JP2015137224A - Manufacturing method of strengthened glass plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of strengthened glass plate with higher strength.SOLUTION: A manufacturing method of strengthened glass plate comprises a chemical strengthening step of strengthening glass plate chemically, and a polishing after strengthening step of polishing the surface of the glass plate after the chemical strengthening step. A suede pad having a foaming resin layer is used in the polishing after strengthening step.

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 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 suede pad is used.
(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 method for producing a tempered glass sheet, wherein the polishing pad is a suede pad.
(3) The method for producing a tempered glass sheet according to (1) or (2), wherein the suede pad is buffed.
(4) The said suede pad is laminated | stacked on the nonwoven fabric, The manufacturing method of the tempered glass board in any one of (1)-(3) characterized by the above-mentioned.
(5) The tempered glass according to any one of (1) to (4), wherein the abrasive grains are abrasive grains containing 50% or more of cerium oxide having an average particle diameter of 0.2 to 1.5 μm. A manufacturing method of a board.

  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 a figure which shows the photograph of the cross section of a polishing pad, (a) is a suede pad, (b) is a nonwoven fabric pad, (c) is a hard urethane pad. It is a figure which shows the photograph of the surface of a polishing pad, (a) is a suede pad, (b) is a nonwoven fabric pad, (c) is a hard urethane pad. It is the schematic for demonstrating the method of an intensity | strength test. It is a figure which shows the atomic force microscope photograph of the tempered glass board grind | polished after reinforcement | strengthening, (a) is a tempered glass board grind | polished with the pad of the two-layer structure of a suede pad and a nonwoven fabric pad, (b) is a suede pad (C) is a tempered glass plate polished with a non-woven pad, and (d) is a tempered glass plate polished with a hard urethane pad.

Hereinafter, an embodiment of a method for producing a tempered 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 telephone, it is about 0.2 mm-2.5 mm normally, Preferably, it is 0.3 mm-0.7 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 the surface of the chemically strengthened glass plate 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 part formed in 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 the sun gear 13 and the ring gear 14 are rotationally driven at a predetermined rotation ratio, whereby the glass plate carrier. The planetary gear motion that revolves around the sun gear 13 is performed while 10 rotates.

  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 suede pads. The suede pad is obtained by attaching a foamed resin layer to a base material such as PET, and the hardness of the 4.5 mm thick laminated layer is 45 to 95 in Shore A hardness. The foamed resin layer is typically (soft) polyurethane. The suede pad may be a buffed suede pad in which the foamed resin layer is opened by buffing the surface of the foamed resin layer. The surface of the foamed resin layer is not buffed and the foamed resin layer is not buffed. It may be an untreated buffed untreated suede pad. FIG. 4A shows a cross-sectional photograph of the unbuffed suede pad, and FIG. 5A shows a photograph of the surface of the buffed suede pad.

  Moreover, it is good also as a 2 layer suede pad which has a 2 layer structure by attaching a soft base layer on a base material, and also attaching a buff process suede pad or a buff non-processed suede pad on it. Examples of the soft underlayer include unemployed cloth pads and woven cloth pads, and nonwoven cloth pads are preferable. The suede pad is preferably a buffed suede pad, and more preferably a two-layer suede pad.

  The suede pad 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 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, and preferably contain 50% or more of cerium oxide having an average particle diameter of 0.2 to 1.5 μm. .

[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 suede pad, which is a feature of the present invention, may be applied to pre-strengthening polishing (S3) as long as it is applied to 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 and comparative examples, the following steps were appropriately combined.

(Chemical strengthening)
The flat glass is 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 is 435 ° C., and the immersion time is 4 hours. The obtained chemically tempered glass (hereinafter referred to as tempered glass) is washed with water and subjected to the subsequent cerium oxide polishing or colloidal silica 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.

(Cerium oxide polishing)
As a polishing slurry, cerium oxide having an average particle diameter (d50) of 1 μm is dispersed in water to produce a slurry, and the tempered glass is polished by about 2.0 μm using the obtained slurry. In the slurry in which cerium oxide having an average particle diameter (d50) of 1 μm is dispersed in water, cerium oxide particles having a maximum of about 10 μm are present.

(Colloidal silica polishing)
As a polishing slurry, colloidal silica (Compol 80; manufactured by Fujimi Incorporated) having an average particle diameter (d50) of 80 nm is dispersed in water to prepare a slurry. Polish 0 μm.

[Example 1]
After strengthening the flat glass by the chemical strengthening step, colloidal silica polishing was performed on the strengthened glass. As a polishing pad, a non-woven pad is affixed to a PET substrate, and a buffed suede pad with a buffed surface of the foamed resin layer is affixed on the non-woven pad, and has a two-layer structure of a non-woven pad and a buffed suede pad. A two-layer suede pad was used.

[Example 2]
After strengthening the flat glass by the chemical strengthening step, the tempered glass was polished with cerium oxide. As a polishing pad, a non-woven pad is affixed to a PET substrate, and a buffed suede pad with a buffed surface of the foamed resin layer is affixed on the non-woven pad, and has a two-layer structure of a non-woven pad and a buffed suede pad. A two-layer suede pad was used.

[Example 3]
After strengthening the flat glass by the chemical strengthening step, the tempered glass was polished with cerium oxide. As a polishing pad, a buffed suede pad in which a foamed resin layer whose surface was buffed was attached to a PET substrate was used.

[Example 4]
After strengthening the flat glass by the chemical strengthening step, the tempered glass was polished with cerium oxide. As the polishing pad, a buffed untreated suede pad in which a foamed resin layer whose surface was not buffed was attached to a PET substrate was used.

[Comparative Example 1]
After strengthening the flat glass by the chemical strengthening step, the tempered glass was polished with cerium oxide. As the polishing pad, a non-woven pad in which a non-woven fabric was bonded to a PET substrate was used.

[Comparative Example 2]
After strengthening the flat glass by the chemical strengthening step, the tempered glass was polished with cerium oxide. As the polishing pad, a hard urethane pad in which hard urethane was attached to a PET substrate was used.

  Table 1 shows the conditions of each polishing treatment in Examples and Comparative Examples.

[Evaluation method]
Hereinafter, the evaluation method will be described. For each of the examples and comparative examples, the following Ball on Ring test was performed after the polishing treatment. FIG. 6 is a schematic diagram for explaining the strength test used in the present invention.

《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. . In FIG. 6, 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 this Embodiment, the center area | region of the tempered glass board 1 was pressurized from upper direction after cut | disconnecting the tempered glass obtained after the grinding | polishing process of an Example and a comparative example into a 50 mm square. 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 the BOR strength, and Table 1 shows a range of measured values for 20 times. In addition, about Example 1, it is an average value of 20 measurements.

  From the results of BOR strength, when Examples 1 and 2 using a two-layer suede pad, which is the same polishing pad, are compared, in Example 1 in which the average particle diameter (d50) of the abrasive grains is remarkably small, BOR strength is high. It became. This is presumably because the surface roughness of the tempered glass plate is greatly different when polished with abrasive grains having greatly different average particle diameters (d50). However, if the average particle diameter (d50) of the abrasive grains is small, an attempt to polish the same polishing amount will increase the polishing time accordingly.

  Next, in Examples 2 to 4 and Comparative Examples 1 and 2 using the same abrasive grains (cerium oxide), the BOR strength is compared with that of Comparative Example 1 (nonwoven fabric pad) and 2 (hard urethane pad). Examples 2-4 using suede pads gave high results.

  Considering this result with reference to the cross-sectional photograph of FIG. 4 and the surface photograph of FIG. 5, the hard urethane pad has pores (holes) larger than the cerium oxide particles (up to about 10 μm) contained in the abrasive grains. However, since the hard urethane pad itself is hard, there is no escape area for the abrasive grains on the surface other than the pores, and the contact between the abrasive grains and the glass surface becomes hard, and it is considered that minute scratches are likely to occur. Therefore, it is considered that the BOR strength is lowered.

  On the other hand, in the suede pad, since the foamed resin layer itself can be deformed softly and elastically, the contact between the abrasive grains and the glass surface is extremely mild, and it is considered that minute scratches are difficult to occur. In particular, in the buffed suede pad, pores larger than the cerium oxide particles (up to about 10 μm) contained in the abrasive grains are formed, and the average particle diameter of the cerium oxide particles in the foamed resin layer itself ( Since micropores of the same level as d50) are formed, it is considered that the contact between the abrasive grains and the glass surface is extremely mild and it is difficult for microscopic scratches to occur. Therefore, it is considered that the BOR strength is higher than that of the hard urethane pad.

  In addition, in the non-woven fabric pad, although pores as small as the average particle diameter (d50) of cerium oxide particles are formed, cerium oxide particles contained in the abrasive grains (up to about 10 μm depending on the fiber orientation) ), The distance between the fibers becomes smaller, and the contact with the glass surface changes depending on the direction of the fibers. The contact between the abrasive grains and the glass surface is basically a mild contact, and it is considered that minute scratches are difficult to occur. Therefore, it is considered that the BOR strength is higher than that of the hard urethane pad.

  Therefore, in order to verify whether or not the BOR intensity is increased if the glass surface is good, the surface roughness (Ra) is further measured for each of Examples 2 and 3 and Comparative Examples 1 and 2 using an atomic force microscope (AFM). Was measured. The results of the surface roughness (Ra) are shown in Table 2, and the results of ranking the BOR strength and the surface roughness (Ra) in Examples 1 and 3 and Comparative Examples 1 and 2 are shown in Table 3.

  From the results of Table 3, when Example 3 (buffed suede pad) and Comparative Example 1 (nonwoven pad) are compared, Comparative Example 1 (nonwoven pad) is more surface than Example 3 (buffed suede pad). Despite the small roughness (Ra), the BOR strength was better in Example 3 (buffed suede pad) than in Comparative Example 1 (nonwoven fabric pad), that is, higher in strength. Therefore, the BOR strength and the surface roughness (Ra) of the tempered glass do not necessarily match, and it has been proved that using a suede pad for the tempered glass is effective for increasing the BOR strength. This is presumably because the wall constituting the hole of the suede pad is thin and easily deformed, so that it is difficult to be in a polished state in which scratches enter.

  Moreover, in Examples 2-4, Example 2 (two-layer suede pad which has a two-layer structure of a nonwoven fabric pad and a buff processing suede pad), Example 3 (buff processing suede pad) in order with high BOR strength, Example 4 (unbuffed suede pad) was obtained. In this regard, in the two-layer suede pad, since the nonwoven fabric is interposed between the substrate and the suede pad, it is considered that the contact between the abrasive grains and the glass surface becomes milder due to the elasticity of the nonwoven fabric. In addition, as described above, the buffed suede pad has pores on the pad surface as compared to the unbuffed suede pad, and thus it is considered that the contact between the abrasive grains and the glass surface becomes milder.

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 tempered glass board, 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 suede pad is used. 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 method for producing a tempered glass sheet, wherein the polishing pad is a suede pad.   The method of manufacturing a tempered glass sheet according to claim 1, wherein the suede pad is buffed.   The said suede pad is laminated | stacked on the nonwoven fabric, The manufacturing method of the tempered glass board of any one of Claims 1-3 characterized by the above-mentioned.   The abrasive grains are abrasive grains containing 50% or more of cerium oxide having an average particle diameter of 0.2 to 1.5 µm, The tempered glass plate production according to any one of claims 1 to 4, Method.