JP5074978B2 - Manufacturing method of glass substrate of cover glass for portable device - Google Patents

Description

  The present invention relates to a glass substrate (cover glass) used for protecting a display screen of a portable terminal device such as a mobile phone or a PDA (Personal Digital Assistant), a glass substrate used for a main body of a portable device, and a method for manufacturing the same. .

In mobile terminal devices such as mobile phones and PDAs, and other mobile devices, a protective plate is provided in order to prevent an impact or external force from being applied to the display (for example, Patent Document 1). 2. Description of the Related Art In recent years, a protective plate using chemically strengthened glass that has strength even if it is a thin plate has been proposed with a reduction in thickness of portable terminal devices and portable devices (for example, Patent Document 2).
JP 2004-299199 A JP 2007-99557 A

  In the conventional processing method described in Patent Document 2, the glass end surface has a rough surface roughness, and the glass end surface is chamfered to have a microcrack of about several tens μm to several hundreds μm. However, there is a problem that the mechanical strength required for the above cannot be obtained.

  In order to solve this problem, in the prior application (Japanese Patent Application No. 2007-325542), the present applicant forms a resist pattern of a desired shape on a glass substrate, and etches the glass substrate using the resist pattern as a mask. Thus, it is provided to obtain a glass substrate having a desired shape.

  However, in this method, as shown in FIG. 7, since etching proceeds isotropically from both main surfaces 41a and 41b of the glass substrate 41 facing each other, etching from the main surface 41a side and main surface 41b are performed. A top portion 41d of the end surface 41c formed by etching from the side is formed. The top 41d is a portion that protrudes extremely on the end face 41c. A glass substrate having such a top 41d may be broken during handling or chipping, and the breakage or chipping may cause the portion to become the starting point of cleavage. There is a problem of lowering the strength.

The present invention has been made in view of the above points, and provides a glass base material for a cover glass for a portable device that is safe and has high mechanical strength because there is no extremely projecting portion on the end face, and a method for manufacturing the same. For the purpose.

The manufacturing method of the glass substrate of the cover glass for portable devices of the present invention is an etchant capable of etching the glass substrate using a resist pattern formed on each of one and the other main surfaces of the plate-like glass substrate as a mask. Etching the glass substrate from each of one and the other main surfaces of the glass substrate to obtain a glass substrate by cutting into a desired shape, and to the outside in the surface direction of the main surface at the end surface of the glass substrate A step of locally applying thermal energy that can soften the glass substrate surface to the protruding top , and after locally applying thermal energy to the end surface of the glass substrate, the ion exchange treatment And a step of chemically strengthening the surface of the glass substrate .

  According to this method, since the heat energy that can soften the glass substrate surface is locally applied to the end surface of the glass substrate that has been cut into a desired shape by etching, the main surface and the end surface of the glass substrate. Since a roundness is formed between the glass substrate and the glass substrate, there can be obtained a glass substrate that does not have an extremely projecting portion on the end face and can exhibit high mechanical strength.

In the manufacturing method of the glass substrate of the cover glass for portable devices of the present invention, after applying thermal energy locally to the end surface of the glass substrate, before chemically strengthening, the end surface of the glass substrate It is preferable to subject the glass substrate to which heat energy has been locally applied to an annealing treatment to alleviate the thermal strain generated by applying the heat energy .

In the method for manufacturing a glass substrate of a cover glass for a portable device according to the present invention, the thermal energy is energy generated from any one of a discharge source, a heating source, and a light source, and is relative to an end surface of the glass substrate. It is preferable to perform any one of heat treatment, electric discharge machining treatment, and light irradiation treatment locally .

In the manufacturing method of the glass substrate of the cover glass for portable devices of this invention, it is preferable to make a high temperature member approach the end surface of the said glass substrate, and to heat-process by radiant heat.

  The glass substrate of the present invention is formed by etching the glass substrate with an etchant capable of etching the glass substrate, using the resist pattern formed on the main surface of the plate-like glass substrate as a mask, and cutting the glass substrate into a desired shape. Since it is obtained by locally applying thermal energy that can soften the glass substrate surface to the end surface of this glass substrate, there is no part that protrudes extremely on the end surface. In addition, high mechanical strength can be exhibited.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
The glass substrate according to the embodiment of the present invention is obtained by etching the glass substrate with an etchant capable of etching the glass substrate using a resist pattern formed on the main surface of the plate-like glass substrate as a mask. It is obtained by cutting out into a shape to obtain a glass substrate, and locally applying thermal energy that can soften the glass substrate surface to the end face of the glass substrate.

  Fig.1 (a) is a figure which shows a part of glass base material obtained by etching a glass substrate and cutting out to a desired shape. The glass substrate 1 shown in FIG. 1A has a pair of opposing main surfaces 11 and 12 and an end surface 13. When a resist pattern is formed on each of the main surfaces 11 and 12 of the glass substrate and the glass substrate is etched using the resist pattern as a mask, the etching proceeds isotropically from both the main surfaces 11 and 12 facing the glass substrate. Further, the top portion 14 is formed on the end face 13 by etching from the main surface 11 side and etching from the main surface 12 side. In this etching, since the etching proceeds so as to draw a substantially circular arc from the main surface 11 side and the main surface 12 side to the inside of the glass substrate in a cross-sectional view, when the glass substrate is cut out, the glass substrate In the vicinity of the center thickness, the arcs intersect with each other. As shown in FIG. 1A, the top portion 14 is the most protruding portion of the end surface 13.

  The etching method for etching the glass substrate may be either wet etching (wet etching) or dry etching (dry etching). Wet etching is preferable from the viewpoint of reducing the processing cost. The etchant used for wet etching may be anything as long as it can etch a glass substrate. Preferably, an acidic solution mainly containing hydrofluoric acid or a mixed acid containing at least one acid among sulfuric acid, nitric acid, hydrochloric acid, and silicic hydrofluoric acid can be used. The etchant used for dry etching is not particularly limited as long as it can etch a glass substrate. For example, a fluorine-based gas can be used.

  The resist material used in the etching process may be any material having resistance to an etchant used when etching glass using a resist pattern as a mask. Since glass is usually etched by wet etching of an aqueous solution containing hydrofluoric acid or dry etching of a fluorine-based gas, for example, a resist material having excellent resistance to hydrofluoric acid can be used. In addition, as a stripping solution for stripping the resist material from the glass substrate, an alkaline solution such as KOH or NaOH is preferably used. Note that the types of the resist material, the etchant, and the stripping solution can be appropriately selected according to the material of the glass substrate that is the material to be etched.

  Thus, after obtaining the glass substrate 1 by etching, heat energy that can soften the glass substrate surface is locally applied to the end surface of the glass substrate 1. Here, locally applying heat energy that can soften the glass substrate surface is not the entire glass substrate 1 but the top 14, the end surface 13 and the top of the main surface 11, and the end surface 13 and the main surface generated by etching. It means that processing is performed on a necessary area so that the top (ridge line) of 12 does not protrude. If such a treatment is performed on the entire surface of the glass substrate 1, the glass substrate is distorted or surface sagging occurs. Therefore, the purpose of the processing in a state in which such glass substrate distortion or surface sagging does not occur is intended. To do.

  As described above, the glass substrate obtained by locally applying thermal energy that can soften the glass substrate surface to the end surface 13 of the glass substrate 1, as shown in FIG. The top portion 14 ′ constituted by the surfaces 11 and 12 and the end face 13 ′ and the top portion 14 ″ constituted by the end face 13 ′ have end shapes in which roundness is formed. More specifically, the top portion 14 ′ is an edge where two layers are not cut from the surface in a sharp edge test according to UL-1439. Further, the top portion 14 ′ has a chamfered dimension from the start point of the curved surface on the main surfaces 11 and 12 to the end surface 13 ′ (Y), from the start point of the curved surface protruding outward on the end surface 13 ′ to the main surface. When the distance (X) up to 11 and 12 is expressed, it is preferable that the distance (X) and the distance (Y) are 10 μm to 100 μm, respectively.

  Moreover, when the thermal energy which can soften the glass base material surface with respect to the end surface of the glass base material 1 is applied locally, depending on the thermal energy conditions, as shown in FIG. As a result of the surface tension of 1, the raised portions 15 are formed on the main surfaces 11 and 12 adjacent to the end face, and the thickness of the glass substrate may increase. Since scratches and impacts are concentrated on the raised portion 15 of the main surface and breakage is likely to occur, the thickness t ′ of the glass substrate including the raised portion 15 and the thickness of the region not affected by thermal energy. The difference from t (t′−t) is preferably 50 μm or less. More preferably, it is 10 μm or less. The plate thicknesses t and t 'can be measured by, for example, a micrometer having a head having a spindle parallel section of 3.5 mm. t ′ is the maximum thickness of the glass substrate 1 on which the raised portion 15 is formed, and t is the maximum measured at a distance R that is far away from the position of the maximum thickness t ′ until there is no sudden thickness change. The plate thickness. For example, if the spindle parallel section φ3.5 mm, the distance R can be set to 5 mm.

  The thermal energy may be any energy that can soften the glass substrate surface, and energy generated from any one of a discharge source, a heating source, and a light source can be used. Examples of the treatment using these energies include heat treatment, electric discharge machining treatment, and light irradiation treatment.

  The heat treatment refers to a treatment in which heat treatment is performed on the end surface 13 of the glass substrate 1 using a burner that is a heat source. For example, as shown in FIG. 2A, the glass substrate 1 is placed on the plate 2 made of stainless steel or the like so that the end surface 13 of the glass substrate 1 extends from the plate 2. The glass substrate 1 shown in FIG. 2B is moved relatively (for example, 5 mm / second to 9 mm / second) by a glass substrate 1 and a burner (for example, a concentrated flame of butane gas φ10) 3 as a flame means. The X part of is heated. In the treatment in this case, first, the glass substrate 1 is placed on the plate 2, and then the plate 2 is heated to about 400 ° C. (in the range of 350 ° C. to annealing point temperature). Then, X part of the glass base material 1 is heated, moving the glass base material 1 and the burner 3 relatively, and the top part 14 formed in the end surface 13 is rounded by etching. Finally, the glass substrate 1 is cooled to room temperature in about 10 to 20 minutes. Here, stainless steel is used as the material of the plate 2, but heat-resistant alloy, graphite, ceramics, or the like may be used. Here, a butane gas burner is used, but an LNG (liquefied natural gas) burner, an LPG (liquefied petroleum gas) burner, an acetylene gas burner, an oxygen gas burner, or the like may be used.

  However, generally, the softening point temperature of glass is as high as 600 ° C. or higher, and when a locally heated portion to which heat energy is locally applied is exposed to rapid cooling, breakage occurs due to a difference in shrinkage from the non-locally heated portion. For this reason, this damage can be prevented by carrying out so-called preheating, in which the plate 2 is preliminarily heated to a temperature not lower than 250 ° C. and not higher than the annealing point.

  In addition, due to the heat treatment, a large thermal strain occurs at the boundary between the treated part and the non-treated part, and tensile stress is applied. In this state, there is a possibility that breakage easily occurs with a slight impact. . For this reason, it is preferable to perform the annealing process which relieves a thermal distortion with respect to the glass base material 1 after an electrical discharge machining process in the vicinity of a cooling point. As conditions for the annealing treatment, the annealing temperature is from + 10 ° C. to 1 minute to 30 minutes. A typical annealing temperature of aluminosilicate glass is, for example, 500 ° C.

  The electric discharge machining process is a process of applying thermal energy to the end surface 13 of the glass substrate 1 by arc discharge from a discharge source. Specifically, it refers to a process of applying thermal energy using a discharge phenomenon (a phenomenon in which insulation in air is broken by applying a high voltage between electrodes). For example, as shown in FIG. 3, a region including the end surface 13 of the glass substrate 1 placed on the plate 2 is disposed between two refractory metal rods 4 whose tips are sharply polished. A high voltage of about 1000 V is applied between the melting point metal rods 4. As a result, a discharge area called plume 5 is generated between the refractory metal rods 4, and the end face 13 of the glass substrate 1 in this discharge area is heated by thermal energy. At this time, the end surface 13 of the glass substrate 1 is heated while relatively moving the glass substrate 1 and the refractory metal rod 4, and the top portion 14 and the end surface 13 formed on the end surface 13 by etching and the main surface 11, Round 12 tops (ridges). In the electric discharge machining process, the high temperature region is limited to the plume 5 only, so that the glass base material is not distorted outside the plume 5 region, and no surface sagging occurs.

However, generally the softening point temperature of the glass is as high as 600 ° C. or higher, breakage due to the difference in contraction amount between the locally localized heating portion is exposed and the non-local heating portion quench application of heat energy arising. For this reason, this damage can be prevented by carrying out so-called preheating, in which the plate 2 is preliminarily heated to a temperature not lower than 250 ° C. and not higher than the annealing point. Furthermore, due to the electrical discharge machining treatment, a large thermal strain is generated at the boundary between the treated area and the non-treated area, and tensile stress is applied. In this state, there is a possibility that breakage easily occurs with a slight impact. is there. For this reason, it is preferable to anneal the glass substrate 1 after the electric discharge machining treatment in the vicinity of the cooling point. As conditions for the annealing treatment, the annealing temperature is from + 10 ° C. to 1 to 30 minutes. A typical annealing temperature of aluminosilicate glass is, for example, 500 ° C.

  The light irradiation process refers to a process in which the glass substrate 1 is heat-treated with respect to the end surface 13 of the glass substrate 1 using a laser beam or the like using a laser beam. The laser light may be light having a wavelength that can soften the glass. For example, a carbon dioxide laser or a YAG laser can be used as the light source.

  Moreover, volatilization of the ionic component in glass occurs by the heating by the said heat energy, and the composition of the outermost surface may fluctuate. In this case, since the density of the glass decreases due to volatilization of the ionic component in the glass, the strength at the end face 13 tends to be weaker than that in the untreated region. Therefore, after applying thermal energy locally to the glass substrate and performing an annealing treatment, the glass substrate 1 is subjected to chemical strengthening to generate a compressive stress, which is a tensile stress that cannot be removed by annealing. The relative reduction and the end face strength due to the density change can be compensated, and a sufficient strength as a glass substrate can be obtained. Here, chemical strengthening means strengthening by replacing the alkali metal ions constituting the glass with alkali metal ions having a size larger than that by ion exchange.

In addition, as ion exchange treatment conditions, a single salt of potassium nitrate (KNO ₃ ), a single salt of sodium nitrate (NaNO ₃ ), and a mixed salt obtained by mixing potassium nitrate and sodium nitrate at an arbitrary weight ratio may be used. The temperature may be selected in the range of 350 ° C. to 450 ° C. and the time in the range of 1 hour to 20 hours.

  Regarding the order of local heat treatment by thermal energy, annealing treatment and chemical strengthening treatment, compressive stress generated by chemical strengthening is thermally relaxed after local heat treatment and annealing treatment by thermal energy rather than chemical strengthening treatment. Therefore, it is preferable to perform a chemical strengthening treatment after the local heat treatment with heat energy and the annealing treatment.

  About the heat processing performed with respect to the end surface of the glass base material after an etching, as shown in FIG. 4, the area | region containing the end surface of the glass base material 1 is inserted in the recessed part of the heating block 6 of a cross-sectional substantially U shape. (Close to the heating block 6 at a distance of about 2 mm), by heating the heating block 6 (about 1000 ° C.), a heating atmosphere and a concentrated area of infrared radiation are created in the recess, and the end face of the glass substrate 1 is heated to the heating block 6 6 may be exposed to radiant heat (about 400 ° C.) to indirectly heat the end face. In this case, the heating block is made longer than the glass substrate 1, and the top portion 14 and the end surface 13 formed on the end surface 13 by etching after leaving the end portion of the glass substrate in the recess for about 2 to 10 seconds. And the top part (ridgeline) of the main surfaces 11 and 12 is rounded. Examples of the material of the heating block 6 that creates a heating atmosphere by heating with a laser or an infrared heater include silicon nitride.

  Such a glass substrate 1 has no top portion (ridge line) protruding from the top portion 14 and the end surface 13 and the main surfaces 11 and 12 and is rounded, so that it may be damaged during handling or transportation. Chipping is less likely to occur. In the glass substrate according to the present invention, after forming a resist pattern on the main surface of a plate-like glass substrate, the glass substrate is etched with an etchant capable of etching the glass substrate using the resist pattern as a mask. The end surface 13 ′ of the glass substrate 1 is made of a molten glass surface, and the surface roughness (arithmetic average roughness Ra) at the end surface 13 ′ is cut. It is 10 nm or less. Thus, since the glass substrate according to the present invention forms an outer shape by etching, the end face 13 'has a very high smoothness and is composed of a molten glass surface, which is formed by machining. It will be in a state without any microcracks that are always present on the end face, and exhibit high mechanical strength.

The mechanical strength of the glass substrate is preferably 5000 kgf / cm ² or more, more preferably 7000 kgf / cm ² or more, and most preferably 10000 kgf / cm ^{2 in} terms of three-point bending strength (three-point bending strength). The above is desirable.

  As the glass substrate 1, a glass body molded directly from a molten glass or a glass body molded to a certain thickness is cut out to a predetermined thickness, and the main surface is polished to a predetermined thickness. Things can be used. It is preferable to use what was directly molded into a sheet form from molten glass. This is because the main surface of the glass substrate molded directly from molten glass into a sheet is a hot-molded surface, and has a very high smoothness and a surface state without microcracks. Examples of a method for directly forming a sheet from molten glass include a downdraw method and a float method. Of these, the downdraw method is preferred. In addition to the effects such as high smoothness described above, when performing external processing by an etching process, using the resist pattern formed on both main surfaces of the glass substrate as a mask, when etching the glass substrate from both main surfaces, This is because etching can be performed uniformly from both main surfaces, so that the dimensional accuracy is good and the cross-sectional shape of the end face of the glass substrate is also good. The thickness of the glass substrate 1 is preferably 0.3 mm or greater and 1.3 mm or less.

Examples of the glass that can be formed into a glass plate by the downdraw method include aluminosilicate glass containing SiO ₂ , Al ₂ O ₃ , Li ₂ O and / or Na ₂ O. In particular, the aluminosilicate glass is composed of 62 wt% to 75 wt% SiO ₂ , 5 wt% to 15 wt% Al ₂ O ₃ , 4 wt% to 10 wt% Li ₂ O, 4 wt% to 12 wt%. of _Na 2 O, and 5.5 wt% preferably contains ZrO ₂ of 15 wt%, _further, the weight ratio of Na 2 O / ZrO ₂ is 0.5 to 2.0, further Al ₂ O ₃ / weight ratio of ZrO ₂ it is preferred that the composition is 0.4 to 2.5.

SiO ₂ is a main component that forms a glass skeleton. Mobile devices, especially cover glasses for mobile phones, are used in extremely harsh environments such as touching human skin and contact with water and rainwater. It is necessary to have sex. The ratio of SiO ₂ is preferably 62% by weight to 75% by weight in consideration of the chemical durability and the melting temperature.

Al ₂ O ₃ is contained in order to improve the ion exchange performance on the glass surface. The proportion of Al ₂ O ₃ is preferably 5% by weight to 15% by weight in view of chemical durability and devitrification resistance.

Li ₂ O is an essential component for chemically strengthening glass by being ion-exchanged mainly with Na ions in the ion-exchange treatment bath at the glass surface layer. The ratio of Li ₂ O is preferably 4% by weight to 10% by weight in consideration of ion exchange performance, devitrification resistance and chemical durability.

Na ₂ O is an essential component when the glass is chemically strengthened by ion exchange with K ions in the ion exchange treatment bath at the glass surface layer. The ratio of Na ₂ O is preferably 4% by weight to 12% by weight in consideration of the mechanical strength, devitrification resistance, and chemical durability.

ZrO ₂ has the effect of increasing the mechanical strength. The ratio of ZrO ₂ is preferably 5.5% by weight to 15% by weight in consideration of chemical durability and stable production of homogeneous glass.

  Note that other multicomponent glass may be used instead of aluminosilicate glass. Further, crystallized glass may be used as long as the transparency necessary for the glass substrate is ensured.

  Next, taking as an example a cover glass for a mobile phone used for protecting a display screen of a mobile phone as an example of a glass substrate, an example performed to clarify the effect of the present invention will be described.

Example 1
First, SiO ₂ is 63.5% by weight, Al ₂ O ₃ is 8.2% by weight, Li ₂ O is 8.0% by weight, Na ₂ O is 10.4% by weight, and ZrO ₂ is 11.9% by weight. The aluminosilicate glass contained was formed into a plate-like glass substrate (sheet-like glass) having a plate thickness of 0.5 mm by the downdraw method. The surface roughness (arithmetic mean roughness Ra) of the main surface of the sheet-like glass formed by this downdraw method was 0.2 nm when examined by an atomic force microscope.

Next, a negative type acid-resistant acid resist was coated on both main surfaces of the sheet glass with a thickness of 32 μm, and this acid-resistant resist was baked (prebaked) at 100 ° C. for 30 minutes. Next, the hydrofluoric acid resistant resist is exposed to energy of 300 mJ / cm ² from both sides through a photomask having a predetermined pattern, and the hydrofluoric acid resistant resist after the exposure is used with a developer (Na ₂ CO ₃ solution). Development was performed to form a resist pattern in which the hydrofluoric acid resistant resist remained in a region other than the region to be etched on the sheet-like glass. Further, the sheet-like glass on which the resist pattern was formed was baked (post-baked) at 250 ° C. for 30 minutes.

  Next, using a mixed acid aqueous solution (40 ° C.) of hydrofluoric acid (15% by weight) and sulfuric acid (24% by weight) as an etchant, using the resist pattern as a mask, sheet-like glass is etched from both main surface sides. 1-etching was performed to cut out a predetermined shape (square shape with chamfered corners (size: 50 mm × 40 mm)). Thereafter, the hydrofluoric acid resistant resist remaining on the glass was swollen using a NaOH solution, peeled off from the glass, and rinsed.

Next, using the apparatus shown in FIG. 2, flame treatment was performed on the end surface of the glass substrate after etching. Here, the plate on which the glass substrate was placed was fixed, the plate was preheated to 430 ° C., and the flame treatment was performed by moving the burner at a speed of 4.2 mm / sec. Immersion at 380 ° C. for 2 hours in a molten salt in which the ratio of sodium nitrate (NaNO ₃ ) and potassium nitrate (KNO ₃ ) (NaNO ₃ : KNO ₃ ) was mixed at a weight ratio of 4: 6 with respect to this glass substrate Then, the chemical strengthening was performed by ion exchange treatment. In this manner, the cover glass for a mobile phone of Example 1 was produced.

  About the obtained mobile phone cover glass, the chamfer dimension (average value of distance (X) and distance (Y)) shown in FIG. 1B and the value of t′-t (thickness) shown in FIG. Change). The results are shown in Table 1 below. Moreover, the bending strength measurement and the sharp edge test were performed about the obtained cover glass for mobile phones. The results are shown in Table 1 below.

As shown in FIG. 5A, the bending strength measurement is performed by placing a glass substrate 1 (mobile phone cover glass) on two supports (fulcrum points) 25 and 26 arranged at a fixed distance. A load was applied to one central point between the bodies 25 and 26 via a load body 27, and the maximum bending stress when the fracture occurred was measured. Since the three-point bending strength depends on the distance between the fulcrums, the substrate width, and the substrate thickness, normalization was performed using the following equation.
σ = (3PL) / (2 wt ² )
Here, σ indicates a three-point bending strength (kgf / cm ² ), P indicates a maximum load (kgf) when the glass substrate (cover glass for a mobile phone) breaks, L indicates a support 25, 26 indicates a distance (cm) between 26, w indicates a glass substrate (mobile phone cover glass) width (cm) as shown in FIG. 5 (b), and t indicates a glass substrate as shown in FIG. 5 (b). The thickness (cm) of the material (cover glass for mobile phone) is shown.

  The sharp edge test was conducted by using a sharp edge tester SET-50 manufactured by Excel Corporation and a tape kit TC-3 by a method based on UL-1439 (determination of the sharpness of the edge of the device). As shown in FIG. 6, the tape kit TC-3 is a kit having three layers of tapes 31 to 33 on the head 34 having a diameter of 12.7 mm and assuming the softness of fingers. The tester SET-50 is a tool for pressing it against the edge to be measured with a constant load. Specifically, the tape kit TC-3 attached to the sharp edge tester SET-50 is measured with a constant load (arrow direction in FIG. 6: 6.67N) of the edge to be measured (glass substrate (cover glass for mobile phone)). The edge part). While maintaining the load, the tape kit TC-3 is moved back and forth 100 mm (one way 50 mm) along the edge portion.

(Example 2)
The mobile phone of Example 2 was the same as Example 1 except that the preheating temperature in the flame treatment was 380 ° C., the moving speed was 7.2 mm / second, and the annealing treatment was performed at 510 ° C. for 1 minute after the flame treatment. A cover glass was obtained. The obtained cover glass for a mobile phone was examined for chamfer dimensions and thickness variation, and subjected to bending strength measurement and sharp edge test. The results are also shown in Table 1 below.

(Example 3)
A mobile phone cover of Example 3 in the same manner as in Example 1 except that laser irradiation treatment using a CO ₂ laser is performed instead of flame treatment, the preheating temperature is set to 450 ° C., and the moving speed is set to 40 mm / second. Glass was obtained. Note that after the laser irradiation treatment, annealing treatment was performed at 510 ° C. for 1 minute. About the obtained cover glass for mobile phones, the chamfer dimension and the thickness change amount were examined, and the bending strength measurement and the sharp edge test were performed. The results are also shown in Table 1 below.

Example 4
Indirect heating using the apparatus of FIG. 4 is performed instead of the flame treatment, the preheating temperature is 400 ° C., the heating block is made longer than the glass substrate 1, the temperature of the heating block is 1000 ° C., and the glass substrate A cover glass for a mobile phone of Example 4 was obtained in the same manner as in Example 1 except that the end part was left in the recess for 5 seconds. In addition, after the indirect heating by a heating block, annealing treatment was performed at 510 ° C. for 1 minute. The obtained cover glass for a mobile phone was examined for chamfer dimensions and thickness variation, and subjected to bending strength measurement and sharp edge test. The results are also shown in Table 1 below.

(Example 5)
The electric discharge machining process using the apparatus shown in FIG. 3 is performed instead of the flame process, the preheating temperature is set to 300 ° C., and the moving speed is set to 2.0 mm / sec. A cover glass for a mobile phone was obtained. Note that after the electric discharge machining treatment, annealing treatment was performed at 510 ° C. for 1 minute. About the obtained cover glass for mobile phones, the chamfer dimension and the thickness change amount were examined, and the bending strength measurement and the sharp edge test were performed. The results are also shown in Table 1 below.

(Comparative example)
The glass substrate after etching in Example 1 was used as a cover glass for a mobile phone of a comparative example. About the obtained cover glass for mobile phones, the chamfering amount was examined, and the bending strength measurement and the sharp edge test were performed. The results are also shown in Table 1 below.

As can be seen from Table 1, the cover glass for mobile phones of Examples 1 to 5 has a chamfered dimension of 10 μm or more, so that the top is not sharp but rounded, Since the height of the portion is small, it is possible to suppress the concentration of scratches and impacts on the raised portion, and the three-point bending strength (three-point bending strength) is 5000 kgf / cm ² or more and the mechanical strength is high. . This is because the crack at the sharp apex that occurs during handling by heat treatment using thermal energy such as flame machining, laser machining, electric discharge machining, etc. is smoothed, and the top is rounded, so a new crack is created during handling. Since there is nothing that becomes difficult to occur and becomes the starting point of cleavage, and a compressive stress layer is formed on the surface by chemical strengthening in a state where the end is smooth, when the three-point bending strength (three-point bending strength) becomes high Conceivable. In particular, in contrast to Example 1 in which flame processing was performed, in Example 2 in which annealing treatment for relaxing thermal strain was performed after flame processing, mechanical strength was improved, and three-point bending strength (three-point bending strength) And a very high mechanical strength of 7000 kgf / cm ² was obtained. In addition, as in Examples 3 to 5, the three-point bending strength (three-point bending strength) is also obtained when annealing is performed to reduce thermal strain after laser irradiation processing, indirect heating processing, and electric discharge machining processing. The mechanical strength was very high at 7000 kgf / cm ² or more. In addition, because of the rounded shape at the top, all the sharp edge tests passed.

On the other hand, the cover glass for mobile phones of the comparative example had a sharp top and failed the sharp edge test. Also, the three-point bending strength (three-point bending strength) was far below 5000 kgf / cm ² . This is because the top portion is sharp because there is no heat treatment using thermal energy such as flame processing, and cracks are generated at the sharp apex during handling, and there are those that become the starting point of cleavage. The point bending strength is considered to be low.

  The present invention is not limited to the above embodiment, and can be implemented with appropriate modifications. For example, the materials, processing procedures, and the like in the above-described embodiment are merely examples, and various modifications can be made within the scope of the effects of the present invention. In addition, various modifications can be made without departing from the scope of the object of the present invention.

(A)-(c) is a figure which shows a part of glass base material which concerns on embodiment of this invention. (A), (b) is a figure which shows the flame treatment apparatus used with the manufacturing method of the glass base material concerning embodiment of this invention. It is a figure which shows the discharge treatment apparatus used with the manufacturing method of the glass base material which concerns on embodiment of this invention. It is a figure which shows the indirect heat processing apparatus used with the manufacturing method of the glass base material which concerns on embodiment of this invention. It is a figure for demonstrating a bending strength measuring apparatus. It is a figure for demonstrating a sharp edge test. It is a figure for demonstrating the edge of a glass base material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass base material 2 Plate 3 Burner 4 High melting-point metal rod 5 Plume 6 Heating block 11,12 Main surface 13 End surface 14 Top part 25,26 Support body 27 Load body 31-33 Tape 34 Head

Claims (4)

  Using the resist pattern formed on one and the other main surfaces of the plate-like glass substrate as a mask, the glass substrate is etched from each of the one and the other main surfaces of the glass substrate with an etchant capable of etching the glass substrate. Etching to obtain a glass substrate by cutting into a desired shape, and heat that can soften the surface of the glass substrate relative to the top of the end surface of the glass substrate that protrudes outward in the surface direction of the main surface A step of locally applying energy, and a step of chemically strengthening the glass substrate surface by ion exchange treatment after locally applying thermal energy to the end face of the glass substrate. The manufacturing method of the glass base material of the cover glass for portable devices.   After the thermal energy is locally applied to the end surface of the glass base material and before chemical strengthening, the thermal energy is applied to the glass base material to which the thermal energy is locally applied to the end surface of the glass base material. The manufacturing method of the glass substrate of the cover glass for portable devices of Claim 1 which performs the annealing process which relieve | moderates the thermal strain produced by adding.   The thermal energy is energy generated from any one of a discharge source, a heating source, and a light source, and is locally applied to the end surface of the glass substrate, and is any one of heat treatment, electric discharge machining treatment, and light irradiation treatment. The manufacturing method of the glass base material of the cover glass for portable devices of Claim 1 or Claim 2 characterized by the above-mentioned.   The said heat processing makes a high temperature member approach the end surface of the said glass base material, and heat-processes by radiant heat, The manufacturing method of the glass substrate of the cover glass for portable devices of Claim 3 characterized by the above-mentioned.

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