阅读说明：本技术 化学强化玻璃及可折叠装置 (Chemically strengthened glass and foldable device ) 是由 鹿岛出 藤原祐辅 于 2020-03-18 设计创作，主要内容包括：本发明涉及一种化学强化玻璃,其特征在于,具备第1主面和第1主面的相反侧的第2主面,所述化学强化玻璃的厚度为0.30mm以下,所述化学强化玻璃具有以第1主面呈凸面且第2主面呈凹面的方式弯曲的形状,所述化学强化玻璃在以第1主面为下侧的方式载置于水平面、且无重力以外的外力作用的状态下,第1主面的一部分不与水平面接触。(The present invention relates to a chemically strengthened glass, which is characterized by comprising a 1 st main surface and a 2 nd main surface on the opposite side of the 1 st main surface, wherein the chemically strengthened glass has a thickness of 0.30mm or less, the chemically strengthened glass has a shape that the 1 st main surface is convex and the 2 nd main surface is concave, and a part of the 1 st main surface is not in contact with a horizontal surface in a state that the 1 st main surface is placed on the horizontal surface as a lower side and no external force other than gravity acts.)

1. A chemically strengthened glass comprising a 1 st main surface and a 2 nd main surface on the opposite side of the 1 st main surface, wherein the chemically strengthened glass has a thickness of 0.30mm or less,

the chemically strengthened glass has a shape curved such that the 1 st main surface is convex and the 2 nd main surface is concave,

the chemically strengthened glass is placed on a horizontal surface such that the 1 st main surface is located on the lower side, and in a state where no external force other than gravity acts, a part of the 1 st main surface does not contact the horizontal surface.

2. The chemically strengthened glass according to claim 1,

which is in a curved rectangular shape and is provided with a plurality of grooves,

each of the 1 st major surface and the 2 nd major surface has an opposite pair of end portions that are not curved,

the chemically strengthened glass is placed on a horizontal plane such that the first main surface 1 is located below the glass substrate, and can be cut by a plane passing through: a 1 st point which is a center point of the one end portion of the 2 nd main surface which is not bent; a 2 nd point which is a center point of the other end portion of the 2 nd main surface which is not bent; a 3 rd point which is a center point of the one end portion of the 1 st main surface which is not bent; and a 4 th point which is a center point of the other end portion of the 1 st main surface which is not bent,

in a cross-sectional view taken along the plane, an angle θ formed by the 1 st point, the 5 th point and the 2 nd point is 165 ° or less, and the 5 th point is a point on the 2 nd main surface and having a maximum distance from a straight line connecting the 1 st point and the 2 nd point.

3. The chemically strengthened glass according to claim 1 or 2, wherein the restoring force at 10mm bending measured by the method described below is 1.0kgf or less,

method for measuring restoring force at 10mm bending:

using a chemically strengthened glass having a shape in which a rectangular glass having a short side of 60mm × a long side of 120mm is bent along a line connecting the centers of the long sides, a 1 st supporting disk and a 2 nd supporting disk are arranged so that a supporting surface of the 1 st supporting disk and a supporting surface of the 2 nd supporting disk face each other in parallel, one end portion of the 1 st main surface and the other end portion of the 1 st main surface of the chemically strengthened glass, which are not bent, are fixed to overlap each other in a plan view on the supporting surfaces of the 1 st supporting disk and the 2 nd supporting disk, respectively, and a restoring force when a distance D between the supporting surface of the 1 st supporting disk and the supporting surface of the 2 nd supporting disk is 10mm is measured and is regarded as a restoring force when the glass is bent by 10 mm.

4. The chemically strengthened glass according to any one of claims 1 to 3, wherein a restoring force in a plane measured by a method described below is 1.0kgf or less,

the method for measuring the restoring force in a plane comprises the following steps:

using a chemically strengthened glass having a shape in which a rectangular glass having a short side of 60mm × a long side of 120mm is bent along a line connecting the centers of the long sides, a 1 st support plate and a 2 nd support plate are disposed so that a support surface of the 1 st support plate and a support surface of the 2 nd support plate face each other in parallel, the chemically strengthened glass is placed on the support surface of the 2 nd support plate so that the 2 nd main surface is located below the support surface, and a restoring force is measured by setting a distance D between the support surface of the 1 st support plate and the support surface of the 2 nd support plate to be equal to a thickness of the chemically strengthened glass and is used as a planar restoring force.

5. A foldable device having a flexible display and a housing having a deformation portion along which the foldable device can be folded,

the flexible display device comprises a cover glass formed of the chemically strengthened glass according to any one of claims 1 to 4,

the cover glass is configured in such a manner that a portion bent when the foldable device is folded is deformed.

Technical Field

The invention relates to chemically strengthened glass and a foldable device.

Background

In protective covers for displays of various electronic devices such as smartphones, glass covers (cover glasses) are often used from the viewpoint of improving the appearance. Glass has high theoretical strength, but the strength is greatly reduced by damage. Therefore, for cover glass that is required to have strength such as impact resistance, chemically strengthened glass in which a compressive stress layer is formed on the surface of the glass by ion exchange or the like is used.

In recent years, foldable electronic devices (foldable devices) having a bendable display have been marketed. In order to use as cover glass for such a display, chemically strengthened glass having flexibility is desired.

For example, patent document 1 discloses a flexible ultrathin chemically strengthened glass. The glass is the following ultrathin chemically strengthened glass: the thickness t is less than 500 μm, the depth DOL of the ion exchange layer is less than 30 μm, the surface compressive stress CS is 100MPa to 700MPa, the central tensile stress CT is less than 120MPa, and the DOL, CS and CT satisfy a specific relationship.

Patent document 2 discloses an ultrathin chemically strengthened glass having a thickness t of 0.4mm or less, a DOL of less than 30 μm, a CS of 100MPa to 700MPa, and a CT of less than 120MPa, and satisfying a specific relationship among DOL, CS, and CT.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-508954

Patent document 2: japanese Kohyo publication 2017-529304

Disclosure of Invention

Problems to be solved by the invention

In the chemically strengthened glass having flexibility, it is preferable to thicken the glass within a range in which flexibility can be secured in order to improve strength. However, when the glass is thickened, a strong restoring force is generated at the time of bending. When the glass having a large restoring force at the time of being bent is used for the cover glass for the foldable device, there are problems that it is difficult to fold the foldable device, the foldable device is naturally opened even when being folded, and the foldable device is violently opened at the time of being opened.

Thus, it is difficult to achieve both improvement in strength and suppression of restoring force when the flexible glass is bent.

In view of the above circumstances, an object of the present invention is to provide chemically strengthened glass having flexibility and excellent strength, and having a small restoring force when bent.

Means for solving the problems

The chemically strengthened glass according to the present invention for solving the above problems is characterized by comprising a 1 st main surface and a 2 nd main surface on the opposite side of the 1 st main surface, the chemically strengthened glass having a thickness of 0.30mm or less, the chemically strengthened glass having a shape in which the 1 st main surface is curved so as to be convex and the 2 nd main surface is curved so as to be concave, and a part of the 1 st main surface being not in contact with a horizontal surface in a state in which the 1 st main surface is placed on the horizontal surface so as to be a lower side and no external force other than gravity acts.

The chemically strengthened glass of the present invention may be in a form of: the chemically strengthened glass is in a curved rectangular shape, wherein both the 1 st main surface and the 2 nd main surface have a pair of opposite end parts which are not curved, and the chemically strengthened glass can be cut by a plane passing through the following points in a state that the 1 st main surface is placed on a horizontal plane in a manner that the 1 st main surface is the lower side and no external force other than gravity acts on the glass: a 1 st point which is a center point of one end portion of the 2 nd main surface which is not bent; a 2 nd point which is a center point of the other end portion of the 2 nd main surface which is not bent; a 3 rd point which is a center point of the one end portion of the 1 st main surface which is not bent; and a 4 th point which is a center point of the other end portion of the 1 st main surface which is not bent, wherein an angle θ formed by the 1 st point, the 5 th point and the 2 nd point is 165 ° or less in a cross-sectional view taken along the plane, and the 5 th point is a point which is on the 2 nd main surface and has the largest distance from a straight line connecting the 1 st point and the 2 nd point.

In one embodiment of the chemically strengthened glass of the present invention, the restoring force at 10mm bending measured by the following method may be 1.0kgf or less.

(method of measuring restoring force at 10mm bending)

Using a chemically strengthened glass having a shape in which a rectangular glass having a short side of 60mm × a long side of 120mm is bent along a line connecting the centers of the long sides, a 1 st supporting disk and a 2 nd supporting disk are arranged so that a supporting surface of the 1 st supporting disk and a supporting surface of the 2 nd supporting disk face each other in parallel, one end portion of the 1 st main surface of the chemically strengthened glass, which is not bent, and the other end portion of the 1 st main surface, which is not bent, are fixed to the supporting surfaces of the 1 st supporting disk and the 2 nd supporting disk so as to overlap each other in a plan view, respectively, and a restoring force when a distance D between the supporting surface of the 1 st supporting disk and the supporting surface of the 2 nd supporting disk is 10mm is measured and is used as the restoring force when the disk is bent by 10 mm.

In one embodiment of the chemically strengthened glass of the present invention, the planar recovery force may be 1.0kgf or less as measured by the following method.

(method of measuring restoring force in planar state)

Using a chemically strengthened glass having a shape in which a rectangular glass having a short side of 60mm × a long side of 120mm is bent along a line connecting the centers of the long sides, the 1 st supporting disk and the 2 nd supporting disk are arranged so that the supporting surface of the 1 st supporting disk and the supporting surface of the 2 nd supporting disk face each other in parallel, the chemically strengthened glass is placed on the supporting surface of the 2 nd supporting disk so that the 2 nd main surface is positioned on the lower side, and the restoring force is measured by setting the distance D between the supporting surface of the 1 st supporting disk and the supporting surface of the 2 nd supporting disk to be equal to the thickness of the chemically strengthened glass and is used as the planar restoring force.

In addition, the foldable device of the present invention is provided with a flexible display and a housing having a deformation portion, the foldable device being foldable along the deformation portion,

the flexible display is provided with a cover glass formed of the chemically strengthened glass of the present invention,

the cover glass is disposed in such a manner that a portion bent when the foldable device is folded is deformed.

ADVANTAGEOUS EFFECTS OF INVENTION

The chemically strengthened glass of the present invention has flexibility, excellent strength, and a small restoring force when bent.

Drawings

FIG. 1 is a perspective view showing one embodiment of a chemically strengthened glass of the present invention.

FIG. 2 is a side view showing one embodiment of the chemically strengthened glass of the present invention.

FIG. 3 is a side view showing a state in which one embodiment of the chemically strengthened glass of the present invention is deformed.

FIG. 4 is a side view showing a modification of the chemically strengthened glass according to the embodiment of the present invention.

FIG. 5 is a perspective view showing one embodiment of the chemically strengthened glass of the present invention.

FIG. 6 is a sectional view showing one embodiment of the chemically strengthened glass of the present invention.

FIG. 7 is a cross-sectional view showing a modification of the chemically strengthened glass according to the embodiment of the present invention.

FIG. 8 is a cross-sectional view showing a modification of the chemically strengthened glass according to the embodiment of the present invention.

Fig. 9 is a diagram for explaining a bending test apparatus.

FIG. 10 is a view for explaining a method of measuring the restoring force at 10mm bending.

Fig. 11 is a diagram for explaining a method of measuring the restoring force in a planar state.

Fig. 12 is a diagram for explaining a method of measuring the restoring force in a planar state.

Fig. 13 is a schematic view showing a closed state of an embodiment of the foldable device of the present invention.

Fig. 14 is a schematic view showing an opened state of an embodiment of the foldable device of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the embodiments described below. In the following drawings, members and portions that exhibit the same function are sometimes described with the same reference numerals, and redundant description may be omitted or simplified. The embodiments shown in the drawings are schematic for clearly explaining the present invention, and do not accurately show actual dimensions and scale.

[ chemically strengthened glass ]

Fig. 1 and 2 show schematic views of the chemically strengthened glass of the present embodiment (hereinafter also referred to as "glass of the present embodiment"). Fig. 1 is a perspective view, and fig. 2 is a side view. The glass 1 of the present embodiment is a chemically strengthened glass having a thickness of 0.30mm or less, and including a 1 st main surface 2 and a 2 nd main surface 3 on the opposite side of the 1 st main surface 2.

The glass 1 of the present embodiment is characterized by being subjected to bending. That is, the glass 1 of the present embodiment is characterized by having a shape curved so that the 1 st main surface 2 is convex and the 2 nd main surface 3 is concave. The curved shape is preferably a V-shape, a U-shape, or a substantially U-shape of the glass 1 when viewed from the side.

Therefore, in the glass 1 of the present embodiment, the first main surface 2 is placed on the horizontal surface H such that the first main surface 2 is located on the lower side, and a part of the first main surface 2 does not contact the horizontal surface H in a state where no external force other than gravity acts. Since conventional flexible glass that has not been subjected to bending is flat when it is not bent, the entire main surface on the horizontal plane side is in contact with the horizontal plane in a state of being placed on the horizontal plane and free from an external force other than gravity. In this regard, the conventional flexible glass is different from the glass 1 of the present embodiment.

The glass 1 of the present embodiment having the above-described configuration deforms less in the closing direction (direction in which the degree of bending increases) than when the flat glass deforms in the same shape, and therefore the restoring force due to the deformation is also small.

For example, when a conventional flat glass is deformed in a folded shape as shown in fig. 3, the glass needs to be bent by 180 ° to be deformed, and a large restoring force is generated. On the other hand, since the glass 1 of the present embodiment has a bent shape before bending, the amount of deformation at the time of bending is small, and the generated restoring force is also small.

As described above, the glass 1 of the present embodiment suppresses the restoring force when bent by a method not involving a decrease in strength, such as bending without an external force other than gravity, and not a method involving a decrease in strength, such as reducing the thickness of the sheet. Thus, the glass 1 of the present embodiment can achieve both the improvement of strength and the suppression of restoring force.

The shape of the glass 1 of the present embodiment is not particularly limited as long as the above conditions are satisfied, and may have a flat portion and a curved portion as shown in fig. 1 and 2, for example, or may have a shape that is curved as a whole as in a modification shown in fig. 4.

In addition, from the viewpoint of use as a cover glass for a foldable device, the glass 1 of the present embodiment is preferably rectangular in shape with the 1 st principal surface 2 and the 2 nd principal surface 3 curved, and the principal surfaces more preferably have: a pair of opposite end portions bent in a U-shape, a substantially U-shape, or a V-shape; and an opposite pair of end portions that are not bent.

The degree of bending of the glass 1 of the present embodiment is also not particularly limited, and is preferably large in order to suppress the restoring force at the time of bending in the closing direction.

On the other hand, if the degree of bending is too large, the restoring force generated when the cover glass is deformed in the opening direction becomes large, and when the cover glass is applied to a cover glass for a foldable device, there are problems that the cover glass is difficult to open, the cover glass is naturally folded even when opened, and the cover glass is violently opened when closed.

The degree of bending of the glass 1 of the present embodiment can be evaluated by various indexes, for example, by using the angle θ. The angle θ will be described below with reference to the drawings.

Fig. 5 is a perspective view of the glass 1 according to the present embodiment for explaining the angle θ. The glass has a curved rectangular shape, and the 1 st main surface 2 and the 2 nd main surface 3 each have a pair of opposite end portions that are not curved.

First, in the chemically strengthened glass 1 which is placed on a horizontal plane such that the 1 st main surface 2 is located on the lower side and in which no external force other than gravity acts, the center point of the non-bent one end portion 3a of the 2 nd main surface 3 is set to the 1 st point P1, the center point of the non-bent other end portion 3b of the 2 nd main surface 3 is set to the 2 nd point P2, the center point of the non-bent one end portion 2a of the 1 st main surface 2 is set to the 3 rd point P3, and the center point of the non-bent other end portion 2b of the 1 st main surface 2 is set to the 4 th point P4. Next, a cross-sectional view taken along a plane passing through the 1 st point P1, the 2 nd point P2, the 3 rd point P3, and the 4 th point P4 (i.e., a plane passing through a broken line in fig. 5) is examined.

The following may be cut by a plane passing through the 1 st to 4 th points P1 to P4: the bent portion of the chemically strengthened glass 1 perpendicularly intersects with respect to a line segment (broken line) connecting the 1 st point P1 and the 2 nd point P2 on the 2 nd main surface. This may also be the case in other words: the bent portion of the chemically strengthened glass 1 perpendicularly intersects with respect to a line segment (broken line) connecting the 3 rd point P3 and the 4 th point P4 on the 1 st main surface.

The bending portion of the chemically strengthened glass 1 perpendicularly intersects with a line segment (broken line) connecting the 1 st point P1 and the 2 nd point P2, and when the chemically strengthened glass 1 is bent in a V-shape as shown in fig. 6, the bending line as a valley is orthogonal to the line segment. In the case where the chemically strengthened glass 1 is bent in a U-shape or a substantially U-shape as shown in fig. 8, it means that a straight line as an axis of bending is perpendicular to the line segment.

Fig. 6 is a cross-sectional view of the glass 1 shown in fig. 5 cut as described above. In this cross-sectional view, an angle formed by the 1 st point P1, the 5 th point P5, and the 2 nd point P2 is defined as an angle θ, and the 5 th point P5 is a point on the 2 nd main surface 3 at which a distance d from a straight line L connecting the 1 st point P1 and the 2 nd point P2 is the largest.

The smaller the angle θ, the greater the degree of bending.

Fig. 5 and 6 show examples of glass having a flat portion and bent near the center. This example is a case where the curved portion on the 2 nd main surface 3 is linear, that is, a case where the curved portion is bent in a V-shape.

On the other hand, the angle θ may be similarly determined for glasses having different bending modes. Fig. 7 and 8 show cross-sectional views of modified examples of different shapes. The glass of the modification shown in fig. 7 has a shape curved away from the vicinity of the center, but the angle θ can be determined similarly using such a glass. The glass of the modification shown in fig. 8 has no flat portion and is curved as a whole, that is, is curved in a gentle U-shape. Even with such a glass, as shown in fig. 8, the angle θ can be similarly obtained from the 1 st point P1, the 5 th point P5, and the 2 nd point P2.

The size of the angle θ can be adjusted as appropriate depending on the application of the glass 1 of the present embodiment, and is, for example, preferably 15 ° or more, more preferably 30 ° or more, and further preferably 45 ° or more, and is preferably 165 ° or less, more preferably 150 ° or less, and further preferably 135 ° or less.

The radius of curvature of the 5 th point P5 in the cross-sectional view when the chemically strengthened glass 1 is bent into a U shape or a substantially U shape is not particularly limited, and can be appropriately adjusted depending on the application of the glass 1 of the present embodiment.

The thickness of the glass 1 of the present embodiment is 0.30mm or less in order to obtain flexibility. In addition, the thickness of the chemically strengthened glass 1 of the present embodiment is preferably 0.25mm or less, more preferably 0.20mm or less, and further preferably 0.17mm or less, for further improvement in flexibility, weight reduction, and suppression of restoring force.

On the other hand, the thickness of the glass 1 of the present embodiment is preferably 0.03mm or more, more preferably 0.04mm or more, further preferably 0.05mm or more, and further preferably 0.07mm or more from the viewpoint of strength.

The surface compressive stress value (CS) of the glass 1 of the present embodiment is preferably large from the viewpoint of strength. By increasing the CS to increase the strength, the scratch resistance and crack resistance are improved, and further, the flexibility is improved because cracking is less likely to occur even when the sheet is bent. The CS of the glass 1 of the present embodiment is preferably 400MPa or more, more preferably 450MPa or more, and further preferably 500MPa or more.

On the other hand, if CS is too large, it becomes difficult to reduce internal tensile stress (CT) described later, and therefore, the CS of the glass 1 of the present embodiment is preferably 1200MPa or less, more preferably 1100MPa or less, and further preferably 1000MPa or less.

The Depth (DOL) of the compressive stress layer of the glass 1 of the present embodiment is preferably 3 μm or more, more preferably 5 μm or more, further preferably 7 μm or more, and particularly preferably 8 μm or more, in order to improve strength and improve scratch resistance, crack resistance, and flexibility.

On the other hand, if DOL is too large, it becomes difficult to reduce internal tensile stress (CT) described later, and therefore DOL of the glass 1 of the present embodiment is preferably 25 μm or less, more preferably 20 μm or less, and further preferably 18 μm or less.

The internal tensile stress (CT) of the glass 1 of the present embodiment is preferably 250MPa or less, more preferably 200MPa or less, further preferably 180MPa or less, further preferably 150MPa or less, and particularly preferably 120MPa or less, in order to suppress the fragments from scattering violently upon crushing.

The composition of the glass 1 of the present embodiment is not particularly limited as long as the mother composition, that is, the composition before the chemical strengthening treatment contains alkali metal ions. An example of the mother composition of the glass 1 of the present embodiment will be described in detail later.

The restoring force of the glass 1 of the present embodiment can be evaluated by various values, for example, by values measured by a bending test shown below.

< bending test >

(bending test apparatus)

Fig. 9 is a schematic diagram of a bending test apparatus used in the bending test. The bending test apparatus is an apparatus for deforming (bending) the chemically strengthened glass 1 of the present embodiment.

The bending test device is provided with: the base 12, the 1 st support plate (upper support plate) 14, the 2 nd support plate (lower support plate) 16, the adjusting portion 300, the support portion 50, and the placement portion 60.

The 1 st support disk 14 has a support surface 14a as a downward flat surface, and the 2 nd support disk 16 has a support surface 16a as an upward flat surface. Stoppers to be abutted against the end portions of the chemically strengthened glass 1 were provided on these supporting surfaces according to the test method. The details will be described later.

The adjusting part 300 adjusts the distance D between the support surface 14a of the 1 st support plate 14 and the support surface 16a of the 2 nd support plate 16, which are parallel to each other. The adjusting unit 300 is constituted by a retractable elevator (jack), for example.

The support portion 50 is fixed to the base 12, and rotatably supports the 1 st supporting plate 14 via a coupling portion 52 such as a hinge. The 1 st support disk 14 is rotatable between a test position (1 st position) where the support surface 14a of the 1 st support disk 14 is parallel to the support surface 16a of the 2 nd support disk 16, and an installation position (2 nd position) where the support surface 14a of the 1 st support disk 14 is inclined with respect to the support surface 16a of the 2 nd support disk 16. While the 1 st support plate 14 is rotated from the test position to the set position, the radius of curvature of the bent portion of the chemically strengthened glass supported by the 1 st support plate 14 and the 2 nd support plate 16 gradually increases.

The mounting portion 60 is fixed to the base 12 and is mounted on the 1 st supporting plate 14 disposed above the 2 nd supporting plate 16. When the 1 st support plate 14 is at the test position, it can be placed on the upper end surface of the placement portion 60. In order to stabilize the posture of the 1 st support plate 14, the 1 st support plate 14 may be placed on a plurality of placement portions 60. Each placement portion 60 is formed with a bolt hole to which a shaft portion 62b of a bolt 62 is screwed. Further, the 1 st support plate 14 is formed with a through hole through which the shaft portion 62b of the bolt 62 passes. The 1 st support plate 14 is sandwiched between the head 62a of the bolt 62 and each placement portion 60, and the posture of the 1 st support plate 14 can be stabilized.

The restoring force of the glass 1 of the present embodiment when bent can be evaluated by measuring the load required when the glass 1 of the present embodiment is deformed (bent) under various conditions using the above-described bending test apparatus. For example, a load sensor (not shown) may be used to measure the load.

For example, the restoring force at the time of bending of 10mm, which is measured under the conditions shown below using a load cell, and the restoring force at the time of plane can be used as indexes for evaluation of the restoring force at the time of being bent.

(restoring force at 10mm bending)

The sample used was chemically strengthened glass having a rectangular shape with a short side of 60mm × a long side of 120mm, and bent along a line connecting the centers of the long sides. In order to measure the restoring force at the time of 10mm bending, first, a stopper 17a abutting on one non-bent end 1a of the chemically strengthened glass 1 is provided on the supporting surface 14a of the 1 st supporting disk 14, and a stopper 17b abutting on the other non-bent end 1b of the chemically strengthened glass 1 is provided on the supporting surface 16a of the 2 nd supporting disk 16. The stoppers 17a and 17b are provided so that the end portions 1a and 1b of the chemically strengthened glass 1 are fixed at positions overlapping in a plan view during the test. Next, as shown in fig. 9, the chemically strengthened glass 1 is set so that the end 1a abuts against the stopper 17a and the end 1b abuts against the stopper 17 b. Thereafter, the 1 st support plate 14 and the 2 nd support plate are brought close to each other, and as shown in fig. 10, the restoring force when the distance D between the support surface 14a of the 1 st support plate 14 and the support surface 16a of the 2 nd support plate 16 is 10mm is regarded as the restoring force at the time of 10mm bending.

The glass 1 of the present embodiment has a small restoring force at 10mm bending.

The recovery force at the time of bending of 10mm of the glass 1 of the present embodiment is preferably 1.0kgf or less, more preferably 0.9kgf or less, and further preferably 0.8kgf or less, in order to suppress the recovery force at the time of bending in the closing direction. The lower limit is not particularly limited, but is usually 0.2kgf or more.

The above-mentioned restoring force at the time of 10mm bending is: the restoring force was measured using a glass having a rectangular shape in which a short side of 60mm × a long side of 120mm was bent along a line connecting the centers of the long sides. For the glass having a size different from the above, the same evaluation can be performed and converted in accordance with the glass size when the above-mentioned restoring force at the time of bending of 10mm is measured. The restoring force is proportional to the length of the short side.

The above-described restoring force at the time of bending of 10mm can be adjusted by appropriately adjusting the thickness of the glass 1 of the present embodiment, the magnitude of the angle θ, the radius of curvature of the bent portion, the composition (mother composition), conditions of various processes in the manufacturing method described later, and the like. The same applies to the planar restoring force described later.

(planar time recovery force)

Since the glass 1 of the present embodiment has a curved shape in a state where no external force is applied, a restoring force is generated even when the glass is formed into a flat shape different from a flat glass.

As a sample for measuring the planar restoring force (hereinafter, also referred to as "planar restoring force"), a chemically strengthened glass having a rectangular shape with a short side of 60mm × a long side of 120mm and bent along a line connecting the centers of the long sides was used.

First, as shown in fig. 11, the glass 1 is placed on the support surface 16a of the 2 nd support plate 16 of the bending test apparatus so that the 2 nd main surface 3 is positioned below. Thereafter, the 1 st support plate 14 and the 2 nd support plate 16 are brought close to each other, and as shown in fig. 12, the distance D between the support surface 14a of the 1 st support plate 14 and the support surface 16a of the 2 nd support plate 16 is set to a restoring force equal to the thickness of the glass 1, which is a planar restoring force. The glass 1 of the present embodiment is different from a flat glass in that the restoring force is not zero in the flat surface.

The planar recovery force of the glass 1 of the present embodiment is preferably 1.0kgf or less, more preferably 0.9kgf or less, and further preferably 0.8kgf or less, in order to suppress the recovery force when bending in the opening direction. The lower limit is not particularly limited, but is usually 0.2kgf or more.

It should be noted that the planar restoring force is: the restoring force was measured using a glass having a rectangular shape in which a short side of 60mm × a long side of 120mm was bent along a line connecting the centers of the long sides. For glasses having a size different from the above, the same evaluation can be performed and converted according to the glass size when the restoring force in a plane is measured. The restoring force is proportional to the length of the short side.

[ foldable device ]

The application of the glass of the present embodiment is not particularly limited, and a cover glass for a flexible display of a foldable device can be exemplified as an example of a suitable application.

Fig. 13 and 14 are schematic views showing a foldable device including a cover glass made of the chemically strengthened glass of the present embodiment (hereinafter, also referred to as "foldable device of the present embodiment"). Fig. 13 is a schematic view showing a closed state, and fig. 14 is a schematic view showing an open state.

The foldable device 5 of the present embodiment includes a housing 6 and a flexible display 7.

The housing 6 includes a deformable portion 6a formed of a hinge or a flexible member, and the flexible display 7 is a flexible display. Therefore, the foldable device 5 of the present embodiment can be folded along the deformable portion 6a of the housing 6 and deformed into various states such as a closed state shown in fig. 13 and an open state shown in fig. 14. In fig. 13, the case 6 includes only 1 deforming portion, but the case 6 may include a plurality of deforming portions.

The flexible display 7 includes a cover glass 1 formed of the glass 1 of the present embodiment. The cover glass 1 is disposed so that the bent portion of the glass 1 of the present embodiment is bent when the foldable device 5 is deformed at the deformation portion 6 a.

With such a configuration, in the foldable device 5 of the present embodiment, the restoring force due to the cover glass 1 in the closed state is smaller than that of a foldable device using a flat glass as the cover glass. Therefore, the foldable device 5 of the present embodiment is less likely to be difficult to fold, and is likely to open naturally even when folded, and is likely to open violently when opened.

[ method for producing chemically strengthened glass ]

The method for producing the chemically strengthened glass of the present embodiment is not particularly limited, and the chemical strengthening treatment may be performed after the flat glass for chemical strengthening is given a curved shape, or the curved shape may be given after the chemical strengthening treatment is performed on the flat glass for chemical strengthening. The term "glass for chemical strengthening" refers to glass before chemical strengthening is performed.

Hereinafter, an example of the method for producing chemically strengthened glass according to the present embodiment in which a bent shape is given to a planar glass for chemical strengthening and then a chemical strengthening treatment is performed will be described.

An example of the method for producing chemically strengthened glass according to the present embodiment described below includes the following steps (1) to (4).

(1) Preparation process of glass for chemical strengthening

(2) Cutting step

(3) Bending process

(4) Chemical strengthening treatment step

(1) The chemical strengthening glass preparation step is a step of preparing a chemical strengthening glass to be chemically strengthened.

(2) The cutting step is a step of cutting the glass for chemical strengthening into a desired size and shape.

(3) The bending step is a step of applying bending to the glass for chemical strengthening to give a bent shape.

(4) The chemical strengthening treatment step is a step of forming a compressive stress layer on the surface of the glass for chemical strengthening to which a curved shape is imparted by chemical strengthening treatment.

(1) Preparation process of glass for chemical strengthening

The method for producing the glass for chemical strengthening is not particularly limited, and examples thereof include the following methods: a method in which a glass raw material is charged into a continuous melting furnace with its kind and amount appropriately adjusted so as to obtain a desired composition, heated and melted, clarified, supplied to a forming apparatus, and then the molten glass is formed into a sheet shape and slowly cooled.

Various methods can be used for forming the glass. Examples of the method include a down-draw method (for example, an overflow down-draw method, a slit down-draw method, a flat-draw method, and the like), a float method, a roll out method, and a press method.

The glass may be formed to have a desired thickness by forming the glass, or may be formed to have a desired thickness by performing thinning treatment (thinning treatment) after forming the glass. As a method of the thinning process, chemical etching, grinding, polishing, and the like can be cited. The thinning treatment is preferably performed to remove fine scratches on the glass surface and obtain a glass having high strength, and particularly preferably performed by chemical etching.

The composition of the glass for chemical strengthening is not particularly limited as long as it is a composition capable of forming a compressive stress layer by chemical strengthening treatment. Examples of the chemically strengthened glass include aluminosilicate glass, soda-lime glass, borosilicate glass, lead glass, alkali barium glass, and aluminoborosilicate glass.

The chemical strengthening glass may have the following composition, for example. The following compositions are all expressed in mol% based on oxide.

(1) Containing SiO₂ 50～80％、Al₂O₃ 2～25％、Li₂O 0～10％、Na₂O 0～18％、K₂0 to 10% of O, 0 to 15% of MgO, 0 to 5% of CaO and ZrO₂0 to 5% of glass.

(2) Containing SiO₂ 50～74％、Al₂O₃ 1～10％、Na₂O 6～14％、K₂O3-11%, MgO 2-15%, CaO 0-6%, and ZrO₂0 to 5% and SiO₂And Al₂O₃The total content of (A) is 75% or less, Na₂O and K₂A glass having a total content of O of 12 to 25% and a total content of MgO and CaO of 7 to 15%.

(3) Containing SiO₂ 68～80％、Al₂O₃ 4～10％、Na₂O 5～15％、K₂0 to 1% of O, 4 to 15% of MgO, and ZrO₂0 to 1% of glass.

(4) Containing SiO₂ 67～75％、Al₂O₃ 0～4％、Na₂O 7～15％、K₂1 to 9% of O, 6 to 14% of MgO, and ZrO₂0 to 1.5% and SiO₂And Al₂O₃The total content of (a) is 71-75%, and Na₂O and K₂A glass containing 12 to 20% by weight of O and less than 1% by weight of CaO.

(5) Containing SiO₂ 65～75％、Al₂O₃0.1 to 5%, 1 to 6% of MgO, 1 to 15% of CaO, and Na₂O and K₂Glass containing 10 to 18% of total O.

(6) Containing SiO₂ 60～72％、Al₂O₃ 1～10％、MgO 5～12％、CaO 0.1～5％、Na₂O 13～19％、K₂0 to 5% of O, and RO/(RO + R)₂O) is 0.20 to 0.42 (in the formula, RO represents the total content of alkaline earth metal oxides, R₂O represents the total content of alkali metal oxides. ) The glass of (2).

(7) Containing SiO₂ 55.5～80％、Al₂O₃ 12～20％、Na₂O 8～25％、P₂O₅2.5% or more, and alkaline earth metal RO (RO is MgO + CaO + SrO + BaO) 1% or more.

(8) Containing SiO₂ 57～76.5％、Al₂O₃ 12～18％、Na₂O 8～25％、P₂O₅2.5-10% of glass and more than 1% of alkaline earth metal RO.

(9) Containing SiO₂ 56～72％、Al₂O₃ 8～20％、B₂O₃ 3～20％、Na₂O 8～25％、K₂O 0～5％、MgO 0～15％、CaO 0～15％、SrO₂0 to 15%, BaO 0 to 15%, and ZrO₂0 to 8% of glass.

(2) Cutting step

The cutting step is a step of cutting the obtained glass for chemical strengthening into a desired size, and includes a step of cutting the glass for chemical strengthening by chemical etching or short pulse laser. When glass is cut by chemical etching or short-pulse laser, microcracks are less likely to occur at the end faces (cut sections), and therefore high-strength glass can be obtained.

When the glass for chemical strengthening is cut by chemical etching, first, resist materials are applied to both surfaces of the glass for chemical strengthening, the resist materials are exposed through a photomask having a desired shape pattern, and the exposed resist materials are developed to form resist patterns in regions other than the etched regions. Subsequently, the etched region is etched to cut the chemical strengthening glass.

The etchant is not particularly limited as long as it can etch and cut glass, and for example, one obtained by adding at least one acid selected from sulfuric acid, nitric acid, hydrochloric acid, and fluorosilicic acid to hydrofluoric acid can be used. The resist material is not particularly limited as long as it is resistant to an etchant, and can be appropriately selected from known materials. Examples of the stripping solution for the resist material include alkali solutions such as KOH and NaOH.

In addition, although the above-described etching cutting step is an example in which wet etching is employed, dry etching using fluorine gas may be employed. When the glass is cut by chemical etching in this way, the glass having extremely few microcracks at the end face (cut section) and extremely high smoothness can be obtained.

When the glass for chemical strengthening is cut with a short-pulse laser, the glass is cut with a known device using a picosecond laser, a femtosecond laser, an attosecond laser, or the like as the short-pulse laser. Thus, when the glass is cut with the short pulse laser, the glass having extremely few microcracks on the end face and extremely high smoothness can be obtained.

After the cutting step and before the chemical strengthening treatment step, a step of performing chemical etching so that the end face becomes an arc (end face treatment step) may be performed.

For example, the end face of glass cut by chemical etching may have a sharp shape because it is isotropically etched from both surfaces. In this case, since the end face may be easily broken, it is preferable to make the end face have a sufficiently round shape by the end face treatment step.

(3) Bending process

In the bending step, the chemically strengthened glass that has been cut is subjected to bending processing to impart a bent shape. The method of bending is not particularly limited. For example, the glass for chemical strengthening can be bent by performing a heat treatment in a state where the glass is bent at a desired angle and curvature. The heating temperature and heating time in the bending process may be appropriately adjusted. A method of heating the glass to a temperature higher than the glass transition point and molding the glass with a mold can be employed.

In the case where the chemical strengthening treatment step (4) is performed first and then the bending step (3) is performed, the chemically strengthened glass is subjected to the step (3). The method of the bending step in this case is the same as in the case of the above-described glass for chemical strengthening.

(4) Chemical strengthening treatment step

The chemical strengthening treatment is performed by bringing the chemical strengthening glass subjected to bending processing into contact with an inorganic salt composition containing other alkali metal ions having a larger ionic radius than the alkali metal ions contained in the glass. By this treatment, alkali metal ions (Li ions and/or Na ions) contained in the glass are exchanged for large alkali metal ions (Na ions and/or K ions) contained in the inorganic salt composition, and a high-density compressive stress layer is formed.

The density of the chemically strengthened glass gradually increases from the outer edge of the region (intermediate layer) present in the center of the glass and not subjected to ion exchange to the surface of the compressive stress layer, and therefore there is no clear boundary at which the density rapidly changes between the intermediate layer and the compressive stress layer. In the case where the chemical strengthening treatment step (4) is performed first and then the bending step (3) is performed, the chemical strengthening glass that has not been subjected to the bending process is subjected to the step (4). The method of the chemical strengthening treatment step in this case is the same as in the case of the glass for chemical strengthening subjected to bending.

Examples of the method of bringing the inorganic salt composition into contact with the glass for chemical strengthening include a method of applying a paste-like inorganic salt composition to the glass for chemical strengthening, a method of spraying an aqueous solution of an inorganic salt composition onto the glass for chemical strengthening, and a method of immersing the glass for chemical strengthening in an inorganic salt composition (hereinafter also referred to as "molten salt") which is heated to a melting point or higher and melted. Among these methods, a method of immersing the glass for chemical strengthening in a molten salt is preferable.

When the glass for chemical strengthening contains Na ions, potassium nitrate (KNO) may be used₃) And further contains a compound selected from the group consisting of K₂CO₃、Na₂CO₃、KHCO₃、NaHCO₃、K₃PO₄、Na₃PO₄、K₂SO₄、Na₂SO₄Of the group consisting of KOH and NaOHAn inorganic salt composition of at least one flux.

The melting point of potassium nitrate is 330 ℃ and is lower than the strain point (usually 500 to 600 ℃) of the glass for chemical strengthening.

When a chemical strengthening treatment is performed by immersing a glass for chemical strengthening in a molten salt, the glass for chemical strengthening is preheated to, for example, 100 ℃ or higher, immersed in the molten salt heated to a predetermined temperature for a predetermined time, then pulled out of the molten salt, and naturally cooled.

The chemical strengthening temperature may be set to a strain point (usually 500 to 600 ℃) of the glass for chemical strengthening, and is preferably 350 ℃ or higher for obtaining a deep compressive stress layer, and more preferably 400 ℃ or higher, and still more preferably 430 ℃ or higher for shortening the treatment time and forming a low-density layer.

The immersion time of the glass for chemical strengthening in the molten salt is preferably 1 minute to 10 hours, more preferably 5 minutes or more, further preferably 10 minutes or more, further preferably 8 hours or less, further preferably 4 hours or less, in consideration of the balance between the strength of the obtained chemically strengthened glass and the depth of layer of compressive stress.

In the method for producing a glass for chemical strengthening, it is preferable that the step of cleaning the glass (cleaning step) is provided after the chemical strengthening treatment step. In the cleaning step, the glass is cleaned with industrial water, ion-exchanged water, or the like, which is treated as necessary, and it is particularly preferable to use ion-exchanged water. The preferable cleaning conditions vary depending on the cleaning liquid used, and for example, when ion-exchanged water is used, cleaning is preferably performed at 0 to 100 ℃. The cleaning step can be performed by various methods such as the following method: a method of immersing the chemically strengthened glass in a water tank containing ion-exchanged water or the like, a method of exposing the glass surface to flowing water, a method of spraying a cleaning liquid onto the glass surface by spraying, and the like.

Examples

(example 1)

A flat alkali-containing glass having a short side of 60mm, a long side of 120mm and a thickness of 0.05mm was subjected to chemical strengthening treatment so that the compressive stress value of the surface became 900MPa and the thickness of the compressive stress layer became 7 μm. The obtained chemically strengthened glass was heated, and was bent using a mold so that the angle θ formed by the 1 st point, the 5 th point, and the 2 nd point was 90 °, to produce a bent rectangular chemically strengthened glass. The recovery force at 10mm bending of the obtained chemically strengthened glass was measured, and as a result, the recovery force at 10mm bending was 0.41 kgf.

Comparative example 1

A flat rectangular chemically strengthened glass sheet was produced in the same manner as in example 1, except that the glass sheet was not bent. The recovery force at 10mm bending of the obtained chemically strengthened glass was measured, and as a result, the recovery force at 10mm bending was 1.22 kgf.

Thus, the chemically strengthened glass subjected to bending can reduce the restoring force when bent.

The present invention is described in detail with reference to specific embodiments, but it is obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. The present application is based on japanese patent application No. 3/18 in 2019 (japanese application No. 2019-050003), the contents of which are incorporated herein by reference.

Description of the reference numerals

1 chemically strengthened glass (cover glass),

1a, 1b chemically strengthening the ends of the glass,

2 the 1 st main surface,

2a one end portion of the 1 st main surface which is not bent,

2b the other end portion of the 1 st main surface which is not bent,

3 the 2 nd main surface,

3a one end portion of the 2 nd main surface which is not bent,

3b the other end portion of the 2 nd main surface which is not bent,

P1 point 1,

P2 point 2,

P3 point 3,

P4 point 4,

P5 point 5,

5 a foldable device,

6a shell body,

6a deformation part,

7a flexible display,

12 a substrate,

14 th 1 support disk (upper support disk),

14a support surface of the 1 st support plate,

16 nd 2 support plate (lower support plate),

16a support surface of the 2 nd support plate,

17a, 17b stop,

50 a supporting part,

52 a connecting part,

60 a carrying part,

62 bolts,

62a head of the bolt,

62b a shaft portion of the bolt,

300 an adjusting part.