JP7730460B2 - Glass plate manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing glass sheets.

When manufacturing glass plates for panel displays such as liquid crystal displays and organic EL displays, large mother glass formed by a forming method such as downdraw is cut to form glass plates of the specified size.

Patent document 1 discloses a method for manufacturing glass plates that includes a recessed line forming process in which a recessed line is formed on the surface of mother glass by plastic deformation, an initial crack forming process in which an internal initial crack is formed at a position corresponding to the recessed line, a crack propagation process in which the internal initial crack is propagated within the mother glass along the recessed line, and a bending and splitting process in which the mother glass is bent and split along the recessed line.

In this manufacturing method, the recessed line formed by the recessed line forming process has a compressive stress layer formed by plastic deformation and a tensile stress layer formed closer to the interior of the mother glass than this compressive stress layer.

In the initial crack formation process, a scribe wheel is brought into contact with the surface of the mother glass and moved in a direction that intersects with the concave line. This creates a scribe line on the mother glass that intersects with the concave line. An internal initial crack is formed in the tensile stress layer, starting from this scribe line (see paragraphs 0030, 0031 and Figure 8 of the same document).

In the crack propagation process, cracks originating from these internal initial cracks are propagated in the tensile stress layer of the concave line. The subsequent bending and splitting process produces glass sheets that do not develop lateral cracks on the edge surfaces.

Japanese Patent Application Laid-Open No. 2019-89672

As mentioned above, in conventional glass plate manufacturing methods, scribe lines are formed on the mother glass using a scribing wheel to form internal initial cracks. Because the scribe lines contain numerous lateral cracks, in the bending and splitting process, the portion of the mother glass where the scribe lines are formed must be separated from the glass plate and discarded.

As such, conventional glass plate manufacturing methods required a section of the mother glass where scribe lines were to be formed, and this section had to be discarded, resulting in a decrease in glass plate yield.

The present invention was made in consideration of the above circumstances, and its technical objective is to cut mother glass without causing lateral cracks on the cut surface, while improving the yield of glass plates.

The present invention is intended to solve the above-mentioned problems, and provides a method for manufacturing a glass plate that includes a cutting step of cutting mother glass, wherein the cutting step includes a recessed line forming step of forming a recessed line on the surface of the mother glass by plastic deformation, an initial crack forming step of forming an initial crack in the recessed line, and a crack propagation step of propagating the initial crack along the recessed line within the mother glass, wherein the recessed line has a protrusion formed at the end of the recessed line in the width direction, and the protrusion includes a first base located toward the center of the recessed line in the width direction, and a second base located opposite the first base, and the initial crack forming step involves scratching at least one of the first base and the second base.

According to the above method, in the recessed line forming process, a recessed line free of lateral cracks can be formed by plastically deforming the surface of the mother glass. In the initial crack forming process, an initial crack can be formed in the protrusion by scratching at least one of the first base and second base of the protrusion.

Therefore, in the present invention, it is not necessary to form a scribe line that intersects with the recessed line using a scribing wheel, as is done in the past. In the crack propagation process, by propagating a crack starting from an initial crack along the recessed line, it is possible to produce a glass sheet that does not have lateral cracks on the edge surface (cut surface).

In this way, the present invention allows the mother glass to be cut without forming a scribe line that intersects with the recessed line, making it possible to minimize the amount of glass waste during the cutting process. This improves the yield of glass sheets.

In this method, the protrusion includes a first protrusion located at one end of the recessed line in the width direction and a second protrusion located at the other end of the recessed line in the width direction, and the initial crack formation process may involve making the scratch on the first protrusion or the second protrusion.

In the initial crack formation process, the scratch may be made in the protrusion along the width direction of the recessed line. This makes it possible to easily form an initial crack in the protrusion.

In the initial crack formation process, the scratch may be created by contacting a pointed tool with at least one of the first base portion and the second base portion. This ensures that an initial crack is formed in the protrusion.

During the initial crack formation process, the tool may be vibrated. This ensures that an initial crack is formed in the protrusion.

According to the present invention, mother glass can be cut without causing lateral cracks on the cut surface, and the yield of glass plates can be improved.

FIG. 2 is a perspective view of a scribe tip. FIG. 2 is a plan view of a scribe tip. FIG. 2 is a side view of the scribe tip. 1 is a flowchart showing a method for manufacturing a glass plate. FIG. 4 is a plan view illustrating a recessed line forming step in the manufacturing method of the glass plate. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. FIG. 2 is an enlarged cross-sectional view of a main part of the mother glass plate. FIG. 2 is a cross-sectional view showing an initial crack formation step in the method for manufacturing a glass plate. FIG. 2 is a plan view illustrating a crack propagation step in the method for manufacturing a glass plate. FIG. 2 is a cross-sectional view showing a crack propagation step in the method for manufacturing a glass plate. FIG. 2 is a perspective view showing a crack propagation step in the method for manufacturing a glass plate. FIG. 2 is a cross-sectional view showing a bending step in the manufacturing method of a glass plate. FIG. 2 is a perspective view of a manufactured glass plate. FIG. 10 is a plan view of the mother glass to be cut in the cutting step. FIG. 1 is a plan view of a mother glass cut by a conventional method. FIG. 10 is a cross-sectional view showing another example of the initial crack formation step in the method for producing a glass plate.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figures 1 to 14 show one embodiment of a method for manufacturing a glass plate according to the present invention.

Figures 1 to 3 show the scribe tip used to form recessed lines in the mother glass in this method. In this embodiment, a pencil-shaped scribe tip 1 is shown as an example, but the configuration of the scribe tip is not limited to this embodiment. The scribe tip 1 has a shank 2 and a tip 3 fixed to the end of the shank 2.

The shank 2 is made of metal and is cylindrical or polygonal. The shank 2 is attached to the holder H. The holder H holds the shank 2 and moves the scribe tip 1 vertically and horizontally. The holder H can also freely change the inclination angle of the shank 2 relative to the mother glass G.

The tip 3 is made of, for example, a single-crystal or polycrystalline diamond tip, but is not limited to this and can be made of PCBN, ceramic, cemented carbide, or other metals. The tip 3 is fixed to the tip of the shank 2 with adhesive, brazing material, or the like. The tip 3 is configured in the shape of a truncated cone, and a pressing portion 4 is formed at its end, which comes into contact with the mother glass G. In other words, the edge of the axial end face 3a of the tip 3 forms the pressing portion 4.

The pressing portion 4 is configured in an arc shape to prevent lateral cracks from occurring in the mother glass G. The pressing portion 4 presses against the surface of the mother glass G, causing plastic deformation and forming a recessed line RL in this plastically deformed portion. The radius (radius of curvature) of the pressing portion 4 is preferably 0.001 mm to 1 mm, and more preferably 0.025 mm to 0.5 mm.

This circular pressing portion 4 can be considered to be made up of multiple arcs. For example, as shown in Figure 2, the pressing portion 4 is virtually composed of three arcs 4a to 4c. In this example, the central angle θa of each of the arcs 4a to 4c is set to 120°, but this is not limited to this and it is desirable that it be between 5° and 120°. Note that while the central angle θa of each of the arcs 4a to 4c is set to be equal, it may also be configured with different angles.

As shown in Figure 3, the mother glass G used in this method has a first principal surface Ga and a second principal surface Gb, which are opposite surfaces, and an end surface Gc connecting the first principal surface Ga and the second principal surface Gb. In the present invention, at least one of the first principal surface Ga or the second principal surface Gb is referred to as the "surface" of the mother glass G. In this embodiment, the thickness t of the mother glass G is preferably 0.01 mm to 1 mm, and more preferably 0.01 mm to 0.7 mm. The mother glass G has a side length of 1000 mm or more, but is not limited to this dimension.

Mother glass G can be formed by various known forming methods, including the float method, roll-out method, slot downdraw method, and redraw method, but is preferably formed by the overflow downdraw method. In the overflow downdraw method, molten glass is poured into an overflow groove provided at the top of a forming body with a roughly wedge-shaped cross section. The molten glass that overflows on both sides of the overflow groove flows down along both side walls of the forming body, fusion-integrating at the bottom end of the forming body and continuously forming a single ribbon-shaped glass. A portion of the ribbon-shaped glass is cut widthwise to form rectangular mother glass G.

The following describes a method for manufacturing a glass plate. In this example, we will explain the production of a rectangular glass plate from a rectangular mother glass G made of alkali-free glass (OA-10G manufactured by Nippon Electric Glass Co., Ltd.).

This method includes a cutting step for cutting the mother glass G. As shown in Figure 4, the cutting step includes a recessed line forming step S1 for forming a recessed line RL by plastic deformation on the surface (e.g., the first principal surface Ga) of the mother glass G using a scribe tip 1, an initial crack forming step S2 for forming an initial crack in the recessed line RL, a crack propagation step S3 for propagating the initial crack along the recessed line RL into the mother glass G, and a bending/splitting step S4 for applying bending stress to the mother glass G.

In the recessed line forming process S1, first, the mother glass G is placed on a mounting table (not shown), and the scribe tip 1 is brought into contact with the first main surface Ga of the mother glass G. It is preferable that a resin sheet is placed on the mounting table, and the mother glass G is placed on this resin sheet. The scribe tip 1 is supported by a holder H so that the shank 2 is inclined relative to the mother glass G. When the shank 2 is inclined toward the movement direction X, the inclination angle θb (see Figure 3) is preferably 30° to 85°, but is not limited to this range.

A load is then applied to the scribe tip 1, and the first main surface Ga of the mother glass G is pressed by the pressing portion 4 of the tip 3 while the scribe tip 1 is slid along the movement direction X as shown in Figure 5. The movement speed of the scribe tip 1 is preferably 50 mm/s to 1500 mm/s. The load applied to the scribe tip 1 is 0.1 N to 10 N, but is not limited to this range and is set appropriately depending on conditions such as the size, thickness, and material of the mother glass G. The pressing portion 4 (arc 4a) is positioned in a direction perpendicular to the movement direction X (so that the tangent to arc 4a is perpendicular to the movement direction X) (see Figure 2).

A portion of the first principal surface Ga is plastically deformed by the pressure of the pressing portion 4. As shown in Figure 5, the movement of the pressing portion 4 forms a linear recessed line RL in the plastically deformed portion of the first principal surface Ga. Hereinafter, the direction perpendicular to the longitudinal direction of the recessed line RL (movement direction X) will be referred to as the width direction Y of the recessed line RL. The width dimension W1 (see Figure 6) of the recessed line RL in the width direction Y is preferably 10 μm to 50 μm. The depth of the recessed line RL is preferably 0.3 μm to 1.0 μm.

As shown in Figure 6, the concave line RL includes a compressive stress layer 5, a tensile stress layer 6, and protrusions 7a and 7b.

The compressive stress layer 5 is formed by plastically deforming the first main surface Ga of the mother glass G. The tensile stress layer 6 is formed closer to the interior of the mother glass G than the compressive stress layer 5. The tensile stress layer 6 is covered by the compressive stress layer 5.

The protrusions 7a, 7b are formed at the ends RLa, RLb of the recessed line RL in the width direction Y. The protrusions 7a, 7b protrude from the first principal surface Ga due to plastic deformation of the mother glass G. The protrusion amount (height from the first principal surface Ga) h of the protrusions 7a, 7b is preferably 0.01 μm to 0.10 μm. The protrusions 7a, 7b are formed along the entire length of the recessed line RL. The protrusions 7a, 7b include a portion 5a of the compressive stress layer 5 and a portion 6a of the tensile stress layer 6.

The protrusions 7a, 7b include a first protrusion 7a formed at one end RLa of the recessed line RL in the width direction Y, and a second protrusion 7b formed at the other end RLb of the recessed line RL in the width direction Y. Each protrusion 7a, 7b includes a first base 8a located at the center (bottom) of the recessed line RL in the width direction Y, and a second base 8b located on the opposite side of the first base 8a in the width direction Y. The width dimension W2 (the distance from the first base 8a to the second base 8b) of each protrusion 7a, 7b in the width direction Y of the recessed line RL is preferably 2 μm to 10 μm.

As shown in Figure 7, the first base portion 8a and the second base portion 8b are relaxation layers in which compressive stress is relaxed. It is presumed that slight compressive or tensile stress acts on these relaxation layers, or that the compressive and tensile stresses are substantially cancelled out. The width dimension W3 of these relaxation layers, i.e., the width dimension of the first base portion 8a and the second base portion 8b that can be scratched, is, for example, 1 μm or less.

As shown in Figure 8, in the initial crack formation step S2, the protrusions 7a and 7b are scratched with a pointed tool 9 so as to form initial cracks in the tensile stress layer 6a at the positions of the protrusions 7a and 7b. The pointed tool 9 can be, for example, a diamond tip or a carbide tool. More specifically, an electroplated diamond file or a carbide scribing tool can be used.

In this embodiment, an example is shown in which only the first protrusion portion 7a is scratched, but this is not limited to this, and it is also possible to scratch only the second protrusion portion 7b, or both the first protrusion portion 7a and the second protrusion portion 7b.

Specifically, in the initial crack formation step S2, the tip of the tool 9 is brought into contact with the first base 8a of the first protrusion 7a and then moved toward the second base 8b along the width direction Y of the recessed line RL. In this case, the tool 9 may be rotated around its axis or vibrated. From the perspective of reliably forming an initial crack, it is preferable to vibrate the tool 9. In this case, for example, the tool 9, vibrating with an amplitude of 10 μm to 15 μm and a frequency of 100 Hz to 300 Hz, may be brought into contact with the first base 8a and the second base 8b several to several hundred times.

This movement of the tool 9 causes scratches to form in the first protrusion 7a. These scratches are formed in the first base 8a and second base 8b, which are the buffer layer of the first protrusion 7a, but not in the compressive stress layer 5a between the first base 8a and second base 8b. Hereinafter, scratches formed in the first base 8a and second base 8b, which are the buffer layer of the first protrusion 7a, are referred to as initial cracks FC.

In the crack propagation process S3, a crack propagates within the tensile stress layer 6, starting from the initial crack FC. The initial crack FC in the second base portion 8b propagates along the width direction Y of the recessed line RL due to the action of residual stress in the tensile stress layer 6, crossing the first protrusion 7a and reaching the first base portion 8a, as shown by arrow A1 in Figures 9 and 10. The crack that has reached the first base portion 8a or the initial crack FC in the first base portion 8a propagates along the compressive stress layer 5a toward the center (bottom) of the width direction Y of the recessed line RL due to the action of residual stress in the tensile stress layer 6, as shown by arrow A2 in Figures 9 and 10.

When the crack reaches a position corresponding to the bottom of the concave line RL, it propagates along the longitudinal direction of the concave line RL, as shown by arrow A3 in Figures 9 and 11. In Figures 10 and 11, the crack that has reached a position corresponding to the bottom of the concave line RL is indicated by the symbol C (same in Figure 12).

In the crack propagation step S3, an external force F1 (see Figure 11) may be applied to the mother glass G to increase the propagation speed of the crack C. This external force F1 generates bending stress in the mother glass G across the concave line RL, causing the crack C to propagate faster inside the mother glass G. The external force F1 is adjusted so that the crack C does not propagate in the thickness direction of the mother glass G.

Once the crack C has finished propagating along the recessed line RL, the bending/breaking process S4 is performed. As shown in Figure 12, in the bending/breaking process S4, an external force F2 is applied to the mother glass G to propagate the crack C in the thickness direction of the mother glass G.

This external force F2 is set to be greater than the external force F1 applied to the mother glass G in the crack propagation process S3. The external force F2 generates bending stress in the mother glass G across the recessed line RL.

The crack C propagates in the thickness direction of the mother glass G due to the action of this bending stress. When the crack C reaches the first principal surface Ga and the second principal surface Gb, the mother glass G is separated. This forms a glass plate G1.

As shown in FIG. 13, glass sheet G1 has a first principal surface G1a, a second principal surface G1b located opposite the first principal surface G1a, and an end surface G1c connecting the first principal surface G1a and the second principal surface G1b. Furthermore, glass sheet G1 has a curved surface CS and a protrusion 7 (first protrusion 7a or second protrusion 7b) that are traces of the recessed line RL at the boundary B between the first principal surface G1a and the end surface G1c. Because the curved surface CS and the protrusion 7 are free of lateral cracks, glass sheet G1 has high mechanical strength even without grinding. Additionally, glass sheet G1 retains a compressive stress layer 5 formed along the curved surface CS and a tensile stress layer 6 located more inward than this compressive stress layer 5.

Below, we will explain the effect of improving yield by the manufacturing method of glass sheet G1 according to this embodiment, with reference to Figures 14 and 15. Figure 14 shows rectangular mother glass cut by the manufacturing method of glass sheet according to this embodiment. Figure 15 shows rectangular mother glass cut by forming a scribe line with a scribe wheel as in the conventional method.

In the example shown in Figures 14 and 15, the recessed line forming process S1 forms four recessed lines RL1 to RL4 on the first main surface Ga at positions inside the end faces Gc of the four sides of the mother glass G. Hereinafter, the recessed lines RL1 to RL4 will be referred to as the first recessed line RL1, the second recessed line RL2, the third recessed line RL3, and the fourth recessed line RL4, respectively. The first recessed line RL1 is parallel to the second recessed line RL2 and perpendicular to the third recessed line RL3 and the fourth recessed line RL4.

Figure 15 illustrates an example of forming an initial crack in the first recessed line RL1 and the second recessed line RL2. In this case, the scribe wheel 10 contacts the first main surface Ga at a position outside the third recessed line RL3 (toward the end surface Gc) and moves perpendicular to the first recessed line RL1 and the second recessed line RL2. The cutting depth of the scribe wheel 10 is set so that the scribe wheel 10 reaches the tensile stress layer of the recessed line RL.

By moving the scribe wheel 10, a scribe line SL is formed on the mother glass G, parallel to the third recessed line RL3. This scribe line SL contains numerous lateral cracks. For this reason, the scribe line SL must be formed at a position sufficiently far from the third recessed line RL3 to prevent cracks originating from these lateral cracks from progressing toward the third recessed line RL3. Therefore, in order to form the scribe line SL, the dimensions L11 and L21 of each side of the mother glass G necessarily become large.

In contrast, in the initial crack formation process S2 in this embodiment, the initial crack formed by the pointed tool 9 includes lateral cracks, but is formed primarily in the first base portion 8a and/or second base portion 8b, which are the relaxation layers. Therefore, in the initial crack formation process S2, it is possible to form an initial crack near the intersection P (see Figure 14) of each recessed line RL1 to RL4, which forms the corner of the glass sheet G1.

Therefore, in the manufacturing method of the glass sheet G1 according to this embodiment, when manufacturing a glass sheet G1 of the same dimensions, it is possible to reduce the dimensions L1 and L2 of each side of the mother glass G compared to conventional manufacturing methods. In other words, in the present invention, the amount of glass discarded in the cutting process can be reduced compared to conventional manufacturing methods. This allows for an improved yield of the glass sheet G1.

The present invention is not limited to the configuration of the above-described embodiment, nor is it limited to the above-described effects. Various modifications are possible to the present invention without departing from the spirit and scope of the present invention.

In the above embodiment, an example was shown in which a straight recessed line RL is formed on the mother glass G in the recessed line forming step S1, but the present invention is not limited to this form. In the recessed line forming step S1, a recessed line including a curve or a circular recessed line may also be formed on the mother glass G.

In the above embodiment, the initial crack FC is formed by moving the pointed tool 9 from the first base 8a to the second base 8b of the first protrusion 7a in the initial crack formation step S2, but the present invention is not limited to this form. As shown in FIG. 16, the initial crack formation step S2 may also involve contacting the tool 9 with two locations, the first protrusion 7a and the second protrusion 7b, to form multiple initial cracks FC. Alternatively, the initial crack FC may be formed by moving the tool 9 from the second base 8b of the protrusion 7 toward the first base 8a.

In the initial crack formation process S2, the initial crack FC may be formed only in the first base portion 8a, or only in the second base portion 8b. That is, in the initial crack formation process S2, it is sufficient to scratch at least one of the first base portion 8a and the second base portion 8b. From the perspective of improving manufacturing efficiency, it is preferable to scratch at least one of the first base portion 8a and the second base portion 8b. Note that when forming the initial crack FC only in the first base portion 8a, scratches may be formed on the first principal surface Ga around the first base portion 8a (e.g., within 50 μm of the first base portion 8a, preferably within 30 μm of the first base portion 8a, and more preferably within 20 μm of the first base portion 8a). From the perspective of preventing scratches from being formed on this first principal surface Ga, it is preferable to form the initial crack FC only in the first base portion 8a.

In the above embodiment, an example of cutting a single layer of mother glass G is shown, but this is not limited to this, and this method can also be applied when cutting a glass laminate made by stacking multiple mother glasses, or a glass resin laminate made by stacking mother glass and a resin plate.

In the initial crack formation step S2 of the above embodiment, the tip of the tool 9 is brought into contact with the first base 8a of the first protrusion 7a and then moved along the width direction Y of the recessed line RL toward the second base 8b, vibrating the tool 9 during this process. However, the tool 9 does not necessarily have to be moved or vibrated. For example, the tip of the tool 9 may be positioned above the first base 8a or second base 8b of the first protrusion 7a, and then the tool 9 may be dropped to bring the tip of the tool 9 into contact with the first base 8a or second base 8b of the first protrusion 7a, thereby forming the initial crack FC. In this case, the kinetic energy of the tip of the tool 9 when it contacts the first protrusion 7a or the like is preferably, for example, 0.013 J or greater.

7a First protrusion 7b Second protrusion 8a First base 8b Second base 9 Pointed tool FC Initial crack G Mother glass G1 Glass plate RLa End of recessed line in width direction RLb End of recessed line in width direction S1 Recessed line forming step S2 Initial crack forming step S3 Crack propagation step Y Recessed line width direction

Claims (5)

A method for manufacturing a glass plate, comprising a cutting step of cutting a mother glass,
the cutting step includes a recessed line forming step of forming a recessed line on the surface of the mother glass by plastic deformation, an initial crack forming step of forming an initial crack on the recessed line, and a crack propagation step of propagating the initial crack inside the mother glass along the recessed line,
the recessed line includes a protrusion formed at an end of the recessed line in a width direction,
the protrusion includes a first base portion located on a central side of the recessed line in the width direction, and a second base portion located on an opposite side to the first base portion,
the first base portion and the second base portion are relaxation layers in which compressive stress is relaxed,
A method for manufacturing a glass plate, characterized in that in the initial crack formation process, a pointed tool is brought into contact with at least one of the first base portion and the second base portion, thereby scratching at least one of the first base portion and the second base portion. the protrusion includes a first protrusion located at one end of the recessed line in the width direction and a second protrusion located at the other end of the recessed line in the width direction,
The method for manufacturing a glass plate according to claim 1 , wherein in the initial crack formation step, the scratch is formed on the first protrusion or the second protrusion. The method for manufacturing a glass plate according to claim 1 or 2, wherein in the initial crack formation step, the scratch along the width direction of the recessed line is formed on the protrusion. The method for manufacturing a glass plate according to claim 1 , wherein the initial crack forming step includes vibrating the tool. The method for manufacturing a glass plate according to claim 1 , wherein in the initial crack formation step, the flaw is not formed in the compressive stress layer between the first base portion and the second base portion.