JP2022143262A - Tempered glass plate and production method of tempered glass plate - Google Patents

Abstract

To materialize a tempered glass plate having thin thickness and small warpage.SOLUTION: A production method of a tempered glass plate includes a strengthening step of obtaining a tempered glass plate 1 of which both the front and back surfaces have each a compressive stress layer 5, 6 formed by chemically strengthening a flexible glass plate. The tempered glass plate 1 has a warped portion 4 warped in such a manner that one of the front and back surfaces 2, 3 is convex. The production method further includes a removing step of reducing a warp by removing a surface layer of the compressive stress layer 5 on the surface 2 side (convex face side) in the warped portion 4.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present disclosure relates to tempered glass sheets and methods for manufacturing tempered glass sheets.

2. Description of the Related Art In recent years, portable electronic devices such as smartphones and tablet PCs are being promoted to have larger screens. However, if the screen is enlarged, the device as a whole will become larger and the portability will deteriorate. Therefore, in order to achieve both a large screen and good portability, a foldable device has been proposed.

As a cover glass for a foldable device, for example, an ultra-thin tempered glass plate (with a thickness of 100 μm or less as an example) disclosed in Patent Document 1 is employed. The tempered glass plate is manufactured by chemically strengthening a flexible, ultra-thin glass plate.

JP 2018-188360 A

By the way, when a glass plate is chemically strengthened as described above, the thinner the glass plate to be strengthened, the more likely the tempered glass plate is to warp greatly (warp in which one of the front and back surfaces is convex). there were. In view of such circumstances, a technical problem to be solved is to realize a tempered glass sheet having a small thickness and a small warp.

As a result of intensive research, the inventors have found the following reasons as factors in which the thinner the glass sheet to be tempered, the more likely the tempered glass sheet is to warp greatly. That is, during chemical strengthening, there may be a difference in the degree of strengthening between the front side and the back side of the glass plate (hereinafter referred to as "difference in strengthening between the front and back sides"). Examples of the cause of the difference in strength between the front and back surfaces include uneven adhesion of the molten salt (strengthening liquid) used for chemical strengthening when the glass is pulled up, and uneven temperature distribution during strengthening. As the thickness of the glass sheet to be strengthened decreases, the bending rigidity of the glass sheet decreases. Therefore, the tempered glass sheet tends to warp greatly due to the difference in strengthening between the front and back surfaces.

Furthermore, as a result of intensive research by the inventor, (1) the difference in strengthening between the front and back is the difference in the depth of the compressive stress layers formed on both the front and back sides of the glass plate due to chemical strengthening, or the difference in the maximum compressive stress value , and the compressive stress layer is deeper or the maximum compressive stress value is larger on the side with a large degree of strengthening between the front and back, (2) the convex side of the warp that occurred on the side with a large degree of strengthening between the front and back I came to know that

Based on the above findings, a method for manufacturing a tempered glass sheet for solving the above problems is a tempered glass sheet in which a compressive stress layer is formed on each of the front and back sides by chemically strengthening a flexible glass sheet. wherein the tempered glass sheet includes a warped portion warped so that one of the front and back surfaces is convex, and the surface layer of the compressive stress layer on the convex side of the warped portion is removed. and a removing step of reducing the warpage.

In this method, the surface layer portion of the compressive stress layer on the convex side of the warped portion is removed along with the execution of the removing step. In other words, the depth of the compressive stress layer on the side with the greater degree of strengthening between the front and back or the surface maximum compressive stress value is reduced. As a result, the difference in the depth of the compressive stress layer or the maximum compressive stress value between the front and back surfaces can be reduced, and thus the difference in strengthening between the front and back surfaces can be reduced. As a result, even a tempered glass sheet having a small thickness and a small bending rigidity can be reduced in warpage. As described above, according to the present method, a tempered glass sheet having a small thickness and a small warp can be obtained.

In the above method, the surface layer portion of the compressive stress layer corresponding to the partial area may be removed by etching or polishing only the partial area on the convex surface of the warped portion.

In this way, etching or polishing only needs to be performed on a part of the convex surface instead of the entire area, so that the removal process can be completed more quickly. Moreover, the cost required for the removal process can also be suppressed.

In the above method, etching is preferably performed while the tempered glass sheet is suspended and supported in a vertical position.

In this way, by suspending and supporting the tempered glass plate in a vertical position, unlike the case where the tempered glass plate is placed on a horizontal surface in a flat position, the shape of the warp is deformed from the original shape due to the influence of gravity. You can eliminate the fear of doing so. In other words, it becomes possible to perform the removal step in a state in which the original shape of the warp is exposed. This is advantageous in accurately performing the removal process.

In the above method, it is preferable to etch a region including the vertex of the convex surface in the warped portion.

The apex of the convex surface in the warped portion has a strong tendency to correspond to the portion where the difference in strength between the front and back surfaces is maximized. Therefore, by etching the region including the apex of the convex surface, the warpage can be effectively reduced.

In the above method, the tempered glass sheet includes a plurality of warped portions, and among the plurality of warped portions, the tempered glass sheet includes a warped portion having a convex surface and a warped portion having a convex back surface. It may be

In this case, along with the execution of the removing step, the warp is reduced in both the warped portion with the convex surface and the warped portion with the convex back surface. This makes it possible to reduce the overall warpage of the tempered glass sheet.

In the above method, etching may be performed by using an etching member having a flat surface capable of holding an etchant, and bringing the flat surface of the etching member into contact with a partial region on the convex surface of the warped portion. preferable.

In this way, etching can be performed simply and reliably on a partial area of the convex surface instead of on the entire area.

In the above method, the area of the flat surface of the etching member is preferably equal to or greater than the area of the tempered glass plate.

By doing so, it is possible to reliably perform simultaneous etching on the respective areas to be etched included in the tempered glass plate, so that the removal process can be completed more quickly.

In the above method, the etching member is a sponge-like member impregnated with an etchant, and the etchant preferably contains HF or a mixed acid containing HF.

In this way, since the sponge-like member is impregnated with the etchant, it is possible to save the trouble of supplying the etchant to the etching member each time the removal step is performed. Moreover, etching can be performed efficiently by including HF or a mixed acid containing HF in the etchant.

In the above method, when the entire tempered glass sheet consists of a single warped portion, the surface layer portion of the compressive stress layer corresponding to the entire region is etched or polished by etching or polishing the entire region of the convex surface of the warped portion. may be removed.

In this case, under the condition that one of the front and back surfaces of the entire tempered glass sheet is convex, etching or polishing may be performed on the entire area of the convex surface, so it is possible to simplify the treatment in the removal process. becomes.

In the above method, when the maximum depth of the compressive stress layer on the convex side before the removing step is DOC, and the thickness of the surface layer portion of the compressive stress layer removed in the removing step is Δt, Δt≦0.8×DOC. is preferably satisfied.

By doing so, it is possible to enjoy the effect of reducing the warpage due to the removal process without unduly losing the compressive stress layer.

In the above method, it is preferable that the tempered glass sheet has a thickness of 100 μm or less before the removal step, and a warpage amount of 1 mm or less after the removal step.

As described above, the thinner the tempered glass sheet, the more likely it is to warp. Therefore, if the removal process is performed on an ultra-thin tempered glass sheet having a thickness of 100 μm or less before the removal process, the effect can be favorably received. If the amount of warpage of the tempered glass sheet after the removing step is 1 mm or less, it is possible to make the tempered glass sheet suitable as a cover glass of a foldable device or the like.

Furthermore, a tempered glass plate for solving the above problems is a tempered glass plate having a thickness of 100 μm or less, including a warped portion in which one of the front and back surfaces is convex, and on the convex surface of the warped portion At least a part of the tempered glass plate has a treated region that is etched, and the tempered glass plate has a warpage amount of 1 mm or less.

Although the tempered glass sheet is an ultra-thin tempered glass sheet having a thickness of 100 μm or less, the amount of warpage is suppressed to 1 mm or less. Therefore, it can be suitably used as a cover glass of a foldable device or the like.

According to the method for manufacturing a tempered glass sheet according to the present disclosure, it is possible to obtain a tempered glass sheet having a small thickness and little warpage. In addition, the tempered glass sheet according to the present disclosure is a tempered glass sheet with small warp even if the thickness is thin.

FIG. 4 is a side view schematically showing a removing step in the method for manufacturing a tempered glass sheet. FIG. 4 is a side view schematically showing a tempered glass plate after a removal step; FIG. 4 is a side view schematically showing a removing step in the method for manufacturing a tempered glass sheet. FIG. 4 is a side view schematically showing a removing step in the method for manufacturing a tempered glass sheet.

Hereinafter, a method for manufacturing a tempered glass sheet and a tempered glass sheet according to embodiments will be described with reference to the accompanying drawings.

<First embodiment>
A method for manufacturing a tempered glass sheet according to the first embodiment includes a tempering step and a removing step.

[Strengthening process]
In the strengthening step, a flexible glass sheet is chemically strengthened to obtain a tempered glass sheet having compressive stress layers (layers to which compressive stress acts) formed on the front side and the back side, respectively. When performing the strengthening step, first, a glass plate for chemical strengthening is prepared.

A glass plate is obtained by cutting and processing a glass ribbon formed by an overflow down-draw method. Although the type of glass plate is not limited, the glass plate of the present embodiment is alkali aluminosilicate glass suitable for chemical strengthening. Further, the glass plate has a composition capable of obtaining a particularly high compressive stress value among alkali aluminosilicate glasses, and further has a composition capable of realizing a high liquidus viscosity to enable molding by the overflow down-draw method. In the present embodiment, the overflow downdraw method is used to obtain the glass plate, but in addition to this, the slot downdraw method, the float method, the redraw method, or the like may be used to obtain the glass plate.

It is preferable to subject the end surface of the glass plate to chamfering and strength improvement by polishing, heat treatment, etching, or the like. The front and back surfaces of the glass plate may be polished. may be left unpolished without being polished. Note that when the glass plate is formed by the overflow down-draw method and is not polished, the front and back surfaces of the glass plate are fire-polished surfaces. The glass plate may be further subjected to a slimming treatment to reduce the thickness by etching.

The glass plate has, as an example of glass composition, SiO ₂ 50 to 80%, Al ₂ O ₃ 5 to 25%, B ₂ O ₃ 0 to 35%, Li ₂ O 0 to 20%, and Na ₂ O in mol%. 1-20%, Li ₂ O+Na ₂ O 1-20%, K ₂ O 0-10%. It should be noted that each component with a range including 0% indicates that it is an optional component. That is, it does not have to contain the said component. Further, the glass plate may contain the following components in addition to the above components. In mole %, MgO 0.1-12%, CaO 0-10%, SrO 0-5%, BaO 0-5%, ZnO 0-6%, ZrO ₂ 0.001-10%, P ₂ O ₅ 0 ~10%. In addition, as a clarifier, one or _more selected from the group of _{As2O3 , Sb2O3 ,} SnO2, F, Cl, SO3 ₍ preferably the group of _{SnO2 ,} Cl, SO3) may contain 0 to 3%. In addition, it is preferable that substantially no As ₂ O ₃ , F, PbO, and Bi ₂ O ₃ are contained in consideration of the environment.

The shape of the glass plate is not particularly limited, but in this embodiment, it has a rectangular shape with long sides and short sides. The length of the long side of the glass plate is, for example, 50 mm or more and 500 mm or less, preferably 60 mm or more and 450 mm or less, more preferably 65 mm or more and 400 mm or less, still more preferably 70 mm or more and 300 mm or less, 75 mm or more and 200 mm or less, 80 mm or more and 160 mm or less. be. The length of the short side of the glass plate is, for example, 40 mm or more and 400 mm or less, preferably 45 mm or more and 350 mm or less, more preferably 50 mm or more and 300 mm or less, still more preferably 55 mm or more and 120 mm or less, and 60 mm or more and 80 mm or less.

The glass plate has a thickness that can impart flexibility, and in the present embodiment, the maximum thickness of the glass plate is, for example, 100 µm or less, preferably 5 µm or more and 95 µm or less, and more preferably 10 µm or more. It is 85 μm or less, more preferably 15 μm or more and 75 μm or less. For further thinning, the thickness of the glass plate may be 65 μm or less, or 55 μm or less. On the other hand, the lower limit of the thickness of the glass plate is preferably 20 μm or more and 25 μm or more. If the glass plate is made too thin, it becomes difficult to ensure the strength, and if the glass plate is made too thin, it becomes difficult to increase the compressive stress value by strengthening, and there is a risk that the flexibility may be impaired. In the present embodiment, the thickness of the glass plate is preferably constant, and the thickness deviation is preferably within 3 μm.

Here, as an example, the glass plate in the present embodiment is a non-film-formed glass plate on which film-forming treatment has not been performed. That is, the case where the front and back surfaces are glass plates is exemplified. In addition, the present invention can also be applied to a film-formed glass plate on which a film-forming process has been performed.

Next, the glass plate prepared as described above is chemically strengthened by ion exchange treatment. Specifically, the glass plate is immersed in a molten salt (strengthening liquid) for ion exchange treatment.

Molten salts are salts containing components that can be ion-exchanged with components in the glass sheet, typically alkali nitrates. Alkaline nitrates include NaNO ₃ , KNO ₃ , LiNO ₃ and the like, and each of these can be used alone (at 100% by mass), or a mixture of a plurality of types can be used, typically KNO ₃ 100 % by mass. The mixing ratio when a plurality of types of _{alkali nitrates are} mixed may be determined _arbitrarily . ~70% _, or ratios such as 50-70% _NaNO3 and 30-50% KNO3.

Conditions such as the temperature and immersion time of the molten salt in the ion exchange treatment may be set according to the composition and the like within the range where desired stress characteristics can be obtained. The temperature of the molten salt is, for example, 350-500°C, preferably 355-470°C, 360-450°C, 365-430°C and 370-410°C. The immersion time is, for example, 3 minutes to 300 minutes, preferably 5 minutes to 120 minutes, more preferably 7 minutes to 100 minutes.

A tempered glass sheet is obtained through the ion exchange treatment described above. It is preferable to wash and dry the tempered glass plate after the ion exchange treatment. Note that the ion exchange treatment is not limited to one time, and may be performed multiple times.

The maximum depth DOC of the compressive stress layer of the tempered glass plate is 15.0 μm or less, preferably 0.5 μm or more and 12.0 μm or less, preferably 1.0 μm or more and 10.0 μm or less, preferably 1.0 μm. 8.5 μm or less, more preferably 2.0 μm or more and 8.0 μm or less, more preferably 2.5 μm or more and 7.5 μm or less, and 2.5 μm or more and 5.5 μm or less. As a result of various investigations by the inventors regarding the compressive stress value and the threshold value of the maximum depth of the compressive stress layer that does not cause a dangerous fracture mode when the tempered glass plate is broken, the maximum depth of the compressive stress layer is It has been found that it is effective to set the thickness to 9.0 μm or less. By doing so, it is possible to ensure safety while having sufficient strength against bending. The DOC in the present invention is the depth at which the stress in the tempered glass plate changes from compressive stress to tensile stress, and is the depth at which the stress becomes zero.

The maximum compressive stress CS in the compressive stress layer of the tempered glass plate is, for example, 520 MPa or more and 2000 MPa or less, preferably 650 MPa or more and 1800 MPa or less, more preferably 700 MPa or more and 1700 MPa or less. By setting the maximum compressive stress CS in such a range, high bending strength can be obtained. In order to further improve the bending strength, the maximum compressive stress CS can be more preferably 760 MPa or more and 1600 MPa or less, and still more preferably 820 MPa or more and 1550 MPa or less. On the other hand, when the suppression of pulverization at breakage is emphasized and the suppression of the maximum tensile stress CT is prioritized, the upper limit of the maximum compressive stress CS can be limited to 1000 MPa or less, 900 MPa or less, 800 MPa or less, or 740 MPa or less.

[Removal step]
After the tempering process is completed, as shown in FIG. 1, the tempered glass sheet 1 obtained in the tempering process is removed.

The tempered glass plate 1 obtained in the tempering process includes a warped portion 4 in which one of the front and back surfaces 2 and 3 is convex. In addition, the case where the surface 2 is convex is illustrated here. That is, the surface 2 side is the side with a large degree of strengthening between the front and back surfaces. In this embodiment, the entire tempered glass plate 1 consists of a single warped portion 4 . That is, only the front surface 2 is convex in the entire tempered glass plate 1 (the rear surface 3 does not have a convex portion). Compressive stress layers 5 and 6 are formed on the front surface 2 side and the rear surface 3 side of the tempered glass plate 1, respectively. The compressive stress layer 5 on the side of the front surface 2, which is the side with a large degree of strengthening, is deeper on average than the compressive stress layer 6 on the side of the back surface 3, which is the side with a small degree of strengthening. The cross-hatched portions in FIG. 1 are the portions where the compressive stress layers including the compressive stress layers 5 and 6 on the front and back sides of the tempered glass plate 1 are formed.

The warp of the tempered glass plate 1 (warp portion 4) may occur along either one of the long side direction and the short side direction of the tempered glass plate 1, or may occur along both directions. or along a direction that intersects both directions (eg, diagonally). Here, when the tempered glass plate 1 is placed flat on a horizontal support surface provided on a surface plate (placed with the convex surface 2 in contact with the support surface), the tempered glass The amount of warpage is defined as the dimension by which the edge of the plate 1 rises from the supporting surface. In this case, the amount of warp generated in the tempered glass sheet 1 having a thickness of 100 μm or less is, for example, 5 mm to 15 mm before the removal step is performed.

In the removing step, warpage is reduced by removing the surface layer portion of the compressive stress layer 5 on the surface 2 side (convex side) of the tempered glass plate 1 . Specifically, only a partial region on the surface 2 of the tempered glass plate 1 is etched to remove the surface layer portion of the compressive stress layer 5 corresponding to the partial region. That is, the depth of the compressive stress layer 5 on the side with the greater degree of reinforcement is reduced between the front and back sides, and the difference between the depths of both the compressive stress layers 5 and 6 is reduced. In the following description, the region to be etched in the tempered glass plate 1 is referred to as "etching target region". Here, the area of the etching target region is preferably 20% or more, more preferably 30% or more, still more preferably 40% or more, and most preferably 50% or more of the area of the tempered glass plate 1. . Also, the area of the etching target region is less than 100%, preferably 90% or less of the area of the tempered glass plate 1 .

The etching target region is a region including the apex of the surface 2 of the tempered glass sheet 1, that is, the portion that protrudes most in the thickness direction of the tempered glass sheet 1 on the convex surface. The apex of the front surface 2 tends to correspond to the portion where the front-back strengthening difference (the difference in the degree of strengthening between the front surface 2 side and the back surface 3 side) of the tempered glass plate 1 is the largest. In this embodiment, the maximum compressive stress CS is generated at the vertices of the surface 2 before execution of the removal step. In addition, when the maximum compressive stress CS is generated at a location other than the vertex on the surface 2, the area including the location may be set as the etching target area.

When etching the area to be etched, the tempered glass plate 1 is vertically suspended and supported. In order to suspend and support the tempered glass sheet 1, for example, the upper region of the rear surface 3 of the tempered glass sheet 1 in a vertical position may be held by a holding member (suction pad or the like). Further, the upper side portion of the tempered glass plate 1 in the vertical posture may be gripped by a gripping member (such as a chuck).

Furthermore, when etching the etching target region, an etching member 8 having a flat surface 7 capable of holding an etchant (details of which will be described later) is used. Specifically, the etching is performed by bringing the etching target region and the flat surface 7 of the etching member 8 into contact with each other. In this embodiment, the area to be etched is etched while partially flattening the surface 2 of the tempered glass plate 1 so as to follow the flat surface 7 of the etching member 8 as the two come into contact with each other. At this time, the area on the surface 2 of the tempered glass plate 1 excluding the area to be etched is in a state of floating above the flat surface 7 of the etching member 8 .

Details of the etching member 8 will now be described. The etching member 8 has a plate-like outer shape. The flat surface 7 of the etching member 8 is substantially perpendicular to the horizontal plane. The area of the flat surface 7 of the etching member 8 is equal to or larger than the area of the tempered glass plate 1 , and in the present embodiment, the area of the flat surface 7 is larger than the area of the tempered glass plate 1 . The etching member 8 is a sponge-like member impregnated with an etching liquid, and is a PVA sponge in this embodiment. A member other than a sponge-like member may be used as the etching member 8 as long as the etching liquid can be retained on the flat surface 7 . However, it is preferable to use one whose flat surface 7 is difficult to deform. For example, as the etching member 8, it is possible to use a polyurethane sponge or the like.

In the present embodiment, while the surface 2 of the tempered glass plate 1 is partially flattened so as to follow the flat surface 7 of the etching member 8, the etching target region is etched, but this is not the only option. . As the area to be etched and the flat surface 7 of the etching member 8 come into contact with each other, the flat surface 7 of the etching member 8 is deformed into a concavely curved surface so as to follow the warpage of the tempered glass plate 1 (curvature of the surface 2). However, etching may be applied to the area to be etched.

As the etchant, an acidic or alkaline liquid capable of etching glass can be used. In this embodiment, an acidic etchant is used. As an acidic etching solution, for example, an aqueous solution containing HF can be used. When an aqueous solution containing HF is used, the etching rate for glass is high, and etching can be performed efficiently.

The aqueous solution containing HF is, for example, an aqueous solution containing only HF or a combination of HF and HCl, HF and HNO ₃ , HF and H ₂ SO ₄ , or HF and NH ₄ F. HF, HCL, HNO ₃ , H ₂ SO ₄ , NH ₄ F, the concentration of each compound is preferably 0.1 to 30 mol/L. _In etching using an aqueous solution containing HF _, a fluoride containing a glass component is produced as a by _- product, which may cause a decrease in the etching rate or cause defects. By using a mixed acid with other acids such as , the by-product can be decomposed to suppress a decrease in productivity. When etching is performed using an acidic etchant, the temperature of the etchant is, for example, 10° C. to 30° C., and the treatment time is, for example, preferably 0.1 to 60 minutes, preferably 0.5 to 60 minutes. 30 minutes is more preferable, and 1 to 10 minutes is even more preferable.

Here, in the present embodiment, the maximum depth of the compressive stress layer 5 on the surface 2 side before the removal step is performed is DOC, and the thickness of the surface layer portion of the compressive stress layer 5 to be removed in the removal step (that is, the removal amount ) is Δt, the removing process is performed so as to satisfy Δt≦0.8×DOC. In addition, preferably Δt≦0.85×DOC, more preferably Δt≦0.9×DOC, still more preferably Δt≦0.95×DOC, and most preferably Δt≦0.97×DOC in the removal step to run. As a more specific example, Δt is 0.01 to 2 μm, preferably 0.03 to 1.5 μm, more preferably 0.05 to 1.2 μm, still more preferably 0.07 to 1 μm. By setting the thickness of the surface layer portion of the removed compressive stress layer 5 within such a range, the amount of variation in the maximum compressive stress CS and the maximum depth DOC of the compressive stress layer before and after the removal process can be minimized. , making it easier to control.

The numerical values such as the maximum compressive stress CS, the maximum tensile stress CT, and the maximum depth DOC of the compressive stress layer are obtained by measuring the stress distribution of the glass with a measuring device such as FSM-6000 or SLP-1000 manufactured by Orihara Seisakusho. can be derived from

Here, in this embodiment, when removing the surface layer portion of the compressive stress layer 5 in the removing step, the etching member 8 is used to etch the etching target region. However, not limited to this, after masking the entire area of the back surface 3 of the tempered glass plate 1 and the area excluding the etching target area on the front surface 2, the tempered glass sheet 1 is immersed in an etching solution to be etched. Areas may be etched. Furthermore, instead of etching, only a partial region (region including the vertex of the surface 2) on the surface 2 of the tempered glass plate 1 is subjected to polishing processing, so that the compressive stress layer corresponding to the partial region 5 may be removed.

Further, in the present embodiment, only a partial area on the surface 2 of the tempered glass plate 1 is the etching target area, but the entire area (100% of the area) of the surface 2 is the etching target area. The surface layer portion of the compressive stress layer 5 may be removed. In this case, the etchant may be sprayed onto the entire surface 2 using a spray or the like, or only the surface 2 of the front and back surfaces 2 and 3 may be immersed in the etchant. Further, when removing the surface layer portion of the compressive stress layer 5 corresponding to the entire area of the surface 2, the entire area of the surface 2 may be subjected to polishing.

When the removal process described above is completed, as shown in FIG. 2, the tempered glass sheet 1 is obtained with less warpage than before the removal process. In the following description, the tempered glass sheet 1 after the removal process is referred to as a "treated tempered glass sheet 1" to distinguish it from the tempered glass sheet 1 before the removal process.

In the removal step described above, if only a partial region on the front surface 2 of the tempered glass plate 1 is the target region for etching, the tempered glass plate 1 after the treatment has a convex surface 2 on the front and back surfaces 2 and 3. Only some areas of have etched processing areas. That is, part of the surface 2 includes an etched surface. On the other hand, in the removal step, when the entire region of the front surface 2 of the tempered glass plate 1 is set as the etching target region, the tempered glass plate 1 after treatment has the convex surface 2 of the front and back surfaces 2 and 3, It has an etched processing area. That is, the entire surface 2 becomes an etching surface. Of course, in this embodiment, there is no treated area on the rear surface 3 of the tempered glass sheet 1 after treatment. That is, the back surface 3 becomes a non-etching surface.

The thickness of the tempered glass sheet 1 after treatment partially decreases at the removed portion depending on the above-mentioned Δt, but the maximum thickness of the tempered glass sheet 1 after treatment is, for example, 100 μm or less, preferably 5 μm or more and 95 μm or less. It is more preferably 10 μm or more and 85 μm or less, still more preferably 15 μm or more and 75 μm or less.

Although the compressive stress depth of the treated tempered glass sheet 1 partially decreases at the removed portion according to the above-described Δt, the maximum depth DOC of the compressive stress layer of the treated tempered glass sheet 1 is, for example, 0.5 μm. 0.5 μm or more and 12.0 μm or less, more preferably 2.0 μm or more and 8.0 μm or less, more preferably 2.5 μm or more and 7.5 μm or less, and 2.5 μm or more and 5.5 μm or less.

The maximum compressive stress CS in the compressive stress layer of the tempered glass sheet 1 after treatment is, for example, 520 MPa or more and 2000 MPa or less, preferably 650 MPa or more and 1800 MPa or less, more preferably 700 MPa or more and 1700 MPa or less.

The warpage of the tempered glass sheet 1 after treatment is, for example, 1.0 mm or less, preferably 0.7 mm or less, and more preferably 0.5 mm or less.

<Second embodiment>
A second embodiment will be described below. In addition, in the description of the second embodiment and the later-described third embodiment, elements that are substantially the same as the elements described in the first embodiment will be referred to in the description of the second and third embodiments. The same reference numerals are given to the drawings to omit redundant description, and only differences from the first embodiment will be described.

As shown in FIG. 3, the difference of the second embodiment from the first embodiment is that in the removing step, the tempered glass plate 1 is laid flat instead of being vertically suspended. It is a point. Specifically, with the etching member 8 laid flat on a surface plate, the tempered glass plate 1 is placed on the etching member 8 so that the convex surface 2 of the tempered glass plate 1 faces downward. Place. As a result, the etching target region and the flat surface 7 of the etching member 8 are brought into contact with each other and etched. Also in the second embodiment, the treated tempered glass sheet 1 similar to that in the first embodiment is obtained.

<Third Embodiment>
As shown in FIG. 4, the third embodiment differs from the first embodiment in that the entire tempered glass plate 1 is not formed from a single warped portion 4, but from a plurality of warped portions (two in this embodiment). and the etching target region exists on both the front surface 2 and the back surface 3 of the tempered glass plate 1 in the removing step.

As shown in the figure, the upper side portion and the lower side portion of the tempered glass plate 1 suspended and supported in a vertical posture are warped in opposite directions. In the following description, the warped portion 4 located relatively upward and having the front surface 2 convex is referred to as a first warped portion 4a, and the warped portion located relatively downward and having the back surface 3 convex 4 is referred to as a second warped portion 4b. In the first warped portion 4a, the degree of strengthening is greater on the surface 2 side than on the surface 2 side and the back surface 3 side, and the compressive stress layer 5 is deeper than the compressive stress layer 6 on average. there is On the other hand, in the second warped portion 4b, the degree of strengthening is large on the back surface 3 side, opposite to the first warped portion 4a, and the compressive stress layer 6 is deeper than the compressive stress layer 5 on average. there is

In the first warped portion 4a, only a partial region (region including the vertex of the surface 2) on the surface 2 of the first warped portion 4a is an etching target region. On the other hand, in the second warped portion 4b, only a partial region (region including the vertex of the back surface 3) on the back surface 3 of the second warped portion 4b is an etching target region. When etching these etching target regions, the flat surface 7 of the etching member 8 is brought into contact with the etching target regions from the front surface 2 side and the back surface 3 side of the tempered glass plate 1, respectively. As a result, the surface layer portion of the compressive stress layer 5 corresponding to a partial area on the surface 2 and the surface layer portion of the compressive stress layer 6 corresponding to a partial area on the back surface 3 are removed.

In the treated tempered glass sheet 1 obtained in the third embodiment, the amount of warpage is 1 mm or less (preferably 0.7 mm or less, more preferably 0.5 mm or less). This post-treatment tempered glass sheet 1 includes a first warp portion 4a and a second warp portion 4b, a partial region on the surface 2 at the first warp portion 4a, and a region on the back surface 3 at the second warp portion 4b. Some areas have process areas that have been etched. That is, part of the front surface 2 of the first warped portion 4a and part of the back surface 3 of the second warped portion 4b include etched surfaces.

In the first to third embodiments described above, in the tempered glass plate 1, the degree of strengthening of the compressive stress layer 5 on the front surface 2 side and the compressive stress layer 6 on the back surface 3 side is average However, this is not the only case. In some cases, the depth of the layer is the same between the side with a large degree of strengthening and the side with a small degree of strengthening, and there is a difference only in the value of the maximum compressive stress CS. Of course, there may be differences in both the layer depth and the value of the maximum compressive stress CS (see examples below).

Here, it is also possible to apply the following modifications to each of the above-described embodiments. In each of the above-described embodiments, the etching member 8 is provided with the flat surface 7, but this is not the only option. It may be provided on the member 8 .

As an example, the treated tempered glass sheet 1 was manufactured in the same manner as in the above embodiment, and the amount of warpage in the tempered glass sheet 1 before the removal step and the amount of warp in the treated tempered glass plate 1 after the removal step were measured. compared with The results are shown in [Table 1] below.

First, as a tempering step, the glass composition is mol % SiO ₂ 66.4%, Al ₂ O ₃ 11.5%, B ₂ O ₃ 0.5%, K ₂ O 1.4%, Na ₂ O 15 .2%, Li ₂ O 0.02%, MgO 4.8%, CaO 0.1%, SnO ₂ 0.1% glass plate for chemical strengthening (vertical dimension x horizontal dimension: 200 mm x 100 mm, thickness: 50 μm) were immersed in molten salt (KNO ₃ , 430° C.) for 10 minutes to obtain a plurality of tempered glass plate 1 samples.

Next, two warped samples were extracted from the plurality of samples, washed, and then removed. Specifically, one of the two samples is Example 1 and the other is Example 2. In Example 1, the same aspect as the second embodiment described above, and in Example 2, the first embodiment described above. A removal step was performed by etching in the same manner as the morphology to produce a post-treated tempered glass sheet 1 . The item "processing method" in [Table 1] below indicates the posture of the tempered glass plate 1 when performing the removal step.

For both Examples 1 and 2, a PVA sponge manufactured by Aion Co., Ltd. (product name: B-Fine) was used as the etching member 8 for etching, and an etching solution (HF 1 wt% aqueous solution) was applied to the PVA sponge. Impregnated. In each of Examples 1 and 2, the contact time between the sample and the PVA sponge is as shown in the "treatment time" item in [Table 1] below.

Then, in each of Examples 1 and 2, a change in the amount of warpage before and after the removal process was verified. Each item "convex side CS", "concave side CS", "convex side DOC", "concave side DOC", and "warp amount" in "before treatment" in the following [Table 1] is the tempered glass before the removal process. In the plate 1, the maximum compressive stress CS on the convex side, the maximum compressive stress CS on the concave side, the maximum depth DOC of the compressive stress layer on the convex side, the maximum depth DOC of the compressive stress layer on the concave side, and the amount of warpage are shown respectively. In addition, the items "convex side CS", "convex side DOC", and "warp amount" of "after treatment" are the maximum compressive stress CS on the convex side and the convex side The maximum depth DOC and the amount of warpage of the compressive stress layer at .

As is clear from the results shown in [Table 1], it can be seen that the amount of warpage is greatly suppressed after the removal process compared to before the removal process. Furthermore, it can be seen that even with an ultra-thin tempered glass plate having a thickness of 50 μm, the amount of warpage can be reduced to 1 mm or less. Further, as can be understood from the results shown in [Table 1], the values of the convex side CS and the convex side DOC after the removal process are close to the values of the concave side CS and the concave side DOC before the removal process. That is, the strengthening difference between the front and back surfaces can be made extremely small with the execution of the removing process. From the above, it is presumed that according to the method for manufacturing a tempered glass sheet according to the present disclosure, it is possible to realize a tempered glass sheet that is thin but has little warpage.

REFERENCE SIGNS LIST 1 tempered glass plate 2 front surface 3 back surface 4 warped portion 4a first warped portion 4b second warped portion 5 compressive stress layer 6 compressive stress layer 7 flat surface 8 etching member

Claims (12)

A method for producing a tempered glass sheet, comprising a tempering step of chemically tempering a flexible glass sheet to obtain a tempered glass sheet having compression stress layers formed on both front and back sides,
The tempered glass plate includes a warped portion that is warped so that one of the front and back surfaces is convex,
A method for manufacturing a tempered glass sheet, further comprising a removing step of reducing warpage by removing a surface layer portion of the compressive stress layer on the convex side of the warped portion. 2. The surface layer portion of the compressive stress layer corresponding to the partial area is removed by etching or polishing only a partial area on the convex surface of the warped portion. A method for producing the tempered glass sheet described. 3. The method for manufacturing a tempered glass sheet according to claim 2, wherein etching is performed while the tempered glass sheet is suspended and supported in a vertical position. 4. The method for manufacturing a tempered glass sheet according to claim 2, wherein a region including the vertex of the convex surface in the warped portion is etched. The tempered glass plate includes a plurality of warped portions,
5. The plurality of warped portions include the warped portion having a convex front surface and the warped portion having a convex rear surface of the tempered glass sheet. The method for producing the tempered glass plate according to 1. Using an etching member having a flat surface capable of holding an etchant,
The tempered glass plate according to any one of claims 2 to 5, wherein etching is performed by bringing the partial region on the convex surface of the warped portion and the flat surface of the etching member into contact with each other. manufacturing method. 7. The method for manufacturing a tempered glass sheet according to claim 6, wherein the area of the flat surface of the etching member is equal to or larger than the area of the tempered glass sheet. The etching member is a sponge-like member impregnated with the etching liquid,
8. The method for manufacturing a tempered glass sheet according to claim 6, wherein the etching liquid contains HF or a mixed acid containing HF. The entire tempered glass plate consists of the single warped portion,
2. The tempered glass sheet according to claim 1, wherein the surface layer portion of the compressive stress layer corresponding to the entire region is removed by etching or polishing the entire region of the convex surface in the warped portion. Production method. When the maximum depth of the compressive stress layer on the convex surface side before the removing step is DOC, and the thickness of the surface layer portion of the compressive stress layer removed in the removing step is Δt,
10. The method for producing a tempered glass sheet according to any one of claims 1 to 9, wherein Δt≦0.8×DOC is satisfied. The thickness of the tempered glass plate before the removing step is 100 μm or less,
The method for producing a tempered glass sheet according to any one of claims 1 to 10, wherein the amount of warping of the tempered glass sheet after the removing step is 1 mm or less. A tempered glass plate having a thickness of 100 μm or less,
Including a warped part that warps so that one of the front and back surfaces is convex,
Having a processed region in which etching is applied to at least a partial region on the convex surface of the warped portion;
A tempered glass sheet, wherein the amount of warp of the tempered glass sheet is 1 mm or less.

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