WO2014030738A1

WO2014030738A1 - Glass substrate for cover glass for electronic device, cover glass for electronic device, and method for manufacturing glass substrate for cover glass for electronic device

Info

Publication number: WO2014030738A1
Application number: PCT/JP2013/072547
Authority: WO
Inventors: 高野　徹朗
Original assignee: Hoya株式会社
Priority date: 2012-08-23
Filing date: 2013-08-23
Publication date: 2014-02-27
Also published as: JP2017019723A; JPWO2014030738A1; JP6313391B2; CN104379533A; CN104379533B; JP6025156B2

Abstract

The present invention provides a glass substrate for a cover glass for an electronic device, in which the strength of an end face having an apex is enhanced. This glass substrate has a pair of end faces adjoining a principal surface, and the end faces are shaped having an apex as viewed in cross-section and have a compressive stress layer due to chemical strengthening, the maximum compressive stress being 600 MPa or greater, and the depth of the compressive stress layer being 60 µm or less. The apex angle θ (degrees) of the apex, the maximum compressive stress (CS) [MPa] of the surface, and the depth (d) [µm] of the compressive stress layer satisfy the relationship 600 MPa ≤ -3.5 × {(d/sin(θ/2)) - d} + CS.

Description

Glass substrate for cover glass for electronic device, cover glass for electronic device, and method for manufacturing glass substrate for cover glass for electronic device

The present invention relates to a portable device cover that serves as a cover for a display screen of a portable device such as a mobile phone, a portable game machine, a PDA (Personal Digital Assistant), a digital still camera, a video camera, or a slate PC (Personal Computer). Glass, glass for touch sensor used as cover for touch sensor, glass substrate for cover glass for electronic device including cover glass for track pad used for operation panel of PC, cover glass for electronic device, and cover glass for electronic device This invention relates to a method for producing a glass substrate.

Conventionally, in mobile devices such as mobile phones (electronic devices), an acrylic resin plate having excellent transparency and light weight has been generally used for its display screen. However, in recent years, it has become thinner than a conventional acrylic resin plate. The cover glass is made of a glass material that has high strength and is superior to conventional acrylic resin plates in terms of surface smoothness, protection (weather resistance, antifouling properties), appearance and luxury. It has come to be.

By the way, in recent years, touch-panel electronic devices have become dominant. In the touch panel method, an electronic device is operated mainly by pressing a predetermined part (for example, an icon displayed on the screen) of the display screen. Therefore, improvement of the strength of the display screen is required. In addition, efforts have been made to reduce the thickness of electronic devices from the viewpoint of weight reduction and design. For this purpose, there is a demand for a cover glass having sufficient strength even if it is thin, lightweight, and has a large screen (large area).

In order to satisfy the requirements for such cover glass for electronic equipment, the cover glass is subjected to a chemical strengthening treatment for improving its strength. This chemical strengthening treatment is performed by immersing the glass substrate in a chemical strengthening treatment liquid obtained by heating and melting the chemical strengthening salt. For example, by increasing the heating temperature of the chemical strengthening treatment liquid or extending the treatment time, It is thought that as the thickness (depth) of the compressive stress layer formed on the surface layer of the substrate increases, the compressive stress value increases and the strength (breaking strength, scratch resistance, etc.) of the glass substrate increases. It is also known that chemically tempered glass with excellent tempering properties increases delayed fracture and brittleness if too much chemical strengthening is applied.

For example, Patent Document 1 discloses a tempered glass article having a central tension lower than a limit value at which the glass exhibits brittleness beyond that, and includes central tension CT, compressive stress, stress layer depth, glass plate thickness, and the like. The chemical strengthening conditions which do not show brittleness in relation to the above are disclosed.

Special table 2011-530470 gazette

However, according to the study of the present inventor, even in a glass substrate subjected to chemical strengthening under the chemical strengthening conditions disclosed in Patent Document 1, for example, by contact with a jig in the cover glass assembly process, the glass substrate It has been found that cracks, scratches and the like are generated on the end face, and a lot of cracks, cracks and the like are generated from the cracks.
In addition, for example, a glass substrate having an end surface shape having apexes 14 to 16 as shown in FIGS. 1A to 1C is structurally chipped or cracked starting from a chip compared to a curved or flat surface. Easy to do. Furthermore, as will be described later, it has also been found that chemical strengthening enters deeper than expected at such a top portion and there is a decrease in compressive stress. Therefore, in the glass substrate used for the cover glass for electronic devices, the strength improvement of the end face is particularly desired.

Accordingly, an object of the present invention is to provide a glass substrate for an electronic device cover glass that has improved the strength of the end face having the top, the cover glass for an electronic device provided with this glass substrate, and the glass substrate for an electronic device cover glass. It is to provide a manufacturing method.

In the said patent document 1, although the chemical strengthening of the main surface of a glass article is examined as mentioned above, nothing is examined about the chemical strengthening of the end surface of a glass article. In order to solve the above-mentioned problems, the present inventors have intensively studied the relationship between the end face shape of the glass substrate and chemical strengthening, and as a result, have completed the present invention based on the obtained knowledge.
That is, the present invention has the following configuration.

(Configuration 1)
A glass substrate used for a cover glass for electronic equipment, wherein the glass substrate contains, as main components, SiO ₂ 50 to 70 wt%, Al ₂ O ₃ 5 to 20 wt%, Na ₂ O 6 to 20 wt%, K ₂ O 0-10 wt%, MgO 0-10 wt%, CaO 0-10 wt% glass composition, wherein the glass substrate comprises a pair of main surfaces and end faces adjacent to the pair of main surfaces And the end surface has a shape having a top portion in a cross-sectional view, and the glass substrate has a compressive stress layer formed on the surface by chemical strengthening by ion exchange, and has a maximum compressive stress on the main surface. The value is 600 MPa or more, the depth of the compressive stress layer is 60 μm or less, the apex angle of the apex is θ [degrees], the maximum compressive stress value of the main surface is CS [MPa], and the compressive stress layer of the main surface If the depth of d is [μm],
600 MPa ≦ −3.5 × {(d / sin (θ / 2)) − d} + CS
It is a glass substrate of the cover glass for electronic devices characterized by satisfy | filling these relationships.

(Configuration 2)
2. The glass substrate of a cover glass for an electronic device according to Configuration 1, wherein the apex angle θ of the apex is not less than 30 degrees and not more than 135 degrees.
(Configuration 3)
The end surface of the glass substrate has a shape in which two concave surfaces that draw a substantially arc toward the inside of the substrate in a cross-sectional view intersect each other near the center in the thickness direction of the substrate, and the thickness direction at the end surface of the glass substrate The glass substrate of a cover glass for an electronic device according to

Configuration

1 or 2, wherein the top portion is disposed in each of a central portion and a thickness direction main surface side of an end surface.

(Configuration 4)
The glass of the cover glass for an electronic device according to

Configuration

1 or 2, wherein a central portion in the thickness direction on the end surface of the glass substrate is curved, and the top portion is disposed on the main surface side in the thickness direction on the end surface. It is a substrate.
(Configuration 5)
The said glass substrate is a glass substrate of the cover glass for electronic devices in any one of the structures 1 thru | or 4 which consists of aluminosilicate glass.

(Configuration 6)
6. The glass substrate for a cover glass for an electronic device according to any one of Structures 1 to 5, wherein a thickness of the glass substrate is in a range of 0.1 mm to 1.5 mm.
(Configuration 7)
An electronic apparatus cover glass comprising the glass substrate according to any one of Configurations 1 to 6.

(Configuration 8)
A method for producing a glass substrate used for a cover glass for electronic equipment, wherein the glass substrate contains 50 to 70% by weight of SiO ₂ , 5 to 20% by weight of Al ₂ O _{3 and} 6 to 20% of Na ₂ O as main components. A glass composition containing 1% by weight, 0 to 10% by weight of K ₂ O, 0 to 10% by weight of MgO, and 0 to 10% by weight of CaO. An external shape processing step for processing an external shape, and a chemical strengthening step for performing chemical strengthening treatment by ion exchange on the glass substrate subjected to the external shape processing. In the external shape processing step, a pair of main surfaces and the pair of main surfaces The end surface is adjacent to the surface, and the end surface forms a glass substrate having a shape having a top portion in cross-sectional view. In the chemical strengthening step, the apex angle of the top portion is set to θ [degree], and chemical strengthening is performed. That That CS [MPa] maximum compressive stress value of the main surface, when the depth of the compression stress layer of the main surface formed by the chemical strengthening is performed and d [[mu] m],
600 MPa ≦ −3.5 × {(d / sin (θ / 2)) − d} + CS
The method of manufacturing a glass substrate of a cover glass for an electronic device, wherein a chemical strengthening treatment is performed so as to satisfy the above relationship.

(Configuration 9)
9. The electronic device according to Configuration 8, wherein the outer shape processing step includes a step of cutting out a predetermined outer shape from a sheet glass by machining and a step of processing an end surface shape of the cut glass substrate by wet etching. It is a manufacturing method of the glass substrate of a cover glass.

According to the present invention, in particular, the strength of the end face having the top is improved due to the brittleness of the end face having the top, such as the strength of the end face having the top and the reduction of the compressive stress due to the chemical strengthening of the conventional structure or deeper than expected. The glass substrate of the cover glass for electronic devices which can reduce generation | occurrence | production of a chip, a crack, etc., the cover glass for electronic devices provided with this glass substrate, and the manufacturing method of the glass substrate of the cover glass for electronic devices can be provided.

(A), (b), (c) is sectional drawing which shows the end surface shape example of the glass substrate in connection with this invention. (A)-(c) is a reference drawing for demonstrating the definition of the apex angle heel of the end face top part in this invention, respectively. It is a figure which shows the relationship between an apex angle and the compressive-stress layer depth in a top part. It is a figure which shows the relationship between chemical strengthening conditions, a compressive-stress layer depth, and a maximum compressive-stress value. It is a figure which shows the relationship between the compressive-stress layer depth d, apex angle (theta), and the maximum compressive-stress value CS on the surface when the maximum compressive-stress value in a top part is 600 Mpa or more. (A) And (b) is a reference drawing for demonstrating the edge drop test method of a glass substrate.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The cover glass for electronic equipment according to the present invention is incorporated as a cover glass for mobile equipment, for example, on a display screen of a mobile phone. The cover glass for an electronic device in the present invention is a cover for a display screen of a mobile device such as a mobile phone, a portable game machine, a PDA (Personal Digital Assistant), a digital still camera, a video camera, or a slate PC (Personal Computer). Mobile device cover glass, touch sensor cover glass serving as a touch sensor cover, trackpad cover glass used for an operation panel of a PC, and the like.

For example, the cover glass for mobile devices is required to be strong because it is necessary to protect the display screen from being damaged by an external impact. In particular, in the case of a touch panel, a cellular phone is operated by pressing a predetermined part (for example, an icon displayed on the screen) of the display screen. Is required to have a cover glass having sufficient strength even if it is thin, lightweight, and has a large screen (large area).

The cover glass for an electronic device according to the present invention is manufactured by a process as described below. Here, as an example, a case of a cover glass for a mobile device such as a mobile phone will be described.
First, a glass material (large plate glass) formed into a sheet shape is cut into a predetermined size by etching (small piece) to produce a glass substrate for cover glass.

A sheet-like glass material (sheet glass) having a thickness of, for example, about 0.5 mm manufactured by a downdraw method or a float method is cut into small pieces of a predetermined size by etching. The size of the small piece may be determined in consideration of the size of the product cover glass plus the margin necessary for the outer peripheral shape processing.

The thickness of the glass substrate for cover glass is preferably in the range of, for example, about 0.1 mm to 1.5 mm, more preferably from the viewpoint of responding to the recent market needs for thinner and lighter portable devices. The range is about 0.3 mm to 0.7 mm.

In the present invention, the glass constituting the glass substrate for cover glass is preferably a glass composition that can be chemically strengthened by ion exchange, for example, amorphous aluminosilicate glass. A glass substrate made of such an aluminosilicate glass is excellent in strength after chemical strengthening. As such an aluminosilicate glass, for example, SiO ₂ is 50 to 70 wt%, Al ₂ O ₃ is 5 to 20 wt%, Na ₂ O is 6 to 20 wt%, and K ₂ O is 0 to 10 wt%. An aluminosilicate glass containing 0 to 10% by weight of MgO and 0 to 10% by weight of CaO as main components can be used.

When the above plate glass is cut into small pieces, if an etching method is applied, it is possible to cut out a desired shape, particularly a complicated outer shape, and the outer shape processing and perforation processing can be performed simultaneously with the formation of the outer periphery of the glass substrate. It can be carried out. That is, a resist (photosensitive organic material) is applied to the surface of the plate glass, and predetermined exposure and development are performed to form a resist pattern having a cutting line pattern (a pattern in which no resist exists on the cutting line). Form. Then, the glass material on which such a resist pattern is formed is cut into small pieces of a predetermined size by wet etching using an etching solution that can dissolve the glass material (for example, an acidic solution containing hydrofluoric acid as a main component). The remaining resist pattern is peeled off and washed.

FIGS. 1A and 1B are cross-sectional views showing examples of the shape of the end face of a glass substrate obtained by etching a plate glass and cutting the outer shape into, for example, a rectangular shape.
A glass substrate 1 shown in FIG. 1 has a pair of opposing

main surfaces

11 and 12 and an end face 13 adjacent to the pair of

main surfaces

11 and 12. When the glass substrate is etched using a resist pattern (not shown) formed on the

main surfaces

11 and 12 of the glass substrate (plate glass before cutting) as a mask, the etching is performed from both the

main surfaces

11 and 12 facing the glass substrate, respectively. Therefore, the top portion 16 is formed on the end surface 13 by etching that proceeds from the main surface 11 side and etching that proceeds from the main surface 12 side. In this etching, since the etching proceeds so as to draw a substantially circular arc from the main surface 11 side and the main surface 12 side toward the inside of the glass substrate in a cross-sectional view, when the glass substrate 1 is cut out, Two concave surfaces that draw a substantially circular arc toward the center of the substrate have an end surface shape that intersects near the center in the thickness direction of the substrate (see FIG. 1A). As a result, the top portion 16 is formed at the center in the thickness direction of the substrate, and the

top portions

14 and 15 are formed at the edge portions between the end surface 13 and the

main surfaces

11 and 12. That is, the end surfaces of the obtained glass substrate 1 have the

top portions

14, 15, and 16 disposed at the center portion in the thickness direction at the end surface and the main surface side in the thickness direction at the end surface.

FIG. 1B shows an example in which the top shape is improved by grinding or chamfering the

top portions

14 and 15 on the

main surfaces

11 and 12 side after the etching. The above describes the case where the plate glass is shredded by an etching method. However, the present invention is not limited to this. For example, a large-sized plate glass is cut (cut into small pieces) to a predetermined size by machine (cutter) processing. The glass substrate 1 for cover glass can also be produced by polishing the surface with a grindstone or the like. For example, a large number (for example, about several tens) of sheet glass having a thickness of, for example, about 0.5 mm manufactured by the downdraw method or the float method is laminated (laminated), and, for example, a predetermined size is obtained using a glass cutter. Cut into small pieces. As described above, if the laminated state is cut at a time, the laminated pieces can be shaped at the same time in the next shape processing step, which is advantageous in production. Then, after performing necessary shape processing by machining, processing by wet etching is mainly performed to remove a damaged layer such as micro cracks on the processed surface.

Also in the glass substrate thus obtained, as shown in FIG. 1 (c), apexes 14 and 15 are formed at the edge portions of the end surface 13 and both the

main surfaces

11 and 12. That is, the end surface of the glass substrate 1 obtained by external processing using both machining and wet etching is curved at the center in the thickness direction at the end surface, and the top portion 14 on the main surface side in the thickness direction at the end surface. , 15 are arranged.

Here, the apex angle θ of the apex formed on the end surface 13 of the glass substrate 1 cut out from the plate glass by etching or machining is defined as follows in the present invention.
This will be described with reference to FIG. The top 16 formed at the center in the thickness direction of the glass substrate 1 is drawn at the apex (the most protruding point) and a circle with a radius of 10 μm from the apex (drawn with a broken line in FIG. 2). The angle formed by two imaginary lines L1 and L2 that respectively connect the contact point between the contour of the glass substrate 1 and the contour line of the glass substrate 1 is defined as an apex angle θ (see FIG. 2A).

Further, with respect to the top portion 15 formed on the main surface side in the thickness direction at the end face, when a circle having a radius of 10 μm is drawn from the vertex (the most protruding point), the circle (indicated by a broken line in FIG. 2). An angle formed by two virtual lines L1 and L2 respectively connecting the drawn circle) and the contact point of the outline of the glass substrate 1 is defined as an apex angle θ (see FIG. 2B). In this case, one virtual line (for example, virtual line L2) is located on main surface 12. The apex angle of the apex 14 is defined similarly.

Further, the curved surface or the chamfered top portion 15 as shown in FIG. 1 (b), and the glass substrate 1 obtained by performing the outer shape processing by combining the mechanical processing and wet etching as shown in FIG. 1 (c). As for the apex 15 on the end surface in the thickness direction main surface side, when the vertex (the most protruding point) and a circle with a radius of 10 μm are drawn from the vertex (the circle drawn with a broken line in FIG. 2). An apex angle θ is an angle formed by two virtual lines L1 and L2 that connect the contact points of the glass substrate 1 and the contour line of the glass substrate 1 (see FIG. 2C). The apex angle of the apex 14 is defined similarly.

Next, a chemical strengthening treatment is performed on the glass substrate that has been cut into pieces by etching or machining to improve the strength.
As a method of chemical strengthening treatment, for example, a low temperature ion exchange method in which ion exchange is performed in a temperature range not exceeding the temperature of the glass transition point, for example, a temperature of 300 to 600 degrees Celsius is preferable. The chemical strengthening treatment is a process in which a molten chemical strengthening salt is brought into contact with a glass substrate, whereby an alkali metal element having a relatively large atomic radius in the chemical strengthening salt and a relatively small atomic radius in the glass substrate. This is a treatment in which an alkali metal element is ion-exchanged, an alkali metal element having a large ion radius is permeated into the surface layer of the glass substrate, and compressive stress is generated on the surface of the glass substrate.

As the chemical strengthening salt, alkali metal nitrates such as potassium nitrate and sodium nitrate can be preferably used. A chemically strengthened glass substrate is improved in strength and excellent in impact resistance, and thus is suitable for a cover glass used for a portable device that requires impact and pressure and requires high strength.

The chemical strengthening process will be described in more detail. For example, a rectangular glass substrate is immersed in a chemical strengthening treatment liquid obtained by heating and melting a chemically strengthened salt, thereby chemically strengthening the glass substrate; and And a cooling step of taking out the glass substrate from the chemical strengthening treatment liquid and lowering the temperature of the glass substrate.

In order to solve the above-mentioned problems, the inventor has intensively studied the relationship between the end face shape of the glass substrate, in particular, the end face shape having a top as shown in FIG. 1 and chemical strengthening.
The compressive stress layer generated at the top of the end surface by chemical strengthening proceeds with ion exchange from the two directions on both sides of the top, so the compressive stress layer generated on the region surface other than the top on the end surface and the main surface It is presumed that the depth (thickness) becomes deep, and it is considered that the compressive stress value at the top portion is smaller than the compressive stress value at the main surface. When the depth (thickness) of the compressive stress layer measured in the normal direction of the area surface other than the top of the end surface or the main surface is d, the top surface of the end surface is measured in the direction of the bisector of the apex angle θ. The depth d ′ of the compressive stress layer at the top can be theoretically calculated when d / sin (θ / 2).

Here, using the relational expression of d / sin (θ / 2), the apex angle of the apex and the compressive stress layer depth at the apex (the compressive stress layer depth at the main surface or the like is 100) FIG. 3 shows the result of the relationship with the% ratio. As shown in FIG. 3, it has been found that the depth of the compressive stress layer at the top of the end face becomes deeper as the apex angle is less than 90 degrees, that is, an acute angle.

Moreover, FIG. 4 is a figure which shows the relationship between chemical strengthening conditions, the compressive-stress layer depth of a main surface, and the maximum compressive-stress value.
The fracture strength and scratch resistance of the chemically strengthened glass substrate correlate with the maximum compressive stress value of the substrate surface, and it is considered that the larger the compressive stress value, the stronger the impact from the outside. FIG. 4 shows the compressive stress layer depth and maximum when chemical heating conditions are changed within the range of 440 ° C. to 500 ° C. and the processing time (immersion time) within the range of 2 to 9 hours. The relationship with the compressive stress value is shown.
According to FIG. 4, it is shown that the maximum compressive stress value of the compressive stress layer measured in the direction perpendicular to the end face (region surface other than the top) or the main surface decreases as the depth increases. That is, if the chemical strengthening is made too deep with respect to the glass substrate, the maximum compressive stress value is lowered.

Investigating this on the top of the end face, the top (especially when the apex angle is an acute angle) is likely to concentrate stress when it hits, and it is desirable to have higher strength. However, at the top, ion exchange more than expected proceeds as described above, and a compressive stress layer deeper than the compressive stress layer generated on the main surface or the like is formed by the chemical strengthening conditions, and as a result, more than expected. Only low compressive stress can be obtained. For this reason, it is considered that the top portion is more likely to generate cracks and scratches due to external impacts, and the cracks and cracks starting from the cracks are more likely to occur.

Based on the above findings, the present inventor has examined the conditions for obtaining a sufficient strength against an impact at the top of the end face.
Some overlap with what has already been described, but the depth of the compressive stress layer measured in the direction perpendicular to the end face (area surface other than the top) or the main surface is d [μm] (actual value), and the top at the top The theoretical value of the depth of the compressive stress layer measured in the direction of the bisector of the angle is d ′ [μm], the apex angle of the apex is θ [degrees], the end surface (region surface other than the apex) and the main surface The maximum compressive stress value is CS [MPa] (actual value), and the theoretical value of the maximum compressive stress value at the top is CS ′ [MPa].

As described above, d ′ = d / sin (θ / 2).
Also, CS ′ = A × (d′−d) + CS = A × {(d / sin (θ / 2)) − d} + CS
... The relational expression with the expression (1) is established.
Here, A is the ratio of the change amount of the compressive stress value to the change amount of the depth of the compressive stress layer, and a value within the range of −10 MPa / μm to −0.5 MPa / μm can be selected. When A is larger than −0.5 MPa / μm, the amount of change (decrease) in the compressive stress value relative to the amount of change in the depth of the compressive stress layer is small. There is little need to consider how to enter. On the other hand, when A is smaller than −10 MPa / μm, the glass substrate has a large amount of change (decrease) in the compressive stress value relative to the amount of change in the depth of the compressive stress layer. Not suitable as a cover glass.

Here, in order to suppress the occurrence of chipping or cracking due to brittleness of the end face having the top, it is preferable that the theoretical value CS ′ of the compressive stress value of the top is preferably 600 MPa or more. Confirmed by the person. When CS ′ ≧ 600 MPa, the compressive stress layer depth d, apex angle θ, and the maximum compressive stress value CS on the surface are obtained by the following relational expression, and the results are shown in FIG.
600 MPa ≦ A × {(d / sin (θ / 2)) − d} + CS
Here, the value of A, that is, the ratio of the amount of change in the compressive stress value to the amount of change in the depth of the compressive stress layer, is that the glass composition is SiO ₂ : 60.2 wt%, Al ₂ O ₃ : 13.2 wt%. Na ₂ O: 13.9 wt%, K ₂ O: 3.3 wt%, MgO: 2.2 wt%, CaO: 3.2 wt%, ZrO: 4.0 wt% It can be calculated from the experimental results under practical strengthening conditions as shown in FIG.
As an example of this strengthening condition, using a molten salt of potassium nitrate 100%, at the heating temperature of the chemical strengthening treatment liquid of Tg (glass transition temperature of the glass) -150 ° C. which is a general chemical strengthening temperature range, The ratio of the change amount of the compressive stress value to the change amount of the depth of the compressive stress layer can be obtained from the measured value under the strengthening condition where d is 20 μm and 40 μm, for example, and the ratio can be used as A.
Here, A is set to −3.5 MPa / μm from the result of FIG.

Here, a chemically strengthenable aluminosilicate glass applied to the present invention, SiO ₂ is 50 to 70 wt%, Al ₂ O ₃ is 5 to 20 wt%, Na ₂ O is 6 to 20 wt%, For an aluminosilicate glass having a glass composition containing 0 to 10% by weight of K ₂ O, 0 to 10% by weight of MgO, and 0 to 10% by weight of CaO, the amount of change in the depth of the compressive stress layer It was confirmed that the amount of change in the compressive stress value was substantially equivalent to the experimental result shown in FIG. Therefore, within this composition range, the theoretical value CS ′ of the compressive stress value at the top can be obtained by using −3.5 MPa / μm as the value of A.
In the present invention, it is assumed that the apex angle θ is usually 30 degrees or more and 135 degrees or less. When the apex angle is 135 degrees or less, the reduction in compressive stress due to the chemical strengthening at a depth greater than expected is significant, and the present invention is preferably applied, and more preferably in the range of 30 degrees to 120 degrees. is there. When the apex angle is less than 30 degrees, the structure is easily chipped regardless of the presence or absence of chemical strengthening, and therefore chamfering or the like is necessary in advance. In addition, when the apex angle exceeds 135 degrees, as shown in FIG. 5, the difference between CS and CS ′ is extremely small, so that the compressive stress is reduced due to the chemical strengthening beyond the expected depth. Hateful.
Here, assuming 30 to 135 degrees, for example, in order to satisfy CS ′ ≧ 600 MPa, for example, θ is 30 degrees and d exceeds 60 μm, and since CS ≧ 1400 MPa is difficult to realize, d is 60 μm or less, CS Is suitably 600 MPa or more.

From the above, the glass substrate used for the cover glass for electronic equipment according to the present invention has a pair of main surfaces and end faces adjacent to the pair of main surfaces, and the end faces have a top portion in a cross-sectional view. The glass substrate has a compressive stress layer formed on the surface by chemical strengthening by ion exchange, the maximum compressive stress value of the main surface is 600 MPa or more, and the depth of the compressive stress layer is 60 μm. When the apex angle of the apex is θ [degrees], the maximum compressive stress value of the main surface is CS [MPa], and the depth of the compressive stress layer of the main surface is d [μm],
600 MPa ≦ A × {(d / sin (θ / 2)) − d} + CS
Here, A is the ratio of the change amount of the compressive stress value to the change amount of the depth of the compressive stress layer, and is a value in the range of −10 MPa / μm to −0.5 MPa / μm. It is characterized by satisfying. In order to obtain such a glass substrate, for example, the above-described chemical strengthening conditions are preferably adjusted as appropriate.
Here, SiO ₂ is 50 to 70 wt%, Al ₂ O ₃ is 5 to 20 wt%, Na ₂ O is 6 to 20 wt%, K ₂ O is 0 to 10 wt%, and MgO is 0 to 10 wt%. In the case of a glass composition containing 0 to 10% by weight of CaO, when −3.5 MPa / μm is used as A, the relational expression relating to compressive stress is as follows.
600 MPa ≦ −3.5 × {(d / sin (θ / 2)) − d} + CS

According to the glass substrate of the cover glass for electronic equipment of the present invention, particularly the strength of the end surface having the top portion is improved, for example, the maximum compressive stress value at the top portion is 600 MPa or more, and the depth of the conventional structure or more than expected. Occurrence of chipping, cracking, etc. due to brittleness of the end face having the apex, such as a reduction in compressive stress due to the chemical strengthening, can be reduced.
In addition, as shown in FIG. 1 described above, when the shape has the

apexes

14, 15, 16 on the end surface 13 of the glass substrate 1, it is particularly desirable to further improve the strength of the apex where the apex angle is an acute angle. From this point of view, it is preferable to appropriately adjust the aforementioned chemical strengthening conditions.

A cover glass for an electronic device is produced using the glass substrate that has been subjected to the chemical strengthening treatment described above.
The glass substrate itself may be used as a cover glass for electronic equipment. Or according to the use of an electronic device, you may provide one or more decoration layers with respect to one main surface of the said glass substrate. The decorative layer includes an anti-reflection coating, an anti-glare coating, a half mirror coating, a layer having an optical function such as a polarizing film, and a layer having an electrical function such as a transparent conductive film typified by an ITO (Indium Tin Oxide) film. And a layer having a function of improving aesthetics such as a printing layer. Moreover, various devices, such as a touch panel, can also be formed in a cover glass by laminating | stacking and patterning a some decoration layer. Examples of means for forming these decorative layers include film forming methods such as vapor deposition and sputtering, and printing methods such as screen printing.

In addition, you may give a desired antifouling coating on the surface of the glass substrate which performed the above chemical strengthening process. When a user uses a touch panel type portable device, the display screen is directly touched and operated, so that dirt such as fingerprints tends to adhere to the cover glass that protects the display screen. Therefore, it is desirable to prevent or suppress the dirt such as fingerprints from adhering to the cover glass, or to easily wipe off even if dirt such as fingerprints adheres. Therefore, it is preferable that the surface of the cover glass is subjected to an antifouling coating process using, for example, a fluorine resin material.

As mentioned above, the final cover glass for electronic devices is produced by forming arbitrarily the above-mentioned decorating layer and antifouling coating layer with respect to the chemically strengthened glass substrate.
As described above, according to the glass substrate according to the present invention, the cover glass for an electronic device including the glass substrate, and the method for manufacturing the glass substrate, the strength of the end face having the top portion can be particularly improved. It is possible to reduce the occurrence of chipping or cracking of the glass substrate or the cover glass for electronic equipment of the product due to a reduction in compressive stress caused by chemical strengthening at a depth higher than expected.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples in the case where a cover glass for electronic devices is used as a cover glass for portable devices.
(Examples and comparative examples)
The glass substrate used for the cover glass for portable devices was produced through the following (1) glass substrate processing steps and (2) chemical strengthening steps.

(1) Glass substrate processing step First, a predetermined shape (rectangular shape) and size (100 mm × 50 mm) are etched from a 0.5 mm thick plate glass made of an aluminosilicate gate glass manufactured by a downdraw method or a float method. ) And after the etching, a glass substrate for cover glass having an improved apex shape was prepared by grinding or chamfering the apex on the main surface side by grinding. As the aluminosilicate _glass, SiO 2: 60.2 wt%, Al ₂ O _3: 13.2 wt%, Na ₂ O: 13.9 wt%, K ₂ O: 3.3 wt%, MgO: 2 A glass for chemical strengthening containing 0.2 wt%, CaO: 3.2 wt%, and ZrO: 4.0 wt% was used.
After the produced glass substrate was scribed with a glass cutter, the cut surface was observed with a microscope. As a result, it was a shape having a top portion similar to that shown in FIG.

(2) Chemical strengthening process Next, the glass substrate was chemically strengthened. For chemical strengthening, a chemical strengthening treatment liquid in which potassium nitrate and sodium nitrate were mixed (see Table 1 for the mixing ratio) was prepared. The chemical strengthening treatment solution was heated to a predetermined temperature, and the glass substrate was immersed for a predetermined time to perform chemical strengthening.
Here, the heating temperature of the chemical strengthening treatment liquid was changed within the range of 440 ° C. to 500 ° C. and the treatment time (immersion time) within the range of 2 to 9 hours (see Table 1). 4 and Comparative Examples 1 to 3.

Moreover, in the said glass substrate processing process, the external shape of the glass substrate was formed by machining, the end surface of the glass substrate was etched, chemical strengthening was carried out, and it was set as Example 5 and Comparative Example 4 shown in Table 1. After scribing the produced glass substrate with a glass cutter, the cut surface was observed with a microscope. As a result, it was a shape having the same top as in FIG.
After performing chemical strengthening in this manner, the glass substrate is taken out from the chemical strengthening treatment solution, and after cooling, the glass substrate is removed from each of neutral detergent, pure water, IPA, and IPA (steam drying) in order to remove deposits on the glass substrate. It was immersed in a washing tank sequentially, ultrasonically washed, and dried.

Thus, glass substrates for cover glasses of Examples 1 to 5 and Comparative Examples 1 to 4 were produced.
The apex angle θ of the top surface of each glass substrate is formed on the top 16 formed near the center in the thickness direction of the end surface or on the main surface side in the thickness direction in accordance with the definition described with reference to FIG. The apex angle of the apex 15 (or 14) was determined.
Moreover, the compressive stress value CS and the compressive stress layer depth (thickness) d of the main surface of each glass substrate were measured using a surface stress measuring apparatus by a web guide method.

Using the apex angle θ of the end surface top portion of each glass substrate thus obtained, the compressive stress value CS of the main surface of each glass substrate, and the value of the compressive stress layer depth (thickness) d, the above-mentioned formula (1) (CS The theoretical value CS ′ [MPa] of the maximum compressive stress value at the top of each glass substrate was determined by “= A × {(d / sin (θ / 2)) − d} + CS) and shown in Table 1. From the results shown in FIG. 4, A = −3.5 MPa / μm.

Also, an edge drop test was performed on each glass substrate. As shown in FIG. 6 (a), this test is performed from above (15 cm) toward a glass substrate from a hardened steel pin 2 (φ1 mm, width (length) 20 mm) placed horizontally on a table (not shown). 1 was dropped vertically, and the presence or absence of cracks in the glass substrate or chipping at the center of the end face was evaluated.

As for the glass substrates of Examples 4 and 5 and Comparative Examples 2 to 4, as shown in FIG. 6 (b), the pin 2 is inclined 45 degrees from the horizontal, and the upper side (15 cm) is directed toward the pin. The glass substrate 1 was dropped vertically, and the presence or absence of cracks in the glass substrate or chipping at the top of the main surface rather than the center of the end face was evaluated.
The edge hitting location of the glass substrate in the edge drop test is shown in Table 1 as “1 (b) -16” in the case of the top 16 in FIG. 1 (b), and the top 15 (or 14) in FIG. 1 (b). In this case, the case of “1 (b) -15” and the case of the top 15 (or 14) of FIG.
In Table 1, those without cracks and chips were marked with “◯”.
The above results are summarized in Table 1 below.

From the results of Table 1, the theoretical value of the compressive stress value at the end of the end face increases (600 MPa or more) when the glass substrate of the embodiment of the present invention is chemically strengthened so as to satisfy the above-described relational expression. As a result, it was confirmed that the strength of the end face (particularly the top) of the glass substrate was improved in the edge drop test by applying chemical strengthening so as to satisfy the above-described relational expression.
On the other hand, the glass substrate of the comparative example was chipped in the edge drop test. In the glass substrate of this comparative example, the above-described relational expression by chemical strengthening is not satisfied, the compressive stress value at the end face top is less than 600 MPa, and the strength improvement of the end face by chemical strengthening is not achieved.
In addition, this invention is not limited to the above Example. For example, the cover glass for an electronic device may be a cover glass for a touch sensor or a cover glass for a track pad.

DESCRIPTION OF SYMBOLS 1

Glass substrate

11, 12 Main surface of glass substrate 13

End surface

14, 15, 16 top of glass substrate

Claims

A glass substrate used for a cover glass for electronic equipment,
The glass substrate as a main component,
50 to 70% by weight of SiO 2
Al 2 O 3 5-20% by weight,
Na 2 O 6-20% by weight,
K 2 O 0-10% by weight,
MgO 0-10% by weight,
A glass composition containing 0-10% by weight of CaO,
The glass substrate has a pair of main surfaces and an end surface adjacent to the pair of main surfaces, and the end surface has a shape having a top in a sectional view,
The glass substrate has a compressive stress layer formed on the surface by chemical strengthening by ion exchange, the maximum compressive stress value of the main surface is 600 MPa or more, and the depth of the compressive stress layer is 60 μm or less,
When the apex angle of the apex is θ [degree], the maximum compressive stress value of the main surface is CS [MPa], and the depth of the compressive stress layer of the main surface is d [μm],
600 MPa ≦ −3.5 × {(d / sin (θ / 2)) − d} + CS
The glass substrate of the cover glass for electronic devices characterized by satisfy | filling the relationship of these.
The glass substrate of the cover glass for an electronic device according to claim 1, wherein the apex angle θ of the apex is not less than 30 degrees and not more than 135 degrees.
The end surface of the glass substrate has a shape in which two concave surfaces that draw a substantially arc toward the inside of the substrate in a cross-sectional view intersect each other near the center in the thickness direction of the substrate, and the thickness direction at the end surface of the glass substrate The glass substrate of a cover glass for an electronic device according to claim 1 or 2, wherein the top portion is disposed in each of the center portion and the thickness direction main surface side of the end surface.
3. The cover glass for an electronic device according to claim 1, wherein the central portion in the thickness direction on the end surface of the glass substrate is curved, and the top portion is disposed on the main surface side in the thickness direction on the end surface. Glass substrate.
The glass substrate for an electronic device cover glass according to any one of claims 1 to 4, wherein the glass substrate is made of aluminosilicate glass.
6. The glass substrate of a cover glass for an electronic device according to claim 1, wherein the thickness of the glass substrate is in a range of 0.1 mm to 1.5 mm.
An electronic device cover glass comprising the glass substrate according to any one of claims 1 to 6.
A method for producing a glass substrate used for a cover glass for electronic equipment,
The glass substrate as a main component,
50 to 70% by weight of SiO 2
Al 2 O 3 5-20% by weight,
Na 2 O 6-20% by weight,
K 2 O 0-10% by weight,
MgO 0-10% by weight,
A glass composition containing 0-10% by weight of CaO,
The manufacturing method includes an outer shape processing step of cutting out a predetermined outer shape from a plate glass and processing the outer shape of the glass substrate, and a chemical strengthening step of performing chemical strengthening treatment by ion exchange on the outer shape processed glass substrate. ,
In the outer shape processing step, a pair of main surfaces and an end surface adjacent to the pair of main surfaces are formed, and the end surfaces form a glass substrate having a shape having a top portion in a sectional view,
In the chemical strengthening step, the apex angle of the top is θ [degree], the maximum compressive stress value of the main surface due to chemical strengthening is CS [MPa], and the chemical strengthening is performed. When the depth of the compressive stress layer on the main surface is d [μm],
600 MPa ≦ −3.5 × {(d / sin (θ / 2)) − d} + CS
The manufacturing method of the glass substrate of the cover glass for electronic devices characterized by performing a chemical strengthening process so that the relationship may be satisfy | filled.
9. The electronic apparatus according to claim 8, wherein the outer shape processing step includes a step of cutting a predetermined outer shape from a sheet glass by machining, and a step of processing an end surface shape of the cut glass substrate by wet etching. Of manufacturing a glass substrate of a cover glass for use.