JP2013040086A - Method for manufacturing tempered glass plate and cover glass, and cover glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a tempered glass plate with higher strength and light weight.SOLUTION: The method for manufacturing a tempered glass plate includes: a polishing process of polishing the surface of a glass plate 1 by using slurry containing colloidal silica having an average particle diameter of 80 nm or less; and a chemical tempering process of, after the polishing process, chemically tempering the glass plate 1. The polishing process includes a step of polishing the surface of the glass plate 1 by using slurry containing cerium oxide, and then polishing the surface of the glass plate 1 by using slurry containing colloidal silica having an average particle diameter of 80 nm or less.

Description

  The present invention relates to a tempered glass plate, a method for producing a cover glass, and a cover glass.

  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.

  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 (for example, Patent Document 1). Patent Document 1 discloses a glass plate and a method for manufacturing the same that suppress deformation and is not easily damaged by forming a compressive stress layer on the surface of the glass plate by chemical strengthening.

Japanese Patent Laid-Open No. 7-223845

  However, the glass plate used for the cover glass is required to have higher strength and lighter weight because the main surface is subjected to a larger stress than the outside.

  Therefore, an object of the present invention is to provide a method for producing a tempered glass plate that is stronger and lighter.

According to an aspect of the invention,
A polishing step of polishing the surface of the glass plate using a slurry containing colloidal silica having an average particle size of 80 nm or less;
A chemical strengthening step of chemically strengthening the glass plate after the polishing step;
The manufacturing method of a tempered glass board containing is provided.

  The present invention has the following effects.

  About the tempered glass board which is higher intensity | strength and lightweight, the manufacturing method can be provided.

FIG. 1 is a schematic diagram for explaining the state of the surface of a glass plate. FIG. 2 is a schematic view illustrating the distribution in the thickness direction of the residual stress of the glass plate after chemical strengthening. FIG. 3 is a schematic diagram for explaining the strength test method.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

The composition of the glass plate that can be used in the method for producing a tempered glass plate of the present invention is not particularly limited. 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 0.2 mm-2.5 mm normally.

[Polishing process (before chemical strengthening process)]
The schematic for demonstrating the state of the surface of a glass plate to Fig.1 (a) is shown. The surface of the glass plate 1 produced by a method such as a float method, a fusion down draw method, a slit down draw method, or a redraw method usually has a micro-order scratch 2 (sometimes referred to as a crack 2) or a glass plate. There are deflections and dents. More specifically, there are generally cracks 2 called Griffith flow on the surface of the glass. When a tensile stress is applied to the surface of the glass, stress concentration occurs in the crack, and the crack progresses to break the glass. Therefore, the surface of the glass plate is polished and flattened in order to remove the cracks 2 and the deflection and dent of the glass plate present on the surface of the glass plate. In addition, the length of the crack on the glass surface is usually about 0.1 μm to 3 μm.

  As a method for removing the cracks 2 on the surface of the glass plate 1, the surface of the glass plate is polished with a slurry containing colloidal silica having an average particle size of 80 nm or less, more preferably 20 nm or less. Colloidal silica refers to a colloid of silica or its hydrate, and usually has a particle size of 10 to 300 nm. As a particle size of the colloidal silica used in the glass plate strengthening method of the present invention, the average particle size is preferably 80 nm or less, and more preferably 20 nm or less.

  Fine irregularities of up to about 1 μm may remain on the surface of the glass plate subjected to chemical strengthening by ion exchange. When force acts on the glass, stress concentrates on the above-mentioned cracks and locations where fine irregularities exist, and may break even with a force smaller than the theoretical strength.

  By polishing using a slurry containing colloidal silica having an average particle size of 80 nm or less as abrasive grains, the surface of the glass plate can be uniformly flattened. For this reason, since chemically strengthened glass with a small fine unevenness | corrugation on the surface is obtained, since sufficient intensity | strength can be achieved in the intensity | strength test of a glass plate, it is preferable. The rotation speed and polishing pressure during polishing can be appropriately selected by those skilled in the art according to the composition of the glass plate.

  Usually, as a method of flattening the surface of the glass plate, wet etching or the like can be mentioned. In the present invention, polishing is performed using a slurry containing colloidal silica having an average particle size of 80 nm or less as abrasive grains. FIG. 1B is a schematic diagram for explaining the state of the surface of the glass plate 1 after the wet etching process. As apparent from FIG. 1B, the surface of the glass plate 1 processed by wet etching is not substantially flat although it depends on the etching conditions. Therefore, a sufficient strength cannot be achieved in the strength test of the glass plate, which is not preferable.

Further, it is more preferable to polish using a slurry containing abrasive grains described below before polishing using the slurry containing colloidal silica. Examples of abrasive grains that are preferably polished before using a slurry containing colloidal silica include rare earth oxides such as cerium oxide, zirconium oxide, aluminum oxide, magnesium oxide, and silicon oxide (colloidal silica). Conventional abrasive grains such as silicon carbide, manganese oxide, iron oxide, diamond, boron nitride and zircon. One type of these abrasive grains may be used alone, or two or more types may be used in combination. When polishing by these conventional polishing methods, after polishing, finish polishing is performed using abrasive grains containing colloidal silica having an average particle size of 80 nm or less. In general, for example, when a polishing process is performed using a slurry containing cerium oxide (CeO ₂ ) abrasive grains, the cerium oxide abrasive grains have an average particle diameter of 1.1 μm (= 1100 nm). . For this reason, in the polishing using only cerium oxide, bending and dent generated before the polishing process remain. Therefore, sufficient glass strength may not be obtained, which is not preferable.

[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.

  In FIG. 2, the schematic diagram which shows the thickness direction distribution of the residual stress S of the glass plate after chemical strengthening is shown. In FIG. 2, S1 is the maximum residual compressive stress of one surface layer (referred to as the surface layer) of the glass plate, and S2 is the maximum residual compressive stress of the other surface layer (referred to as the back layer) (usually S1 = S2). ), D1 is the thickness of the surface layer, D2 is the thickness of the back surface layer, D is the thickness of the glass plate, and T is the average residual tensile stress of the intermediate layer existing between the surface layer and the back surface layer. Further, the horizontal axis in FIG. 2 indicates the distance in the plate thickness direction when the surface layer is the reference point (= 0).

  As shown in FIG. 2, the compressive stress remaining in the front surface layer and the back surface layer tends to gradually decrease from the front surface and the back surface toward the inside. On the other hand, as a reaction for forming a front surface layer and a back surface layer in which compressive stress remains, an intermediate layer in which a tensile stress remains is formed between the front surface layer and the back surface layer. At this time, the tensile stress remaining in the intermediate layer is substantially constant.

In FIG. 2, S1, S2 (usually S2 = S1), D1, D2 (usually D2 = D1), and T can be adjusted by the strengthening treatment conditions, and the concentration and temperature of the treatment liquid for chemical strengthening, the chemical strengthening Those skilled in the art can adjust the time for immersing the glass in the treatment liquid. The chemical strengthening conditions and method in the present invention are not particularly limited, and known methods can be used. Specifically, a glass plate, for example, chemical strengthening is performed by immersing 1 hour to 10 hours in KNO ₃ molten salt at 400 ° C. to 450 ° C.. 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.

[Other processes]
A glass plate subjected to chemical strengthening by ion exchange may have 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, it is preferable to remove a layer (referred to as a heterogeneous layer) having defects and fine irregularities present on at least one surface of the chemically strengthened glass. In addition, although the thickness of the heterogeneous layer in which a defect exists is based also on the conditions of chemical strengthening and the surface state of the glass plate before a chemical strengthening process, it is 0.01-0.5 micrometer normally.

  Examples of the method for removing the heterogeneous layer including defects and fine irregularities include a method in which polishing is performed using abrasive grains containing colloidal silica having an average particle size of 80 nm or less.

  Before polishing with a slurry containing colloidal silica, such as rare earth oxides such as cerium oxide, zirconium oxide, aluminum oxide, magnesium oxide, silicon oxide, silicon carbide, manganese oxide, iron oxide, diamond, boron nitride and zircon Alternatively, polishing may be performed using a slurry containing known abrasive grains.

  As a method for removing a heterogeneous layer including defects and fine irregularities, a method for removing the heterogeneous layer by wet etching is also preferable. In this case, the etching conditions are not particularly limited as long as the heterogeneous layer including defects and fine unevenness can be removed. For example, as an etchant, hydrofluoric acid, an acidic solution containing hydrofluoric acid as a main component, hydrofluoric acid containing sulfuric acid, hydrochloric acid, phosphoric acid, nitric acid, mixed acid containing at least one of silicic acid, caustic soda, caustic potash, etc. Alkalis can be used. Moreover, etching temperature is 10 to 60 degreeC normally, Preferably it is 20 to 40 degreeC. Further, the etching time is usually 30 seconds to 30 minutes, preferably 1 minute to 10 minutes. These etching conditions can be appropriately selected by those skilled in the art so that the reaction product does not precipitate depending on the material of the glass substrate used.

  Since a deposit may adhere to the surface of the glass plate after polishing or etching, it is preferable to wash the glass plate after the treatment. The washing method is not particularly limited, and a known method can be used. For example, washing with an aqueous solution such as sulfuric acid, hydrochloric acid, or nitric acid can be performed in a state where ultrasonic waves are applied.

[Method for producing cover glass]
The glass plate strengthening method of the present invention can be applied to a method for manufacturing a cover glass for a display such as a mobile phone, a digital camera, and a touch panel display. The manufacturing method of tempered glass changes with uses, and if it uses the tempering method of the glass plate of this invention, it will not specifically limit as another process. An example is shown below, but the present invention is not limited to this example.

  First, the prepared glass base plate is formed into a desired size and shape to be finally finished through processes such as cutting, drilling, notching, polishing, and thread chamfering. At this time, in order to improve the handling of the subsequent process and reduce the process cost, it is cut into a size larger than the desired size to be finally finished, and after all the processing steps are completed, the desired size is obtained. It may be formed into a shape.

  The formed glass plate is strengthened by the method for producing tempered glass of the present invention. The reinforced glass plate is subjected to printing, antireflection coating, functional film bonding, and the like to produce a cover glass.

  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 50 mm, a width of 50 mm, and a thickness of 1.1 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 addition, the bottom surface and top surface in an Example and a comparative example refer to the surface (bottom surface) which contacted the molten tin in the case of shaping | molding by a float process, and the surface (top surface) on the opposite side.

  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 strengthened glass is washed with water and used for the next step.

(Cerium oxide polishing)
As a polishing slurry, cerium oxide having an average particle diameter (d50) of 1 μm is dispersed in water to prepare a slurry, and the flat glass is polished by about 3.0 μm using the obtained slurry.

(Colloidal silica polishing)
As a polishing slurry, colloidal silica having an average particle diameter (d50) of 80 nm (Compoule 80; manufactured by Fujimi Incorporated) is dispersed in water to prepare a slurry, and the obtained slurry is used to form a flat glass having a thickness of about 0.2 μm. Grind.

(Wet etching)
The flat glass is etched at 20 ° C. for 5 minutes using a mixed acid of hydrofluoric acid and hydrochloric acid (0.55 mass% hydrofluoric acid, 5.8 mass% hydrochloric acid) as an etchant.

[Example 1]
After the cerium oxide polishing was performed on the flat glass, colloidal silica polishing was performed, and the flat glass was reinforced by the chemical strengthening process. The cerium oxide polishing and colloidal silica polishing were performed on the top surface.

[Comparative Example 1]
After performing cerium oxide polishing on the flat glass, the flat glass was strengthened by a chemical strengthening process. The cerium oxide polishing was performed on the top surface.

[Comparative Example 2]
After performing wet etching on the flat glass, the flat glass was strengthened by a chemical strengthening process. The wet etching was performed on both the top surface and the bottom surface.

[Comparative Example 3]
The flat glass was strengthened by the chemical strengthening step, but none of the treatment before chemical strengthening was performed.

  Table 1 shows the conditions for each strengthening treatment in the examples and comparative examples.

［評価方法］
以下、評価方法を説明する。各実施例と比較例に関し、化学強化前の処理を行った面についてそれぞれ下記の評価を行った。比較例３（化学強化前処理なし）についてはトップ面を評価した。

[Evaluation method]
Hereinafter, the evaluation method will be described. With respect to each of the examples and comparative examples, the following evaluations were performed on the surfaces subjected to the treatment before chemical strengthening. For Comparative Example 3 (no chemical strengthening pretreatment), the top surface was evaluated.

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

In this Embodiment, the center area | region of the glass plate 1 was pressurized from the upper direction of the glass plate 1 obtained after the Example and the comparative example. The test conditions are as follows.
Sample thickness: 1.1 (mm);
Lowering speed of the pressing jig 3: 1.0 (mm / min):
At this time, the breaking load (unit N) when the glass was broken was defined as BOR strength, and the average value of 20 measurements was defined as BOR average strength.

<< Arithmetic average surface roughness Ra >>
The surface roughness of the glass substrate was measured using a stylus type surface roughness meter (Multimode V SPM-Nanoscope V controller manufactured by Veeco). In addition, the measured value measured the surface roughness of two arbitrary places from the glass plate, and showed it with the average value.

  Table 1 also shows the results of evaluation by the above-described evaluation method in the glass obtained by the glass strengthening method of the present invention.

  It can be seen that the glass obtained by the glass strengthening method of the present invention has smaller surface roughness and higher strength than the glass of the comparative example.

1 Glass plate 2 Scratches (cracks)
3 Pressure jig 4 Receiving jig

Claims (4)

A polishing step of polishing the surface of the glass plate using a slurry containing colloidal silica having an average particle size of 80 nm or less;
A chemical strengthening step of chemically strengthening the glass plate after the polishing step;
The manufacturing method of a tempered glass board containing.   The said grinding | polishing process is a process of grind | polishing using the slurry containing the colloidal silica whose average particle diameter is 80 nm or less, after grind | polishing the surface of the said glass plate using the slurry containing a cerium oxide. Method for manufacturing a tempered glass sheet.   The manufacturing method of the cover glass for displays including the manufacturing method of the tempered glass board of Claim 1 or 2.   The cover glass obtained by the manufacturing method of the cover glass of Claim 3.

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