JP2015157733A - Method for producing chemically strengthened glass plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently producing a chemically strengthened glass plate having reduced warpage.SOLUTION: There is provided a method for producing a chemically strengthened glass plate having principal front and rear surfaces and an end surface for connecting the principal front and rear surfaces, which comprises, after performing chemical strengthening, a step of polishing the principal front and rear surfaces using a polishing pad having Shore A hardness of 70 or more and 95 or less.

Description

  The present invention relates to a method for producing a chemically strengthened glass sheet.

  In a mobile phone such as a smartphone or a portable device such as a PDA, a cover glass is used to protect the display. In recent years, technology for reducing the thickness and weight of portable devices has been demanded, and cover glass has been reduced in weight and thickness.

  Such a cover glass is manufactured by cutting a glass base plate into a predetermined shape and chemically strengthening, and then polishing the main plane (see, for example, Patent Document 1).

  In addition, there is a demand for more efficient production of chemically strengthened glass as the market expands.

JP 2012-218995 A

  When the main plane of the glass plate is polished, the glass plate may be warped due to a difference in polishing rate between the upper surface and the lower surface. In a general method for producing a glass plate, the main plane is polished before chemical strengthening, so that the warpage of the glass plate generated by polishing before strengthening may be further increased by polishing after strengthening. Come out.

  In order to place the glass plate in the polishing process after strengthening so as to reduce the warp generated by polishing before strengthening, a process of checking the warpage state of the glass plate must be performed each time, It will certainly reduce the production throughput.

  The method for producing a chemically strengthened glass sheet according to one aspect of the present invention is a method for producing a chemically strengthened glass sheet having a main surface on the front and back sides and an end surface connecting between the main surfaces of the front and back surfaces. The method includes a step of polishing the front and back main surfaces using a polishing pad having a Shore A hardness of 70 to 95.

  Moreover, the manufacturing method of the chemically strengthened glass plate of another aspect of the present invention includes a step of preparing a glass plate having front and back main surfaces and an end surface connecting the main surfaces of the front and back surfaces, and the front and back surfaces of the glass plate. It comprises a step of polishing a main surface, a step of chemically strengthening the polished glass plate to form a chemically tempered glass plate, and a step of polishing main surfaces of the front and back surfaces of the chemically tempered glass plate. A method for producing a chemically strengthened glass plate.

  According to the manufacturing method of the glass plate which concerns on 1 aspect of this invention, the chemically strengthened glass plate which reduced curvature can be manufactured efficiently.

It is sectional drawing which showed typically the cross section in the manufacturing process of a chemically strengthened glass plate. It is sectional drawing which showed typically the cross section in the manufacturing process of a chemically strengthened glass plate. It is sectional drawing which showed typically the cross section in the manufacturing process of a chemically strengthened glass plate. It is sectional drawing which showed typically the cross section in the manufacturing process of the chemically strengthened glass plate which concerns on one Embodiment of this invention. It is sectional drawing which showed typically the cross section in the manufacturing process of the chemically strengthened glass plate which concerns on one Embodiment of this invention.

  Hereinafter, an embodiment of a method for producing a chemically strengthened glass sheet of the present invention will be described with reference to the drawings. 1 to 3 are cross-sectional views schematically showing a cross-section in the manufacturing process of the chemically strengthened glass plate.

  As shown in FIG. 1, a glass plate 20 is placed between polishing pads 10 provided in a double-side polishing apparatus (not shown) to perform polishing. The polishing pad 10 is a soft polishing pad, and the hardness laminated to a thickness of 4.5 mm is a Shore A hardness of 45 or more and less than 70. If it is less than 45, it may be difficult to obtain a sufficient polishing rate. The polishing pad material satisfying such conditions typically includes unemployed fabric pads, woven fabric pads, suede pads, and the like, of which suede pads are the most preferred.

  The polishing pad 10 is thinner than a hard urethane pad (typically 1.5 mm to 2.0 mm), and typically has a thickness of about 0.3 mm to 0.9 mm. Also, the groove depth formed on the pad surface is shallower than that of the hard urethane pad (typically 1.2 mm to 1.7 mm), typically 0.2 mm to 0.8 mm. Have a thickness of about.

The composition of the glass plate 20 is not particularly limited, but is preferably easy to chemically strengthen. As a preferable composition of the glass plate 20, for example, in terms of mol% based on oxide, SiO ₂ : 50 to 80%, Al ₂ O ₃ : 2 to 25%, Li ₂ O: 0 to 10%, Na ₂ O _{: 0~18%, K 2 O:} 0~10%, MgO: 0~15%, CaO: 0~5% and _ZrO 2: a glass containing 0 to 5%.

Besides, by mol% based on _{oxides, SiO 2: 50~74%, Al} 2 O 3: 1~10%, Na 2 O: 6~14%, K 2 O: 3~11%, MgO : 2~15%, CaO: 0~6% and _ZrO 2: comprises 0-5%, the total content of SiO ₂ and _Al 2 _{O 3} is 75% or less, the content of Na ₂ O and _{K 2} O total from 12 to 25% of glass total content of MgO and CaO is _{7~15%, SiO 2: 68~80%} , Al 2 O 3: 4~10%, Na 2 O: 5~15 %, K ₂ O: 0 to 1%, MgO: 4 to 15% and ZrO ₂ : Glass containing 0 to 1%, SiO ₂ : 67 to 75%, Al ₂ O ₃ : 0 to 4%, Na ₂ O _{: 7~15%, K 2 O:} 1~9%, MgO: 6~14% and _ZrO 2: comprises 0 to 1.5%, SiO ₂ and l ₂ total content of O ₃ is 71-75%, the sum is 12 to 20% content of Na ₂ O and _{K 2} O, when containing CaO, the content is less than 1% It is preferable to use glass.

  The glass plate 20 before chemical strengthening is produced by a method such as a float method, a fusion downdraw method, a slit downdraw method, or a redraw method, and is chemically strengthened using a known chemical strengthening treatment.

  The polishing liquid (polishing slurry) includes, for example, rare earth oxides such as colloidal silica and cerium oxide, zirconium oxide, aluminum oxide, magnesium oxide, silicon oxide, silicon carbide, manganese oxide, iron oxide, diamond, boron nitride and zircon. A slurry containing known abrasive grains is used. Abrasive grains may be used alone or in combination of two or more.

  The size, shape, and thickness of the glass plate 20 vary depending on the application and can be selected as appropriate. However, the thinner the chemically strengthened glass, the higher the effect because the influence of warpage increases as the thickness decreases. Specifically, the warp can be more effectively reduced when the thickness of the glass plate 20 is 0.7 mm or less, and preferably 0.6 mm or less.

  Actually, as shown in FIG. 2, the glass plate 20 is warped by a polishing process before chemical strengthening or the like. FIG. 2 shows a case where the warped glass plate 20 is convex (convex upward) toward the polishing pad 10 for upper surface polishing. In order to polish so as to reduce the warp of the glass plate 20, it is necessary to polish more convex portions of the glass plate 20 than the concave side, but the lower surface side of the glass plate 20 is also affected by the weight of the glass plate 20 and the like. It is more polished and warpage is worsened.

  On the other hand, as shown in FIG. 3, if the warped glass plate 20 is convex toward the polishing pad 10 for lower surface polishing (convex downward), more convex portions of the glass plate 20 can be polished. I can do it.

  As described above, depending on the direction in which the glass plate 20 is placed, there are the glass plate 20 whose warpage deteriorates and the glass plate 20 which improves. By performing the step of confirming the warpage of the glass plate 20 before the polishing step after chemical strengthening, it becomes possible to polish in a direction in which the warpage of all the glass plates 20 can be improved. It is not realistic to perform the process of checking the warpage state for each sheet.

  FIG.4 and FIG.5 is sectional drawing which showed typically the cross section in the manufacturing process of the chemically strengthened glass plate which concerns on one Embodiment of this invention.

  As shown in FIG. 4, a glass plate 40 is placed between polishing pads 30 provided in a double-side polishing apparatus (not shown) to perform polishing. The polishing pad 30 is a soft polishing pad, and the hardness laminated to a thickness of 4.5 mm is 70 to 95 in Shore A hardness. If it exceeds 95, there is a risk of minute scratches on the glass due to the pressing of the abrasive grains. The polishing pad material satisfying such conditions typically includes unemployed fabric pads, woven fabric pads, suede pads, and the like, of which suede pads are the most preferred. The polishing pad 10 is different in hardness.

  The polishing pad 30 is thinner than the thickness of the hard urethane pad (typically 1.5 mm to 2.0 mm), and typically has a thickness of about 0.3 mm to 0.9 mm. Also, the groove depth formed on the pad surface is shallower than that of the hard urethane pad (typically 1.2 mm to 1.7 mm), typically 0.2 mm to 0.8 mm. Have a thickness of about.

The composition of the glass plate 40 is not particularly limited, but is preferably easy to chemically strengthen. As a preferable composition of the glass plate 10, for example, expressed as mol% based on oxide, SiO ₂ : 50 to 80%, Al ₂ O ₃ : 2 to 25%, Li ₂ O: 0 to 10%, Na ₂ O _{: 0~18%, K 2 O:} 0~10%, MgO: 0~15%, CaO: 0~5% and _ZrO 2: a glass containing 0 to 5%.

Besides, by mol% based on _{oxides, SiO 2: 50~74%, Al} 2 O 3: 1~10%, Na 2 O: 6~14%, K 2 O: 3~11%, MgO : 2~15%, CaO: 0~6% and _ZrO 2: comprises 0-5%, the total content of SiO ₂ and _Al 2 _{O 3} is 75% or less, the content of Na ₂ O and _{K 2} O total from 12 to 25% of glass total content of MgO and CaO is _{7~15%, SiO 2: 68~80%} , Al 2 O 3: 4~10%, Na 2 O: 5~15 %, K ₂ O: 0 to 1%, MgO: 4 to 15% and ZrO ₂ : Glass containing 0 to 1%, SiO ₂ : 67 to 75%, Al ₂ O ₃ : 0 to 4%, Na ₂ O _{: 7~15%, K 2 O:} 1~9%, MgO: 6~14% and _ZrO 2: comprises 0 to 1.5%, SiO ₂ and l ₂ total content of O ₃ is 71-75%, the sum is 12 to 20% content of Na ₂ O and _{K 2} O, when containing CaO, the content is less than 1% It is preferable to use glass.

  The glass plate 10 before chemical strengthening is produced by a method such as a float method, a fusion down draw method, a slit down draw method, or a redraw method, and is chemically strengthened using a known chemical strengthening treatment.

  The polishing liquid (polishing slurry) includes, for example, rare earth oxides such as colloidal silica and cerium oxide, zirconium oxide, aluminum oxide, magnesium oxide, silicon oxide, silicon carbide, manganese oxide, iron oxide, diamond, boron nitride and zircon. A slurry containing known abrasive grains is used. Abrasive grains may be used alone or in combination of two or more.

  As shown in FIG. 4, FIG. 4 shows a case where the warped glass plate 40 is convex toward the polishing pad 30 for upper surface polishing (convex upward). In this embodiment, since the polishing pad 30 having a Shore A hardness of 70 to 95 is used, the polishing pad 30 is not deformed into a shape following the curved surface of the glass plate 40, and the convex portion of the glass plate 40 is centered. Polishing can be performed in a state in which polishing pressure is easily applied. Therefore, polishing after chemical strengthening can be carried out while polishing more convex portions of the glass plate 40 and improving the warp of the glass plate 40.

  On the other hand, as shown in FIG. 5, even when the warped glass plate 40 is convex toward the polishing pad 10 for lower surface polishing (convex downward), it is easy to apply polishing pressure around the convex portion of the glass plate 40. Since it can grind | polish with this, more convex parts can be grind | polished.

  In order to confirm the above-mentioned effect, the glass plate was placed so that the convex portion of the glass plate was on the upper surface using a polishing pad of Shore A hardness (51.5, 78.0, 91.0) of three types of pads. The glass substrate was polished and the amount of warpage change of the glass substrate was measured. The results are shown in Table 1. As the polishing amount, a value obtained by adding the polishing amounts on both sides of the glass substrate is described (that is, one side is a half value). The amount of warpage change was a positive value when the warpage of the glass substrate increased before and after polishing after chemical strengthening, and a negative value when the warpage decreased. The amount of warpage of the chemically strengthened glass plate used in this measurement before chemical polishing and before polishing was about 60 μm on average. Here, the amount of warpage is a warpage obtained by measuring the amount of warpage in an area of 60 mm × 34 mm in the center using FT17 manufactured by Nidek and converting the result into a size of 150 × 153 mm.

  As shown in Table 1, when polishing was performed using a polishing pad having a Shore A hardness of 51.5, warping deteriorated. On the other hand, when the Shore A hardness of the polishing pad is 78.0 and 91.0, the warpage improves even when the glass plate is placed and polished so that the convex portion of the glass plate is on the upper surface. became. Further, it has been found that warping is greatly improved by polishing 4 μm (single side 2 μm) or more using a polishing pad having a Shore A hardness of 78.0 or more.

  Furthermore, by using a polishing pad having a large Shore A hardness, it is possible to suppress an increase in the amount of change in warpage. Specifically, in the case of a polishing pad having a large Shore A hardness, even if the warpage becomes large to some extent during polishing, it becomes easy to apply polishing pressure around the convex portion of the substrate, resulting in warping of the glass substrate. Can be suppressed. Therefore, it is preferable to use a polishing pad having a large Shore A hardness even when polishing glass without warping.

  Next, the manufacturing method of a cover glass is demonstrated as an example of the manufacturing method of the chemically strengthened glass plate which concerns on this invention. First, the glass plate manufactured by the float process etc. is cut | disconnected and a predetermined glass base plate is sampled. Then, it cuts so that it may meet the size of a desired cover glass, and the chamfering process of an end surface is performed. Subsequently, the surface of the glass plate is polished (pre-strengthening polishing) using a double-side polishing apparatus to remove cracks.

Subsequently, chemical strengthening is performed. For example, chemical strengthening is performed by immersing in KNO ₃ molten salt at 400 ° C. to 450 ° C. for 1 hour to 10 hours. Moreover, after chemical strengthening, it is preferable to wash with water for the purpose of removing deposits such as molten salt adhering to the glass plate.

  Next, the surface of the glass plate is polished (polished after strengthening) using a double-side polishing apparatus, and the defect layer formed on the surface of the glass plate by chemical strengthening is removed. Finally, a black layer or the like having a light shielding property is printed on the peripheral edge of the glass plate, and the cover glass is manufactured.

  In the above example, the case where the chemically strengthened glass plate polished before strengthening is polished after strengthening is described, but the present invention is not limited thereto. For example, when polishing after chemical strengthening on a glass plate warped by chemical strengthening treatment, or polishing after chemical strengthening on a glass plate warped by performing etching treatment before chemical strengthening, etc. It doesn't matter.

10, 30 Polishing pad 20, 40 Glass plate

Claims (5)

A method for producing a chemically strengthened glass plate having a main surface on the front and back sides and an end surface connecting between the main surfaces on the front and back surfaces,
A method for producing a chemically strengthened glass sheet, comprising a step of polishing the front and back main surfaces with a polishing pad having a Shore A hardness of 70 to 95 after chemical strengthening.   2. The chemically strengthened glass sheet according to claim 1, wherein the chemically strengthened polishing step is a step of polishing the chemically strengthened glass having warpage on the front and back main surfaces. Method.   The method for producing a chemically strengthened glass sheet according to claim 1, wherein the polishing step after the chemical strengthening is performed by polishing 4 μm or more. Preparing a glass plate having a main surface of the front and back and an end surface connecting the main surfaces of the front and back;
Polishing the front and back main surfaces of the glass plate;
Chemically tempering the polished glass plate to form a chemically tempered glass plate;
Polishing the front and back main surfaces of the chemically strengthened glass plate;
A method for producing a chemically strengthened glass sheet, comprising:   5. The method for producing a chemically strengthened glass sheet according to claim 4, wherein 4 μm or more is polished in the step of polishing the front and back main surfaces of the chemically strengthened glass sheet.

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