WO2012128184A1 - Device for measuring surface stress of glass and method for measuring surface stress of glass - Google Patents

Abstract

Disclosed is a device for measuring surface stress of a glass provided with: a light source; a light supply member that allows light from the light source to enter in a surface layer of a tempered glass; a light extraction member that allows light traveling in the surface layer of the tempered glass to emit outside the tempered glass; and light conversion member that separates the emitted light into two types of light components vibrating parallel to and perpendicular to a boundary surface of the tempered glass and the light extraction member, and converts the light components as an emission line or a dark line. In the device, the tempered glass is a colored glass, and the light from the light source is monochromatic light having the center wavelength in a wavelength range where an absorption coefficient of the tempered glass is 4.5 mm^-1 or less.

Description

Glass surface stress measuring apparatus and glass surface stress measuring method

The present invention relates to a glass surface stress measuring apparatus and a glass surface stress measuring method for nondestructively measuring the amount of compressive stress on the surface of an object of tempered glass.

Conventionally, metallic panels and black panels have been widely used for operation panels and open / close doors of AV and OA devices. Since these panels are coated with a paint of a desired color on a resin or metal, there are problems in durability such as peeling off after long-term use. Moreover, when using these panels as a structural material, or when using as an opening-and-closing door, what was provided with high intensity | strength is calculated | required. The present applicant has applied for the glass described in Patent Document 1 as a glass exhibiting a black color suitable for applications in which both durability and high strength are required.

Incidentally, as a method for increasing the strength of glass, a method of forming a compressive stress layer on the glass surface is generally known. There are two methods for forming a compressive stress layer on the glass surface: a wind-cooling strengthening method (physical strengthening method) in which the glass plate surface heated to near the softening point is rapidly cooled by air cooling, etc., and ions at temperatures 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.

It is important to measure the amount of compressive stress for the purpose of confirming that the glass obtained by forming a compressive stress layer on the glass surface has a certain strength or more in terms of quality control. A nondestructive method for measuring surface compressive stress (hereinafter sometimes referred to as CS) and surface compressive stress layer depth (hereinafter also referred to as DOL), which is the amount of compressive stress of glass, has been proposed and put into practical use. (For example, patent document 2). This measurement method utilizes the fact that the compressive stress layer formed on the glass surface exhibits an optical waveguide effect due to the difference in refractive index from other glass portions where the compressive stress layer does not exist.

JP 2011-084456 A JP-A-53-136886

However, since the apparatus for measuring CS and DOL in a nondestructive manner emits light propagated through the surface layer of the glass and observes it, it cannot measure the above-described colored glass having a low visible transmittance such as black. The problem was newly confirmed. In this case, it is necessary to perform a strength measurement test with breakage such as bending strength, crack initiation, load, or sample processing for measuring birefringence, or use EPMA (Electron Probe Micro Analyzer) for chemically strengthened glass. There is no method for measuring the amount of compressive stress or strength of glass other than using a very time-consuming method such as measuring the depth of the diffusion layer of potassium, and the accuracy of the measurement data is low and the reliability is poor. An object of this invention is to provide the apparatus and method which measure the surface stress of the colored glass with the low transmittance | permeability of visible region.

The present invention provides a light source, a light supply member that causes light from the light source to enter the surface layer of the tempered glass, and a light extraction member that emits light propagated in the surface layer of the tempered glass to the outside of the tempered glass. A light conversion member that separates the emitted light into two types of light components that vibrate parallel and perpendicular to the boundary surface between the tempered glass and the light extraction member, and converts the light into a bright line row or a dark line row; And the light incident on the light conversion member is monochromatic light having a central wavelength in a wavelength region where the extinction coefficient of the tempered glass is 4.5 mm ⁻¹ or less. (Hereinafter, it may be called the surface stress measuring device of the glass of the present invention).

Moreover, it is a surface stress measuring apparatus of the glass of this invention, Comprising: The said tempered glass is colored glass, It is characterized by the above-mentioned. Further, in the glass surface stress measuring apparatus according to the present invention, the light from the light source is monochromatic light having a central wavelength in a wavelength region where the extinction coefficient of the tempered glass is 4.5 mm ⁻¹ or less. And Further, the glass surface stress measuring apparatus according to the present invention comprises a bandpass filter or a monochromator for extracting monochromatic light in a wavelength region where the extinction coefficient of the tempered glass is 4.5 mm ⁻¹ or less from the emitted light. It is provided between the light source and the tempered glass, or between the light extraction member and the light conversion member.

Further, in the glass surface stress measurement apparatus of the present invention, the light from the light source is monochromatic light in a wavelength region of 700 nm or more. In the glass surface stress measuring apparatus according to the present invention, the light from the light source is monochromatic light in a wavelength region of 2000 nm or less. In the glass surface stress measuring apparatus according to the present invention, the light source is a light emitting diode. In the glass surface stress measurement apparatus of the present invention, the light source is a laser.

In the glass surface stress measuring apparatus according to the present invention, the tempered glass has a minimum value of an extinction coefficient at a wavelength of 550 nm to 650 nm exceeding 1.7 mm ⁻¹ . Moreover, it is the surface stress measuring apparatus of the glass of this invention, Comprising: The said tempered glass is colored by containing a metal ion, It is characterized by the above-mentioned. In the glass surface stress measuring apparatus according to the present invention, the tempered glass is colored by depositing a metal colloid. In the glass surface stress measuring apparatus of the present invention, the tempered glass is colored by precipitating crystals. In the glass surface stress measuring apparatus according to the present invention, the tempered glass is chemically strengthened.

In addition, the glass surface stress measurement apparatus according to the present invention is an image pickup device that picks up an image of a bright line row or dark line row converted by the light conversion member, and an image obtained by the image pickup device, and the bright line row or dark line row. And an image processing device for emphasizing the image. Further, the glass surface stress measuring apparatus according to the present invention comprises a measuring means for measuring the surface stress of the tempered glass based on the bright line array or dark line array converted by the light conversion member, the measuring means comprising: The photoelastic constant of the tempered glass at a wavelength substantially the same as that of monochromatic light having a central wavelength in a wavelength range of 4.5 mm ⁻¹ or less is used.

The present invention is a method for measuring the surface stress of a tempered glass, the step of entering light from a light source into the surface layer of the tempered glass, and the step of propagating the light in the surface layer of the tempered glass. The step of emitting the light after propagation to the outside, the step of separating the emitted light into two types of light components that vibrate parallel and perpendicular to the glass surface, and the two types of separated light components, respectively The step of converting into a dark line array or bright line array and the step of measuring the surface stress of the tempered glass based on the dark line array or bright line array, and the light separated in the separating step is the tempered glass A method for measuring the surface stress of glass that is monochromatic light having a central wavelength in a wavelength range of 4.5 mm ⁻¹ or less (hereinafter sometimes referred to as the method for measuring the surface stress of glass of the present invention) is provided.

The glass surface stress measurement method of the present invention is characterized in that the tempered glass is colored. Further, in the glass surface stress measurement method of the present invention, the light from the light source is monochromatic light having a central wavelength in a wavelength region where the extinction coefficient of the tempered glass is 4.5 mm ⁻¹ or less. And The glass surface stress measurement method of the present invention is also characterized in that the tempered glass taken out by using a bandpass filter or a monochromator emits monochromatic light having a wavelength range of 4.5 mm ⁻¹ or less of the tempered glass. It enters into the surface layer of this.

The glass surface stress measurement method of the present invention is also characterized in that the tempered glass taken out using a bandpass filter or a monochromator is irradiated with monochromatic light having a wavelength range of 4.5 mm ⁻¹ or less on the glass surface. It is characterized by being separated into two types of light components that vibrate in parallel and perpendicularly. In the glass surface stress measurement method of the present invention, the monochromatic light is monochromatic light having a wavelength region of 700 nm or more. In the glass surface stress measurement method of the present invention, the light from the light source is monochromatic light in a wavelength region of 2000 nm or less.

In the glass surface stress measurement method of the present invention, the tempered glass is characterized in that the minimum value of the extinction coefficient at a wavelength of 550 nm to 650 nm exceeds 1.7 mm ⁻¹ . In the glass surface stress measurement method of the present invention, the tempered glass is colored by containing metal ions. In the glass surface stress measurement method of the present invention, the tempered glass is colored by depositing a metal colloid. In the glass surface stress measurement method of the present invention, the tempered glass is colored by precipitating crystals.

The glass surface stress measurement method of the present invention is characterized in that the tempered glass is chemically strengthened. Further, the method for measuring the surface stress of the glass of the present invention, the step of imaging the converted bright line row or dark line row, and image processing for enhancing the bright line row or dark line row from the image obtained by the imaging. And measuring the surface stress of the tempered glass based on the emphasized bright line array or the dark line array. Further, in the glass surface stress measurement method of the present invention, the step of measuring the surface stress of the tempered glass includes monochromatic light having a central wavelength in a wavelength region where the extinction coefficient of the tempered glass is 4.5 mm ⁻¹ or less. And using the photoelastic constant of the tempered glass at substantially the same wavelength.

According to the present invention, it is possible to nondestructively measure the surface compressive stress and the surface compressive stress layer depth even with a colored tempered glass having a low transmittance in the visible region.

It is the schematic which shows 1st Embodiment of the surface stress measuring apparatus of the glass in this invention, and the surface stress measuring method of glass. It is the schematic which shows 2nd Embodiment of the surface stress measuring apparatus of the glass in this invention, and the surface stress measuring method of glass. It is the schematic which shows 3rd Embodiment of the surface stress measuring apparatus of the glass in this invention, and the surface stress measuring method of glass. It is the schematic which shows the structure of the light conversion member with which the surface stress measuring apparatus of the glass in this invention is provided. It is the schematic which shows the structure of the image processing apparatus with which the surface stress measuring apparatus of the glass in this invention is provided. It is a schematic diagram of the interference fringe (bright line row or dark line row) displayed on the display provided in the surface stress measuring apparatus for glass in the present invention. It is a figure for demonstrating the measuring method of the photoelastic constant Kc in this invention. It is a figure which shows the relationship between the light absorption coefficient of the colored glass used in the Example, and a wavelength. It is an image of the interference fringe in wavelength 600nm of the colored glass C of an Example. It is an image of the interference fringe in wavelength 600nm of the colored glass D of an Example. It is an image of the interference fringe in wavelength 790nm of the colored glass C of an Example. It is an image of the interference fringe in wavelength 790nm of the colored glass D of an Example.

(First embodiment)
In FIG. 1, the schematic of the surface stress measuring apparatus 10 of the glass of the 1st Embodiment of this invention is shown.

A prism made of optical glass is placed in optical contact with the surface of the tempered glass as a medium (light supply member) that makes light incident on the surface of the tempered glass that is the object to be measured. Similarly, a prism made of optical glass is placed in a state of being in optical contact with the surface of the tempered glass as a medium (light extraction member) for emitting light propagating through the surface layer of the tempered glass to the outside of the tempered glass. . Since light optically enters and exits through the prisms on the surface of the tempered glass, those having a refractive index larger than that of the tempered glass are used. A light source is arrange | positioned so that light may inject into the surface layer of tempered glass from the prism which is a light supply member. The light conversion member is disposed in a direction in which light propagating through the surface layer of tempered glass is emitted from a prism that is a light extraction member. The light conversion member vibrates in the emission direction of light propagated through the surface layer of tempered glass, parallel and perpendicular to the boundary surface between the tempered glass surface and the prism that is the light supply member, that is, the emission surface. Are separated into two types of light components, and each of these components is converted into a bright line row or a dark line row, respectively. A means for observing the bright line array or the dark line array as an interference fringe image is provided. Using these apparatus configurations, the amount of compressive stress (CS, DOL) of the tempered glass is measured.

Chemically strengthened or air-cooled tempered glass has a compressive stress layer on the surface. These compressive stress layers have a higher refractive index than glass portions other than the compressive stress layer. These refractive indexes increase monotonously from the bottom to the surface of the compressive stress layer. Further, the birefringence of the compressive stress layer also monotonously increases toward the surface. Therefore, there are two depth versus refractive index curves for light oscillating perpendicular to the glass surface and light parallel to the glass surface, resulting in different optical waveguide effects and comparing the resulting interference fringe images. Thus, the surface compressive stress and the surface compressive stress layer depth of the tempered glass can be obtained.

Therefore, in the surface stress measuring apparatus 10 using the optical waveguide effect described above, it is possible to obtain an interference fringe image composed of a bright line array or a dark line array by light oscillating perpendicularly to the glass surface and light oscillating parallel to the glass surface. It is essential.

However, in the existing glass surface stress measuring device, when the tempered glass is colored, when the light from the light source propagates through the surface layer of the tempered glass, it is absorbed by the metal ions or the like as the coloring component and emitted. There is a problem that it is difficult to recognize interference fringe images using light.

In contrast, in the surface stress measurement apparatus 10 of the present invention, the wavelength of light from the light source incident on the light supply member is centered in the wavelength region where the extinction coefficient of the tempered glass as the object to be measured is 4.5 mm ⁻¹ or less. By using monochromatic light having a wavelength, an interference fringe image can be clearly observed even with a colored tempered glass, and thus CS and DOL of the tempered glass can be accurately measured in a non-destructive manner.

The calculation method of the extinction coefficient 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 extinction coefficient β is calculated using a relational expression of T = 10− ^βt .

As described above, it is preferable to use a light source capable of emitting monochromatic light having a central wavelength in a wavelength region where the extinction coefficient of the to-be-measured object is 4.5 mm ⁻¹ or less. When the tempered glass is colored, the incident light is absorbed by the influence of the contained metal ions and metal colloids, so that the emitted light may be very weak or unrecognizable. On the other hand, by making the light source as described above, the influence of light absorption by the tempered glass is reduced, and therefore, the surface stress layer can be measured with high accuracy. If light having a wavelength of the tempered glass having an extinction coefficient exceeding 4.5 mm ⁻¹ is used as the light source, the emitted light becomes weak for the reasons described above and it is difficult to recognize the interference fringe image, which is not preferable as the light source of the present invention. . Further, it is preferable to use light having a wavelength extinction coefficient of 4 mm ^-1 or less tempered glass to the light source, the absorption coefficient of tempered glass that is more preferable to use light having a wavelength of 3 mm ^-1 or less as the light source, the tempered glass More preferably, light having an extinction coefficient of 2 mm ⁻¹ or less is used as the light source.

Any light source may be used as long as the light source itself can emit monochromatic light having a center wavelength in a wavelength region where the extinction coefficient of the tempered glass is 4.5 mm ⁻¹ or less. Moreover, even if the light source is not monochromatic light, the light from the light source incident on the tempered glass is converted into monochromatic light by using means for monochromatic light such as a bandpass filter or a monochromator between the light source and the tempered glass. Also good. Even if the light source is monochromatic light, means for monochromatic light such as a bandpass filter or a monochromator may be used in order to make the light from the light source a monochromatic light with a narrower half-value width. By using monochromatic light with a narrow half-value width as the light source, the influence of other wavelengths can be eliminated as much as possible, and a clearer interference fringe image can be obtained.

The light from the light source is preferably monochromatic light having a wavelength range of 700 nm or more. This makes it possible to accurately measure the CS and DOL of the surface stress layer even with glass that does not substantially transmit visible light, such as black. In addition, in the conventional surface stress measuring apparatus and method, even a colored glass that transmits a part of visible light for which an interference fringe image could not be recognized due to the measurement wavelength can be measured. The light from the light source can be used as long as it is monochromatic light in a wavelength region of 700 nm or more, but it is preferable to use a shorter wavelength in the infrared region. As a reason, when light having a long wavelength is used as a light source, the change with respect to the refractive index fluctuation of the glass becomes dull, and the number of interference fringes obtained is small, and the DOL measurement accuracy tends to be lowered. Further, the sensitivity of the image sensor is better as the wavelength is shorter in the infrared region, and the accuracy of the apparatus can be increased. Furthermore, when a bandpass filter is used, it is possible to obtain a filter having a narrower half-value width when the wavelength is shorter, and the accuracy of the apparatus can be improved. From the above, the light from the light source is preferably monochromatic light having a wavelength range of 2000 nm or less, more preferably monochromatic light having a wavelength range of 1500 nm or less. Most preferred is monochromatic light having a wavelength range of 950 nm or less.

As the light source, any kind of light source can be used as long as it can obtain a desired monochromatic light. For example, a light emitting diode or a laser can be preferably used. Since light emitting diodes having various center wavelengths are available, a light source corresponding to the extinction coefficient characteristic of the tempered glass can be appropriately selected. Further, since the life of the light source is long, the replacement frequency can be lowered.

Laser has high output, narrow half width, and can obtain linearly polarized monochromatic light. Therefore, it is possible to improve measurement accuracy without using a bandpass filter or the like. Further, by using a laser line filter, which is a kind of bandpass filter, in combination with a laser, it is possible to obtain monochromatic light with a very narrow half-value width. In addition, when using means for monochromatic light, such as a bandpass filter or a monochromator, a light source such as a xenon lamp, a metal halide lamp, or a mercury lamp can be used.

The light supply member and the light extraction member can each be a prism made of optical glass having a refractive index higher than that of tempered glass. Further, the light supply member prism and the light extraction member prism may be separate as shown in FIG. 1 or may be integrated. Further, the light shielding means may be sandwiched between these prisms and integrated. The light shielding means is used for the purpose of eliminating unnecessary ambient light from entering a prism that is a light extraction member. As the light shielding means, a shielding plate made of metal or the like, or a shielding film made of a metal thin film can be used. If the surface of the tempered glass and each prism are in close contact, and light does not enter or exit well, a liquid whose refractive index is similar to that of each prism is interposed between the tempered glass and each prism. And may be optically contacted.

The light conversion member is for observing light emitted from the surface layer by the light from the light source being incident on the surface layer of the tempered glass, propagating through the surface layer. The light emitted from the tempered glass causes birefringence between the light whose direction of vibration is along the glass surface and the light perpendicular to the surface due to the surface compressive stress of the surface layer. Both have the same refractive index gradient, but have different refractive angles because of different effective refractive indexes. Therefore, it is possible to measure CS and DOL by observing both the dark line caused by the light oscillating in the direction perpendicular to the dark line caused by the light oscillating in the direction parallel to the incident surface of the emitted light. As a method of extracting these two kinds of light components from the emitted light, a single or a plurality of polarizing plates are used. Moreover, as a means of observing the interference fringe image consisting of the obtained dark line array, a method of manually reading the scale using an eyepiece micrometer, a solid-state image pickup device such as a CCD or CMOS arranged on the focal plane is obtained. A method of calculating CS or DOL by analyzing the interference fringe image can be used. Further, for the purpose of extracting only monochromatic light having a specific wavelength from the emitted light, a band pass filter, a monochromator, or the like may be disposed in front of the polarizing plate. In addition, about a structure of a light conversion member, not only the said form but a well-known thing can be used.

(Second Embodiment)
Next, the glass surface stress measuring apparatus 20 and the glass surface stress measuring method according to the second embodiment of the present invention will be described. In FIG. 2, the schematic of the surface stress measuring apparatus 20 of the glass of the 2nd Embodiment of this invention is shown.

The glass surface stress measuring device 20 of the second embodiment is a band-pass filter that extracts monochromatic light in a wavelength region where the extinction coefficient of the tempered glass to be measured is 4.5 mm ⁻¹ or less from the light emitted from the light extraction member. Alternatively, the surface stress of the glass according to the first embodiment described with reference to FIG. 1 except that a monochromator is provided between the light extraction member and the light conversion member, and light from the light source is not limited to monochromatic light. Since the configuration is the same as that of the measuring apparatus 10, the description thereof is omitted.

When measuring glass that hardly transmits visible light, for example, black, it is preferable to use a light source with a large amount of light in order to use light in a wavelength region that can pass through the glass for measurement. At that time, even if the light source itself does not emit monochromatic light, it is equipped with a band-pass filter or monochromator that takes out monochromatic light of a specific wavelength between the light extraction member and the light conversion member, so that a monochromatic light with a certain amount or more is obtained. Light can be obtained, whereby a clear interference fringe image can be obtained. Further, by cutting light having a wavelength that is not related to the measurement just before the light conversion member, noise caused by light having a wavelength that is not related to the measurement is eliminated, and a clear interference fringe image can be obtained. The monochromatic light extracted by the bandpass filter or the monochromator needs to be light in a wavelength region where the extinction coefficient of the tempered glass to be measured is 4.5 mm ⁻¹ or less. Use of monochromatic light having a wavelength range in which the extinction coefficient of the tempered glass exceeds 4.5 mm ⁻¹ is not preferable because light entering the light conversion member becomes weak and makes it difficult to recognize an interference fringe image. As the light source having a large light amount, a known light source such as a xenon lamp, a metal halide lamp, or a mercury lamp can be used. Further, in order to eliminate the influence other than the desired wavelength from the light emitted from the light extraction member, it is preferable that the bandpass filter or the monochromator can extract monochromatic light having a half-value width as narrow as possible.

As the monochromatic light extracted using a bandpass filter or a monochromator, monochromatic light having a wavelength range of 700 nm or more is preferably used. This makes it possible to accurately measure the CS and DOL of the surface stress layer even with glass that does not substantially transmit visible light, such as black. In addition, in the conventional surface stress measuring apparatus and method, even a colored glass that transmits a part of visible light for which an interference fringe image could not be recognized due to the measurement wavelength can be measured. Note that monochromatic light extracted using a band-pass filter or a monochromator can be used as long as it is monochromatic light having a wavelength region of 700 nm or more, but it is preferable to use a shorter wavelength in the infrared region. As a reason, when light having a long wavelength is used as a light source, the change with respect to the refractive index fluctuation of the glass becomes dull, and the number of interference fringes obtained is small, and the DOL measurement accuracy tends to be lowered. Further, the sensitivity of the image sensor is better as the wavelength is shorter in the infrared region, and the accuracy of the apparatus can be increased. Furthermore, when a bandpass filter is used, it is possible to obtain a filter having a narrower half-value width when the wavelength is shorter, and the accuracy of the apparatus can be improved. From the above, the monochromatic light is preferably monochromatic light having a wavelength range of 2000 nm or less, and more preferably monochromatic light having a wavelength range of 1500 nm or less. Most preferred is monochromatic light having a wavelength range of 950 nm or less.

(Third embodiment)
FIG. 3 is a schematic view of a glass surface stress measuring apparatus 30 according to a third embodiment of the present invention. Here, the glass surface stress measuring device 30 and the glass surface stress measuring method of the third embodiment of the present invention will be described. Colored glass has lower light transmittance than conventional transparent glass, so the boundary between bright line or dark line array obtained by the light conversion member is blurred, and accurate surface stress (CS, DOL) May not be calculated. For example, the surface compressive stress depth (DOL) is specified by interference fringes formed by light reflected from the deepest portion in the depth direction. However, since the light reflected from the deepest part has a long optical path length propagating in the glass, the attenuation of light (luminance) becomes large and it is difficult to clearly recognize it as an interference fringe. Therefore, in the third embodiment, the obtained bright line array or dark line array image is subjected to image processing, and the bright line array or dark line array is emphasized to calculate a more accurate surface stress amount (CS, DOL). I am doing so. Hereinafter, the configuration of the glass surface stress measuring apparatus 30 according to the third embodiment will be described with reference to FIG. 3, but the glass according to the first and second embodiments described with reference to FIGS. About the same structure as the surface stress measuring apparatus 10, the same code | symbol is attached | subjected and the overlapping description is abbreviate | omitted.

(Configuration of Glass Surface Stress Measuring Device 30)
The glass surface stress measurement device 30 according to the third embodiment includes a light source 2, a bandpass filter 3, a light supply member 4, a light extraction member 5, a light conversion member 6 </ b> A, and an image processing device 11. .

FIG. 4 is a schematic diagram showing the configuration of the light conversion member 6A provided in the glass surface stress measurement device 30. As shown in FIG. The light conversion member 6A includes a lens 6a, a polarizing plate 6b, an image sensor 6c, and a housing 6d. The lens 6 a converges the light emitted from the light extraction member 5. The polarizing plate 6 b separates two types of light components that vibrate in parallel and perpendicular to the boundary surface between the tempered glass 1 and the light extraction member 5 from the light emitted from the light extraction member 5. The light that has passed through the polarizing plate 6b is recognized as a bright line array or a dark line array. When the separated light component is passed, it is recognized as a bright line row, and when the light component other than the separated light component is passed, it is recognized as a dark line row. Note that an IR (infrared) polarizing plate is preferably used for the polarizing plate 6b.

The imaging element 6c is an image sensor (for example, a CCD (Charge-Coupled Device) image sensor, a CMOS (Complementary Metal-Oxide Semiconductor) image sensor) for observing a bright line array or a dark line array as an interference fringe image. The image sensor 6c photoelectrically converts the received light and outputs the luminance value for each of the plurality of pixels constituting the image to the image processing apparatus 11 as digital image data.

FIG. 5 is a schematic diagram showing the configuration of the image processing apparatus 11 provided in the glass surface stress measurement apparatus 30. The image processing apparatus 11 includes an image correction unit 11a, an enhancement unit 11b, a D / A converter 11c, and a display 11d.

The image correction unit 11a performs white balance adjustment and γ correction on the digital image data output from the image sensor 6c.

The emphasis unit 11b emphasizes the contrast of the digital image data after correction, and emphasizes the bright line row or the dark line row. For example, the following method can be adopted as a method for enhancing the contrast of the bright line array or the dark line array. Note that the following method may be applied to the entire interference fringe image obtained by the imaging device 6c, or may be applied only to a specific image area where light attenuation is large. For example, in order to specify the deepest part of the surface compressive stress depth, image processing that emphasizes only the image area corresponding to the periphery of the deepest part may be performed.

(First method)
In the first method, the bright line row or the dark line row is emphasized by binarizing the luminance value of each pixel constituting the image with a threshold value stored in advance. For example, when the luminance value is set from 0 (minimum luminance: black) to 255 (maximum luminance: white), the luminance value of a pixel having a luminance value exceeding the threshold value (for example, 127) is set to 255, and the threshold value (for example, 127) It can be binarized by setting the luminance value of a pixel having a luminance value equal to or less than 0 to 0.

(Second method)
In the second method, the bright line row or the dark line row is emphasized by enhancing the outline (edge). In this edge enhancement, an existing edge enhancement filter (for example, a sharpness filter) may be used.

The D / A converter 11c converts the digital image data in which the bright line row or dark line row is emphasized into analog image data that can be displayed on the display 11d. The display 11d is, for example, a liquid crystal display or a CRT (Cathode Ray Tube), and displays an image corresponding to the analog image data output from the D / A converter 11c on the screen.

(Calculation of CS and DOL)
FIG. 6 is a schematic diagram of bright line rows or dark line rows displayed on the display 11d. Note that the bright line row or dark line row on the left side of FIG. 6 is the bright line row or dark line row of the light component that vibrates perpendicularly to the boundary surface between the tempered glass 1 and the light extraction member 5. Further, the bright line row or dark line row on the right side of FIG. 6 is the bright line row or dark line row of the light component that vibrates parallel to the boundary surface between the tempered glass 1 and the light extraction member 5.

From the interference fringes displayed on the display 11d, the surface compressive stress (CS) and the surface compressive stress layer depth (DOL) can be calculated. Specifically, the distance difference Δt between the bright line array or the dark line array of two types of light components that vibrate parallel and perpendicular to the boundary surface between the tempered glass 1 and the light extraction member 5 separated by the light conversion member 6A. The surface compressive stress (CS) can be calculated from (see FIG. 6). Further, the surface compressive stress layer depth (DOL) can be calculated from the number of bright line rows or dark line rows.

In addition, although the photoelastic constant Kc is used for the calculation of the surface compressive stress (CS) and the surface compressive stress layer depth (DOL), this photoelastic constant Kc is actually substantially the same as the light source incident on the tempered glass. The photoelastic constant of the tempered glass at a wavelength is preferred. That is, it is the photoelastic constant of the tempered glass at substantially the same wavelength as the monochromatic light having the central wavelength in the wavelength region where the extinction coefficient of the tempered glass incident on the light conversion member is 4.5 mm ⁻¹ or less. This is because the photoelastic constant obtained depends on the wavelength used. Here, the substantially same wavelength means a wavelength within a range of several nm to several tens of nm centering on the same wavelength.

(Measuring method of photoelastic constant Kc)
Here, the photoelastic constant Kc is a constant representing the relationship between the stress F and the optical path difference δ due to birefringence, and satisfies the relationship of the following equation (1), where d is the thickness of the glass.
δ = Kc · d · F (1)

That is, when attempting to measure the photoelastic constant Kc of the tempered glass, it is necessary to measure the photoelastic constant Kc by applying stress to the tempered glass. However, like this embodiment, when the tempered glass which is a measuring object of the surface compressive stress (CS) and the surface compressive stress layer depth (DOL) is a colored glass, if the tempered glass is too thick, it passes through the tempered glass. There is a possibility that the amount of light to be performed is not sufficient and the photoelastic constant Kc cannot be measured, or an accurate value of the photoelastic constant Kc cannot be obtained. On the other hand, if the tempered glass is thin, the tempered glass cannot withstand the applied stress and may be damaged.

FIG. 7 is a diagram for explaining a method of measuring the photoelastic constant Kc in the present invention. Hereinafter, a method for measuring the photoelastic constant Kc in the present embodiment will be described with reference to FIG. Here, a method for measuring the photoelastic constant Kc will be described by taking as an example a four-point bending method in which force F is applied from four points to the tempered glass 1 having the photoelastic constant Kc to apply a bending stress.

From the light source 101, the tempered glass 1 has a central wavelength in a wavelength region where the extinction coefficient is 4.5 mm ⁻¹ or less, and monochromatic light in a wavelength region of 700 nm to 2000 nm, more preferably 700 nm to 1500 nm. Monochromatic light is emitted. The wavelength of the monochromatic light of the light source 101 is substantially the same as the wavelength of the light incident on the light conversion member of the glass surface stress measurement device.

The polarizing plates 102 and 104 are arranged so that they are orthogonal to each other, that is, have a phase difference of 90 degrees, with the tempered glass 1 and the Babinet correction plate 103 that are the objects of measurement of the photoelastic constant Kc interposed therebetween. The polarizing plate 102 allows only the light component polarized in a specific direction out of the light emitted from the light source 101. Further, the polarizing plate 104 allows only the light component polarized in the direction orthogonal to the polarizing direction of the polarizing plate 102 among the light transmitted through the tempered glass 1 to pass therethrough. The Babinet correction plate 103 is a compensation plate made of quartz. The photodetector 105 receives the light that has passed through the polarizing plate 104. The force F is applied by a load application mechanism (not shown) such as a loader.

As shown in FIG. 7, in the present invention, the thickness of the tempered glass 1 is set to a thickness that allows light from the light source 101 to pass therethrough, and the load application direction is not the thickness direction of the tempered glass 1, but the tempered glass 1 The force F is applied from the thick side. For this reason, it is possible to suppress the possibility that the amount of light passing through the tempered glass is not sufficient and the photoelastic constant Kc cannot be measured and that the accurate value of the photoelastic constant Kc cannot be obtained. Further, the tempered glass 1 cannot withstand the load to which it is applied and can be prevented from being damaged.

As described above, in the present invention, image processing is performed and the bright line array or dark line array is emphasized, so that the surface stress amount (CS, DOL) of the tempered glass 1 can be measured more accurately. In addition, in measurement of the photoelastic constant Kc used when calculating the surface compressive stress (CS) and the surface compressive stress layer depth (DOL), the light is actually incident on the light conversion member of the surface stress measuring device of the tempered glass 1. Light having substantially the same wavelength as the light to be emitted, that is, monochromatic light having a central wavelength in a wavelength region where the extinction coefficient of tempered glass is 4.5 mm ⁻¹ or less and having a wavelength region of 700 nm to 2000 nm. For this reason, the surface stress amount (CS, DOL) of the tempered glass 1 can be measured more accurately. The light used for measuring the photoelastic constant Kc is more preferably monochromatic light having a wavelength range of 700 nm to 2000 nm.

The object of the present invention is to measure the surface stress of tempered glass in which the glass itself is colored. Examples of the colored tempered glass include the following forms.

As a 1st form, it is glass which contains a metal ion in tempered glass and was colored by absorption of the light of the specific wavelength by a metal ion. When the transition metal element or rare earth element contained in the glass is an element having a plurality of valences, the glass has a specific color due to the influence of the wavelength of light that is selectively absorbed by the transition of electrons. Since the transition metal ion dissolved in the glass is strongly influenced by the anion adjacent to the outer shell, the wavelength of light that is selectively absorbed is influenced by factors such as the basic glass composition, the melting atmosphere, and the additive components. In addition, since the rare earth element atoms are completely filled with electrons in the electron orbit close to the outer shell, and incomplete in the electron orbits inside, the electron transition occurs in the inner orbits and light Since selective absorption of the wavelength is performed, the color is almost constant without being affected by the basic glass or the molten atmosphere. For example, when transition metal ions are used, the glass can be colored blue by containing Cu ²⁺ in the glass. Moreover, when using rare earth elements, it can be set as the glass colored pink by containing Er3 ⁺ in glass.

As a second form, glass containing metal colloid in tempered glass and colored with metal colloid. When colloids smaller than the wavelength of light are present in the glass, the glass is colored by absorbing specific (wavelength) light. For example, a colloid of gold or copper is precipitated in the glass, whereby a red colored glass can be obtained.

A third form is a glass that is recognized as milky white by scattering incident light by precipitating crystalline particles on tempered glass.

The colored tempered glass described above has different wavelengths to be absorbed depending on coloring components and the like. In the glass surface stress measuring apparatus and method of the present invention, the wavelength of light from the light source is monochromatic light having a central wavelength in a wavelength region where the extinction coefficient of the tempered glass is 4.5 mm ⁻¹ or less. The incident fringe image can be clearly recognized from the emitted light without being absorbed by the coloring component when the incident light propagates through the surface layer. Further, the tempered glass may have a minimum value of an extinction coefficient of light having a wavelength of 550 nm to 650 nm exceeding 1.7 mm ⁻¹ . Glass having such an extinction coefficient cannot recognize an interference fringe image with a conventional surface stress measurement device. Alternatively, even if the interference fringe image can be recognized, there is a problem that it is unclear and it is difficult to automatically process the image. The present inventor measured a colored tempered glass having a minimum extinction coefficient of light having a wavelength of 550 nm to 650 nm slightly exceeding 1.7 mm ⁻¹ using a conventional surface stress measuring device, and found an interference fringe image. I couldn't recognize it. By measuring the tempered glass having the minimum extinction coefficient of light having a wavelength of 550 nm to 650 nm exceeding 1.7 mm ⁻¹ using the surface stress measuring apparatus and method of the present invention, the interference fringe image can be clearly recognized and accurately detected. It is possible to measure the surface stress.

There are an air-cooling tempering method and a chemical tempering method as tempering methods in tempered glass, but the present invention can be applied to any glass tempered by either method. The air-cooling strengthening method is a method in which a cold wind is applied to a glass plate once heat-treated to cool it, thereby forming a compressive stress on the surface. In addition, the chemical strengthening method, for example, by placing soda lime glass in a potassium nitrate molten salt heated to about 380 ° C., ion exchange of alkali ions (sodium ions as glass components in molten salt having a larger ion radius) This is a method of forming compressive stress on the glass surface by ion exchange with potassium ions. Each of the strengthening treatments forms a surface compression layer on the surface layer of the glass, and they have a refractive index different from that of the glass portion other than the surface compression layer. Therefore, any tempered glass subjected to any tempering treatment can be measured by the surface compression measuring apparatus and method of the present invention using the optical waveguide effect of the surface layer. Further, the tempered glass includes a glass having a multilayer structure in which glasses having different thermal expansion coefficients are laminated, and the case where the surface layer glass is colored glass is also included in the form. Moreover, the glass in which the surface of the glass serving as the core is coated with a colored soot having a different thermal expansion coefficient from that of the glass serving as the core is also included in the form of the colored glass.

As a colored tempered glass, SiO ₂ 61.9%, Na ₂ O 11.5%, K ₂ O 3.9%, MgO 10.6%, Al ₂ O ₃ 5 in terms of mole percentage based on oxide. , 8%, ZrO 2.4%, Co ₃ O ₄ 0.4%, Fe ₂ O ₃ 3.3%, SO ₃ 0.4% black sheet glass (glass A), SiO ₂ 62 0.1%, Na ₂ O 11.6%, K ₂ O 3.9%, MgO 10.6%, Al ₂ O ₃ 5.8%, ZrO 2.4%, Fe ₂ O ₃ 3.3%, SO ₃ 0.4% black sheet glass (glass B), SiO ₂ 62.0%, Na ₂ O 12.0%, K ₂ O 3.9%, MgO 10.1%, Al _{2 O 3 7.7%, ZrO 0.5%} , Co 3 O 4 0.4%, Fe 2 O 3 3.3%, or SO 3 0.1% Sheet glass exhibiting made black (glass _{C), SiO 2 63.8%,} Na 2 O 10.5%, K 2 O 4.0%, MgO 10.4%, Al 2 O 3 8.0%, A plate-like glass (glass D) having a black color composed of ZrO 0.4%, Co ₃ O ₄ 0.05%, TiO ₂ 0.3%, NiO 0.65%, SO ₃ 0.1% was prepared. .

The glasses A to D were immersed in KNO ₃ molten salt at 450 ° C. for 6 hours to be chemically strengthened. When these glasses A to D were analyzed for potassium concentration in the depth direction using EPMA, ion exchange occurred from the surface to a depth of about 30 μm, and a compressive stress layer was formed. FIG. 8 shows the relationship between the absorption coefficient and the wavelength of Glass A and Glass B.

Regarding glass A to glass D, it was confirmed whether or not an interference fringe image could be observed with a surface stress measurement device when a sodium lamp was used as the light source and a wavelength of 600 nm was used as the measurement light. The absorption coefficient of glass A at a wavelength of 600 nm is 5.7 mm ⁻¹ , and the absorption coefficient of glass B at a wavelength of 600 nm is 1.37 mm ⁻¹ . The absorption coefficient of glass C at a wavelength of 600 nm is 5.47 mm ⁻¹ , and the absorption coefficient of glass D at a wavelength of 600 nm is 1.37 mm ⁻¹ .

As a result, glass B was able to observe an interference fringe image, whereas glass A could not confirm the interference fringe image. This is presumably because the incident light having a wavelength of 600 nm is absorbed when propagating through the surface layer of the glass A, and the emitted light is extremely weak.

Next, for glass A, when an infrared light emitting diode was used as a light source and a wavelength of 850 nm was used as measurement light, it was confirmed whether an interference fringe image could be observed with a surface stress measurement device. The absorption coefficient of glass A at a wavelength of 850 nm is 1.17 mm ⁻¹ . As a result, an interference fringe image of glass A could be confirmed. This is presumably because incident light with a wavelength of 850 nm was partially absorbed when propagating through the surface layer of glass A, but its attenuation was small and could be recognized as emitted light.

Next, for glass A, a xenon lamp was used as the light source, a bandpass filter was placed between the light extraction member (prism) and the light conversion member, and it was confirmed whether an interference fringe image could be observed with a surface stress measurement device. . In addition, the band pass filter used what selectively permeate | transmits only the light of wavelength 850nm vicinity, and took out monochromatic light from the light which inject | emitted the glass A by this. As a result, an interference fringe image of glass A could be confirmed. This is presumably because incident light with a wavelength of 850 nm was partially absorbed when propagating through the surface layer of glass A, but its attenuation was small and could be recognized as emitted light.

Next, interference fringe images observed with the surface stress measuring apparatus for glass C and glass D are shown in FIGS. As a result, the glass C could not observe an interference fringe image. Glass D was able to confirm an interference fringe image. However, the boundary on the right side of the interference fringe image (the portion indicating the depth of the compressive stress layer) is unclear, and an accurate value cannot be obtained by calculating DOL using the automatic processing of the surface stress measurement device. It was.

Subsequently, for glass C and glass D, when an infrared light emitting diode was used as a light source and a wavelength of 790 nm was used as measurement light, it was confirmed whether an interference fringe image could be observed with a surface stress measurement device. Incidentally, the absorption coefficient at a wavelength of 790nm of the glass C is 1.12 mm ^-1 and the absorption coefficient at a wavelength of 790nm of the glass D is 0.16 mm ^-1.

FIGS. 11 and 12 show interference fringe images observed with a surface stress measuring device for glass C and glass D. FIG. As a result, both the glass C and the glass D were able to confirm interference fringe images. In both glasses, an accurate value could be obtained by calculating the DOL using the automatic processing of the surface stress measuring device.

(Other embodiments)
The forms of the present invention described above are merely examples, and the present invention is not limited to these. The components forming each optical system, such as the light source and the light conversion member, and the combination of these components are not limited to those illustrated, but can be changed within the scope of the measurement principle. For example, you may use as an apparatus which measures the surface stress amount (CS, DOL) of both the colored tempered glass with a low visible region transmittance | permeability and the transparent tempered glass with a high visible region transmittance | permeability. Thereby, transparent glass and colored glass can be measured with the same surface stress meter.

According to the glass surface stress measuring apparatus and the glass surface stress measuring method of the present invention, the surface stress amount (CS, DOL) of the colored tempered glass having low transmittance in the visible region can be accurately measured nondestructively. Is possible.

DESCRIPTION OF SYMBOLS 1 ... Tempered glass, 2 ... Light source, 3 ... Band pass filter, 4 ... Light supply member (prism), 5 ... Light extraction member (prism), 6, 6A ... Light conversion member, 6a ... Lens, 6b ... Polarizing plate, 6c ... Image sensor, 6d ... Case, 7 ... Surface stress layer, 8 ... Light from light source (incident light), 9 ... Ejecting light, 11 ... Image processing device, 11a ... Image correction unit, 11b ... Enhancer , 11c ... D / A converter, 11d ... display, 10, 20, 30 ... glass surface stress measuring device, 101 ... light source, 102, 104 ... polarizing plate, 103 ... Babinet correction plate, 105 ... photo detector.

Claims (29)

1. A light source;
   A light supply member for allowing light from the light source to enter the surface layer of tempered glass;
   A light extraction member for injecting the light propagated in the surface layer of the tempered glass out of the tempered glass;
   A light conversion member that separates the emitted light into two types of light components that vibrate parallel and perpendicular to the boundary surface between the tempered glass and the light extraction member, and converts the light into a bright line or a dark line;
   With
   The glass surface stress measurement apparatus according to claim ¹ , wherein the light incident on the light conversion member is monochromatic light having a central wavelength in a wavelength region in which the extinction coefficient of the tempered glass is 4.5 mm ⁻¹ or less.
2. 2. The glass surface stress measuring apparatus according to claim 1, wherein the tempered glass is colored glass.
3. The surface of the glass according to claim 1 or 2, wherein the light from the light source is monochromatic light having a central wavelength in a wavelength region where the extinction coefficient of the tempered glass is 4.5 mm ^-1 or less. Stress measuring device.
4. A band-pass filter or a monochromator that extracts monochromatic light in a wavelength range where the extinction coefficient of the tempered glass is 4.5 mm ⁻¹ or less from the emitted light is provided between the light source and the tempered glass, or the light extraction member. The glass surface stress measuring device according to any one of claims 1 to 3, wherein the glass surface stress measuring device is provided between the light converting member and the light converting member.
5. 5. The glass surface stress measurement apparatus according to claim 1, wherein the light from the light source is monochromatic light having a wavelength region of 700 nm or more.
6. The glass surface stress measuring apparatus according to claim 5, wherein the light from the light source is monochromatic light having a wavelength range of 2000 nm or less.
7. 7. The glass surface stress measuring apparatus according to claim 1, wherein the light source is a light emitting diode.
8. The glass light source stress measuring apparatus according to any one of claims 1 to 6, wherein the light source is a laser.
9. The glass surface stress measuring apparatus according to any one of claims 1 to 8, wherein the tempered glass has a minimum value of an extinction coefficient at a wavelength of 550 nm to 650 nm exceeding 1.7 mm- ¹ .
10. 10. The glass surface stress measurement device according to claim 1, wherein the tempered glass is colored by containing metal ions.
11. 10. The glass surface stress measuring device according to claim 1, wherein the tempered glass is colored by depositing a metal colloid.
12. 10. The glass surface stress measuring device according to claim 1, wherein the tempered glass is colored by precipitating crystals.
13. 13. The glass surface stress measuring apparatus according to claim 1, wherein the tempered glass is chemically strengthened.
14. An image sensor for imaging the bright line array or dark line array converted by the light conversion member;
    The glass surface stress measurement device according to claim 1, further comprising an image processing device that emphasizes the bright line row or the dark line row from an image obtained by the image pickup device. .
15. Measuring means for measuring the surface stress of the tempered glass based on the bright line array or dark line array converted by the light conversion member;
    The measurement means uses a photoelastic constant of the tempered glass at substantially the same wavelength as monochromatic light having a central wavelength in a wavelength region where the extinction coefficient of the tempered glass is 4.5 mm ^-1 or less. The glass surface stress measuring device according to any one of claims 1 to 14.
16. A method for measuring the surface stress of tempered glass,
    Injecting light from a light source into the surface layer of the tempered glass;
    Propagating the light in the surface layer of the tempered glass;
    A step of emitting the light after propagation to the outside;
    Separating the emitted light into two light components that vibrate parallel and perpendicular to the glass surface;
    Converting the two separated light components into dark line lines or bright line lines, respectively;
    Measuring the surface stress of the tempered glass based on the dark line or bright line,
    Have
    The method for measuring the surface stress of glass, wherein the light separated in the separating step is monochromatic light having a central wavelength in a wavelength region in which the extinction coefficient of the tempered glass is 4.5 mm ⁻¹ or less.
17. The method for measuring the surface stress of glass according to claim 16, wherein the tempered glass is colored.
18. The surface of the glass according to claim 16 or 17, wherein the light from the light source is monochromatic light having a central wavelength in a wavelength region in which the extinction coefficient of the tempered glass is 4.5 mm ^-1 or less. Stress measurement method.
19. The monochromatic light having a wavelength region of an absorption coefficient of 4.5 mm ⁻¹ or less of the tempered glass taken out using a bandpass filter or a monochromator is incident on the surface layer of the tempered glass. The method for measuring the surface stress of glass according to any one of claims 18 to 18.
20. Monochromatic light with a wavelength range of 4.5 mm ^-1 or less of the tempered glass taken out using a bandpass filter or monochromator is separated into two light components that vibrate parallel and perpendicular to the glass surface. The method for measuring the surface stress of glass according to any one of claims 16 to 18, wherein:
21. The glass surface stress measurement method according to any one of claims 16 to 20, wherein the monochromatic light is monochromatic light having a wavelength region of 700 nm or more.
22. The method for measuring the surface stress of glass according to claim 21, wherein the light from the light source is monochromatic light in a wavelength region of 2000 nm or less.
23. The method for measuring the surface stress of glass according to any one of claims 16 to 22, wherein the tempered glass has a minimum value of an extinction coefficient at a wavelength of 550 nm to 650 nm exceeding 1.7 mm- ¹ .
24. The method for measuring the surface stress of glass according to any one of claims 16 to 23, wherein the tempered glass is colored by containing metal ions.
25. The method for measuring surface stress of glass according to any one of claims 16 to 23, wherein the tempered glass is colored by depositing a metal colloid.
26. The method for measuring the surface stress of glass according to any one of claims 16 to 23, wherein the tempered glass is colored by precipitating crystals.
27. The method for measuring surface stress of glass according to any one of claims 16 to 26, wherein the tempered glass is chemically strengthened.
28. Imaging the converted bright line or dark line;
    Performing image processing for emphasizing the bright line row or the dark line row from an image obtained by the imaging, and
    The method for measuring the surface stress of glass according to any one of claims 16 to 27, wherein the surface stress of tempered glass is measured based on the emphasized bright line array or dark line array.
29. The step of measuring the surface stress of the tempered glass,
    29. The photoelastic constant of the tempered glass at substantially the same wavelength as that of monochromatic light having a central wavelength in a wavelength region where the extinction coefficient of the tempered glass is 4.5 mm ⁻¹ or less is used. The method for measuring the surface stress of glass according to any one of the above.

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