JP2017014023A - Method for producing strengthened glass plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a strengthened glass plate having higher strength, and a method for producing the same.SOLUTION: Provided is a method for producing a strengthened glass plate comprising: a chemical strengthening step of chemically strengthening a glass plate; and a polishing step after strengthening of polishing the surface of the glass plate. In the polishing step after strengthening, a strengthened glass plate 30 is retained to a carrier 10 for a both side polishing apparatus, is sandwiched between polishing pads 16, 18 fitted to the upper surface plate and the lower surface plate and is polished while feeding a polishing liquid containing abrasives. As the polishing pads, non-fabric pads are used, and the polishing is performed in a state where the deformation quantity of the non-fabric pads reaches 0.04 mm or more.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing a tempered 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. In general, when the glass plate is thinned, the strength is lowered. Therefore, a cover glass having higher strength than before is required. Further, a glass plate having a higher strength is demanded other than the cover glass. As a method for compensating for the lack of strength of the glass plate, a technique for chemically strengthening the glass plate by an ion exchange method or the like has been developed. By forming a compressive stress layer on the surface of the glass plate by chemical strengthening, it is possible to provide a glass plate that suppresses bending and is not easily damaged.

  Patent Document 1 discloses a method of providing a tempered glass plate that is stronger and lighter by performing a post-strengthening polishing step in which polishing is performed using a slurry containing colloidal silica having an average particle size of 80 nm or less after chemical strengthening. Is disclosed.

JP 2012-218995 A

  However, a tempered glass plate used for a cover glass or the like is required to have a higher strength because its main surface is subjected to a greater stress than the outside.

  Therefore, an object of the present invention is to provide a method for producing a tempered glass sheet having higher strength.

The present invention provides the following aspects.
(1) a chemical strengthening process for chemically strengthening a glass plate;
A post-strengthening polishing step of polishing the surface of the glass plate after the chemical strengthening step, and a method for producing a strengthened glass plate,
In the post-strengthening polishing step, a non-woven pad is used,
A method for producing a tempered glass sheet, comprising polishing the nonwoven fabric pad in a state where the deformation amount is 0.04 mm or more.
(2) A tempered glass plate is held by a glass plate carrier that performs planetary gear motion between a sun gear and a ring gear of a double-side polishing apparatus, and the tempered glass plate held by the glass plate carrier is used as an upper surface plate and a lower surface plate. A method for producing a tempered glass plate, which is sandwiched between polishing pads attached to and manufactured by polishing while supplying a polishing liquid containing abrasive grains,
The polishing pad is a non-woven pad,
The manufacturing method of the tempered glass board characterized by grind | polishing in the state from which each deformation | transformation amount of the said nonwoven fabric pad will be 0.04 mm or more.
(3) The method for producing a tempered glass sheet according to (1) or (2), wherein polishing is performed at a polishing pressure of 60 to 120 g / cm ² .
(4) The method for producing a tempered glass sheet according to any one of (1) to (3), wherein the nonwoven fabric pad has a Shore A hardness of 45 to 95.
(5) The method for producing a tempered glass plate according to any one of (1) to (4), wherein the tempered glass plate is a cover glass.

  According to the method for producing a tempered glass sheet of the present invention, a high-strength tempered glass sheet can be produced.

It is a schematic block diagram of a double-side polishing apparatus. It is a schematic diagram of the tempered glass board clamped between the polishing pads in the double-side polishing apparatus. It is a flowchart explaining the flow of the manufacturing method of a cover glass. It is the schematic for demonstrating the method of an intensity | strength test. It is a graph which shows the relationship between the Shore A hardness of the nonwoven fabric pad in Examples 1-4, and the BOR intensity | strength of the tempered glass after grinding | polishing. It is a graph which shows the relationship between the deformation amount of the nonwoven fabric pad in Examples 1-4, and the BOR intensity | strength of the tempered glass after grinding | polishing.

Hereinafter, an embodiment of a method for producing a strengthened glass sheet of the present invention will be described with reference to the drawings.
The manufacturing method of the tempered glass board of this invention is equipped with the chemical strengthening process which chemically strengthens a glass plate, and the post-strengthening grinding | polishing process which grind | polishes the surface of the said glass plate after this chemical strengthening process.

[Chemical strengthening process]
In the chemical strengthening step, the surface of the glass is ion-exchanged to form a surface layer in which compressive stress remains. Specifically, by ion exchange on the surface of the glass, ions having a small ion radius (for example, Li ions and Na ions) contained in the glass are replaced with ions having a large ion radius (for example, K ions). . Thereby, compressive stress remains on the surface of the glass, and the strength of the glass is improved.

The composition of the glass plate for chemical strengthening is not particularly limited as long as it can be chemically strengthened. Preferred composition of the glass plate, for example, by mol% based on _{oxides, SiO 2: 50~80%, Al} 2 O 3: 2~25%, Li 2 O: 0~10%, 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 is produced by a method such as a float method, a fusion down draw method, a slit down draw method, or a redraw method.

  Moreover, although the thickness of a glass plate changes with uses, in the case of cover glass uses, such as a mobile phone, it is about 0.3 mm-1.5 mm normally, Preferably, it is 0.35 mm-1.2 mm.

  A tempered glass plate subjected to chemical strengthening by ion exchange has defects on its surface. In addition, fine irregularities of up to about 1 μm may remain. When force acts on the glass, stress concentrates on the above-described defects and fine irregularities and may break even with a force smaller than the theoretical strength. Therefore, in the present invention, a layer (referred to as a defect layer) having defects and fine irregularities present on at least one surface of the glass after chemical strengthening is removed. In addition, although the thickness of the defect layer in which a defect exists is based also on the conditions of chemical strengthening, it is 0.01-0.5 micrometer normally.

[Polishing post-strengthening process]
Examples of a method for removing a defect layer including defects and fine irregularities include a method of polishing using a double-side polishing apparatus 12 shown in FIGS. 1 and 2.

  As shown in FIG. 1, a glass plate carrier 10 on which a glass plate 30 (see FIG. 2) can be installed is set between the sun gear 13 and the ring gear 14 in the double-side polishing apparatus 12. The gear portion 10a formed on the outer peripheral surface of the sun gear 13, the ring gear 14 and the glass plate carrier 10 constitutes a planetary gear mechanism, and rotates the sun gear 13 and the ring gear 14 at a predetermined rotation ratio, thereby enabling the glass plate. The carrier 10 performs planetary gear motion that revolves around the sun gear 13 while rotating.

  At this time, the glass plate carrier 10 holds the glass plate 30 in the glass plate holding hole 11 formed in the glass plate holding portion 10b inside the gear portion 10a, as shown in FIG. Is sandwiched between an upper surface plate 15 and a lower surface plate (not shown) on which polishing pads 16 and 18 are mounted, and the glass plate 30 is pressed with a predetermined polishing load. A polishing liquid (abrasive slurry) containing abrasive grains is supplied between the polishing pads 16 and 18 and the glass plate carrier 10 and the glass plate 30, and the upper surface plate 15 and the lower surface plate rotate relative to each other. Thus, both main planes of the glass plate held by the glass plate carrier 10 are simultaneously polished.

  The polishing pads 16 and 18 are nonwoven fabric pads. The nonwoven fabric pad is a soft polishing pad in which a felt in which fibers are entangled without weaving, or a material in which this felt is impregnated with rubber or resin is attached to a substrate such as PET. The hardness is preferably 45 to 95 in terms of Shore A hardness when laminated to a thickness of 4.5 mm. The fibers constituting the nonwoven fabric pad can be appropriately selected from polyester fibers, aramid fibers, nylon fibers, polyolefin fibers and the like, among which polyester fibers are most preferable. The resin can be appropriately selected from polyurethane, epoxy, and the like, and among them, polyurethane is most preferable.

In addition, each of the polishing pads 16 and 18 is set such that a deformation amount (hereinafter also referred to as a sinking amount) due to a polishing pressure at the time of polishing is 0.04 mm or more. The amount of deformation of each polishing pad 16, 18 is the distance between the surface of the most contracted polishing pad 16, 18 in contact with the glass plate 30 and the portion located between the glass plates 30 and closest to the glass plate carrier 10. Yes, represented by Dp in FIG. The polishing pressure can be appropriately set depending on the relationship between the polishing time and the polishing amount, but is preferably 50 to 120 g / cm ² (SI), more preferably 60 to 100 g / cm ² .

  That is, if the polishing pressure is constant, in order to secure a deformation amount (sinking amount) of 0.04 mm or more due to the polishing pressure during polishing, a polishing pad having a low hardness, that is, a soft polishing pad, or a hardness of When a high, that is, a hard polishing pad is used, the polishing pad can be deformed by increasing the thickness of the polishing pad. In this embodiment, the amount of deformation was measured by applying pressure while the polishing pad was wet. By measuring in a wet state, it can be measured under the same conditions as during polishing.

  The nonwoven fabric pad typically has a thickness of about 1.0 mm to 5.0 mm. The depth of the groove formed on the pad surface typically has a thickness of about 50% with respect to the thickness of the polishing pad.

  The glass plate carrier 10 is manufactured by laminating a plurality of prepregs. The material of the prepreg is not particularly limited, and can be selected depending on the amount of deformation of the target glass plate carrier 10 or the like. For example, a glass fiber cloth, a glass fiber nonwoven cloth, an aramid fiber nonwoven cloth, a polyester fiber cloth or the like is used as a base material, and a material impregnated with an epoxy resin, a phenol resin, an unsaturated polyester resin, a polyimide resin or the like is used. be able to.

  Moreover, the prepreg to be used is not limited to one type, and prepregs of different materials may be laminated. The laminated prepreg is pressurized and heated with a press to produce the glass plate carrier 10.

  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.

[Other processes]
The manufacturing method of the tempered glass plate of the present invention may include other steps of removing scratches (cracks) existing on the surface of the glass plate and bending or dents of the glass plate before the step of chemically strengthening. As a method of removing the cracks on the surface of the glass plate before the chemical strengthening treatment, a method of polishing the surface of the glass plate can be mentioned as in the above-described step of removing the defective layer.

Next, a cover glass manufacturing method will be described with reference to FIG. 3 as an example of a method for manufacturing a tempered glass sheet of the present invention.
In the cover glass manufacturing method, first, a glass plate manufactured by a float method or the like is cut to obtain a predetermined glass base plate (S1). 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 (S2). Subsequently, the surface of the glass plate is polished (pre-strengthening polishing) using the double-side polishing apparatus 12 to remove cracks (S3).

Subsequently, chemical strengthening is performed (S4). 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.

  Subsequently, the surface of the glass plate is polished (polished after strengthening) using the double-side polishing apparatus 12, and the defect layer formed on the surface of the glass plate by chemical strengthening is removed (S5). Finally, a black layer having a light shielding property or the like is printed on the peripheral edge of the glass plate (S6), and the cover glass is manufactured.

  The polishing using the nonwoven fabric pad, which is a feature of the present invention, may be applied to the pre-strengthening polishing (S3) as long as it is applied to the post-strengthening polishing (S5).

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

In all Examples and Comparative Examples, flat glass having a length of 300 mm, a width of 225 mm, and a thickness of 0.56 mm obtained by molding after the float method was used. The composition of the flat glass used was expressed in terms of mol% on the basis of oxide, SiO ₂ : 64%, Al ₂ O ₃ : 8%, MgO: 11%, Na ₂ O: 12.5%, ZrO ₂ : 0.00. It was 5%.

  In the following examples, the non-woven pads of Examples 1 to 4 were subjected to a polishing treatment after chemical strengthening treatment (after strengthening). Table 1 shows the thickness, density, compression rate, deformation amount, compression elastic modulus, and hardness of the nonwoven fabric pads of Examples 1 to 4.

(Chemical enhancement)
The flat glass was immersed in KNO ₃ molten salt, subjected to ion exchange treatment, and then chemically strengthened by cooling to near room temperature. At this time, the temperature of the KNO ₃ molten salt was 435 ° C., and the immersion time was 4 hours. The obtained chemically tempered glass (hereinafter referred to as tempered glass) was washed with water and subjected to the next cerium oxide polishing step. The tempered glass after tempering had a surface compressive stress (CS) of 700 ± 50 MPa and a compressive stress layer depth (DOL) of 18 ± 2 μm.

(Polishing after strengthening)
As a polishing slurry, cerium oxide having an average particle diameter (d50) of 1 μm was dispersed in water to prepare a slurry, and the tempered glass was polished for a predetermined time using the obtained slurry.

[Evaluation method]
Hereinafter, the evaluation method will be described. For each example, the following Ball on Ring test was performed after polishing.

《Ball on Ring test》
In the Ball on Ring (BOR) test, the tempered glass plate 1 was pressed with a pressurizing jig 2 made of SUS304 while the tempered glass plate 1 was placed horizontally, and the strength of the tempered glass plate 1 was measured. . FIG. 4 is a schematic diagram for explaining the strength test used in the present invention. In FIG. 4, a tempered glass plate 1 as a sample is horizontally installed on a receiving jig 3 made of SUS304. A pressurizing jig 2 for pressurizing the tempered glass plate 1 is installed above the tempered glass plate 1.

In the present embodiment, the central region of the tempered glass plate 1 is pressurized from above the tempered glass plate 1. The test conditions are as follows.
Sample thickness: 0.56 (mm);
Lowering speed of the pressure jig 2: 1.0 (mm / min):
At this time, the breaking load (unit N) when the glass was broken was defined as BOR strength. The BOR intensity shown in Table 1 was obtained by calculating the average of the BOR intensity for a predetermined number of times (N number) while changing the polishing pressure and the platen rotation speed, and set the range in which the average of the obtained BOR intensity could be included.

For example, in Example 1, as shown in Table 2 below, 6 lots (N number) were polished under each condition while changing the polishing pressure within the range of 60 to 100 g / cm ³ and the lower platen rotation speed within the range of 20 to 40 rpm. Went. The average of 6 lots is shown in Table 2 as BOR intensity. Further, the machining allowance was also measured and shown in Table 2. In Example 1, the lowest BOR intensity average value is 323N and the highest value is 339N. When rounded off, the average BOR intensity range can be 320N to 340N. Table 1 shows this range as BOR intensity. Note that the lower surface plate, the upper surface plate, the carrier rotation, and the carrier revolution are set in advance at predetermined ratios, and the polishing time is 300 seconds.

FIG. 5 is a graph showing the relationship between the Shore A hardness of the nonwoven fabric pad in Examples 1 to 4 and the BOR strength of the tempered glass after polishing.
When comparing the nonwoven fabric pads having substantially the same thickness (about 1.35 mm) in Examples 1 to 3, the Shore A hardness decreases, that is, as the nonwoven fabric pad becomes softer, the BOR strength of the sheet glass increases. I understand. On the other hand, when the non-woven pad of Example 4 (3 mm) having a large plate thickness is used, it can be seen that the BOR strength of the plate glass is high even though the Shore A hardness is high, that is, the non-woven pad is hard.

FIG. 6 is a graph showing the relationship between the amount of deformation (the amount of deformation of the nonwoven fabric pad) and the BOR strength of the tempered glass after polishing when a load of 100 g / cm ² is applied to the nonwoven fabric pads in Examples 1 to 4.
As apparent from FIG. 6, when the deformation amount of the nonwoven fabric pad is taken on the horizontal axis, it can be seen that the BOR strength increases as the deformation amount of the nonwoven fabric pad increases. This is presumably because, by ensuring a predetermined amount of deformation, the abrasive grains can escape to the non-woven fabric pad during polishing, so that the contact between the abrasive grains and the glass surface becomes mild and it is difficult for fine scratches to occur. Thus, it is thought that the BOR intensity | strength of a tempered glass board becomes high by ensuring the deformation amount of a nonwoven fabric pad.

  From FIG. 5 and FIG. 6, in order to ensure the deformation amount of the nonwoven fabric pad, when using a soft polishing pad with a low hardness of the polishing pad or using a polishing pad with a high hardness (hard), the thickness of the polishing pad is changed. It turns out that thickening is effective.

  From FIG. 6, linearity is recognized between the deformation amount of the nonwoven fabric pad and the BOR strength. When an approximate straight line (regression straight line) is drawn on Examples 1 to 4, y = 1374.8x + 151.11 is obtained. When the BOR strength is 200 N or more, the deformation amount of the nonwoven fabric pad is 0.04 mm or more, and the BOR strength Is 250 N or more, the amount of deformation of the nonwoven fabric pad needs to be 0.072 mm or more.

The present invention is not limited to the embodiment described above, and can be implemented in various forms without departing from the gist of the present invention.
For example, in the said embodiment, although the manufacturing method of the cover glass was illustrated as an example of the manufacturing method of a glass plate, it is applicable not only to this but glass of various uses.

DESCRIPTION OF SYMBOLS 10 Glass plate carrier 10a Gear portion 10b Glass plate holding portion 11 Glass plate holding hole 12 Double-side polishing device 13 Sun gear 14 Ring gear 15 Upper surface plate 16 Polishing pad 18 Polishing pad

Claims (5)

A chemical strengthening process to chemically strengthen the glass plate;
A post-strengthening polishing step of polishing the surface of the glass plate after the chemical strengthening step, and a method for producing a strengthened glass plate,
In the post-strengthening polishing step, a non-woven pad is used,
A method for producing a tempered glass sheet, comprising polishing the nonwoven fabric pad in a state where the deformation amount is 0.04 mm or more. A tempered glass plate is held on a glass plate carrier that performs planetary gear motion between a sun gear and a ring gear of a double-side polishing apparatus, and the tempered glass plates held on the glass plate carrier are attached to an upper surface plate and a lower surface plate. A method for producing a tempered glass plate, which is produced by sandwiching between polishing pads and polishing while supplying a polishing liquid containing abrasive grains,
The polishing pad is a non-woven pad,
The manufacturing method of the tempered glass board characterized by grind | polishing in the state from which each deformation | transformation amount of the said nonwoven fabric pad will be 0.04 mm or more. The method for producing a tempered glass sheet according to claim 1, wherein polishing is performed at a polishing pressure of 60 to 120 g / cm ² .   The method for producing a tempered glass sheet according to any one of claims 1 to 3, wherein the nonwoven fabric pad has a Shore A hardness of 45 to 95.   The said tempered glass board is a cover glass, The manufacturing method of the tempered glass board of any one of Claims 1-4 characterized by the above-mentioned.

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