JP2015017016A - Strengthened glass plate, and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a strengthened glass plate having improved quality of an end surface and an improved lasting strength by polishing the end surface of the strengthened glass plate made of strengthened glass, and a manufacturing method of the same.SOLUTION: A manufacturing method of a strengthened glass plate includes a cutting step for cutting a glass sheet having a strengthened layer formed on the surface by ion exchange to manufacture a strengthened glass plate having a main surface and an end surface, and a step for polishing the end surface with loose abrasive particles. In the polishing step, a boundary polished surface is formed at the boundary between the main surface and the end surface and the strengthened layer on the boundary polished surface remains when polished.

Description

  The present invention relates to a tempered glass sheet and a method for producing the same.

  The glass plate is manufactured by cutting a sheet glass into a predetermined size with a cutting device. When cutting the sheet glass, a scribe line is formed on the sheet glass, and tensile stress is concentrated on the scribe line to cleave the sheet glass. The scribe line is generally formed by a method of mechanically forming using a diamond cutter or a method of causing an initial crack to proceed by heating and rapid cooling using a laser.

  When the scribe line is formed mechanically, fine cracks inevitably exist around the scribe line. When a scribe line is formed using a laser, a very sharp edge is formed at the corner between the end surface and the front and back surfaces of the divided glass plate. In the chamfering machine, these edges have a C-side shape for grinding the end portion of the short-side end surface of the rectangular glass plate using a diamond wheel for grinding, and a convex shape with a curved cross-sectional shape of the end surface. Grinded into an arc or R shape.

  The arithmetic average roughness Ra of the end face of the glass plate is ground to be, for example, about 0.1 μm to 0.2 μm. However, a layer containing microcracks called microcracks or hair cracks is formed on the end face of the ground glass plate. This layer is called a work-affected layer or a fragile fracture layer, and causes a reduction in fracture strength at the end face of the glass plate. It is known that the breaking strength at the end face of the glass plate is improved by removing such a layer and polishing the end face of the glass plate. In addition to improving the strength, the end surface of the glass plate is mirror-finished so that the end surface can be exposed, and the degree of freedom in designing a display device or the like can be increased.

However, in the case of a tempered glass plate made of tempered glass, the strength may not be improved even if the end surface is polished to remove a layer in which micro cracks are formed and the end surface is made a mirror surface.
Therefore, the present invention provides a tempered glass plate that polishes the end face of a tempered glass plate made of tempered glass, improves the end face quality, and maintains and improves the strength, and a method for producing the same.

  The present inventor, when the strength does not improve after performing the mirror finish on the end face after chamfering of the tempered glass plate made of tempered glass, the tempered layer of the surface of the main surface of the tempered glass plate in the region in contact with the end face Found that the problem is lost.

Therefore, the manufacturing method of the tempered glass plate of the present invention includes a cutting step of manufacturing a tempered glass plate having a main surface and an end face by cutting a glass sheet having a tempered layer formed by ion exchange on the surface. And polishing the main surface and the end surface using free abrasive grains,
In the polishing step, polishing is performed such that a boundary polishing surface is formed at a boundary portion between the main surface and the end surface, and a reinforcing layer of the boundary polishing surface remains.
The boundary polishing surface is a region where free abrasive grains are in contact with the main surface of the glass sheet and polished, and is 500 μm or more, preferably 1000 μm, more preferably in a direction perpendicular to the longitudinal direction of the end surface in the glass sheet surface. It preferably has a length of 1500 μm or more.

In the polishing step, the thickness of the boundary polishing surface after the polishing step is in the range of 0.3 to less than 1, more preferably 0.5 to less than 1 of the thickness of the main surface reinforcing layer. It is preferable to polish as described above.
It is preferable to further include a grinding step for grinding the end face between the cutting step and the polishing step.
Moreover, it is preferable to grind | polish the said grinding | polishing process so that the average roughness Ra of the said end surface may be less than 0.01 micrometer.
Furthermore, it is preferable to etch the end face after the polishing step.

The tempered glass plate of the present invention is a tempered glass plate having a tempered layer reinforced and formed on the surface by ion exchange, and has a boundary polished surface at the boundary between the main surface and the end surface. The reinforcing layer on the surface is thicker than the reinforcing layer on the boundary polished surface. Here, the boundary polishing surface is the same as described above.
The roughness Ra of the end face and the roughness Ra of the boundary polishing surface are preferably less than 0.01 μm.
Further, the thickness of the reinforcing layer remaining on the boundary polished surface is preferably in the range of 0.3 to less than 1, more preferably 0.5 to less than 1, the thickness of the reinforcing layer on the main surface.

  The display device of the present invention is assembled by exposing the end face of any of the above-described tempered glass plates.

  ADVANTAGE OF THE INVENTION According to this invention, while grind | polishing the end surface of the tempered glass board made from tempered glass, while improving end surface quality, the intensity | strength is also maintained and improved, and its manufacturing method can be provided.

It is a flowchart of the manufacturing method of the glass plate which concerns on this embodiment. It is a schematic diagram which shows the manufacturing apparatus 1 of the glass plate used with the manufacturing method of the glass plate which concerns on this embodiment. It is a figure which shows typically the cross section of the tempered glass board PG after grinding of an end surface. It is a figure which shows typically the cross section of the tempered glass board PG after grinding | polishing of an end surface. It is a top view which shows the outline of the grinding | polishing apparatus 10 which concerns on this embodiment. It is a fragmentary sectional view which follows the VI-VI line of FIG.

  Hereinafter, the manufacturing method of the tempered glass board of one embodiment of the present invention is explained, referring to drawings.

(1) Manufacturing method of tempered glass board In the manufacturing method of the tempered glass board concerning this embodiment, a glass board is manufactured using a down draw method. First, with reference to FIG. 1 and FIG. 2, the manufacturing apparatus 1 of the tempered glass board used for the several process included in the manufacturing method of a tempered glass board and a several process is demonstrated. As shown in FIG. 1, the manufacturing method of a tempered glass plate is mainly a melting step S1, a refining step S2, a forming step S3, a cooling step S4, a base plate cutting step S5, a strengthening treatment step S6, a cutting step S7, and a grinding step. S8 and polishing step S9.

The melting step S1 is a step in which the glass raw material is melted. After the glass raw material is prepared so as to have a desired composition, as shown in FIG. 2, the glass raw material is put into a melting apparatus 2 arranged upstream. Glass raw materials, for example, made of _{SiO 2, Al 2 O 3,} Na 2 O, K 2 O, LiO 2, MgO, B 2 O 3, CaO, SrO, the composition of BaO or the like. Specifically, a glass material having a strain point of 500 ° C. or higher and a devitrification temperature −Tg (glass transition point) of 400 ° C. or lower is used. The glass raw material is melted by the melting device 2 to become molten glass. The melting temperature is adjusted according to the type of glass. In this embodiment, the glass material is melted at 1600 ° C. or lower. The molten glass is sent to the refining device 4 through the upstream pipe 3.

  The clarification step S2 is a step of removing bubbles in the molten glass. The molten glass from which bubbles have been removed in the refining device 4 is then sent to the forming device 6 through the downstream pipe 5.

  The forming step S3 is a step of forming the molten glass into a sheet-like glass (sheet glass). In this embodiment, an overflow downdraw method is used.

  The cooling step S4 is a step of cooling (slow cooling) the sheet glass. The sheet glass is cooled to a temperature close to room temperature through the cooling step S4. In addition, according to the cooling state in cooling process S4, the thickness (plate thickness) of a glass plate, the curvature amount of a glass plate, and the distortion amount of a glass plate are determined.

  The base plate cutting step S5 is a step of manufacturing the glass sheet by cutting the sheet glass into a predetermined size by the cutting device 8. When cutting the sheet glass, a scribe line is formed on the sheet glass, and tensile stress is concentrated on the scribe line to cleave the sheet glass. The scribe line is generally formed by a method of mechanically forming using a diamond cutter or a method of causing an initial crack to proceed by heating and rapid cooling using a laser.

The strengthening treatment step S6 is a step of performing ion exchange treatment on the surface of the glass sheet formed as described above. In the tempering step S6, a glass sheet having a reinforced layer (ion exchange region) that is reinforced and formed on the surface by ion exchange is formed. In the chemical strengthening treatment, the glass sheet is immersed in a treatment bath of 100% KNO ₃ maintained at, for example, about 350 to 550 ° C. for about 1 to 25 hours. At this time, the glass sheet is chemically strengthened by ion exchange of Na ⁺ ions or Li ⁺ ions on the surface of the glass sheet with K ⁺ ions or Li ⁺ ions in the treatment bath. Note that the temperature, time, ion exchange solution, and the like during the ion exchange treatment can be changed as appropriate. For example, the ion exchange solution may be a mixed solution of two or more types. In the reinforcing treatment step S6, a reinforcing layer having a certain thickness A is formed on the surface of the glass sheet. The constant thickness may have a width. When a certain thickness has a width, A is an average value.

  The cutting step S7 is a step of manufacturing a tempered glass plate PG having a main surface and an end face by cutting the glass sheet having the tempered layer into a predetermined size with a not-shown cutting device. Here, the main surface refers to the surface of the sheet glass where the reinforced layer having a certain thickness A exists, and the end surface refers to the reinforced layer having a thickness A less than [the above thickness A × 0.3]. The surface of the sheet glass of the part to do. The thickness of the end face reinforcing layer may be 0 (zero).

  In the cutting step S7, a scribe line is formed on the glass sheet having the reinforcing layer, and the tensile stress is concentrated on the scribe line to cleave. The scribe line is generally formed by a method of mechanically forming using a diamond cutter or a method of causing an initial crack to progress by heating and rapid cooling using a laser. An edge is formed in the vicinity of the end face of the cleaved tempered glass plate PG.

  The grinding step S8 is a step of grinding an edge near the end face of the tempered glass plate PG. When the scribe line is mechanically formed in the cutting step S7, fine cracks inevitably exist around the scribe line. In addition, when a scribe line is formed using a laser, a very sharp edge is formed at the corner (boundary portion) between the end surface of the divided tempered glass plate PG and the front and back surfaces (main surface). Is done.

  For these edges, a chamfering machine (not shown) uses a metal bond wheel having diamond abrasive grains for grinding on the short side end surface of the rectangular glass plate PG, and the end surface has a curved sectional shape. Grinding into a shape, arc shape or R shape (first grinding step). The tempered glass sheet PG after grinding has, for example, a main surface 32, an end face 34, and a reinforced layer 40 as shown in FIG.

  The arithmetic average roughness Ra of the end surface 34 of the tempered glass plate PG is ground so as to be about 0.1 μm to 0.2 μm, for example. However, a layer containing micro cracks called micro cracks or hair cracks is formed on the end face 34 of the ground glass plate PG. This layer is called a work-affected layer or a fragile fracture layer, and exists in a thickness of about 10 μm to 30 μm, for example.

  Subsequently, it is preferable to remove the work-affected layer generated by the metal bond wheel (second grinding step) with a grinding wheel using a binder having lower hardness and rigidity than the binder of the metal bond wheel. Specifically, secondary grinding is performed using a resin bond wheel and a resin bond wheel in which diamond abrasive grains are dispersed. On the end surface 34 of the glass plate PG subjected to the secondary grinding, a work-affected layer or a fragile fracture layer that is thinner than a work-affected layer or a fragile fracture layer formed by a metal bond wheel remains. The presence of such a layer reduces the breaking strength at the end face 34 of the tempered glass sheet PG. In order to remove such a layer and improve the breaking strength at the end face 34 of the tempered glass plate PG, a polishing step S9 is performed.

The work-affected layer remaining after the second grinding step is performed to be less than 10 μm.
The work-affected layer remaining after the second grinding step is preferably ground to be less than 5 μm, more preferably 1 to 3 μm.
The second grinding process is not limited to the resin bond wheel. Grinding with a metal bond wheel having finer diamond abrasive grains than in the first grinding step may be used.

(1-1) Polishing The polishing step S9 is a step of polishing an end portion composed of the end surface 34 of the ground tempered glass plate PG and the main surface 32 near the end surface in a polishing apparatus using loose abrasive grains. . In conventional grinding / polishing using fixed abrasive grains, it is difficult to reduce and remove microcracks generated in the boundary region (boundary portion) between the main surface and the end surface. On the other hand, according to the present invention, it is possible to polish the loose abrasive grains from the main surface to the end face with a reduced load on the glass, so that microcracks in the boundary region can be reduced and removed. Thereby, the fall of the bending strength resulting from a microcrack can be suppressed.

  In FIG. 4, the cross section of the tempered glass board PG after grinding | polishing of the end surface 34 is shown typically. In the polishing step S9, the boundary portion between the main surface 32 and the end surface 34 is 500 μm or more, preferably 1000 μm or more, more preferably 1500 μm in the direction perpendicular to the longitudinal direction of the end surface in the surface of the tempered glass plate PG (glass sheet). The boundary polishing surface 36 having the above length is formed, and polishing is performed so that the reinforcing layer 40 of the boundary polishing surface 36 remains. In the polishing step S9, the thickness of the reinforcing layer 40 on the boundary polishing surface 36 after polishing is preferably 0.3 or more and less than 1 of the thickness A of the reinforcing layer 40 on the main surface 32, more preferably 0.5 or more and less than 1. Polish to be in the range.

The fact that the reinforcing layer remains means that the ion exchange region remains. The fact that the ion exchange region remains means that a substituted ion such as potassium that has been substituted is detected by EPMA (electron beam microanalyzer method) or EDS analysis (energy dispersive X-ray spectroscopy).
In the present invention, the ion exchange region remains by means of an EDS analyzer (VE-7800 manufactured by Keyence Corporation) with a substitution ion concentration of 30 wt% on the boundary polishing surface 36 with respect to a substitution ion concentration on the surface 32 (= main surface). % Or more is detected.

  Further, the first ion exchange region 30 that is an ion exchanged region on the main surface 32 is thicker than the second ion exchange region 38 that is an ion exchanged region on the boundary polishing surface 36. In the present invention, the thickness (depth from the surface) of the first ion exchange region 30 is considered as the thickness of the reinforcing layer 40 on the main surface 32. Further, the thickness (depth from the surface) of the second ion exchange region 38 is considered as the thickness of the reinforcing layer 40 on the boundary polishing surface 36. The thickness of the reinforcing layer 40 remaining on the boundary polishing surface 36 is preferably in the range of 0.3 to less than 1, more preferably 0.5 to less than 1, the thickness of the reinforcing layer 40 on the main surface 32.

  In the polishing step S9, the work-affected layer or the brittle fracture layer of the end surface 34 of the tempered glass plate PG is removed, and the arithmetic average roughness Ra of the end surface 34 of the tempered glass plate PG is strengthened so as to be less than 0.01 μm, for example. The end surface of the glass plate PG is polished. It is preferable to polish so that the arithmetic average roughness Ra of the boundary polishing surface 36 is the same. In the present invention, the ion-exchanged reinforcing layer remains in the region (boundary polished surface) on the end surface side of the main surface, and the end surface and the boundary polished surface are finished to Ra less than 0.01 μm. The bending strength of the plate can be maintained and improved.

  FIG. 5 is a plan view showing an outline of the polishing process using the polishing apparatus 10 of the present embodiment. 6 is a partial cross-sectional view taken along line VI-VI in FIG. The polishing apparatus 10 includes a pair of magnetic field forming units 12 and free abrasive grains 20 held in a space formed therebetween as a polishing wheel. The magnetic field forming unit 12 is composed of, for example, a magnet such as a permanent magnet or an electromagnet, and is provided so as to form a magnetic field having a desired strength between the pair of magnetic field forming units.

  The rotation shaft 18 is connected to a rotation drive unit (not shown) and is provided to rotate around a shaft at a desired rotation speed. Moreover, the rotating shaft 18 is provided so that it may approach and leave | separate with respect to the tempered glass board PG with the moving mechanism not shown. The magnetic field forming unit 12 is fixed to the rotating shaft 18 and rotates together with the rotating shaft 18. As a result, the loose abrasive grains 20 are continuously rotated around the rotation shaft 18. At this time, as shown in FIG. 6, the end portion of the tempered glass plate PG bites into the loose abrasive grains 20, and the end portion of the tempered glass plate PG rotates while being in contact with the loose abrasive grains 20. Grain 20 and the edge part of tempered glass board PG move relatively. Thereby, the edge part of the tempered glass board PG is grind | polished by the loose abrasive 20 restrained by the magnetic field which the magnetic field formation part 12 forms.

  The length of the boundary polishing surface 36 after polishing, the thickness of the reinforced layer 40 on the boundary polishing surface 36, and the length of the boundary polishing surface are determined by the depth of biting into the free abrasive grains 20 at the end of the tempered glass plate PG, and polishing. It can be adjusted by adjusting time etc. In addition, in order to prevent that the said penetration depth is not enough and the boundary part of an end surface and a surface is not grind | polished, a fixed penetration depth is required exceeding a boundary part.

  As the loose abrasive 20, a magnetic material polishing slurry containing magnetic powder is used. The magnetic material polishing slurry is composed of a magnetic powder and a liquid. The magnetic powder functions as abrasive grains and is composed of magnetic particles such as iron oxide and ferrite. As liquid mixed with magnetic powder, for example, water, hydrocarbons, esters, ethers, hydrogen fluoride, or water as the main component, adding hydrocarbons, esters, ethers, hydrogen fluoride, etc. Liquid or the like can be used. Further, a surfactant such as a fatty acid ester may be added at 0.5 wt% or less. Moreover, in order to relieve the composition change, propylene glycol having a boiling point higher than that of water may be added at less than 3%. From the viewpoint of suppressing an increase in the temperature of the magnetic polishing slurry during polishing, water is preferable as the liquid.

  In the present embodiment, the magnetic powder and water are mixed so that the concentration of the magnetic powder in the magnetic material polishing slurry is preferably 70 wt% or more. The concentration of the magnetic powder is preferably 80 wt% or more, and more preferably 85 wt% or more, from the viewpoint of glass removal ability.

  In the present embodiment, the end face 34 is polished without moving the polishing apparatus 10 in the conveying direction of the tempered glass plate PG. However, the polishing apparatus is stopped while the tempered glass plate PG is stopped or the tempered glass plate PG is conveyed. 10 may be moved to polish the end face 34 of the tempered glass plate PG.

  After the polishing step S9, the polished end face 34 may be further etched with fluoric acid (HF) or the like. The average strength can be improved by smoothing the scratches remaining on the weakly strengthened and non-strengthened end faces with fluoric acid or the like. The concentration of fluoric acid is preferably 100 ppm or more, more preferably 1000 ppm to 3000 ppm.

(2) Display device The display device of the present invention is assembled by exposing the end face of the tempered glass plate. For this reason, it is possible to polish the end face of the tempered glass plate made of tempered glass to improve the end face quality and to maintain and improve the strength.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

Example 1
For a tempered glass plate having a CS (compressive stress value) of 600 MPa or more and a DOL (ion exchange layer depth) of 20 μm or more, grinding is performed using a metal bond wheel having diamond abrasive grains. The Ra of the end face and the boundary polishing face was polished to less than 0.01 μm. At that time, polishing was performed so that the ion-exchange layer remained on the boundary polished surface. The boundary polished surface was ground and polished so that the K concentration was 30% or more.
The average strength in the four-point bending test when 20 sheets were tested was 454 MPa of 450 MPa or more.

Example 2
For the tempered glass plate similar to that of Example 1, the first grinding using a metal bond wheel having diamond abrasive grains and the second grinding using a resin bond wheel are performed, and further by polishing the magnetic abrasive grains, The Ra of the boundary polished surface was polished to less than 0.01 μm. At that time, polishing was performed so that the ion-exchange layer remained on the boundary polished surface. The boundary polished surface was ground and polished so that the K concentration was 30% or more.
The polished tempered glass plate was etched at room temperature under the conditions of HF 4.6 wt% concentration and 30 sec.
The average strength in a 4-point bending test when 20 sheets were tested was 798 MPa, which is 750 MPa or more.

Example 3
For the same tempered glass plate as in Examples 1 and 2, the first grinding using a metal bond wheel having diamond abrasive grains, the second grinding using a resin bond wheel, and further by magnetic abrasive grain polishing, The Ra of the end face and the boundary polishing face was polished to less than 0.01 μm. At that time, polishing was performed so that the ion-exchange layer remained on the boundary polished surface. The boundary polished surface was ground and polished so that the K concentration was 30% or more.
The polished tempered glass plate was etched at room temperature under the conditions of HF 4.6 wt% concentration and 30 sec.
The average strength in the four-point bending test when 20 sheets were tested was 814 MPa of 800 MPa or more.

Comparative Example A tempered glass plate similar to that of Example 1 was used as glass having a cut end surface by mechanical scribe + folding. First grinding using a metal bond wheel having diamond abrasive grains, second grinding using a resin bond wheel, and further polishing using a polishing wheel using a polyurethane binder having flexibility and elasticity as a polishing step Went.
In the four-point bending test when 20 sheets were tested, the average strength was 350 MPa.

(3) Modification (3-1) Modification 1
Using a tempered glass plate of CS: 400 MPa and DOL: 8-12 μm, end face treatment by grinding / polishing and HF etching was performed in the same manner as in Example 3 to evaluate the change in bending strength before and after the treatment. By reducing the thickness of the work-affected layer after the second grinding step to less than 3 μm, the time required for polishing the magnetic abrasive grains until the roughness Ra of the end surface was less than 0.01 μm was shortened. Thereby, even if it was a tempered glass board with a thinner tempering layer than an Example, the average intensity | strength was able to be improved like an Example.

  In the said Example, although the resin bond wheel was used as a 2nd grinding process, you may use a metal bond wheel. For example, the work-affected layer generated in the first grinding step may be reduced or removed using a wheel having finer abrasive grains than in the first grinding step. Furthermore, a third grinding step with finer abrasive grains may be performed.

(3-2) Modification 2
The first ground using a metal bond wheel having diamond abrasive grains is performed on the same tempered glass plate as in Example 1, and then a metal having abrasive grains smaller than the abrasive grains used in the first grinding step. The second grinding process was performed using a bond wheel, and the Ra of the end face and the boundary polishing surface was polished to less than 0.01 μm by magnetic abrasive polishing. Similar to the examples, the average strength could be improved.

  According to the present invention, polishing can be performed in a state where the load applied to the glass is reduced from the main surface to the end surface by the free abrasive grains, so that microcracks in the boundary region can be reduced and removed. Thereby, the fall of the bending strength resulting from a microcrack can be suppressed.

DESCRIPTION OF SYMBOLS 1 Glass plate manufacturing apparatus 2 Melting apparatus 4 Refining apparatus 6 Molding apparatus 8 Cutting apparatus 10 Polishing apparatus 12 Magnetic field forming part 18 Rotating shaft 20 Free abrasive grain PG Tempered glass sheet

International Publication No. 2012/066757 JP 2001-259978 A

Claims (9)

Cutting a glass sheet having a reinforced layer formed by ion exchange on the surface, and manufacturing a tempered glass plate having a main surface and an end surface; and
Polishing the main surface and the end surface using loose abrasive grains;
Have
In the polishing step, polishing is performed so that a boundary polishing surface is formed at a boundary portion between the main surface and the end surface, and a reinforcing layer of the boundary polishing surface remains.
The manufacturing method of the tempered glass board characterized by the above-mentioned. The boundary polishing surface has a length of at least 500 μm or more in a direction perpendicular to the longitudinal direction of the end surface in the glass sheet surface.
The manufacturing method of the tempered glass board of Claim 1. A grinding step of grinding the end face between the cutting step and the polishing step;
The manufacturing method of the tempered glass board of Claim 1 or 2. The polishing step is performed so that the average roughness Ra of the end surface is less than 0.01 μm.
The manufacturing method of the tempered glass board of any one of Claim 1 to 3. After the polishing step, the end surface is etched.
The manufacturing method of the tempered glass board of any one of Claim 1 to 4. A tempered glass plate having a reinforced layer formed by ion exchange on the surface,
The main surface has a boundary polished surface at the boundary with the end surface,
A tempered glass sheet, wherein the reinforced layer on the main surface is thicker than the reinforced layer on the boundary polished surface. The boundary polishing surface has a length of at least 500 μm or more in a direction perpendicular to the longitudinal direction of the end surface in the glass sheet surface.
The tempered glass sheet according to claim 6. The tempered glass sheet according to claim 6 or 7, wherein the roughness Ra of the end face and the roughness Ra of the boundary polished surface are less than 0.01 µm.   The display apparatus assembled by exposing the end surface of the tempered glass board of any one of Claim 6 to 8.