JP2014028730A - Method for manufacturing a chemically strengthened glass and method for measuring the stress of a glass - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for measuring the stress of a glass capable of measuring the stress of even a glass having a low transmissivity within the visible light region and a method for manufacturing a chemically strengthened glass.SOLUTION: According to the provided method for measuring the stress of a glass and method for manufacturing a chemically strengthened glass, an incident beams with a wavelength exceeding 780 nm is guided into the surface layer of a glass by a beam feeding member, and after the beam propagated within the surface layer of the glass has been emitted out of the glass by a beam retrieving member, the emitted beam is separated into multiple types of beam components, and the respectively beam components are converted into emission line series.

Description

  The present invention relates to a method for producing chemically tempered glass used as an exterior member of an electronic device such as a communication device or information device that can be carried and used, and a method for measuring the stress of the glass.

  Cases of electronic devices such as mobile phones or smartphones are used by appropriately selecting materials such as resin or metal in consideration of various factors such as decoration, scratch resistance, workability, and cost. . In recent years, attempts have been made to use glass, which has not been used conventionally, as a casing material (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.

  The electronic device includes a display device such as a liquid crystal panel on the outer surface of the device. These display devices tend to have high definition and high brightness, and accordingly, backlights serving as light sources also tend to have high brightness. In addition to irradiating the light from the light source on the display device side, the light may reach the back surface of the housing that is multiple-reflected inside the device and is covered.

  Further, even in an organic EL (Electro-Luminescence) display that does not require a light source, there is a concern that light leaks from the light emitting element. When metal is used as the material of the housing, there is no problem, but when glass having transparency as described above is used, light from the light source may pass through the housing and be recognized from the outside of the device.

  Therefore, in a casing of an electronic device such as a mobile phone or a smartphone, light shielding properties are required so that components inside the device cannot be seen. Therefore, when glass is used for a housing, glass having low transmittance in the visible light region is used in order to give the glass a shielding property against visible light (hereinafter referred to as a shielding property).

  In addition, in an electronic device such as a mobile phone or a smartphone, high strength is required for the housing in consideration of damage due to a drop impact during use or contact damage due to long-term use. In addition, electronic devices such as mobile phones and smartphones are required to be lightweight and thin in order to be differentiated by thin design or to reduce the burden for movement, and are required to increase strength.

  Therefore, conventionally, in order to improve the scratch resistance of the glass, the glass is chemically strengthened to form a compressive stress layer on the surface to enhance the scratch resistance of the glass. The quality control of the strength of the glass can be controlled by stress measurement. The stress of glass is generally measured by a surface stress measuring device using the optical waveguide effect (Patent Documents 2 and 3).

JP 2009-61730 A Japanese Utility Model Publication No. 6-74941 JP-A-11-281501

However, a glass having a low transmittance in the visible light region has a problem that the stress cannot be measured by a surface stress measuring device because the transmittance in the visible region is low. Further, although the compressive stress depth can be obtained from a K ⁺ profile obtained by EPMA (Electron Probe Micro Analyzer), there is a problem that the compressive stress value cannot be obtained and cannot be measured even when it is broken.

  Therefore, an object of the present invention is to provide a glass stress measurement method and a chemically tempered glass manufacturing method capable of measuring stress even in a glass having low transmittance in the visible light region.

  The present inventors make light having a wavelength of more than 780 nm incident on the surface layer of the glass by the light supply member, and emit light that has propagated in the surface layer of the glass to the outside by the light extraction member. By separating surface light into multiple types of light components and converting each light component as a line of bright lines, the glass stress can be measured using surface-propagating light, even for glass with low transmittance in the visible light region. The present invention was completed.

That is, the present invention is as follows.
1. Light having a wavelength of more than 780 nm is incident on the surface layer of the glass by the light supply member, and light propagated in the surface layer of the glass is emitted to the outside of the glass by the light extraction member, and plural types of the emitted light are emitted. A method for measuring the stress of glass, characterized in that the light component is separated into a plurality of light components and each light component is converted into a line of bright lines.
2. 2. The method for measuring stress of glass according to item 1 above, wherein the plurality of light components are two light components that vibrate parallel and perpendicular to the glass surface.
3. 3. The glass stress measurement method according to item 1 or 2, wherein the glass is a chemically strengthened glass obtained by subjecting crystallized glass or phase-separated glass to ion exchange treatment.
4). 4. The method for measuring stress of glass according to any one of items 1 to 3, wherein a transmittance of 1 mm in thickness in a visible light region of the glass is 20% or less.
5. 5. The method for measuring stress of glass according to any one of items 1 to 4, wherein the wavelength of the light is 2500 nm or less.
6). Light having a wavelength of more than 780 nm is incident on the surface layer of the glass by the light supply member, and light propagated in the surface layer of the glass is emitted to the outside of the glass by the light extraction member, and plural types of the emitted light are emitted. A method for producing chemically tempered glass, comprising a step of measuring the stress of the glass by separating the light component into a light line array and measuring the stress of the glass.
7). 7. The method for producing chemically tempered glass according to item 6, wherein the plurality of light components are two light components that vibrate in parallel and perpendicular to the glass surface.
8). 9. The method for producing chemically strengthened glass according to 7 or 8 above, wherein the glass is chemically strengthened glass obtained by subjecting crystallized glass or phase-separated glass to ion exchange treatment.
9. 10. The method for producing chemically tempered glass according to any one of 7 to 9 above, wherein a transmittance of 1 mm in thickness in a visible light region of the glass is 20% or less.
10. 10. The method for producing chemically tempered glass according to any one of 7 to 9 above, wherein the wavelength of the light is 2500 nm or less.

  According to the method for producing chemically strengthened glass of the present invention, light having a wavelength exceeding 780 nm is incident on the surface layer of the glass by the light supply member, and a plurality of lights propagated in the surface layer of the glass by the light extraction member. Even if it is a chemically strengthened glass that is chemically tempered glass with low transmittance in the visible light region by separating the light components into seed light components and converting them into a line of bright lines, the stress using surface propagation light Can be measured efficiently and non-destructively, and the quality of the chemically strengthened glass can be stabilized and homogenized.

  In addition, according to the stress measurement method for glass of the present invention, even for a glass having a low transmittance in the visible light region, the stress can be efficiently and nondestructively measured using surface propagation light. It is very useful for designing a structure using a glass having a low transmittance in the visible light region, a machine product, or individual parts constituting them. The glass stress measurement method of the present invention is also suitable for identifying defective products.

FIG. 1 is a schematic view of an apparatus used for a stress measurement method. FIG. 2 is a diagram for explaining how to read bright lines. FIG. 3 shows a spectroscopic graph of the object to be measured. (Example)

  Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

  In the method for producing chemically strengthened glass according to the present invention, light having a wavelength exceeding 780 nm is incident on the surface layer of the glass by the light supply member, and a plurality of kinds of light propagated in the surface layer of the glass by the light extraction member. A chemically tempered glass can be produced by a conventional method, except that it includes a step of separating the light component into a bright line array.

[Method for producing glass before chemical strengthening]
The glass used for chemical strengthening in the production method of the present invention preferably has a transmittance of 1 mm in the visible light region of 20% or less, and more preferably 10% or less. Examples thereof include crystallized glass, phase-separated glass, metal fine particle-dispersed glass, or glass in which ceramic powder such as alumina, mullite, zirconia, cordierite is dispersed, and is preferably crystallized glass or phase-separated glass. . Dispersion of particles having a refractive index inside the glass results in light scattering, resulting in a glass having a low translucency and a milky white color.

(Crystallized glass)
Crystallized glass is glass that makes white light transmitted through the glass difficult to recognize on the surface side of the glass by utilizing light scattering of the crystallized glass, or has design properties.

  The crystallized glass is preferably a crystallized glass having a transmittance of 1 mm in thickness of 20% or less for any wavelength of 380 nm to 780 nm and containing nepheline solid solution crystals.

Crystallized glass containing nepheline solid solution crystals can be produced through heat treatment of the precursor as described in US Pat. No. 2,920,971. In the production of crystallized glass containing nepheline solid solution crystals, the following steps (i) to (iii) are included.
(I) Melting a glass-forming batch that usually contains a nucleating agent.
(Ii) At the same time, the melt is cooled to a temperature lower than its transition range to form a glass having a desired shape.
(Iii) The glass is subjected to a prescribed heat treatment method to crystallize the glass.

The step (iii) is divided into the following two steps (iii-1) and (iii-2).
(Iii-1) First, the original glass is heated to a temperature within or slightly higher than the transition range to form nuclei in the glass. As conditions for the heat treatment for generating nuclei in the glass, the temperature is preferably 950 ° C. or lower, and more preferably 900 ° C. or lower. Further, the heat treatment time is preferably 1 to 10 hours, and more preferably 2 to 6 hours.
(Iii-2) The glass is heated to a higher temperature, sometimes higher than its softening point, to grow crystals on the nuclei formed in (iii-1). As conditions for the heat treatment for growing the crystal, the temperature is preferably 850 to 1200 ° C., more preferably 900 to 1150 ° C. Further, the heat treatment time is preferably 1 to 10 hours, and more preferably 2 to 6 hours.

  The crystallized glass containing nepheline solid solution crystals obtained by heat treatment under the conditions within the above range is easy to ion-exchange, and the crystallized glass is ion-exchanged to provide a high light shielding property suitable for the casing. Strength can be obtained.

  In the crystallization mechanism, crystals grow substantially simultaneously on innumerable nuclei formed in advance, so that a fine-structured nepheline solid solution containing relatively uniform sized fine crystals uniformly distributed in the glass matrix Crystallized glass containing crystals is obtained, and these crystals occupy most of the glass.

Nepheline solid solution crystals are crystals represented by the formula _{Na 8-x K x Al 8} Si 8 O 32 ( the formula x varies from 0-8). Nepheline solid solution crystals have high ion exchange efficiency, and high strength can be obtained in addition to light shielding properties that are more suitable for the housing by subjecting the crystallized glass containing the crystals to ion exchange treatment.

  Further, the main crystal phase of the crystallized glass is preferably nepheline solid solution crystal. The main crystal phase of the crystallized glass is nepheline solid solution crystal, so that high ion exchange efficiency can be obtained, and the crystallized glass having the nepheline solid solution crystal as the main crystal phase is ion-exchanged so that it is more suitable for the casing. In addition to light shielding properties, high strength can be obtained.

  Typically, 20-90% of crystallized glass containing nepheline solid solution crystals is crystalline. In the present invention, the crystallinity of the crystallized glass containing nepheline solid solution crystals is preferably 20 to 70%, and more preferably 40 to 65%. By setting the degree of crystallinity to 70% or less, ions diffuse in the glass phase during the ion exchange treatment, and the ions are exchanged in the crystal phase by the diffused ions. Is obtained. Moreover, since it whitens by scattering of a crystal phase, the obtained crystallized glass can have light-shielding property suitable for a housing | casing.

The crystallinity C of the crystallized glass containing nepheline solid solution crystal is determined by performing X-ray diffraction measurement on a crystal other than nepheline solid solution crystal as a reference sample and crystallizing glass containing nepheline solid solution crystal. The ratio a of the X-ray diffraction intensity is obtained and is calculated from the mass ratio b and a of the reference sample and crystallized glass by the following formula.
C = A × a × (b / 1−b)

  Here, A is a constant referred to as a reference intensity ratio (RIR), which is a database diffraction PD that is databased from the International Center for Diffraction Data (http://www.icdd.com/). -2 Use the value shown in Release 2006.

The crystal phase that appears in nepheline solid solution crystals depends on the composition of the original glass and the heat treatment applied to the glass. “Nephelin” refers to a natural mineral having a crystal structure belonging to the hexagonal system and identified by the general chemical formula Na _8-x K _x Al ₈ Si ₈ O ₃₂ (x is 0 to 8). However, it has been found that the mineral nepheline exists as a wide range of solid solutions, the degree of which is not fully understood by the above formula (Geophical Laboratory, Paper No 1309, 'Nepheline Solid Solutions').

  The same applies to crystallized glass containing nepheline solid solution crystals, and the range of solid solutions is even wider because crystal growth occurs under unbalanced conditions. Therefore, metastable crystal glass can grow. The crystal phase of crystallized glass containing nepheline solid solution crystals may change substantially, and these crystals show a common diffraction peak with nepheline solid solution crystals in X-ray diffraction analysis, but the peak spacing and intensity are the same as those of the crystal phase. It may vary depending on the nature.

The crystallized glass containing nepheline solid solution crystals preferably contains Na ₂ O. When the crystallized glass containing the nepheline solid solution crystal contains Na ₂ O, the strength of the crystallized glass by the subsequent ion exchange treatment can be increased. The content of Na ₂ O in the crystallized glass containing nepheline solid solution crystals is preferably 10 to 50%, more preferably 12 to 40%, and still more preferably 15 to 30%.

SiO ₂ and Al ₂ O ₃ are the main components of nepheline solid solution and are essential. The content of SiO ₂ in the crystallized glass containing nepheline solid solution crystals is preferably 40 to 70%, and more preferably 45 to 64%. The content of Al ₂ O ₃ in the crystallized glass containing nepheline solid solution crystals is preferably 8 to 28%, more preferably 15 to 25%, and still more preferably 20 to 24%.

In crystallized glass containing nepheline solid solution crystals, TiO ₂ is essential as a nucleation material.

The content of TiO ₂ in the crystallized glass containing nepheline solid solution crystals is preferably 4 to 12%, and more preferably 5 to 10%.

The crystallized glass containing nepheline solid solution crystals may contain K ₂ O. K ₂ O is one of the components that form nepheline solid solution crystals, is a component that improves meltability, and is a component that increases the ion exchange rate in chemical strengthening. In order to improve the ion exchange rate, the effect is small at less than 1%. Preferably it is 2% or more. When K ₂ O exceeds 10%, the weather resistance decreases. Preferably it is 8% or less.

  The crystallized glass containing nepheline solid solution crystals is preferably whitened. By forming the crystallized glass for housing of the present invention obtained by ion-exchange treatment of crystallized glass containing nepheline solid solution crystal having whitening and light-shielding properties, it is possible to reduce the light without providing a light-shielding means separately. A highly shielding housing that exhibits a white appearance at a low cost can be obtained. Moreover, the housing | casing provided with the designability is obtained.

  The crystallized glass containing nepheline solid solution crystals preferably has a transmittance of 1 mm in thickness for any wavelength of 380 nm to 780 nm of 20% or less, more preferably 10% or less, and even more preferably 5% or less. Particularly preferably, it is 1% or less. The transmittance of crystallized glass containing nepheline solid solution crystals can be measured by ordinary transmittance measurement (linear transmittance measurement).

  The transmittance of crystallized glass containing nepheline solid solution crystals can be adjusted by adjusting the glass composition and crystallization treatment conditions.

  Co, Mn, Fe, Ni, Cu, Cr, V, Zn, Bi, Er, Tm, Nd, Sm, Sn, Ce, Pr, Eu, Ag or Au are added to the crystallized glass as coloring components. Also good. When added, it is 5% or less in terms of mol% based on oxide.

(Phase-separated glass)
The method for producing the phase-separated glass is not particularly limited. For example, a suitable amount of various raw materials are prepared, heated to about 1500 to 1800 ° C. and melted, and then homogenized by defoaming, stirring, etc. Formed into a plate shape by the downdraw method, press method or roll-out method, or cast into a block shape, and after slow cooling, processed into an arbitrary shape, and then subjected to phase separation treatment to obtain a desired shape After processing, ion exchange treatment is performed.

  In the present invention, the glass is melted, homogenized, molded, slowly cooled, or shaped without any special phase separation process in steps such as melting, homogenizing, molding, annealing, or shaping. The glass phase-separated by heat treatment is included in the phase-separated glass, and in this case, the step of phase-separating the glass is included in the melting step.

  Glass phase separation means that a single-phase glass is divided into two or more glass phases. Examples of the method for phase separation of glass include a method for heat-treating glass.

  As a condition for heat treatment for phase separation of glass, a temperature 50 to 400 ° C. higher than the glass transition point is typically preferable. A temperature higher by 100 ° C to 300 ° C is more preferable. The time for heat-treating the glass is preferably 1 to 64 hours, more preferably 2 to 32 hours. From the viewpoint of mass productivity, it is preferably 24 hours or less, and more preferably within 12 hours.

  Whether or not the glass is phase-separated can be determined by X-ray diffraction and SEM (scanning electron microscope). That is, when the glass is phase-divided, a diffraction peak due to X-ray diffraction is detected. Moreover, when the glass is phase-separated, it can be observed that it is divided into two or more phases when observed with an SEM.

The phase-separated glass preferably contains Na ₂ O. When the phase-separated glass contains Na ₂ O, the strength of the glass by the subsequent ion exchange treatment can be increased. The Na ₂ O content in the glass is preferably 1% or more. If it is less than 1%, it becomes difficult to form a desired surface compressive stress layer by ion exchange. Preferably it is 3% or more, More preferably, it is 4% or more. When Na ₂ O exceeds 17%, the weather resistance decreases. Preferably it is 14% or less, More preferably, it is 11% or less.

The phase-separated glass preferably contains SiO ₂ , Al ₂ O ₃ and MgO. When the phase-separated glass contains SiO ₂ , Al ₂ O ₃ and MgO, ion exchange is facilitated, and durability and strength are improved.

The content of SiO ₂ in the phase-separated glass is preferably 60 to 80%, more preferably 65 to 75%, and still more preferably 68 to 73%. The content of Al ₂ O ₃ in the phase-separated glass is preferably 0 to 10%, more preferably 1 to 7%, and further preferably 2 to 5%. In addition, for example, the content of Al ₂ O ₃ is preferably 0 to 10%. Al ₂ O ₃ may or may not be contained, but when it is contained, the content is preferably 10% or less. Is the meaning. The content of MgO in the phase-separated glass is preferably 5 to 30%, more preferably 10 to 28%, and still more preferably 15 to 25%.

The phase-separated glass preferably contains at least one selected from ZrO ₂ , P ₂ O ₅ , B ₂ O ₃ and La ₂ O ₃ . When the phase-separated glass contains at least one selected from ZrO ₂ , P ₂ O ₅ , B ₂ O ₃ and La ₂ O ₃ , the whiteness of the glass can be increased. The total amount is preferably 0.5 to 10%.

The content of ZrO ₂ in the phase-separated glass is preferably 0 to 5%, and more preferably 0.5 to 3%. The content of P ₂ O ₅ in the phase-separated glass is preferably 0 to 10%, more preferably 0.5 to 5%, and further preferably 1 to 4%. The content of B ₂ O ₃ in the phase-separated glass is preferably 0 to 5%, and more preferably 0.2 to 2. The content of La ₂ O ₃ in the phase-separated glass is preferably 0 to 5%, and more preferably 0.2 to 2%.

The phase-separated glass may contain K ₂ O. K ₂ O is a component for improving the meltability, and is a component for increasing the ion exchange rate in chemical strengthening to obtain a desired surface compressive stress and stress layer depth. In order to improve the meltability, the effect is small at less than 1%. Preferably it is 1% or more. In order to improve the ion exchange rate, it is preferably 2% or more, and typically 3% or more. When K ₂ O exceeds 9%, the weather resistance decreases. Preferably it is 7% or less, typically 6% or less.

  Examples of the state of the phase-separated glass include a binodal state and a spinodal state. The binodal state is a phase separation by a nucleation-growth mechanism and is generally spherical. The spinodal state is a state in which the phase separation is intertwined with each other in three dimensions with some degree of regularity. In order to increase the surface compressive stress in the chemically strengthened layer having a surface compressive stress by ion-exchanging the phase-separated glass, the phase-separated glass subjected to the ion exchange treatment is preferably in a binodal state. In particular, it is preferable that a dispersed phase of other components rich in silica is present in the alkali-rich matrix.

  The phase-separated glass is preferably whitened. The phase-separated glass preferably has a transmittance of 1 mm in thickness for any wavelength from 380 nm to 780 nm of 20% or less, more preferably 10% or less, still more preferably 5% or less, particularly preferably. Is 1% or less. The transmittance of the phase-separated glass can be measured by ordinary transmittance measurement (linear transmittance measurement).

  In order to whiten the phase-separated glass, the average particle size of the dispersed phase in the phase-separated glass is preferably 50 to 2000 nm, and more preferably 100 to 1000 nm. The average particle size of the dispersed phase can be measured by SEM observation.

  Further, in order to whiten the phase-separated glass, it is preferable that the difference in refractive index between the dispersed phase particles in the phase-separated glass and the matrix around it is large.

  Furthermore, the volume ratio of the dispersed phase particles in the phase-separated glass is preferably 10% or more, and more preferably 20% or more. Here, the volume ratio of the particles of the dispersed phase is estimated from the ratio of the dispersed particles by calculating the ratio of the dispersed particles distributed on the glass surface from the SEM observation photograph.

[Ion exchange treatment]
In the production method of the present invention, the glass is chemically exchanged by ion exchange treatment to have high strength. Chemical strengthening is a method of increasing the strength of glass by forming a compressive stress layer on the glass surface. 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 a process of exchanging Na ions or K ions for Li ions and K ions for Na ions. In the case of crystallized glass, this includes the case where alkali ions of crystals in the crystallized glass are exchanged.

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 ) A method of immersing glass in molten salt.

The conditions 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 350 to 550 ° C., and 400 to 500. More preferably, it is ° C. The time for chemical strengthening is preferably 1 to 144 hours, and more preferably 2 to 24 hours. Examples of the molten salt include KNO ₃ and NaNO ₃ . Specifically, for example, it is typical to immerse the glass in a KNO ₃ molten salt at 400 to 550 ° C. for 2 to 24 hours.

  The chemically tempered glass obtained by the production method of the present invention (hereinafter also referred to as the chemically tempered glass of the present invention) has a compressive stress layer on the surface by an ion exchange treatment. In the manufacture of glass used for housing applications, a polishing step may be performed when the glass is flat. In the glass polishing process, the grain size of the abrasive grains used in the final stage of polishing is typically 2 to 6 μm. By such abrasive grains, the surface of the glass finally has a maximum size of 5 μm. It is thought that a crack is formed.

  In order to make the effect of improving the strength by chemical strengthening effective, it is preferable to have a surface compressive stress layer deeper than the microcracks formed on the glass surface, and the depth of the surface compressive stress layer generated by chemical strengthening is 6 μm. The above is preferable. In addition, if a scratch exceeding the depth of the surface compressive stress layer is caused during use, it leads to glass breakage. Therefore, the surface compressive stress layer is preferably deeper, more preferably 10 μm or more, more preferably 20 μm or more, typically 30 μm or more.

  On the other hand, when the surface compressive stress layer becomes too deep, the internal tensile stress increases and the impact at the time of fracture increases. That is, it is known that when the internal tensile stress is large, the glass tends to break up into pieces when it breaks. 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, when the depth of the surface compressive stress layer exceeds 70 μm, scattering at the time of breakage becomes significant.

  Therefore, in the chemically strengthened glass of the present invention, the depth of the surface compressive stress layer is preferably 70 μm or less. When the chemically tempered glass of the present invention is used as a casing, depending on the electronic equipment to be packaged, for example, in a panel having a high probability of contact scratches on the surface, the depth of the surface compressive stress layer is reduced for safety. More preferably, it is 60 μm or less, more preferably 50 μm or less, and typically 40 μm or less.

[Measurement of stress]
The light used for the stress is polarized light, and the polarized light is separated into a plurality of types of light components, and these light components are respectively converted as bright line arrays. Examples of polarized light include linearly polarized light, circularly polarized light, and elliptically polarized light. The plurality of types of light components are preferably two types of light components that vibrate parallel and perpendicular to the glass surface from the viewpoint of cost and sensitivity.

  In FIG. 1, the schematic which shows the one aspect | mode of the measuring apparatus used for the stress measurement of the glass in the manufacturing method of this invention and the stress measuring method of this invention is shown. An optical glass incident prism 2 and an emitting prism 3 are respectively used as a light supply member for incident light and a light extraction member for emitting light into the surface 1a of the measured object surface. It adheres to the body surface 1a. Since light enters and exits optically through these prisms in the measured object surface 1a layer, the refractive index of the medium is larger than that of the measured object.

  Incident light 6 incident on the measured object surface 1a layer is light of more than 780 nm belonging to the infrared light region, not the visible light region. The wavelength of the incident light 6 is more than 780 nm, preferably 900 nm or more or 1000 nm or more, and more preferably 1300 nm or more. Moreover, it is preferable that it is usually 2500 nm or less, and it is more preferable that it is 2000 nm or less. When the wavelength of light incident on the surface of the glass is shorter than 780 nm, it is difficult to accurately measure the stress of the glass having low transmittance in the visible light region.

  The DUT 1 is glass, and is preferably chemically strengthened glass obtained by subjecting the glass to ion exchange treatment. In the present invention, the transmittance with a thickness of 1 mm in the visible light region of the glass whose stress is measured is preferably 20% or less, more preferably 10% or less, for any wavelength from 380 nm to 780 nm. Preferably, it is 5% or less, more preferably 1% or less.

  Specifically, for example, crystallized glass, phase-separated glass, metal fine particle-dispersed glass or glass in which ceramic powder such as alumina, mullite, zirconia or cordierite is dispersed, or by ion-exchange treatment of these glasses The chemically strengthened glass obtained is mentioned.

  Each of the prisms 2 and 3 can function as a main part of the measuring apparatus in this state if they are combined and set once as shown. In this example, a portion constituted by the incident prism 2 and the exit prism 3 is a measurement unit.

  The light from the light source 4 is linearly polarized by a polarizing element corresponding to the polarizer 5 and is converted into, for example, a slit-shaped incident light 6 through a slit-shaped opening 7, and a perpendicular line 8 at the incident point 7 on the surface 1 a to be measured is obtained. The incident light is incident at a critical refraction angle φc that totally reflects. At this time, the polarization plane of the incident light 6 makes an angle of 45 ° with respect to the incident plane.

  A part of the incident light 6 that is incident at an angle equal to the critical refraction angle φc becomes the surface propagation light 9 and travels in the vicinity of the surface 1a to be measured in parallel with the surface. The surface propagation light 9 is slightly scattered at various points along the traveling path, and the scattered light is emitted from the measured object 1 by the emission prism 3.

  The extracted emitted light 10 is passed through a polarizing element corresponding to the analyzer 11 placed in the traveling direction and an eyepiece 12 in this order, and each of the traveling paths of the surface propagation light 9 that changes with the propagation distance in the detector 13. The polarization characteristics of the points are measured.

  When polarizing infrared rays, a polarizing plate made of glass or plastic can be used. An optical filter may be used when measuring with infrared rays having a specific wavelength. An infrared camera is used for infrared detection. An infrared image detected by the infrared camera is calculated by a computer and displayed on a monitor or printed.

  The measuring device used for measuring the stress of the glass in the stress measuring method of the present invention is configured by combining the measuring unit and each optical system of the incident light 6 and the emitted light 10, and the measurement principle is known as described above. Is the same as Therefore, the constituent elements forming the optical systems of the incident light 6 and the outgoing light 10 and the combinations of these elements can be changed within the scope of the measurement principle without being specified as examples.

  Examples of the light source 4 include a semiconductor laser, a solid-state laser, a gas laser, a fiber laser, supercontinuum light, and a lamp. One or a plurality of optical filters may be used to select light having a preferable wavelength from light emitted from the light source 4. A lens may be used to obtain parallel light from the light source.

  If the light source 4 emits linearly polarized light and the light source 4 can be attached so that the polarization plane of the linearly polarized light is in a desired vibration direction, the polarizer 5 need not be arranged. Therefore, the polarizing element may be provided as a function even if it is not an independent single member like the polarizer 5. For the polarizer 5 and the analyzer 11, a polarizing element such as a polarizing plate or a Nicol prism can be used.

  The condensing lens system 14 between the light source 4 and the polarizer 5 is such that the light flux density of the slit-shaped incident light 6 is maximized, that is, the slit-shaped incident light 6 has a desired light flux density optimum for measurement. Thus, it is preferable to condense the light from the light source 4 into coherent light substantially equal to the width of the slit-shaped opening. This condensing can be performed before the slit opening or at the position of the slit opening. On the contrary, when the light source 4 has a large output and the light flux density is excessively large, the light from the light source 4 is adjusted by changing the aperture of the condenser lens system 14, and the light flux density of the slit-like incident light 6 is reduced. it can.

  Although the light flux density of the slit-shaped incident light 6 can be adjusted by the output of the light source 4, the condenser lens system can easily adjust the light flux density by adjusting the aperture, and can collect the output of the light source 4. It is particularly preferable because the light source can be used with light and does not require a very large light output. The slit-shaped opening can be replaced with another one as long as it can convert light from the light source into slit light.

  As long as the incident prism 2 and the exit prism 3 have the same function, various shapes of prisms or media other than the prisms can be employed. If the operation is the same, it is not necessary to use a structure in which the incident prism 2 and the emission prism 3 are integrated with each other as shown in FIG. Therefore, it may be provided in a portion where unnecessary light may enter, for example, a portion close to the surface to be measured 1a. And as a form of the light shielding plate, a light shielding film can also be used.

  In addition, if the incident light 6 does not enter the measurement object 1 simply by bringing the measurement unit into close contact with the measurement object surface 1a, a liquid whose refractive index is similar to that of the prism is changed to the prism and the measurement object surface. Optical contact is realized by interposing between la. When the measured object surface 1a is a flat surface, slit light can be directly incident on the measured object surface through the liquid without the incident prism 2, and in this case, the liquid It also functions as an alternative to the incident prism 2. Therefore, the incident prism 2 also includes the liquid medium.

  The method for producing chemically tempered glass of the present invention includes a step in which light having a wavelength of more than 780 nm is incident on the surface of the glass, an optical image by polarized light is observed, and the stress of the glass is measured. In the method for producing chemically strengthened glass of the present invention, the step of measuring the stress of the glass may be a sampling inspection or a 100% inspection.

  “Sampling inspection” refers to an inspection method in which a portion of glass constituting a lot is extracted in a predetermined manner and tested (or inspected), and the result is compared with a judgment criterion to determine whether the lot is acceptable or not. . Sampling inspection conditions can be appropriately adjusted depending on the glass composition, chemical strengthening conditions, and the like, and can be performed in accordance with, for example, JIS Z 9015 (1999).

(Calculation of surface compressive stress and depth of compressive stress layer)
In the chemically strengthened glass of the present invention and the stress measurement method of the present invention, light having a wavelength of more than 780 nm is incident on the surface layer of the glass by the light supply member, and propagated in the surface layer of the glass by the light extraction member. Light is emitted to the outside of the glass, the emitted light is separated into a plurality of types of light components, and these light components are converted into bright line arrays, respectively, thereby determining the surface compressive stress of the glass and the depth of the compressive stress layer. The surface layer of glass means a deteriorated layer, that is, a portion where the surface compressive stress is not zero.

  The method for determining the surface compressive stress and the depth of the compressive stress layer in the present invention will be described below by taking as an example the case where the measurement object is chemically strengthened glass.

When glass is ion-exchanged with a mixed molten salt (for example, potassium nitrate) and chemically strengthened, K ⁺ ions enter the glass surface, generating surface stress and increasing the refractive index of the surface layer. The degree of increase in the refractive index is different between component lights that vibrate perpendicularly and parallel to the surface due to the photoelastic effect due to stress, and is birefringent. Since the refractive index for light whose electric field vibrates perpendicularly to the surface is larger and the surface layer exhibits the optical waveguide effect, it can be used for surface stress measurement.

The surface layer of the chemically strengthened glass differs from the inner non-modified layer by the ion exchange treatment, and also differs depending on the depth. K ⁺ ions increase on the surface and decrease toward the bottom of the surface layer. Corresponding to this change in composition, the surface compressive stress is maximum at the surface and approximately zero at the bottom of the surface layer. The refractive index for light is maximum at the surface and decreases as it gets deeper, and constant when it is deeper than the bottom of the surface layer. At the same time, the glass has a birefringence due to the photoelastic effect caused by the strong surface compressive stress in the surface layer. The refractive index distribution is different between two linearly polarized light whose vibration directions are perpendicular to each other.

That is, the refractive index difference Δn at a certain depth has a relationship expressed by the following formula (1) with the surface compressive stress F at that depth. Thus, the surface layer has a higher refractive index than the inside, and there is also a refractive index gradient within the layer.
Δn = C × F (1)
C: Photoelastic constant of glass

  When light is incident on the surface layer of the chemically strengthened glass using a light supply member, a mode is formed when incident light from the surface and light waves transmitted to the surface layer strengthen each other. When the light is emitted through the light extraction member after passing through a finite distance, a light image (bright line) composed of a number of lines equal to the number of modes is obtained. The arrangement of bright lines (line of bright lines) corresponds to the distribution of the effective refractive index of the mode.

The bright line is obtained non-destructively, and the refractive index distribution in the surface layer can be easily estimated from the bright line. That is, the number of bright lines corresponds to the number of modes, and the position of the bright lines corresponds to the effective refractive index of the mode. From these, as shown in FIG. 2, the refractive index n _S of the surface and the refractive index n _{B of the} bottom of the surface layer are also obtained by extrapolation.

FIG. 2 is a diagram for explaining how to read bright lines when a plurality of types of light components are two types of light components that vibrate parallel and perpendicular to the glass surface as a specific example.
C1, C2: Corresponds to the refractive index n _B at the bottom of the surface layer (portion inside the surface layer of glass, unaltered layer) at the light / dark boundary on the emission line.
A1, A2: Strips formed by a mode that propagates through the shallowest part of the surface layer of glass, the position of which corresponds to the refractive index of the glass within about 3 μm from the surface layer of the glass.
B1, B2: Strips formed by a mode that travels in a shallow place following A1 and A2.
Y1, Y2: positions of virtual stripes obtained by extrapolation from A and B, corresponding to the refractive index n _S of the surface.

Since there is a strong surface compressive stress in the surface layer, the refractive index n _S of the surface and the refractive index n _B of the bottom of the surface layer are different between the two types of linearly polarized light that vibrate in directions orthogonal to each other. Therefore, by rotating the polarizing plate (analyzer) by 90 degrees from one chemically strengthened glass, the emission line and the refractive index by two kinds of light components can be obtained, and the surface compression stress and the depth of the compression stress layer are adjusted by the following procedure. Can be sought.
(1) Obtain the bright line and refractive index of the two light components.
(2) Obtain the refractive index distribution and the number of existing bright lines for each of the two types of light components.
(3) The surface compressive stress F is calculated | required by following formula (2).
F = Δn / C (2)
C: Photoelastic constant of glass Δn: Refractive index difference at a certain depth (4) The depth of the compressive stress layer is obtained by the following formula (3). n _S -n _B is usually 0.005 to 0.015, and thus corresponds to a stress layer thickness of 3 to 4 μm per number of bright lines.

N: number of bright lines n _S : refractive index of surface n _B : refractive index of bottom of surface layer

  The chemically tempered glass (hereinafter also referred to as the chemically tempered glass of the present invention) obtained by the production method of the present invention is, for example, packaged in an electronic device. On the outer surface of the mobile phone, a display device made up of a liquid crystal panel or an organic EL display and an operation device made up of buttons, or a display device such as a touch panel integrated with an operation device is arranged on one outer surface. The frame material surrounds the periphery. The other outer surface is composed of a panel. And there exists a frame material in the thickness part of the apparatus between one outer surface and the other outer surface. The frame material and the frame material, or the panel and the frame material may be configured integrally.

  The chemically strengthened glass of the present invention can be used for any of the above-mentioned frame materials, panels, and frame materials. In addition, these shapes may be flat or curved, and may be a concave shape or a convex shape in which the frame material and the frame material, or the panel and the frame material are integrated. Good.

  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. Some organic EL displays include a light emitting element that emits white light or the like without using the light source. If these white light leaks out of the device through the crystallized glass for the casing, the appearance will deteriorate. Therefore, it is preferable that the crystallized glass for a housing has a characteristic of reliably blocking white light.

  Moreover, the chemically strengthened glass of the present invention is characterized by excellent mechanical strength and the like. Therefore, it can be preferably used for a crystallized glass casing of a portable electronic device such as a mobile phone that requires high strength to the casing.

  The chemically strengthened glass of the present invention may be formed not only in a flat plate shape but also in a concave shape or a convex shape. In this case, you may press-form in the state which reheated and melt | dissolved the glass shape | molded in the flat plate or the block. Moreover, you may shape | mold into a desired shape by what is called a direct press method which flows out and press-molds a molten glass directly on a press die. Further, a portion corresponding to a display device or a connector of an electronic device may be processed simultaneously with press molding, or may be subjected to cutting after press molding.

  The chemically strengthened glass of the present invention can be suitably used for portable electronic devices. A portable electronic device is a concept that encompasses communication devices or information devices that can be carried around.

  Examples of the communication device include a mobile phone, a PHS (Personal Handy-phone System), a smartphone, a PDA (Personal Data Assistance), and a PND (Portable Navigation Device, a portable car navigation system) as a communication terminal. Examples of the device include a portable radio, a portable television, and a one-segment receiver.

  Examples of information devices include digital cameras, video cameras, portable music players, sound recorders, portable DVD players, portable game machines, notebook computers, tablet PCs, electronic dictionaries, electronic notebooks, electronic book readers, portable printers, and mobile phones. For example, a scanner. In addition, it is not limited to these for illustration.

  By using the crystallized glass for a casing of the present invention for these portable electronic devices, a portable electronic device having high strength and aesthetic appearance can be obtained.

  Note that the chemically strengthened glass of the present invention having high strength and aesthetics can be applied to a desktop personal computer, a television such as a large television, a building material, furniture, or a home appliance.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited by these.

Size: 15 mm × 15 mm, composition: expressed in mol%, SiO ₂ 66.1%, Al ₂ O ₃ 1.8%, MgO 16.5%, ZrO ₂ 0.9%, Na ₂ A glass obtained by chemically strengthening glass having O of 9.2%, P ₂ O ₅ of 5.5%, a thickness of 1 mm and a transmittance of 1550 nm at a wavelength of 1550 nm (KNO ₃ at 450 ° C. for 6 hours). The object to be measured. A spectroscopic graph of the measured object is shown in FIG.

  Using a laser diode (LD) with a wavelength of 1550 nm as the light source, as shown in FIG. 1, the emission lines and the refractive index due to the two types of polarized light (light components) are observed, and the refractive index distribution for each of the two types of light components When the number of existing bright lines was measured and the surface compressive stress (F) and the depth of the surface compressive stress layer were calculated from the following formulas (2) and (3), respectively, the surface compressive stress was 580 MPa, and the compressive stress depth was 22 μm. Become.

F = Δn / C (2)
F: surface compressive stress C: glass photoelastic constant Δn: refractive index difference at a certain depth

N: number of bright lines n _S : refractive index of surface n _B : refractive index of bottom of surface layer

DESCRIPTION OF SYMBOLS 1 Measured object 1a Measured object surface 2 Incident prism 3 Ejecting prism 4 Light source 5 Polarizer 6 Incident light 7 Incident point 8 Vertical line 9 Surface propagated light 10 Emitted light 11 Analyzer 12 Eyepiece 13 Detector 14 Condensing lens system

Claims (10)

  Light having a wavelength of more than 780 nm is incident on the surface layer of the glass by the light supply member, and light propagated in the surface layer of the glass is emitted to the outside of the glass by the light extraction member, and plural types of the emitted light are emitted. A method for measuring the stress of glass, characterized in that the light component is separated into a plurality of light components and each light component is converted into a line of bright lines.   The glass stress measurement method according to claim 1, wherein the plurality of light components are two light components that vibrate parallel and perpendicular to the glass surface.   The glass stress measurement method according to claim 1 or 2, wherein the glass is a chemically strengthened glass obtained by subjecting a crystallized glass or a phase-separated glass to an ion exchange treatment.   The glass stress measurement method according to any one of claims 1 to 3, wherein a transmittance of 1 mm in thickness in a visible light region of the glass is 20% or less.   The method for measuring stress of glass according to any one of claims 1 to 4, wherein the wavelength of the light is 2500 nm or less.   Light having a wavelength of more than 780 nm is incident on the surface layer of the glass by the light supply member, and light propagated in the surface layer of the glass is emitted to the outside of the glass by the light extraction member, and plural types of the emitted light are emitted. A method for producing chemically tempered glass, comprising a step of measuring the stress of the glass by separating the light component into a light line array and measuring the stress of the glass.   The method for producing chemically strengthened glass according to claim 6, wherein the plurality of types of light components are two types of light components that vibrate parallel and perpendicular to the glass surface.   The method for producing chemically strengthened glass according to claim 7 or 8, wherein the glass is chemically strengthened glass obtained by subjecting crystallized glass or phase-separated glass to ion exchange treatment.   The method for producing chemically strengthened glass according to any one of claims 7 to 9, wherein a transmittance of 1 mm in thickness in a visible light region of the glass is 20% or less.   The method for producing chemically strengthened glass according to any one of claims 7 to 9, wherein the wavelength of the light is 2500 nm or less.

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