Scribing method of thin sheet glass substrate

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 a process of advancing cracks that do not penetrate the substrate along a scheduled scribing line set on the substrate in the plane direction. Cracks that have progressed in the plane direction due to scribe will form a scribe line. In addition, "scribe" refers to the process of forming a crack in which the tip (the deepest part of the crack) in the depth direction of the crack stays in the substrate, and causes a full cut (a state in which the substrate is completely divided). , Processing that forms cracks penetrating from the front surface to the back surface of the substrate (called full-cut processing) is not included. Therefore, in order to completely divide the substrate along the scribe line formed by the scribe, a break process for developing cracks in the depth direction is performed later.

For convenience of explanation, "progress of cracks" means that cracks grow 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 growth".

When the glass substrate is irradiated while scanning the laser beam, compressive stress is generated in the region where the beam spot of the laser beam passes and is heated. Then, by spraying the refrigerant at the position immediately after the beam spot has passed to cool it, tensile stress is generated in the cooled region (cooling spot). In this way, the stress gradient is formed by forming the region where the compressive stress is generated on the substrate and the region where the tensile stress is generated close to each other. In recent years, processing techniques such as scribing the surface of a glass substrate by forming cracks on the glass substrate using this stress gradient (see, for example, Patent Document 1) or full-cutting of a glass substrate have been used. (See, for example, Patent Documents 2 and 3).

When trying to divide a glass substrate by forming a stress gradient on the substrate by heating by laser irradiation and cooling immediately after heating, as described above, scribe processing that requires break processing after forming a scribe line and break 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 comparing the processing quality such as straightness of the finally obtained processed end face, it is compared with scribe processing. Is inferior.

On the other hand, the scribe processing is very excellent in the quality of the end face formed. Moreover, since it is possible to perform cross-scribing processing that can completely divide after forming vertical and horizontal scribe lines on the substrate, in the manufacturing process of liquid crystal panels, etc., in the processing of cutting out a small square substrate from a large-area substrate, Scribing is often used.<patcit num="1"><text>International Publication No. WO 03/008352 Gazette</text></patcit><patcit num="2"><text>Japanese Unexamined Patent Publication No. 2004-155159</text></patcit><patcit num="3"><text>Japanese Unexamined Patent Publication No. 2001-170786</text></patcit>

<p> In the field of manufacturing liquid crystal panels, glass substrates with a thickness of 1 mm or more have been used so far, but in order to reduce the weight of products, it is required to use as thin a substrate as possible. Specifically, it is required that the thickness of the substrate to be used is 0.7 mm or less, and more preferably in the range of 0.1 mm to 0.4 mm. Therefore, in the glass substrate dividing processing technology, it is required to process such a thin plate substrate having a plate thickness of 0.4 mm or less by scribe processing instead of full cutting processing.</p><p> Whether scribe processing or full-cut processing is established by laser irradiation is a processing condition parameter such as heating conditions (irradiation time, irradiation power, scanning speed, etc.) and cooling conditions (refrigerant temperature, spray amount, spray position, etc.). At the same time, it depends on the thickness of the glass substrate.</p><p> Generally, when the plate thickness of the glass substrate is thick, the scribe processing can be easily and surely established, but it is uncertain whether the scribe processing is established as the plate thickness becomes thinner than 0.7 mm. Become. Further, when it is 0.4 mm or less, scribe processing becomes difficult, and if it is forcibly processed, it tends to be a through crack and a full cut process is performed. Hereinafter, the relationship between the thickness of the substrate and the machining mode will be described with reference to a schematic diagram.</p><p> &lt;Plate board&gt; First, the case of a thick glass substrate will be described. The case where the plate thickness is thick here means that when the upper surface of the substrate is irradiated with a laser beam and the heat (heat) generated near the upper surface is transferred into the substrate, the thickness of the substrate is sufficiently thick, so that the substrate is thick. When cracks are formed on the surface, heat transfer stays inside the substrate and 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 plate thickness is 1 mm or more.</p><p> FIG. 9 is a schematic diagram for explaining the stress distribution generated on a thick plate substrate having a plate thickness of 1 mm or more when cracks are propagated and advanced by laser irradiation and cooling. FIG. 9 (a) is a perspective view, and FIG. 9 (b) is a plan view thereof. In addition, FIGS. 10 (a), 10 (b) and 10 (c) show the temperature distribution and stress distribution in the A-A'cross section, B-B'cross section and C-C' cross section of FIG. 9, respectively. It is a schematic diagram for demonstrating. From another point of view, FIGS. 10 (a), 10 (b) and 10 (c) show the time of the temperature distribution and stress distribution at the same point due to the passage of the beam spot BS and the cooling spot CS. Represents a change.</p><p> In FIG. 9, an elliptical beam spot BS is formed by a laser beam emitted from a laser beam irradiation mechanism (not shown). Behind the beam spot BS, an elliptical cooling spot CS is formed by a refrigerant sprayed from a cooling mechanism (not shown). While maintaining the positional relationship between the beam spot BS and the cooling spot CS at a slight distance, scribe the plate substrate GA from one end side to the other end side in which the initial crack TR is formed in advance. It is scanned along the scheduled line SL.</p><p> 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 plate substrate GA due to the influence of expansion due to heating in the vicinity of the region heated by the passage of the beam spot BS. Next, a tensile stress (indicated by a solid arrow in the figure) due to the temperature distribution formed on the plate substrate GA is generated in the vicinity of the region cooled by the passage of the cooling spot CS.</p><p> Next, the stress and strain generated inside the thick plate substrate GA will be described with reference to FIG. In the thick plate substrate GA, the heated portion HR is formed inside the substrate by heating due to the passage of the laser beam through the beam spot BS, and the heated portion HR is locally expanded to be compressed as shown in FIG. 10 (a). Stress (indicated by the dashed arrow in the figure) is generated.</p><p> Subsequently, after a short delay, the cooling heat generated by the passage of the cooling spot CS causes the cooling site CR to be formed near the surface as shown in FIG. 10 (b), and the cooling site CR locally contracts to cause tensile stress (tensile stress (). (Indicated by the solid arrow in the figure) occurs. In the case of the thick plate substrate GA, the heated portion HR is gradually transmitted to the inside of the substrate, but because the substrate is thick, it does not reach the back surface when cracks are formed, and the heated portion HR remains inside the substrate. ..</p><p> Then, as shown in FIG. 10 (c), when cold heat is gradually transferred from the surface layer of the thick plate substrate GA by forming the cooling portion CR, the cooling portion CR exists near the upper surface of the substrate, and the heating portion is below the cooling portion CR. HR will exist. Since this heating site HR is a site where compressive stress is generated, it can be rephrased as the internal compressive stress field Hin existing inside the substrate.</p><p> An internal compressive stress field Hin is formed in the thick plate substrate GA, and a tensile stress is formed in the vicinity of the upper surface of the substrate. As a result, the thick plate substrate GA is locally subjected to upwardly convex strain, and the tensile stress is generated. A force that bends the substrate in the same direction as the above (indicated by the one-point chain line arrow in the figure) is generated on the upper surface of the substrate. In addition, in FIG. 10 (c), since the direction of bending is shown, the deformation due to the strain generated in the thick plate substrate GA is exaggerated for convenience.</p><p> As a result, cracks C perpendicular to the upper surface of the thick plate substrate GA in the thickness direction (depth direction) are formed on the upper surface of the thick plate substrate GA due to the tensile stress and the force for bending the substrate so as to be convex upward. To. This crack C forms a scribe line.</p><p> In this case, since the internal compressive stress field Hin is formed inside the thick plate substrate GA as described above, when the crack C reaches this internal compressive stress field, the progress is hindered and the thick plate substrate The growth of crack C in GA will stop near the internal compressive stress field.</p><p> Therefore, in the thick plate substrate GA, it becomes difficult for the crack C to propagate until it reaches the back surface, and scribe processing is performed in which a crack that does not penetrate is formed in the vicinity of the upper surface of the substrate. In other words, the scribe processing mode is a processing mode in which cracks are propagated by a stress gradient caused by a temperature gradient of heat and cold formed in the thickness direction of the substrate.</p><p> &lt;Thin plate board&gt; Next, the case of a thin glass substrate will be described. The case where the plate thickness is thin here means that when the laser beam is applied to the upper surface of the substrate and the heat (heat) generated near the upper surface of the substrate is transferred into the substrate, the plate thickness of the substrate is sufficiently thin. This refers to the case where the heat reaches the lower surface when the surface of the substrate is cooled and cracks are formed. Specifically, when the plate thickness is 0.7 mm or less, particularly 0.4 mm or less, the heat given to the upper surface of the substrate reaches the lower surface.</p><p> FIG. 11 is a schematic diagram for explaining the stress distribution generated on a thin glass substrate having a thickness of 0.7 mm or less when cracks are propagated and progressed by laser irradiation and cooling. 11 (a) is a perspective view, and FIG. 11 (b) is a plan view. In addition, FIGS. 12 (a), 12 (b) and (c) explain the temperature distribution and stress distribution after laser irradiation in the D-D', cross-section E-E'and cross-section F-F'cross-sections of FIG. 11, respectively. It is a schematic diagram for doing.</p><p> In FIG. 11, an elliptical beam spot BS is formed by a laser beam emitted from a laser beam irradiation mechanism (not shown). Behind the beam spot BS, an elliptical cooling spot CS is formed by a refrigerant sprayed from a cooling mechanism (not shown). The beam spot BS and the cooling spot CS are scheduled to be separated from one end side to the other end side where the initial crack TR is formed in advance on the thin plate substrate GB while maintaining the positional relationship slightly separated from each other. Scanned along line SL.</p><p> 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 plate substrate GB in the vicinity of the region heated by the passage of the beam spot BS due to the influence of expansion due to heating. Next, tensile stress (indicated by the solid arrow in the figure) is generated in the vicinity of the region cooled by the passage of the cooling spot CS due to the effect of shrinkage due to cooling. As a result, a stress gradient is generated in the vicinity of the upper surface of the thin plate substrate GB, in which the front side (back side) is a compressive stress and the rear side (front side) is a tensile stress. In this case, regarding the stress distribution near the upper surface of the thin plate substrate GB, the temperature difference in the vertical direction of the substrate is less likely to occur due to the thin plate thickness, and as a result, cracks that tend to proceed in the surface direction are likely to be formed. Become. The reason for this will be described based on the stress generated inside the substrate.</p><p> FIG. 12 is a schematic diagram for explaining the stress and strain generated inside the thin plate substrate GB. In the thin plate substrate GB, the heating portion HR is formed inside the substrate as shown in FIG. 12A by heating by passing the laser beam irradiating the upper surface of the substrate through the beam spot BS, and the heating portion HR expands locally. As a result, compressive stress (indicated by the dashed arrow in the figure) is generated. In this case, since the thickness of the substrate is thin, the heating portion HR immediately reaches the lower surface of the substrate GB.</p><p> Next, the cooling portion CR is formed in the vicinity of the surface as shown in FIG. 12 (b) by the cooling heat generated by the passage of the cooling spot CS. In the case of a thin board GB, the cold part CR will soon reach the center of the board GB.</p><p> When the cold heat is further transferred, the cooling portion CR reaches the lower surface of the thin plate substrate GB as shown in FIG. 12 (c). As described above, in the thin plate substrate GB, since hot and cold heat is rapidly transmitted from the upper surface to the lower surface of the thin plate substrate GB, it is difficult to maintain the stress gradient due to the temperature gradient in the thickness direction of the substrate. Therefore, it is difficult to perform scribe processing on a thin plate substrate. Further, even if it is established, the process window becomes narrow and stable machining is difficult.</p><p> Therefore, in the thin plate substrate GB, the substrate is affected by the stress gradient caused by the temperature difference generated in the front-rear direction along the planned division 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. Crack will progress. That is, when the heating portion HR and the cooling portion CR exist 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 near the boundary between the heating portion HR and the cooling portion CR. It will be. As a result, cracks extending from the upper surface to the lower surface of the thin plate substrate proceed in the direction from the cooling portion CR to the heating portion HR. Therefore, the full-cut processing mode can be easily established.</p><p> When the plate thickness of the substrate is thick as described above, scribe processing is performed, but as the plate thickness of the substrate is reduced, full-cut processing is likely to occur, and scribe processing becomes difficult. Therefore, it is necessary to increase the thickness of the glass substrate in order to avoid full-cut processing during processing and to set the scribe processing mode in which a scribe line can be reliably formed. And for the processing of very thin substrates with a plate thickness of 0.4 mm or less, the division by scribe processing can be done by selecting the processing conditions from a narrow process window range or giving up as scribe processing is difficult and making a full cut. It was supposed to be divided by processing.</p><p> Therefore, the present invention is a scribing method capable of reliably scribing even a thin glass substrate having a substrate thickness in the range of 0.1 mm to 0.4 mm, which was previously considered to be impossible to scribing. The purpose is to provide. Another object of the present invention is to expand the process window of processing conditions capable of scribe processing on a thin glass substrate having the above-mentioned plate thickness.</p>

<p> When the substrate is heated by laser irradiation and then cooled, tensile stress is generated on the laser irradiation surface (upper surface of the substrate) side in the substrate at the time when cracks are formed immediately after cooling. Therefore, it was considered that the substrate after heating and cooling was deformed upward (convex toward the laser irradiation surface side). However, laser scribes were performed on a plurality of glass substrates having different plate thicknesses, the influence of the plate thickness was experimentally determined, and a two-dimensional thermoelastic analysis by the finite element method was performed based on the experimental results. 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 is recessed upward depending on the processing conditions (that is, when the time difference between heating and cooling becomes large). It was discovered that it deforms into a concave shape on the laser irradiation surface side. Then, under such processing conditions, it is considered that the progress of cracks and the progress of cracks are suppressed and cracks are not formed. Therefore, the following scribe method has been devised in the present invention.</p><p> The method for scribing a glass substrate of the present invention, which has been made to solve the above problems, is at a temperature that does not cause thermal damage to the scheduled scribing line on a thin glass substrate having a plate thickness of 0.1 mm to 0.4 mm. A thin plate glass that forms a scribe line by irradiating along the scribe line while moving the laser beam relative to heat and then cooling so that cracks that do not penetrate the substrate proceed on the scribe line. This is a substrate scribing method. Based on thermoelastic analysis by the finite element method, the substrate thickness and scanning speed processing conditions when forming a scribing line, and the stress immediately after laser heating and cooling are performed. When the scribe line is formed under the processing conditions of the plate thickness and scanning speed at which the substrate is deformed to be concave on the laser irradiation surface side by calculating the relationship with the deformation state of the substrate due to the above, a table provided with a substrate adsorption mechanism. Laser irradiation and cooling are performed with the substrate adsorbed on the substrate.</p><p> Here, the "temperature that does not cause thermal damage" means a temperature at which damage such as deformation and melting that can be visually confirmed is left due to excessive heating when the beam spot passes through. Specifically, for example, in the case of a soda glass substrate, the temperature may be lower than the experimentally determined 500 ° C (see FIG. 5), as will be 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 attracted to a table by a substrate adsorption mechanism and fixed. As a result, the stress gradient in the front-rear direction along the scheduled scribe line suppresses the force to split laterally with respect to the scheduled scribe line, and prevents the full cut state.</p><p> 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 relaxed by the deformation of the substrate, so that cracks are difficult to grow only on the surface of the substrate. The crack does not grow at all, or even if the crack grows, it becomes a full cut. However, by fixing the substrate with the substrate adsorption mechanism, cracks can develop (along with suppression of full cut) by eliminating the deflection that was recessed upwards, and as a result, it has not been possible until now. It becomes possible to establish scribe processing under the processing conditions that meet the conditions.</p>

<p> According to the present invention, even a thin plate substrate having a plate thickness of 0.1 mm to 0.4 mm can be scribed instead of full-cut, and the process window in which scribe processing can be performed can be expanded.</p>

Hereinafter, embodiments of the present invention will be described with reference to the drawings. [Device configuration] First, an apparatus configuration for carrying out the scribe method of the present invention will be described. Here, a general-purpose laser scribe device equipped with a substrate adsorption mechanism is used. FIG. 1 is a diagram showing a schematic configuration of a main part of the laser scribe device 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, and the deformed state of the substrate, which are obtained by the thermoelastic analysis by the finite element method described later.

In the present invention, the table 10 provided with the vacuum suction mechanism is used. On the upper surface of the table 10, a plate 11 formed of a porous member (for example, a porous ceramic) on which the substrate G is placed is provided. The table 10 is in close contact with the periphery of the plate 11, the bottom surface is formed, the body 12 in which the hollow space 12a is formed between the table 10 and the plate 11, and the flow path 13 connected to the hollow space 12a are formed, and the external flow path 14 is formed. A vacuum pump 16 that depressurizes the hollow space 12a via a flow path 13, an external flow path 14, and an opening control valve 16a, a flow path 13, an external flow path 14, and a pressure control valve 17a. It consists of an air source 17 that sends pressurized air to the hollow space 12a via the air source 17. 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. There is.

Above the plate 11, a screen that integrally scans a laser irradiation mechanism 21 that irradiates an elliptical beam spot on the substrate and a cooling mechanism 22 that injects a refrigerant to form an elliptical cooling spot on the substrate. The head 23 is arranged. The scribe head 23 has a scanning drive mechanism and a control unit (not shown) so that the scanning speed can be controlled between 10 mm / sec and 500 mm / sec.

[Scribe method] In the present invention, a glass substrate having a plate thickness of 0.1 mm to 0.4 mm is targeted. Until now, it has been difficult to scribe a glass substrate in this plate thickness range, and it has been necessary to select processing conditions from a narrow process window. In particular, it was thought that the thinner the substrate, the narrower the process window, and when it became as thin as 0.2 mm, scribe processing could not be performed at all. However, as shown in FIG. 2, by performing the experiment described later and the two-dimensional thermoelastic analysis by the finite element method based on the experimental result, the plate thickness and the plate thickness in which the substrate is deformed to be concave on the laser irradiation surface side and It was found that there are processing conditions for scanning speed. Therefore, in the scribing method of the present invention, the substrate is adsorbed by the substrate adsorption mechanism under the processing conditions of the plate thickness and the scanning speed that are deformed to be concave on the laser irradiation surface side, and the substrate is processed within the above processing conditions. By doing so, it is possible to prevent a full cut and to apply a force in the same direction as the tensile stress to the upper surface side of the substrate. As a result, scribe processing can be performed reliably.

[Experiment] In order to examine the effect of the plate thickness of the glass substrate on the laser scribing process, the range of processing conditions that enable laser scribing on the glass substrate with the plate thickness of 1.1 mm, 0.7 mm, 0.55 mm, and 0.4 mm was obtained by experiments. Based on the results, a two-dimensional thermoelastic analysis was performed by the finite element method.

The experimental method will be described. Fix a 300 mm x 400 mm soda glass substrate to the vacuum suction mechanism (see Fig. 1) to make it difficult to perform full-cut processing. An initial crack, which is the starting point of scribe, is provided in advance on the edge of the glass substrate with a cutter wheel. CO for laser light source₂A laser is used and the glass surface is molded so as to have an elliptical beam spot. 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. 9 (b) and 11 (b), and the dimensional relationship is as follows. Semimajor axis of beam spot YA: 22mm Beam spot short axis XA: 2.1mm Semi-major axis of cooling spot YB: 3.0mm Cooling spot short axis YA: 2.0mm Distance between the center of the beam spot and the center of the cooling spot d: 10mm

FIG. 3 shows the data (FIGS. 3 (a1) to 3 (d1)) obtained as the scanning speed v with respect to the laser output P for the processing conditions capable of laser scribe at each plate thickness h, and the crack depth with respect to the laser output P. These are the data for which Dc was obtained (Fig. 3 (a2) to Fig. 3 (d2)). When the plate thickness h is 0.4 mm, scribing is possible even at the maximum scanning speed of the device of 500 mm / sec, as shown in Fig. 3 (d1). In FIGS. 3 (a1) to 3 (d1), the x mark on the high speed side indicates the state in which the progress of cracks has stopped, and the x mark on the low speed side indicates the state in which thermal damage remains on the glass substrate. There is.

As the laser output increases at any plate thickness, the scan speed that can be scribbled tends to increase. The processing conditions (x mark on the low speed side) where thermal damage occurred are almost the same regardless of the plate thickness. The crack depth Dc for each laser output in FIGS. 3 (a2) to 3 (d2) corresponds to the low scanning speed side when the depth is deep and the high speed side when the depth is shallow.

The processing conditions (x mark on the high speed side) where crack progress is stopped when the plate thickness h is 1.1 mm have a wide range of scanning speeds that can be scribbled on the low output side of the laser, but are narrow on the high output side. Scribing is not possible when the scanning speed is 350 mm / sec or higher. On the other hand, when the plate thickness h is 0.4 mm, the range of scanning speeds that can be scribbled on the low output side is narrow, and when the laser output is 30.4 W, scribing is not possible at all scanning speeds. On the other hand, the scanning speed range in which scribing is possible on the high output side is wide, and scribing is possible even at a scanning speed of 500 mm / sec. That is, the thicker the plate thickness h, the more difficult it is to scribing on the high-speed side of the scanning speed, and the thinner the plate thickness h, the more difficult it is to scribing on the low-speed side.

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

Next, based on the machining conditions obtained in the experiment, the thermoelastic analysis by the finite element method was performed by the following method, and the influence of the plate thickness on the machining conditions of the scribe was examined. The finite element method analysis program is Quick Welder manufactured by the Computational Mechanics and Computational Center. Element division is performed with the laser irradiation surface as the xy coordinates, the y-axis as the scribe direction, and the z-axis as the plate thickness direction. For element division, the minimum division value in the beam direction (y direction) was 3.7 μm, and the minimum division value in the plate thickness direction (z direction) was 2.7 μm. The physical characteristics of the soda glass substrate are as follows. Density: 2520kg / m² Specific heat: 800J / kgK Thermal conductivity: 1.03W / mK Coefficient of thermal expansion: 8.7 × 10^-6K^-1 Young's modulus: 71.6 GPa Poisson's ratio: 0.23 Softening temperature: 720 ° C ~ 730 ° C Bending strength: 49MPa

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

In the two-dimensional heat conduction analysis of the xz plane, the center of the laser beam was scanned in the y direction from the position of y = -15 mm, 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 factor of the optical system and the reflectance of the glass. In addition, the heat transfer coefficient α in the cooling region₀Is 10⁵W / m²It was K. Then, using the obtained temperature field, σ_yy= τ_yx= τ_yzA two-dimensional thermoelastic analysis of the xz plane was performed as a plane stress problem assuming = 0. The irradiation end of the laser beam was constrained in the x direction, and the other end was constrained in the x and z directions, respectively. In the following description, the maximum temperature reached on the surface of the glass substrate during laser scribe is T._max, Σ of the glass substrate surface generated in the cooling region_xxMaximum tensile stress of σ_tmaxAnd.

Thermoelastic analysis was performed on glass substrates with plate thicknesses of 0.4 mm, 0.55 mm, 0.7 mm, and 1.1 mm under the processing conditions of output and scanning speed at which laser scribe was possible. FIG. 5 is a diagram showing the results of thermoelastic analysis. Figures 5 (a) to 5 (d) show the analysis results for the plate thicknesses of 1.1 mm, 0.7 mm, 0.55 mm, and 0.4 mm, respectively. The upper plot point group in the figure is the maximum temperature reached on the glass substrate surface T._max(Right vertical axis), the lower plot point group is the maximum tensile stress σ of the glass substrate surface._tmax(Left vertical axis). The x marks on the high-speed side of each plot point group correspond to the machining conditions in which the crack progress of the laser scribe stopped in the middle in FIGS. 3 (a1) to 3 (d1), and the x marks on the low-speed side correspond to the machining conditions. Corresponds to processing conditions that cause thermal damage.

At each plate thickness, when the laser output is constant and the scanning speed becomes low, T_maxWill increase. T for any laser output_maxThe upper limit of is almost constant (about 500 ° C) regardless of the scanning speed. Therefore, T_maxIt can be said that thermal damage does not occur in the glass below the upper limit of.

On the other hand, when the laser output is constant and the scanning speed becomes high, σ_tmaxIs decreasing. This is the reason why the crack depth becomes shallower on the high speed side in FIGS. 3 (a2) to 3 (d2). Σ for any laser output_tmaxThe lower limit of is almost constant (about 65 MPa) regardless of the scanning speed. Therefore, σ_tmaxIt can be said that the crack in the laser scribe progresses above the lower limit of. As a result, from the results of thermoelastic analysis, the processing conditions that enable laser scribe regardless of the plate thickness are the maximum surface temperature T._maxAnd the maximum tensile stress σ in the cooling region_tmaxIt can be estimated from.

Next, the influence of the plate thickness on the laser scribe will be described. Figure 6 shows the maximum tensile stress σ in the cooling region._tmaxIt is a figure which shows the temperature distribution and the deformation state of the xz plane (however, the half on one side with a scribe schedule line as one end) at the generation position. The left end of each figure corresponds to the position directly below the scheduled scribe line. Therefore, the upper left end is the laser incident position. On the opposite side of the scribe line, a temperature distribution and deformation state are formed in which these figures are mirror-symmetrical due to symmetry. The inclination in each figure indicates the magnitude of the substrate deformation and the deformation direction (convex upward or concave upward). That is, the downward-sloping figure is in an upwardly convex deformed state, and the upward-sloping figure is in an upwardly concave deformed state.

Here, for substrates with plate thicknesses 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 / sec, and (b) laser output P = 52.8. The processing conditions of W, scanning speed V = 80 mm / sec, and (c) laser output P = 71.0 W, scanning speed V = 320 mm / sec are shown.

As for the temperature distribution on the xz plane, a high temperature region remains inside the glass just below the cooling. The lower the scanning speed, the deeper the high temperature region, and the heat is transferred to the inside. Among these, especially under the processing conditions of a plate thickness of 0.4 mm, a laser output of P = 30.4 W, and a scanning speed of V = 80 mm / sec, the temperature of the back surface rises to about 200 ° C. And, unlike the others, the substrate under these processing conditions is deformed upward in a concave shape.

FIG. 7 is a diagram showing the stress distribution corresponding to FIG. Tensile stress is generated on the surface of the cooling region, and a high temperature region is formed inside the substrate just below the cooling region, forming a compressive stress field. The depth of the internal compressive stress field (depth relative to the plate thickness) when processed under the processing conditions of a plate thickness of 0.4 mm, laser output P = 30.4 W, and scanning speed V = 80 mm / sec, etc. It is deeper than the processing conditions of. This is considered to be one of the reasons why the substrate is deformed upward in a concave state.

Fig. 8 shows the maximum tensile stress σ in the cooling region under the five machining conditions shown in Fig. 4._tmaxIt is a figure which arranged and showed about the plate thickness. Σ under any processing conditions_tmaxIs convex upward, and the maximum plate thickness tends to shift to the thinner side as the scanning speed increases, and to the thicker side as the scanning speed increases. For example, under the machining conditions of laser output P = 71.0W and scanning speed v = 320mm / sec, the maximum tensile stress σ_tmaxThe maximum plate thickness approaches 0.4 mm. Maximum tensile stress σ when the plate thickness is 1.1 mm_tmaxIs smaller than the lower limit at which crack progresses, and as a result, it is considered that scribe cannot be performed. The maximum tensile stress σ under the conditions of laser output P = 30.4W and scanning speed V = 80mm / sec._tmaxThe maximum plate thickness is 1.1 mm or more. As a result, the maximum tensile stress σ with a plate thickness of 0.4 mm_tmaxIs smaller than the lower limit of crack progress, and it is considered that scribe cannot be performed.

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

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

Then, when the plate thickness of the substrate is 0.1 mm to 0.4 mm, the range of the upward concave state becomes dominant in the equation (1). As a result, as described above, in the range where the substrate is in a concave state, the substrate suction mechanism is used to bring the substrate into close contact with the table to suppress the deformation of the substrate into a concave state, so that a tensile stress is applied to the upper surface of the substrate. This makes it easier for cracks to progress and progress. Therefore, the process window for scribe processing will be expanded. In addition, in order to suppress the deformation of the substrate in the scribe schedule line, it is necessary to adsorb the vicinity of the scribe schedule line, but scribe processing can be performed by using a table having a vacuum adsorption mechanism provided with a porous member on the upper surface. I confirmed that the process window that can be used is expanded. If there are suction holes in the range of about 0.5 mm from the scheduled scribe line, a process window that can suppress deformation of the substrate and perform scribe processing will expand even on a suction table with a plate material with multiple suction holes on the upper surface. Although it was confirmed that, since it is not necessary to align the suction holes of the table with the scheduled 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 becomes convex upward, if the substrate is adsorbed by the adsorption mechanism to avoid becoming a full cut state, the substrate is adsorbed and a force in the same direction as the compressive stress is applied to the position of the scribe scheduled line. Since it becomes more difficult to scribe, it has been found that the method of using the scribe method of processing in the region where the thin plate substrate is recessed is meaningful when scribe processing the thin plate substrate.

The present invention is used when scribe processing is performed on a thin glass substrate having a plate thickness of 0.1 mm to 0.4 mm.

<figref num="1">The figure which shows the structure of the main part of the laser scribing apparatus used for carrying out the scribing method of this invention.</figref><figref num="2">The figure which shows the relationship between the plate thickness of a glass substrate, the scanning speed of a beam spot and a cooling spot, and the deformation state of a substrate obtained by thermoelastic analysis by a finite element method.</figref><figref num="3">The data (FIGS. 3 (a1) to 3 (d1)) obtained as the scanning speed v with respect to the laser output P and the crack depth Dc with respect to the laser output P were obtained as the processing conditions capable of laser scribing at each plate thickness h. The figure which shows the data (Fig. 3 (a2)-Fig. 3 (d2)).</figref><figref num="4">The figure which shows the result of arranging the crack depth Dc with respect to the plate thickness.</figref><figref num="5">The figure which shows the result of thermoelastic analysis.</figref><figref num="6">Maximum tensile stress σ in the cooling region_tmaxThe figure which shows the temperature distribution and the deformation state of the xz plane at the generation position.</figref><figref num="7">The figure which shows the stress distribution corresponding to FIG.</figref><figref num="8">Maximum tensile stress σ in the cooling region_tmaxIs organized and shown in terms of plate thickness.</figref><figref num="9">The schematic diagram for demonstrating the stress distribution which occurs in a thick plate substrate when cracks are propagated and progressed by laser irradiation and cooling.</figref><figref num="10">Schematic diagram for explaining the temperature distribution and stress distribution in the A-A'cross section, the B-B'cross section and the C-C' cross section of FIG.</figref><figref num="11">The schematic diagram for demonstrating the stress distribution which occurs in the substrate when cracks are propagated and progressed by irradiating and cooling a thin plate substrate with a laser.</figref><figref num="12">The schematic diagram for demonstrating the temperature distribution and the stress distribution in the cross section D-D', the cross section E-E', and the cross section F-F' of FIG.</figref>

Code description

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 scribe device G: Glass substrate