JP7782191B2 - Glass substrate, glass laminate, display device and electronic device - Google Patents

Description

This disclosure relates to glass substrates, glass laminates using the same, display devices, and electronic devices.

Traditionally, display devices have used glass or resin cover members to protect them. These cover members protect the display device from impacts and scratches, and are required to have strength, impact resistance, scratch resistance, etc. Glass cover members are characterized by high surface hardness, scratch resistance, and high transparency, while resin cover members are characterized by being lightweight and shatter-resistant. In general, the thicker the cover member, the better it protects the display device from impacts, and the material and thickness of the cover member are selected appropriately based on weight, cost, display size, etc.

In recent years, there has been active development of flexible displays such as foldable displays, rollable displays, and bendable displays, and in particular, the development of foldable displays, i.e., display devices that can be bent, is progressing rapidly.

In bendable display devices, the cover member must also bend in accordance with the movement of the display device, and so a bendable cover member is used. For resin cover members, colorless and transparent polyimide and polyamide-imide films have been developed through ingenious chemical structure (see, for example, Patent Document 1). For glass cover members, research is underway into bendable cover members made by thinning the glass, such as ultra-thin glass (UTG) (see, for example, Patent Documents 2 to 5). Among glass types, chemically strengthened glass has particularly high bending resistance. By incorporating expansion stress into the glass surface, minute scratches on the glass surface do not become larger when bent, making the glass less likely to break.

Japanese Patent Application Laid-Open No. 2019-137864 Special Publication No. 2020-521699 International Publication No. 2016/194785 Special table 2016-508954 publication International Publication No. 2020/095415

However, the thinner the glass substrate, the lower its impact resistance, especially at the edges. In particular, when chemically strengthened glass is cut, the compressive stress layer formed on the surface of the chemically strengthened glass is absent at the cut surface of the glass substrate, resulting in a decrease in strength at the cut surface of the glass substrate.

The present disclosure has been made in light of the above-mentioned circumstances, and its primary objective is to provide a glass substrate and a glass laminate that have good bending resistance and edge impact resistance.

One embodiment of the present disclosure provides a glass substrate having a first surface, a second surface opposing the first surface, and a side surface connecting the first surface and the second surface, wherein the thickness of the glass substrate is 100 μm or less, the side surface is connected to the first surface, and has an inclined portion extending outward from an end of the first surface at an angle toward the second surface relative to the first surface, the width of the inclined portion in the first surface direction of the glass substrate being 0.05 μm or more and 9.00 μm or less, and the length of the inclined portion in the thickness direction of the glass substrate being 0.05 μm or more and 5.00 μm or less.

In the glass substrate of the present disclosure, it is preferable that the ratio (a/b) of the width a of the inclined portion in the first surface direction of the glass substrate to the length b of the inclined portion in the thickness direction of the glass substrate is 1.8 or greater and 20.0 or less.

Furthermore, in the glass substrate of the present disclosure, it is preferable that the inclined portion has a curved surface that is convex outward.

Furthermore, in the glass substrate of the present disclosure, it is preferable that the maximum height Sz of the side surface be 1.5 μm or less.

Furthermore, in the glass substrate according to the present disclosure, when the regions formed by dividing the side surface into ten equal parts in the thickness direction are designated as first to tenth regions in the order from the first surface side to the second surface side, and when the maximum heights of the first to tenth regions of the side surface are designated as Sz1 to Sz10 in the order from the first region to the tenth region, respectively, it is preferable that the relationships of the following formulas (1) to (3) are satisfied.
Sz1>Sz4 (1)
Sz1>Sz5 (2)
Sz1>Sz6 (3)

Furthermore, in the glass substrate of the present disclosure, it is preferable that the side surface has a flat portion connecting the inclined portion and the second surface.

Furthermore, the glass substrate in this disclosure is preferably chemically strengthened glass.

Furthermore, the glass substrate of the present disclosure is preferably used in a foldable display device in which the first surface of the glass substrate faces outward.

Another embodiment of the present disclosure provides a glass laminate having the above-mentioned glass substrate and a resin layer disposed on at least one of the first surface side and the second surface side of the glass substrate.

In the glass laminate of the present disclosure, it is preferable that the resin layer is disposed on the second surface side of the glass substrate.

Furthermore, it is preferable that the glass laminate disclosed herein has a total light transmittance of 85% or more and a haze of 1.5% or less.

Another embodiment of the present disclosure provides a display device comprising a display panel and the above-described glass substrate or the above-described glass laminate disposed on the viewer side of the display panel.

The display device of the present disclosure is preferably foldable so that the first surface of the glass substrate faces outward.

Another embodiment of the present disclosure provides an electronic device including the above-described display device.

The present disclosure has the effect of providing glass substrates and glass laminates that have good bending resistance and edge impact resistance.

FIG. 1 is a schematic cross-sectional view illustrating a glass substrate according to the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a glass substrate according to the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a glass substrate according to the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a glass substrate according to the present disclosure. FIG. 1 is a schematic plan view illustrating a glass substrate according to the present disclosure. FIG. 1 is a schematic perspective view illustrating a glass substrate according to the present disclosure. FIG. 1 is a schematic cross-sectional view illustrating a glass substrate according to the present disclosure. FIG. 1 is a schematic diagram for explaining a U-shaped bending test. 1 is a schematic cross-sectional view illustrating a glass laminate according to the present disclosure. 1 is a schematic cross-sectional view illustrating a glass laminate according to the present disclosure. 1 is a schematic cross-sectional view illustrating a glass laminate according to the present disclosure. 1 is a schematic cross-sectional view illustrating a display device according to the present disclosure. FIG. 1 is a schematic diagram for explaining an impact test. FIG. 10 is an explanatory diagram illustrating a method for measuring the maximum height Sz.

Embodiments of the present disclosure are described below with reference to the drawings. However, the present disclosure can be implemented in many different forms, and should not be construed as being limited to the description of the embodiments exemplified below. Furthermore, to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual form, but these are merely examples and do not limit the interpretation of the present disclosure. Furthermore, in this specification and each figure, elements similar to those previously described with reference to the previous figures are designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

In this specification, when describing the arrangement of another component on a component, the terms "above" or "below" are used, unless otherwise specified, to include both the case where another component is placed directly above or below the component so as to be in contact with the component, and the case where another component is placed above or below the component with another component interposed between them. Furthermore, in this specification, when describing the arrangement of another component on the surface of a component, the terms "on the surface side" or "on the surface" are used, unless otherwise specified, to include both the case where another component is placed directly above or below the component so as to be in contact with the component, and the case where another component is placed above or below the component with another component interposed between them.

The glass substrate, glass laminate, display device, and electronic device described herein are described in detail below.

A. Glass Substrate The glass substrate in the present disclosure is a glass substrate having a first surface (hereinafter sometimes referred to as a first main surface), a second surface (hereinafter sometimes referred to as a second main surface) facing the first main surface, and a side surface connecting the first main surface and the second main surface, the glass substrate having a thickness of 100 μm or less, the side surface being connected to the first main surface and having an inclined portion extending outward from an end of the first main surface at an angle toward the second main surface with respect to the first main surface, the inclined portion having a width of 0.05 μm or more and 9.00 μm or less in the first main surface direction of the glass substrate, and the length of the inclined portion in the thickness direction of the glass substrate being 0.05 μm or more and 5.00 μm or less.

Here, in the present disclosure, "connected" refers to a state in which a predetermined member is disposed in contact with a predetermined surface (including an inclined portion).
In the present disclosure, the "side surface" of the glass substrate refers to all surfaces of the glass substrate other than the first and second main surfaces. The "side surface" also includes the "inclined portion."

1 and 2 are schematic cross-sectional views showing an example of a glass substrate according to the present disclosure, and FIG. 2 is an enlarged view of FIG. 1. As shown in FIGS. 1 and 2, glass substrate 1 has a first major surface 1A, a second major surface 1B opposing first major surface 1A, and a side surface 1C connecting first major surface 1A and second major surface 1B, and has a thickness T of a predetermined value or less. Side surface 1C of glass substrate 1 is connected to first major surface 1A and has an inclined portion 2a extending outward from the end of first major surface 1A at an angle toward second major surface 1B relative to first major surface 1A. The width a of inclined portion 2a in the direction of the first major surface of glass substrate 1 is within a predetermined range, and the length b of inclined portion 2a in the thickness direction of glass substrate 1 is within a predetermined range. Furthermore, in FIGS. 1 and 2, side surface 1C of glass substrate 1 has a flat portion 2b connecting inclined portion 2a and second major surface 1B.

Note that the "end of the first surface" refers to the boundary between the first surface and the inclined portion of the side surface. For example, in Figure 2, the end of the first surface 1A is the boundary between the first surface 1A and the inclined portion 2a of the side surface 1C.

Additionally, the term "outside" in "from the end of the first surface to the outside" refers to the side of the flat surface of the side surface opposite to the glass substrate.
Furthermore, the "first surface direction of the glass substrate" in "the first surface direction of the glass substrate of the inclined portion" refers to a direction perpendicular to the thickness direction of the glass substrate.

The glass substrate disclosed herein has a thin thickness of less than a predetermined value, which allows for high flexibility and improved bending resistance. However, glass substrates are prone to microcracks during processing, particularly at the edges of the glass substrate when it is cut. Microcracks in the glass substrate make it more likely for cracks to occur starting from these microcracks. Furthermore, using chemically strengthened glass as the glass substrate can improve bending resistance and impact resistance. However, even in this case, when cutting a glass substrate made of chemically strengthened glass, the compressive stress layer formed on the surface of the chemically strengthened glass is not present on the cut surface of the glass substrate, i.e., the side surface, resulting in reduced strength on the side surface of the glass substrate.

In contrast, in the present disclosure, the side surface 1C of the glass substrate 1 has an inclined portion 2a. The width a of this inclined portion 2a in the direction of the first principal surface of the glass substrate 1 and the length b of this inclined portion 2a in the thickness direction of the glass substrate 1 are within a predetermined range, thereby improving the impact resistance of the edge of the glass substrate. While the reason for this is unclear, it is presumed as follows: The inclined portion 2a on the side surface 1C can prevent stress from concentrating on the corner of the glass substrate when the edge of the glass substrate is subjected to an impact. Furthermore, the length b of the inclined portion 2a in the thickness direction of the glass substrate 1 is within a predetermined range and is relatively small, thereby enabling the area of the flat portion 2b on the side surface 1C of the glass substrate 1 to be relatively large. Furthermore, the width a of the inclined portion 2a in the direction of the first principal surface of the glass substrate 1 is within a predetermined range and is relatively small, thereby enabling the area of the edge of the glass substrate 1 where the thickness is thinner than the thickness T, which is the length between the first principal surface 1A and the second principal surface 1B, to be relatively small. This increases the strength of the edge of the glass substrate, thereby improving the impact resistance of the edge of the glass substrate.

Accordingly, the present disclosure makes it possible to produce a glass substrate with excellent bending resistance and edge impact resistance. Therefore, the glass substrate of the present disclosure can be bent and used in a wide variety of display devices, and can be used, for example, as a component for a foldable display.

The thickness of the glass substrate is 100 μm or less, preferably 15 μm or more and 100 μm or less, more preferably 20 μm or more and 90 μm or less, and even more preferably 25 μm or more and 80 μm or less. A thin glass substrate within the above range can provide good flexibility and sufficient hardness. It can also suppress curling of the glass substrate. Furthermore, this is preferable in terms of reducing the weight of the glass substrate.
The thickness of the glass substrate refers to the length between the first and second main surfaces of the glass substrate.

In the glass substrate, the inclined portion 2a may have a flat surface, as shown in Figure 2, or may have an outwardly convex curved surface, as shown in Figure 3. In particular, it is preferable for the inclined portion to have an outwardly convex curved surface. This is because it can effectively prevent stress from concentrating at the corners of the glass substrate when the edge of the glass substrate is subjected to an impact.

Note that the "outside" in "outwardly convex curved surface" refers to the side opposite the glass substrate itself, when a plane is imagined connecting the boundary between the inclined portion and the first surface and the boundary between the inclined portion and the side surface perpendicular to the first surface.

In the glass substrate, the width a of the inclined portion in the direction of the first principal surface of the glass substrate is 0.05 μm or more, and preferably 0.5 μm or more. If the width a of the inclined portion in the direction of the first principal surface of the glass substrate is too small, stress is likely to concentrate at the corners of the glass substrate when the edge of the glass substrate receives an impact, which may result in cracking. On the other hand, the width a of the inclined portion in the direction of the first principal surface of the glass substrate is 9.00 μm or less, and preferably 5.0 μm or less. By having the width a of the inclined portion in the direction of the first principal surface of the glass substrate within the above range and being relatively small, the thin portions of the glass substrate at the edge of the glass substrate can be made relatively small, thereby increasing the strength of the edge of the glass substrate.

Furthermore, in the glass substrate, the length b of the inclined portion in the thickness direction of the glass substrate can be 0.05 μm or more, and preferably 0.1 μm or more. If the length b of the inclined portion in the thickness direction of the glass substrate is too small, stress is likely to concentrate at the corners of the glass substrate when the edge of the glass substrate receives an impact, which may result in cracks. On the other hand, the length b of the inclined portion in the thickness direction of the glass substrate can be 5.00 μm or less, and preferably 2.0 μm or less. By having the length b of the inclined portion in the thickness direction of the glass substrate within the above range and being relatively small, the area of the flat portion on the side surface can be relatively large, and the strength of the edge of the glass substrate can be increased.

In the present disclosure, one method for setting the width a and length b within the above-mentioned predetermined ranges is to use a polishing process in the processing step of the manufacturing method described below. Adjustments can also be made by changing the cutter pressure during cutting and the tempering conditions for chemically tempered glass.

Specifically, increasing the cutter pressure during cutting tends to increase a and decrease b. Furthermore, by setting the tempering conditions for chemically strengthened glass to conditions that increase the surface stress value and increase the thickness of the strengthened layer, a and b tend to decrease. In this disclosure, it is possible to adjust a and b in this way.

Furthermore, as described below, when the glass substrate is chemically strengthened glass, the ratio (a/b) of the width a of the inclined portion in the first principal surface direction of the glass substrate to the length b of the inclined portion in the thickness direction of the glass substrate is preferably 1.8 or more, and more preferably 2.3 or more. By having a/b in the above range, the slope of the inclined portion can be made relatively gentle.

Here, in the manufacturing process of a glass substrate, for example, if chemical strengthening treatment and cutting are performed in that order, no compressive stress layer will be present on the side of the glass substrate. In this case, if a/b is smaller than the above range and the inclination of the inclined portion is relatively steep, the area where the compressive stress layer 3 is not present tends to be relatively large on the flat portion 2b of the side surface 1C of the glass substrate 1, as shown in Figure 4(a), for example. In contrast, if a/b is within the above range and the inclination of the inclined portion is relatively gentle, it is easier to ensure an area where the compressive stress layer 3 is present on the flat portion 2b of the side surface 1C of the glass substrate 1, as shown in Figure 4(b), for example. Therefore, in the above case, it is presumed that having a/b in the above range can improve the impact resistance of the edge of the glass substrate.

Furthermore, if the manufacturing process for a glass substrate involves, for example, cutting and chemical strengthening in that order, a compressive stress layer will also be present on the side of the glass substrate. In this case, if a/b is smaller than the above range and the slope of the inclined portion is relatively steep, the compressive stress tends to be generated unevenly in the compressive stress layer formed on the side of the glass substrate. Uneven compressive stress is likely to leave residual distortion, which is thought to affect fracture. In contrast, if a/b is within the above range and the slope of the inclined portion is relatively gentle, the compressive stress tends to be uniform in the compressive stress layer formed on the side of the glass substrate. Therefore, even in the above case, it is believed that keeping a/b within the above range can improve the impact resistance of the edge of the glass substrate.

Furthermore, when the glass substrate is chemically strengthened glass, the ratio (a/b) of the width a of the inclined portion in the first principal surface direction of the glass substrate to the length b of the inclined portion in the thickness direction of the glass substrate is, for example, preferably 20.0 or less, more preferably 10.0 or less. If a/b is too large, the slope of the inclined portion becomes too gentle, and when the end of the glass substrate is impacted, stress is likely to concentrate at the corners of the glass substrate, which may cause cracks.
In the present disclosure, the above a/b is preferably in the range of 1.8 to 20.0, and particularly preferably in the range of 2.3 to 10.0.

Here, the width a of the inclined portion in the direction of the first principal surface of the glass substrate refers to the width of the inclined portion 2a when the glass substrate 1 is viewed in a plan view in the thickness direction, as shown in Figures 5(a) and 5(b), for example. If the inclined portion is a curved surface that convex outward, as shown in Figure 3, for example, the boundary between the first principal surface 1A and the inclined portion 2a is the boundary between the flat surface that constitutes the first principal surface 1A and the curved surface that constitutes the inclined portion 2a; that is, the R of the curved surface that constitutes the inclined portion 2a ends at the R on the first principal surface 1A side. Note that Figure 1 corresponds to the cross-sectional view taken along line A-A in Figure 5(a), and also corresponds to the cross-sectional views taken along lines A-A and B-B in Figure 5(b).

Furthermore, the length b of the inclined portion in the thickness direction of the glass substrate refers to the height of the inclined portion 2a, as shown in Figures 2 and 3, for example. If the inclined portion is a curved surface that convex outward, as shown in Figure 3, for example, the boundary between the inclined portion 2a and the flat portion 2b is the boundary between the curved surface that makes up the inclined portion 2a and the flat surface that makes up the flat portion 2b; in other words, the R of the curved surface that makes up the inclined portion 2a ends at the flat portion 2b side.

In the glass substrate, it is sufficient that at least some of the side surfaces have the inclined portion; for example, all of the side surfaces may have the inclined portion, or only some of the side surfaces may have the inclined portion. Furthermore, if the glass substrate is rectangular, it is sufficient that at least one of the four side surfaces has the inclined portion; for example, two opposing side surfaces may have the inclined portion, or all four side surfaces may have the inclined portion.

When the glass substrate is rectangular, it is preferable that two of the four opposing side surfaces have the above-mentioned inclined portions. For example, as shown in Figures 6(a) and (b), when the glass substrate 1 is bent, the bent portion F1 of the glass substrate 1 is likely to crack if it receives an impact. Therefore, by having two of the four side surfaces of the glass substrate that are approximately parallel to the bending direction D1 of the glass substrate 1 have the above-mentioned inclined portions, the strength of the bent portion of the glass substrate can be increased, and the impact resistance of the bent portion can be improved.

Furthermore, when the glass substrate has a rectangular shape when viewed in a plan view from the thickness direction, it is preferable that, of the four side surfaces of the glass substrate, two side surfaces that are approximately parallel to the long side direction of the glass substrate have the above-mentioned inclined portions 2a, as shown in FIG. 5(a), for example. For example, as shown in FIGS. 6(a) and 6(b), when bending the glass substrate 1, the bending direction D1 of the glass substrate 1 is often made approximately parallel to the long side direction of the glass substrate because it is easy to bend. Therefore, by having the above-mentioned inclined portions on two side surfaces that are approximately parallel to the long side direction of the glass substrate, the strength of the bent portion of the glass substrate can be increased, and the impact resistance of the bent portion can be improved.

Furthermore, for the reasons mentioned above, it is preferable that of the four side surfaces of the glass substrate, two side surfaces that are approximately parallel to the bending direction of the glass substrate have the above-mentioned inclined portions.

In particular, it is preferable that all four side surfaces of the glass substrate have the above-mentioned inclined portions, as shown in Figure 5(b), for example. This can improve the impact resistance of the edge of the glass substrate.

Furthermore, the side surface of the glass substrate needs to have at least an inclined portion, but it is preferable that it has an inclined portion and a flat portion connecting the inclined portion and the second main surface.

Here, since the side surface of the glass substrate has an inclined portion connected to the first main surface, when the glass substrate is folded so that the first main surface faces outward, the inclined portion faces outward. If the glass substrate is chemically strengthened glass, the compressive stress layer is thinner at the inclined portion, and the compressive stress value is lower on the first side of the glass substrate than on the second side. The lower the compressive stress value, the easier it is to bend. Therefore, when folding so that the inclined portion faces outward, it is easier to bend and has better bending resistance than when folding so that the inclined portion faces inward. Therefore, when the side surface of the glass substrate has an inclined portion and a flat portion connecting the inclined portion and the second main surface, when the glass substrate is folded so that the first main surface faces outward, it has better bending resistance than when folding so that the second main surface faces outward.

On the other hand, if the side of the glass substrate has, for example, a first inclined portion connected to the first main surface, a second inclined portion connected to the second main surface, and a flat portion connected to the first inclined portion and the second inclined portion, when the glass substrate is folded so that the first main surface faces outward, the first inclined portion faces outward and the second inclined portion faces inward; and when the glass substrate is folded so that the second main surface faces outward, the first inclined portion faces inward and the second inclined portion faces outward. Therefore, when the side surface of the glass substrate has, for example, a first inclined portion connecting to the first main surface, a second inclined portion connecting to the second main surface, and a flat portion connecting to the first inclined portion and the second inclined portion, the bending resistance when the glass substrate is folded so that the first main surface faces outward and the bending resistance when the glass substrate is folded so that the second main surface faces outward are expected to be similar to the bending resistance when the side surface of the glass substrate has an inclined portion and a flat portion connecting the inclined portion and the second main surface and is folded so that the inclined portion faces inward.

Therefore, when the side surface of the glass substrate has an inclined portion and a flat portion connecting the inclined portion and the second main surface, it is believed that the bending resistance can be improved when the glass substrate is folded so that the inclined portion faces outward, i.e., when the glass substrate is folded so that the first main surface of the glass substrate faces outward, compared to when the side surface of the glass substrate has, for example, a first inclined portion connecting to the first main surface, a second inclined portion connecting to the second main surface, and a flat portion connecting to the first inclined portion and the second inclined portion. Therefore, it is preferable that the side surface of the glass substrate have an inclined portion and a flat portion connecting the inclined portion and the second main surface.

Furthermore, the maximum height Sz of the side surface of the glass substrate is preferably, for example, 1.5 μm or less, and more preferably 1.0 μm or less. When the maximum height Sz of the side surface of the glass substrate is within the above range, the smoothness of the side surface of the glass substrate is high, thereby reducing microcracks on the side surface of the glass substrate, and as a result, the strength of the side surface of the glass substrate can be increased. This can suppress cracking from the side surface of the glass substrate when the glass substrate is bent, improving bending resistance. Furthermore, it can also improve the impact resistance of the edge of the glass substrate during the manufacture and use of the glass substrate or a display device component and display device using the glass substrate. On the other hand, the maximum height Sz of the side surface of the glass substrate is preferably 0.005 μm or more. If Sz is less than 0.005 μm, poor adhesion may occur, making it difficult to cover the edge.
In the present disclosure, the above Sz is preferably in the range of 0.005 μm to 1.5 μm, and particularly preferably in the range of 0.005 μm to 1.0 μm.

Here, the maximum height Sz is a value measured in accordance with ISO 25178. The maximum height Sz can be measured using a non-contact surface profile measuring device that employs optical interference. As an example of a non-contact surface profile measuring device that employs optical interference, the VertScan 2.0 R5500GML-A150-AC non-contact surface/layer cross-sectional shape measuring system manufactured by Ryoka Systems Co., Ltd. can be used. Details of the method for measuring the maximum height Sz will be described in the Examples section below.
In the present disclosure, Sz is a parameter for evaluating surface roughness, and is more effective for evaluating irregular surface properties than Rz, which indicates line roughness.

Furthermore, when the side surface of the glass substrate is divided into ten equal regions in the thickness direction and the regions are designated as the first region to the tenth region in the order from the first main surface side to the second main surface side, and when the maximum heights of the first region to the tenth region on the side surface are designated as Sz1 to Sz10 in the order from the first region to the tenth region, respectively, it is preferable that the relationships of the following formulas (1) to (3) are satisfied.
Sz1>Sz4 (1)
Sz1>Sz5 (2)
Sz1>Sz6 (3)
When the relationships of the above formulas (1) to (3) are satisfied, the smoothness of the central portion in the thickness direction of the side surface of the glass substrate is relatively high, thereby making it possible to suppress the progression of microcracks on the side surface of the glass substrate.

In the above case, as shown in FIG. 7, for example, the side surface 1C of the glass substrate 1 is divided into ten equal regions in the thickness direction of the glass substrate 1, and the regions are designated as the first region 4A to the tenth region 4J in order from the first main surface 1A to the second main surface 1B of the glass substrate 1. The maximum heights Sz of the first region 4A to the tenth region 4J of the side surface 1C of the glass substrate 1 are designated as Sz1 to Sz10 in order from the first region 4A to the tenth region 4J. That is, for example, the maximum height Sz of the first region 4A is designated as Sz1, the maximum height Sz of the second region 4B is designated as Sz2, and the maximum height Sz of the third region 4C is designated as Sz3.

For a glass substrate, it is sufficient that the maximum height Sz of at least some of the side surfaces is within a predetermined range. For example, the maximum height Sz of all of the side surfaces may be within a predetermined range, or the maximum height Sz of only some of the side surfaces may be within a predetermined range. Furthermore, if the glass substrate is rectangular, it is sufficient that the maximum height Sz of at least one of the four side surfaces is within a predetermined range.

When the glass substrate is rectangular, it is particularly preferable that the maximum height Sz of two opposing side surfaces of the four side surfaces be within a predetermined range. For example, as shown in Figures 6(a) and 6(b), when the glass substrate 1 is bent, cracks are likely to occur in the glass substrate 1 at the bent portion F1 of the glass substrate 1. Therefore, if the maximum heights Sz of the two side surfaces of the glass substrate 1 that are approximately parallel to the bending direction D1 of the glass substrate 1 are within the above range, cracks can be prevented from occurring in the bent portion when the glass substrate is bent, and bending resistance can be improved.

Furthermore, when the glass substrate has a rectangular shape when viewed in a plan view from the thickness direction, it is preferable that the maximum height Sz of two of the four side surfaces of the glass substrate that are approximately parallel to the long side direction of the glass substrate be within the above range. For example, as shown in Figures 6(a) and 6(b), when bending the glass substrate 1, the bending direction D1 of the glass substrate 1 is often made approximately parallel to the long side direction of the glass substrate because it is easy to bend. Therefore, if the maximum height Sz of two of the four side surfaces of the glass substrate that are approximately parallel to the long side direction of the glass substrate are within the above range, cracks can be suppressed from occurring in the bent portion of the glass substrate when the glass substrate is bent, and bending resistance can be improved.

Furthermore, for the reasons mentioned above, it is preferable that the maximum height Sz of the two side surfaces of the glass substrate that are approximately parallel to the bending direction of the glass substrate be within the above range.

In particular, it is preferable that the maximum heights Sz of all four side surfaces of the glass substrate are within a specified range. This can further reduce cracking of the glass substrate when it is bent, further improving its bending resistance. Furthermore, it can improve the impact resistance of the edges of the glass substrate.

The glass that constitutes the glass substrate is not particularly limited, but chemically strengthened glass is preferable. Chemically strengthened glass has better impact resistance and bending resistance than non-strengthened glass. Chemically strengthened glass also has excellent mechanical strength, which makes it preferable in that it can be made thinner.

Chemically strengthened glass is typically glass whose mechanical properties are strengthened by chemical methods, such as partially exchanging sodium ions for potassium ions near the surface of the glass, and has a compressive stress layer on the surface. In other words, chemically strengthened glass has a high potassium content on the surface, and is subjected to compressive stress on the surface.

Examples of glass that can be used to make chemically strengthened glass substrates include aluminosilicate glass, soda-lime glass, borosilicate glass, lead glass, alkali barium glass, and aluminoborosilicate glass.

Commercially available chemically strengthened glass substrates include, for example, Corning's Gorilla Glass, AGC's Dragontrail, and Schott's chemically strengthened glass.

The glass substrate in this disclosure preferably has flex resistance. Specifically, the flex resistance of the glass substrate can be evaluated by performing the U-shaped flex test described below.

The U-shaped bending test is performed as follows. First, a glass substrate test piece measuring 20 mm x 100 mm is prepared. Next, as shown in Figure 8(a), the short side 1P of the glass substrate 1 and the short side 1Q opposite the short side 1P are fixed by parallel-arranged fixing parts 100A and 100B, respectively. As shown in Figure 8(a), fixing part 100B is slidable horizontally. Next, as shown in Figure 8(b), fixing part 100B is moved closer to fixing part 100A, thereby bending the glass substrate 1 into a U-shape. Furthermore, as shown in Figure 8(c), fixing part 100B is moved to gradually reduce the distance d between the two opposing short sides 1P and 1Q of the glass substrate 1 fixed by fixing parts 100A and 100B until cracks or fractures occur in the glass substrate 1. At this time, the bending test is performed so that the bent portion 1R of the glass substrate 1 does not protrude from the bottom ends of the fixed portions 100A and 100B. For example, if the distance d between the two opposing short side portions 1P and 1Q is 10 mm, the outer diameter of the bent portion 1R is considered to be 10 mm.

In the above U-bend test, the distance d between the opposing short sides 1P and 1Q of the glass substrate 1 when cracks or breakage occurs is preferably 10 mm or less, more preferably 8 mm or less, and most preferably 5 mm or less. The smaller the distance d between the opposing short sides 1P and 1Q of the glass substrate 1, the higher the bending resistance.

As described above, when the glass substrate is folded so that the first main surface faces outward, the bending resistance is higher than when the glass substrate is folded so that the second main surface faces outward.
Therefore, in the U-shaped bending test, it is preferable that the glass substrate has the above-mentioned bending resistance when folded so that the first main surface of the glass substrate faces outward. In particular, it is more preferable that the glass substrate has the above-mentioned bending resistance when folded so that the first main surface of the glass substrate faces outward and when folded so that the first main surface of the glass substrate faces inward.

The bending resistance of a glass substrate can also be evaluated by conducting a dynamic bending test. In a dynamic bending test, the distance d between the opposing short sides 1P and 1Q of the glass substrate 1 is set to a predetermined value in the U-bending test described above, and the glass substrate is repeatedly bent.

In the dynamic bending test described above, it is preferable that the glass substrate does not crack or break when the operation of bending the glass substrate 1 by 180° so that the distance d between the opposing short sides 1P and 1Q of the glass substrate 1 is 12 mm is repeated 200,000 times.

In addition, when the number of samples in the dynamic bending test is 10, it is preferable that the pass rate calculated by the following formula from the total number of samples (10) and the number of samples in which cracks or breaks did not occur in the glass substrate is 80% or more.
Pass rate (%) = (number of samples in which the glass substrate was not cracked or broken) / 10 x 100

Furthermore, bending resistance can be improved by reducing the thickness of the glass substrate.

For example, if the thickness of the glass substrate is 81 μm or more and 100 μm or less, it is preferable that the glass substrate does not crack or break when the above-mentioned dynamic bending test involves repeatedly bending the glass substrate 1 by 180° 200,000 times so that the distance d between the opposing short sides 1P and 1Q of the glass substrate 1 is 12 mm.

Furthermore, for example, when the thickness of the glass substrate is 50 μm or more and 81 μm or less, it is preferable that the glass substrate does not crack or break when the above-mentioned dynamic bending test involves repeatedly bending the glass substrate 1 by 180° 200,000 times so that the distance d between the opposing short sides 1P and 1Q of the glass substrate 1 is 10 mm.

Furthermore, for example, when the thickness of the glass substrate is 50 μm or less, it is preferable that the glass substrate does not crack or break when the above-mentioned dynamic bending test involves repeatedly bending the glass substrate 1 by 180° 200,000 times so that the distance d between the opposing short sides 1P and 1Q of the glass substrate 1 is 8 mm.

In the dynamic bending test, as with the U-bend test described above, it is preferable that the above-mentioned bending resistance be maintained when the glass substrate is folded so that its first main surface faces outward, and it is even more preferable that the above-mentioned bending resistance be maintained both when the glass substrate is folded so that its first main surface faces outward and when it is folded so that its first main surface faces inward.

The method for manufacturing a glass substrate according to the present disclosure is not particularly limited as long as it can form an inclined portion on the side surface of the glass substrate, and can keep the width a of the inclined portion in the first principal surface direction of the glass substrate within a predetermined range, and keep the length b of the inclined portion in the thickness direction of the glass substrate within a predetermined range. For example, the method for manufacturing a glass substrate may include a cutting step of cutting the glass substrate so that an inclined portion is formed on the side surface of the glass substrate, the width a of the inclined portion in the first principal surface direction of the glass substrate falls within a predetermined range, and the length b of the inclined portion in the thickness direction of the glass substrate falls within a predetermined range. Furthermore, for example, the method for manufacturing a glass substrate may include a cutting step of cutting the glass substrate, and a processing step of processing the cut surface of the glass substrate so that an inclined portion is formed on the side surface of the glass substrate, the width a of the inclined portion in the first principal surface direction of the glass substrate falls within a predetermined range, and the length b of the inclined portion in the thickness direction of the glass substrate falls within a predetermined range. Among these, it is preferable that the method for manufacturing a glass substrate cuts the glass substrate so that an inclined portion is formed on the side surface of the glass substrate, the width a of the inclined portion in the first principal surface direction of the glass substrate falls within a predetermined range, and the length b of the inclined portion in the thickness direction of the glass substrate falls within a predetermined range.

Examples of methods for cutting glass substrates include scribing methods such as mechanical scribing using a tool or laser scribing, chemical etching, and laser cutting. Specifically, a mechanical scribing method using the "SOLID-D" cutter manufactured by Mitsuboshi Diamond Industrial Co., Ltd. is preferably used.

Furthermore, when the glass substrate is chemically strengthened glass, for example, the processes may be performed in the order of chemical strengthening treatment and cutting, or cutting and chemical strengthening treatment. When performing the chemical strengthening treatment and cutting in that order, for example, when manufacturing display device components using the glass substrate, subsequent manufacturing steps can be carried out without cutting the large glass substrate, thereby improving production efficiency.

The glass substrate according to the present disclosure can be used, for example, as a cover member for a display device. Specifically, the glass substrate according to the present disclosure can be used as a cover member for a display device used in electronic devices such as smartphones, tablet devices, wearable devices, personal computers, televisions, digital signage, public information displays (PIDs), and in-vehicle displays. In particular, the glass substrate according to the present disclosure can be preferably used for flexible displays such as foldable displays, rollable displays, and bendable displays, and is more preferably used for foldable displays.

In particular, the glass substrate of the present disclosure is preferably used in a foldable display device with the first main surface of the glass substrate facing outward. As described above, when the glass substrate is folded so that the first main surface faces outward, bending resistance is higher than when the glass substrate is folded so that the second main surface faces outward. Therefore, the glass substrate of the present disclosure is preferably used in a foldable display device with the first main surface of the glass substrate facing outward.

B. Glass Laminate A glass laminate according to the present disclosure includes the above-described glass substrate and a resin layer disposed on at least one of the first and second main surfaces of the glass substrate.

FIGS. 9 to 11 are schematic cross-sectional views showing an example of a glass laminate according to the present disclosure. As illustrated in FIG. 9, the glass laminate 10 may include a glass substrate 1 and a resin layer 11 disposed on the first main surface 1A side of the glass substrate 1. As illustrated in FIG. 10, the glass laminate 10 may include a glass substrate 1 and a resin layer 12 disposed on the second main surface 1B side of the glass substrate 1. As illustrated in FIG. 11, the glass laminate 10 may include a glass substrate 1, a resin layer 11 disposed on the first main surface 1A side of the glass substrate 1, and a resin layer 12 disposed on the second main surface 1B side of the glass substrate 1.

The glass laminate of the present disclosure has the above-mentioned glass substrate, which allows for improved bending resistance and edge impact resistance. Therefore, the glass laminate of the present disclosure is bendable and can be used in a wide variety of display devices, such as a foldable display component.

The following describes each component of the glass laminate in this disclosure.

1. Glass Substrate The glass substrate used in the glass laminate of the present disclosure is the same as that described in the above section "A. Glass Substrate," and therefore, description thereof will be omitted here.

2. Resin Layer The resin layer in the present disclosure is a layer disposed on at least one of the first and second main surfaces of the glass substrate.

Examples of resin layers include impact absorbing layers, shatterproof layers, hard coat layers, protective layers, anti-reflection layers, low-reflection layers, anti-glare layers, anti-static layers, and decorative layers.

The resin layer may be a single layer or may have multiple layers. The resin layer may be a layer with a single function or may have multiple layers with different functions.

In the glass laminate of the present disclosure, the resin layer may be disposed on at least one of the first and second main surfaces of the glass substrate. For example, it may be disposed only on the first main surface of the glass substrate, only on the second main surface of the glass substrate, or on both the first and second main surfaces of the glass substrate. Of these, the resin layer is preferably disposed on the second main surface of the glass substrate. When the resin layer is disposed on the second main surface of the glass substrate, in manufacturing the glass laminate, for example, the resin layer can be formed on the glass substrate and then the laminate of the glass substrate and the resin layer can be cut. In this case, for example, when manufacturing a display device component using the glass laminate, subsequent manufacturing processes can be carried out without cutting large glass substrates, thereby improving production efficiency.

The material of the resin layer is appropriately selected depending on the intended function, etc. The resin contained in the resin layer may be any resin as long as it has transparency, and a general resin may be used.
For example, polyimide, polyimideamide, polyethylene terephthalate (PET), cycloolefin polymer (COP), triacetyl cellulose (TAC), acrylic resin, polycarbonate (PC), and epoxy resin are preferably used.

The resin layer may also contain additives as needed. Examples of additives include ultraviolet absorbers, light stabilizers, antioxidants, fillers, antistatic agents, antifouling agents, surfactants, lubricants, flame retardants, plasticizers, and colorants.

The thickness of the resin layer is not particularly limited as long as it provides flexibility, and can be selected appropriately depending on the intended function, etc. The thickness of the resin layer is, for example, 2 μm or more, and may be 5 μm or more, 10 μm or more, or 15 μm or more. The thickness of the resin layer is, for example, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. By making the resin layer relatively thin within the above range, flexibility can be increased, cracking of the resin layer can be suppressed when the glass laminate is bent, and flex resistance can be maintained.

The thickness of the resin layer can be the average value of thicknesses measured at any 10 locations on a cross section of the glass laminate in the thickness direction as observed with a transmission electron microscope (TEM), scanning electron microscope (SEM), or scanning transmission electron microscope (STEM). Unless otherwise specified, the same method can be used to measure the thickness of other layers in the glass laminate.

One example of a method for forming a resin layer is to apply a resin composition to a glass substrate. There are no particular limitations on the application method, as long as it allows application to the desired thickness, and examples include common application methods such as gravure coating, gravure reverse coating, gravure offset coating, spin coating, roll coating, reverse roll coating, blade coating, dip coating, and screen printing. Other methods for forming the resin layer include a transfer method in which a resin layer is transferred to one side of the glass substrate, and a method in which a film-like resin layer is attached to one side of the glass substrate via an adhesive layer.

The adhesive layer is transparent. Specifically, the total light transmittance of the adhesive layer is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more. The upper limit of the total light transmittance is 100%.

Adhesives used in the adhesive layer include, for example, pressure-sensitive adhesives such as OCA (Optical Clear Adhesive), heat seal agents, and photosensitive adhesives.

The thickness of the adhesive layer is preferably, for example, 1 μm or more and 100 μm or less. If the adhesive layer is too thick, there is a risk that its flex resistance will be impaired. On the other hand, if the adhesive layer is too thin, there is a risk that its adhesion will not be ensured and it may peel off.

3. Other Configurations In addition to the layers described above, the glass laminate according to the present disclosure may include other layers as needed. Examples of other layers include a primer layer.

The glass laminate according to the present disclosure may have a primer layer between the glass substrate and the resin layer. The primer layer can improve adhesion between the glass substrate and the resin layer.

The material for the primer layer is not particularly limited as long as it is a material that can improve adhesion between the glass substrate and the resin layer, and examples include resins. Examples of resins include (meth)acrylic resins, urethane resins, (meth)acrylic urethane copolymers, vinyl chloride-vinyl acetate copolymers, polyesters, butyral resins, chlorinated polypropylene, chlorinated polyethylene, epoxy resins, and silicone resins. These resins may be used alone or in combination of two or more.

The thickness of the primer layer should be sufficient to enhance adhesion between the glass substrate and the resin layer, and can be, for example, 0.1 μm or more and 10 μm or less, and preferably 0.2 μm or more and 5 μm or less.

One example of a method for forming a primer layer is to apply a primer layer composition to a glass substrate. Examples of application methods include common application methods such as gravure coating, gravure reverse coating, gravure offset coating, spin coating, roll coating, reverse roll coating, blade coating, dip coating, and screen printing. A transfer method can also be used to form the primer layer.

4. Properties of the Glass Laminate The glass laminate of the present disclosure preferably has a total light transmittance of, for example, 85% or more, and more preferably 88% or more. Such a high total light transmittance allows the glass laminate to have good transparency. The upper limit of the total light transmittance is 100%.

Here, the total light transmittance of the glass laminate can be measured in accordance with JIS K7361-1, for example, using a haze meter HM150 manufactured by Murakami Color Research Laboratory.

The haze of the glass laminate in the present disclosure is preferably 1.5% or less, and more preferably 1.0% or less. Such a low haze allows for a glass laminate with good transparency. The lower limit of haze is 0%.

Here, the haze of the glass laminate can be measured in accordance with JIS K-7136, for example, using a haze meter HM150 manufactured by Murakami Color Research Laboratory.

The glass laminate of the present disclosure preferably has bending resistance. Specifically, when the glass laminate is subjected to the above-described U-bend test, the distance between the opposing short sides of the glass laminate at the time when cracks or breakage occurs is preferably 10 mm or less, and more preferably 5 mm or less.

As described above, when the glass substrate is folded so that the first main surface faces outward, the bending resistance is higher than when the glass substrate is folded so that the second main surface faces outward.
Therefore, in the U-shaped bending test, it is preferable that the glass laminate have the above-mentioned bending resistance when folded so that the first main surfaces of the glass substrates face outward. In particular, it is more preferable that the glass laminate have the above-mentioned bending resistance when folded so that the first main surfaces of the glass substrates face outward and when folded so that the first main surfaces of the glass substrates face inward.

Furthermore, when the above-mentioned dynamic bending test is conducted on the glass laminate, it is preferable that the glass laminate does not crack or break when it is repeatedly bent 200,000 times so that the distance between the opposing short sides of the glass laminate is 12 mm.

In addition, when the number of samples in the dynamic bending test is 10, the pass rate calculated by the following formula from the total number of samples (10) and the number of samples in which cracks or breaks did not occur in the glass laminate is preferably 80% or more.
Pass rate (%) = (number of samples in which cracks or breaks did not occur in the glass laminate) / 10 x 100

In the dynamic bending test, as with the U-bend test described above, it is preferable that the above-mentioned bending resistance be maintained when the glass laminate is folded so that the first main surfaces of the glass substrates face outward. It is even more preferable that the above-mentioned bending resistance be maintained both when the glass laminate is folded so that the first main surfaces of the glass substrates face outward and when the glass laminate is folded so that the first main surfaces of the glass substrates face inward.

5. Uses of Glass Laminate The glass laminate according to the present disclosure can be used as a component arranged on the viewer side of the display panel in a display device. The glass laminate according to the present disclosure can be used in display devices used in electronic devices such as smartphones, tablet devices, wearable devices, personal computers, televisions, digital signage, public information displays (PIDs), and in-vehicle displays. In particular, the glass laminate according to the present disclosure can be preferably used in flexible displays such as foldable displays, rollable displays, and bendable displays, and is more preferably used in foldable displays.

In particular, the glass laminate of the present disclosure is preferably used in a display device that can be folded so that the first main surface of the glass substrate faces outward. As described above, when the glass substrate is folded so that the first main surface faces outward, bending resistance can be improved compared to when the glass substrate is folded so that the second main surface faces outward.

When the glass laminate of the present disclosure is disposed on the surface of a display device, it may be disposed so that the first major surface of the glass substrate faces the display panel, or so that the second major surface of the glass substrate faces the display panel. Furthermore, for example, when a foldable display device is folded so that the screen faces inward, it is preferable to fold it so that the first major surface of the glass substrate faces outward, as described above. Therefore, it is preferable that the glass laminate be disposed so that the first major surface of the glass substrate faces the display panel. On the other hand, for example, when a foldable display device is folded so that the screen faces outward, it is preferable that the display device is folded so that the first major surface of the glass substrate faces outward, as described above. Therefore, it is preferable that the glass laminate be disposed so that the second major surface of the glass substrate faces the display panel.

The method for disposing the glass laminate of the present disclosure on the surface of a display device is not particularly limited, and examples include a method using an adhesive layer. The adhesive layer may be any known adhesive layer used for bonding glass laminates.

C. Display Device A display device according to the present disclosure includes a display panel and the above-described glass substrate or the above-described glass laminate disposed on the viewer side of the display panel.

Figure 12 is a schematic cross-sectional view showing an example of a display device according to the present disclosure, an example that includes the glass laminate described above. As shown in Figure 12, the display device 20 includes a display panel 21 and a glass laminate 10 that is disposed on the viewer's side of the display panel 21. In the display device 20, the glass laminate 10 is used as a component that is disposed on the surface of the display device 20, and an adhesive layer 22 is disposed between the glass laminate 10 and the display panel 21.

The glass substrate and glass laminate in this disclosure may be similar to the glass substrate and glass laminate described above.

Display panels in this disclosure include, for example, display panels used in display devices such as liquid crystal display devices, organic EL display devices, and LED display devices.

The display device of the present disclosure may have a touch panel member between the display panel and the glass substrate or glass laminate.

The display device according to the present disclosure is preferably a flexible display. In particular, the display device according to the present disclosure is preferably foldable. That is, the display device according to the present disclosure is more preferably a foldable display. Because the display device according to the present disclosure has the above-described glass substrate or glass laminate, it has excellent impact resistance and bending resistance, and is suitable as a flexible display, and even a foldable display.

In particular, it is preferable that the display device of the present disclosure be foldable so that the first main surface of the glass substrate faces outward. As described above, when the display device is folded so that the first main surface of the glass substrate faces outward, it has higher bending resistance than when the display device is folded so that the second main surface of the glass substrate faces outward.

D. Electronic Device An electronic device in the present disclosure includes the display device described above.

Electronic devices in this disclosure are not particularly limited as long as they are equipped with the above-mentioned display devices, and examples include smartphones, tablet devices, wearable devices, personal computers, televisions, digital signage, public information displays (PIDs), in-vehicle displays, etc.

Note that this disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical concept described in the claims of this disclosure and that provides similar effects is within the technical scope of this disclosure.

The following examples and comparative examples will further explain this disclosure.

[Example 1]
A chemically strengthened glass substrate having a thickness of 70 μm was scribed using a cutter ("SOLID-D" manufactured by Mitsubishi Diamond Industrial Co., Ltd.) and then broken to be cut into a size of 100 mm × 20 mm to obtain a glass substrate.

[Example 2]
A chemically strengthened glass substrate having a thickness of 50 μm was scribed using a cutter ("SOLID-D" manufactured by Mitsubishi Diamond Industrial Co., Ltd.) and then broken to be cut into a size of 100 mm × 20 mm to obtain a glass substrate.

[Example 3]
A glass substrate was obtained in the same manner as in Example 1, except that a chemically strengthened glass substrate having a thickness of 30 μm was used.

[Example 4]
A glass substrate was obtained in the same manner as in Example 1, except that the pressure applied during scribing with the cutter was increased by 1.5 times.

[Example 5]
A glass substrate obtained in the same manner as in Example 1 was subjected to a processing step (special polishing treatment using particles with a particle diameter of 1 μm) to adjust the width a and length b.

[Example 6]
A glass substrate was obtained in the same manner as in Example 1, except that the pressure applied during scribing with the cutter was increased by 2.5 times.

[Example 7]
A glass substrate was obtained in the same manner as in Example 5, except that the special polishing time was set to 0.4 times the special polishing time of Example 5.

[Example 8]
A glass substrate was obtained in the same manner as in Example 1, except that untempered glass was used.

[Example 9]
A glass substrate was obtained in the same manner as in Example 2, except that the pressure applied when scribing with a cutter was reduced by 1/6.

[Comparative Example 1]
A 70 μm thick glass substrate was scribed using a cutter ("Glass Scriber Cutter Tip" manufactured by Kosaka Laboratory Co., Ltd.) with a push-in depth of 0.1 mm and a speed of 20 mm/sec, and then broken to be cut into pieces measuring 100 mm × 20 mm. The glass substrate was then subjected to a chemical strengthening treatment.

[Comparative Example 2]
A chemically strengthened glass substrate having a thickness of 70 μm was cut into a size of 100 mm × 20 mm by scribing and breaking under the same conditions as in Comparative Example 1. Thereafter, the cut surface of the chemically strengthened glass substrate was polished with abrasive paper containing an abrasive having a grain size of 15 μm, and then polished with diamond abrasive grains having a grain size of 1 μm.

[Comparative Example 3]
A chemically strengthened glass substrate having a thickness of 70 μm was cut into a size of 100 mm × 20 mm using a picosecond laser with a pulse energy of 80 μJ and an oscillation frequency of 150 kHz. Then, a resist was applied to the surface of the chemically strengthened glass substrate, and the cut surface of the chemically strengthened glass substrate was etched with a hydrogen fluoride solution.

[Evaluation 1]
(1) Shape The cut surface of the glass substrate was observed at a magnification of 20,000 times using a scanning electron microscope (SEM) (Hitachi High-Technologies Corporation "S-4800"), and the side shape was measured. The glass substrates of Examples 1 and 2 and Comparative Example 1 had a first main surface, a second main surface opposite the first main surface, and a side surface connecting the first main surface and the second main surface, and the side surface had an inclined portion connecting to the first main surface and a flat portion connecting the inclined portion and the second main surface. In addition, in the glass substrates of Examples 1 and 2, the inclined portion of the side surface had a curved surface that was convex outward. The glass substrate of Comparative Example 2 had a first main surface, a second main surface opposite the first main surface, and a side surface connecting the first main surface and the second main surface, and the side surface was flat. The glass substrate of Comparative Example 3 had a first main surface, a second main surface opposite the first main surface, and a side surface connecting the first main surface and the second main surface, and the side surface had a first inclined portion connecting to the first main surface, a second inclined portion connecting to the second main surface, and a flat portion connecting the first inclined portion and the second inclined portion, and the end of the glass substrate had a tapered shape.

(2) Maximum height Sz
The maximum height Sz of the side surface of the glass substrate was measured using a non-contact surface/layer cross-sectional shape measurement system, VertScan 2.0 R5500GML-A150-AC, manufactured by Ryoka Systems Co., Ltd. Various parameters were determined based on ISO 25178, and measurements were taken at 10 random locations to determine the arithmetic mean value. The measurement conditions were as follows. The 10 random locations were selected from locations that excluded the upper and lower 20% of the glass substrate in the thickness direction and were free of dust, dirt, etc.
Measurement area: 0.02 mm x 0.02 mm
・Objective lens: 50x ・Measurement mode: Wave
Wavelength filter: 530 white
Height analysis mode: p-v mode

The measurement is carried out by the following method.
As shown in Fig. 14, first, a glass substrate 101 is fixed by being sandwiched between two jigs 100, 100 on a stage S. Next, a lens 102 equipped with a light source is placed directly above the side surface of the glass substrate 101. The inclination of the stage S is adjusted so that the direction of light from the light source is perpendicular to the stage S. Finally, the height of the stage S is adjusted to adjust the distance between the lens 102 and the side surface of the glass substrate 101, thereby adjusting the focus, and then measurement is performed.

(3) U-shaped bending test The glass substrate was subjected to the above-described U-shaped bending test. The distance d between the two opposing short sides of the glass substrate when cracks or breakage occurred in the glass substrate was measured. Table 1 shows the maximum distance when cracks or breakage occurred in the glass substrate. The smaller the value, the better the bending resistance.

The results of the U-bend test were evaluated according to the following criteria.
A: d = less than 5 mm B: d = 5 mm or more, less than 10 mm C: d = 10 mm or more

In Table 1, "bent outward from the first principal surface" refers to the case where the glass substrate was folded so that the first principal surface was on the outside, and "bent within the first principal surface" refers to the case where the glass substrate was folded so that the first principal surface was on the inside. Also, in Table 1, the numbers in parentheses indicate the above evaluation.

(4) Dynamic Bending Test The above-described dynamic bending test was carried out on the glass substrate to evaluate the bending resistance of the glass substrate.
In this test, the distance d between the two opposing short sides of the glass substrate was 8 mm or 12 mm, and the number of repetitions was 200,000. The number of samples was 10. The pass rate was calculated from the total number of samples (10) and the number of samples in which no cracks or breaks occurred in the glass substrate using the following formula.
Pass rate (%) = (number of samples in which the glass substrate was not cracked or broken) / 10 x 100

The results of the dynamic bending test were evaluated according to the following criteria.
A: The pass rate is over 80%.
B: The pass rate is between 60% and 80%.
C: The pass rate is less than 60%.

In Table 1, "bent outward from the first principal surface" refers to the case where the glass substrate was folded so that the first principal surface was on the outside, and "bent within the first principal surface" refers to the case where the glass substrate was folded so that the first principal surface was on the inside. Also, in Table 1, the numbers in parentheses indicate the above evaluation.

(5) Impact Resistance of Edges An impact test was performed on a glass substrate as illustrated in FIG. 13 . First, a sample stage 31 and a rail 32 were positioned at an angle of 16° relative to the horizontal. Next, a glass substrate 1 was placed on the sample stage 31, and a weight 33 was placed on the glass substrate 1 to fix the glass substrate 1. The glass substrate 1 was fixed so that the edge of the glass substrate 1 protruded 2 mm from the side of the sample stage 31. Next, a 5.5 g, φ11 mm steel ball 34 was dropped from a predetermined distance L along the rail 32 to impact the side of the glass substrate 1. The maximum distance L at the edge of the glass substrate at which the glass substrate did not crack or break was measured. Note that a larger value indicates higher impact resistance.
The results of the impact resistance of the edge were evaluated according to the following criteria.
A: 12cm or more B: 8cm or more C: Less than 8cm

Generally, when a glass substrate is chemically strengthened, cutting results in a decrease in strength at the side of the glass substrate because no compressive stress layer is present on the side of the glass substrate. In contrast, as shown in Table 1, when the side of the glass substrate has an inclined portion connected to the first main surface, the width a of the inclined portion in the direction of the first main surface of the glass substrate is within a predetermined range, and the length b of the inclined portion in the thickness direction of the glass substrate is within a predetermined range (Examples 1 and 2), it was confirmed that the impact resistance of the edge of the glass substrate is good. Furthermore, when the maximum height Sz of the side of the glass is equal to or less than a predetermined value (Examples 1 and 2), it was confirmed that the bending resistance is good.

[Evaluation 2]
(Maximum height Sz)
The side surface of the glass substrate of Examples 1 and 2 and Comparative Example 1 was divided into ten equal parts in the thickness direction, and the regions were designated as first to tenth regions in order from the first main surface side to the second main surface side, and the maximum height Sz of each region was measured. The maximum heights of the first to tenth regions were designated Sz1 to Sz10 in order from the first region to the tenth region, respectively.

The maximum height Sz of each region of the side surface of the glass substrate was measured using a non-contact surface/layer cross-sectional shape measurement system, VertScan 2.0 R5500GML-A150-AC, manufactured by Ryoka Systems Co., Ltd. Various parameters were determined based on ISO 25178, and measurements were taken at 10 arbitrary points in each region, and the arithmetic mean value of these parameters was calculated. The measurement conditions were as follows:
Measurement area: 7 μm x 10 μm when the thickness of the glass substrate is 70 μm
When the thickness of the glass substrate is 50 μm, 5 μm × 10 μm
When the thickness of the glass substrate is 30 μm, 3 μm × 10 μm
・Objective lens: 50x ・Measurement mode: Wave
Wavelength filter: 530 white
Height analysis mode: pv mode The measurement method was the same as in [Evaluation 1] above.

In Examples 1 to 3, 7, and 9, the relationships of the following formulas (1) to (3) were satisfied. On the other hand, in Comparative Example 1, the relationships of the following formulas (1) and (2) were not satisfied.
Sz1>Sz4 (1)
Sz1>Sz5 (2)
Sz1>Sz6 (3)

REFERENCE SIGNS LIST 1 ... Glass substrate 1A ... First main surface of glass substrate 1B ... Second main surface of glass substrate 1C ... Side surface of glass substrate 2a ... Inclined portion 2b ... Planar portion 3 ... Compressive stress layer 10 ... Glass laminate 11, 12 ... Resin layer 20 ... Display device 21 ... Display panel a ... Width of inclined portion in first main surface direction of glass substrate b ... Length of inclined portion in thickness direction of glass substrate T ... Thickness of glass substrate

Claims (13)

A glass substrate having a first surface, a second surface opposite to the first surface, and a side surface connecting the first surface and the second surface,
The thickness of the glass substrate is 15 μm or more and 100 μm or less,
the side surface has an inclined portion connected to the first surface and extending outward from an end of the first surface at an incline toward the second surface with respect to the first surface,
The width of the inclined portion in the first surface direction of the glass substrate is 0.05 μm or more and 9.00 μm or less,
The length of the inclined portion in the thickness direction of the glass substrate is 0.05 μm or more and 5.00 μm or less,
A glass substrate, wherein a ratio (a/b) of a width a of the inclined portion in a first surface direction of the glass substrate to a length b of the inclined portion in a thickness direction of the glass substrate is 1.8 or more and 20.0 or less . The glass substrate according to claim 1 , wherein the inclined portion has an outwardly convex curved surface. The glass substrate according to claim 1 or 2 , wherein the maximum height Sz of the side surface is 1.5 μm or less. 4. The glass substrate according to claim 3, wherein when the regions formed by dividing the side surface into ten equal parts in a thickness direction are designated as a first region to a tenth region in the order from the first surface side to the second surface side, and when the maximum heights of the first region to the tenth region of the side surface are designated as Sz1 to Sz10 in the order from the first region to the tenth region, respectively, the glass substrate satisfies the relationships of the following formulas (1) to (3):
Sz1>Sz4 (1)
Sz1>Sz5 (2)
Sz1>Sz6 (3) The glass substrate according to claim 1 , wherein the side surface has a flat portion connecting the inclined portion and the second surface. The glass substrate according to any one of claims 1 to 5 , which is chemically strengthened glass. The glass substrate according to claim 1 , which is used in a foldable display device so that the first surface of the glass substrate faces outward. The glass substrate according to any one of claims 1 to 7 ,
a resin layer disposed on at least one of a first surface side and a second surface side of the glass substrate;
A glass laminate comprising: The glass laminate according to claim 8 , wherein the resin layer is disposed on the second surface side of the glass substrate. 10. The glass laminate according to claim 8 or claim 9 , which has a total light transmittance of 85% or more and a haze of 1.5% or less. A display panel;
a glass substrate according to any one of claims 1 to 7 or a glass laminate according to any one of claims 8 to 10, which is disposed on a viewer side of the display panel;
A display device comprising: The display device according to claim 11 , which is foldable so that the first surface of the glass substrate faces outward. An electronic device comprising the display device according to claim 11 or 12 .