrate having a plate thickness of 0.1 mm to 0.4 mm, the substrate is sucked and fixed to the table by the substrate suction mechanism. Thereby, the force to tear in the lateral direction with respect to the planned scribe line is suppressed by the stress gradient in the front-rear direction along the planned scribe line, and a full cut state is prevented.

  On the other hand, in a substrate that is deformed to be concave on the laser irradiation surface side, the tensile stress generated on the surface on the laser irradiation side is alleviated by the deformation of the substrate, so that cracks are difficult to propagate only on the surface of the substrate. The crack does not progress at all or even if the crack progresses, it becomes a full cut. However, by fixing the substrate with the substrate adsorption mechanism, it becomes possible to develop cracks (with the suppression of full cut) by eliminating the bending that has been recessed upward, and as a result, it has not been possible so far Scribe processing can be established under the appropriate processing conditions.

  According to the present invention, even a thin substrate having a plate thickness of 0.1 mm to 0.4 mm can be made scribe processing instead of full cut processing, and the process window capable of scribe processing can be widened. it can.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Device configuration]
First, the apparatus configuration for carrying out the scribing method of the present invention will be described. Here, a general-purpose laser scribing apparatus equipped with a substrate suction mechanism is used. FIG. 1 is a diagram showing a schematic configuration of a main part of a laser scribing apparatus LS used in the present invention. FIG. 2 is a diagram showing the relationship between the plate thickness of the glass substrate, the scanning speed of the beam spot and the cooling spot obtained by thermoelastic analysis by the finite element method described later, and the deformation state of the substrate.

  In the present invention, a table 10 provided with a vacuum suction mechanism is used. On the upper surface of the table 10, there is provided a plate 11 made of a porous member (for example, porous ceramic) on which the substrate G is placed. The table 10 is in close contact with the periphery of the plate 11, has a bottom surface, a body 12 in which a hollow space 12 a is formed between the table 11, a flow path 13 connected to the hollow space 12 a, and an external flow path 14. A vacuum pump 16 that depressurizes the hollow space 12a via a plug 15, a flow path 13, an external flow path 14, and an opening degree adjustment valve 16a; a flow path 13, an external flow path 14, and a pressure adjustment valve 17a. And an air source 17 for sending pressurized air to the hollow space 12a. The table 10 can suck the glass substrate G placed on the plate by operating the vacuum pump 16, and can release the suction state by sending air from the air source 17. It is.

  Above the plate 11 is a scribe that integrally scans a laser irradiation mechanism 21 that irradiates an elliptical beam spot on the substrate and a cooling mechanism 22 that jets a coolant to form an elliptical cooling spot on the substrate. A head 23 is arranged. The scribe head 23 can be controlled at a scanning speed between 10 mm / second and 500 mm / second by a scanning drive mechanism and a control unit (not shown).

[Scribe method]
In the present invention, a glass substrate having a plate thickness of 0.1 mm to 0.4 mm is an object. Until now, it was difficult to scribe a glass substrate in this thickness range, and it was necessary to select processing conditions from a narrow process window. In particular, it has been considered that the scribe process cannot be performed at all when the thickness of the substrate is reduced and the process window is narrowed to about 0.2 mm.
However, by performing an experiment to be described later and a two-dimensional thermoelastic analysis by a finite element method based on the result of the experiment, as shown in FIG. It has been found that there are processing conditions for scanning speed. Therefore, in the scribing method of the present invention, the substrate is sucked by the substrate suction mechanism under the processing conditions of the plate thickness and the scanning speed that cause the concave deformation on the laser irradiation surface side, and the processing is performed within the range of the above processing conditions. By doing so, a full cut is prevented and a force in the same direction as the tensile stress is applied to the upper surface side of the substrate. As a result, scribing can be reliably performed.

[Experiment]
In order to examine the influence of the glass substrate thickness in laser scribe processing, experiments were conducted on the range of processing conditions in which laser scribe can be performed on glass substrates having thicknesses of 1.1 mm, 0.7 mm, 0.55 mm, and 0.4 mm. Based on the results, a two-dimensional thermoelastic analysis by the finite element method was performed.

The experimental method will be described. A 300 mm × 400 mm soda glass substrate is fixed to a vacuum suction mechanism (see FIG. 1) to make it difficult to be fully cut. An initial crack serving as a starting point for scribing is previously provided at the end of the glass substrate with a cutter wheel. A CO ₂ laser is used as the laser light source, and it is shaped so as to form an elliptical beam spot on the glass surface. The cooling spot is formed by a water jet and is formed near the rear end of the beam spot. The positional relationship between the beam spot and the cooling spot is the same as that of the beam spot BS and the cooling spot CS shown in FIGS. 9B and 11B, and the dimensional relationship is as follows.
Beam spot long axis YA: 22 mm
Beam spot minor axis XA: 2.1 mm
Long axis YB of the cooling spot: 3.0 mm
Short axis YA of the cooling spot: 2.0 mm
Distance d between beam spot center and cooling spot center: 10 mm

FIG. 3 shows data (FIGS. 3 (a1) to 3 (d1)) obtained as the scanning speed v with respect to the laser output P, and the crack depth with respect to the laser output P. This is data (Fig. 3 (a2) to Fig. 3 (d2)) for which the depth Dc is obtained.
When the plate thickness h is 0.4 mm, as shown in FIG. 3 (d1), scribing is possible even at the maximum scanning speed of 500 mm / sec. 3 (a1) to FIG. 3 (d1), the x mark on the high speed side represents the state where the progress of the crack is stopped, and the x mark on the low speed side represents the state where the thermal damage remains on the glass substrate. Yes.

In any plate thickness, as the laser output increases, the scribing scanning speed tends to increase. In addition, the processing conditions (x mark on the low speed side) where the thermal damage occurred are almost the same regardless of the plate thickness.
As for the crack depth Dc for each laser output in FIGS. 3A2 to 3D2, the deeper one corresponds to the low speed side of the scanning speed and the shallower one corresponds to the high speed side.

The processing conditions (x mark on the high speed side) in which the crack progress stopped when the plate thickness h is 1.1 mm are wide on the low output side of the laser, but narrow on the high output side. When the scanning speed is 350 mm / second or more, scribing cannot be performed.
On the other hand, when the plate thickness h is 0.4 mm, the range of scanning speed that can be scribed on the low output side is narrow, and when the laser output is 30.4 W, scribing cannot be performed at all scanning speeds. On the other hand, the scanning speed range in which scribing on the high output side is wide is possible, and scribing is possible even at a scanning speed of 500 mm / sec.
That is, as the plate thickness h increases, scribing becomes more difficult on the high speed side of the scanning speed, and as the plate thickness h decreases, scribing becomes difficult on the low speed side.

FIG. 4 is a diagram showing the results of arranging the crack depth Dc under the five processing conditions in which thermal damage did not occur with respect to the plate thickness. The conditions under which the progress of cracks stopped and scribing could not be performed are indicated by crosses.
Under the conditions of a laser output of 71.0 W and a scanning speed of 320 mm / second, scribing cannot be performed at a plate thickness of 1.1 mm. Under the conditions of a laser output of 30.4 W and a scanning speed of 80 mm / second, the plate thickness is 0.4 mm. You cannot scribe. Except for these, scribing is possible at all plate thicknesses.

Next, based on the processing conditions obtained in the experiment, a thermoelastic analysis by the finite element method was performed by the following method, and the influence of the plate thickness on the scribing processing conditions was examined. The finite element method analysis program is Quick Welder manufactured by the Center for Computational Mechanics.
The element is divided with the laser irradiation surface as the xy coordinate, the y axis as the scribe direction, and the z axis as the plate thickness direction. In the element division, the division minimum value in the beam direction (y direction) was 3.7 μm, and the minimum winning value in the plate thickness direction (z direction) was 2.7 μm.
The physical property values of the soda glass substrate are as follows.
Density: 2520kg / m ²
Specific heat: 800J / kgK
Thermal conductivity: 1.03 W / mK
Thermal expansion coefficient: 8.7 × 10 ⁻⁶ K ⁻¹
Young's modulus: 71.6 GPa
Poisson's ratio: 0.23
Softening temperature: 720 ° C to 730 ° C
Bending strength: 49MPa

  The time step was 0.25 mm / v, which is the time obtained by dividing 0.25 mm by the scanning speed v. The size of the beam spot and the cooling spot was the same elliptical shape as described above, and had a Gaussian distribution.

In the two-dimensional heat conduction analysis on the xz plane, the center of the laser beam was scanned from the position y = -15 mm in the y direction, and the heating and cooling conditions were changed with time. At this time, the amount of heat input to the glass was set to 0.798 P (W) with respect to the laser output P (W) in consideration of the attenuation rate of the optical system and the reflectance of the glass. Further, the heat transfer coefficient α ₀ in the cooling region was set to 10 ⁵ W / m ² K.
Subsequently, using the obtained temperature field, a two-dimensional thermoelastic analysis of the xz plane was performed as a plane stress problem assuming that σ _yy = τ _yx = τ _yz = 0. The irradiation end of the laser beam was constrained in the x direction, and the other end was constrained in the x direction and the z direction, respectively.
In the following description, T _max is the maximum temperature reached on the glass substrate surface during laser scribing, and σ _tmax is the maximum tensile stress of σ _xx generated on the glass substrate surface in the cooling region.

Thermoelastic analysis was performed on glass substrates having a thickness of 0.4 mm, 0.55 mm, 0.7 mm, and 1.1 mm under processing conditions of output and scanning speed at which laser scribing was possible.
FIG. 5 is a diagram showing the results of thermoelastic analysis. FIGS. 5A to 5D show the analysis results of plate thicknesses of 1.1 mm, 0.7 mm, 0.55 mm, and 0.4 mm, respectively.
In the drawing, the upper plot point group represents the maximum temperature T _max reached on the glass substrate surface (right vertical axis), and the lower plot point group represents the maximum tensile stress σ _tmax on the glass substrate surface (left). Vertical axis).
The x mark on the high speed side of each plot point group corresponds to the processing conditions in which the crack progress of the laser scribe stopped in the middle of FIGS. 3 (a1) to 3 (d1). Corresponds to the processing conditions that caused thermal damage.

At each plate thickness, when the laser output is constant, T _max increases as the scanning speed decreases. At any laser output, the upper limit value of T _max is almost constant (about 500 ° C.) regardless of the scanning speed. Therefore, it can be said that the glass is not thermally damaged below the upper limit of _Tmax .

On the other hand, when the laser output is constant, σ _tmax decreases as the scanning speed increases. This is the reason why the crack depth is shallow on the high speed side in FIGS. 3 (a2) to 3 (d2). The lower limit of σ _tmax at any laser output is almost constant (about 65 MPa) regardless of the scanning speed. Therefore, it can be said that the crack in laser scribing progresses above the lower limit of σ _tmax .
Thereby, from the result of the thermoelastic analysis, regardless of the plate thickness, the processing conditions capable of laser scribing can be estimated from the maximum surface temperature T _max and the maximum tensile stress σ _{tmax in the} cooling region.

Next, the influence of the plate thickness in laser scribe will be described.
FIG. 6 is a diagram showing a temperature distribution and a deformed state of the xz plane (however, one half on one side of the planned scribe line) at the position where the maximum tensile stress σ _{tmax is} generated in the cooling region. The left end of each figure corresponds to the position directly under the scribe line. Therefore, the upper left corner is the laser incident position. On the opposite side of the scribe line, a temperature distribution and a deformed state are formed in which these figures are mirror-symmetrical due to symmetry.
The inclination in each figure represents the magnitude of the substrate deformation and the deformation direction (convex upward or concave upward). In other words, the downward-right view is an upward convex deformation state, and the upward-right view is an upward concave deformation state.

  Here, for a substrate having a plate thickness of 1.1 mm, 0.7 mm, 0.55 mm, and 0.4 mm, (a) laser output P = 30.4 W, scanning speed V = 80 mm / second, and (b) Processing conditions of laser output P = 52.8 W, scanning speed V = 80 mm / second, and (c) laser output P = 71.0 W, scanning speed V = 320 mm / second are shown.

As for the temperature distribution on the xz plane, a high temperature region remains in the glass immediately under cooling. The lower the scanning speed, the deeper the high temperature region, and heat is transferred to the inside.
Among these, in particular, under the processing conditions where the plate thickness is 0.4 mm, the laser output P is 30.4 W, and the scanning speed V is 80 mm / second, the temperature of the back surface rises to about 200 ° C. And in the board | substrate of this process condition, unlike others, it deform | transforms into a concave upward.

FIG. 7 is a diagram showing a stress distribution corresponding to FIG. A tensile stress is generated on the surface of the cooling region, a high temperature region is formed inside the substrate immediately below the cooling region, and a compressive stress field is formed.
The depth of the internal compressive stress field (relative depth with respect to the plate thickness) when the plate thickness is 0.4 mm, the laser output P is 30.4 W, and the processing speed is V = 80 mm / sec. , Deeper than other processing conditions. This is considered to be a cause of the substrate being deformed upwardly.

FIG. 8 is a diagram showing the maximum tensile stress σ _tmax in the cooling region under the five processing conditions shown in FIG. Under any processing condition, σ _tmax is convex upward, and the maximum plate thickness tends to shift to a thinner side as the scanning speed increases, and to a thicker side as the speed decreases. For example, under the processing conditions of laser output P = 71.0 W and scanning speed v = 320 mm / second, the plate thickness at which the maximum tensile stress σ _tmax is maximized approaches 0.4 mm. It is considered that the maximum tensile stress σ _tmax when the plate thickness is 1.1 mm is smaller than the lower limit value at which the crack progresses, and as a result, scribing can no longer be performed.
The laser output P = 30.4W, thickness of maximum tensile stress sigma _tmax is maximized under the condition of scan speed V = 80 mm / sec equal to or greater than 1.1 mm. As a result, it is considered that the maximum tensile stress σ _tmax with a plate thickness of 0.4 mm is smaller than the lower limit value at which the crack progresses, and scribing can no longer be performed.

FIG. 2 described above is a diagram showing the deformation state of the substrate (upwardly convex state and upwardly concave state) using the plate thickness and the scanning speed as parameters.
When the results of the thermoelastic analysis described above are arranged, the state in which the substrate is convex upward (right side from the boundary) and the state in which the substrate is concave upward (left side from the boundary) are separated by using the following formula (1) as a boundary. .
y = 7.5X ^-2.8 (1)
y is the scanning speed (mm / sec), x is the plate thickness (mm)

  For example, when the substrate thickness is 0.4 mm, the scanning speed is 320 mm / second, and when it is 160 mm / second, it is deformed upward, but when the scanning speed is 80 mm / second, it is concave upward. It will be transformed into.

When the thickness of the substrate is 0.1 mm to 0.4 mm, the range in which the substrate is concave in Formula (1) becomes dominant.
As a result, as described above, in the range where the concave state is formed, the substrate suction mechanism is brought into close contact with the table to suppress the deformation of the substrate into the concave state, so that a tensile stress is applied to the upper surface of the substrate. It is possible to make the cracks progress and progress easily. Therefore, a process window that can be scribed is expanded. In order to suppress the deformation of the substrate in the scribe line, it is necessary to suck the vicinity of the scribe line, but scribe processing can be performed by using a table having a vacuum suction mechanism provided with a porous member on the upper surface. Confirmed that the process window can be expanded. If the suction holes are within a range of about 0.5 mm from the planned scribe line, a process window capable of performing scribing while suppressing deformation of the substrate even on a suction table provided with a plate material provided with a plurality of suction holes on the upper surface is expanded. However, since it is not necessary to align the suction hole of the table with the scribe line, it is preferable to use a vacuum suction table having a porous member on the upper surface.

  By the way, in the region that protrudes upward, if the substrate is adsorbed with an adsorption mechanism to avoid becoming a full cut state, a force in the same direction as the compressive stress is applied to the position of the planned scribe line by adsorbing the substrate. However, since the scribing process becomes difficult, it has been proved that a method using a scribing method for processing in a region where the thin plate substrate is concaved is significant.

  The present invention is used when scribing a thin glass substrate having a plate thickness of 0.1 mm to 0.4 mm.

The figure which shows the structure of the principal part of the laser scribing apparatus used in order to implement the scribing method of this invention. The figure which shows the board | substrate thickness calculated | required by the thermoelastic analysis by a finite element method, the scanning speed of a beam spot and a cooling spot, and the deformation | transformation state of a board | substrate. The data (FIG. 3 (a1) to FIG. 3 (d1)) obtained as the scanning speed v with respect to the laser output P as the laser scribing processing conditions at each plate thickness h and the crack depth Dc with respect to the laser output P were obtained. The figure which shows data (FIG. 3 (a2)-FIG.3 (d2)). The figure which shows the result which arranged the crack depth Dc with respect to plate | board thickness. The figure which shows the result of a thermoelastic analysis. It shows the deformation state and the temperature distribution of the x-z plane at the maximum tensile stress sigma _tmax generation position of the cooling zone. The figure which shows the stress distribution corresponding to FIG. The figure which arranged the maximum tensile stress (sigma) _tmax of the cooling region in order regarding plate _{| board} thickness. The schematic diagram for demonstrating the stress distribution which arises in a board | substrate when a crack progresses and advances by performing laser irradiation and cooling with respect to a thick board | substrate. The schematic diagram for demonstrating the temperature distribution and stress distribution in the A-A 'cross section of FIG. 9, B-B' cross section, and C-C 'cross section. The schematic diagram for demonstrating the stress distribution which arises in a board | substrate when a crack progresses and advances by performing laser irradiation and cooling with respect to a thin board | substrate. The schematic diagram for demonstrating the temperature distribution and stress distribution in D-D 'of FIG. 11, the cross section E-E', and the cross section F-F 'cross section.

Explanation of symbols

10: Table 11: Plate (porous member)
12: Body 16: Vacuum pump 17: Air source 21: Laser irradiation mechanism 22: Cooling mechanism 23: Scribe head LS: Laser scribing device G: Glass substrate

Claims (3)

Irradiation along the planned scribe line while moving the laser beam relative to the planned scribe line of a thin glass substrate with a thickness of 0.1 mm to 0.4 mm at a temperature that does not cause thermal damage to the substrate. Then, by cooling, a scribing method for a thin glass substrate that forms a scribe line so that a crack that does not penetrate the substrate proceeds on the scribe line,
Based on thermoelastic analysis by the finite element method, the relationship between the processing conditions of the substrate thickness and scanning speed when forming the scribe line, and the deformation state of the substrate due to the stress immediately after the laser heating and cooling are performed To calculate
When the scribe line is formed under the processing conditions of the plate thickness and the scanning speed at which the cooled substrate is deformed to be concave on the laser irradiation surface side, the substrate is adsorbed on a table equipped with a substrate adsorption mechanism. A scribing method characterized by performing laser irradiation and cooling in a state. Relationship between substrate thickness and scanning speed processing conditions when forming a scribe line, and deformation state of the substrate immediately after laser heating and cooling, based on finite element method thermoelastic analysis The scribing method according to claim 1, wherein is a formula (1).

y = 7.5x ^-2.8 (1)
Here, y is the scanning speed (mm / sec), x is the plate thickness (mm)   The scribing method according to claim 1, wherein the substrate adsorption mechanism adsorbs the substrate via a porous member disposed on the upper surface of the table.