WO2015137285A1 - Glass for chemical strengthening, and chemically strengthened glass - Google Patents

Abstract

　Provided are a glass for chemical strengthening and a chemically strengthened glass, provided with characteristics suitable for application in a housing or decorative component of an electronic device, i.e., excellent aesthetics, high productivity, and high strength. This glass for chemical strengthening is characterized by containing 0.1-7% Fe₂O₃, 1-25% Al₂O₃, and 0.1-10% B₂O₃ by mole percentage in terms of oxides, the minimum absorbance in a wavelength range of 380 nm to 780 nm being at least 0.3, the indentation load of a Vickers indenter giving a crack incidence of 50% when an indentation is formed using the Vickers indenter (angle of tip: 136°) in a mirror-finished surface of a sheet of the glass having a thickness of 0.8 mm being at least 150 gf, and the glass for chemical strengthening not containing magnetite crystals.

Description

Chemically strengthened glass and chemically strengthened glass

The present invention relates to a chemically tempered glass and a chemically tempered glass used for electronic devices, for example, casings and ornaments of communication devices and information devices that can be carried and used.

Cases and decorations for electronic devices such as mobile phones are selected and used from materials such as resin and metal in consideration of various factors such as decorativeness, scratch resistance, workability, and cost. Yes.

In recent years, attempts have been made to use glass, which has not been used in the past, as a casing material (see Patent Document 1). According to Patent Document 1, in an electronic device such as a mobile phone, it is said that a unique decoration effect with a sense of transparency can be exhibited by forming the casing body from glass.

筐 体 Cases and decorations of electronic devices that can be carried around, such as mobile phones, are required to have high strength in consideration of damage due to drop impact during use and contact damage due to long-term use.

As a method for increasing the strength of glass, a method of forming a compressive stress layer on the glass surface is generally known.
As a method for forming a compressive stress layer on the glass surface, an air cooling strengthening method (physical strengthening method) in which the glass plate surface heated to near the softening point is rapidly cooled by air cooling or the like, and ions at a temperature below the glass transition point. Alkali metal ions (typically Li ions and Na ions) having a small ionic radius on the glass plate surface by exchange are alkali ions (typically Na ions or K ions for Li ions). A typical chemical strengthening method is to exchange K ions for Na ions.

For example, the decorative glass as described above is usually used with a thickness of 2 mm or less. When the air cooling strengthening method is applied to such a thin glass plate, it is difficult to form a compressive stress layer because the temperature difference between the surface and the inside is difficult to be obtained, and the desired high strength characteristic can be obtained. Can not. Further, in the air cooling enhancement, due to the variation in cooling temperature, there is a great concern that the flatness may be impaired particularly for a thin plate, and the texture that is the object of the present invention may be impaired. From these points, it is preferable that the latter can be strengthened by the chemical strengthening method.

Also, the case and decoration of electronic devices such as mobile phones are often used in black, which does not insist on the existence of the device itself, yet provides a profound feeling and luxury.

The glass described in Patent Document 2 is known as a glass that can be chemically strengthened and has a black color. The glass described in Patent Document 2 is an aluminosilicate glass containing a high concentration of iron oxide.

JP 2009-61730 A Japanese Examined Patent Publication No. 45-16112

When glass is strengthened using a chemical strengthening method, it is known that the surface compressive stress of the compressive stress layer is improved by containing an aluminum component in the glass.
Moreover, the melting temperature of a glass raw material becomes high by containing an aluminum component in glass. Therefore, it is also known that the melting temperature of the glass raw material is kept below a certain level by containing a boron component in the glass.

However, the present inventor, for the purpose of creating a glass exhibiting a black color with high absorbance, when an iron component is contained in the glass and the above-described aluminum component and boron component are co-added, the aluminum component and the iron component It was confirmed that devitrification occurred in the melted glass in the specific content range.

When the glass exhibiting black color is devitrified in the glass, there is a problem that the surface of the glass is thin and cloudy and the appearance is not excellent. Since devitrification in the glass occurs not only on the surface of the glass but also on the inside, even if the surface of the glass is polished, this problem cannot be solved.

Further, when devitrification occurs in the glass, there is a problem that the polishing process takes time because a crystal phase having higher hardness than the glass phase exists in the glass. In addition, due to the presence of a crystalline phase having high hardness in the glass, chipping and cracking are likely to occur on the end face of the glass in the polishing step, and the bending strength of the glass may be reduced.

The object of the present invention is to provide chemically tempered glass and chemically tempered glass having characteristics suitable for use in electronic device casings and decorative products, that is, excellent aesthetics, high productivity, and high strength.

The present invention, in a molar percentage based on the following oxides, _{Fe 2 O 3 0.1 ~ 7%} , the _{Al 2 O 3 1 ~ 25%} , the B 2 _{O 3} containing 0.1 to 10 percent, Vickers indenter having a minimum value of absorbance at a wavelength of 380 nm to 780 nm of 0.3 or more and a mirror finished surface of a glass plate having a thickness of 0.8 mm having an angle of 136 ° (hereinafter referred to as “in this specification”) This “Vickers indenter having a tip angle of 136 °” is referred to as “Vickers indenter (tip portion angle is 136 °)”.) When a dent is formed using a Vickers indenter, the crack occurrence rate is 50%. The intensifying load is 150 gf (1.471 N) or more, and a glass for chemical strengthening that does not contain magnetite crystals (hereinafter referred to as the chemically strengthened glass of the present invention) is provided.

Further, when the glass for chemical strengthening of the present invention contains 2 to 7% of Fe ₂ O ₃ , Al ₂ O ₃ is X%, and Fe ₂ O ₃ is Y%, the following formula (1) A chemically strengthened glass containing the indicated amount is provided.
Y ≦ −0.518X + 8.924 (1)
Also provided is a glass for chemical strengthening according to the present invention, which contains 0.1 to 5% of V ₂ O ₅ .

Further, the glass for chemical strengthening according to the present invention is SiO ₂ 55 to 75%, Al ₂ O ₃ 1 to 25%, B ₂ O ₃ 0.1 to 10%, Na ₂ O 10-20%, K ₂ O 0-5%, MgO 0-10%, CaO 0-10%, ΣRO (R is Mg, Ca, Sr, Ba, and Zn) Represents an alkaline earth metal selected from the group consisting of: RO represents one or more oxides of the alkaline earth metal, and ΣRO represents the total content of RO contained). 18%, 0.1 to 7% of Fe ₂ O ₃ and 0 to at least one metal oxide selected from the group consisting of coloring components (Co, Mn, Ni, Cu, Cr, V, and Bi) Provide a glass for chemical strengthening containing ˜7%.

Further, the present invention is a chemically strengthened glass obtained by chemically strengthening the above-described glass for chemical strengthening according to the present invention, which is provided with a compressive stress layer on the surface and is a glass plate having a thickness of 0.8 mm. Provided is a chemically strengthened glass having a Vickers indentation load of 7 kgf (68.65 N) or more that gives a fracture rate of 50% when a Vickers indenter (angle of the tip portion is 136 °) is implanted on the surface.

Also provided is a chemically strengthened glass of the present invention, wherein the depth of the compressive stress layer is 10 μm or more, and the surface compressive stress of the compressive stress layer is 300 MPa or more.

According to the present invention, it is possible to obtain a chemically strengthened glass and a chemically strengthened glass exhibiting a black color with characteristics suitable for use in electronic device casings and decorative products, that is, an excellent aesthetic appearance. Moreover, the glass for chemical strengthening and the chemically strengthened glass of the present invention can be a glass having high productivity and high strength.

It is the figure which plotted the presence or absence of devitrification in each glass of an Example and a comparative example by content of an iron component and an aluminum component.

The glass for chemical strengthening of the present invention is expressed in terms of a mole percentage based on the following oxides: Fe ₂ O ₃ is 0.1 to 7%, Al ₂ O ₃ is 1 to 25%, B ₂ O ₃ is 0.1 to Contains 10%.
In addition, in this specification, content, such as a coloring component, shows conversion content when each component which exists in glass shall exist as a displayed oxide. For example, “contains 0.1 to 7% of Fe ₂ O ₃ ” means that the Fe content in the glass is all in the form of Fe ₂ O ₃ , that is, Fe This means that the content in terms of Fe ₂ O ₃ is 0.1 to 7%.
In the present specification, “to” indicating a numerical range is used in the sense of including the numerical values described before and after it as a lower limit and an upper limit, and unless otherwise specified, Are used with similar meanings.

Fe ₂ O ₃ is a component for shielding light having a wavelength in the visible range and presenting the glass black, and is essential. If it is less than 0.1%, the glass does not exhibit black color. If Fe ₂ O ₃ exceeds 7%, the glass becomes unstable and devitrification may occur.
The ratio of the content of divalent iron in terms of Fe ₂ O ₃ in the total iron (that is, iron redox) is preferably 10 to 50%, particularly preferably 15 to 40%. Most preferably, it is 20 to 30%. If the iron redox is lower than 10%, when SO ₃ is contained, the decomposition does not proceed and the expected clarification effect may not be obtained. If it is higher than 50%, SO ₃ will be decomposed too much before clarification and the expected clarification effect may not be obtained, or the number of bubbles may increase due to generation of bubbles.

Iron redox may indicate the percentage of divalent iron in terms of Mossbauer Spectroscopy Fe ₂ O ₃ in the total iron in terms of Fe ₂ O ₃ by% on the display. Specifically, a radiation source ( ⁵⁷ Co), a glass sample (a 3-7 mm thick glass flat plate cut, ground, and mirror-polished from the glass block) and a detector (LND 45431) are arranged on a straight line. Perform optical system evaluation. The radiation source is moved with respect to the axial direction of the optical system, and the energy change of γ rays is caused by the Doppler effect. Then, using the Mossbauer absorption spectrum obtained at room temperature, the ratio of divalent Fe to trivalent Fe is calculated, and the ratio of divalent Fe is defined as iron redox.

Al ₂ O ₃ is a component that improves the chemical strengthening properties of glass and is essential. If it is less than 1%, the chemical strengthening properties are not sufficient. If Al ₂ O ₃ exceeds 25%, the viscosity of the glass becomes high and uniform melting becomes difficult.

B ₂ O ₃ is a component that lowers the melting temperature of the glass raw material and is essential. When B ₂ O ₃ is contained, if it is less than 0.1%, the effect of lowering the melting temperature of the glass raw material may not be obtained. If B ₂ O ₃ exceeds 10%, striae due to volatilization may occur and the yield may decrease.

The glass for chemical strengthening of the present invention has a minimum absorbance of 0.3 or more at a wavelength of 380 nm to 780 nm.
The glass for chemical strengthening is packaged, for example, on an electronic device. On the outer surface of the mobile phone, a display device made up of a liquid crystal panel or organic EL and an operation device made up of buttons, or an operation device made up of a display device such as a touch panel and an operation device are arranged on one side. The frame material is enclosed. The other surface on the opposite side is constituted by a panel. And there exists a frame material in the thickness part of the apparatus between one surface and the other surface. The frame material and the frame material, or the panel and the frame material may be configured integrally.

The glass for chemical strengthening can be used for any of the above-mentioned frame materials, panels, and frame materials. Moreover, the glass for chemical strengthening may be flat, concave, or convex.

A light source of a display device provided in an electronic device is configured to emit white light such as a light emitting diode, an organic EL, or a CCFL. Therefore, the minimum value of the absorbance at a wavelength of 380 nm to 780 nm of the chemically strengthened glass needs to be 0.3 or more so that the white light does not leak outside the device through the chemically strengthened glass. White light is made to be recognized as white after phosphors are used and light having a plurality of wavelengths in the visible range is combined. Therefore, by setting the minimum value of the absorbance at a wavelength in the visible range to 0.3 or more, it is possible to absorb white light with a single glass without providing a light shielding unit and obtain sufficient light shielding properties.

If the minimum absorbance at a wavelength of 380 nm to 780 nm of the glass is less than 0.3, a desired light shielding property cannot be obtained, and visible light may pass through the chemically strengthening glass. In addition, when the chemically strengthened glass is formed into a concave shape or a convex shape, visible light may pass through a portion where the thickness is the thinnest. When the thickness of the glass for chemical strengthening is thin, it is necessary to make the minimum value of the absorbance at the thin portion 0.3 or more, and the absorbance is preferably 0.7 or more, more preferably 0.9 or more, 1.0 or more is particularly preferable.

The method for calculating absorbance in the present invention is as follows. Both surfaces of the glass plate are mirror-polished and the thickness t is measured. The spectral transmittance T of this glass plate is measured (for example, using a UV-visible near-infrared spectrophotometer V-570 manufactured by JASCO Corporation). Then, the absorbance A is calculated using a relational expression of A = −log ₁₀ T.

The glass for chemical strengthening of the present invention is a glass plate having a thickness of 0.8 mm, but the crack occurrence rate when indentation is formed on the mirror-finished surface using a Vickers indenter (the angle of the tip is 136 °) is 50%. The indentation load of the Vickers indenter (hereinafter sometimes referred to as CIL) is 150 gf or more.
If this indentation load is less than 150 gf, it means that the surface of the glass is easily damaged, and the scratches remaining on the glass surface during polishing and the like become deep. Therefore, a chemically strengthened glass having high strength after chemically strengthening the chemically strengthened glass cannot be obtained.

The indentation load was determined by the following method. A plate-like glass having a thickness of 0.8 mm and having both surfaces mirror-polished was prepared. Using a Vickers hardness tester, a Vickers indenter (the tip angle was 136 °) was pressed for 15 seconds, then the Vickers indenter was removed, and the vicinity of the indentation was observed after 15 seconds. In the observation, we investigated how many cracks occurred from the corner of the indentation. The measurement was performed by pushing the Vickers indenter of 50 gf (0.49 N), 100 gf (0.981 N), 200 gf (1.961 N), 300 gf (2.941 N), 500 gf (4.903 N), 1 kgf (9.807 N). Separately, it was performed on 10 sheets of glass. The average number of cracks generated was calculated for each load. The relationship between the load and the number of cracks was calculated by regression using a sigmoid function. From the regression calculation result, the load at which the number of cracks was two was defined as the indentation load value (gf). The atmospheric conditions for the measurement are an air temperature of 25 ° C. and a humidity of about 40%.

It is essential that the chemically strengthening glass of the present invention does not contain magnetite crystals.
As described above, when devitrification occurs in the glass, a polishing phase takes time because a crystal phase having a higher hardness than the glass phase is present in the glass. In addition, due to the presence of a crystalline phase having high hardness in the glass, chipping and cracking are likely to occur on the end face of the glass in the polishing step, and the bending strength of the glass may be reduced.

The present inventor has found that there is a content range in which devitrification does not occur between the iron component and the aluminum component when melting the glass for chemical strengthening, which essentially includes the iron component, the boron component, and the aluminum component. Magnetite crystals are a kind of oxide mineral and crystallize when the iron component contained in the glass raw material is devitrified in the process of melting to slow cooling. The chemical composition is represented by Fe ²⁺ Fe ³⁺ ₂ O ₄ (triiron tetroxide).

In the present invention, the magnetite crystal in the glass is judged to be contained when the linear transmittance at a wavelength of 800 nm of the glass having a thickness of 0.8 mm is 1% or less. This is because, when magnetite crystals are present in the glass, light transmitted through the glass is scattered by the crystals, and the value of the linear transmittance is thereby significantly reduced. As another method, the presence or absence of magnetite crystals in the glass can be confirmed by a method in which the surface of the glass is polished and observed using an optical microscope.

The chemically strengthened glass of the present invention has two preferred embodiments (first and second embodiments) described below.

The glass for chemical strengthening according to the first embodiment will be described.
The composition of the glass for chemical strengthening according to the first embodiment of the present invention will be described using the mole percentage display content unless otherwise specified.

Fe ₂ O ₃ is an essential component for presenting the glass in black, and the total iron content represented by Fe ₂ O ₃ is 2% or more and 7% or less. If the total iron content is less than 2%, the desired black glass cannot be obtained. Preferably it is 2.5% or more, More preferably, it is 3% or more. If Fe ₂ O ₃ exceeds 7%, a desired black color tone cannot be obtained. Preferably it is 6% or less, More preferably, it is 5% or less.

Al ₂ O ₃ is a component that improves the weather resistance and chemical strengthening properties of glass and is essential. However, when 2 to 7% of Fe ₂ O ₃ is contained, devitrification may occur in the molten glass in a specific content range of the aluminum component and the iron component. Therefore, the _Al 2 _{O 3} contained in the glass X%, if the _Fe 2 _{O 3} was set to Y%, as the _Al 2 _{O 3,} contains an amount indicated by the following equation (1).
Y ≦ −0.518X + 8.924 (1)
With a range of _Al 2 _{O 3} and _Fe 2 _{O 3} shown in Equation (1), it is possible to prevent the devitrification occurs in the glass. On the other hand, if it is out of the above range, devitrification may occur in the glass. The formula (1) is obtained by the present inventor by creating a number of glasses having different content ratios of the iron component and the aluminum component and confirming whether or not devitrification occurs.

The glass for chemical strengthening of the second embodiment will be described.
The composition of the glass for chemical strengthening of the following second embodiment of the present invention will be described using the mole percentage display content unless otherwise specified.

Fe ₂ O ₃ is an essential component for presenting the glass in a relatively thin black color, and the total iron content represented by Fe ₂ O ₃ is 0.1 to less than 2%. If the total iron content is less than 0.1%, a desired black glass cannot be obtained. Preferably it is 0.2% or more, More preferably, it is 0.5% or more. If Fe ₂ O ₃ is 2% or more, the strength of the glass may be lowered. Preferably it is 1.8% or less, More preferably, it is 1.5% or less.

Next, other glass components common to the glass for chemical strengthening of the first and second embodiments will be described using the mole percentage display content unless otherwise specified.

SiO ₂ is a component constituting the glass skeleton and essential, and the content of SiO ₂ is 55 to 75%. If it is less than 55%, the stability as glass will deteriorate, or the weather resistance will deteriorate. Preferably it is 60% or more. More preferably, it is 65% or more.
If the SiO ₂ content exceeds 75%, the viscosity of the glass increases and the meltability decreases significantly. Preferably it is 73% or less, typically 72% or less.

Na ₂ O is a component that improves the meltability of glass, and is essential because a surface compressive stress layer is formed by ion exchange. The content of Na ₂ O is 10 to 20%. If it is less than 10%, the meltability is poor, and it becomes difficult to form a desired surface compressive stress layer by ion exchange. Preferably it is 11% or more, typically 12% or more.
When Na ₂ O exceeds 20%, the weather resistance decreases. Preferably it is 18% or less, typically 16% or less.

K ₂ O is a component that improves the meltability and has the effect of increasing the ion exchange rate in chemical strengthening, and is therefore not essential, but is a preferable component. When K ₂ O is contained, the content of K ₂ O is preferably 0.01 to 5%. If it is less than 0.01%, there is a possibility that a significant effect cannot be obtained for improving the meltability, or a significant effect cannot be obtained for improving the ion exchange rate. Typically, it is 0.3% or more.
When K ₂ O exceeds 5%, the weather resistance decreases. Preferably it is 4% or less, typically 3% or less.

MgO is a component that improves the meltability, and is not essential, but can be contained as necessary. When MgO is contained, the content of MgO is preferably 3 to 10%. If it is less than 3%, there is a possibility that a significant effect for improving the meltability cannot be obtained. Typically 4% or more.
When MgO exceeds 10%, the weather resistance decreases. Preferably it is 9% or less, typically 8% or less.

CaO is a component that improves the meltability, and can be contained as necessary. When CaO is contained, the content of CaO is preferably 0.01 to 10%. If it is less than 0.01%, a significant effect on improving the meltability cannot be obtained. Typically, it is 0.1% or more.
If CaO exceeds 10%, the chemical strengthening properties are lowered. Preferably it is 9% or less, typically 8% or less.

RO (R is an alkaline earth metal selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, and RO is a component of the alkaline earth metal oxide) improves the meltability. Although it is a component and is not essential, it can contain any 1 or more types as needed.
The total ΣRO content of RO when RO is contained is preferably 1 to 18%. If it is less than 1%, the meltability may decrease. Preferably it is 3% or more, typically 5% or more.
When ΣRO exceeds 18%, the weather resistance decreases. It is preferably 15% or less, more preferably 13% or less, and typically 11% or less. Note that ΣRO indicates the total amount of all RO components.

ZrO ₂ is a component that increases the ion exchange rate and is not essential, but may be contained in a range of less than 1%. If the ZrO ₂ content exceeds 1%, the meltability may be deteriorated and remain in the glass as an unmelted product.

SO ₃ is a component that acts as a fining agent, and is not essential, but can be contained as necessary. When SO ₃ is contained, the content of SO ₃ is preferably 0.005 to 0.3%. If it is less than 0.005%, the expected clarification action cannot be obtained. Preferably it is 0.01% or more, More preferably, it is 0.02% or more. 0.03% or more is most preferable. On the other hand, if it exceeds 0.5%, it becomes a generation source of bubbles, and there is a possibility that the glass melts slowly or the number of bubbles increases. Preferably it is 0.3% or less, More preferably, it is 0.2% or less. 0.1% or less is most preferable.

SnO ₂ is a component that acts as a fining agent, and is not essential, but can be contained as necessary. When SnO ₂ is contained, the content of SnO ₂ is preferably 0.005 to 1%. If it is less than 0.005%, the expected clarification action cannot be obtained. Preferably it is 0.01% or more, More preferably, it is 0.05% or more. On the other hand, if it exceeds 1%, it becomes a generation source of bubbles, and there is a possibility that the glass melts slowly or the number of bubbles increases. Preferably it is 0.8% or less, More preferably, it is 0.5% or less. Most preferred is 0.3% or less.

Li ₂ O is a component for improving the meltability, and is not essential, but can be contained as necessary. When Li ₂ O is contained, the content of Li ₂ O is preferably 1 to 15%. If it is less than 1%, there is a possibility that a significant effect for improving the meltability cannot be obtained. Preferably it is 3% or more, and typically 6% or more.
If Li ₂ O exceeds 15%, the weather resistance may decrease. Preferably it is 10% or less, typically 5% or less.

SrO is a component for improving the meltability, and is not essential, but can be contained as necessary. When SrO is contained, the content of SrO is preferably 1 to 15%. If it is less than 1%, there is a possibility that a significant effect for improving the meltability cannot be obtained. Preferably it is 3% or more, and typically 6% or more.
If SrO exceeds 15%, the weather resistance and chemical strengthening properties may be lowered. Preferably it is 12% or less, typically 9% or less.

BaO is a component for improving the meltability, and is not essential, but can be contained as necessary. When BaO is contained, the content of BaO is preferably 1 to 15%. If it is less than 1%, there is a possibility that a significant effect for improving the meltability cannot be obtained. Preferably it is 3% or more, and typically 6% or more.
If BaO exceeds 15%, the weather resistance and chemical strengthening properties may be reduced. Preferably it is 12% or less, typically 9% or less.

ZnO is a component for improving the meltability, and is not essential, but can be contained as necessary. When ZnO is contained, the content of ZnO is preferably 1 to 15%. If it is less than 1%, there is a possibility that a significant effect for improving the meltability cannot be obtained. Preferably it is 3% or more, and typically 6% or more.
If ZnO exceeds 15%, the weather resistance may be lowered. Preferably it is 12% or less, typically 9% or less.

The glass coloring component may contain at least one component of a metal oxide selected from the group of metals consisting of Co, Mn, Ni, Cu, Cr, V, and Bi. When such components are contained, the total content of these components is preferably 7% or less, and typically 6% or less.

Among the above-mentioned coloring components, V ₂ O ₅ is a component that improves CIL and can be contained as necessary, although not essential. When V ₂ O ₅ is contained, the content of V ₂ O ₅ is preferably 0.1 to 5%. If it is less than 0.1%, there is a possibility that a significant effect for improving CIL cannot be obtained. Preferably it is 0.2% or more, and typically 0.5% or more.
If V ₂ O ₅ exceeds 5%, the weather resistance may decrease. Preferably it is 4% or less, typically 3% or less.

The glass for chemical strengthening of the present invention may be chemically strengthened to form a compressive stress layer on the glass surface.
The method of chemical strengthening treatment is not particularly limited as long as it can ion-exchange Na ₂ O on the glass surface layer and K ₂ O in the molten salt. For example, a method of dipping the glass like a heated potassium nitrate (KNO ₃₎ molten salt. The conditions for forming a chemically strengthened layer (surface compressive stress layer) having a desired surface compressive stress on the glass surface vary depending on the thickness of the glass, but the glass is added to the KNO ₃ molten salt at 400 to 550 ° C. It is typical to soak for 2 to 20 hours.
Further, as this KNO ₃ molten salt, in addition to KNO ₃ , for example, NaNO ₃ may be contained in an amount of about 5% or less.

The chemically strengthened glass of the present invention can be produced by applying the chemical strengthening method described above. At this time, the depth of the compressive stress layer generated by the chemical strengthening treatment is preferably 10 μm or more. The reason is as follows.

In the production of glass used for decorative purposes, the glass surface may be polished, and the grain size of the abrasive grains used for polishing at the final stage is typically 2 to 6 μm. Such abrasive grains are thought to ultimately form microcracks having a maximum size of 5 μm on the glass surface. In order to make the strength improvement effect by the chemical strengthening treatment effective, it is necessary to form a compressive stress layer deeper than the microcracks formed on the glass surface. For this reason, it is preferable that the depth of the compressive-stress layer produced by a chemical strengthening process shall be 10 micrometers or more. Moreover, since the damage exceeding the depth of a compressive-stress layer at the time of use will lead to destruction of glass, the one where the compressive-stress layer is thick is preferable. For this reason, the compressive stress layer is more preferably 12 μm or more, further preferably 14 μm or more, and typically 16 μm or more.

On the other hand, if the compressive stress layer is too deep, the internal tensile stress increases and the impact at the time of failure increases. That is, it is known that when the internal tensile stress is large, the glass tends to become a fine piece and scatter in pieces at the time of breakage, which increases the risk. As a result of experiments by the present inventors, it has been found that in a glass having a thickness of 2 mm or less, scattering at the time of breakage becomes significant when the depth of the surface compressive stress layer exceeds 70 μm. Therefore, in the chemically strengthened glass of the present invention, the depth of the compressive stress layer is 70 μm or less. When used as a decorative glass, depending on the application, for example, a portable device having a higher probability of contact scratches on the surface than an operation panel of a mounting type device such as an AV device / OA device. When applying to the above, it is conceivable to reduce the depth of the compressive stress layer for safety. In this case, the depth of the compressive stress layer is more preferably 60 μm or less, further preferably 50 μm or less, and typically 40 μm or less.

Further, as described above, the chemically strengthened glass of the present invention can be obtained by chemically strengthening the glass by chemically strengthening, but the surface compressive stress of the compressive stress layer formed on the glass surface is 300 MPa or more. Preferably, it is 550 MPa or more, more preferably 700 MPa or more. Further, the surface compressive stress of the surface compressive stress layer is preferably 1400 MPa or less, and more preferably 1300 MPa or less. Typically, it is 1200 MPa or less.

In addition, the chemically strengthened glass of the present invention is a glass plate having a thickness of 0.8 mm, and a Vickers indenter having a fracture rate of 50% when a Vickers indenter (the angle of the tip portion is 136 °) is driven into the mirror-finished surface The driving load (hereinafter sometimes referred to as FIL) is preferably 7 kgf (68.65 N) or more. By doing in this way, the glass strong against a bending and an abrasion can be obtained. When the driving load of the Vickers indenter at which the fracture rate is 50% is less than 7 kgf (68.65 N), the strength of the glass is insufficient, and the chemical strengthening effect may not be sufficiently exhibited. Preferably, it is 8 kgf (78.45 N) or more, more preferably 10 kgf (98.07 N) or more.

The driving load was obtained by the following method. A plate-shaped chemically tempered glass having a thickness of 0.8 mm prepared by mirror-polishing both surfaces of a glass plate having a thickness of 0.8 mm and performing chemical strengthening treatment was prepared. With a Vickers hardness tester, the presence or absence of glass breakage was observed when a Vickers indenter (the angle of the tip portion was 136 °) was driven. The measurement is performed by a Vickers indentation load of 5 kgf (49.03 N), 10 kgf (98.07 N), 20 kgf (196.13 N), 30 kgf (294.20 N), 40 kgf (392.27 N), and 50 kgf (490.33 N). Separately, it was performed on 10 sheets of glass. The glass breaking rate was calculated for each load. In a region including a load where the fracture rate is 50%, the relationship between the load and the fracture rate was calculated by regression using a linear function. From the regression calculation results, the load at which the fracture rate was 50% was determined as the driving load value (kgf). The atmospheric conditions for the measurement are an air temperature of 25 ° C. and a humidity of about 40%.

The method for producing the glass for chemical strengthening of the present invention is not particularly limited. For example, various raw materials are prepared so as to have a desired glass composition, heated to 1500 to 1700 ° C. and melted, and then defoamed and stirred. Homogenized and formed into a plate shape or the like by a well-known down draw method, press method, float method or the like, or cast into a block shape. And after slow cooling, it cut | disconnects to desired size, and gives a polishing process as needed, and is manufactured.

As described above, the chemical strengthening glass of the present invention has been described by way of an example, but the configuration can be appropriately changed as necessary without departing from the spirit of the present invention.

Hereinafter, although it demonstrates in detail based on the Example of this invention, this invention is not limited only to these Examples.

For Examples 1 to 49 in Table 1 to Table 5 (Examples 1 to 33 are Examples, and Examples 34 to 49 are Comparative Examples), oxides, Commonly used glass materials such as products, carbonates and nitrates were appropriately selected and weighed to 100 ml as glass. Note that the SO ₃ in Table, was added to bow the glass raw material nitric _(Na 2 SO _4), a residual SO ₃ remaining in glass after Glauber's salt decomposition, is a calculated value.

Next, this raw material mixture was put into a platinum crucible, put into a resistance heating type electric furnace at 1500 to 1600 ° C., heated for about 0.5 hours, and then the raw materials were melted, and then melted for 1 hour and degassed. Then, it was poured into a mold having a length of about 50 mm × width of about 100 mm × height of about 20 mm preheated to about 300 ° C., and slowly cooled at a rate of about 1 ° C./min to obtain a glass block. After cutting this glass block, the glass is cut out so that the size is 40 mm long x 40 mm wide x 0.8 mm thick, then ground, and finally polished on both sides to a mirror surface to obtain a plate-like glass It was.

About the obtained plate-like glass, the crack occurrence rate when forming an indentation using a Vickers indenter (angle of the tip portion is 136 °) on the mirror-finished surface of a glass plate having a thickness of 0.8 mm is 50%. The indentation load (CIL) of the Vickers indenter, and the fracture rate when the Vickers indenter (the tip angle is 136 °) is driven into the mirror-finished surface of the glass plate having a thickness of 0.8 mm that has been chemically strengthened. Vickers indentation load (FIL) of 50%, minimum and maximum values of linear transmittance at wavelengths of 300 nm to 800 nm and wavelengths of 380 nm to 780 nm, and minimum and maximum values of absorbance at wavelengths of 300 nm to 800 nm and wavelengths of 380 nm to 780 nm Tables 1 to 5 also show whether or not devitrification occurs. In Tables 1 to 5, “-” indicates that no measurement was performed.

Indentation load (CIL) of Vickers indenter with a crack generation rate of 50% when indentation is formed on the mirror-finished surface of the glass plate with a thickness of 0.8 mm using a Vickers indenter (the tip angle is 136 °) And a Vickers indentation load that causes a fracture rate of 50% when a Vickers indenter (tip angle is 136 °) is applied to the mirror-finished surface of a glass plate having a thickness of 0.8 mm that has been chemically strengthened. The method for measuring (FIL) is as described above.

Absorbance was determined by the following method. The thickness t of a plate-like glass obtained by mirror-polishing both surfaces of a glass plate corresponding to a thickness of about 0.8 mm was measured with a caliper. The spectral transmittance T of the glass was measured using an ultraviolet-visible near-infrared spectrophotometer (manufactured by JASCO Corporation, V-570). In Tables 1 to 5, the spectral transmittance T is a value considering the surface reflection when the reflectance of the glass is assumed to be 4%. The absorbance A was calculated using a relational expression of A = −log ₁₀ T. Further, the minimum and maximum values of absorbance at wavelengths of 300 nm to 800 nm and wavelengths of 380 nm to 780 nm were determined.

The depth (DOL) and the surface compressive stress (CS) of the compressive stress layer after the chemical strengthening treatment of the glass were measured using a surface compressive stress meter using infrared as measurement light.
The chemical strengthening treatment was performed by preparing a glass plate having a thickness of 0.8 mm and immersing the glass in a molten salt composed of KNO ₃ (99%) and NaNO ₃ (1%) at 450 ° C. for 6 hours. The glasses of Examples 34 to 48 where devitrification occurred could not measure DOL and CS because the measurement light of the surface compressive stress meter did not pass through. Therefore, in Tables 4 and 5, “measurement impossible” was set.

The presence or absence of devitrification of the glass was determined by measuring the spectral transmittance T of a glass plate having a thickness of 0.8 mm using an ultraviolet-visible-near infrared spectrophotometer (manufactured by JASCO Corporation, V-570). When the linear transmittance at 800 nm was 1% or less, devitrification occurred. When the linear transmittance at a wavelength of 800 nm exceeded 1%, no devitrification was assumed. That is, when the linear transmittance at a wavelength of 800 nm of glass having a plate thickness of 0.8 mm exceeds 1% (that is, no devitrification), it indicates that the glass does not contain magnetite crystals.

For each glass of Examples and Comparative Examples, and the content of the aluminum component (the content of Al ₂ O ₃₎ horizontal axis, the content of iron component (content of Fe ₂ O ₃₎ and the vertical axis, devitrification FIG. 1 shows a plot in which there is no ◯ and in which no devitrification is indicated as x.

As shown in Tables 1 to 5, the chemically strengthened glass of the present invention exhibits a black color, has high strength, and can be obtained without devitrification. On the other hand, the glass of the comparative example is devitrified, and there is a possibility that the aesthetic appearance is impaired. Further, since crystals with high hardness are generated in the glass, the polishing process takes time, and productivity may be lowered. Further, in the polishing step, chipping and cracks are likely to occur on the end face of the glass, and the bending strength of the glass may be reduced.

In addition, as shown in FIG. 1, in particular, when the content of Fe ₂ O _{3 in} the glass is 2% or more and the contents of the aluminum component and the iron component do not satisfy the above formula (1), Fe ₂ O ₃ is not easily dissolved in the glass but is easily precipitated as a magnetite crystal. Therefore, it is possible to obtain a desired black glass with less devitrification by appropriately adjusting the contents of the aluminum component and the iron component so as to satisfy the above formula (1).

The chemically tempered glass of the present invention is provided around the operation panel of AV equipment / OA equipment, the door of the product, the operation button / knob, or the rectangular display surface of an image display panel such as a digital photo frame or TV. It can be used for decorative items such as decorative panels arranged on the glass or black-colored glass for electronic devices. It can also be used for interior parts for automobiles, members such as furniture, and building materials used outdoors and indoors.
The entire contents of the specification, claims, drawings and abstract of Japanese Patent Application No. 2014-049750 filed on March 13, 2014 are incorporated herein by reference. .

Claims (6)

1. In the following oxide-based mole percentage display, Fe ₂ O ₃ is contained in an amount of 0.1 to 7%, Al ₂ O ₃ is contained in an amount of 1 to 25%, and B ₂ O ₃ is contained in an amount of 0.1 to 10%.
   The minimum absorbance at a wavelength of 380 nm to 780 nm is 0.3 or more,
   A glass plate having a thickness of 0.8 mm has a Vickers indentation load of 150 gf with a crack occurrence rate of 50% when an indentation is formed on the mirror-finished surface using a Vickers indenter (the tip angle is 136 °). 1.471N) or more,
   A glass for chemical strengthening characterized by not containing magnetite crystals.
2. A glass for chemical strengthening containing 2 to 7% of Fe ₂ O ₃ ,
   The Al ₂ O ₃ X%, if the _Fe 2 _{O 3} was set to Y%, chemically strengthened glass according to claim 1, characterized in that it contains an amount indicated by the following equation (1).
   Y ≦ −0.518X + 8.924 (1)
3. The glass for chemical strengthening according to claim 1 or 2, wherein the glass contains 0.1 to 5% of V ₂ O ₅ .
4. In the molar percentage display based on the following oxide, SiO ₂ is 55 to 75%, Al ₂ O ₃ is 1 to 25%, B ₂ O ₃ is 0.1 to 10%, Na ₂ O is 10 to 20%, K ₂ O 0-5%, MgO 0-10%, CaO 0-10%, ΣRO (R represents an alkaline earth metal selected from the group consisting of Mg, Ca, Sr, Ba, and Zn .) the _{0 ~ 18%, Fe 2 O} 3 0.1 to 7% coloring components (Co, Mn, Ni, Cu , Cr, V, and a metal oxide selected from the group of metals consisting of Bi The glass for chemical strengthening according to any one of claims 1 to 3, comprising 0 to 7% of at least one component).
5. A chemically strengthened glass obtained by chemically strengthening the chemically strengthened glass according to any one of claims 1 to 4,
   With a compressive stress layer on the surface,
   Although the glass plate has a thickness of 0.8 mm, the impact load of the Vickers indenter that gives a fracture rate of 50% when the Vickers indenter (the tip angle is 136 °) is applied to the mirror-finished surface is 7 kgf (68.65 N) or more. Chemically tempered glass characterized by
6. The chemically strengthened glass according to claim 5, wherein the depth of the compressive stress layer is 10 µm or more, and the surface compressive stress of the compressive stress layer is 300 MPa or more.

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