JP2015205779A - Chemically strengthened glass plate, and impact testing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a chemically strengthened glass plate that hardly fractures.SOLUTION: A chemically strengthened glass plate has a surface, a rear surface, and an end face with beveled parts. In an impact test, the glass plate is arranged so that the surface and the rear surface are inclined at an angle of 20 degrees or less to a vertical surface, and is fixed to a flat plate with the rear face touching the flat plate, and an impact load of a diameter of 40 mm hits the boundary between the surface and the beveled part while the glass plate is fixed. The chemically strengthened glass plate has an average energy of 0.1 J or more when fractured.

Description

  The present invention relates to a chemically strengthened glass plate in which a compressive stress layer is formed by chemical strengthening, and an impact test method thereof.

  In recent years, in flat panel display devices such as mobile phones and personal digital assistants (PDAs), a thin plate-like cover glass has been applied to the front surface of the display so as to have a wider area than the image display portion in order to enhance display protection and aesthetics. It has been done to arrange. Such flat panel display devices are required to be lightweight and thin, and accordingly, it is also required to make cover glass used for display protection thinner. However, as the thickness of the cover glass is reduced, the strength decreases, and the cover glass itself may be broken due to falling in use or while carrying it, which plays the original role of protecting the display device. There was a problem that it was impossible.

  For this reason, the conventional cover glass formed the compressive-stress layer on the surface by chemically strengthening a glass plate, and raised the intensity | strength of the cover glass (for example, patent document 1). However, even if the cover glass is chemically strengthened, the cover glass may be damaged if the user accidentally drops the flat panel display device.

JP 2011-105598 A

  In the past, various strength test methods have been attempted in research on damage to the cover glass as described above and development of a cover glass that is resistant to breakage. Specifically, after assembling the flat panel display device, a considerable number of them can be dropped on the ground and destroyed, and the broken glass can be evaluated, or the bending strength, surface strength, etc. can be evaluated. Has been done.

  However, dropping the flat panel display device, which is the final product, on the ground not only is inefficient, but also wastes the flat panel display device itself. In addition, it has been difficult to evaluate the breakage of the cover glass actually mounted on the flat panel display device only by evaluating the bending strength and the surface strength. In addition, it has been difficult to reproduce the state of breakage of the cover glass without omission only by the conventional test method. Therefore, it has been desired to reproduce the damage when the chemically tempered glass plate is actually mounted on the flat panel display device before the flat panel display device becomes a product.

  Therefore, an object of the present invention is to provide a chemically strengthened glass plate that reproduces one situation of breakage when a cover glass is actually mounted on a flat panel display device and is not easily broken in that situation.

The chemically strengthened glass plate of one aspect of the present invention is a chemically strengthened glass plate having a front surface, a back surface, and an end surface, and having a chamfered portion on the end surface,
The front surface and the back surface are arranged so as to form an angle of 20 degrees or less with respect to the vertical surface, the plate glass is fixed while the back surface is in contact with a flat plate, and the surface glass and the chamfered portion are fixed in a state where the plate glass is fixed. In an impact test in which an impactor collides with the boundary, the average energy at the time of fracture starting from the boundary between the back surface and the chamfered portion of the chemically strengthened glass plate is 0.1 J or more.
Further, the impact test method for a chemically strengthened glass sheet according to one aspect of the present invention is an impact test method for a glass sheet having a front surface, a back surface, and an end surface, and having a chamfered portion on the end surface. It arrange | positions so that the angle of 20 degrees or less may be made with respect to a surface, and the process of fixing the said glass plate, making the said back surface contact a flat plate, and the boundary of the said surface and a chamfering part in the state which fixed the said glass plate A step of colliding the impactor; and a step of confirming the presence or absence of breakage starting from the boundary between the back surface and the chamfered portion of the glass plate after the impactor collides.

  It is possible to provide a chemically strengthened glass plate that reproduces one aspect of breakage when the cover glass is actually mounted on a flat panel display device, and is difficult to break in that situation.

It is explanatory drawing which showed typically the condition where a flat panel display apparatus falls. It is explanatory drawing which showed typically the impact test method of the chemically strengthened glass plate which concerns on embodiment of this invention. It is the graph which showed the relationship between impact fracture strength and CS about four types of samples from which the compressive stress (CS) of a glass surface differs. It is the graph which showed the relationship between impact fracture strength and CS about four types of glass plates different from the glass plate shown in FIG. It is the graph which performed CNC grinding | polishing or brush grinding | polishing about the glass plate from which thickness differs, and showed the relationship between impact fracture strength and CS. It is the schematic which shows the glass plate by one Embodiment of this invention. It is the schematic which shows the state after the etching of the glass plate by one Embodiment of this invention. It is the schematic which expanded and showed a part of state after the etching of the glass plate by one Embodiment of this invention. FIG. 9 is a partially enlarged view of FIG. 8 and is a schematic view showing a state after etching of the glass plate according to the embodiment of the present invention. It is explanatory drawing of the brush grinding | polishing method. It is explanatory drawing of the brush grinding | polishing method. It is explanatory drawing of the brush grinding | polishing method. It is explanatory drawing which expanded and showed grinding | polishing in FIG. It is sectional drawing which showed the glass plate after brush grinding | polishing with the continuous line, and showed the glass plate before brush grinding | polishing with the dashed-two dotted line.

Hereinafter, the method for reproducing cracks in the chemically strengthened glass according to the present invention will be described. First, the mechanism for breakage of the cover glass that occurs when the flat panel display device is dropped, as found by the present inventors, will be described. Here, the outer surface of the cover glass is called the front surface, and the display side surface is called the back surface.
FIG. 1 is an explanatory view schematically showing a situation where the flat panel display device 1 falls. As shown in FIG. 1, when the flat panel display device 1 falls on the ground 3 (asphalt / concrete), the boundary portion between the end surface and the surface of the cover glass 2 (hereinafter referred to as the surface end portion) is the ground first. 3 is touched. In such a case, an impact stress is generated at the end portion of the cover glass surface. When the cover glass breaks due to such a drop accompanied by impact stress, the present inventors do not use the front edge of the cover glass that first contacts the asphalt concrete 3 but the boundary between the end face and the back face of the cover glass 2. It has been found that this often occurs starting from the region (hereinafter referred to as the back end).

  A method for testing the impact strength by reproducing the impact force applied to the cover glass 2 when the flat panel display device 1 as shown in FIG. 1 falls on the ground 3 will be described below.

<Impact test method>
FIG. 2 is an explanatory view schematically showing an impact test method for a chemically strengthened glass sheet according to an embodiment of the present invention. An impact tester 300 and a chemically strengthened glass 400 as a test piece are shown. In FIG. 2, a state where the impactor 303 is in the neutral position is indicated by a solid line, and a state where the impactor 303 is lifted from the neutral position is indicated by a one-dot chain line.

  The chemically strengthened glass plate 400 includes a front surface 401 and a back surface 402 which are main planes parallel to each other, an end surface 403 which is perpendicular to the main planes 401 and 402, and each main plane 401 and 402 and the end surface 403. And chamfered surfaces 404 and 405 formed therebetween. The chemically strengthened glass plate 400 is formed symmetrically with respect to the center planes of both main planes 401 and 402, and the chamfered surfaces 404 and 405 have substantially the same size and shape.

  The impact tester 300 includes a rotating shaft 301 that is horizontally disposed, a support member 302 that extends vertically from the rotating shaft 301, and a columnar impactor 303 that is coaxially fixed to the indicating member 302. For example, the impactor 303 has a radius of 20 mm and a mass of 307 g. The impactor 303 is rotatable about the rotation shaft 301 and is rotatable to the left and right from a neutral position where the support member 302 is vertical.

  The impact tester 300 includes a jig 304 that supports the main planes 401 and 402 of the chemically strengthened glass 400 at an angle of 20 degrees or less with respect to the vertical plane. The chemically strengthened glass 400 is fixed by the jig 304 so that the back surface 402 does not float from the jig 304. Further, the glass is fixed so as not to be bent by an impact. This reproduces the situation where the back surface of the cover glass is fixed when the cover glass is incorporated into the flat panel display device. Therefore, the jig 304 is preferably larger than the chamfered surface 405 of the chemically strengthened glass 400, and the jig 304 is preferably disposed so as to extend outside the chamfered surface 405 (upward in FIG. 2). Here, the main planes 401 and 402 of the chemically strengthened glass 400 are supported by being inclined at an angle of 20 degrees or less with respect to the vertical plane, thereby reproducing the impact when the flat panel display device is dropped.

  The impact test is performed by lifting the impactor 303 from the neutral position and dropping it by gravity, as shown by a one-dot chain line in FIG. The impactor 303 rotates about the rotation axis 401 by gravity, and collides with the boundary portion (surface end portion) between the surface 401 and the chamfered portion 404 of the chemically strengthened glass 400 at the neutral position as shown by a solid line in FIG. To do. As described above, by supporting the main planes 401 and 402 of the chemically strengthened glass 400 with an inclination of 20 degrees or less with respect to the vertical plane, the impactor 303 is caused to collide with the surface end portion and the impact strength is measured. be able to.

  The impact energy applied to the chemically strengthened glass 400 at the time of collision is calculated based on the weight (16 g) of the support member 302, the weight of the impactor 303 (307 g), and the height H at which the center of gravity 305 of the impactor 303 is lifted. Is done.

  Thereafter, it is visually checked whether or not a crack has occurred at the back end of the chemically strengthened glass 400. If no crack is generated, the height H for lifting the impactor 303 is increased and the test is repeated. It is preferable to repeat the test so that the position of the chemically strengthened glass 400 is gradually shifted each time the impactor 303 is lifted and the same position is not impacted. The maximum impact energy when a crack occurs is recorded as impact fracture strength (J).

  FIG. 3 is a graph showing the relationship between impact fracture strength and CS for four types of glass plates having different glass surface compressive stresses (CS). As shown in FIG. 3, it can be seen that the impact fracture strength is improved as CS is increased. The samples shown in Table 1 below were used. In Table 1, CNC (Computer Numerical Control) refers to a method using CNC control for polishing the end face of a glass plate, and refers to CNC polishing using a grindstone.

Next, FIG. 4 is a graph showing the relationship between impact fracture strength and CS for four types of glass plates different from the glass plate shown in FIG. Here, a significant difference from the glass plate shown in FIG. 3 is that the finish of the end face of the sample is changed from CNC polishing to brush polishing.
Each sample used is shown in Table 2 below. Details of brush polishing will be described later.

  As shown in FIG. 4, it can be seen that the impact fracture strength can be significantly improved by carrying out brush polishing. It is considered that the impact fracture strength is improved by making the end surface finish by brush polishing because fine scratches as starting points of cracks existing on the end surface can be removed as compared with CNC polishing.

  Next, FIG. 5 is a graph showing the relationship between impact fracture strength and CS after CNC polishing or brush polishing is performed on glass plates having different thicknesses. As shown in FIG. 5, it can be seen that the thickness of the glass plate as well as the CS and end face finishes are factors that change the impact fracture strength as factors for increasing the impact fracture strength. In addition, the thickness of the glass plate in this case points out the thickness of the end surface of glass. Therefore, the thickness may be increased over the entire glass plate, or only the thickness of the end face may be increased.

  In addition, it is preferable practically that the impact fracture strength at the back end is 0.1 J or more. In order to satisfy the impact fracture strength, parameters such as CS, presence / absence of brush polishing, and plate thickness can be appropriately combined. However, from the viewpoint of bending strength, CS is preferably 500 MPa or more. The thickness of the glass plate is preferably 0.6 mm or more, more preferably 0.7 mm or more, and still more preferably 1.0 mm or more.

  Here, the chemically strengthened glass subjected to brush polishing will be described. FIG. 6 is a schematic view showing a glass plate according to an embodiment of the present invention. The glass plate 10 has front and back main surfaces 11 and 12 and end surfaces 13 adjacent to the two main surfaces 11 and 12. The two main surfaces 11 and 12 are flat surfaces parallel to each other.

  The end surface 13 includes a flat portion 14 perpendicular to the two main surfaces 11 and 12 and chamfered portions 15 and 16 formed between the main surfaces 11 and 12 and the flat portion 14. The flat part 14 may be a cut surface obtained by cutting a plate glass having a larger area than the glass plate 10 or may be a processed surface obtained by processing the cut surface.

  For example, four chamfered portions 15, 16 may be provided corresponding to four sides of the rectangular main surfaces 11, 12, or only one may be provided, and the number of chamfered portions 15, 16 is not particularly limited. In order to suitably reduce the breakage, it is preferably provided on all sides.

  The chamfered portions 15 and 16 are formed by removing the corners of the cut surface or the processed surface and the main surface. The chamfered portions 15 and 16 are, for example, flat surfaces or curved surfaces oblique to the main surfaces 11 and 12. In FIG. 6, the chamfered portions 15 and 16 have the same dimensional shape, but may have different dimensional shapes.

  The chamfered portions 15 and 16 of the present embodiment are flat surfaces that are inclined with respect to the main surfaces 11 and 12, but the outer surfaces of the chamfered portions 15 and 16 extend from the main surfaces 11 and 12 to the flat portion 14 in the thickness direction view (X direction view). Any surface may be used as long as the surface gradually protrudes in the direction, or a curved surface. In this case, the chamfered portions 15 and 16 may be connected to each other without the flat portion 14, and the chamfered portions 15 and 16 may have substantially the same radius of curvature.

  The glass plate 10 has chemical strengthening layers (compressive stress layers) 21 and 22 formed on both main surfaces 11 and 12 at a predetermined depth from the main surfaces 11 and 12. The compressive stress layer is formed by immersing glass in a treatment liquid for ion exchange. A small ionic radius ion (eg, Li ion, Na ion) contained in the glass surface is replaced with a large ionic radius ion (eg, K ion), and a compressive stress layer is formed on the glass surface at a predetermined depth from the surface. Is done. Due to the stress balance, a tensile stress layer is formed inside the glass.

  The two compressive stress layers 21 and 22 of the present embodiment have the same surface compressive stress and the same thickness, but may have different surface compressive stresses and different thicknesses. FIG. 7 is a schematic view showing a state after etching of a glass plate according to an embodiment of the present invention. In FIG. 7, the state after the etching of the glass plate 10 is indicated by a solid line, and the state before the etching of the glass plate 10 is indicated by a two-dot chain line. FIG. 8 is a partially enlarged view of FIG. 7 and shows the relationship between the etching surface 17, the pits 18 formed on the etching surface 17, and the ideal surface 19 of the etching surface 17.

  In this embodiment, when the predetermined portions 13a and 13b of the end face 13 are etched, pits 18 having a depth of 1 μm or more (preferably a depth of 0.8 μm or more, more preferably a depth of 0.6 μm or more) are formed on the etching surface 17. Absent. The predetermined portions 13a and 13b have a distance H in the plate thickness direction from the main planes 11 and 12 adjacent to the chamfered portions 15 and 16 of the side surface 13 within 1/5 of the plate thickness E (H ≦ 1/5 × E). ) Part.

  “Etching” is performed at room temperature (25 ° C.) by immersing the entire glass plate 10 in an etching solution. As an etchant, an aqueous solution containing 5% by mass hydrofluoric acid (HF) and 95% by mass pure water is used. The etching solution penetrates into the latent scratch formed on the surface or inside of the glass plate 10 and spreads the latent scratch to clarify it.

  The “etching amount” is controlled by the immersion time. Specifically, after performing etching for a predetermined time using glass having the same composition in advance to calculate an etching rate, etching is performed by adjusting the immersion time so that a desired etching amount is obtained. Depending on the type of glass, the hydrofluoric acid concentration may be changed to adjust the etching rate.

  The “pit depth” is obtained based on the measurement method of the protruding valley depth Rvk defined in JIS B0671-2: 2002.

  Here, the target for examining the presence or absence of the pits 18 having a depth of 1 μm or more is limited to the portions 13a and 13b of the side surface 13 when the minute scratches are present in the portions 13a and 13b. This is because the glass plate 10 may be damaged.

In the present embodiment, the pits 18 on the surface of the etching surface 17 when the portions 13a and 13b are etched by, for example, a depth of 10 μm are measured. Etching is performed to clarify latent scratches, and the depth is not limited to 10 μm.
In addition, the latent scratches in the portions 13a and 13b were measured regardless of the presence or absence of etching, and the depth of the latent scratches was measured.

  Here, the “latent scratch depth” was measured by the following process. First, after the glass plate 10 is etched, the main plane of the glass substrate is polished by a predetermined amount, washed and dried, and the work-affected layer that has become circular pits or elliptic pits by etching is observed with an optical microscope. Here, the “work-affected layer” refers to a layer in which scratches, cracks, and the like generated in a glass substrate are present in processing steps such as shape imparting, chamfering, and grinding. For example, the objective lens of an optical microscope used 20 times, and it observed with the observation visual field of 635 micrometers x 480 micrometers. This process was repeated a plurality of times, and the etching amount of the glass plate 10 when the circular pits or the elliptical pits were no longer observed was defined as “latent scratch depth”.

  In the glass plate 10 of the present embodiment, the effect of the compressive stress layer can be obtained even if there are latent scratches in the chamfered portion by chemically strengthening the DOL so that the latent scratch depth is 0.9 or less. It is preferable because it can be obtained. As a more preferred embodiment, the latent scar depth is 0.7 or less, more preferably 0.5 or less with respect to DOL. Although it is preferable to measure DOL in a chamfering part here, you may measure DOL inside 10 mm from the boundary area | region of a chamfering part and a main surface. A similar effect can be obtained if the DOL of the region is 0.9 or less with respect to the latent scratch depth of the chamfered portion. As a more detailed evaluation, in the center of each of the four sides of the glass plate, the DOL inside 10 mm from the boundary region between the chamfered portion and the main surface and the latent scratch depth of the chamfered portion are 0.9 or less, respectively. It doesn't matter.

  Next, the brush polishing method will be described. 9-11 is explanatory drawing of the brush grinding | polishing method. FIG. 9 shows a laminated body 130 including a glass plate 110 that is a base plate (original), and a brush 140 that polishes an outer edge portion of the laminated body 130. FIG. 10 is an enlarged view showing a state in which the outer edge portion of the laminated body 130 is polished with the brush 140. FIG. 11 shows the glass plate 110A after brush polishing by a solid line, and shows the glass plate 110 before brush polishing by a two-dot chain line.

  In the glass plate brush polishing method of the present embodiment, a spacer 120 is interposed between the glass plates 110 and a laminate step for producing the laminate 130 and a polishing step for polishing the outer edge portion of the laminate 130 with the brush 140. And have. The glass plate manufacturing method further includes a separation step of separating the glass plate 110 </ b> A obtained by polishing the glass plate 110 with the brush 140 and the spacer 120.

  As shown in FIG. 9, the laminated body 130 includes a plurality of glass plates 110 and plate-like spacers 120 interposed between the glass plates 110. The glass plates 110 and the spacers 120 are alternately stacked and then fixed by being sandwiched by a jig such as a clamp. A protective sheet for preventing damage to the glass plate 110 may be disposed between the glass plate 110 and the spacer 120. The protective sheet is made of resin or the like.

  In addition, although the glass plate 110 and the spacer 120 of this embodiment were fixed with a jig | tool, the fixing method is not specifically limited. For example, the fixing method may be a method of bonding the glass plate 110 and the spacer 120. As the adhesive, one that can be removed in the separation step after the polishing step is used, and for example, a heat-softening resin is used. Instead of forming an adhesive layer between the glass plate 110 and the spacer 120, the spacer 120 itself may be used as the adhesive layer.

  Each glass plate 110 may be cut | disconnected and multiple pieces may be cut | disconnected, for example after chemically strengthening the plate glass of a larger area than the glass plate 110. FIG. About the kind of plate glass, the chemical strengthening method, and the cutting method, since it is the same as said content, description is abbreviate | omitted.

  As shown in FIG. 10, each glass plate 110 has two main planes 111 and 112 and a side surface 113 adjacent to the two main planes 111 and 112. The two main planes 111 and 112 are flat surfaces parallel to each other. The side surface 113 is a cut surface and is a flat surface perpendicular to the main planes 111 and 112.

  Each glass plate 110 has a compressive stress layer formed at a predetermined depth from each main plane 111, 112 on both main planes 111, 112, similarly to the glass plate 10 shown in FIG. A tensile stress layer is formed between the compressive stress layers for balance of stress. Moreover, each glass plate 110 has the area | region where the tensile stress by chemical strengthening remains in the side surface 113 similarly to the glass plate 10 shown in FIG.

  As shown in FIG. 10, each glass plate 110 has substantially the same size and shape and is laminated so that the outer edges overlap each other when viewed in the lamination direction (in the direction of arrow X in the figure). Therefore, the outer edge portion of each glass plate 110 is evenly polished.

  Each spacer 120 is made of a softer material than a glass plate, and is made of, for example, polypropylene resin or urethane foam resin.

  Each spacer 120 has substantially the same size and shape. Each spacer 120 is disposed on the inner side of the outer edge of the glass plate 110 when viewed in the stacking direction (viewed in the direction of arrow X in the figure), and forms a groove-like gap 160 between the glass plates 110.

  The brush 140 is a roll brush as shown in FIG. 9, and includes a rotation shaft 141 parallel to the stacking direction of the stacked body 130, brush hairs 142 held substantially perpendicular to the rotation shaft 141, and the like. The brush 140 is relatively moved along the outer edge of the laminated body 130 while being rotated around the rotation shaft 141, and discharges slurry containing an abrasive toward the outer edge of the laminated body 130. Brush the outer edge. As the abrasive, cerium oxide, zirconia, or the like is used. The particle size (D50) of the abrasive is, for example, 5 μm or less, preferably 2 μm or less.

  The brush 140 is a channel brush, and is formed by spirally winding a long member (channel) in which a plurality of brush hairs 142 are planted around a rotation shaft 141.

The brush bristles 142 are mainly composed of a resin such as polyamide, and may include an abrasive such as alumina (Al ₂ O ₃ ), silicon carbide (SiC), or diamond. The brush hair 142 may be formed in a linear shape and have a tapered tip portion.

  In the present embodiment, the width W1 of the gap 160 is 1.25 times or more the maximum diameter A of the bristle 142 (W1 ≧ 1.25 × A). Therefore, as shown in FIG. 5, the brush hairs 142 are smoothly inserted into the gap 160, and the corners between the main planes 111 and 112 and the side surfaces 113 of the glass plate 110 are chamfered to a curved surface by the brush hairs 142.

  The width W1 of the gap 160 is preferably 1.33 × A or more, and more preferably 1.5 × A or more. The width W1 of the gap 160 may be smaller than the plate thickness E of the glass plate 110 in order to improve brush polishing efficiency.

  The glass plate 110A polished by the brush 140 has two main planes 111A and 112A and side surfaces 113A adjacent to the two main planes 111A and 112A, as indicated by solid lines in FIG. The two main planes 111A and 112A are flat surfaces parallel to each other. The side surface 113A includes a flat portion 114A perpendicular to the main planes 111A and 112A, and chamfered portions 115A and 116A formed between the main planes 111A and 112A and the flat portion 114A. The chamfered portions 115A and 116A are curved surfaces that gradually protrude outward from the main planes 111A and 112A to the flat portion 114A in the thickness direction view (X direction view).

  The flat portion 114A is formed by polishing the side surface of the glass plate 110 indicated by a two-dot chain line in FIG. The chamfered portions 115 </ b> A and 116 </ b> A are formed by polishing the corner portion between the main plane and the side surface of the glass plate 110 indicated by a two-dot chain line in FIG.

  The side surface 113A of the glass plate 110A is polished with a slurry containing an abrasive having a particle size of 5 μm or less by inserting brush bristles 142 into the gap adjusted by the spacer 120. When etching is performed with a thickness of 10 μm, there is no pit having a depth of 1 μm or more on the etched surface. The predetermined portion is a portion of the side surface 113A whose distance in the plate thickness direction from the main planes 111A and 112A adjacent to the chamfered portions 115A and 116A is within 1/5 of the plate thickness.

  Moreover, you may further have the process of grinding the outer edge part of a glass plate, before forming the laminated body for brush grinding | polishing so that it may describe below. 12-14 is explanatory drawing of the manufacturing method of the glass plate by the 3rd Embodiment of this invention. FIG. 12 shows a glass plate 110 which is a base plate (original) and a rotating grindstone 240 for grinding an outer edge portion of the glass plate 110. FIG. 13 shows an enlarged view of the state in which the outer edge portion of the laminated body 130B including the glass plate 110B ground by the rotating grindstone 240 is polished by the brush 140 (see FIG. 10). FIG. 14 shows the glass plate 110C after brush polishing by a solid line, and the glass plate 110B before brush polishing by a two-dot chain line.

  The manufacturing method of a glass plate interposes the spacer 120 between the grinding process which grinds the outer edge part of the glass plate 110 with the disk shaped rotary grindstone 240, and the glass plates 110B obtained by grinding the glass plate 110, It has the lamination process which produces laminated body 130B, and the grinding | polishing process which grind | polishes the outer edge part of laminated body 130B with the brush 140. FIG. The glass plate manufacturing method further includes a separation step of separating the glass plate 110 </ b> C obtained by polishing the glass plate 110 </ b> B with the brush 140 and the spacer 120.

  An annular grinding groove 242 extending in the circumferential direction is formed on the outer peripheral surface 241 of the rotating grindstone 240. The wall surface of the grinding groove 242 includes abrasive grains such as alumina, silicon carbide, and diamond. The grain size (JIS R6001) of the abrasive grains is, for example, # 300 to # 2000. The particle size is measured based on JIS R6002. The smaller the particle size, the larger the particle size and the better the grinding efficiency.

  The rotating grindstone 240 is relatively moved along the outer edge of the glass plate 110 while being rotated about the center line of the rotating grindstone 240, and the outer edge portion of the glass plate 110 is ground by the wall surface of the grinding groove 242. A coolant such as water may be used during grinding.

  As shown in FIG. 13, the glass plate 110B ground with the rotating grindstone 240 has two main planes 111B and 112B and side surfaces 113B adjacent to the two main planes 111B and 112B. The side surface 113B is a ground surface ground by the rotating grindstone 240, and is a flat portion 114B perpendicular to the main planes 111B and 112B, and a chamfer formed between the main planes 111B and 112B and the flat portion 114B. Part 115B, 116B. The chamfered portions 115B and 116B are flat surfaces that are inclined with respect to the main planes 111B and 112B, for example.

  The chamfered portions 115B and 116B of the present embodiment are flat surfaces that are inclined with respect to the main planes 111B and 112B. However, the chamfered portions 115B and 116B are outside from the main planes 111B and 112B to the flat portions 114B when viewed in the plate thickness direction (viewed in the X direction). Any surface may be used as long as the surface gradually protrudes in the direction, or a curved surface. In this case, the chamfered portions 115B and 116B may be connected to each other without the flat portion 114B, and the chamfered portions 115B and 116B may have substantially the same radius of curvature.

  The laminated body 130B includes a plurality of glass plates 110B ground by the rotating grindstone 240 and a plate-like spacer 120 interposed between the glass plates 110B. The glass plates 110 </ b> B and the spacers 120 are alternately stacked and then fixed by being sandwiched by a jig such as a clamp. A protective sheet for preventing damage to the glass plate 110 </ b> B may be disposed between the glass plate 110 </ b> B and the spacer 120. The protective sheet is made of resin or the like. Note that another fixing method may be used as a method of fixing the glass plate 110 </ b> B and the spacer 120.

  Each glass plate 110B ground by the rotating grindstone 240 has substantially the same size and shape, and is laminated so that the outer edges overlap each other when viewed in the laminating direction (the arrow X direction in the figure). Therefore, the outer edge portion of each glass plate 110B is evenly polished. A cooling liquid such as water may be used during polishing.

  Each spacer 120 has substantially the same size and shape, and is disposed on the inner side of the grinding surface (flat portion 114B and chamfered portions 115B and 116B) of each glass plate 110B in the stacking direction view (viewed in the direction of arrow X in the drawing). The gap 160B is formed between the glass plates 110B.

  In this embodiment, the width W2 of the gap 160B is not less than 1.25 times the maximum diameter A of the bristle 142 (W2 ≧ 1.25 × A). Therefore, as shown in FIG. 13, the brush bristle 142 is smoothly inserted into the gap 160 </ b> B, and the boundary between the main planes 111 </ b> B and 112 </ b> B of the glass plate 110 </ b> B and the chamfered parts 115 </ b> B and 116 </ b> B is chamfered into a curved surface by the brush bristle 142. The At this time, the boundary portion between the chamfered portions 115 </ b> B and 116 </ b> B and the flat portion 114 </ b> B is also chamfered to a curved surface by the brush hair 142.

  The width W2 of the gap 160B is preferably 1.33 × A or more, more preferably 1.5 × A or more. The width W2 of the gap 160B may be smaller than the plate thickness E of the glass plate 110B in order to improve the efficiency of brush polishing.

  The glass plate 110C polished with the brush 140 has two main planes 111C and 112C and side surfaces 113C adjacent to the two main planes 111C and 112C, as indicated by solid lines in FIG. The two main planes 111C and 112C are flat surfaces parallel to each other. The side surface 113C includes a flat portion 114C perpendicular to the main planes 111C and 112C, and chamfered portions 115C and 116C formed between the main planes 111C and 112C and the flat portion 114C. The chamfered portions 115C and 116C are surfaces that gradually protrude outward from the main planes 111C and 112C to the flat portion 114C in the thickness direction view (X direction view).

  Since the side surface 113C of the glass plate 110C is polished with a slurry containing an abrasive having a particle size of 5 μm or less by inserting brush hairs into the gap adjusted by the spacer 120, a predetermined portion of the side surface 113C is etched. There is no pit with a depth of 1 μm or more on the etched surface. The predetermined portion is a portion of the side surface 113C whose distance in the plate thickness direction from the main planes 111C and 112C adjacent to the chamfered portions 115C and 116C is within 1/5 of the plate thickness. Therefore, the glass plate 110C excellent in bending strength similar to the first embodiment is obtained.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions are made to the above-described embodiments without departing from the scope of the present invention. be able to.

  For example, although the grinding groove is formed on the outer peripheral surface of the rotary grindstone of the embodiment, it may not be formed. When there is no grinding groove, the side surface of the glass plate ground on the outer peripheral surface of the rotating grindstone is a surface perpendicular to the main plane. Therefore, when there is no grinding groove, a glass plate having substantially the same shape as that of the base plate 110 indicated by a two-dot chain line in FIG. 11 is obtained by grinding, and then substantially the same shape as that of the glass plate 110A indicated by the solid line in FIG. A glass plate is obtained.

  Moreover, you may grind | polish the corner | angular part of a glass plate with a sheet | seat instead of grinding with the rotating grindstone with a grinding groove. Further, instead of grinding with a rotating grindstone with a grinding groove, after grinding with a rotating grindstone without a grinding groove, the corners of the ground glass plate may be polished with a sheet.

The method of chemical strengthening treatment for obtaining the tempered glass sheet of the present invention is not particularly limited as long as it can ion-exchange Na in the glass surface layer and K in the molten salt, but for example, heated potassium nitrate molten salt The method of immersing glass is mentioned. Incidentally, potassium nitrate molten salt, or potassium nitrate salts in the present invention other KNO _3, including those containing KNO ₃ and 10 wt% or less of NaNO _3.
The chemical strengthening treatment conditions for forming a chemically strengthened layer (compressive stress layer) having a desired surface compressive stress on the glass vary depending on the thickness of the glass plate, but it is 2 to 350 to 550 ° C. potassium nitrate molten salt. It is typical to immerse the glass substrate for ~ 20 hours. From an economical viewpoint, it is preferable to immerse on the conditions of 350-500 degreeC and 2 to 16 hours, and a more preferable immersion time is 2 to 10 hours.

  Although the glass plate of the present invention has a substantially rectangular shape, the corner may have a curved shape when viewed from the front, or the side portion may have a protrusion or a depression outward or inward in the surface direction.

  Although there is no particular limitation on the method for producing the glass plate in the present invention, for example, appropriate amounts of various raw materials are prepared, heated to about 1400 to 1800 ° C. and melted, and then homogenized by defoaming, stirring, etc. It is manufactured by forming into a plate shape by a downdraw method, a press method, etc., and then cooling to a desired size after slow cooling.

It is preferable that the glass transition point Tg of the glass of the glass plate of this invention is 400 degreeC or more. If it is less than 400 ° C., the surface compressive stress is relaxed during ion exchange, and there is a possibility that sufficient stress cannot be obtained. More preferably, it is 550 degreeC or more.
The temperature T2 at which the viscosity of the glass of the glass plate of the present invention is 10 ² dPa · s is preferably 1800 ° C. or lower, more preferably 1750 ° C. or lower.
The temperature T4 at which the viscosity of the glass of the present invention is 10 ⁴ dPa · s is preferably 1350 ° C. or lower.

The specific gravity ρ of the glass of the glass plate of the present invention is preferably 2.37 to 2.55.
It is preferable that the Young's modulus E of the glass of the glass plate of this invention is 65 GPa or more. If it is less than 68 GPa, the rigidity and breaking strength of the glass cover glass may be insufficient.
The Poisson's ratio σ of the glass of the glass plate of the present invention is preferably 0.25 or less. If it exceeds 0.25, the crack resistance of the glass may be insufficient.

Next, unless otherwise indicated, the glass composition of the glass plate of the present invention will be described using the mole percentage display content.
SiO ₂ is a component that constitutes the skeleton of glass and is essential, and reduces the occurrence of cracks when scratches (indentations) are made on the glass surface, or the fracture rate when indentations are made after chemical strengthening. It is a component to make small. If the SiO ₂ content is less than 56%, the stability, weather resistance or chipping resistance of the glass is lowered. SiO ₂ is preferably 58% or more, more preferably 60% or more. If SiO ₂ exceeds 75%, the viscosity of the glass increases and the meltability decreases.

Al ₂ O ₃ is an effective component for improving ion exchange performance and chipping resistance, is a component that increases the surface compressive stress, or a component that reduces the crack generation rate when indented with a 110 ° indenter. And essential. If Al ₂ O ₃ is less than 5%, a desired surface compressive stress value or compressive stress layer thickness cannot be obtained by ion exchange. Preferably it is 9% or more. If Al ₂ O ₃ exceeds 20%, the viscosity of the glass becomes high and uniform melting becomes difficult. Al ₂ O ₃ is preferably 15% or less, typically 14% or less.

The total SiO ₂ + Al ₂ O ₃ content of SiO ₂ and Al ₂ O ₃ is preferably 80% or less. If it exceeds 80%, the viscosity of the glass at high temperature may increase and melting may be difficult, and it is preferably 79% or less, more preferably 78% or less. _Further, it is preferable that SiO 2 + _Al 2 _{O 3} is 70% or more. If it is less than 70%, the crack resistance when an indentation is made decreases, more preferably 72% or more.

Na ₂ O is a component that forms a surface compressive stress layer by ion exchange and improves the meltability of the glass, and is essential. If Na ₂ O is less than 8%, it becomes difficult to form a desired surface compressive stress layer by ion exchange, and it is preferably 10% or more, more preferably 11% or more. If Na ₂ O exceeds 22%, the weather resistance is lowered, or cracks are likely to occur from the indentation. Preferably it is 21% or less.

K ₂ O is not essential, but may be contained in a range of 10% or less in order to increase the ion exchange rate. If it exceeds 10%, cracks are likely to occur from the indentation, or the change in surface compressive stress due to the concentration of NaNO ₃ in the molten potassium nitrate salt may increase. K ₂ O is 5% or less, more preferably 0.8% or less, still more preferably 0.5% or less, and typically 0.3% or less. When it is desired to reduce the change in the surface compressive stress due to the NaNO ₃ concentration in the potassium nitrate molten salt, it is preferable not to contain K ₂ O.

MgO is a component that increases the surface compressive stress and is a component that improves the meltability and is essential. When it is desired to suppress stress relaxation, it is preferable to contain MgO. When MgO is not contained, the degree of stress relaxation tends to change depending on the location of the chemical strengthening treatment tank due to variations in the molten salt temperature when performing chemical strengthening treatment, and as a result, a stable compressive stress value can be obtained. May be difficult. On the other hand, if MgO exceeds 14%, the glass tends to be devitrified, or the change in surface compressive stress due to the concentration of NaNO ₃ in the potassium nitrate molten salt may increase, and it is preferably 13% or less.

The SiO ₂ —MgO is preferably 64% or less, more preferably 62% or less, and typically 61% or less.
The Al ₂ O ₃ —MgO is preferably 9% or less, more preferably 8% or less.

The total content of SiO ₂ , Al ₂ O ₃ , Na ₂ O and MgO is preferably 98% or more. If the total is less than 98%, it may be difficult to obtain a desired compressive stress layer while maintaining crack resistance. Typically, it is 98.3% or more.

ZrO ₂ is not essential, but may be contained in a range of up to 5% in order to reduce the viscosity at high temperature or increase the surface compressive stress. If ZrO ₂ exceeds 5%, there is a risk that the possibility of cracking from the indentation increases. Therefore, it is preferably 2% or less, more preferably 1% or less, and typically does not contain ZrO ₂ .

B ₂ O ₃ is not essential, but may be contained in a range of 6% or less in order to improve the melting property at high temperature or the glass strength. If B ₂ O ₃ exceeds 6%, it is difficult to obtain a homogeneous glass, which may make it difficult to mold the glass, or may reduce crack resistance. Typically no B ₂ O ₃ is contained.
The total content of SiO ₂ , Al ₂ O ₃ , Na ₂ O and MgO is preferably 98% or more.

  Although the preferable glass component of the glass plate of this invention consists of the component demonstrated above essentially, you may contain another component in the range which does not impair the objective of this invention. When such components are contained, the total content of these components is preferably less than 2%, more preferably 1% or less. Hereinafter, the other components will be described as an example.

ZnO may be contained up to 2%, for example, in order to improve the melting property of the glass at a high temperature, but is preferably 1% or less, and 0.5% or less in the case of manufacturing by a float process. It is preferable to make it. If ZnO exceeds 0.5%, it may be reduced during float molding, resulting in a product defect. Typically no ZnO is contained.
Since TiO ₂ coexists with Fe ions present in the glass, the visible light transmittance is lowered and the glass may be colored brown, so even if it is contained, it is preferably 1% or less. Does not contain.

Li ₂ O is a component that lowers the strain point to facilitate stress relaxation, and as a result makes it impossible to obtain a stable surface compressive stress layer, so it is preferably not contained, and even if it is contained, its content Is preferably less than 1%, more preferably 0.05% or less, and particularly preferably less than 0.01%.

In addition, Li ₂ O may be eluted in a molten salt such as KNO ₃ during chemical strengthening treatment, but when the chemical strengthening treatment is performed using a molten salt containing Li, the surface compressive stress is remarkably reduced. Li ₂ O is preferably not contained from this viewpoint.

CaO may be contained in a range of 5% or less in order to improve the meltability at high temperature or to prevent devitrification. If the CaO content exceeds 5%, the ion exchange rate or the resistance to cracking decreases. Typically no CaO is contained.
SrO may be contained as necessary, but since the effect of lowering the ion exchange rate is greater than that of MgO and CaO, the content is preferably less than 1% even when contained. Typically no SrO is contained.
Since BaO has the greatest effect of reducing the ion exchange rate among alkaline earth metal oxides, BaO should not be contained, or even if contained, its content should be less than 1%. preferable.

When SrO or BaO is contained, the total content thereof is preferably 1% or less, more preferably less than 0.3%.
When one or more of CaO, SrO, BaO and ZrO ₂ are contained, the total content of these four components is preferably less than 1.5%. If the total is 1.5% or more, the ion exchange rate may be lowered, and is typically 1% or less.

As a fining agent for melting the glass, SO ₃ , chloride, fluoride and the like may be appropriately contained. However, in order to increase the visibility of a display device such as a touch panel, it is preferable to reduce as much as possible the components that are mixed as impurities in the raw material, such as Fe ₂ O ₃ , NiO, and Cr ₂ O ₃ that absorb in the visible region, The percentage is preferably 0.15% or less, and more preferably 0.05% or less.

<Example>
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

As examples, a plurality of glass plates having different plate thicknesses (0.6 mm, 1.0 mm, 1.1 mm) were prepared, and chemical strengthening treatment was performed on each glass plate. The chemically strengthened sample was prepared by brush polishing the end face and by CNC polishing, and the impact strength was measured. The results are shown in Table 3 below. In Table 3, each numerical value represents an average value, and the CNC polishing was performed using a # 600 grindstone.
In Examples 1 to 6 and 8, end face finishing is performed by brush polishing, and all have high impact strength of 0.1 J or higher. On the other hand, in each of Comparative Examples 1 to 6, end face finishing was performed by CNC polishing, and in all cases, the impact strength was a value smaller than 0.1 J.
Example 7 had a high CS of 1000 MPa or more, and had a high impact strength of 0.1 J or more without brushing the end face.

  From the above examples, the impact strength depends on the end face finish, CS, and plate thickness, respectively, and a glass plate having an impact strength of 0.1 J or more can be prepared by adjusting them.

  It can be used as a cover glass for display devices. Moreover, it can utilize also for a solar cell board | substrate, an aircraft window glass, etc.

DESCRIPTION OF SYMBOLS 10 Glass plate 11, 12 Main surface 13 End surface 13a, 13b Predetermined part 15, 16 Chamfer 17 Etching surface 18 Pit 21, 22 Chemical strengthening layer (compressive stress layer)
23 Tensile stress layer

Claims (6)

A chemically strengthened glass plate having a front surface, a back surface and an end surface, and having a chamfered portion on the end surface,
The front surface and the back surface are arranged so as to form an angle of 20 degrees or less with respect to the vertical surface, the plate glass is fixed while the back surface is in contact with a flat plate, and the surface glass and the chamfered portion are fixed in a state where the plate glass is fixed. In the impact test in which an impactor having a diameter of 40 mm collides with the boundary, the chemically strengthened glass plate has an average energy of 0.1 J or more when the chemically strengthened glass plate is broken.   2. The pit having a depth of 1 μm or more does not exist on the etched surface when etching is performed in a portion where the distance in the thickness direction from the main surface adjacent to the chamfered portion is within 1/5 of the thickness. The chemically strengthened glass plate described in 1.   The chemically strengthened glass sheet according to claim 1 or 2, wherein the thickness of the end surface of the sheet glass is 0.6 mm or more.   The chemically strengthened glass plate according to any one of claims 1 to 3, wherein the plate glass has a compressive stress layer on a surface thereof, and the compressive stress of the compressive stress layer is 500 MPa or more. A glass plate impact test method having a front surface, a back surface, and an end surface, and having a chamfered portion on the end surface,
Placing the front and back surfaces at an angle of 20 degrees or less with respect to a vertical surface, and fixing the glass plate while contacting the back surface with a flat plate;
A step of causing an impactor to collide with a boundary between the surface and the chamfered portion in a state where the glass plate is fixed;
An impact test method for a chemically strengthened glass sheet, comprising the step of confirming the presence or absence of breakage starting from the boundary between the back surface and the chamfered portion of the glass sheet after the impactor collides.   The impactor is connected to a rotating shaft extending in a horizontal direction via a support member. The impact test method for a chemically strengthened glass sheet according to claim 5, wherein the impact test is performed.

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