JP2019069861A - Chemically strengthened glass, sensor unit, portable device and method for producing chemically strengthened glass - Google Patents

Abstract

To provide a chemically strengthened glass with minimized warpage.SOLUTION: A chemically strengthened glass has a thickness of less than 1000 μm, satisfying the following formula (1) and formula (2): ΔS/t≤4×10(MPa/μm) (1) and 0.05≤DOL/DOL≤0.4 (2), where, ΔS=S×0.015 (3), S=(CS+HM_CS)×DOL×0.5 (4), CS: a compression stress of an outermost surface layer on one principal face (MPa), HM_CS: a compression stress half CS(MPa), DOL: a depth of a compressive stress layer on the one principal face side (μm), DOL: a depth of the compressive stress layer corresponding to HM_CS(μm), t: the thickness of the chemically strengthened glass (μm).SELECTED DRAWING: None

Description

  The present invention relates to a chemically strengthened glass, a sensor unit, a portable device, and a method of manufacturing the chemically strengthened glass.

  2. Description of the Related Art In recent years, in panel display devices such as mobile phones and personal digital assistants (PDAs), a cover glass is disposed on the front of the display to enhance the protection of the display and the appearance. For such a panel display device, reduction in weight and thickness is required, and reduction in thickness of the cover glass is also required.

However, if the cover glass is made thinner, the strength may be reduced, and the cover glass itself may be broken due to an impact caused by dropping during use or carrying, and there is a problem that the original role of protecting the display can not be performed. The
For this reason, in the conventional cover glass, the glass plate is chemically strengthened, a compressive stress layer is formed on the surface, and the impact resistance is enhanced (Patent Document 1).

International Publication No. 2012/043482

  However, in the method of chemical strengthening described in Patent Document 1, it is a problem that as the impact resistance becomes higher, the thinner the glass is, the more the glass is warped.

  An object of the present invention is to provide a method for manufacturing a chemically strengthened glass, a sensor unit, a portable device, and a chemically strengthened glass in which warpage is minimized.

The chemically strengthened glass of the present invention is a chemically strengthened glass having two main surfaces, and the thickness of the chemically strengthened glass is less than 1000 μm, and the following characteristics (1) and (2) are satisfied: I assume.
ΔS / t ² ≦ 4 × 10 ⁻³ (MPa / μm) (1)
0.05 ≦ DOL _HM / DOL ₁ ≦ 0.4 (2)
here,
ΔS = S × 0.015 (3)
S = (CS ₀ + HM_CS ₀ ) × DOL _HM × 0.5 (4)
CS ₀ : Compressive stress of outermost layer on one main surface (MPa)
HM_CS ₀ : Compression stress half of CS ₀ (MPa)
DOL ₁ : depth of the compressive stress layer on the one principal surface side (μm)
DOL _HM : Depth of compressive stress layer corresponding to HM_CS ₀ (μm)
t: Thickness of chemically strengthened glass (μm)
According to the present invention, it is possible to provide a chemically strengthened glass in which warpage is suppressed as much as possible.

In the chemically strengthened glass of the present invention, the DOL ₁ is preferably 15 μm or more.
According to this aspect of the invention, the impact resistance of the glass surface can be enhanced.

In the chemically strengthened glass of the present invention, the relative dielectric constant is preferably 7.5 or more.
According to this aspect of the present invention, it is possible to provide a chemically strengthened glass in which warpage is suppressed as much as possible and sufficient sensing sensitivity can be obtained even when provided on a sensor.

In the chemically strengthened glass of the present invention, it is preferable to satisfy the following formula (5).
(Ε ₂ −ε ₀ ) / ε ₂ ≦ 0.05 (5)
ε ₂ : relative permittivity of the unreinforced region of the chemically strengthened glass ε ₀ : relative permittivity of the entire chemically strengthened glass According to this aspect of the present invention, the chemically strengthened glass in which the decrease in the relative permittivity due to chemical strengthening is suppressed Can be provided.

In the chemically strengthened glass of the present invention, the thickness is preferably less than 400 μm.
According to this aspect of the present invention, it is possible to reduce the weight of the unit or device in which the chemically strengthened glass is used.

The chemically strengthened glass of the present invention is a chemically strengthened glass having two main surfaces, and has a thickness of 300 μm or less, and the position and thickness direction of the two main surfaces in the thickness direction cross section When the relationship with the displacement is approximated by a quadratic function, an absolute value a of a quadratic term coefficient of the quadratic function is 1.0 × 10 ⁻⁷ μm ⁻¹ or less.

  The sensor unit of the present invention comprises a sensor and the above-described chemically strengthened glass.

  The portable device of the present invention includes the above-described sensor unit.

The method for producing a chemically strengthened glass of the present invention includes the following steps (I) to (III) sequentially, and the depth DOL ₁ of the compressive stress layer on _one major surface side of the obtained chemically strengthened glass is 15 μm or more , compressive stress CS ₀ the one main surface outermost layer is not less than 500 MPa, and a thickness is equal to or less than 1000 .mu.m.
(I) A first chemical strengthening step of forming a compressive stress layer on the glass surface by ion exchange treatment of glass (II) A heating step of heat treating the glass at a temperature lower by 50 ° C. or more than the glass transition point (III) A second chemical strengthening step of further forming a compressive stress layer on the glass surface by ion exchange treatment of glass According to the present invention, it is possible to provide a chemically strengthened glass in which warpage is suppressed as much as possible.

  In the method for producing chemically strengthened glass of the present invention, the ion exchange treatment in steps (I) and (III) is preferably treatment at a temperature 50 ° C. or more lower than the glass transition temperature.

The method for producing a chemically strengthened glass according to the present invention includes the depth DOL ₁ of the compressive stress layer of the resulting chemically strengthened glass and the depth DOL of the compressive stress layer corresponding to a position that is half of the compressive stress CS ₀ of the outermost surface layer. It is preferable that _HM satisfy | fills following formula (2).
0.05 ≦ DOL _HM / DOL ₁ ≦ 0.4 (2)

It is a figure which shows the relationship of the compressive stress depth and compressive stress of chemical strengthening glass. It is a figure which shows the portable apparatus which has a sensor unit using the chemical strengthening glass (cover member) which concerns on this embodiment, Comprising: (A) is a perspective view, (B) is sectional drawing. It is a figure which shows the glass after chemical strengthening, and (A) is a perspective view, (B) is an example of B-B sectional drawing of (A), (C) is other than B-B sectional drawing of (A) An example of It is a figure which shows the relationship between (DELTA) S / t ² and the absolute value a of the quadratic term coefficient at the time of approximating the cross-sectional shape of chemical strengthening glass by a quadratic function.

[Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Composition of chemically strengthened glass]
First, the structure of the chemically strengthened glass will be described.
The chemically strengthened glass of the present embodiment is a plate-like chemically strengthened glass having two main surfaces, the thickness of the chemically strengthened glass is less than 1000 μm, and the following formulas (1) and (2) are satisfied. .
ΔS / t ² ≦ 4 × 10 ⁻³ (MPa / μm) (1)
0.05 ≦ DOL _HM / DOL ₁ ≦ 0.4 (2)
here,
ΔS = S × 0.015 (3)
S = (CS ₀ + HM_CS ₀ ) × DOL _HM × 0.5 (4)
CS ₀ : Compressive stress of outermost layer on one main surface (MPa)
HM_CS ₀ : Compression stress half of CS ₀ (MPa)
DOL ₁ : depth of the compressive stress layer on the one principal surface side (μm)
DOL _HM : Depth of compressive stress layer corresponding to HM_CS ₀ (μm)
t: Thickness of chemically strengthened glass (μm)

When the thickness of the chemically strengthened glass satisfying the above conditions is 300 μm or less, the relationship between the position in the surface direction of the two main surfaces in the thickness direction sectional view and the displacement in the thickness direction is approximated by a quadratic function The absolute value a of the quadratic term coefficient of the quadratic function is not more than 1.0 × 10 ⁻⁷ μm ⁻¹ .

Hereinafter, the technical significance of Formula (1) and Formula (2) is demonstrated with reference to FIG.
Since a compressive stress layer is formed on the surface of the chemically strengthened glass, if the compressive stress depth DOL (Depth Of Layer) is taken along the horizontal axis and the compressive stress value CS (Compressive Stress) corresponding to DOL is taken along the vertical axis. The relationship between DOL and CS is as shown by curve A in FIG.
In FIG. 1, it is considered that the area of the region surrounded by the vertical axis, the horizontal axis and the curve A, that is, the integral value of the curve A is correlated with the sum of the compressive stress values stored on one main surface of the chemically strengthened glass. Be

One of the causes of the warpage of the chemically strengthened glass is that the compressive stress value between the two main surfaces is different. Therefore, one major surface outermost layer of compressive stress (maximum value of compressive stress) when a CS _0, half of compressive stress CS ₀ and HM_CS _0, corresponds from the one main surface outermost layer to HM_CS ₀ The integral value (area S in FIG. 1) up to the depth DOL _HM was used as the compressive stress value in the vicinity of the surface of one main surface. However, at this time, the curve A in FIG. 1 was approximated by a straight line.
From the above, the area S in FIG. 1 is an area of a trapezoid having coordinates (0, 0), (DOL _HM , 0), (DOL _HM , HM_CS ₀ ), and (0, CS ₀ ) as apexes. It is required in

  Next, the compressive stress value of the two main surfaces of the chemically strengthened glass usually has a difference of about 1.5% due to a slight change in composition, a difference in cooling rate and the like caused by the manufacturing process. Therefore, the difference ΔS between S between the two main surfaces is expressed as the above-mentioned equation (3).

Further, in consideration of the influence of the thickness t of the entire glass on the easiness of chemical tempered glass to be influenced, the value ΔS / t ² was defined by dividing ΔS by t ² .
When this ΔS / t ² is 4 × 10 ⁻³ (MPa / μm) or less, warpage of the chemically strengthened glass is suppressed. The above is the ground of formula (1).
Incidentally, [Delta] S / t ² of the formula (1) varies depending calculating the S of formula (4) using either of the two main surfaces, one of the two major surfaces satisfy the equation (1) Even if it does not, if the other satisfies the formula (1), it is included in the present invention. In order to further suppress the warpage of the chemically strengthened glass, ΔS / t ² is preferably 3.5 × 10 ⁻³ (MPa / μm) or less, and more preferably 3 × 10 ⁻³ (MPa / μm) or less.

Moreover, in order to satisfy Formula (1), it is preferable to make S small.
However, as in Patent Document 1, when performing only the chemical strengthening of one step, CS, when you try to as large as possible DOL, it becomes a characteristic such as curve a _1, S is increased.
Also, small S, and when trying to enlarge the DOL, it becomes a characteristic such as the curve a _2, CS is reduced.
Also, small S, and when trying to enlarge the CS, it becomes a characteristic such as curve a _3, DOL is reduced.
Then, as a result of having examined, chemical strengthening of two or more steps is performed so that a formula of (2) may be satisfied, and it is considered as characteristic like curve A bent to the origin side than a case of one step of chemical strengthening We found that S can be reduced while maintaining CS and DOL. Thereby, the warpage of the chemically strengthened glass is suppressed.
The above is the basis of Formula (2).
From the viewpoint of reducing S as much as possible while maintaining CS and DOL, DOL _HM / DOL ₁ in the formula (2) is preferably 0.35 or less, more preferably 0.3 or less. The lower limit of CS ₀ (maximum value of compressive stress) main surface outermost layer of compressive stress is 500 MPa, preferably 550 MPa, 600 MPa is more preferable. This is to improve the surface strength of the glass. The upper limit of the CS ₀ is 1300 MPa, preferably 1200 MPa, 1100 MPa is more preferable. This is to prevent so-called "self-destruction cracking" of glass.
In the chemically strengthened glass of the present embodiment, the depth DOL ₁ of the main surface compressive stress layer is preferably 15 μm or more. This is because it is preferable that the value of DOL ₁ is large from the viewpoint of enhancing the impact resistance of the glass surface. DOL ₁ is, 20 [mu] m is more preferable, still more preferably 25 [mu] m, 30 [mu] m is particularly preferred. The upper limit of DOL ₁ is 100 μm, preferably 90 μm, more preferably 85 μm, and still more preferably 80 μm, depending on the thickness of the chemically strengthened glass. This is to prevent stress relaxation caused by the increase of the reinforcement time.

In the chemically strengthened glass of the present embodiment, the relative dielectric constant is preferably 7.5 or more.
With such a configuration, it is possible to provide a chemically strengthened glass in which warpage is suppressed as much as possible and sufficient sensing sensitivity can be obtained even when provided on a sensor.

In addition, the chemically strengthened glass lowers the dielectric constant due to the chemical strengthening. As described above, in order to obtain sufficient sensing sensitivity, it is preferable to suppress the decrease in relative dielectric constant.
Therefore, in the chemically strengthened glass of the present embodiment, it is preferable to satisfy the following formula (5).
(Ε ₂ −ε ₀ ) / ε ₂ ≦ 0.05 (5)
ε ₂ : relative permittivity of the unreinforced region of chemically tempered glass ε ₀ : relative permittivity of the entire chemically tempered glass

With such a configuration, it is possible to provide a chemically strengthened glass in which the decrease in relative permittivity due to chemical strengthening is suppressed.
The relative dielectric constant ε is a value at a frequency of 1 MHz, and can be obtained by measuring the capacitance of a capacitor configured by providing electrodes on both sides of a chemically strengthened glass. Here, the relative dielectric constant of the glass before chemical strengthening may be used as the relative dielectric constant of the unreinforced region.

In the chemically strengthened glass of the present embodiment, the thickness is preferably less than 400 μm.
With such a configuration, it is possible to reduce the weight of units and devices in which chemically strengthened glass is used.

[Method of producing chemically strengthened glass]
Next, a method of manufacturing the chemically strengthened glass of the present embodiment will be described.
Schematically, first, a glass is prepared, and chemical strengthening is first performed under the condition that the relationship shown by curve a ₂ as shown in FIG. 1 is obtained ((I) first chemical strengthening step), and then (II) after the heating step, and that a chemical strengthening in the conditions relationship shown by the curve a ₃ is obtained ((III) the second chemical strengthening process). According to such a manufacturing method, a chemically strengthened glass having a relationship such as curve A corresponding to a curve obtained by superposing curve a ₂ and curve a ₃ is obtained.

First, a method of producing a glass before chemical strengthening to be used is shown. Raw materials of respective components constituting the glass before chemical strengthening are prepared to have a desired composition, and are heated and melted in a glass melting furnace.
Next, the glass is homogenized by bubbling, stirring, addition of a clarifying agent, etc., and formed into a glass plate of a predetermined thickness (before chemical strengthening) by a conventionally known forming method and gradually cooled.
Thereafter, the formed glass is ground and polished as required, subjected to at least two chemical strengthening treatments, and washed and dried after each chemical strengthening treatment.

  (I) In the first chemical strengthening step of forming a compressive stress layer on the glass surface by ion exchange treatment of the glass, the alkali metal ion (eg, sodium ion, or the like) contained in the glass to be treated is contained in the glass Contact with a molten salt (eg, potassium salt or sodium salt) containing an alkali metal ion having a larger ion radius than lithium ion) in a temperature range not exceeding the transition temperature of glass. Then, the alkali metal ions in the glass and the alkali metal salt having a large ion radius of the alkali metal salt are ion-exchanged, and a compressive stress is generated on the glass surface due to the difference in occupied area of the alkali metal ions to form a compressive stress layer. The temperature range in which the glass is brought into contact with the molten salt may be any temperature range that does not exceed the transition temperature of the glass, but is preferably 50 ° C. or less from the glass transition point. This prevents stress relaxation of the glass.

In the chemical strengthening treatment, the treatment temperature and the treatment time for bringing the glass into contact with the molten salt containing an alkali metal ion can be appropriately adjusted according to the composition of the glass and the molten salt.
350 degreeC or more is preferable normally, and, as for the heating temperature of molten salt, 370 degreeC or more is more preferable. In addition, usually 500 ° C. or less is preferable, and 450 ° C. or less is more preferable.
By setting the heating temperature of the molten salt to 350 ° C. or higher, it is possible to prevent the chemical strengthening from becoming difficult due to the decrease of the ion exchange rate. Further, by setting the temperature to 500 ° C. or less, decomposition and deterioration of the molten salt can be suppressed.
The treatment time for bringing the glass into contact with the molten salt is generally preferably 10 minutes or more, more preferably 15 minutes or more, in order to provide sufficient compressive stress. In addition, since long-term ion exchange lowers the productivity and reduces the compressive stress value by relaxation, it is 20 hours or less, preferably 16 hours or less.

(II) In the heating step of heat treating the glass at a temperature lower by 50 ° C. or more than the glass transition point, the glass having the compressive stress layer formed on the glass surface obtained in step (I) is heat treated to compress the surface. It is a process of moving larger alkali metal ions, such as potassium ions, present in the stress layer from the surface of the glass to the inside of the glass.
The temperature at which the glass is heat-treated is lower than the glass transition temperature by 50 ° C. or more, preferably 70 ° C. or more, more preferably 100 ° C. or more. Thereby, stress relaxation of glass can be prevented and the omission of chemical strengthening can be suppressed.
Although the heat processing time of glass is suitably adjusted by heat processing temperature, it is preferable normally that it is 30 minutes-2000 minutes, and it is more preferable that it is 30 to 300 minutes.

(III) The second chemical strengthening step of forming a compressive stress layer on the surface of the glass by ion exchange treatment of the glass compresses the surface of the glass obtained in step (II) by ion exchange of the glass It is a process of further forming a stress layer. In step (III), ion exchange may be performed to form a compressive stress layer on the glass surface and the inside thereof.
The ion exchange treatment of step (III) may be carried out by the same method as the ion exchange treatment of step (I) or may be another method. Other molten salts may also be used.
Steps (I) to (III) in the present invention may be carried out sequentially on a continuous process, for example on a continuously moving glass ribbon in a glass plate manufacturing process, or may be carried out discontinuously on-line. Good.
By the above method, chemically strengthened glass having the above-mentioned characteristics is manufactured.

[Functional effects of chemically strengthened glass]
Since the chemically strengthened glass is configured to satisfy the formulas (1) and (2), it is possible to provide a chemically strengthened glass in which warpage is suppressed as much as possible.

[Portable devices using chemically strengthened glass]
The chemically strengthened glass of the present invention may be used in a smart phone as a portable device provided with a capacitive fingerprint sensor for fingerprint authentication as a sensor as shown in FIG.
As shown in FIG. 2A, the smartphone 30 includes a housing 32 which is open on one side, and a cover member 33 which is provided to close the opening of the housing 32. At a position facing the cover member 33 in the housing 32, a fingerprint authentication sensor 34 and a display element (not shown) are arranged.

The cover member 33 is made of the chemically strengthened glass of the present invention, and when the finger F approaches or contacts, the capacitance of the portion locally changes.
The fingerprint authentication sensor 34 includes a substrate 35 and a plurality of electrodes 36 provided on the substrate 35 at predetermined intervals, as shown in FIG. Detect fingerprints from changes in volume. Then, the cover member 33 is provided on the electrodes 36 of the fingerprint authentication sensor 34, whereby the fingerprint authentication sensor unit 31 as a sensor unit is configured. Although not shown in FIG. 2B, a plurality of electrodes 36 are provided on the substrate 35 at predetermined intervals also in the direction perpendicular to the paper surface.

  In such a fingerprint authentication sensor unit 31, when the finger F contacts the cover member 33, electric charges are accumulated between the finger F and the electrode 36 according to the unevenness of the fingerprint of the finger F. Here, as the distance between the finger F and the electrode 36 increases, the capacitance decreases and the amount of accumulated charge decreases. Therefore, in the valley (concave portion) F1 of the finger F, the distance between the valley (concave portion) F1 and the electrode 36 is large, so the amount of accumulated charge decreases. On the other hand, since the distance between the peak (convex part) F2 and the electrode 36 is small in the peak (convex part) F2 of the finger F, the amount of accumulated charge is large. By measuring the charge amount at each point generated in this manner and converting it into an image, the shape of the fingerprint is detected as an image. In addition, in detection, the capacitance of the cover member 33 may be changed, and the finger F may or may not be in contact with the cover member 33.

Although the fingerprint authentication sensor is exemplified as the sensor of the present invention, a capacitive touch sensor or an ultrasonic sensor may be used.
Although a portable device such as a smart phone has been exemplified as a device provided with the sensor unit of the present invention, it may be an apparatus such as an automated teller machine of a bank, a door lock of a car, or a personal authentication device such as entrance control into a building. Good. However, the fingerprint authentication sensor can be suitably used particularly for mobile devices such as a smartphone, a mobile phone, and a tablet personal computer.
Although the case where the chemically strengthened glass of the present invention is used as a cover member of a sensor is illustrated, it may be applied as a cover member of a device which does not have a sensor, a building material, a decorative member, a scratch resistant cover member, or the like. Furthermore, although the surface treatment such as an antiglare layer (AG layer), an antireflective layer (AR layer), a fingerprint resistant layer (AFP layer), etc. may be performed on at least one main surface of the chemically strengthened glass, the sensor cover When used as a member, the surface roughness of the cover member is important, so for example, the arithmetic average roughness Ra is preferably 1000 nm or less. The lower limit value of Ra is not particularly limited. Moreover, the printing layer and resin layer for decoration and concealment may be formed in one main surface of chemical strengthening glass.

  When the chemically strengthened glass of the present invention is used as a cover member of a sensor, the thickness t of the chemically strengthened glass shown in FIG. 2 (B) is less than 1.0 mm (1000 μm). According to the present invention, it becomes a chemically strengthened glass which can be reduced in weight while having strength. The thickness t is preferably less than 0.4 mm (400 μm), and more preferably 0.3 mm (300 μm) or less. This is a chemically strengthened glass that can be used as a cover glass with good sensing sensitivity that combines strength and weight reduction.

[Modification]
The present invention is not limited to the above embodiment, and various improvements and design changes can be made without departing from the scope of the present invention, and other specific procedures for practicing the present invention. The structure and the like may be other structures and the like as long as the object of the present invention can be achieved.

For example, as the glass to be subjected to the chemical strengthening treatment, a glass containing an alkali ion having a small ion radius (for example, an alkali metal ion having a smaller ion radius than potassium or an alkali metal ion having a smaller ion radius) can be used. Such a glass is SiO ₂ , Al ₂ O ₃ , Na ₂ O and MgO, or SiO ₂ , from the viewpoint of sufficiently imparting surface compressive stress and enabling the compressive stress layer to be deepened in a short time. It is preferable to contain Al ₂ O ₃ , Li ₂ O and MgO.

SiO ₂ is an essential component to form a glass skeleton.
Na ₂ O is a component that chemically strengthens the glass by being mainly replaced with potassium ions in the ion exchange treatment, controls the thermal expansion coefficient, and reduces the high temperature viscosity of the glass to enhance the meltability and the formability. .
Li ₂ O is a component that chemically strengthens the glass by being mainly replaced with sodium ions in ion exchange treatment, controls the thermal expansion coefficient, and reduces the high temperature viscosity of the glass to enhance the meltability and the formability. .
Al ₂ O ₃ is a component that has the effect of increasing the glass transition point Tg, the weather resistance, and the Young's modulus, and further improves the ion exchange performance of the glass surface.
MgO is a component that makes the glass resistant to scratching and improves the solubility of the glass.
ZrO ₂ is a component that improves the Young's modulus and improves the chemical durability and hardness of the glass, and it may be preferable to include it.

For example, a glass having the following composition can be used as the glass to be subjected to the chemical strengthening treatment.
(I) 50 to 80% of SiO ₂ , ₂ to 25% of Al ₂ O ₃ , 0 to 10% of Li ₂ O, 0 to 18% of Na ₂ O, and K ₂ O in the composition represented by mol% Composition containing 0-10% MgO, 0-15% MgO, 0-5% CaO and 0-5% ZrO ₂ (ii) mole% expressed as SiO ₂ , 50-74% SiO ₂ , Al 1 to 10% of ₂ O ₃ , 6 to 14% of Na ₂ O, 3 to 11% of K ₂ O, ₂ to 15% of MgO, 0 to 6% of CaO and 0 to 5% of ZrO ₂ , The total content of SiO ₂ and Al ₂ O ₃ is 75% or less, the total content of Na ₂ O and K ₂ O is 12 to 25%, and the total content of MgO and CaO is 7 to 15% a composition which is displayed at a certain glass (iii) mol%, a SiO ₂ 68 to 80%, the _Al 2 _{O 3 4~10%,} a ₂ O and 5 to 15%, _{K 2} O 0 to 1%, the MgO 4 to 15% and ZrO ₂ is composition displaying a glass (iv) mole% containing 0 to 1%, a SiO ₂ 67 75%, the _Al 2 _{O 3} 0 to 4%, a Na ₂ O 7 to 15%, the _{K 2} O 1 to 9%, the MgO having 6 to 14% and the ZrO ₂ contained 0 to 1.5% , The total content of SiO ₂ and Al ₂ O ₃ is 71 to 75%, the total content of Na ₂ O and K ₂ O is 12 to 20%, and when it contains CaO, the content is 1% the composition displaying a glass (v) mole percent is less than the _{SiO 2 60~75%, Al 2 O} 3 5-15%, the MgO 0 to 12%, 0 to 3% of CaO, a ZrO ₂ 0-3%, 10-20% of Li ₂ O, 0 to 8% of Na ₂ O, the _{K 2} O containing 0 to 5% _Li 2 O, a ₂ O and _{K 2} O content of total _{R 2} O is 25 percent or less, a ratio _{Li 2} O / _R 2 O content and _{R 2} O of Li ₂ O is 0.5 to 1.0 Glass (vi) a composition that displays by mol%, a SiO ₂ 61 to 72%, the _{Al 2 O 3 8~17%, 6~18} % of Li ₂ O, 2 to 15% of Na _{2 O, K} 2 O , 0 to 6% of MgO, 0 to 6% of CaO, 0 to 4% of TiO ₂ and 0 to 2.5% of ZrO ₂ , Li ₂ O, Na ₂ O and K ₂ Sum of content of O: R ₂ O: 15 to 25%, ratio of content of Li ₂ O to R ₂ O: Li ₂ O / R ₂ O: 0.35 to 0.8, content of MgO and CaO Glass with a total of 0-9%

  Examples of the glass forming method as described above include a float method, a pressing method, a fusion method, a downdraw method and a roll out method. In particular, the float method suitable for mass production is preferable. In addition, continuous molding methods other than the float method, that is, the fusion method and the downdraw method are also suitable. Moreover, when forming colored glass, the roll-out method may be optimal.

In the chemical strengthening step, the ion exchange treatment is not particularly limited as long as it is performed twice or more, but is preferably 3 times or less, more preferably 2 times, from the viewpoint of shortening tact time.
It is preferable to use a treatment salt containing at least potassium ion or sodium ion as the molten salt for performing the ion exchange treatment. As such a treated salt, for example, potassium nitrate or sodium nitrate is suitably mentioned. These treated salts may be subjected to steam addition, carbon dioxide addition, and the like.
In addition, the mixed molten salt may contain other components. Other components include, for example, alkali carbonates such as potassium carbonate, alkali sulfates such as sodium sulfate and potassium sulfate, and alkali chlorides such as sodium chloride and potassium chloride. In particular, a molten salt in which 1 to 10% by mass of potassium carbonate is mixed with potassium nitrate can be used. In this case, it may be used in the first chemical strengthening step or may be used after the second chemical strengthening step. Moreover, you may use the glass wash | cleaned after processing using the molten salt which mixed sodium nitrate and potassium nitrate for the glass which produces the chemical strengthening glass of this invention.

  The glass before or after chemical strengthening may be etched with acid or alkali. In the acid etching, an aqueous solution containing halogen, nitric acid, sulfuric acid, a mixed aqueous solution of these, etc. can be used. For example, an aqueous solution containing halogen can be used, and a hydrogen fluoride aqueous solution is preferable. It is preferable to remove about 1 to 20 μm from one side of the glass surface by etching. The thickness of the glass before chemical strengthening may be determined in consideration of this etching amount.

In the chemically strengthened glass of the present invention, the Vickers hardness is preferably 3500 N / mm ² or more and 10000 N / mm ² or less.
When the Vickers hardness is set to 3500 N / mm ² or more, the chemically strengthened glass is not easily damaged. Further, when the Vickers hardness is 10000 N / mm ² or less, it is possible to simultaneously achieve high hardness of the chemically strengthened glass and ease of processing, and to secure surface accuracy when increasing the area. Further, as a Vickers hardness, 3750N / mm ² or more 9000 N / mm ² more preferably less, 4000 N / mm ² or more 8500N / mm ² or less is particularly preferred.
The Vickers hardness can be measured, for example, by a Vickers hardness test described in Japanese Industrial Standard JIS Z 2244.

In the chemically strengthened glass of the present invention, the Young's modulus is preferably 40 GPa or more and 150 GPa or less.
When the Young's modulus is 40 GPa or more, sufficient strength can be secured. When the Young's modulus is 150 GPa or less, the strength and the processability of glass (in particular, the processability of polishing) can be compatible. Moreover, as a Young's modulus, 45 GPa or more and 140 GPa or less are more preferable, and 50 GPa or more and 130 GPa or less are especially preferable.

If chemically tempered glass of the present invention is used as a cover member for fingerprint authentication sensor, it is preferable area of the region facing the sensing portion of the fingerprint authentication sensor is 60 mm ² or more 41000Mm ² or less.
The area of the area facing the sensing area of the fingerprint authentication sensor (sensing area opposing area) is, for example, the area of the cover member 33 as shown in FIG. 2A, and the sensing area opposing area is less than 60 mm ² If there is, the false recognition may increase because the sensor area is small. On the other hand, if the facing area of the sensing part is larger than 41000 mm ^{2, the} area where the finger is not in contact becomes parasitic capacitance and not only does the sensing sensitivity fall, but it becomes difficult to make the surface accuracy uniform. There is a case. Further, as the sensing portion facing areas, and more preferably 80 mm ² or more 40500Mm ² or less, particularly preferably 100 mm ² or more 40000 mm ² or less.

If chemically tempered glass of the present invention is used as a sensor for fingerprint authentication, the value _A s / E obtained by dividing the sensing portion opposing area _{A s} Young's modulus E ^{is, 1.5 × 10 -7 m 2 /} GPa or more 1. It is preferably 4 × 10 ⁻² m ² / GPa or less.
When A _s / E is less than 1.5 × 10 ⁻⁷ m ² / GPa, the processability is deteriorated and chipping of the edge tends to occur. On the other _hand, when the _A s / E is at 1.4 × ¹⁰ -2 ^m 2 / GPa or more, the mechanical properties deteriorate and strength can not be guaranteed. _Further, as the ^{_{A s / E, 5.0 × 10}} -7 m is preferably 2 / GPa or more 1.0 × ¹⁰ -2 ^m 2 / GPa or ^{less, 1.0 × 10 -6 m 2 /} GPa or more It is especially preferable that it is 5.0 * 10 < ^-3 > m < ² > / GPa or less.

  Next, examples of the present invention will be described. However, the present invention is not limited to the following examples.

[Advance preparation]
First, a non-chemically reinforced aluminosilicate glass (trade name after chemical strengthening: Dragontrail X (registered trademark), manufactured by Asahi Glass Co., Ltd.) having a square main surface with a thickness of 2 mm (2000 μm) was prepared.
Next, both surfaces of the glass plate were mirror-finished so as to have a thickness of 100 μm, 150 μm, 200 μm, 250 μm, and 300 μm.

[Method of producing chemically strengthened glass]
Examples 1 to 5 are Examples, and Examples 6 to 9 are Comparative Examples.
[Example 1]
Among the prepared glass plates, those having a thickness of 100 μm were subjected to the first chemical strengthening treatment and the second chemical strengthening treatment to obtain the chemically strengthened glass of Example 1.

  In the first chemical strengthening treatment, potassium nitrate and sodium nitrate were used. It adjusted to a cup made of SUS so that potassium nitrate might be 60% by mass%, and heated to 450 ° C. by a mantle heater to prepare a molten salt of potassium nitrate. Then, a plate glass having a thickness of 100 μm was preheated to 400 ° C., immersed in molten salt for 15 hours to carry out ion exchange, and cooled to around room temperature to carry out the first chemical strengthening treatment. The resulting chemically tempered glass was washed with water and dried.

In the second chemical strengthening treatment, potassium nitrate (KNO ₃ ) was added to a SUS cup and heated to 400 ° C. with a mantle heater to prepare a molten salt of potassium nitrate. The plate glass subjected to the first chemical strengthening treatment was preheated to 350 ° C., immersed in molten salt for 10 minutes to perform ion exchange, and cooled to around room temperature to perform a second chemical strengthening treatment. The resulting chemically tempered glass was washed with water and dried.

[Examples 2 to 5]
In Examples 2 to 5, the glass plates having thicknesses of 150 μm, 200 μm, 250 μm, and 300 μm were treated in the same procedure and conditions as in Example 1 to obtain chemically strengthened glass.

[Examples 6-9]
In Examples 6 to 9, in the first chemical strengthening treatment, the glass plate was immersed in molten salt at 425 ° C. for 24 hours for 24 hours in a glass plate with a thickness of 100 μm, 150 μm, 200 μm, and 250 μm respectively, and then raised continuously to 450 ° C. The treatment was performed in the same manner as in Example 1 except that the solution was warmed and dipped for additional 4 hours and the second chemical strengthening treatment was not performed, to obtain a chemically strengthened glass.

[Evaluation method]
Various evaluations were performed by the analysis method shown below.
[Evaluation of glass: surface compressive stress (CS) and surface compressive stress layer depth (DOL)]
The surface compressive stress (CS) of the chemically strengthened glass and the depth (DOL) of the surface compressive stress layer (hereinafter referred to as stress distribution) were measured by a glass surface stress meter device (FSM-6000LE) manufactured by Orihara Mfg.

In the calculated stress distribution, the stress value (unit: MPa) at a glass depth of 0 μm from the outermost surface was taken as the compressive stress (CS ₀ ) of the outermost layer on one main surface of the chemically strengthened glass. In addition, the glass depth (unit: μm) at which the stress value is 0 MPa inside the glass was taken as the depth (DOL ₁ ) of the compressive stress layer on the one main surface side. Furthermore, a half value (HM_CS ₀ , unit is MPa) of the stress value corresponding to CS ₀ is determined, and the glass depth corresponding to this HM_CS ₀ is taken as DOL _HM (unit is μm).

Based on these data and the above equation (1), DOL _HM / DOL ₁ and stress profile integral value (area S in FIG. 1) were calculated.
In addition, the compressive stress on the front and back of the chemically strengthened glass has a difference of about 1.5% due to slight composition fluctuation caused by the manufacturing process and a difference in cooling rate, so ΔS = S × 0.015 The stress profile integral value difference ΔS on the back surface was determined, and ΔS / t ² was calculated from the thickness t of the glass plate. The results are shown in Table 1.

(Evaluation of glass: Evaluation of warpage)
The warpage of the glass was evaluated in the following procedure using a laser displacement meter LT-9030M manufactured by KEYENCE.
First, in the glass after chemical strengthening as shown to FIG. 3 (A), BB cross section was selected as a position which evaluates curvature. In addition, although a BB cross section is not limited to a specific position, it was set as the cross section which passes along the gravity center of glass here. When a BB cross section is illustrated, it becomes an upwardly convex shape as shown in FIG. 3 (B) or a downwardly convex shape shown in FIG. 3 (C).
Next, it arrange | positioned in the holding | maintenance part by making any surface of a glass substrate into a lower surface, and acquired the shape data of the cross section using the laser displacement meter. In the obtained shape data, a point at which the sign of the slope of the tangent changes changes is taken as the origin O, and the cross-sectional shape is approximated by a quadratic function y = ax ² as the warp direction y and the sheet width direction x. Here, the units of y and x are each μm, and the unit of the second-order term coefficient a is μm ⁻¹ .
Finally, the quadratic term coefficient a of the quadratic function was determined, and warpage was evaluated based on the quadratic term coefficient a.
The results are shown in Table 1. In addition, "○" of warpage evaluation shows the case where the quadratic term coefficient a is 1 × 10 ^-7 μm ^-1 or less, and the "×" of warpage evaluation exceeds the quadratic term coefficient a exceeding 1 × 10 ^-7 μm ^-1 Indicates the case.

(Evaluation of glass: relative permittivity)
The relative dielectric constant of glass was simply estimated as follows. First, as a reference example, 0.55 mm thick aluminosilicate glass (unreinforced Dragontrail X (registered trademark), manufactured by Asahi Glass Co., Ltd.) with a relative dielectric constant of 8.3 at 1 MHz and CS = 1100 MPa for each surface It was 8.1 when the chemical strengthening of DOL = 25 micrometers was given and the dielectric constant was measured again. In addition, S of the reference example was 13750 MPa · μm.

The average synthesis capacity C ₁ of the chemically strengthened 50 μm region has the following relation, where the synthesis capacity of the unreinforced region is C ₂ , and the synthesis capacity of the entire chemically strengthened glass is C ₀ .
C ₀ = C ₁ × C ₂ / (C ₁ + C ₂ ) (X)
The relative dielectric constant ε has the following relation to the combined capacitance C and the thickness t.
ε _k = C _k / t _k (Y)
However, k = 0, 1, 2
In the region of 50 μm chemically strengthened from the relationship of Formula (X) and Formula (Y), with ε ₀ = 8.1, ε ₂ = 8.3, t ₀ = 550, t ₁ = 50, t ₂ = 500 The relative dielectric constant ε ₁ was estimated to be ε ₁ = 6.5.
Hereinafter, the relative permittivity of the reinforced region of the chemically strengthened glass is ε ₁ = 6.5, and the relative permittivity of the unreinforced region is ε ₂ = 8.3, and the formula (X), the formula (Y), the reference example Based on S of Examples 1 to 9 and CS, DOL, CS ₀ , DOL ₁ and S of Examples 1 to 9 and the reduction of the relative dielectric constant indicated by the relative dielectric constants ε ₀ and (ε ₂ −ε ₀ ) / ε ₂ of Examples 1 to 9 The rate was calculated.

The above results are shown in Table 1. In Table 1, “○” in the relative dielectric constant reduction rate evaluation indicates “×” when the relative dielectric constant reduction rate is 5% or less ((ε ₂ −ε ₀ ) / ε ₂ ≦ 0.05). Indicates a case where the decrease rate of the relative permittivity exceeds 5%.

Furthermore, FIG. 4 shows the result of plotting a logarithmic graph by plotting ΔS / t ² in Table 1 on the horizontal axis and the quadratic term coefficient a on the vertical axis.
As shown in Table 1 and FIG. 4, in Examples 1 to 5, ΔS / t ² is 4 × 10 ⁻³ MPa / μm or less, and the quadratic term coefficient a is 1.0 × 10 ⁻⁷ μm ⁻¹ or less. It was found that warpage was suppressed even after strengthening. On the other hand, in Examples 6 to 9, it was found that ΔS / t ² exceeded 4 × 10 ⁻³ MPa / μm and the quadratic term coefficient a exceeded 1.0 × 10 ⁻⁷ μm ⁻¹ and warpage was not suppressed. . In Examples 1 to 5, DOL _HM / DOL ₁ was 0.05 or more and 0.4 or less, but in Examples 6 to 9, DOL _HM / DOL ₁ did not satisfy the above conditions.
From the above, it was found that it is sufficient to satisfy the above formulas (1) and (2) in order to suppress warpage as much as possible in chemically strengthened glass. In addition, in order to produce such a chemically strengthened glass, it has been found that two-stage strengthening is effective.
Furthermore, in Examples 1-5, it turned out that a fall of a dielectric constant can be suppressed rather than Examples 6-9.

  Reference Signs List 30 smartphone (mobile device) 31 fingerprint-sensing sensor unit (sensor unit) 33 cover member (chemically reinforced glass) 34 fingerprint-sensing sensor (sensor) 35 substrate 36 electrode

Claims (11)

Chemically strengthened glass having two main surfaces,
Chemically tempered glass characterized in that the thickness of the chemically tempered glass is less than 1000 μm and the following formulas (1) and (2) are satisfied.
ΔS / t ² ≦ 4 × 10 ⁻³ (MPa / μm) (1)
0.05 ≦ DOL _HM / DOL ₁ ≦ 0.4 (2)
here,
ΔS = S × 0.015 (3)
S = (CS ₀ + HM_CS ₀ ) × DOL _HM × 0.5 (4)
CS ₀ : Compressive stress of outermost layer on one main surface (MPa)
HM_CS ₀ : Compression stress half of CS ₀ (MPa)
DOL ₁ : depth of the compressive stress layer on the one principal surface side (μm)
DOL _HM : Depth of compressive stress layer corresponding to HM_CS ₀ (μm)
t: Thickness of chemically strengthened glass (μm) The chemically strengthened glass according to claim 1, wherein DOL ₁ is 15 μm or more.   The chemically strengthened glass according to claim 1 or 2, wherein the relative dielectric constant is 7.5 or more. The chemically strengthened glass according to any one of claims 1 to 3, which satisfies the following formula (5).
(Ε ₂ −ε ₀ ) / ε ₂ ≦ 0.05 (5)
ε ₂ : relative permittivity of the unreinforced region of chemically tempered glass ε ₀ : relative permittivity of the entire chemically tempered glass   The chemically strengthened glass according to any one of claims 1 to 4, which has a thickness of less than 400 μm. Chemically strengthened glass having two main surfaces,
Thickness is 300 μm or less,
When the relationship between the position in the surface direction of the two main surfaces and the displacement in the thickness direction is approximated by a quadratic function in a thickness direction sectional view, the absolute value a of the quadratic term coefficient of the quadratic function is 1. Chemically strengthened glass characterized by having a size of 0 × 10 ⁻⁷ μm ⁻¹ or less. Sensor,
A sensor unit comprising the chemically strengthened glass according to any one of claims 1 to 6.   A mobile device comprising the sensor unit according to claim 7. The depth DOL ₁ of the compression stress layer on one principal surface side of the obtained chemically strengthened glass is 15 μm or more, and the compression stress CS on the outermost surface of one principal surface is sequentially included, including the following steps (I) to (III) _A method for producing a chemically strengthened glass, wherein ₀ is 500 MPa or more and the thickness is less than 1000 μm.
(I) A first chemical strengthening step of forming a compressive stress layer on the glass surface by ion exchange treatment of glass (II) A heating step of heat treating the glass at a temperature 50 ° C. or more lower than the glass transition point (III) The second chemical strengthening step of forming a compressive stress layer on the glass surface by ion exchange treatment of the glass   The method for producing a chemically strengthened glass according to claim 9, wherein the ion exchange treatment in steps (I) and (III) is a treatment at a temperature 50 ° C or more lower than the glass transition temperature. The depth DOL _HM of the compressive stress layer corresponding to a position at which the depth DOL ₁ of the compressive stress layer of the resulting chemically strengthened glass and the compressive stress CS ₀ of the outermost surface of the major surface is ₀ satisfy the following formula (2) The manufacturing method of the chemically strengthened glass as described in 9 or 10.
0.05 ≦ DOL _HM / DOL ₁ ≦ 0.4 (2)

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