WO2014084096A1

WO2014084096A1 - Reinforced glass and method for manufacturing same

Info

Publication number: WO2014084096A1
Application number: PCT/JP2013/081264
Authority: WO
Inventors: 文山本; 博之大川; 山中　一彦
Original assignee: 旭硝子株式会社
Priority date: 2012-11-30
Filing date: 2013-11-20
Publication date: 2014-06-05
Also published as: TW201431820A

Abstract

The purpose of the present invention is to provide a reinforced glass in which the strength of the glass is prevented in an effective manner from decreasing after reinforcement. The present invention pertains to a reinforced glass characterized in that a compressive stress layer is present on the surface layer and the maximum hydrogen concentration in the region within a depth of 10 μm from the outermost surface of the compressive stress layer is no greater than five times the minimum hydrogen concentration at a depth of 10 μm from the outermost surface.

Description

Tempered glass and method for producing the same

The present invention relates to tempered glass and a method for producing the same.

In recent years, in flat panel display devices such as mobile phones or personal digital assistants (PDAs), display protection and improvement in aesthetics have been demanded. For this reason, a thin plate-like cover glass is disposed on the front surface of the display so as to be a wider area than the image display portion. Such flat panel display devices are required to be lightweight and thin, and therefore, it is also required to reduce the thickness of cover glass used for display protection.

However, as the thickness of the cover glass is reduced, the strength decreases, and the cover glass itself may be broken due to dropping during use or carrying. The crack of the cover glass has a problem that the original function of protecting the display device cannot be performed. For this reason, in order to improve the scratch resistance, the conventional cover glass is strengthened by chemical strengthening or physical strengthening to form a compressive stress layer on the surface to enhance the scratch resistance.

As a method for producing a glass having a high strength even though the glass is thin, Patent Document 1 discloses that the ion exchange layer having a potassium ion concentration exceeding 5000 ppm in the surface layer of the chemically strengthened glass substrate is removed thereafter. A method is disclosed in which potassium ions are not ion-exchanged with hydronium ions at the time of cleaning, and thus the strength of the glass is increased by preventing the formation of a tensile stress layer that causes a decrease in strength.

Japanese Unexamined Patent Publication No. 2011-105598

The present inventors have found that the strength of the glass may decrease after chemical strengthening, the main cause of which is that chemical defects are generated when moisture in the atmosphere enters the glass. Moreover, it discovered that this phenomenon generate | occur | produces not only through chemical strengthening but through a temperature rising process in the glass manufacturing process.

Therefore, an object of the present invention is to provide a tempered glass that effectively suppresses a reduction in the strength of the glass after tempering.

The present inventors have a correlation between the hydrogen profile in the surface layer of tempered glass and the strength of the glass, and by making the hydrogen concentration in the surface layer of the tempered glass into a specific range, the surface strength of the glass is dramatically improved. As a result, the present invention has been completed.

That is, the present invention is as follows.
1. The surface layer has a compressive stress layer, and the maximum hydrogen concentration in a region within 10 μm depth from the outermost surface of the compressive stress layer is not more than 5 times the minimum hydrogen concentration of 10 μm depth from the outermost surface. Tempered glass.
The maximum hydrogen concentration in the region within 10 μm depth from the outermost surface of the compressive stress layer and the lowest hydrogen concentration of 10 μm depth from the outermost surface are values measured under the following analytical conditions.
(Analysis conditions)
Measuring device: Secondary ion mass spectrometer having a quadrupole mass analyzer Primary ion species: Cs ⁺
Primary acceleration voltage: 5.0 kV
Primary ion current: 500 nA
Primary ion incident angle (angle from the direction perpendicular to the sample surface): 60 °
Raster size: 300 × 300 μm ²
Detection area: 12 × 12 μm ²
Secondary ion polarity: Use of electron gun for negative neutralization 2. 2. The tempered glass according to item 1, wherein the compressive stress layer is formed by an ion exchange method.
3. 3. The tempered glass according to

item

1 or 2, wherein the compressive stress layer has a compressive stress value of 400 MPa or more.
4). 4. The tempered glass according to any one of items 1 to 3, which is made of alkali aluminosilicate glass or soda lime glass.
5. A ball that places a glass plate on a ring made of stainless steel with a diameter of 30 mm, and that loads the sphere to the center of the ring under static load conditions with a sphere made of steel with a diameter of 10 mm in contact with the glass plate 5. The tempered glass according to any one of the preceding items 1 to 4, wherein a BOR strength F (N) measured by an on-ring test satisfies the following formula.
F ≧ 1000 × t ²
[Wherein, F is the BOR strength (N) measured by the ball-on-ring test, and t is the thickness (mm) of the glass plate. ]
6). In a falling ball test in which a glass plate is placed on a stainless steel base and a sphere made of stainless steel having a diameter of 10 mm is dropped from above, the falling ball strength E (J) calculated by the following formula is E ≧ 1.0 × t ^2. 6. The tempered glass according to any one of the preceding items 1 to 5, wherein
Falling ball strength E (J) = sphere mass (kg) × gravity acceleration (9.81 m / s ² ) × destruction height (m)
[Where E is the falling ball strength (J) measured by the falling ball test, and t is the thickness (mm) of the glass plate. ]
7). A molten salt containing KNO ₃ is brought into contact with glass to form a compressive stress layer on the glass surface, and then the maximum hydrogen concentration in the region within 10 μm depth from the outermost surface of the compressive stress layer has a depth from the outermost surface. A method for producing a tempered glass, comprising removing a hydrogen-containing layer exceeding 5 times the minimum hydrogen concentration of 10 μm.
The hydrogen concentration in a region within 10 μm depth from the outermost surface of the compressive stress layer and the lowest hydrogen concentration at a depth of 10 μm from the outermost surface are values measured under the following analytical conditions.
(Analysis conditions)
Measuring device: Secondary ion mass spectrometer having a quadrupole mass analyzer Primary ion species: Cs ⁺
Primary acceleration voltage: 5.0 kV
Primary ion current: 500 nA
Primary ion incident angle (angle from the direction perpendicular to the sample surface): 60 °
Raster size: 300 × 300 μm ²
Detection area: 12 × 12 μm ²
Secondary ion polarity: use of electron gun for negative neutralization 8. The method for producing tempered glass according to 7 above, wherein the removal of the hydrogen-containing layer is performed by polishing or etching.

In the tempered glass of the present invention, since the generation of defects due to moisture entering the glass is suppressed due to the hydrogen concentration of the surface layer being in a specific range, it is possible to suppress a decrease in strength after tempering, Shows high strength.

FIG. 1 is a schematic diagram for explaining a ball-on-ring test method. FIG. 2 is a schematic diagram for explaining the method of the falling ball test. FIG. 3 is a cross-sectional view of a flat panel display device using the tempered glass of the present invention as a cover glass for the flat panel display device. FIG. 4A is a diagram showing the BOR intensity before and after polishing after strengthening. FIG. 4B is a diagram showing the hydrogen concentration in the glass surface layer before and after polishing after strengthening. FIG. 5A is a diagram showing the correlation between the post-strengthening polishing amount and the BOR intensity. FIG. 5B is a diagram showing the correlation between the post-strengthening polishing amount and the falling ball strength (BD strength). FIG. 6A is a diagram showing the correlation between the heat treatment temperature of the tempered glass and the BOR strength. FIG.6 (b) is a figure which shows the hydrogen concentration in the glass surface layer before and behind heat processing of tempered glass. FIG. 7 is a diagram showing the correlation between the hydrogen profile and the BOR intensity in the glass surface layer after the heat treatment. FIG. 8 is a graph showing the correlation between the plate thickness and the BOR intensity. FIG. 9 is a graph showing the correlation between the plate thickness and the falling ball strength.

[Tempered glass]
The present inventors have found that the surface strength is reduced by heat treatment in the atmosphere both when the glass is strengthened and when it is not strengthened. The relationship between the decrease in strength due to heat treatment, the chemical composition change on the glass surface, and the formation of chemical defects was investigated by secondary ion mass spectrometry (SIMS). Changed. On the other hand, there was no chemical composition change on the glass surface before and after the heat treatment. Therefore, it is considered that the decrease in strength due to the heat treatment is due to a change in the hydrogen profile in the glass surface layer.

The penetration depth of hydrogen into the glass depends on the diffusion coefficient, temperature and time, and the penetration amount of hydrogen is influenced by the moisture content in the atmosphere in addition to these. As a result of examining the correlation between the hydrogen profile area (hydrogen concentration) and the strength of the glass, the present inventors have found that the higher the hydrogen concentration of the glass, the lower the strength.

When the hydrogen concentration in the glass is high, hydrogen enters the Si—O—Si bond network of the glass in the form of SiOH, and the Si—O—Si bond is broken. If the hydrogen concentration in the glass is high, it is considered that the Si—O—Si bond is cut off more, chemical defects are easily generated, and the strength is lowered.

In the present invention, since it is difficult to accurately measure the hydrogen concentration itself, [ ¹ H ⁻ / ³⁰ Si ⁻ ] proportional to the hydrogen concentration is used as a direct indicator of the hydrogen concentration.

Here, in this specification, [ ¹ H ⁻ / ³⁰ Si ⁻ ] is a value measured under the following analytical conditions.
(Analysis conditions)
Measuring device: Secondary ion mass spectrometer having a quadrupole mass analyzer Primary ion species: Cs ⁺
Primary acceleration voltage: 5.0 kV
Primary ion current: 500 nA
Primary ion incident angle (angle from the direction perpendicular to the sample surface): 60 °
Raster size: 300 × 300 μm ²
Detection area: 12 × 12 μm ²
Secondary ion polarity: Use of electron gun for negative neutralization

More specifically, the sputtering rate is 150 nm / sec.

Next, [ ¹ H ⁻ / ³⁰ Si ⁻ ] will be described. The secondary ion intensity I _M1 of the isotope M ₁ of the element M in secondary ion mass spectrometry is the primary ion intensity I _P , the sputtering rate Y of the matrix, the concentration _M M of the element _M (ratio to the total concentration), and the isotope M. _It is proportional to the existence probability α _{1 of 1} , the secondary ionization rate β _{M of} the element M, and the transmission efficiency η (including the detection efficiency of the detector) of the mass spectrometer.
I _M1 = A · I _P · Y · C _M · α ₁ · β _M · η (Formula 1)

Here, A is the ratio of the secondary ion detection area to the scanning range of the primary ion beam. In general, it is impossible to determine the absolute value for the hard beta _M determine the η devices. Therefore, η is eliminated by using a main component element or the like in the same sample as a reference element and taking a ratio with (Equation 1).

Here, when the reference element is R and its isotope is R _j , (Formula 2) is obtained.
I _M1 / I _Rj = (C _M · α ₁ · β _M ) / (C _R · α _j · β _R ) = C _M / K (Formula 2)
Here, K is a relative sensitivity factor of the element M with respect to the element R.
K = ( _CR * [alpha] _j * [beta] _R ) / ([alpha] ₁ * [beta] _M ) (Formula 3)
In this case, the concentration of the element M is obtained from (Equation 4).
C _M = K · I _M1 / I _Rj (Formula 4)

In the present invention, ¹ H ⁻ corresponds to M ₁ and ³⁰ Si ⁻ corresponds to R _j . Therefore, from (Equation 2), the intensity ratio [ ¹ H ⁻ / ³⁰ Si ⁻ ] is equal to the hydrogen concentration C _M divided by K. That is, [ ¹ H ⁻ / ³⁰ Si ⁻ ] is a direct indicator of the hydrogen concentration.

As a secondary ion mass spectrometer having a quadrupole mass spectrometer, for example, ADEPT 1010 manufactured by ULVAC-PHI can be mentioned.

The tempered glass of the present invention has a compressive stress layer on the surface layer, and the maximum hydrogen concentration in a region within 10 μm depth from the outermost surface of the compressive stress layer is 5 times or less than the minimum hydrogen concentration of 10 μm depth from the outermost surface. It is characterized by being. The maximum hydrogen concentration in the region within 10 μm depth from the outermost surface of the compressive stress layer is not more than 5 times, preferably not more than 3 times, and preferably not more than 2 times the minimum hydrogen concentration of 10 μm depth from the outermost surface. It is more preferable. If the maximum hydrogen concentration in the region within 10 μm depth from the outermost surface of the compressive stress layer is more than five times the minimum hydrogen concentration of 10 μm depth from the outermost surface, the surface strength of the tempered glass decreases.

The maximum hydrogen concentration and the minimum hydrogen concentration in a region within a depth of 10 μm from the outermost surface of the compressive stress layer are the values of [ ¹ H ⁻ / ³⁰ Si ⁻ ] measured under the analysis conditions.

In order to make the effect of strength improvement by strengthening effective, the compressive stress value of the compressive stress layer is preferably 400 MPa or more, more preferably 500 MPa or more, and further preferably 600 MPa or more. .

Further, when the tempered glass of the present invention is a chemically tempered glass, the depth of the compressive stress layer is preferably 10 μm or more in order to make the effect of improving the strength by chemical strengthening effective. In addition, if a scratch exceeding the depth of the compressive stress layer occurs during use, the glass will be broken. Therefore, the compressive stress layer is preferably deeper, more preferably 20 μm or more, further preferably 30 μm or more, typically 30 μm or more. It is.

On the other hand, if the compressive stress layer becomes too deep, the internal tensile stress increases and the impact at the time of failure increases. That is, when the internal tensile stress is large, there is a tendency that when the glass breaks, it becomes a fine piece and is shattered. Therefore, the depth of the compressive stress layer is preferably 70 μm or less.

The compressive stress value of the compressive stress layer and the depth of the compressive stress layer of the chemically tempered glass of the present invention are determined by an electron probe microanalyzer (EPMA) or a surface stress meter (for example, FSM- manufactured by Orihara Seisakusho). 6000) or the like.

The surface roughness Ra of the surface layer in the tempered glass of the present invention is preferably 0.1 to 10 nm, and more preferably 0.2 to 3 nm. When the surface roughness Ra of the compressive stress layer is 0.2 to 3 nm, when a film such as a functional film is attached to the glass surface after strengthening, the film and the glass are likely to be in close contact with each other. There is an advantage that it is difficult to peel off. Here, Ra is measured by an atomic force microscope (AFM) at a measurement size of 10 * 10 μm and a scan rate of 1 Hz.

〔Evaluation methods〕
The strength of the tempered glass of the present invention can be evaluated by a ball-on-ring test and a falling ball test.

(Ball-on-ring test)
The tempered glass of the present invention is a state in which a glass plate is disposed on a ring made of stainless steel having a diameter of 30 mm and a contact portion having a radius of curvature of 2.5 mm, and a sphere made of steel having a diameter of 10 mm is brought into contact with the glass plate. The BOR strength F (N) measured by a ball-on-ring test in which the sphere is loaded at the center of the ring under a static load condition is F ≧ 1000 × t ² [where F is measured by a ball-on-ring test. BOR strength (N), and t is the plate thickness (mm) of the glass substrate. ] Is preferable, and it is more preferable that F ≧ 1240 × t ² . When the BOR strength F (N) is F ≧ 1000 × t ² , excellent strength is exhibited even when the plate is thinned.

FIG. 1 shows a schematic diagram for explaining the BOR test used in the present invention. In the ball-on-ring (BOR) test, the glass plate 1 is pressed using a pressure jig 2 made of SUS304 with the glass plate 1 placed horizontally, and the strength of the glass plate 1 is measured. To do.

In FIG. 1, a glass plate 1 as a sample is horizontally installed on a receiving jig 3 made of SUS304. Above the glass plate 1, a pressurizing jig 2 for pressurizing the glass plate 1 is installed.

In the present embodiment, the central region of the glass plate 1 is pressurized from above the glass plate 1. The test conditions are as follows.
Sample thickness: 1.1 (mm)
Lowering speed of the pressure jig 2: 1.0 (mm / min)

(Falling ball test)
The tempered glass of the present invention has a falling ball strength E (J determined by the following formula in a falling ball test in which a glass plate is placed on a base made of stainless steel and a sphere made of stainless steel having a diameter of 32 mm is dropped onto the glass plate from above. ) Preferably satisfies E ≧ 1.0 × t ^2, and more preferably E ≧ 1.7 × t ² . When E ≧ 1.0 × t ² , excellent strength is exhibited even when thinned.
Falling ball strength E (J) = sphere mass (kg) × gravity acceleration (9.81 m / s ² ) × breaking height (m) [where E is the falling ball strength (J) measured by the falling ball test, t is the thickness (mm) of the glass substrate. ]

FIG. 2 shows a schematic diagram for explaining the falling ball test used in the present invention. In the falling ball test, a glass plate 5 is placed on a base 4 made of stainless steel, and a sphere 6 made of stainless steel is dropped onto the glass plate 5 from above, and the strength of the glass plate 5 is evaluated.

As a specific test method, the glass plate 5 is placed on a base 4 made of SUS304 (100 × 100 × 10 × 10 mm thick metal plate having a 40 × 40 mm hollow portion in the center). A sphere 6 (made of SUS304) having a mass of 130 kg is dropped on the center of the glass plate 5, and the falling ball strength is calculated from the height (destruction height) when the sphere 6 is dropped when the glass plate 5 is broken by the above formula. Find (J).

[Method for producing tempered glass]
(Glass composition)
As the tempered glass of the present invention, glass having various compositions can be used as long as it has a composition that can be tempered by a tempering treatment and formed by a float method or a downdraw method.

Specifically, for example, a transparent glass plate made of aluminosilicate glass, soda lime glass, borate glass, lithium aluminosilicate glass, borosilicate glass, non-alkali glass, and other various glasses.

Although the tempered glass of this invention shows the outstanding intensity | strength irrespective of a composition, the glass of the following compositions is mentioned, for example.
(I) The composition expressed in mol% is SiO ₂ 55-75%, Al ₂ O ₃ 5-15%, Li ₂ O 0-15%, Na ₂ O 10-20%, K ₂ O Is represented by a glass (ii) mol% containing 0 to 10%, MgO 0 to 15%, CaO 0 to 5% and ZrO ₂ 0 to 5%, SiO ₂ 55 to 75%, Al ₂ O ₃ 0-15%, Li ₂ O 0-20%, Na ₂ O 0-15%, MgO 0-5%, CaO 0-5% and ZrO ₂ 0-5% composition displaying a glass (iii) mol%, a SiO ₂ 68 ~ 80%, the _{_{Al 2 O 3 4 ~ 10%}} , a Na ₂ O 5 ~ 15%, the _{K 2} O 0 ~ 1%, of MgO 4-15% and ZrO ₂ is composition displaying a glass (iv) mole% containing 0 to 1%, a SiO ₂ 60 ~ 80%, a Including ₂ O ₃ 0-5%, a Na ₂ O 5 ~ 15%, the _{K 2} O 0-5%, the MgO 0 ~ 10%, the CaO 0 ~ 10% and the ZrO ₂ and 0-5% Glass

(Tempered glass)
The tempered glass of the present invention includes a tempered glass by chemical tempering and a tempered glass by physical tempering, and the tempering method is not particularly limited, but is a tempered glass by chemical tempering in which a compressive stress layer is formed by ion exchange method Is preferred.

In the ion exchange method, the surface of the glass is ion-exchanged to form a surface layer in which compressive stress remains. Specifically, alkali metal ions (typically Li ions, Na ions) having a small ion radius on the surface of the glass plate by ion exchange at a temperature below the glass transition point are converted to alkali ions (typically Is substituted for Na ions or K ions for Li ions and K ions for Na ions. Thereby, compressive stress remains on the surface of the glass, and the strength of the glass is improved.

Conditions and methods for chemical strengthening are not particularly limited, and known methods can be used. The chemical strengthening method is not particularly limited as long as Li ₂ O or Na ₂ O on the glass surface layer and Na ₂ O or K ₂ O in the molten salt can be ion-exchanged. For example, heated potassium nitrate (KNO) ₃ ) The method of immersing glass in the molten salt containing is mentioned.

The conditions of the ion exchange treatment for forming a chemically strengthened layer (surface compressive stress layer) having a desired surface compressive stress on the glass vary depending on the thickness of the glass, but the temperature condition is preferably 520 ° C. or lower. 500 ° C. or lower, more preferably 350 ° C. or higher, and more preferably 400 ° C. or higher.

The ion exchange treatment time is preferably 1 to 72 hours, and more preferably 2 to 24 hours. In order to improve productivity, 12 hours or less is more preferable. Examples of the molten salt include KNO ₃ .

Specifically, for example, a method of immersing glass in KNO ₃ molten salt at 400 to 500 ° C. for 1 to 72 hours is typical. Moreover, after chemical strengthening, it is preferable to wash with water for the purpose of removing deposits such as molten salt adhering to the glass plate.

The tempered glass of the present invention can be produced by forming a compressive stress layer on the glass surface and then removing the hydrogen-containing layer on the surface layer of the compressive stress layer. Here, the hydrogen-containing layer is a layer in which the maximum hydrogen concentration in a region within 10 μm depth from the outermost surface of the compressive stress layer exceeds 5 times the minimum hydrogen concentration of 10 μm depth from the outermost surface. The hydrogen concentration of the hydrogen-containing layer is a value measured under the following analytical conditions.

(Analysis conditions)
Measuring device: Secondary ion mass spectrometer having a quadrupole mass analyzer Primary ion species: Cs ⁺
Primary acceleration voltage: 5.0 kV
Primary ion current: 500 nA
Primary ion incident angle (angle from the direction perpendicular to the sample surface): 60 °
Raster size: 300 × 300 μm ²
Detection region: 12 × 12 [mu] m ² secondary ion polarity: an electron gun using perforated for minus neutralizing

Examples of the method for removing the hydrogen-containing layer include polishing or etching.

(Polishing)
The polishing method is not limited. For example, rare earth oxides such as cerium oxide, zirconium oxide, aluminum oxide, magnesium oxide, silicon oxide (including colloidal silica), silicon carbide, manganese oxide, iron oxide, diamond, boron nitride, and zircon. The method of grind | polishing glass using the slurry containing abrasive grains, such as these is mentioned. These abrasive grains may be used alone or in combination of two or more.

In the above-mentioned group of abrasive grains, similarly to the above-described step of removing the surface heterogeneous layer, polishing with a slurry containing colloidal silica having an average particle diameter of 80 nm or less as abrasive grains can be performed on the surface of the glass plate. It is preferable because it can be uniformly polished and a sufficient strength can be achieved.

Also, using a slurry containing known abrasive grains such as rare earth oxides such as cerium oxide, zirconium oxide, aluminum oxide, magnesium oxide, silicon oxide, silicon carbide, manganese oxide, iron oxide, diamond, boron nitride and zircon. It is more preferable to perform polishing using a slurry containing colloidal silica having an average particle size of 80 nm or less as abrasive grains after polishing.

Polishing both surfaces of the glass is preferable because warpage can be reduced by making the hydrogen concentration of the surface layer uniform on both surfaces of the glass.

(etching)
As an etching solution, an aqueous solution containing a glass-soluble chemical is used. An aqueous solution containing fluoride may be used for the glass-soluble chemical. Examples of the fluoride include hydrogen fluoride, ammonium fluoride, potassium fluoride, and sodium fluoride. These aqueous solutions may contain an inorganic acid and / or an organic acid. As the inorganic acid, one or more kinds may be selected from hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid and the like, and as the organic acid, one kind or two kinds or more may be selected from acetic acid, succinic acid and the like.

The etching rate is preferably 0.1 μm / cm ² / min or more, and more preferably 1 μm / cm ² / min or more. By setting the etching rate to 0.1 μm / cm ² / min or more, the time required for the etching process can be shortened, and tempered glass can be produced with higher efficiency. The etching rate can be adjusted by appropriately adjusting the composition of the glass used for chemical strengthening, the temperature or concentration of the etching solution, and the like.

The etching temperature is usually preferably 10 ° C. to 60 ° C., more preferably 20 ° C. to 40 ° C. Furthermore, the etching time is usually preferably from 30 seconds to 30 minutes, more preferably from 1 minute to 10 minutes. These etching conditions can be appropriately selected by those skilled in the art so that the reaction product does not precipitate depending on the material of the glass substrate used.

Etching on both surfaces of the glass is preferable because warpage can be reduced by making the hydrogen concentration of the surface layer uniform on both surfaces of the glass.

Since the deposits may adhere to the surface of the glass plate after etching, it is preferable to wash the glass plate after the treatment. The washing method is not particularly limited, and a known method can be used. For example, washing can be performed with an aqueous solution of sulfuric acid, hydrochloric acid, nitric acid, or the like while applying ultrasonic waves.

The method for producing tempered glass varies depending on the application, and is not particularly limited as other steps other than the hydrogen-containing layer removing step after the tempering step. An example is shown below, but the present invention is not limited to this example.

First, the prepared glass base plate is formed into a desired size and shape to be finally finished through processes such as cutting, drilling, notching, polishing, and thread chamfering. At this time, in order to improve the handling of the subsequent process and reduce the process cost, it is cut into a size larger than the desired size to be finally finished, and after all the processing steps are completed, the desired size is obtained. It may be formed into a shape.

The formed glass is tempered by chemical strengthening or physical strengthening, and then the hydrogen-containing layer is removed to form tempered glass. The tempered glass is subjected to, for example, printing, antireflection coating, functional film bonding, etc., and a cover glass is manufactured.

The tempered glass of the present invention can be used for a cover glass for a display such as a mobile phone, a digital camera or a touch panel display.

Hereinafter, an example in which the tempered glass of the present invention is used as a cover glass for a flat panel display device will be described. FIG. 3 is a cross-sectional view of a display device in which a cover glass is disposed. In the following description, front, rear, left and right are based on the direction of the arrow in the figure.

As shown in FIG. 3, the display device 10 generally includes a display panel 20 provided in the housing 15, and a cover glass 30 that covers the entire surface of the display panel 20 and surrounds the front of the housing 15. .

The cover glass 30 is installed mainly for the purpose of improving the aesthetics and strength of the display device 10 and preventing impact damage, and is formed of a single sheet of glass having a substantially flat shape as a whole. As shown in FIG. 3, the cover glass 30 may be installed so as to be separated from the display side (front side) of the display panel 20 (having an air layer), and has a translucent adhesive film (FIG. (Not shown) may be attached to the display side of the display panel 20.

A functional film 41 is provided on the front surface of the cover glass 30 that emits light from the display panel 20, and a functional film is provided on the back surface of the cover glass 30 on which light from the display panel 20 enters at a position corresponding to the display panel 20. 42 is provided. In addition, although the

functional films

41 and 42 are provided on both surfaces in FIG. 3, the

functional films

41 and 42 are not limited to this and may be provided on the front surface or the back surface, or may be omitted.

The

functional films

41 and 42 have functions such as anti-reflection of ambient light, prevention of impact breakage, electromagnetic wave shielding, near-infrared shielding, color tone correction, and / or scratch resistance improvement, and thickness and shape are used for applications. It is selected as appropriate. The

functional films

41 and 42 are formed, for example, by attaching a resin film to the cover glass 30. Or you may form by thin film formation methods, such as a vapor deposition method, a sputtering method, or CVD method.

Reference numeral 44 denotes a black layer, which is, for example, a coating formed by applying ink containing pigment particles to the cover glass 30, irradiating it with ultraviolet rays, or baking it, followed by cooling. As a result, the display panel or the like cannot be seen from the outside of the housing 15, and the appearance aesthetics are improved.

Examples of the present invention will be specifically described below, but the present invention is not limited to these.

[Manufacture of glass]
(Manufacture of glass plates)
A glass having the following composition was produced by a float method so as to have a plate thickness of 1.1 mm, and cut into 50 × 50 mm to produce a glass plate.
Composition: by mol%, a _{_{_{SiO 2 73%, Al 2 O}}} 3 to 7%, Na ₂ O 14%, the composition containing 6% MgO

In the following examples, the following steps were appropriately combined.

(Chemical strengthening)
The glass plate is immersed in KNO ₃ molten salt, subjected to ion exchange treatment, and then chemically strengthened by cooling to near room temperature. At this time, the temperature of the KNO ₃ molten salt was 435 ° C., and the immersion time was 4 hours. The obtained chemically strengthened glass was washed with water and subjected to the next step.

(Colloidal silica polishing)
As a polishing slurry, colloidal silica having an average particle diameter (d50) of 80 nm (Compoule 80; manufactured by Fujimi Incorporated) is dispersed in water to prepare a slurry, and a glass plate is polished at a polishing rate (single side). ): Polished with a polishing pad (Suede type H2093NX; manufactured by Fujibo Atago Co., Ltd.) at 0.03 μm / min.

[Evaluation methods]
(Secondary ion mass spectrometry)
The hydrogen concentration of the glass plate was analyzed by secondary ion mass spectrometry.

The analysis conditions for secondary ion mass spectrometry were as follows.
Measuring device: Secondary ion mass spectrometer having a quadrupole mass analyzer Primary ion species: Cs ⁺
Primary acceleration voltage: 5.0 kV
Primary ion current: 500 nA
Primary ion incident angle (angle from the direction perpendicular to the sample surface): 60 °
Raster size: 300 × 300 μm ²
Detection area: 12 × 12 μm ²
Secondary ion polarity: Use of electron gun for negative neutralization

In addition, it was set as 0 Field Aperture of a detector.

(Ball-on-ring test)
In the ball-on-ring (BOR) test, the glass plate 1 is placed using the pressure jig 2 (hardened steel, diameter 10 mm, mirror finish) made of SUS304 with the glass plate 1 placed horizontally. The pressure was applied and the strength of the glass plate 1 was measured. FIG. 1 is a schematic diagram for explaining the ball-on-ring test used in the present invention.

1, a glass plate 1 serving as a sample is horizontally installed on a receiving jig 3 made of SUS304 (diameter 30 mm, contact portion curvature R2.5 mm, contact portion is hardened steel, mirror finish). Above the glass plate 1, a pressurizing jig 2 for pressurizing the glass plate 1 is installed.

In this Embodiment, the center area | region of the glass plate 1 was pressurized from the upper direction of the glass plate 1 obtained after the Example and the comparative example. The test conditions are as follows.
Sample thickness: 1.1 (mm)
Lowering speed of the pressure jig 2: 1.0 (mm / min)
At this time, the breaking load (unit N) when the glass was broken was defined as BOR strength, and the average value of 20 measurements was defined as BOR average strength.

(Falling ball test)
FIG. 2 is a schematic diagram for explaining the falling ball test used in the present invention. In the falling ball test, the sphere 6 was dropped on the glass plate 5 and the strength of the glass plate 5 was evaluated. As a specific test method, first, the glass plate 5 was placed on a base 4 made of SUS304 (a vertical 100 × 100 × 10 mm thick metal plate having a 40 × 40 mm hollow portion in the center).

A sphere having a mass of 130 kg (made of SUS304, mirror finish) is dropped at the center of the glass plate 5 and the falling ball strength (J) is calculated from the height (destruction height) at which the sphere 6 is dropped when the glass is broken. Asked. The measurement was performed 20 times, and the average value of the falling ball strength was defined as the average falling ball strength.
Falling ball strength (J) = sphere mass (kg) × gravity acceleration (9.81 m / s ² ) × destruction height (m)

(Surface compressive stress value, compressive stress layer depth)
Surface compressive stress (Compressive Stress; hereinafter, CS, unit is MPa) and depth of compressive stress layer (Depth of Layer; hereinafter, DOL, unit is μm) are a surface stress meter manufactured by Orihara Seisakusho (FSM-6000). And measured.

[Example 1]
(1) A glass plate that has not been polished after chemical strengthening (hereinafter also referred to as an unpolished glass plate after strengthening), and a glass plate in which a region of 2 μm from the surface layer has been polished by colloidal silica polishing after chemical strengthening (hereinafter, after strengthening) The BOR strength in a polished glass plate) was measured. The result is shown in FIG.

In addition, as a result of measuring CS and DOL about each glass plate, it was 750 MPa and 45 μm for the unpolished glass plate after strengthening, and 680 MPa and 43 μm for the glass plate polished after strengthening.

As shown in FIG. 4 (a), the glass plate that has been polished after tempering has a significantly increased BOR strength compared with the glass plate that has not been polished after tempering, although CS is relatively decreased. I found out that

(2) The hydrogen profile in the glass surface layer was analyzed using the unstrengthened and polished glass plate prepared in (1) and the polished and polished glass plate. The result is shown in FIG.

As shown in FIG. 4B, it was found that the hydrogen profile in the glass surface layer of the glass plate polished after tempering was changed as compared with the unpolished glass plate after tempering.

[Example 2]
The relationship between the amount of polishing after strengthening and the strength of the glass plate was examined. FIG. 5A shows the correlation between the BOR strength measured by the ball-on-ring test and the amount of the glass plate polished after strengthening. FIG. 5B shows the correlation between the BD strength measured by the falling ball test and the amount of polishing the glass plate after strengthening.

As shown in FIGS. 5A and 5B, when the amount of polishing the glass plate after strengthening exceeded 2 μm, high BOR strength and BD strength were exhibited. When the hydrogen concentration of the glass plate was analyzed by secondary ion mass spectrometry, when 2 μm was polished from the surface layer of the tempered glass plate, the maximum hydrogen concentration in the region within 10 μm depth from the outermost surface of the compressive stress layer. Was 0.91, and the minimum hydrogen concentration at a depth of 10 μm from the outermost surface was 0.14. That is, the maximum hydrogen concentration in a region within 10 μm depth from the outermost surface of the compressive stress layer was 6.3 times the lowest hydrogen concentration at a depth of 10 μm from the outermost surface.

The maximum hydrogen concentration in a region within 10 μm depth from the outermost surface of the compressive stress layer was 0.13, and the lowest hydrogen concentration at a depth of 10 μm from the outermost surface was 0.11. That is, the maximum hydrogen concentration in the region within 10 μm depth from the outermost surface of the compressive stress layer was 1.2 times the lowest hydrogen concentration of 10 μm depth from the outermost surface. The hydrogen concentration is a value of [ ¹ H ⁻ / ³⁰ Si ⁻ ] measured under the above analysis conditions.

From this result, the maximum hydrogen concentration in the region within 10 μm depth from the outermost surface of the compressive stress layer in the tempered glass is not more than 5 times the minimum hydrogen concentration of 10 μm depth from the outermost surface. It turns out that it can improve.

[Example 3]
The correlation between the annealing temperature in the atmosphere and the BOR strength of the tempered polished glass was examined. FIG. 6A shows the result of measuring the BOR strength after polishing a chemically strengthened glass plate by 2 μm and annealing in air at each temperature for 4 hours.

As shown in FIG. 6 (a), even if the annealing temperature was lower than the temperature of chemical strengthening, the BOR strength of the tempered polished glass was lowered by annealing. The result of Fig.6 (a) shows that the BOR intensity | strength of tempered glass is dependent on annealing temperature.

Since the glass plate is polished and annealed after chemical strengthening, the hydrogen concentration on the glass surface is considered to be very low. From the result of FIG. 6A, it was found that the BOR strength of the tempered glass was lowered by annealing. The same phenomenon was observed for soda lime silicate glass.

In order to analyze this phenomenon, the physical state and chemical state of the glass surface were analyzed. As a result of analyzing the physical state with an atomic force microscope, there was no change in the roughness of Ra and the glass surface.

In addition, the chemical state of the glass surface was analyzed by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry. As a result of analysis by X-ray photoelectron spectroscopy, the composition of the glass surface was not changed except for ion exchange of K and Na. On the other hand, as a result of secondary ion mass spectrometry, it was found that hydrogen entered the glass surface after annealing. The result is shown in FIG.

FIG. 6B shows the result of analyzing the hydrogen concentration of the glass surface layer by secondary ion mass spectrometry when there is no annealing treatment and when annealing is performed at 350 ° C. for 4 hours. From the results shown in FIGS. 6 (a) and 6 (b), it was found that the strength of the glass was lowered by increasing the hydrogen concentration in the glass surface layer by heat treatment.

[Example 4]
In order to investigate the correlation between the hydrogen profile in the glass after the heat treatment and the strength of the glass, a glass in which the hydrogen concentration in the surface layer of the glass was changed by changing the heat treatment conditions was prepared, and the BOR strength of each glass was measured. . The result is shown in FIG.

From the results shown in FIG. 7, it is considered that hydrogen that has entered the surface layer of the glass generates chemical defects in the glass, and the chemical defects reduce the strength of the glass. As observed in atmospheric annealing, hydrogen was observed to penetrate the glass surface layer during the chemical strengthening process. From these results, it was found that the strength of the glass was improved by removing chemical defects generated in the chemical strengthening step by polishing after strengthening.

Also, a graph showing the correlation between the plate thickness and the BOR strength is shown in FIG. In FIG. 8, the ● plot shows a sample (Example) in which the maximum hydrogen concentration in the region within 10 μm depth from the outermost surface of the compressive stress layer is 5 times or less than the lowest hydrogen concentration of 10 μm depth from the outermost surface. BOR intensity is shown. The □ plot shows the BOR intensity of a sample (comparative example) in which the maximum hydrogen concentration in the region within 10 μm depth from the outermost surface of the compressive stress layer exceeds 5 times the minimum hydrogen concentration of 10 μm depth from the outermost surface. is there.

In FIG. 8, the conventional product has a BOR strength of □ plot. However, while the importance of the strength of the glass is further increased by thinning, it is considered that a glass having a BOR strength higher than this is preferable in the future. The solid line plot F = 1000 × t ² is the threshold value. Therefore, it was found that by setting F ≧ 1000 × t ² , the glass exhibits excellent BOR strength even when it is thinned.

A graph showing the correlation between the plate thickness and the falling ball strength is shown in FIG. In FIG. 9, the ● plot shows a sample (Example) in which the maximum hydrogen concentration in the region within 10 μm depth from the outermost surface of the compressive stress layer is 5 times or less than the minimum hydrogen concentration of 10 μm depth from the outermost surface. Indicates falling ball strength. A plot shows the falling ball strength of a sample (comparative example) in which the maximum hydrogen concentration in the region within 10 μm depth from the outermost surface of the compressive stress layer exceeds 5 times the lowest hydrogen concentration of 10 μm depth from the outermost surface.

The conventional product has a falling ball strength of □ plot. However, as the importance of the strength of the glass is further increased due to the thin plate, it is considered that the falling ball strength is more preferable in the future, and the solid line plot E = 1.0. × ^{t 2} is at its threshold. Therefore, it was found that by setting E ≧ 1.0 × t ² , the glass exhibits excellent falling ball strength even when it is thinned.

Table 1 summarizes the above results. In Table 1, the surface roughness Ra is a value measured with an atomic force microscope at a measurement size of 10 * 10 μm. σ _CS is the compressive stress value of the compressive stress layer, DOL is the compressive depth of the compressive stress layer, and is a value measured with a surface stress meter (FSM-6000 manufactured by Orihara Seisakusho).

In Table 1, the H content ratio is a ratio of the maximum hydrogen concentration in a region within 10 μm depth from the outermost surface of the compressive stress layer and the minimum hydrogen concentration of 10 μm depth from the outermost surface.

In Table 1, “B” indicates that the BOR strength F (N) ≧ 1000 × t ² is satisfied, and “X” indicates that the BOR intensity F (N) ≧ 1000 × t ² is not satisfied. In addition, when the falling ball strength E (J) ≧ 1.0 × t ² is satisfied, “◯” is indicated, and when it is not satisfied, “×” is indicated.

As shown in Table 1, all of the tempered glasses of Examples 1 to 5 having an H content ratio of 5 or less have BOR strength F (N) ≧ 1000 × t ² and falling ball strength E (J) ≧ 1.0 × t. ² and excellent strength, the tempered glass of the comparative example, which is a conventional product, has a BOR strength F (N) ≧ 1000 × t ² and a falling ball strength E (J) ≧ 1.0 × t. It was found that ² was not satisfied.

Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit and scope of the invention. This application is based on a Japanese patent application filed on November 30, 2012 (Japanese Patent Application No. 2012-263058), which is incorporated by reference in its entirety.

1, 5 Glass plate 2 Pressure jig 3 Receiving jig 4 Base 6 Sphere 10 Display device 15 Housing 20 Display panel 30 Cover glass

Claims

The surface layer has a compressive stress layer, and the maximum hydrogen concentration in a region within 10 μm depth from the outermost surface of the compressive stress layer is not more than 5 times the minimum hydrogen concentration of 10 μm depth from the outermost surface. Tempered glass.
The maximum hydrogen concentration in the region within 10 μm depth from the outermost surface of the compressive stress layer and the lowest hydrogen concentration of 10 μm depth from the outermost surface are values measured under the following analytical conditions.
(Analysis conditions)
Measuring device: Secondary ion mass spectrometer having a quadrupole mass analyzer Primary ion species: Cs +
Primary acceleration voltage: 5.0 kV
Primary ion current: 500 nA
Primary ion incident angle (angle from the direction perpendicular to the sample surface): 60 °
Raster size: 300 × 300 μm 2
Detection area: 12 × 12 μm 2
Secondary ion polarity: Use of electron gun for negative neutralization
The tempered glass according to claim 1, wherein the compressive stress layer is formed by an ion exchange method.
The tempered glass according to claim 1 or 2, wherein the compressive stress value of the compressive stress layer is 400 MPa or more.
The tempered glass according to any one of claims 1 to 3, comprising alkali aluminosilicate glass or soda lime glass.
The glass plate is placed on a ring made of stainless steel having a diameter of 30 mm and the contact portion is rounded with a radius of curvature of 2.5 mm, and the sphere is statically fixed in a state where the glass plate is in contact with a sphere made of steel having a diameter of 10 mm. The tempered glass according to any one of claims 1 to 4, wherein the BOR strength F (N) measured by a ball-on-ring test applied to the center of the ring under a load condition satisfies the following formula.
F ≧ 1000 × t 2
[Wherein, F is the BOR strength (N) measured by the ball-on-ring test, and t is the thickness (mm) of the glass plate. ]
In a falling ball test in which a glass plate is placed on a stainless steel base and a sphere made of stainless steel having a diameter of 10 mm is dropped from above, the falling ball strength E (J) calculated by the following formula is E ≧ 1.0 × t 2. The tempered glass according to any one of claims 1 to 5, which satisfies:
Falling ball strength E (J) = sphere mass (kg) × gravity acceleration (9.81 m / s 2 ) × destruction height (m)
[Where E is the falling ball strength (J) measured by the falling ball test, and t is the thickness (mm) of the glass plate. ]
A molten salt containing KNO 3 is brought into contact with glass to form a compressive stress layer on the glass surface, and then the maximum hydrogen concentration in the region within 10 μm depth from the outermost surface of the compressive stress layer has a depth from the outermost surface. A method for producing a tempered glass, comprising removing a hydrogen-containing layer exceeding 5 times the minimum hydrogen concentration of 10 μm.
The hydrogen concentration in a region within 10 μm depth from the outermost surface of the compressive stress layer and the lowest hydrogen concentration at a depth of 10 μm from the outermost surface are values measured under the following analytical conditions.
(Analysis conditions)
Measuring device: Secondary ion mass spectrometer having a quadrupole mass analyzer Primary ion species: Cs +
Primary acceleration voltage: 5.0 kV
Primary ion current: 500 nA
Primary ion incident angle (angle from the direction perpendicular to the sample surface): 60 °
Raster size: 300 × 300 μm 2
Detection area: 12 × 12 μm 2
Secondary ion polarity: Use of electron gun for negative neutralization
The method for producing a tempered glass according to claim 7, wherein the removal of the hydrogen-containing layer is performed by polishing or etching.