KR102659463B1 - Evaluation device for tempered glass, evaluation method for tempered glass, manufacturing method for tempered glass, tempered glass - Google Patents

Abstract

The present tempered glass evaluation device includes a polarization phase difference variable member that varies the polarization phase difference of the laser light by more than one wavelength with respect to the wavelength of the laser light, and scattered light emitted when the laser light with the changed polarization phase difference is incident on the tempered glass. An imaging device that acquires a plurality of images by capturing images multiple times at time intervals, measures a periodic luminance change of the scattered light using the plurality of images, calculates a phase change of the luminance change, and calculates a phase change of the luminance change. It has a calculation unit that calculates a stress distribution in the depth direction from the surface of the tempered glass based on and measures a physical quantity related to the strength of the tempered glass using the plurality of images.

Description

Evaluation device for tempered glass, evaluation method for tempered glass, manufacturing method for tempered glass, tempered glass

The present invention relates to an evaluation device for tempered glass, an evaluation method for tempered glass, a method for manufacturing tempered glass, and tempered glass.

In electronic devices such as mobile phones and smartphones, glass is often used in display portions and housing main bodies. In recent years, as electronic devices have become thinner and lighter, there has been a demand for glass used in electronic devices to be thinner. The strength of glass decreases as the plate thickness becomes thinner. Therefore, in order to increase the strength of the glass, so-called chemically strengthened glass, which increases the strength by forming a surface layer (ion exchange layer) by ion exchange on the glass surface, is used, and the stress value of the surface is measured using an optical method, and correctly. It was common to check whether it had been strengthened and then ship it to the market.

As a technique for measuring the stress of the surface layer of tempered glass, for example, when the refractive index of the surface layer of tempered glass is higher than the internal refractive index, the compressive stress of the surface layer is measured non-destructively using the optical waveguide effect and the photoelastic effect. technology (hereinafter referred to as non-destructive measurement technology). In this non-destructive measurement technology, monochromatic light is incident on the surface layer of tempered glass, multiple modes are generated by the optical waveguide effect, light with a defined ray trajectory is extracted from each mode, and an image is formed into a bright line corresponding to each mode using a convex lens. Let's do it. Additionally, the number of bright lines formed into an image exists as many as the number of modes.

In addition, in this non-destructive measurement technology, the bright lines of the light extracted from the surface layer can be observed for two types of light components, the vibration direction of which is horizontal and perpendicular to the emission surface. And, using the property that light of mode 1, which has the lowest order, passes through the side closest to the surface of the surface layer, the refractive index for each light component is determined from the position of the bright line corresponding to mode 1 of the two types of light components. The stress near the surface of the tempered glass is calculated from the difference between the two types of refractive index and the photoelastic constant of the glass (for example, see Patent Document 1).

Meanwhile, based on the principles of the above-mentioned non-destructive measurement technology, the stress at the outermost surface of the glass (hereinafter referred to as surface stress value) is obtained by extrapolation from the positions of the bright lines corresponding to mode 1 and mode 2, and the stress of the surface layer is obtained by extrapolation. A method has been proposed to determine the depth of the compressive stress layer from the total number of bright lines, assuming that the refractive index distribution changes linearly (see, for example, Patent Document 3 and Non-Patent Document 1).

In addition, a method of defining the tensile stress CT inside the glass based on the surface stress value measured by the measurement technology using surface guided light and the depth of the compressive stress layer, and managing the strength of tempered glass using the CT value is proposed. (For example, see Patent Document 2). In this method, the tensile stress CT is calculated as “CT=(CS×DOL)/(t×1000-2×DOL)” (Equation 0). Here, CS is the surface stress value (MPa), DOL is the depth of the compressive stress layer (unit: ㎛), and t is the plate thickness (unit: mm).

In general, if no external force is applied, the total stress is 0. Therefore, tensile stress is generated approximately evenly so that the value obtained by integrating the stress formed by chemical strengthening in the depth direction is balanced in the central portion that has not been chemically strengthened.

In addition, the stress distribution on the surface layer of the glass is measured rather than the depth of the glass at the position where the stress distribution is bent (DOL_TP), and based on the measurement result (measurement image) of the stress distribution on the surface layer of the glass, the stress distribution is on the deeper side of the glass than DOL_TP. A method for predicting has also been proposed (for example, see Patent Document 4). However, in this method, since the actual measurement of the stress distribution on the deep side of the glass is not performed compared to DOL_TP, there is a problem that measurement reproducibility is poor.

However, chemically strengthened glass is also becoming more diverse to improve strength and performance, making it impossible to sufficiently evaluate it using conventional stress measurement methods.

For example, there is tempered glass in which stress distribution is controlled by exchanging lithium-containing glass with two types of ions, potassium and sodium, and chemically strengthened glass in which transparent crystallized glass is ion-exchanged.

In chemically strengthened glass containing lithium, a conventional optical surface stress measuring device can evaluate the stress layer near the surface where lithium is exchanged for potassium, but the internal stress layer where lithium is exchanged for sodium cannot be evaluated. , stress depth cannot be measured.

Since crystallized glass must be transparent, especially for use in display units, the crystallized glass used here is crystallized glass whose crystal grains are sufficiently smaller than the wavelength of visible light, and is transparent in the visible region. Therefore, the surface stress formed in the chemical strengthening process can be measured using a conventional optical surface stress measuring device.

However, the strength of crystallized glass largely depends not only on the stress near the chemically strengthened surface, but also on the crystal grain size, crystal grain density, grain size, etc. produced by recrystallization, and also has a large influence on the chemical strengthening process after recrystallization. Additionally, there is a possibility that the crystals produced in this recrystallization process may also change in the chemical strengthening process.

Therefore, in order to maintain the quality of diversified chemically strengthened glass, it is necessary to measure and manage the distribution of stress to the core and the crystal state in crystallized glass.

Japanese Patent Publication No. 53-136886 Japanese Patent Publication No. 2011-530470 Japanese Patent Publication No. 2016-142600 US Patent Publication No. 2016/0356760

Yogyo-Kyokai-Shi (Journal of Ceramics Association) 87 {3} 1979 Yogyo-Kyokai-Shi (Journal of Ceramics Association) 80 {4} 1972

In recent years, lithium-aluminosilicate-based glass has been attracting attention as a glass that is easy to ion exchange, has a high surface stress value in a short time in a chemical strengthening process, and can deepen the depth of the stress layer.

This glass is immersed in a high-temperature mixed molten salt of sodium nitrate and potassium nitrate to undergo chemical strengthening treatment. Since the concentration of both sodium ions and potassium ions in the molten salt is high, they ion exchange with the lithium ions in the glass. However, since sodium ions are easier to diffuse into the glass, the lithium ions in the glass and the sodium ions in the molten salt are exchanged first. .

Here, the refractive index of glass becomes lower when sodium ions are ion-exchanged with lithium ions, and becomes higher when potassium ions are ion-exchanged with lithium ions or sodium ions. That is, compared to the non-ion-exchanged portion of the glass, the ion-exchanged region near the glass surface has a high potassium ion concentration, and the deeper ion-exchanged region has a higher sodium ion concentration. Therefore, the refractive index near the outermost surface of ion-exchanged glass decreases with depth, but has the characteristic that the refractive index increases with depth from a certain depth to the non-ion-exchanged region.

Therefore, in the stress measurement device using surface guided light described in the background technology, the stress distribution in the deep part cannot be measured using only the stress value or stress distribution at the outermost surface, and the depth of the stress layer, CT value, and overall stress distribution cannot be measured. The stress distribution was unknown. As a result, development to find appropriate chemical strengthening conditions could not be carried out, and quality control of manufacturing could not be carried out.

In addition, when aluminosilicate glass or soda glass is chemically strengthened after wind cooling, the stress distribution or stress value of the chemically strengthened part can be measured using a stress measuring device using surface guided light as described in the background technology. However, the portion that has not been chemically strengthened but has only been strengthened by wind cooling has a small change in refractive index and cannot be measured using a stress measuring device using guided light on the surface described in the background technology. As a result, the depth of the stress layer, CT value, and overall stress distribution were unknown. As a result, development to find appropriate chemical strengthening conditions could not be carried out, and quality control of manufacturing could not be carried out.

On the other hand, crystallized glass has higher strength than general glass. Therefore, chemically strengthened crystallized glass can achieve higher strength than ordinary tempered glass. However, in the crystallized glass, physical performance such as strength is greatly influenced by the crystal state (grain size, grain density, crystal species), etc. Therefore, in crystallized glass, it is necessary to measure physical quantities related to the strength of the crystallized glass along with the stress distribution due to chemical strengthening.

The present invention has been made in consideration of the above points, and its purpose is to provide an evaluation device for tempered glass that can measure the stress distribution of tempered glass and the physical quantity related to the strength of tempered glass.

The present tempered glass evaluation device includes a polarization phase difference variable member that varies the polarization phase difference of the laser light by more than one wavelength with respect to the wavelength of the laser light, and scattered light emitted when the laser light with the changed polarization phase difference is incident on the tempered glass. An imaging device that acquires a plurality of images by capturing images multiple times at time intervals, measures a periodic luminance change of the scattered light using the plurality of images, calculates a phase change of the luminance change, and calculates a phase change of the luminance change. It is a requirement to have a calculation unit that calculates the stress distribution in the depth direction from the surface of the tempered glass based on and measures a physical quantity related to the strength of the tempered glass using the plurality of images.

According to the disclosed technology, it is possible to provide an evaluation device for tempered glass that can measure the stress distribution of tempered glass and can also measure a physical quantity related to the strength of tempered glass.

1 is a diagram illustrating an evaluation device according to a first embodiment.
FIG. 2 is a view of the evaluation device according to the first embodiment as seen from the H direction in FIG. 1.
Figure 3 is a diagram illustrating the relationship between the applied voltage and polarization phase difference of the liquid crystal device.
FIG. 4 is a diagram illustrating a circuit that generates a driving voltage in a liquid crystal device whose polarization phase difference changes linearly over time.
FIG. 5 is a diagram illustrating a scattered light image of laser light L formed on an imaging device at a certain moment.
FIG. 6 is a diagram illustrating temporal changes in the luminance of scattered light at points B and C in FIG. 5.
Figure 7 is a diagram illustrating the phase of scattering light change according to glass depth.
FIG. 8 is a diagram illustrating the stress distribution obtained from Equation 1 based on the phase data of the scattered light change in FIG. 7.
Figure 9 is a diagram illustrating actual scattered light images at different times t1 and t2.
Fig. 10 is a diagram showing an example of an undesirable design of the incident surface of the laser light L in tempered glass.
Fig. 11 is a diagram showing a preferred design example of the incident surface of the laser light L in tempered glass.
FIG. 12 is a diagram illustrating functional blocks of the calculation unit 70 of the evaluation device 1.
Fig. 13 is a flowchart (Part 1) illustrating an evaluation method using the evaluation device 1.
Fig. 14 is a flowchart (Part 2) illustrating the evaluation method using the evaluation device 1.
FIG. 15 is an image of scattered light at a certain time obtained by the imaging device 60.
FIG. 16 is a graph of temporal changes in the average scattered light luminance in area E in FIG. 15(a).
Fig. 17 is a diagram illustrating the relationship between the scattered light luminance amplitude value As and the depth of the glass.
Fig. 18 is a diagram illustrating an evaluation device according to Modification 1 of the first embodiment.
Fig. 19 is a diagram illustrating an evaluation device according to Modification 2 of the first embodiment.
Fig. 20 is a diagram illustrating an evaluation device according to Modification 3 of the first embodiment.
Fig. 21 is a diagram illustrating an evaluation device according to modification example 4 of the first embodiment.
Figure 22 is an explanatory diagram of a polarization phase difference variable member using the photoelastic effect.
Fig. 23 is a diagram illustrating an evaluation device according to the second embodiment.
Figure 24 is a diagram showing the stress distribution measured by the evaluation devices 1 and 2 in the same graph.
25 is a flowchart illustrating an evaluation method using the evaluation device 2.
FIG. 26 is a diagram illustrating functional blocks of the calculation unit 75 of the evaluation device 2.
Figure 27 is a diagram illustrating the stress distribution in the depth direction of tempered glass.
Figure 28 is a flowchart (part 1) for deriving characteristic values based on stress distribution.
Figure 29 is a diagram showing an example of deriving each characteristic value from the measured stress distribution.
Figure 30 is a flowchart (part 2) for deriving characteristic values based on stress distribution.
Figure 31 is a diagram (part 1) showing another example of deriving each characteristic value from the measured stress distribution.
Figure 32 is a flowchart (part 3) for deriving characteristic values based on stress distribution.
Figure 33 is a diagram (Part 2) showing another example of deriving each characteristic value from the measured stress distribution.
Figure 34 is a diagram showing an example of a flowchart of quality judgment using each characteristic value obtained from measurement of stress distribution.
Figure 35 is a diagram showing another example of a flowchart of quality judgment using each characteristic value obtained from measurement of stress distribution.
Figure 36 is an example (Part 1) of a flowchart of quality judgment when strengthening lithium-containing glass twice or more.
Figure 37 is an example (Part 2) of a flowchart of quality judgment when strengthening lithium-containing glass twice or more.
Figure 38 is an example of a composite result of the stress distribution on the surface layer side of the glass and the stress distribution on the deep layer side of the glass.
Figure 39 shows the stress distribution obtained in Comparative Example 1 and Examples 1 to 3.
Fig. 40 is a diagram illustrating an evaluation device according to the third embodiment.
FIG. 41 is a diagram illustrating a scattered light image of laser light L traveling at the interface of a light supply member and tempered glass.
Figure 42 is a diagram illustrating a structural portion for placing liquid between a light supply member and tempered glass.
FIG. 43 is a diagram showing a second example of a structural portion for placing a liquid between a light supply member and tempered glass.
FIG. 44 is a diagram showing a third example of a structural portion for placing a liquid between a light supply member and tempered glass.
FIG. 45 is a diagram showing a fourth example of a structural portion for placing a liquid between a light supply member and tempered glass.
FIG. 46 is a diagram showing a fifth example of a structural portion for placing a liquid between a light supply member and tempered glass.
FIG. 47 is a diagram showing a sixth example of a structural portion for placing a liquid between a light supply member and tempered glass.
Figure 48 is a diagram showing a seventh example of a structural portion for placing a liquid between a light supply member and tempered glass.
Figure 49 is a diagram explaining that laser light L is incident on tempered glass.
FIG. 50 is a diagram explaining an image of a laser trace taken from the imaging element position in FIG. 49.
FIG. 51 is a diagram explaining definitions of the angle and length of the laser light in the light supply member or tempered glass of FIG. 49.
Figure 52 is a top view, front view, and side view of Figure 51.
Figure 53 is a conceptual diagram of laser light traveling through a light supply member and tempered glass.
Figure 54 is a conceptual diagram of laser light traveling through tempered glass.
Figure 55 is an example of a flowchart for calculating the incident complement angle Ψ.
Figure 56 is an example of a flowchart for determining the refractive index ng of tempered glass.
Figure 57 is another example of a flowchart for calculating the incident complement angle Ψ.
Figure 58 is an example of a flowchart for calculating θL where the surface through which the laser light passes and the observation surface do not change.
Figure 59 is a diagram illustrating the stress distribution in the depth direction of tempered glass.
Figure 60 is a diagram illustrating an evaluation device equipped with a glass thickness measuring device.

Hereinafter, modes for carrying out the invention will be described with reference to the drawings. In each drawing, the same reference numerals are assigned to the same components, and redundant descriptions may be omitted.

<First embodiment>

1 is a diagram illustrating an evaluation device according to a first embodiment. As shown in FIG. 1, the evaluation device 1 includes a laser light source 10, a polarizing member 20, a polarization phase difference variable member 30, a light supply member 40, and a light conversion member ( 50), an imaging element 60, a calculation unit 70, and a light wavelength selection member 80.

Reference numeral 200 denotes tempered glass that is the object to be measured. The tempered glass 200 is glass that has been strengthened by, for example, a chemical strengthening method or an air cooling strengthening method. The tempered glass referred to herein also includes crystallized glass that has undergone strengthening treatment. Here, crystallized glass is glass produced through a crystallization process. In other words, it is glass with intentionally precipitated crystals. In this application, crystallized glass to which strengthening treatment has been performed may be referred to as strengthened crystallized glass as needed.

The laser light source 10 is arranged to make the laser light L incident on the surface layer of the tempered glass 200 from the light supply member 40, and a polarization phase difference is formed between the laser light source 10 and the light supply member 40. A variable member 30 is inserted.

As the laser light source 10, for example, a semiconductor laser, helium neon laser, or argon laser can be used. Semiconductor lasers usually have polarization, and semiconductor lasers with wavelengths such as 405 nm, 520 nm, 630 nm, and 850 nm have been put into practical use. The shorter the wavelength of the laser light, the narrower the beam diameter, and the higher the spatial resolution. Additionally, it is preferable that the shorter the wavelength of the laser light, the smaller the noise tends to be. Additionally, the laser light needs to penetrate the measurement target.

In order to increase the resolution in the depth direction of the tempered glass 200, it is preferable that the position of the minimum beam diameter of the laser light is within the ion exchange layer of the tempered glass 200, and the minimum beam diameter is 20 μm or less. It is more preferable to set the position of the minimum beam diameter of the laser light to the surface 210 of the tempered glass 200. Additionally, since the beam diameter of the laser light becomes the resolution in the depth direction, it is necessary to set the beam diameter to be less than the required resolution in the depth direction. Here, the beam diameter means the width of 1/e ² (about 13.5%) when the luminance at the center of the beam is maximum, and when the beam shape is elliptical or sheet-like, the beam diameter means the minimum width. However, in this case, the minimum width of the beam diameter needs to be oriented in the glass depth direction.

Since the cross-sectional shape of the beam emitted from the semiconductor laser is usually oval, spatial resolution can be increased and measurement accuracy can be improved by shaping the beam into a circle using a beam shaping member. In addition, the power distribution within the beam shape of the beam emitted from the semiconductor laser is a Gaussian distribution, but measurement accuracy can be improved by shaping the power distribution into a constant distribution within the beam shape, such as a top hat distribution, using an output distribution shaping member.

The beam shaping member and the power distribution shaping member are inserted between the laser light source 10 and the polarization phase difference variable member 30, for example. Examples of beam shaping members include cylindrical lenses, anamorphic prisms, and apertures. In addition, examples of power distribution shaping members include aspherical lenses, DOEs (Diffractive Optical Elements), and the like.

The polarizing member 20 is inserted between the laser light source 10 and the polarization phase difference variable member 30 as needed. Specifically, when the laser light L emitted from the laser light source 10 is not polarized light, the polarization member 20 is inserted between the laser light source 10 and the polarization phase difference variable member 30. When the laser light L emitted from the laser light source 10 is polarized light, the polarizing member 20 may or may not be inserted. Additionally, the laser light source 10 and the polarizing member 20 are installed so that the polarization plane of the laser light L is 45° with respect to the surface 210 of the tempered glass 200. As the polarizing member 20, for example, a polarizing plate arranged in a rotatable state can be used, but another member having a similar function may be used.

The light supply member 40 is placed in optical contact with the surface 210 of the tempered glass 200, which is the object to be measured. The light supply member 40 has a function of making light from the laser light source 10 incident on the tempered glass 200 . As the light supply member 40, for example, a prism made of optical glass can be used. In this case, since the light ray is optically incident through a prism on the surface 210 of the tempered glass 200, the refractive index of the prism needs to be approximately the same (within ±0.2) as the refractive index of the tempered glass 200. there is.

A liquid having a refractive index substantially equal to that of the tempered glass 200 may be placed between the light supply member 40 and the tempered glass 200. As a result, the laser light L can be efficiently incident on the tempered glass 200. This will be explained in detail in the third embodiment.

The laser light L passing through the tempered glass 200 generates a trace amount of scattered light L _S. The luminance of the scattered light L _S changes with the polarization phase difference of the scattered portion of the laser light L. Additionally, the laser light source 10 is installed so that the polarization direction of the laser light L is θ _s2 in FIG. 2 with respect to the surface 210 of the tempered glass 200 at 45° (within ±5°). Therefore, birefringence occurs due to the photoelastic effect of the stress applied in the in-plane direction of the tempered glass 200, and as the laser light L travels in the tempered glass, the polarization phase difference also changes, and with the change, the scattered light L The luminance of _S also changes. Additionally, polarization phase difference is a phase difference (retardation) generated by birefringence.

In addition, θ _s1 of the laser light L is set to 10° or more and 30° or less with respect to the surface 210 of the tempered glass. This is because if the angle is less than 10°, the laser light propagates on the glass surface due to the optical waveguide effect, making it impossible to obtain information inside the glass. Conversely, if it exceeds 30°, the resolution of the depth inside the glass relative to the laser optical path length becomes low, making it undesirable as a measurement method. Therefore, preferably θ _s1 = 15° ± 5°.

Next, the imaging element 60 will be explained using FIG. 2. FIG. 2 is a view of the evaluation device according to the first embodiment as seen from the H direction in FIG. 1, and is a view showing the positional relationship of the imaging element 60. Since the polarized light of the laser light L is incident on the surface 210 of the tempered glass 200 at an angle of 45°, the scattered light L _S is also emitted at an angle of 45° with respect to the surface 210 of the tempered glass 200. Therefore, in order to capture the scattered light L _S radiated at an angle of 45° with respect to the surface of the tempered glass, the imaging element 60 is positioned at an angle of 45° with respect to the surface 210 of the tempered glass 200 in FIG. 2 . It is installed in this direction. That is, in FIG. 2, θ _s2 = 45°.

Additionally, a light conversion member 50 is inserted between the imaging device 60 and the laser beam L so as to form an image of the scattered light L _S by the laser beam L on the imaging device 60 . As the light conversion member 50, for example, a convex lens made of glass or a lens combining a plurality of convex lenses or concave lenses can be used. At this time, it is preferable that the numerical aperture (NA) of the lens is large because noise is reduced.

In addition, with respect to a lens combining a plurality of lenses, by using a telecentric lens whose main ray is parallel to the optical axis, among the scattered light scattered in all directions from the laser light L, mainly in the direction 45° with respect to the glass surface of the tempered glass 200 An image can be formed only with light scattered in the direction (direction of the imaging device). As a result, unnecessary light such as diffuse reflection from the glass surface can be reduced.

Additionally, a light wavelength selection member 80 is inserted between the laser light L and the imaging element 60 to remove light unnecessary for stress measurement. The light wavelength selection member 80 does not transmit 50% or more of the light having a wavelength other than the wavelength of the laser light L, and preferably does not transmit 90% or more of the light having a wavelength other than the wavelength of the laser light L. Additionally, it is desirable that the width of the wavelength passing through the light wavelength selection member 80 is about 10 nm or less. By inserting the light wavelength selection member 80, Raman scattered light, fluorescence light, or extraneous light that is unnecessary for stress measurement generated from the laser light L can be removed, and only the scattered light L _S necessary for stress measurement can be focused on the imaging device 60. . As the light wavelength selection member 80, for example, a band-pass filter or a short-pass filter made of multiple dielectric films can be used.

As the imaging element 60, for example, a CCD (Charge Coupled Device) element or a CMOS (Complementary Metal Oxide Semiconductor) sensor element can be used. Although not shown in FIGS. 1 and 2, a CCD element or a CMOS sensor element includes a control circuit that controls the element and extracts an electrical signal of an image from the element, a digital image data generation circuit that converts the electrical signal into digital image data, It is connected to a digital recording device that records multiple copies of digital image data. Additionally, a digital image data generation circuit and a digital recording device are connected to the calculation unit 70.

The calculation unit 70 has a function of importing image data from the imaging device 60, a digital image data generation circuit connected to the imaging device 60, or a digital recording device, and performing image processing or numerical calculations. I'm doing it. The calculation unit 70 may be configured to have functions other than this (for example, a function to control the light quantity or exposure time of the laser light source 10, etc.). The calculation unit 70 includes, for example, a Central Processing Unit (CPU), Read Only Memory (ROM), Random Access Memory (RAM), and main memory.

In this case, various functions of the calculation unit 70 can be realized by a program recorded in ROM or the like being read into main memory and executed by the CPU. The CPU of the calculation unit 70 can read or store data from RAM as needed. However, part or all of the calculation unit 70 may be realized only by hardware. Additionally, the calculation unit 70 may physically have a plurality of devices, etc. As the calculation unit 70, for example, a personal computer can be used. Additionally, the calculation unit 70 may have the functions of a digital image data generation circuit and a digital recording device.

The polarization phase difference variable member 30 changes the polarization phase difference when incident on the tempered glass 200 over time. The polarization phase difference that changes is one or more times the wavelength λ of the laser light. The polarization phase difference must be uniform with respect to the wavefront of the laser light L. For example, in a crystal wedge, the wavefront of the laser light is not uniform because the polarization phase difference is not uniform in the direction of the inclined surface of the wedge. Therefore, it is not desirable to use a crystal wedge as the polarization phase difference variable member 30.

Examples of the polarization phase difference variable member 30 that is uniform to the wavefront of the laser light and can electrically vary the polarization phase difference by 1λ or more include a liquid crystal element. The liquid crystal device can vary the polarization phase difference depending on the voltage applied to the device. For example, when the wavelength of the laser light is 630 nm, 3 to 6 wavelengths can be varied. In a liquid crystal device, the maximum value of polarization phase difference that can be varied with an applied voltage is determined by the size of the cell gap.

Since a typical liquid crystal device has a cell gap of several μm, the maximum polarization phase difference is about 1/2λ (several 100 nm). Additionally, in displays using liquid crystal, etc., no further changes are required. On the other hand, the liquid crystal element used in this embodiment needs to vary the polarization phase difference to about 2000 nm, which is about 3 times that of 630 nm, when the wavelength of the laser light is, for example, 630 nm, and a cell of 20 to 50 μm A gap is needed.

The voltage applied to the liquid crystal device and the polarization phase difference are not proportional. As an example, the relationship between the applied voltage and the polarization phase difference of a liquid crystal element with a cell gap of 30 μm is shown in Figure 3. In Figure 3, the vertical axis represents the polarization phase difference (number of wavelengths for a wavelength of 630 nm), and the horizontal axis represents the voltage applied to the liquid crystal element (expressed in logarithms).

The voltage applied to the liquid crystal device is 0V to 10V, and the polarization phase difference of about 8λ (5000nm) can be varied. However, in liquid crystal devices, the orientation of the liquid crystal is generally not stable at low voltages from 0 V to 1 V, and the polarization phase difference changes due to temperature changes, etc. Additionally, when the voltage applied to the liquid crystal element is 5V or more, there is little change in polarization phase difference with respect to the change in voltage. In the case of this liquid crystal device, by using it at an applied voltage of 1.5V to 5V, the polarization phase difference can be stably varied from 4λ to 1λ, that is, about 3λ.

When a liquid crystal element is used as the polarization phase difference variable member 30, the polarization phase difference variable member 30 is connected to a liquid crystal control circuit that controls the liquid crystal, and is controlled in synchronization with the imaging element 60. At this time, it is necessary to linearly vary the polarization phase difference in time and synchronize it with the timing of imaging by the imaging device 60.

Figure 3 is a diagram illustrating the relationship between the applied voltage of the liquid crystal device and the polarization phase difference. As shown in FIG. 3, the applied voltage and polarization phase difference of the liquid crystal device do not change linearly. Therefore, it is necessary to generate a signal whose polarization phase difference changes linearly within a certain period of time and apply it as a driving voltage to the liquid crystal element.

FIG. 4 is a diagram illustrating a circuit that generates a driving voltage in a liquid crystal device whose polarization phase difference changes linearly over time.

In FIG. 4, the digital data storage circuit 301 is provided with a voltage value corresponding to the polarization phase difference for changing the polarization phase difference at regular intervals based on the applied voltage of the liquid crystal element to be used and the data of previously measuring the polarization phase difference. This is recorded in address order as digital data in the required range of polarization phase difference change. Table 1 illustrates some of the digital data recorded in the digital data storage circuit 301. The voltage column in Table 1 is digital data to be recorded, and is the voltage value for every 10 nm change in polarization phase difference.

The clock signal generation circuit 302 uses a crystal oscillator or the like to generate a clock signal with a constant frequency. The clock signal generated by the clock signal generation circuit 302 is input to the digital data storage circuit 301 and the DA converter 303.

The DA converter 303 is a circuit that converts digital data from the digital data storage circuit 301 into an analog signal. In accordance with the clock signal generated by the clock signal generation circuit 302, digital data of the sequentially stored voltage values are read from the digital data storage circuit 301 and sent to the DA converter 303.

The DA converter 303 converts digital data of voltage values read at regular time intervals into analog voltage. The analog voltage output from the DA converter 303 is applied to the liquid crystal element used as the polarization phase difference variable member 30 through the voltage amplification circuit 304.

In addition, although not shown in FIG. 4, the driving circuit of this liquid crystal element is synchronized with the circuit that controls the imaging element 60 in FIG. 2, and with the start of application of the driving voltage to the liquid crystal element, the imaging element ( At 60), temporally continuous imaging begins.

FIG. 5 is a diagram illustrating a scattered light image of laser light L formed on an imaging device at a certain moment. In FIG. 5 , the depth from the surface 210 of the tempered glass 200 increases as it goes upward. In FIG. 5 , point A is the surface 210 of the tempered glass 200, and since the scattered light on the surface 210 of the tempered glass 200 is strong, the scattered light image spreads in an elliptical shape.

Since strong compressive stress is applied to the surface of the tempered glass 200, the polarization phase difference of the laser light L changes with depth due to birefringence due to the photoelastic effect. Therefore, the scattered light luminance of the laser light L also changes with depth. In addition, the principle by which the brightness of scattered light of laser light changes depending on the internal stress of tempered glass is explained, for example, in Yogyo-Kyokai-Shi (Journal of the Ceramic Association) 80 {4} 1972.

By using the polarization phase difference variable member 30, the polarization phase difference of the laser light L before entering the tempered glass 200 can be continuously changed temporally. As a result, at each point of the scattered light image in FIG. 5, the scattered light luminance changes according to the polarization phase difference changed by the polarization phase difference variable member 30.

FIG. 6 is a diagram illustrating temporal changes in the luminance of scattered light (scattered light luminance) at points B and C in FIG. 5. The temporal change in the brightness of the scattered light changes periodically at a period of the wavelength λ of the laser light in accordance with the polarization phase difference changed by the polarization phase difference variable member 30. For example, in Figure 6, at point B and point C, the period of change in scattered light luminance is the same, but the phase is different. This is because when the laser light L progresses from point B to point C, the polarization phase difference further changes due to birefringence due to stress in the tempered glass 200. The phase difference δ between point B and point C is the polarization phase difference changed when the laser light L progresses from point B to point C, expressed as a path difference. If q is the wavelength of the laser light and λ is, δ = q/λ.

Considering locally, the phase F of the periodic change in scattered light luminance accompanying the change in the temporal polarization phase difference of the polarization phase difference variable member 30 at an arbitrary point S on the laser light L is referred to as the laser light L. With respect to the function F(s) expressed at the position s, the differential value dF/ds with respect to s is the amount of birefringence generated by the in-plane stress of the tempered glass 200. From the photoelastic constant C of the tempered glass 200 and dF/ds, the stress σ in the in-plane direction of the tempered glass 200 at point S can be calculated using Equation 1 below (Equation 1).

In this specification, since the laser light L is incident on the glass at an angle, when calculating the stress distribution with respect to the depth in the vertical direction from the glass surface, conversion from point s to the depth direction is required, and Equation 8 (described later) It is expressed as Equation 8).

Meanwhile, the polarization phase difference variable member 30 continuously changes the polarization phase difference by one wavelength or more within a certain period of time. Within that time, the imaging element 60 records scattered light images from a plurality of temporally continuous laser beams L. Then, the temporal change in luminance at each point of the continuously photographed scattered light image is measured.

The change in scattered light at each point of this scattered light is periodic, and the period is constant regardless of location. So, the period T is measured from the change in the brightness of scattered light at a certain point. Alternatively, the average of the periods at a plurality of points may be defined as the period T.

In the polarization phase difference variable member 30, since the polarization phase difference is changed by one wavelength or more (one cycle or more), the scattered light luminance is also changed by one cycle or more. Therefore, the period T can be measured from the difference between a plurality of peaks or valleys, or the difference in time passing the midpoint of the amplitude. Additionally, from data of one cycle or less, it is impossible in principle to know one cycle.

For data on periodic changes in scattered light at a certain point, the phase F at that point can be accurately obtained using the trigonometric least squares method or Fourier integration based on the period T determined above.

In the least squares method or Fourier integration of trigonometric functions in a previously known period T, only the phase component in the known period T is extracted, and noise in other periods can be removed. Additionally, the removal ability increases the longer the temporal change in data is. Usually, the luminance of scattered light is weak and the amount of phase that actually changes is small, so it is necessary to measure data by varying the polarization phase difference by several λ.

If data on the temporal change of the scattered light at each point of the scattered light along the laser light L on the image captured by the imaging device 60 are measured, and the phase F is obtained for each by the same method as above, the laser light L According to , the phase F of the scattered light luminance can be obtained. Figure 7 is an example of the phase of scattering light change depending on glass depth.

In the phase F of the scattered light luminance along the laser light L, the differential value at the coordinate on the laser light L can be calculated, and the stress value at the coordinate s on the laser light L can be obtained using Equation 1. Additionally, if the coordinate s is converted to the distance from the glass surface, the stress value for the depth from the surface of the tempered glass can be calculated. FIG. 8 is an example of calculating the stress distribution from Equation 1 based on the phase data of the scattered light change in FIG. 7.

Figure 9 is an example of actual scattered light images at different times t1 and t2. Point A in Figure 9 is the surface of tempered glass, and surface scattered light is reflected due to the roughness of the surface of tempered glass. The center of this surface scattered light image corresponds to the surface of the tempered glass.

In Figure 9, it can be seen that the luminance of the scattered light image of the laser light is different at each point, and also that the luminance distribution at time t2 is not the same as the luminance distribution at time t1 even at the same point. This is because the phase of the periodic scattering light luminance change is shifted.

In the evaluation device 1, the incident surface of the laser light L is preferably inclined at 45° with respect to the surface 210 of the tempered glass 200. This will be explained with reference to FIGS. 10 and 11.

Fig. 10 is a diagram showing an example of an undesirable design of the incident surface of the laser light L in tempered glass. In Figure 10, the incident surface 250 of the laser light L in the tempered glass 200 is perpendicular to the surface 210 of the tempered glass.

FIG. 10(b) is a view seen from direction H of FIG. 10(a). As shown in FIG. 10(b), the imaging element 60 is installed at an angle of 45° with respect to the surface 210 of the tempered glass 200, and the laser beam L is observed from an angle of 45°. . In the case of Fig. 10, if the distances from two other points, point A and point B, on the laser beam L to the imaging element 60 are referred to as distance A and distance B, the distances are different. In other words, point A and point B cannot be focused at the same time, and the scattered light image of the laser light L in the required area cannot be acquired as a good image.

Fig. 11 is a diagram showing a preferred design example of the incident surface of the laser light L in tempered glass. In FIG. 11 , the incident surface 250 of the laser light L in the tempered glass 200 is inclined at 45° with respect to the surface 210 of the tempered glass 200.

FIG. 11(b) is a view seen from direction H of FIG. 11(a). As shown in FIG. 11 (b), the imaging element 60 is installed at an angle of 45° with respect to the surface 210 of the tempered glass 200, but the incident surface (which is the surface through which the laser light L passes) 250) is also tilted at 45°. Therefore, the distance (distance A and distance B) to the imaging element 60 is the same at any point on the laser beam L, and the scattered light image of the laser beam L in the required area can be acquired as a good image.

In particular, when using laser light with a minimum beam diameter of 20 ㎛ or less, the depth of focus is shallow, at most about 10 ㎛. Therefore, the incident surface 250 of the laser beam L in the tempered glass 200 is inclined at 45° with respect to the surface 210 of the tempered glass 200, so that the imaging element 60 is present at any point on the laser beam L. Keeping the distance to is the same is very important in acquiring good images.

FIG. 12 is a diagram illustrating functional blocks of the calculation unit 70 of the evaluation device 1. As shown in FIG. 12, the calculation unit 70 has a luminance change measurement means 701, a phase change calculation means 702, a stress distribution calculation means 703, and a physical quantity measurement means 704. .

The evaluation device 1 can measure the stress distribution of the tempered glass using the luminance change measurement means 701, the phase change calculation means 702, and the stress distribution calculation means 703 of the calculation unit 70. In addition, the physical quantity measuring means 704 is a part that has the function of measuring a physical quantity related to the strength of the tempered glass. When only measuring the stress distribution of the tempered glass, the physical quantity measuring means 704 does not need to be used.

(Measurement flow 1: Measurement of stress distribution in tempered glass)

FIG. 13 is a flowchart (part 1) illustrating an evaluation method using the evaluation device 1, and is a flowchart illustrating a method of measuring the stress distribution of tempered glass in the evaluation device 1. Referring to FIGS. 12 and 13 , the flow of measurement of the stress distribution of tempered glass in the evaluation device 1 will be described.

In addition, the measurement shown in FIG. 13 can be performed, for example, after the process of producing tempered glass by subjecting a plate to strengthening treatment. In addition, the measurement shown in FIG. 13 may be performed after the process of subjecting a plate to a crystallization treatment to produce crystallized glass and further subjecting the produced crystallized glass to a strengthening treatment to produce strengthened crystallized glass.

First, in step S401, the polarization phase difference of the laser light from the polarized laser light source 10 or the polarized laser light source 10 is temporally continuously adjusted to the wavelength of the laser light by the polarization phase difference variable member 30. It varies by more than 1 wavelength (polarization phase difference variable process).

Next, in step S402, the laser light with the variable polarization phase difference is incident diagonally on the surface 210 of the tempered glass 200, which is the object to be measured, through the light supply member 40 (light supply process).

Next, in step S403, the imaging device 60 captures the scattered light caused by the laser beam with the variable polarization phase difference traveling in the tempered glass 200 multiple times at predetermined time intervals to acquire multiple images. (Imaging process).

Next, in step S404, the luminance change measurement means 701 of the calculation unit 70 uses a plurality of temporally spaced images of the scattered light obtained in the imaging process to measure the polarization phase difference varied by the polarization phase difference variable process. Measure the periodic luminance change of scattered light accompanying temporal changes (luminance change measurement process).

Next, in step S405, the phase change calculation means 702 of the calculation unit 70 calculates the phase change of the periodic luminance change of the scattered light along the laser light incident on the tempered glass 200 (phase change calculation) process).

Next, in step S406, the stress distribution calculation means 703 of the calculation unit 70 calculates the temperature of the tempered glass 200 based on the phase change of the periodic luminance change of the scattered light along the laser light incident on the tempered glass 200. The stress distribution in the depth direction from the surface 210 of 200 is calculated (stress distribution calculation process). Additionally, the calculated stress distribution may be displayed on a display device (liquid crystal display, etc.).

(Measurement flow 2: Measurement of stress distribution in tempered glass and measurement of physical quantities related to strength)

The evaluation device 1 determines the stress distribution of the tempered glass by the luminance change measurement means 701, the phase change calculation means 702, the stress distribution calculation means 703, and the physical quantity measurement means 704 of the calculation unit 70. In addition to measuring, it is possible to measure physical quantities related to the strength of tempered glass.

FIG. 14 is a flowchart (part 2) illustrating an evaluation method using the evaluation device 1, a method of measuring the stress distribution of tempered glass in the evaluation device 1, and a measurement of a physical quantity related to the strength of the tempered glass. This is a flowchart illustrating the method. Referring to FIGS. 12 and 14 , the flow for measuring the stress distribution of tempered glass in the evaluation device 1 and measuring the physical quantity related to the strength of tempered glass will be described.

In addition, the measurement shown in FIG. 14 can be performed, for example, after the process of producing crystallized glass by subjecting a plate to a crystallization treatment and then performing a strengthening treatment on the produced crystallized glass to produce strengthened crystallized glass.

First, steps S401 to S403 are executed as in the case of FIG. 13. Then, step S414 is executed in parallel with steps S404 to S406. In step S414, the physical quantity measurement means 704 of the calculation unit 70 measures a physical quantity related to the strength of the tempered glass using a plurality of temporally spaced images of the scattered light obtained in the imaging process of step S403 ( physical quantity measurement process). Step S414 can be executed approximately simultaneously with steps S404 to S406. Additionally, the measured physical quantity may be displayed on a display device (liquid crystal display, etc.).

Here, “physical quantities related to the strength of tempered glass” refers to, for example, physical quantities such as refractive index, crystallization rate, crystal grain size, crystal grain density, haze, and the amount of defects and impurities in the glass, and the parameters necessary to determine these physical quantities ( (scattered light luminance amplitude value, average scattered light luminance, scattered light luminance dispersion value, etc.). That is, the physical quantity measuring means 704 may measure only the scattered light luminance amplitude value or the average scattered light luminance without directly measuring physical quantities such as the crystallization rate. Even in this case, the strength of the tempered glass can be estimated from the measurement results of the physical quantity measuring means 704.

Below, the measurement of physical quantities related to the strength of tempered glass will be explained in more detail.

(Example 1 of measurement of physical quantity related to the strength of tempered glass)

FIG. 15(a) is an image of scattered light at a certain time obtained by the imaging device 60, and FIG. 15(b) is an enlarged view of area E in FIG. 15(a). Additionally, FIG. 16 is a graph of the temporal change in the average scattered light luminance in area E in FIG. 15(a). When the phase difference of the laser light L incident by the polarization phase difference variable member 30 changes, the scattered light luminance also changes along with it. Therefore, in the graph of the temporal change in the scattered light luminance shown in FIG. 16, the scattered light luminance changes periodically accompanying the change in phase difference of the laser light. The amplitude value of the change in the scattered light luminance is called the scattered light luminance amplitude value As, and the average value of the change in the scattered light luminance is called the average scattered light luminance Is.

Usually, scattered light includes light scattered by several scattering mechanisms. Scattered light whose wavelength is the same as that of the incident light has different scattering properties depending on the relationship between the size of the scattering particle and the wavelength. Let the diameter of the scattering particles be D, the wavelength of the incident light be λ, and if the wavelength λ of the incident light is kept constant, if the scattering particles are sufficiently small, they are scattered by the scattering mechanism of Rayleigh scattering, and the position D = λ × 1/10. From , the scattering mechanism begins to change to micro-scattering, and at D ≥ λ, it completely becomes non-scattering.

The size of the haze of crystallized glass is determined by the crystal grain size, crystal grain density, and the difference in refractive index between the crystals and the glass phase. The smaller the difference in refractive index between the crystal and the glass phase, the smaller the haze. However, it is difficult to completely match the refractive index of the crystal and the glass phase, and it is common for a refractive index difference of about 0.05 to 0.50 to exist. For example, when the difference in refractive index between the crystal and the glass phase is about 0.1, in order for the crystal grain size (diameter of the crystal grain) of the strengthened crystallized glass to be transparent to visible light, the crystal grain size of the strengthened crystallized glass must be sufficiently smaller than the wavelength of visible light of about 600 nm. , is controlled from 10 nm to 100 nm. Therefore, in most cases, the Rayleigh scattering mechanism is dominant, but at 100 nm, which is the maximum crystal grain size, the influence of the non-scattering mechanism also occurs. In addition, the luminance of scattered light is highly proportional to the diameter of the scattering particles for both Rayleigh scattering and non-scattering, and is proportional to the density of the scattering particles. In Rayleigh scattering, it is proportional to the 6th power of the scattering particle diameter, in Mi scattering it is proportional to the 2nd power, and in the area where the Rayleigh scattering is changed to the Mi scattering mechanism, it is thought to be somewhere in between. That is, in Rayleigh scattering and Mie scattering, where the wavelength does not change with the incident light, the larger the scattering particle diameter and the higher the density, the higher the scattered light luminance.

Additionally, scattering in which the wavelength of scattered light is different from the wavelength of incident light includes fluorescence scattering and Raman scattering. Normally, fluorescence scattering occurs due to impurities or defects in the glass, and Raman scattering occurs due to composition or bonding state.

Among these several scattering mechanisms, in Rayleigh scattering, the brightness of the scattered light varies depending on the polarization state of the incident light. In the measurement of stress, as the laser light L travels through the glass due to birefringence due to the photoelastic effect of the internal stress, the polarization state changes, and the scattered light luminance changes accordingly. This is used in the principle of the evaluation device 1. On the other hand, in other scattering mechanisms such as micro scattering, fluorescence scattering, and Raman scattering, the scattered light luminance generally does not depend on the polarization state of the incident light. Therefore, fine scattering, fluorescence scattering, and Raman scattering are not used in the principles of the evaluation device 1.

In the evaluation device 1, a light wavelength selection member 80 that transmits only the vicinity of the wavelength of the laser light is provided between the light supply member 40 and the imaging element 60. Since the width of the wavelength passing through the optical wavelength selection member 80 is very narrow, about 10 nm or less, only scattered light with a wavelength approximately the same as that of the laser light is imaged by the imaging element 60. For example, among scattered light, fluorescence scattering and Raman scattering components with different wavelengths are not included. Therefore, the scattered light luminance amplitude value As is due to Rayleigh scattering, and the average scattered light luminance Is is due to Mie scattering.

The scattered light luminance amplitude value As is determined by the size and crystal grain density of the scattered particles, that is, the crystal grains of the strengthened crystallized glass, and the ratio between the average scattered light luminance Is and the scattered light luminance amplitude value As is determined by the ratio of the Rayleigh scattering component and the unscattered component. Therefore, it is determined by the size of the scattering particles, that is, the crystal grains.

From the two measured values of the scattered light luminance amplitude value As and the average scattered light luminance Is, the absolute value of the scattering particle diameter or scattering particle density cannot be calculated directly. However, in strengthened crystallized glass with different scattering particle diameters and scattering particle densities, that is, the scattered light luminance amplitude value As and the average scattered light luminance Is are different, and it is possible to determine the differences independently. . That is, even without directly calculating the absolute value of the scattering particle diameter or scattering particle density, changes in the scattering particle diameter or scattering particle density can be known by measuring the scattered light luminance amplitude value As or the average scattered light luminance Is.

Alternatively, the crystal grain size or grain density can be estimated by measuring the scattering particle size and scattering particle density and experimentally determining the relationship between the scattered light luminance amplitude value As and the average scattered light luminance Is and the crystal grain size or crystal grain density. .

For example, the relationship between the scattered light luminance amplitude value As and the average scattered light luminance Is and the crystal grain size or crystal grain density is experimentally determined and stored in the memory in the calculation unit 70 as a table or function. Then, the physical quantity measurement means 704 of the calculation unit 70 measures the scattered light luminance amplitude value As and the average scattered light luminance Is using the image obtained in the imaging process of step S403, and calculates the scattered light luminance amplitude value As using a table or function. And the crystal grain size or crystal grain density can be estimated from the measured value of the average scattered light luminance Is.

The measured values of the scattered light luminance amplitude value As and the average scattered light luminance Is reflecting the scattering particle diameter and scattering particle density are the values in area E in Fig. 15(a). However, if the area to be measured is moved from the glass surface of the laser image to each depth in the depth direction and measured, the scattering particle size and scattering particle density in the depth direction of the strengthened crystallized glass can be known. As a result, it can be confirmed that the crystallization state is uniform from the surface to the depth direction.

(Example 2 of measurement of physical quantity related to the strength of tempered glass)

As shown in FIG. 15(b), the scattered light image is not uniform and is in the form of particles. This is an unevenness caused by speckle because the incident light is laser light, and is called a speckle pattern. This speckle pattern is determined by the size and density of the scattering particles and the optical system.

The degree of luminance non-uniformity of the speckle pattern, for example, the luminance dispersion value of area E, is calculated and referred to as Ss. The dispersion value Ss reflects the scattering particle density. When the size of the crystal grain is small and the unscattered component is small and the intensity of the unscattered component cannot be measured, the crystal grain size and crystal grain density can be determined by the luminance dispersion value Ss of this speckle pattern and the scattered light luminance amplitude value As. can be guessed.

That is, even without directly calculating the absolute value of the scattering particle diameter or scattering particle density, changes in the scattering particle diameter or scattering particle density can be known by measuring the dispersion value Ss or the scattered light luminance amplitude value As. In addition, as in the case of the scattered light luminance amplitude value As and the average scattered light luminance Is, the scattering particle diameter and scattering particle density are measured, and the relationship between the scattering value Ss and the scattered light luminance amplitude value As and the crystal grain size or crystal grain density is experimentally obtained and presented in a table. By storing the function as a function in the memory in the calculation unit 70, the crystal grain size and crystal grain density can be estimated.

(Measurement example 3 of physical quantity related to the strength of tempered glass)

In Figure 15(a), θ is the angle along the beam of the laser light of the scattered light image. As will be described later, this angle θ is determined by the refractive index of the glass being measured.

It is desirable that the refractive index of the light supply member 40 is ideally completely equal to the refractive index of the tempered glass 200. However, since it is not realistic to replace the light supply member 40 for each type of tempered glass, a material having a refractive index close to that of the tempered glass 200 is generally used as the light supply member 40. do. That is, there is a slight discrepancy between the refractive index of the tempered glass 200 and the refractive index of the light supply member 40. Additionally, there is variation in the refractive index of tempered glass. If the refractive index of the light supply member 40 and the tempered glass 200 are different, the incident angle θ _s1 of the laser light L into the tempered glass 200 is different from the refraction angle θ _s1 ′ incident on the tempered glass. Since the angle is determined by the position and angle of the laser light source 10, the angle of each side of the light supply member 40, the refractive index, the position and angle of the imaging element, and the refractive index of the tempered glass, the refractive index of the tempered glass If other factors are known, the refractive index of the tempered glass can be calculated by measuring the angle θ along the beam of the laser light L of the scattered light image.

On the other hand, in strengthened crystallized glass, in most cases, the refractive index of the original glass and the refractive index of the crystals to be precipitated are different. For example, in strengthened crystallized glass using lithium aluminosilicate as a base material, the glass refractive index of the base material is 1.52, and the precipitated beta spodumene has a refractive index of 1.66. Additionally, the volume ratio of the precipitated crystals to the base material is about 10 to 50%, and the overall refractive index changes depending on the volume ratio of crystallization. In other words, the volume ratio of crystallization can be calculated by measuring the refractive index of the strengthened crystallized glass.

(Measurement example 4 of physical quantity related to the strength of tempered glass)

Figure 17 illustrates the relationship between the scattered light luminance amplitude value As and the depth of the glass. The external haze value of the glass surface layer can be estimated from the amplitude value of this glass surface. Additionally, the internal haze value can be estimated from the attenuation curve of the amplitude value inside the glass. Additionally, the transmittance can be estimated using this external haze value and internal haze value. Additionally, when one haze value is small, it may be estimated using only the other haze value. Additionally, by using a plurality of laser lights, the color of the tempered glass may be estimated by estimating the transmittance for each wavelength. Additionally, by measuring both sides of the glass, the difference in the surface layer of the glass can be determined from the difference in the amplitude value of the scattered light luminance or the difference in transmittance, thereby determining the surface of the glass. Specifically, anti-glare surface, anti-finger print surface, AR coating surface, anti-bacterial surface, ITO surface, float transfer surface (tin surface), etc. can be considered.

In addition, the measured values of the scattered light luminance amplitude value As, the average scattered light luminance Is, the dispersion value Ss, and the refractive index of the glass shown in the measurement examples 1 to 4 are not limited to tempered crystallized glass, and even in non-crystallized tempered glass, impurities It is useful as a numerical value representing glass defects such as abnormal crystals, composition, unevenness, transparency, etc. That is, the measurement shown in FIG. 14 may be performed after the process of producing tempered glass (not strengthened crystallized glass) by subjecting a plate to strengthening treatment. Additionally, physical quantities other than those shown in Measurement Examples 1 to 4 may be measured.

In this way, in the evaluation device 1, unlike the stress measurement device using surface guided light, stress measurement is not performed depending on the refractive index distribution of the tempered glass, but measurement is performed based on scattered light. Therefore, regardless of the refractive index distribution of the tempered glass (irrespective of the refractive index distribution of the tempered glass), the stress distribution of the tempered glass can be measured from the outermost surface of the tempered glass to a deeper part than before. For example, stress measurement is possible for lithium-aluminosilicate-based tempered glass, etc., which has the characteristic that the refractive index increases with depth from a certain depth.

Additionally, the polarization phase difference of the laser light is temporally continuously varied by one wavelength or more with respect to the wavelength of the laser light by the polarization phase difference variable member 30. Therefore, it becomes possible to obtain the phase of the periodic luminance change of the scattered light using the trigonometric least squares method or Fourier integral. In the least squares method and Fourier integration of trigonometric functions, unlike the conventional method of detecting the phase by changes in the positions of the wave's peaks or valleys, the entire data of the wave is handled and based on a previously known period. Therefore, it is possible to remove noise of different cycles. As a result, it becomes possible to easily and accurately obtain the phase of the periodic luminance change of the scattered light.

Additionally, in the evaluation device 1, a physical quantity related to the strength of tempered glass can be measured using the same image as the image captured for measuring stress distribution. This makes it possible to efficiently measure physical quantities related to strength, and also enables a wide range of evaluations of tempered glass.

<Modification 1 of the first embodiment>

Modification 1 of the first embodiment shows an example of an evaluation device with a different configuration from that of the first embodiment. In addition, in Modification 1 of the first embodiment, description of the same components as the already described embodiment may be omitted.

Fig. 18 is a diagram illustrating an evaluation device according to Modification 1 of the first embodiment. As shown in FIG. 18, the evaluation device 1A is different from the evaluation device 1 (see FIG. 1) in that the light wavelength selection member 80 is replaced with the light wavelength selection members 81 and 82. . Additionally, in Figure 18, the calculation unit is omitted.

The optical wavelength selection members 81 and 82 are, for example, two types of band-pass filters that transmit different wavelength bands, and can be switched manually or automatically.

The light wavelength selection member 81, like the light wavelength selection member 80 of the first embodiment, does not transmit 50% or more of light having a wavelength other than the wavelength of the laser light L, and preferably transmits 90% or more. I don't order it. Additionally, it is desirable that the width of the wavelength passing through the light wavelength selection member 81 is about 10 nm or less.

The light wavelength selection member 82 is a band-pass filter that transmits light of a different wavelength from the wavelength of the laser light L, and the center wavelength is, for example, the wavelength of Raman scattering peculiar to the tempered glass to be measured, or the wavelength of fluorescence scattering. can be matched with The width of the wavelength of light passing through the light wavelength selecting member 82 does not necessarily need to be as narrow as that of the light wavelength selecting member 81.

In the evaluation device 1A, first, the light wavelength selection member 81 is used to measure the stress and the scattered light luminance. Next, the light wavelength selection member 81 is switched to the light wavelength selection member 82, and the scattered light luminance is measured. Then, the ratio of the scattered light luminance when the light wavelength selecting member 81 is used and the scattered light luminance when the light wavelength selecting member 82 is used is calculated. As a result, information on crystals precipitated in the tempered glass, the amount of specific impurities, etc. can be obtained.

Additionally, the light wavelength selection member is not limited to two types, and three or more types may be switchably disposed.

<Modification 2 of the first embodiment>

Modification 2 of the first embodiment shows another example of an evaluation device with a different configuration from that of the first embodiment. In addition, in the second modification of the first embodiment, the description of the same components as the already described embodiment may be omitted.

Fig. 19 is a diagram illustrating an evaluation device according to Modification 2 of the first embodiment. As shown in FIG. 19, in the evaluation device 1B, the laser light source 10 is replaced with the laser light sources 11 and 12, and the optical wavelength selection member 80 is replaced with the optical wavelength selection members 81 and 82. The substitution point is different from the evaluation device 1 (see FIG. 1). Additionally, in Figure 19, the calculation unit is omitted.

The laser light sources 11 and 12 are two types of lasers with different oscillating wavelengths. The light wavelength selection members 81 and 82 are, for example, two types of band-pass filters that transmit different wavelength bands. In the case of the laser light source 11, the light wavelength selection member 81 is selected, and in the case of the laser light source 12, the light wavelength selection member 82 is selected, which can be switched manually or automatically.

The wavelength of the laser light sources 11 and 12 can be appropriately selected from, for example, 405 nm, 520 nm, 640 nm, 850 nm, etc. The light wavelength selection members 81 and 82 can appropriately select a band-pass filter that transmits only the wavelength vicinity of the selected laser light sources 11 and 12.

In the evaluation device 1B, the scattered light luminance amplitude value As, the average scattered light luminance Is, the dispersion value Ss, etc. can be measured using laser light sources 11 and 12 with different wavelengths and light wavelength selection members 81 and 82. there is. Since the brightness and behavior of scattered light are sensitive to the relationship between wavelength and scattered particle diameter, the crystallization state can be known with greater reliability by obtaining information from scattered light at multiple wavelengths.

In addition, the laser light source and the light wavelength selection member are not limited to two types, and three or more types may be switchably disposed.

In addition, the same effect can be obtained even if a plurality of evaluation devices 1 provided with lasers and optical wavelength selection members of different wavelengths are used instead of the evaluation device 1B.

<Modification 3 of the first embodiment>

Modification 3 of the first embodiment shows another example of an evaluation device with a different configuration from that of the first embodiment. In addition, in Modification 3 of the first embodiment, description of the same components as those of the already described embodiment may be omitted.

Fig. 20 is a diagram illustrating an evaluation device according to Modification 3 of the first embodiment. As shown in FIG. 20 (a), the evaluation device 1C includes the light wavelength selection member 80, the light conversion member 50, and the imaging element 60 with respect to the tempered glass 200, It is different from the evaluation device 1 (see FIG. 1) in that the light extraction member 42 is disposed on the opposite side to the light supply member 41 and is in contact with the back surface 220 of the tempered glass 200. do. Additionally, in Figure 20, the calculation unit is omitted.

In the evaluation device 1C, the scattered light L _S2 generated on the back surface 220 side of the tempered glass 200 is transmitted through a light extraction member 42 such as a prism, a light wavelength selection member 80, and a light conversion member 50. Through this, it is incident on the imaging device 60, and multiple images are captured by the imaging device 60 at temporal intervals within a certain period of time. Other than this, the configuration and operation are the same as those of the first embodiment.

In addition, by providing the light supply member 41, reflection of the laser light L on the surface 210 of the tempered glass 200 can be reduced, but the reflection of the laser light L on the surface 210 of the tempered glass 200 can be reduced. If the reflection of is no problem, the laser light L may be directly incident on the tempered glass 200 without providing the light supply member 41.

Since the tempered glass 200 generally has the same stress distribution on the front and back sides, the scattered light Ls on the surface 210 side (the incident side of the laser light L) of the tempered glass 200 is similar to the first embodiment. Detection may be performed, or, as in Modification 1 of the first embodiment, scattered light L _S2 on the back surface 220 side of the tempered glass 200 (the exit side of the laser light L) may be detected.

In addition, when detecting the scattered light L _S2 on the back surface 220 side of the tempered glass 200, it is preferable that the laser light in the tempered glass 200 satisfies the conditions of total reflection. By completely reflecting the laser light on the back surface 220 of the tempered glass 200, diffuse reflection on the back surface 220 of the tempered glass 200 can be reduced, preventing unwanted light from entering the imaging device 60. Because you can. By adjusting the incident angle of the laser light on the tempered glass 200, the laser light can satisfy the conditions of total reflection on the back surface 220 of the tempered glass 200.

Alternatively, as in the evaluation device 1D shown in (b) of FIG. 20, the scattered light L _S3 generated on the surface 210 side of the tempered glass 200 and emitted toward the back surface 220 is transmitted through a light extraction member such as a prism. (42), the light may be incident on the imaging device 60 through the light wavelength selection member 80 and the light conversion member 50, and multiple images may be captured by the imaging device 60 within a certain period of time and at temporal intervals. . Other than this, the configuration and operation are the same as those of the first embodiment.

In addition, similarly to the evaluation device 1C, the reflection of the laser light L on the surface 210 of the tempered glass 200 can be reduced by providing the light supply member 41, but the reflection of the laser light L on the tempered glass 200 ( If the reflection from the surface 210 of the 200 is no problem, the laser light L may be directly incident on the tempered glass 200 without providing the light supply member 41.

In either case of the evaluation devices 1C and 1D, as in the evaluation device 1, from the phase change of the periodic luminance change of the scattered light along the laser light L incident on the tempered glass 200, the tempered glass 200 The stress distribution in the depth direction from the back surface 220 can be calculated.

In particular, according to the evaluation device 1D, the focus of the laser is set at the same position from the glass surface layer regardless of the glass plate thickness. Therefore, even when measuring tempered glass with the same stress distribution, the focus position of the laser does not need to be adjusted or is completed through fine adjustment, which has the effect of shortening the measurement time and improving repeatability. .

<Modification 4 of the first embodiment>

Modification 4 of the first embodiment shows another example of an evaluation device with a different configuration from that of the first embodiment. In addition, in Modification Example 4 of the first embodiment, description of the same components as the already described embodiment may be omitted.

Fig. 21 is a diagram illustrating an evaluation device according to modification example 4 of the first embodiment. As shown in FIG. 21, the evaluation device 1E uses the light wavelength selection member 80A, the light conversion member 50A, and the imaging element 60A to provide a light supply member ( It is different from the evaluation device 1 (see FIG. 1) in that the light extraction member 42 is disposed on the opposite side from 40 and is in contact with the back surface 220 of the tempered glass 200. Additionally, in Figure 21, the calculation unit is omitted.

In the evaluation device 1E, similarly to the evaluation device 1, scattered light L _S emitted from the surface 210 side of the tempered glass 200 can be detected. In addition, in the evaluation device 1E, the scattered light L _S2 emitted from the back surface 220 side of the tempered glass 200 is transmitted through the light extraction member 42 such as a prism, the light wavelength selection member 80A, and the light conversion member ( 50A), it is incident on the imaging device 60A, and multiple images are captured by the imaging device 60A at temporal intervals within a certain period of time. Other operations are the same as in the first embodiment.

In the evaluation device 1E, the stress distribution in the depth direction from the surface 210 of the tempered glass 200 and the stress distribution in the depth direction from the back surface 220 of the tempered glass 200 are determined by the configuration of FIG. 21. can be calculated simultaneously. This is effective when measuring tempered glass in which the front and back sides do not have the same stress distribution, or when you want to check whether the front and back sides have the same stress distribution in any piece of tempered glass.

<Modification 5 of the first embodiment>

Modification 5 of the first embodiment shows an example of a polarization phase difference variable member with a different configuration from that of the first embodiment. Additionally, in Modification 5 of the first embodiment, description of the same components as those of the already described embodiment may be omitted.

As a polarization phase difference variable member, the polarization phase difference can also be varied by applying pressure, utilizing the photoelastic effect of the transparent material. Figure 22 is an explanatory diagram of a polarization phase difference variable member using the photoelastic effect.

In the polarization phase difference variable member 30A shown in FIG. 22, one side of the substantially rectangular polarization phase difference generating material 310 is fixed with a fixing jig 311, and the opposite side of the polarization phase difference generating material 310 is a piezo element. It is in contact with one surface of 312, and the opposite surface of the piezo element 312 is fixed with a fixing jig 313.

The surface of the polarization phase difference generating material 310 in contact with the piezo element 312 and the two opposing surfaces 310a and 310b in a direction perpendicular to the surface are processed to be mirror surfaces, so that polarized light Q can pass through. . As the polarization retardation generating material 310, a material that is transparent and has a large photoelastic effect, for example, quartz glass as glass and polycarbonate as resin, can be used.

When a voltage is applied, the piezo element 312 expands and contracts in the voltage application direction. Whether it expands or contracts is determined by the voltage. Although not shown in FIG. 22, a piezo element driving voltage generation circuit that controls the voltage applied to the piezo element 312 is connected to the piezo element 312.

When a voltage that causes the piezo element 312 to expand is applied by the piezo device driving voltage generation circuit, the piezo element 312 tries to expand in length in the direction in which the voltage is applied, but the length of the piezo element 312 is extended in the direction in which the voltage is applied, but the polarization phase difference generating material ( The piezo element 312 is arranged so that 310) is positioned.

When a voltage in the direction in which the piezo element 312 is stretched is applied by the piezo element driving voltage generation circuit, the piezo element 312 is stretched in the direction of the polarization phase difference generating material 310. Since it is fixed with the fixing jigs 311 and 313, the polarization phase difference generating material 310 is contracted and compressive stress is applied. Due to the compressive stress of the polarization phase difference generating material 310, birefringence occurs in the direction through which the light ray Q passes, and a polarization phase difference occurs in the light ray Q. The amount of polarization phase difference is proportional to the voltage applied to the piezo element 312, and the polarization phase difference can be controlled with a piezo element driving voltage generation circuit that applies a driving voltage to the piezo element 312.

For example, as the polarization phase difference generating material 310, a 10 mm cube of polycarbonate is used. The photoelastic constant of polycarbonate is about 700 nm/cm/MPa, and the Young's modulus is about 2.5 GPa.

As the piezo element 312, for example, a laminated piezo element in which electrodes and high dielectric ceramics with a perovskite crystal structure, such as lead zirconate titanate, which have a large piezo effect, are alternately laminated can be used. For example, in a multilayer piezo element, by making 100 layers with a thickness of 200 μm and a length of about 20 mm, an elongation of 10 μm or more can be obtained with an applied voltage of 100 V.

Since the Young's modulus of lead zirconate titanate, which is the material of the piezo element 312, is more than 10 times that of polycarbonate, the elongation of the piezo element 312 is almost all compression of the polycarbonate, and the piezo element 312 ) is stretched by 10 μm, the 10 mm cube of polycarbonate is compressed by 0.1%, and the compressive stress at that time becomes 2.5 MPa. When the light beam Q passes through the 10 mm polarization retardation generating material 310, a polarization retardation of 1750 nm is generated, and if the wavelength is 630 nm, the polarization retardation of 2.8λ can be varied.

For example, as the polarization phase difference generating material 310, a 10 mm cube of quartz glass is used. The photoelastic constant of quartz glass is about 35 nm/cm/MPa, and the Young's modulus is about 70 GPa. Since the Young's modulus of lead zirconate titanate, which is the material of the piezo element 312, is almost at the same level as that of quartz, almost half of the elongation of the piezo element 312 is due to compression of the quartz glass, and the piezo element 312 elongates by 10㎛. When this happens, the 10 mm cube polycarbonate is compressed by about 0.05%, and the compressive stress at that time becomes about 35 MPa. When the light beam Q passes through the 10 mm polarization phase difference generating material 310, a polarization phase difference of 1225 nm is generated, and if the wavelength is 630 nm, the polarization phase difference of 1.9λ can be varied.

When creating a polarization retardation by modifying the material in this way, the product of the photoelastic constant and Young's modulus is important, and is 0.18 (unitless) for polycarbonate and 0.26 (unitless) for quartz. In other words, it becomes important to use a transparent member with this value of 0.1 or more as the polarization phase difference generating material 310.

In this way, the polarization phase difference variable member is not limited to the liquid crystal element, and can temporally change the polarization phase difference when incident on the tempered glass 200, and the polarization phase difference to be changed is 1 times the wavelength λ of the laser light. If the above can be achieved, it may be in a form that applies a piezo element, or it may be in any other form.

<Second Embodiment>

In the second embodiment, an example of an evaluation device used in combination with the evaluation device according to the first embodiment is shown. Additionally, in the second embodiment, descriptions of the same components as those in the already described embodiment may be omitted.

Fig. 23 is a diagram illustrating an evaluation device according to the second embodiment. For example, it is explained in Yogyo-Kyokai-Shi (Journal of the Ceramics Association) 87 {3} 1979. As shown in FIG. 23, the evaluation device 2 includes a light source 15, a light supply member 25, a light extraction member 35, a light conversion member 45, and a polarizing member 55. It has an imaging element 65 and a calculation unit 75. The evaluation device 2 can be used in combination with the evaluation device 1 shown in FIG. 1. The evaluation device 2 includes the evaluation device 1A shown in FIG. 18, the evaluation device 1B shown in FIG. 19, the evaluation devices 1C and 1D shown in FIG. 20, and the evaluation device shown in FIG. 21 ( It may be used in combination with 1E).

In the evaluation device 2, the light source 15 is arranged to cause light ray La to enter the surface layer of the tempered glass 200 from the light supply member 25. In order to utilize interference, the wavelength of the light source 15 is preferably a short wavelength that provides simple light and dark display.

As the light source 15, for example, a Na lamp from which short-wavelength light can be easily obtained can be used, and the wavelength in this case is 589.3 nm. Additionally, as the light source 15, a mercury lamp with a shorter wavelength than the Na lamp may be used, and the wavelength in this case is, for example, 365 nm, which is the mercury I line. However, since mercury lamps have many bright lines, it is desirable to use them through a band-pass filter that transmits only the 365 nm line.

Additionally, an LED (Light Emitting Diode) may be used as the light source 15. In recent years, LEDs with many wavelengths have been developed, but the spectrum width of the LED is 10 nm or more at half maximum, the short wavelength is poor, and the wavelength changes depending on the temperature. For that reason, it is preferable to use it through a band-pass filter.

When the light source 15 is configured to pass an LED through a band-pass filter, Na lamps and mercury lamps do not have shorter wavelengths, but are suitable in that any wavelength from the ultraviolet region to the infrared region can be used. Additionally, since the wavelength of the light source 15 does not affect the basic principle of measurement by the evaluation device 2, it is okay to use a light source other than the wavelengths exemplified above.

However, by using a light source that irradiates ultraviolet rays as the light source 15, the resolution of the measurement can be improved. That is, since the surface layer of the tempered glass 200 measured by the evaluation device 2 has a thickness of about several μm, an appropriate number of interference fringes can be obtained by using a light source that irradiates ultraviolet rays as the light source 15, and the resolution is improved. It improves. On the other hand, if a light source that irradiates light with a longer wavelength than ultraviolet rays is used as the light source 15, the resolution decreases because the number of interference fringes decreases.

The light supply member 25 and the light extraction member 35 are mounted in optical contact with the surface 210 of the tempered glass 200, which is the object to be measured. The light supply member 25 has a function of making light from the light source 15 incident on the tempered glass 200 . The light extraction member 35 has a function of emitting light propagated from the surface layer of the tempered glass 200 to the outside of the tempered glass 200.

As the light supply member 25 and the light extraction member 35, for example, a prism made of optical glass can be used. In this case, since light rays optically enter and exit the surface 210 of the tempered glass 200 through these prisms, the refractive index of these prisms needs to be larger than that of the tempered glass 200. Additionally, on the inclined surface of each prism, it is necessary to select a refractive index at which the incident light and the exit light pass approximately perpendicularly.

For example, when the inclination angle of the prism is 60° and the refractive index of the tempered glass 200 is 1.52, the refractive index of the prism is, for example, 1.72. Additionally, as the light supply member 25 and the light extraction member 35, other members having similar functions may be used instead of the prism. Additionally, the light supply member 25 and the light extraction member 35 may have an integrated structure. In addition, in order to ensure stable optical contact, between the light supply member 25 and the light extraction member 35 and the tempered glass 200, the refractive index of the light supply member 25 and the light extraction member 35 and In some cases, a liquid (which may be in a gel form) having a refractive index between those of the tempered glass 200 is filled.

An imaging element 65 is disposed in the direction of the light emitted from the light extraction member 35, and between the light extraction member 35 and the imaging element 65, a light conversion member 45 and a polarizing member 55. is inserted.

The light conversion member 45 has a function of converting the light emitted from the light extraction member 35 into a bright line array and concentrating the light onto the imaging element 65 . As the light conversion member 45, for example, a convex lens can be used, but other members with similar functions may also be used.

The polarizing member 55 is a light separation means that has a function of selectively transmitting one of two types of light components that vibrate in parallel and perpendicular to the interface between the tempered glass 200 and the light extraction member 35. . As the polarizing member 55, for example, a polarizing plate arranged in a rotatable state can be used, but another member having a similar function may be used. Here, the light component that vibrates parallel to the interface between the tempered glass 200 and the light extraction member 35 is S-polarized light, and the light component that vibrates perpendicularly is P-polarized light.

Additionally, the boundary surface between the tempered glass 200 and the light extraction member 35 is perpendicular to the exit surface of the light emitted to the outside of the tempered glass 200 through the light extraction member 35. Therefore, the light component that vibrates perpendicular to the exit surface of the light emitted to the outside of the tempered glass 200 through the light extraction member 35 is S-polarized light, and the light component that vibrates in parallel can be said to be P-polarized light.

The imaging element 65 has a function of converting the light emitted from the light extraction member 35 and received via the light conversion member 45 and the polarizing member 55 into an electric signal. As the imaging element 65, for example, an element similar to the imaging element 60 can be used.

The arithmetic unit 75 has a function of importing image data from the imaging device 65 and performing image processing or numerical calculations. The calculation unit 75 may be configured to have functions other than this (for example, a function to control the light amount or exposure time of the light source 15, etc.). The calculation unit 75 includes, for example, a Central Processing Unit (CPU), Read Only Memory (ROM), Random Access Memory (RAM), and main memory.

In this case, various functions of the calculation unit 75 can be realized by a program recorded in ROM or the like being read into main memory and executed by the CPU. The CPU of the calculation unit 75 can read or store data from RAM as needed. However, part or all of the calculation unit 75 may be realized only by hardware. Additionally, the calculation unit 75 may physically have a plurality of devices, etc. As the calculation unit 75, for example, a personal computer can be used.

In the evaluation device 2, the light ray La incident on the surface layer of the tempered glass 200 from the light source 15 through the light supply member 25 propagates within the surface layer. Then, when the light ray La propagates within the surface layer, a mode is generated due to the optical waveguide effect, proceeds along several predetermined paths, and is extracted to the outside of the tempered glass 200 by the light extraction member 35.

Then, by the light conversion member 45 and the polarizing member 55, bright lines of P-polarized light and S-polarized light are formed for each mode on the imaging element 65. Image data of bright lines of P-polarized light and S-polarized light of the number of modes generated on the imaging device 65 are sent to the calculation unit 75. The calculation unit 75 calculates the positions of bright lines of P-polarized light and S-polarized light on the imaging device 65 from image data sent from the imaging device 65.

With this configuration, the evaluation device 2 determines each of the P-polarized light and the S-polarized light in the depth direction from the surface in the surface layer of the tempered glass 200, based on the positions of the bright lines of the P-polarized light and the S-polarized light. The refractive index distribution can be calculated. In addition, based on the calculated difference in the refractive index distribution of P-polarized light and S-polarized light and the photoelastic constant of the tempered glass 200, the stress distribution in the depth direction from the surface in the surface layer of the tempered glass 200 is calculated. can do.

In this way, the evaluation device 2 is an evaluation device capable of measuring stress distribution using guided light from the surface layer of tempered glass. Here, the guided light on the glass surface is generated in a layer where the refractive index of the tempered glass 200 decreases as it goes deeper from the surface. Guided light does not occur in layers where the refractive index increases as the depth increases. For example, in lithium-aluminosilicate-based glass, the refractive index only near the outermost surface of the glass decreases as the depth increases, but from a certain depth, the refractive index increases with depth. In the case of such tempered glass, guided light is generated only in the outermost layer, where the refractive index decreases as the depth increases, and the stress distribution can be measured up to the depth where the refractive index distribution is reversed.

On the other hand, in the image of scattered light shown in FIG. 9 of the first embodiment, point A in FIG. 9 is the glass surface, and the surface scattered light is strongly spread around. This spread surface scattered light reflects information of surface points. At surface point A, the information is correct, but for example, the scattered light of the laser light L in a slightly deeper part of the glass from surface point A is the scattered light that reflects the original stress of the glass at that point, and the stress at surface point A is The reflected scattered light is mixed, and it is difficult to accurately measure stress in areas where surface scattered light overlaps.

The depth of the part where this surface scattered light overlaps varies depending on the quality of the glass and the surface condition of the glass, but is usually about 10 μm. The depth of the reinforcing layer of tempered glass is deep, and in the surface area near the outermost surface, for example, about 10㎛ in depth, the change in the depth direction of stress is gradual, the surface stress value is low, or the reinforcing layer is deep. In tempered glass, even within a depth of 10 μm that cannot be accurately measured, accurate stress can be estimated by extrapolating the distribution of stress in deeper areas to the glass surface.

However, the stress distribution of the tempered glass 200 is near the outermost surface, for example, in tempered glass where the stress suddenly increases between the surface of the tempered glass 200 and a depth of 10 μm, the stress value near the outermost surface by extrapolation A large error occurs in the estimated value. In particular, the stress value on the outermost surface has a large error. However, outside the area where this surface scattered light interferes, the stress distribution can be measured accurately as an absolute value.

Among the stress values at the outermost surface or the stress distribution near the outermost surface measured with the evaluation device (2), and the stress distribution measured with the evaluation device (1), those that are not disturbed by surface scattered light By combining the stress distribution of sufficiently deep portions from the outermost surface, the overall stress distribution can be measured with high precision.

In the case where the sufficiently reliable depth region of the evaluation device 1 and the measurable depth region of the evaluation device 2 are discontinuous, in tempered glass, using the theoretically expected stress distribution function, the least squares method is used. , by performing approximate calculations, the stress in discontinuous areas can also be accurately estimated.

Figure 24 is a diagram showing the stress distribution measured by the evaluation devices 1 and 2 in the same graph. More specifically, the stress near the outermost surface measured with the evaluation device 2 for tempered glass having a two-stage chemically strengthened stress distribution and having a region where the slope of the stress suddenly changes around 10 ㎛ depth from the surface. The distribution (area A) and the stress distribution (area C) in a sufficiently reliable area measured by the evaluation device 1 are shown in the same graph.

In the example of FIG. 24, there is a region B in the middle that is not measured by either the evaluation device 1 or the evaluation device 2. Based on the stress distributions in regions A and C, a curve obtained by the least squares method as a function of the expected stress distribution in region B is shown as a dotted line. In this case, even if there is no actual data of the area containing the inflection point, the location of the inflection point can also be estimated from the curve obtained by the least squares method.

(Measurement flow)

Next, the measurement flow will be explained with reference to FIGS. 25 and 26. 25 is a flowchart illustrating an evaluation method using the evaluation device 2. FIG. 26 is a diagram illustrating functional blocks of the calculation unit 75 of the evaluation device 2.

First, in step S407, light from the light source 15 is incident on the surface layer of the tempered glass 200 (light supply process). Next, in step S408, the light propagated within the surface layer of the tempered glass 200 is emitted to the outside of the tempered glass 200 (light extraction process).

Next, in step S409, the light conversion member 45 and the polarizing member 55 respond to two types of light components (P polarized light and S polarized light) that vibrate parallel and perpendicular to the emission surface of the emitted light, It is converted into two types of bright line rows, each having at least two bright lines (light conversion process).

Next, in step S410, the imaging element 65 images two types of bright line rows converted by the light conversion process (imaging process). Next, in step S411, the position measurement means 751 of the calculation unit 75 measures the position of each bright line in the two types of bright line rows from the image obtained in the imaging process (position measurement process).

Next, in step S412, the stress distribution calculation means 752 of the calculation unit 75 calculates the strength of the tempered glass 200 corresponding to the two types of light components from the positions of at least two bright lines in each of the two types of bright line rows. The refractive index distribution from the surface to the depth direction is calculated. Then, based on the difference in the refractive index distribution of the two types of light components and the photoelastic constant of the glass, the stress distribution extending from the surface of the tempered glass 200 in the depth direction is calculated (stress distribution calculation step).

Next, in step S413, the synthesis means 753 of the calculation unit 75 combines the stress distribution calculated in step S412 with the stress calculated by the stress distribution calculation means 703 of the calculation unit 70 of the evaluation device 1. Composite the distribution.

In the case where the sufficiently reliable depth region of the evaluation device 1 and the measurable depth region of the evaluation device 2 are discontinuous, the synthesis means 753 of the calculation unit 75, for example, as shown in FIG. 24 As shown, the stress distribution in area A calculated by the stress distribution calculation means 752 of the calculation unit 75 of the evaluation device 2 and the stress distribution calculation means 703 of the calculation unit 70 of the evaluation device 1 are Based on the calculated stress distribution in region C, the stress distribution in region B is calculated using the least squares method or the like.

Additionally, the calculation unit 75 may be provided with a CT value calculation means for calculating a CT value, a DOL_Zero value calculation means for calculating a DOL_Zero value, etc., in addition to the structure shown in FIG. 26 . In this case, the CT value or DOL_Zero value can be calculated based on the stress distribution calculated by the synthesis means 753.

Next, an example of deriving each characteristic value of the stress distribution will be described. Figure 27 is a diagram illustrating the stress distribution in the depth direction of tempered glass. In Figure 27, CS2 is the stress value at the outermost surface, CS_TP is the stress value at the position where the stress distribution bends, CT is the stress value at the deepest part of the glass, DOL_TP is the glass depth at the position where the stress distribution bends, and DOL_zero is The glass depth at which the stress value becomes zero, DOL_tail, is the glass depth at which the stress value becomes the same as CT.

As shown in FIG. 28, the stress distribution can be measured in step S501, and the characteristic value can be derived in step S502 based on the stress distribution measured in step S501. This is explained in more detail below.

Figure 29 shows an example of deriving each characteristic value from the measured stress distribution. For example, in step S601 of FIG. 30, the entire stress distribution (the entire solid line shown in FIG. 29) is measured by the evaluation device 1. Then, each characteristic value is derived in step S604.

In step S604, each characteristic value is derived, for example, as follows. That is, as shown in Fig. 29, consider two line segments: a line segment passing through CS2 and a line segment passing through DOL_zero. And, when the difference between the two line segments and the measured stress distribution is minimized, the intersection points of the two line segments are called CS_TP and DOL_TP. Additionally, the intersection of the line segment passing through DOL_zero and CT is called DOL_tail.

This method includes, for example, lithium-aluminosilicate-based tempered glass, tempered glass that has been chemically strengthened once using a mixed salt of sodium nitrate and potassium nitrate, and molten salt containing sodium nitrate and molten salt containing potassium nitrate. It can be applied to tempered glass that has been chemically strengthened by each use more than once, and tempered glass that has undergone both wind and chemical strengthening, etc.

Figure 31 shows another example of deriving each characteristic value from the measured stress distribution. For example, in step S601 of FIG. 32, the overall stress distribution is measured by the evaluation device 1. Next, in step S602, the glass surface layer side rather than DOL_TP is measured using the evaluation device 2. Additionally, it is difficult to measure the area deeper than DOL_TP with the evaluation device 2. Step S601 and step S602 are net floating.

Next, in step S603, the portion measured in step S602 and the portion measured in step S601 on the deeper side are combined. As a result, the stress distribution in Figure 31 is obtained. After that, for example, each characteristic value can be derived in the same manner as step S604 in FIG. 30 .

Alternatively, step S602 is similar to the above, and DOL_zero and CT are measured in step S601. Then, in step S603, as shown in FIG. 33, a straight line passing through DOL_zero obtained in step S601 is drawn from the intersection of CS_TP and DOL_TP obtained in step S602, and the stress distribution may be used up to CT.

Quality judgment can be made using each characteristic value obtained from measurement of stress distribution. Figure 34 is an example of a flowchart of quality judgment using each characteristic value obtained from measurement of stress distribution. In FIG. 34, steps S601 to S603 are first executed as in FIG. 32. Next, in step S604, six characteristic values (hereinafter sometimes simply referred to as six measurement values) of CS2, CS_TP, CT, DOL_TP, DOL_zero, and DOL_tail are derived based on the data obtained in steps S601 and S602. do. Next, in step S605, it is determined whether the six characteristic values derived in step S604 are within the allowable range determined in the prior requirement specifications. In this method, two measurements of steps S601 and S602 are required for one quality judgment.

Figure 35 is another example of a flowchart of quality judgment using each characteristic value obtained from measurement of stress distribution. In Figure 35(a), preliminary data is first acquired in step S600. Specifically, for example, for one lot, for a predetermined quantity, six characteristic values are derived using the evaluation devices 1 and 2. Then, based on the required specifications of the product and the derived characteristic values, the allowable range of characteristic values is determined.

Next, in step S601, the deeper side of the glass than DOL_TP is measured using the evaluation device 1. Then, in step S604, six characteristic values are derived again based on the data of the evaluation device 2 in step S600 and the data of the evaluation device 1 in step S601.

Next, in step S605, it is determined whether the six characteristic values measured in step S604 fall within the allowable range determined in step S600. In this method, for quantities other than those measured in the preliminary process, only one measurement in step S601 is required for one quality judgment. Therefore, the quality control flow can be simplified compared to the case of FIG. 34.

In addition, in the preliminary data shown in Figure 35 (a), the sheet thickness is also measured, and by measuring the sheet thickness in step S601, the characteristic value may be derived by including the effect of different sheet thicknesses in step S604.

Additionally, it may be done as shown in Figure 35(b). In Figure 35(b), as in Figure 35(a), preliminary data is first acquired in step S600, and the allowable range of characteristic values is determined.

Next, in step S602, the glass surface layer side rather than DOL_TP is measured using the evaluation device 2. Then, in step S604, six characteristic values are derived again based on the data of the evaluation device 1 in step S600 and the data of the evaluation device 2 in step S602.

Next, in step S605, it is determined whether the six characteristic values measured in step S604 fall within the allowable range determined in step S600. In this method, for quantities other than those measured in the preliminary process, only one measurement in step S602 is required for one quality judgment. Therefore, in this case as well, like (a) in Figure 35, the quality control flow can be simplified compared to the case in Figure 34.

In addition, in the preliminary data in Figure 35 (b), the sheet thickness is also measured, and by measuring the sheet thickness in step S602, the characteristic value may be derived by including the effect of different sheet thicknesses in step S604.

Figure 36 is an example of a flowchart of quality judgment when strengthening twice or more for lithium-containing glass (glass containing 2 wt% or more of lithium) such as lithium-aluminosilicate-based tempered glass. In Figure 36, the tempered glass for tempering other than the final time is judged to pass or not based on the measurement result of the evaluation device 1, and the tempered glass for the final tempering is judged to pass based on the measurement result of the evaluation device 2. Determine whether or not

Specifically, first, the first chemical strengthening is performed in step S650. Then, in step S651, the stress distribution (hereinafter sometimes referred to as the first stress distribution) on the deeper side of the glass than DOL_TP is measured by the evaluation device 1. If there is a problem in the measurement result in step S651 (in the case of NG), the tempered glass is not subject to shipment. On the other hand, if there is no problem in the measurement result in step S651 (in the case of OK), the process proceeds to step S652 and a second chemical strengthening is performed. The pass/fail judgment (OK/NG judgment) in step S651 can be made based on all or part of the six characteristic values (e.g., CT and DOL_zero) derived from the measurement results of the evaluation device 1. there is.

Next, in step S653, the stress distribution (hereinafter sometimes referred to as the second stress distribution) on the glass surface layer side rather than DOL_TP is measured by the evaluation device 2. If there is a problem in the measurement result in step S653 (in the case of NG), the tempered glass is not subject to shipment. On the other hand, if there is no problem in the measurement result in step S653 (in the case of OK), the process proceeds to the next step in step S654. The specific method of determining whether to pass or fail (determination of OK/NG) in step S653 will be described later.

The next process includes, for example, a touch polish process. The touch polish process is, for example, a final polishing process in which the surface of the tempered glass 200 is polished at a relatively low surface pressure. However, it is not essential to provide a touch polish process, and step S653 may be the final process.

Additionally, after step S653, a third chemical strengthening and pass judgment may be performed. In this case, in step S653, the tempered glass for the second tempering is judged to pass or fail based on the measurement results of the evaluation device 1 as in step S651, and the tempered glass for the third tempering (final tempering) is judged as pass or not. The glass is judged to pass or fail based on the measurement results of the evaluation device 2.

The same applies when the number of temperings increases further, and the tempered glass for tempering other than the final time is judged to pass or fail based on the measurement results of the evaluation device (1), and the tempered glass for the final tempering is judged to be pass or not using the evaluation device (2). Pass or fail is judged based on the measurement results. This makes it possible to shorten the evaluation time while maintaining measurement reproducibility.

Here, a specific method of pass/failure judgment (OK/NG judgment) in step S653 will be described.

(Deriving data for evaluation)

First, data for evaluation is derived in advance. Specifically, as shown in FIG. 37, the first chemical strengthening is performed in step S660. Then, in step S661, the deeper side of the glass than DOL_TP is measured by the evaluation device 1 (first measurement). Subsequently, a second chemical strengthening is performed in step S662. Then, in step S663, the deeper side of the glass than DOL_TP is measured by the evaluation device 1 (second measurement). Then, in step S664, evaluation data (first stress distribution) is derived based on one or both of the first measurement result obtained in step S661 and the second measurement result obtained in step S663.

In addition, derivation of data for evaluation is performed using only a predetermined quantity per lot. In addition, the first chemical strengthening and the second chemical strengthening in deriving evaluation data are performed under the same conditions as the first chemical strengthening and the second chemical strengthening during mass production.

(Method for judging pass/failure in step S653)

First, based on the measurement results obtained in step S653, the plate thickness t of the glass to be chemically strengthened, and the evaluation data obtained as shown in Figure 37, the stress distribution (second stress distribution) on the surface layer of the glass is higher than that of DOL_TP. The stress distribution (first stress distribution) on the deep side of the glass is synthesized. For example, the result shown in Figure 38 is obtained.

In Figure 38, the FSM shown with a solid line represents the stress distribution (second stress distribution) on the surface layer side of the glass compared to DOL_TP, and the SLP shown with a broken line represents the stress distribution (first stress distribution) on the deeper side of the glass than DOL_TP. Additionally, t/2 represents the center of the glass plate thickness. Additionally, CS ₀ represents the surface stress value when the first stress distribution (SLP) is extended to the surface side of the tempered glass.

Next, CT is found from the stress distribution after synthesis, each characteristic value is derived, and a pass/fail judgment (shipment judgment) is made based on whether each characteristic value is within the allowable range.

At this time, the second stress distribution (FSM in Figure 38) may be approximated by a function. An example of function approximation is linear approximation using Equation 2 below (Equation 2).

In equation 2, σf(x) is the second stress distribution, a is the slope, and CS2 is the stress value of the outermost surface.

Another example of function approximation is curve approximation using Equation 3 below.

In Equation 3, σf(x) is the second stress distribution, a is the slope, CS2 is the stress value of the outermost surface, and erfc is the error function shown in Equation 4 (Equation 4).

Another example of function approximation is polynomial approximation.

Additionally, the first stress distribution (SLP in FIG. 38) may be moved in the vertical direction (stress value axial direction) in FIG. 38. Specifically, for example, in the stress distribution after synthesis shown in Figure 38, the first stress distribution (SLP) is moved in the stress value axis direction, and the CT at which the integral value of the stress distribution after synthesis is zero is found. Derive each characteristic value. Then, a pass/fail judgment (shipment judgment) can be made based on whether each characteristic value is within the allowable range. At this time, even if the vertical movement amount of the first stress distribution is calculated from a theoretical equation based on the glass plate thickness and the second stress distribution, the movement amount is assumed, the integral value of the stress distribution after synthesis is calculated, and the integral value is calculated. You can also find the movement amount whose value is zero.

In addition, the stress distribution σ(x) after synthesis is approximated by Equation 5 below, and the integral value of σ(x) (x=0 to t/2: t is the glass plate thickness) is set to zero. Find the corresponding CT and derive each characteristic value. Additionally, a pass/fail judgment (shipment judgment) may be made based on whether each characteristic value is within the allowable range.

In Equation 5, σ(x) is the stress distribution after synthesis, σf(x) is the second stress distribution, t is the plate thickness of the tempered glass, and CS ₀ and c are parameters derived based on the first stress distribution.

In equation 5, t is known. Additionally, CS ₀ and c can be obtained from the measurement results of the evaluation device 1 in deriving the evaluation data.

CS ₀ and c may be obtained from simulations based on reinforcement conditions.

Alternatively, CS ₀ and c are CS ₀ 'and c' derived from the measurement results of the tempered glass evaluation device 1 regarding strengthening before the final round in mass production, and Equation 6 below (Equation 6) and may be obtained by Equation 7 (Equation 7).

In equation 6, A1 is the proportionality constant.

In equation 7, A2 is the proportionality constant.

Here, A1 and A2 may be obtained from the measurement results of the evaluation device 1 in deriving the evaluation data, or may be obtained through simulation.

Additionally, the approximation of σ(x) is not limited to Equation 5, and may be, for example, a polynomial approximation.

[Example]

In Example 1, CS_TP (MPa), which is a characteristic value of the stress distribution of tempered glass subjected to chemical strengthening twice, was derived three times for the same sample by the method described in Figure 34, and the evaluation time and measurement reproducibility were investigated. .

In Example 2, CS_TP (MPa), which is a characteristic value of the stress distribution of tempered glass subjected to chemical strengthening twice, was derived three times for the same sample by the method described in Figures 36 to 38, and the evaluation time and measurement reproducibility were determined. was investigated. Specifically, based on the measurement results obtained in step S653 in FIG. 36, the sheet thickness t of the chemically strengthened glass, and the evaluation data obtained as shown in FIG. 37, the second stress distribution (FSM) and the first stress distribution ( When synthesizing the SLP, the first stress distribution (SLP) was moved in the stress value axis direction, the CT at which the integral value of the stress distribution after synthesis was zero was found, and CS_TP was derived.

In Example 3, CS_TP (MPa), which is a characteristic value of the stress distribution of tempered glass subjected to chemical strengthening twice, was derived three times for the same sample by the method described in Figures 36 to 38, and the evaluation time and measurement reproducibility were determined. was investigated. Specifically, based on the measurement results obtained in step S653 in FIG. 36, the sheet thickness t of the chemically strengthened glass, and the evaluation data obtained as shown in FIG. 37, the second stress distribution (FSM) and the first stress distribution ( When synthesizing SLP), the stress distribution σ(x) after synthesis is approximated by Equation 5, and the integral value of σ(x) (x=0 to t/2: t is the glass plate thickness) is zero. was found and CS_TP was derived.

As Comparative Example 1, CS_TP (MPa), which is a characteristic value of the stress distribution of tempered glass subjected to chemical strengthening twice, was derived three times for the same sample by the method described in Patent Document 4, and the evaluation time (minutes) and measurement Reproducibility (difference between maximum and minimum values) was investigated.

The stress distribution obtained in Comparative Example 1 and Examples 1 to 3 is shown in Figure 39, and a summary of the results is shown in Table 2. Additionally, in Figure 39, the stress value at the position where the stress distribution bends is CS_TP.

From Table 2, in Comparative Example 1, the value of CS_TP derived three times for the same sample varied each time, and measurement reproducibility was poor. On the other hand, in Examples 1 to 3, there was little variation in the value of CS_TP derived three times for the same sample, and measurement reproducibility was significantly improved compared to Comparative Example 1. In particular, in Examples 2 and 3, measurement reproducibility is excellent. Additionally, in Example 1, the evaluation time was long, but in Examples 2 and 3, the number of measurements by the evaluation device 1 was reduced, so it was confirmed that the evaluation time was short and measurement reproducibility was excellent.

<Third embodiment>

The third embodiment shows an example in which liquid is placed between the light supply member and the tempered glass. In addition, in the third embodiment, description of the same components as the already described embodiment may be omitted.

Fig. 40 is a diagram illustrating an evaluation device according to the third embodiment, and shows a cross section near the interface between the light supply member and the tempered glass.

As shown in FIG. 40 , in this embodiment, a liquid 90 having a refractive index substantially the same as that of the tempered glass 200 is placed between the light supply member 40 and the tempered glass 200. This is because the refractive index of the tempered glass 200 is slightly different depending on the type of tempered glass, so in order to completely match the refractive index of the light supply member 40, it is necessary to replace the light supply member 40 for each type of tempered glass. . However, since this exchange operation is inefficient, by placing a liquid 90 having a refractive index almost the same as that of the tempered glass 200 between the light supply member 40 and the tempered glass 200, within the tempered glass 200, Laser light L can be incident efficiently.

As the liquid 90, for example, a mixed solution of 1-bromonaphthalene (n=1.64) and xylene (n=1.50) can be used. As the liquid 90, a mixed liquid of a plurality of silicone oils with different structures may be used. For example, the refractive index of dimethyl silicone oil (n = 1.38 to 1.41) and methylphenyl silicone oil (n = 1.43 to 1.57) can be adjusted by changing the chain length of each methyl group or phenyl group. A mixed solution of a plurality of silicone oils whose refractive indexes have been adjusted in this way may be used as the liquid 90. Since the refractive index of the liquid 90 is determined by each mixing ratio, the refractive index can be easily set to be the same as that of the tempered glass 200.

At this time, the refractive index difference between the tempered glass 200 and the liquid 90 is preferably ±0.03 or less, more preferably ±0.02 or less, and even more preferably ±0.01 or less. If there is no liquid 90, scattered light occurs between the tempered glass 200 and the light supply member, and data cannot be taken in a range of about 20 μm.

The thickness of the liquid 90 is preferably 10 μm or more because scattered light is suppressed to about 10 μm or less. In principle, the thickness of the liquid 90 may be any amount, but considering handling of the liquid, it is preferably 500 μm or less.

FIG. 41 is a diagram illustrating a scattered light image of the laser light L traveling at the interface between the light supply member 40 and the tempered glass 200. In Figure 41, point A is the surface scattered light of the tempered glass, and point D is the surface scattered light of the surface of the light supply member 40. Between point A and point D is scattered light from the liquid 90.

If the thickness of the liquid 90 is thin, point A and point D become almost the same point, resulting in surface scattered light obtained by adding the surface scattering of the tempered glass 200 and the surface scattering of the light supply member 40. As for the light supply member 40, if many pieces of tempered glass 200 are measured, a lot of surface damage occurs. When this happens, very large surface scattered light is generated.

However, as shown in FIG. 41, by maintaining the gap between the light supply member 40 and the tempered glass 200 by placing the liquid 90 therebetween, the surface scattered light of the light supply member 40 is prevented from being transmitted to the tempered glass 200. It is possible to prevent overlapping with surface scattered light near the outermost surface layer.

FIG. 42 is a diagram illustrating a structure for placing the liquid 90 between the light supply member 40 and the tempered glass 200. As shown in (a) of FIG. 42, a recessed portion 40x of 10 μm or more is formed on the surface of the light supply member 40 by polishing or etching, and the liquid 90 is filled into the recessed portion 40x, thereby forming the liquid. The thickness of (90) can be stably set to 10㎛ or more. In principle, the depth of the concave portion 40x may be any amount, but considering ease of processing, it is preferably 500 μm or less.

In addition, instead of forming the concave portion 40x on the surface of the light supply member 40, the surface of the light supply member 40 is formed using a thin film forming technique such as vacuum deposition or sputtering, as shown in (b) of FIG. 42. Alternatively, a land member 100 with a thickness of 10 μm or more may be formed of metal, oxide, resin, etc., and a land of the liquid 90 held in the land member 100 may be formed. By holding the liquid 90 with the land member 100, the thickness of the liquid 90 can be stably set to 10 μm or more. In principle, the thickness of the land member 100 may be any amount, but considering ease of processing, it is preferably 500 μm or less.

<Modification of the third embodiment>

In a modification of the third embodiment, an example different from FIG. 42 of the structural portion for placing the liquid 90 between the light supply member 40 and the tempered glass 200 is shown. In addition, in the modified example of the third embodiment, description of the same components as the already described embodiment may be omitted.

FIG. 43 is a diagram showing a second example of a structural portion for placing the liquid 90 between the light supply member 40 and the tempered glass 200. As shown in FIG. 43, the bottom of the concave portion 40x formed on the surface of the light supply member 40 does not need to be flat. The concave portion 40x is, for example, a spherical concave portion similar to a concave lens.

The depth of the concave portion 40x is, for example, 10 μm or more and 500 μm or less. As an example, when the depth of the concave part is 50 μm and the circumferential diameter of the concave part is 10 mm, the radius of curvature R is 200 mm.

The concave portion 40x can be easily formed as a spherical concave portion using the same manufacturing method as that of the concave lens. Since the liquid 90 filled in the concave portion 40x has the same refractive index as the light supply member 40, there is no lens effect due to the liquid 90 in the spherical concave portion, and the trace of the laser light and the scattered light are not affected. There is no effect on the image captured by the camera.

FIG. 44 is a diagram showing a third example of a structural portion for placing the liquid 90 between the light supply member 40 and the tempered glass 200. As shown in FIG. 44, a planar concave lens 43, which is a protrusion, is provided on the surface of the light supply member 40 on the tempered glass 200 side. The planar concave lens 43 is in contact with the tempered glass 200.

The planar concave lens 43 becomes part of the optical path of the laser light incident on the tempered glass 200 through the light supply member 40. In the planar concave lens 43, for example, a spherical concave portion 43x is formed. The depth of the concave portion 43x is, for example, 10 μm or more and 500 μm or less.

The light supply member 40 and the plane concave lens 43 are each formed as separate bodies, and are bonded to each other by an optical adhesive having substantially the same refractive index as the light supply member 40 and the plane concave lens 43.

The optical adhesive that bonds the light supply member 40 and the planar concave lens 43 is exposed to laser light for a long time, so it is desirable to use an adhesive with high durability.

In particular, when the wavelength of the light source is short and close to ultraviolet rays or ultraviolet rays, for example, at a wavelength of 500 nm or less, the optical adhesive deteriorates significantly, so it is necessary to bond the light supply member 40 and the plano-concave lens 43. As an optical adhesive, it is preferable to use an inorganic adhesive or low melting point glass. Alternatively, it is preferable to bond the light supply member 40 and the planar concave lens 43 using an optical contact that does not use an adhesive.

In the processing of general optical elements, the process of forming a prism formed only by a flat surface and the process of forming a lens forming a spherical surface require different technologies, and forming a prism with a spherical concave portion is difficult and requires many processes, resulting in increased productivity. This is bad, and the manufacturing cost becomes very expensive. That is, it is difficult to make the light supply member 40, which is a prism, and the plane concave lens 43 into an integrated structure.

However, the light supply member 40, which is a prism, and the plane concave lens 43 alone can be easily formed using each processing technology. Additionally, a glass plate having substantially the same refractive index as the light supply member 40 and the plane concave lens 43 may be inserted between the light supply member 40 and the plane concave lens 43. This glass plate can be used to attach the light supply member 40 to the evaluation device main body.

In this case, as the optical adhesive for bonding the light supply member 40 and the glass plate, and the optical adhesive for bonding the glass plate and the plano-concave lens 43, if the wavelength of the light source is short and is close to ultraviolet rays or ultraviolet rays, an inorganic adhesive or It is preferable to use low melting point glass. Alternatively, it is preferable to bond the light supply member 40 and the glass plate, and the glass plate and the planar concave lens 43 using an optical contact or the like that does not use an adhesive.

FIG. 45 is a diagram showing a fourth example of a structural portion for placing the liquid 90 between the light supply member 40 and the tempered glass 200. As shown in FIG. 45, a flat outer edge portion 43e may be formed around the planar concave lens 43. In the structure shown in FIG. 45, the flat outer edge 43e becomes a surface in contact with the tempered glass 200, so that when the tempered glass 200 is brought into contact with the light supply member 40, it can be parallelized with high precision. Also, damage such as scratches to the tempered glass 200 can be eliminated.

FIG. 46 is a diagram showing a fifth example of a structural portion for placing the liquid 90 between the light supply member 40 and the tempered glass 200. As shown in Figure 46, the light supply member 40 and the planar concave lens 43 are not fixed with an optical adhesive, but a support that can be removed with a liquid having the same refractive index as the liquid 90 interposed therebetween. You may use (44) to secure it from the outer side so that it does not move.

By configuring the support body 44 to be openable and closed using a spring or the like, only the planar concave lens 43 can be easily replaced. For example, when damage or scratches occur on the planar concave lens 43 due to contact with the tempered glass 200, or when changing to a planar concave lens 43 with a concave portion of a different shape, etc. It is sufficient to manufacture a plurality of lenses 43 and replace them.

Additionally, the shape and structure of the support body 44 may be any as long as the planar concave lens 43 can be held in an exchangeable manner.

FIG. 47 is a diagram showing a sixth example of a structural portion for placing the liquid 90 between the light supply member 40 and the tempered glass 200. As shown in FIG. 47, a groove 43y through which the liquid 90 is discharged may be formed in the flat outer edge 43e formed around the planar concave lens 43. The groove 43y is in communication with the concave portion 43x.

When the liquid 90 is dropped into the concave portion 43x and the tempered glass 200 is placed thereon, air bubbles may remain in the concave portion 43x. By providing a groove 43y for discharging the liquid 90 around the concave portion 43x, when the liquid 90 is dropped into the concave portion 43x and the tempered glass 200 is placed, the groove 43y ), bubbles are also discharged together with the liquid 90, making it difficult to leave bubbles in the concave portion 43x.

As shown in FIG. 48, a groove 40y communicating with the concave portion 43x may be formed on the surface of the light supply member 40 on the side in contact with the tempered glass 200. As in the case of FIG. 47, by providing a groove 40y for discharging the liquid 90 around the concave portion 40x, the liquid 90 is dropped into the concave portion 40x and the tempered glass 200 is formed. When placed, air bubbles are discharged along with the liquid 90 from the groove 40y, making it difficult to leave air bubbles in the concave portion 40x.

43 to 48, the intersecting curves shown in the concave portions 40x or 43x and the vertical lines drawn on the side of the planar concave lens 43 are shown for convenience to make the drawing easier to see, and are not actually It does not indicate lines (thin grooves, protrusions, etc.).

In addition, in the above, the concave portion (40x or 43x) is explained as a concave portion on a spherical surface, but the concave portion (40x or 43x) is not limited to a spherical shape and may be any surface provided with a curved portion. The concave portion (40x or 43x) may be, for example, an aspherical concave shape. Additionally, the groove shape and number of grooves 40y and 43y may be set arbitrarily.

<Fourth Embodiment>

In the fourth embodiment, an example of an evaluation method considering the refractive index of tempered glass is shown. Additionally, in the fourth embodiment, descriptions of the same components as those in the already described embodiment may be omitted.

The equation for calculating the stress St from the polarization phase difference Rt at the depth D of the laser beam is C, the photoelastic constant of the tempered glass, and the angle formed by the laser beam with the surface 210 of the tempered glass 200, that is, the incident complement angle (refraction angle). If Ψ is used, it becomes as shown in Equation 8 (Equation 8) below.

In Equation 8, the last term of Ψ is a correction of the contribution to the laser light of birefringence due to stress. That is, the internal stress due to strengthening of the tempered glass 200 is parallel to the surface 210, while the laser light is incident on the surface 210 at an angle. Therefore, correction of the contribution of birefringence due to stress to the laser light is necessary, and the last Ψ term in Equation 8 becomes the correction. In addition, although St is used in this equation, since the coordinate system of the stress distribution is different from equation 1, a separate symbol is used for convenience.

FIG. 49 is a diagram explaining that laser light L is incident on the tempered glass 200. In Figure 49, the surface of the tempered glass 200 is in contact with the upper surface of the light supply member 40, and the surface of the tempered glass 200 is in contact with the upper surface of the light supply member 40 and the upper surface of the light supply member 40. It is located at the xyz coordinates with the XZ plane. Then, the laser light L enters the incident end surface of the light supply member 40, passes through the upper surface of the light supply member 40 and the surface boundary of the tempered glass 200, and enters the tempered glass 200. . The imaging element 60 captures the laser trace (trajectory of the laser beam L) from below at an inclination of 45°.

FIG. 50 is a diagram explaining an image of a laser trace taken from the position of the imaging device 60 in FIG. 49. The laser trace on the image captured by the imaging device 60 is Cpass, the length is Pc, the angle of the laser trace on the image is χ, the horizontal distance on the image is Lx, and the vertical distance on the image is V. In the evaluation device 1, image analysis is performed on the image of the laser beam L (more precisely, scattered light from the laser beam L) from the imaging device 60, and the stress in the tempered glass 200 is finally measured.

However, since the image acquired by the imaging device 60 is an image from below an inclination of 45°, the length Pc of the laser trace Cpass on the image and the actual length of the laser beam L cannot be said to be the same, and furthermore, the length Pc of the laser trace Cpass on the image cannot be said to be the same. The angle χ is also not the actual incident complement angle Ψ. Therefore, in order to determine the stress from the image of the laser beam L using Equation 8, a conversion equation is needed to determine the actual distance P of the laser beam L and the incident complement angle Ψ.

FIG. 51 is a diagram explaining definitions of the angle and length of the laser light in the light supply member 40 or tempered glass 200 of FIG. 49. Here, we consider a cuboid whose vertices are abcdefgh. Let the length of side bf be Lx, the length of side ab be H, and the length of side fg be D. D is equal to the depth of the light supply member 40 or the tempered glass 200. In Figure 51, the laser beam L is advancing from vertex c to vertex e, and Pass indicates the trajectory of the laser beam L.

The upper surface abfe is assumed to be parallel to the upper surface of the light supply member 40 in FIG. 49 and the surface of the tempered glass 200. Let ce, the length of the trajectory pass of the laser light, be P, and Ψ be the incident angle of incidence on the surface of the tempered glass 200. Additionally, the surface acge is equivalent to the incident surface of the laser light L.

Figure 52 is a top view, front view, and side view of Figure 51. The trajectory seen from the upper surface of the laser light L is called Upass, the length is Pu, the trace seen from the front is called Fpass, the length is called Pf, the trace seen from the side is called Lpass, and the length is called Pl. The angle ω of the trajectory Lpass of the laser light L seen from the side becomes the angle of incidence of the laser light L. ϕ is the Z-axis rotation angle of the laser beam L, and θ is the Y-axis rotation angle.

In Figure 51, in the case of H=D, ω is 45°, and the incident surface of the laser light L is 45°. In the case of H=D, in Figure 52, the Z-axis rotation angle ϕ and the Y-axis rotation angle θ of the laser light L are equal, so in order to set the incident surface of the laser light L in the tempered glass 200 to 45°, the laser light It can be seen that the rotation angles of the Z-axis and Y-axis of L can be made equal.

In addition, the length P of the laser light trajectory Pass is expressed in the following equation 9 (Equation 9).

In addition, if Lx is a unit length, for example, 1, D, H, and Pu are obtained from ϕ and θ, and the incident complement angle Ψ of the laser light on the tempered glass surface is the angle of Pass and Upass, so from these, the laser The length P of the light L and the incident complement angle Ψ with respect to the surface of the tempered glass 200 are easily obtained.

(If the refractive index of the light supply member np = the refractive index ng of the tempered glass)

If the refractive index np of the light supply member 40 and the refractive index ng of the tempered glass 200 are the same, the angles of these lasers and their relationships are the same among the light supply members 40 and the tempered glass 200. For example, the Y-axis rotation angle of the laser in the light supply member 40 or the tempered glass 200 is θ = 15°, the Z-axis rotation angle is ϕ = 15°, and the refractive index of the tempered glass 200 is ng = 1.516. , if the refractive index of the light supply member 40 is the same as that of the tempered glass, np = 1.516, then the angle of incidence in the tempered glass 200 is ω = 45°, and the angle of incidence Ψ = 14.5°.

From Figure 50, if the incident plane is 45°, the image is viewed perpendicular to the incident plane, and the distance Pc of the laser trajectory Cpass shown in Figure 50 becomes the same as the distance P of the actual laser trajectory Pass, The actual depth D can be obtained from the depth V on the image using Equation 10 (Equation 10) below.

From these, it is possible to calculate the stress of the tempered glass from the image of the imaging device 60 of the laser beam.

(If the refractive index np of the light supply member 40 ≠ the refractive index ng of the tempered glass 200)

The above explanation is a case where the light supply member 40 and the tempered glass 200 have the same refractive index, and the laser light proceeds without being refracted at the interface between the light supply member 40 and the tempered glass 200, and the light supply member 40 and the tempered glass 200 have the same refractive index. The laser light in (40) and tempered glass (200) is parallel. However, in reality, the refractive index of the light supply member 40 and the tempered glass 200 are not necessarily the same.

If the refractive index of the light supply member 40 and the tempered glass 200 are different, the Z-axis rotation angle of the laser light does not change, and only the Y-axis rotation angle changes. Therefore, when the refractive index of the light supply member 40 and the tempered glass 200 are the same, even if the incident surface of the laser light in the tempered glass 200 is 45°, the refractive index of the tempered glass 200 is lower than the light supply member 40. ), the incident surface of the laser light on the tempered glass 200 deviates from 45°. In that case, the distance Pc of the laser trajectory Cpass shown in Figure 50 is different from the distance P of the actual laser trajectory Pass (Pc≠P), and equation 10 also does not hold.

It is difficult to directly measure the incident angle Ψ and the incident angle ω of the laser light in tempered glass. So, consider the trajectory of the laser light when the refractive index np of the light supply member 40 and the refractive index ng of the tempered glass 200 are different.

In addition, since the laser light enters the light supply member 40 from the air, the angle before the laser light enters the light supply member 40 and the laser beam at the incident end surface of the light supply member 40 where the laser light enters. The laser light is refracted by the angle formed with the light and enters the light supply member 40. Therefore, considering the incident angle of incidence before the laser beam enters the light supply member 40 and the angle of the incident end surface of the light supply member 40, the necessary incident angle of incidence and angle of incidence of the laser light in the tempered glass 200 are considered. .

In order to distinguish ϕ and θ in FIG. 52 from those in the tempered glass 200, ϕg and θg in the tempered glass 200 and ϕp and θp in the light supply member 40 are incident on the light supply member 40. The former is called ϕL and θL. In addition, the Z-axis rotation angle β and the Y-axis rotation angle α of the incident end surface of the light supply member 40 where the laser is incident are referred to as β. Additionally, the refractive index of the light supply member 40 is assumed to be np, and the refractive index of the tempered glass 200 is assumed to be ng.

If np and ng are different, or β and α are different from ϕL and θL, then the Z-axis rotation angles, ϕL, ϕp, β, and ϕp, ϕg, and the Y-axis rotation angles, θL, θp, α, and θp. , θg are, respectively, Snell's law is established, the angle before incident of the laser light on the light supply member 40, ϕL, θL, the angle of the incident end surface of the light supply member 40, α, β, and the refractive index ng. If , np is known in advance, the rotation angles, ϕg, θg, incident complement angle Ψ, and incident surface angle ω, which are parameters necessary for measurement, of the laser light in the tempered glass 200 can be easily calculated.

Here, the rotation angles ϕL and θL before the laser light enters the light supply member 40, the rotation angle β and α of the incident end surface of the light supply member 40 where the laser light enters, and the refractive index of the light supply member 40. np is determined in the device design and is known. The refractive index of the tempered glass 200 can be determined using a general refractive index measuring device.

Therefore, from the refractive index of the tempered glass 200 measured by other means, ϕL, θL, α, β, np determined in the device design, and the refractive index of the tempered glass 200, the laser in the tempered glass 200 ϕg and θg of the light, incident complementation angle Ψ, and incident angle ω are obtained, and from the images Pc and χ of the laser light imaging device 60, a conversion formula for the incident complementation angle Ψ and incidence angle ω of the laser light in the tempered glass 200 is obtained. , it is possible to measure the stress distribution in the tempered glass from Equation 8. Specific examples are shown below.

Figure 53 is a conceptual diagram of laser light traveling through a light supply member and tempered glass. In addition, although it is actually a three-dimensional angle, it is shown two-dimensionally in FIG. 53 for convenience. Figure 54 is a conceptual diagram of a laser beam traveling through tempered glass, and reference numeral 215 schematically shows the observation surface observed from the imaging device 60 in a crepe shape.

53 and 54, θL is the angle formed between the laser light incident on the light supply member 40 from the laser light source 10 and the normal line of the incident surface 40a of the light supply member 40 (laser side). . In addition, θ _P1 is the angle formed between the laser light incident on the light supply member 40 from the laser light source 10 and the normal line of the incident surface 40a of the light supply member 40 (on the light supply member 40 side), θ _P2 is the angle formed between the laser light incident on the tempered glass 200 from the light supply member 40 and the normal line of the exit surface 40b of the light supply member 40 (on the light supply member 40 side). Additionally, since the incident surface 40a of the light supply member 40 and the exit surface 40b of the light supply member 40 are not actually perpendicular, it cannot be said that θ _P1 + θ _P2 = 90°.

In addition, θg is the angle formed between the laser light incident on the tempered glass 200 from the light supply member 40 and the normal line of the exit surface 40b of the light supply member 40 (on the tempered glass 200 side), and Ψ is This is the incident complement angle (90-θg) formed by the surface 210 (evaluation surface) of the tempered glass 200 and the laser light in the tempered glass 200. Additionally, χ is the slope of the laser light observed from the imaging device 60. Additionally, when thinking of θ, Ψ, etc. in three dimensions, they may be divided as shown in FIG. 52.

The incident complement angle Ψ can be obtained, for example, according to the flowchart shown in FIG. 55. That is, first, in step S701, θ _P1 is derived from θL and np. θ _P1 can be obtained from θL and np using Snell's equation.

Next, in step S702, θ _P2 is derived from θ _P1 . θ _P2 can be obtained from θ _P1 based on the shape of the light supply member 40. Next, in step S703, θg is derived from θ _P2 , np, and ng. θg can be obtained from θ _P2 , np, and ng using Snell's equation.

Next, in step S704, Ψ is derived from θg. Ψ can be obtained from θg by geometric calculation. That is, Ψ=90-θg.

Ideally, the refractive index np of the light supply member 40 and the refractive index ng of the tempered glass 200 are the same, but there are many types of tempered glass and their refractive indices are different. However, the optical glass forming the light supply member 40 is not necessarily a glass with exactly the same refractive index as the tempered glass.

For example, the most commonly used optical glass S-BSL7 (manufactured by Ohara) has np=1.516, below is np=1.487 for S-FSL5 (manufactured by Ohara), and above is np=1.5317 for S-TIL6 (manufactured by Ohara). etc. are available.

Therefore, when measuring tempered glass with a refractive index in a certain range, it is necessary to measure using the light supply member 40 made of optical glass with a refractive index close to that range. For example, when the refractive index of tempered glass is ng = 1.51, the incident angle of incidence Ψ in the tempered glass is 13.7°, and the angle of incidence ω is 43°. From this, a conversion formula can be obtained and the exact stress can be obtained using Equation 8.

In addition, it is also possible to calculate the refractive index ng of the tempered glass 200 from the angle χ of the laser image of the imaging device 60. That is, the refractive index ng of the tempered glass 200 may be derived based on the image of the laser light acquired by the imaging device 60.

Specifically, first, in step S711 of the flowchart shown in FIG. 56, the relationship between the incident complement angle Ψ and the angle xi shown in FIG. 54 is derived. The relationship between the incident complement angle Ψ and the angle χ can be obtained by geometric calculation. Next, in step S712, the angle χ is measured with the imaging device 60 (camera).

Next, in step S713, the incident complement angle Ψ is obtained from the relationship derived in step S711 using the angle xi measured in step S712. Additionally, θg=90-Ψ can be obtained and ng can be derived from the known θ _P2 , np, and θg using Snell's equation.

In this way, the refractive index ng of the tempered glass 200 is obtained from the angle χ of the laser image of the imaging device 60, and a conversion equation is obtained based on the refractive index ng of the tempered glass 200, so that the tempered glass 200 It is also possible to measure the stress distribution.

However, an error occurs in the value of the refractive index ng of the tempered glass 200 derived by the method of FIG. 56 due to the inclination, etc. when the tempered glass 200 is mounted on the light supply member 40. Therefore, when it is desired to stably measure the stress distribution in the tempered glass with high precision, it is desirable to measure the refractive index ng of the tempered glass 200 in advance by another method (measurement with a refractive index measuring device, etc.).

Additionally, it is also possible to correct the incident complement angle Ψ from the angle χ of the laser image of the imaging device 60. For example, in step S711 of the flowchart shown in FIG. 57, the relationship between the incident complement angle Ψ and the angle xi is derived in the same manner as in the case of FIG. 56, and in step S712, the relationship between the incident angle Ψ and the angle xi is derived in the same manner as in the case of FIG. 56, and the imaging element 60 Measure the angle χ with Then, in step S714, the incident complement angle Ψ is derived from the relationship derived in step S711 using the angle χ measured in step S712. By applying the incident complement angle Ψ derived in step S714 to Equation 8, the exact stress can be obtained.

Additionally, when the value of the refractive index ng of the tempered glass 200 is known in advance, it is also effective to design the optimal light supply member 40 by considering the value of the refractive index ng of the tempered glass 200.

The incident angle Ψ and the incident angle ω in the tempered glass 200 can be known by calculation, but if the difference between the refractive index ng of the tempered glass 200 and the refractive index np of the light supply member 40 increases, the angle of incidence Ψ increases from 45°. The discrepancy increases. Accordingly, if the depth of focus of the lens of the imaging device 60 is exceeded, the focus is shifted, spatial resolution deteriorates, and correct stress distribution cannot be measured.

For example, in the case of the refractive index ng = 1.49 of the tempered glass 200, the incident angle of incidence Ψ of the laser light in the tempered glass 200 is 10.3°, and the angle of incidence ω is 35°. In this case, the incident complement angle Ψ can be corrected by calculation, but the incident angle ω is shifted by as much as 10° from 45°, so it is impossible to maintain measurement accuracy only through calculation correction.

Therefore, the angle of the surface of the light supply member 40 on which the laser light is incident is set so that the surface of the laser light incident on the tempered glass 200 is 45 ± 5° with respect to the surface of the tempered glass 200. desirable.

For example, when the distance of the laser trace is 300 μm and the angle of incidence ω is shifted by 10°, the difference in distance from the imaging device 60 to the laser light in the tempered glass 200 is as much as 52 μm, so that the imaging device ( If the depth of focus of the lens connecting the image to the image sensor 60 is exceeded, the laser trace imaged by the imaging device 60 is not uniformly focused over the entire distance, thereby deteriorating measurement accuracy.

So, for example, in step S721 of the flowchart shown in FIG. 58, the value of the refractive index ng of the target tempered glass 200 is obtained. Next, in step S722, the refractive index ng of the tempered glass 200 and the refractive index np of the light supply member 40 are fixed, and θL, which does not change the surface through which the laser light passes and the observation surface, is determined.

For example, in the case of the refractive index ng = 1.49 of the tempered glass 200, the Y rotation angle θL = 15° and the Z rotation angle ϕL = 15° of the laser light are the same, and the rotation of the incident end surface of the light supply member 40 If the angle β = 15° and the Z rotation angle α = 24.5°, in the tempered glass 200, the laser light can have an incident complement angle of 14.4° and an incident surface angle of 44.8°, which is almost the designed angle. Therefore, measurement accuracy does not deteriorate.

By manufacturing the light supply member 40 of this specification, installing the laser light source 10 as is, and only replacing the light supply member 40, the refractive index ng is significantly different from the refractive index np of the light supply member 40. It becomes possible to accurately measure the stress distribution of the tempered glass 200. In addition, in order to eliminate light returning to the laser light source 10, when the tempered glass 200 and the surface on which the laser light enters the light supply member 40 are slightly shifted (about 0.5 to 1°), Equation 8 It can be corrected with

<Fifth Embodiment>

In the fifth embodiment, an example of an evaluation device provided with a function of measuring glass thickness is shown. Additionally, in the fifth embodiment, descriptions of the same components as those in the already described embodiment may be omitted.

In thin plate-shaped tempered glass, compressive stress is formed on the surface for strengthening. In doing so, tensile stresses are generated internally to balance the stresses as a whole.

Figure 59 is a diagram illustrating the stress distribution in the depth direction of tempered glass. In response to the compressive stress formed on the surface, a tensile stress occurs in the central part, and in principle, the stress as a whole becomes zero. That is, the integral value (stress energy) of the stress distribution from the surface to the back surface in the depth direction is 0.

To use another expression, the integral value of the compressive stress at the surface (compressive energy) and the integral value of the tensile stress at the center (tensile energy) become equal. Additionally, in a normal chemical strengthening process, since chemical strengthening of both sides of the glass is performed under the same conditions, the stress distribution is symmetrical with respect to the center of the glass. Therefore, the integral from the surface to the midpoint of the glass in the depth direction also becomes 0.

In the evaluation device 1, the stress value is obtained from the differential value of the phase value of the change in glass depth and scattered light luminance (for example, FIG. 7) and the photoelastic constant (see the first embodiment). Therefore, the phase of the change in glass depth and scattered light luminance in Figure 7 is the same as the integrated value of the stress value. That is, in Figure 7, the phase value of the center point of the tempered glass and the outermost surface of the tempered glass are the same.

In the evaluation device 1, when laser light is diffusely reflected on the outermost surface of the tempered glass and diffusely reflected light is generated, there is a drawback in that the phase value of the change in the brightness of the scattered light on the outermost surface of the tempered glass cannot be accurately measured.

Therefore, the phase value of the center point of the tempered glass is used to determine the phase value of the change in the brightness of scattered light on the outermost surface, or to correct it. As a result, for example, it is possible to accurately measure the stress value and stress distribution at the outermost surface of the tempered glass and near the outermost surface. Additionally, if the measured phase value does not reach the center of the tempered glass, the measured phase value may be extrapolated to the center of the tempered glass to be the phase value of the center of the tempered glass.

In this way, when the thickness of the tempered glass is known, based on the calculated stress distribution and the thickness of the tempered glass, the phase change amount of the outermost surface of the tempered glass where the stress is balanced can be estimated, and the surface stress value can be corrected. .

Figure 60 is a diagram illustrating an evaluation device equipped with a glass thickness measuring device. The evaluation device 3 shown in FIG. 60 has a configuration in which a glass thickness measuring device 120 is installed in the evaluation device 1.

The glass thickness measuring device 120 has a laser light source, a light receiving unit, and a calculation unit (not shown). The laser light Lg emitted from the laser light source of the glass thickness measuring device 120 is reflected from the front surface 210 and the back surface 220 of the tempered glass 200 and is received by the light receiving unit of the glass thickness measuring device 120. . The calculation unit of the glass thickness measuring device 120 measures the thickness of the tempered glass 200 based on the light received by the light receiving unit. As the glass thickness measuring device 120, for example, a commercially available glass thickness gauge can be used.

In the evaluation device 3, the phase value in the depth direction from the surface of the tempered glass 200 is determined by the evaluation device 1 from the change in the brightness of scattered light in the tempered glass 200 caused by the laser light from the laser light source 10. It can be measured. At the same time, the evaluation device 3 can measure the thickness of the tempered glass 200 using the glass thickness measuring device 120.

From the thickness of the tempered glass 200 measured by the glass thickness measuring device 120 and the phase value in the depth direction, the phase value of the center of the tempered glass 200 can be obtained by measurement or extrapolation. Then, based on the phase value, it can be set as the phase value of the outermost surface of the tempered glass 200, or it can be corrected, and the stress distribution can be obtained from the phase value in the depth direction in which the outermost surface has been corrected.

In this way, in the evaluation device 3 provided with means for measuring the thickness of the tempered glass, the stress distribution and the thickness of the tempered glass are measured, and based on the measured thickness of the tempered glass, the phase change amount of the outermost surface of the tempered glass can be estimated.

<Modified example of determination of phase value>

Regarding the determination of the phase value of the change in the scattered light luminance of the outermost surface, the following modifications are possible.

As described above, in the evaluation device 1, when the laser light is diffusely reflected from the outermost surface of the tempered glass 200 and diffusely reflected light is generated, the phase value of the change in the brightness of the scattered light on the outermost surface of the tempered glass 200 is accurately determined. There are flaws that cannot be measured. In order to compensate for the shortcoming, the following method may be further used.

First, two sets of the laser light source 10, the polarization member 20, and the polarization phase difference variable member 30 are prepared, and the laser light L and L' are separated from two other angles θ _s1 and angle θ' _s1. You can hire me. At that time, the scattered light from the laser light L and the scattered light from the laser light L' are measured separately. Among the two sets of laser beams, when the laser beam incident from a smaller angle is used, the error in the phase value of the outermost surface of the tempered glass 200 due to the influence of diffuse reflection on the surface of the tempered glass 200 is smaller. On the other hand, there are cases where it is not possible to measure the core of the tempered glass 200. Therefore, the phase value of the outermost surface of the tempered glass 200 is determined by measurement using laser light incident from a smaller angle, and the result is the phase value of the outermost surface of measurement using laser light incident from a larger angle. By doing so, the measurement precision is improved, and in some cases, it is possible to measure even the deep portion of the tempered glass 200.

Second, in order to suppress diffuse reflection of the laser light on the outermost surface of the tempered glass 200, a step of cleaning the surface of the tempered glass 200 using a cleaning system may be taken before step S601. The cleaning system may be an operation such as cleaning or wiping using a wet or dry cleaner.

Third, when a means for calculating the value of DOL_zero is provided, DOL_zero (front) on the front 210 side of the tempered glass 200 and DOL_zero (back) on the back 220 side are used, as follows: The phase of the outermost surface on the surface 210 side of the tempered glass 200 may be estimated as follows.

That is, the sum of DOL_zero (surface) and DOL_zero (back surface) becomes the thickness of the tempered glass 200, so the midpoint becomes the midpoint of the glass. Since the integral value of the stress from the outermost surface of the tempered glass to this midpoint is zero, the phase value of the center point of the tempered glass and the outermost surface of the tempered glass are the same. In this way, the phase value of the outermost surface of the glass may be obtained without separately measuring the glass plate thickness. Additionally, the position of the origin of the phase may be calculated by extrapolation so that the outermost surface of the tempered glass becomes the phase at the midpoint of the glass.

Additionally, DOL_zero (back surface) is the length measured from the surface 210 side of the tempered glass 200 at the point where the stress value on the back surface 220 side becomes zero. Additionally, in order to measure DOL_zero (back surface) with high precision, liquid 90 may be installed on the back surface 220 side. By doing this, diffuse reflection on the surface on the back side 220 side is suppressed. Additionally, a light blocking function such as a light blocking plate may be provided between the glass and the camera to prevent light from entering from the back side.

Fourth, in the fifth embodiment, when a means for calculating the value of DOL_zero is further provided, DOL_zero (front) on the glass surface 210 side and DOL_zero (back) on the back surface 220 side are used. Therefore, the phase of the outermost surface on the glass surface 210 side may be estimated as follows. In other words, the sum of DOL_zero (surface) and DOL_zero (back surface) becomes the glass thickness, so by determining the position of the outermost surface so that this sum matches the value measured by the glass thickness measuring device, the overall stress distribution can be obtained with high accuracy. . The phase of the outermost surface is estimated by extrapolating the phase to the position of the outermost surface.

Fifth, after the phase change calculation process (S405), a process may be performed to evaluate whether the origin position of the calculated phase change is reasonable. At that time, a display may be used to display the origin position of the phase change calculated in S405 at the corresponding position of the image obtained in the imaging step (S403), and the measurer may visually evaluate it. By doing this, if the origin position of the phase change is greatly shifted due to noise during measurement or light scattering due to dust, air bubbles, or extraneous light, it becomes possible to easily determine re-measurement. Additionally, if disturbance light is the cause, the position of the laser light source may be moved.

Although the preferred embodiment has been described in detail above, it is not limited to the above-described embodiment, and various modifications and substitutions can be made to the above-described embodiment without departing from the scope described in the patent claims.

For example, in each of the above embodiments, the light source is described as a component in the evaluation devices 1 and 2, but the evaluation devices 1 and 2 may be configured without a light source. As a light source, the user of the evaluation devices 1 and 2 can prepare and use an appropriate light source.

This international application claims priority based on Japanese Patent Application No. 2018-031579 filed on February 26, 2018, and the entire contents of Japanese Patent Application No. 2018-031579 are incorporated into this international application.

1, 1A, 1B, 1C, 1D, 1E, 2, 3: Evaluation device
10, 11, 12: Laser light source
15: light source
20, 55: Polarization member
25, 40, 41: Absence of light supply
30, 30A: Polarization phase difference variable member
35, 42: Light extraction member
40a: Incident surface of light supply member
40b: exit surface of the light supply member
40x, 43x: concave part
40y, 43y: Home
43: Plane concave lens
43e: outer edge
44: support
45, 50, 50A: Light conversion member
60, 60A, 65: imaging device
70, 75: Calculation unit
80, 80A 81, 82: Optical wavelength selection member
90: liquid
100: Land absence
120: Glass thickness measuring device
200: Tempered glass
210: Surface of tempered glass
215: observation surface
220: The back side of tempered glass
250: Incident surface of laser light
301: digital data memory circuit
302: clock signal generation circuit
303: DA converter
304: Voltage amplification circuit
310: Polarization phase difference generating material
311, 313: Fixed jig
312: Piezo element
701: means for measuring luminance change
702: Phase change calculation means
703: Stress distribution calculation means
704: Means of measuring physical quantities
751: Position measurement means
752: Stress distribution calculation means
753: synthetic means

Claims (55)

a polarization phase difference variable member that changes the polarization phase difference of the laser light by more than one wavelength with respect to the wavelength of the laser light;
an imaging element that captures scattered light emitted when the laser light with the variable polarization phase difference is incident on the tempered glass multiple times at predetermined time intervals to acquire multiple images;
Measuring a periodic luminance change of the scattered light using the plurality of images, calculating a phase change of the luminance change, and calculating a stress distribution in the depth direction from the surface of the tempered glass based on the phase change; An evaluation device for tempered glass, characterized by having a calculation unit that measures a physical quantity related to the strength of the tempered glass using the plurality of images. According to paragraph 1,
An evaluation device for tempered glass, wherein the calculation unit measures luminance of the scattered light as the physical quantity. According to paragraph 1,
The plurality of images have a speckle pattern,
The evaluation device for tempered glass, wherein the calculation unit measures a dispersion value of luminance of the speckle pattern as the physical quantity. According to paragraph 1,
An evaluation device for tempered glass, wherein the calculation unit measures a refractive index of the tempered glass as the physical quantity. According to any one of claims 1 to 4,
A first optical wavelength selecting member having a relatively high transmittance of the wavelength of the laser light and a second optical wavelength selecting member having a relatively low transmittance of the wavelength of the laser light are switched on an optical path through which the laser light enters the imaging device. Possibly inserted,
The calculation unit may include, as the physical quantities, a first luminance of the scattered light when the first light wavelength selecting member is inserted on the optical path, and the scattered light when the second light wavelength selecting member is inserted on the optical path. An evaluation device for tempered glass, characterized in that the second luminance is measured and the ratio of the first luminance and the second luminance is calculated. According to any one of claims 1 to 4,
When the laser light in the first wavelength band is incident, the first optical wavelength selecting member that transmits the laser light in the first wavelength band and the second optical wavelength selecting member that transmits the light in the second wavelength band are A first optical wavelength selection member is selected, and when laser light in the second wavelength band is incident, the second optical wavelength selection member is switchably inserted onto the optical path through which the laser light is incident on the imaging device. become,
The calculation unit may include, as the physical quantities, the first luminance of the scattered light when the laser light in the first wavelength band is incident and the first optical wavelength selection member is inserted into the optical path, and the laser light in the second wavelength band. An evaluation device for tempered glass, characterized in that the second luminance of the scattered light is measured when light is incident and the second light wavelength selection member is inserted into the optical path. According to any one of claims 1 to 4,
An evaluation device for tempered glass, wherein the calculation unit measures the physical quantity in a plurality of regions in the depth direction from the surface of the tempered glass. According to any one of claims 1 to 4,
An evaluation device for tempered glass, wherein the polarization phase difference variable member is a liquid crystal element. According to any one of claims 1 to 4,
An evaluation device for tempered glass, wherein the polarization phase difference variable member has a photoelastic constant multiplied by Young's modulus of 0.1 or more and is a transparent member that generates the polarization phase difference by applying pressure. According to clause 9,
An evaluation device for tempered glass, wherein the transparent member is quartz glass or polycarbonate. According to any one of claims 1 to 4,
The position of the minimum beam diameter of the laser light is within the ion exchange layer of the tempered glass,
An evaluation device for tempered glass, wherein the minimum beam diameter is 20 μm or less. According to any one of claims 1 to 4,
An evaluation device for tempered glass, wherein the incident surface of the laser light incident on the tempered glass is 45 ± 5° with respect to the surface of the tempered glass. According to clause 12,
It has a light supply member that causes the laser light with the variable polarization phase difference to enter the tempered glass, which is the object to be measured, at an angle with respect to the glass surface,
The angle of the surface of the light supply member on which the laser light is incident is set so that the surface of the laser light incident on the tempered glass is 45 ± 5° with respect to the surface of the tempered glass. Evaluation device. According to any one of claims 1 to 4,
It has a light supply member that causes the laser light with the variable polarization phase difference to enter the tempered glass, which is the object to be measured, at an angle with respect to the glass surface,
A liquid having a refractive index difference from that of the tempered glass of 0.03 or less is provided between the light supply member and the tempered glass,
An evaluation device for tempered glass, characterized in that the thickness of the liquid is 10 μm or more and 500 μm or less. According to clause 14,
A concave portion having a depth of 10 μm or more and 500 μm or less is formed on the surface of the light supply member in contact with the tempered glass,
An evaluation device for tempered glass, wherein the liquid is filled in the concave portion. According to clause 14,
A protrusion in contact with the tempered glass is provided on the surface of the light supply member,
The protrusion becomes a part of the optical path of the laser light incident on the tempered glass through the light supply member,
A concave portion having a depth of 10 μm or more and 500 μm or less is formed on the side of the protrusion that is in contact with the tempered glass,
An evaluation device for tempered glass, wherein the liquid is filled in the concave portion. According to clause 16,
An evaluation device for tempered glass, wherein the protrusion is exchangeably held on a surface of the light supply member. According to clause 16,
An evaluation device for tempered glass, wherein a flat outer edge is formed around the concave portion, and the flat outer edge becomes a surface in contact with the tempered glass. According to clause 15,
An evaluation device for tempered glass, wherein the concave portion is made of a surface having a curved portion. According to clause 15,
An evaluation device for tempered glass, wherein a groove for discharging the liquid is formed around the concave portion. According to clause 15,
When the refractive index of the light supply member and the refractive index of the tempered glass are different,
Obtaining the refractive index of the tempered glass,
From the relationship between the trajectory of the laser light in the tempered glass obtained based on the refractive index of the tempered glass and the image of the laser light acquired by the imaging device, the incident complement angle when the laser light is incident on the tempered glass is derived,
An evaluation device for tempered glass, characterized in that the stress distribution in the depth direction from the surface of the tempered glass is corrected based on the value of the incident complement angle. According to clause 21,
An evaluation device for tempered glass, wherein the refractive index of the tempered glass is derived based on an image of the laser light acquired by the imaging device. According to any one of claims 1 to 4,
When the thickness of the tempered glass is known, based on the calculated stress distribution and the thickness of the tempered glass, estimate the phase change amount of the outermost surface of the tempered glass where the stress is balanced, and correct the surface stress value. Characterized by an evaluation device for tempered glass. According to any one of claims 1 to 4,
Provided with means for measuring the thickness of the tempered glass,
An evaluation device for tempered glass, characterized in that it measures the stress distribution and the thickness of the tempered glass, and estimates the amount of phase change of the outermost surface of the tempered glass based on the measured thickness of the tempered glass. According to any one of claims 1 to 4,
An evaluation device for tempered glass, wherein the laser light in the tempered glass satisfies the conditions of total reflection on the emission side of the tempered glass. According to any one of claims 1 to 4,
a second light supply member for incident light from a second light source into a surface layer having a compressive stress layer of the tempered glass;
a light extraction member that emits light propagated within the surface layer to the outside of the tempered glass;
Two types of light components included in the light emitted through the light extraction member and vibrating parallel and perpendicular to the interface between the tempered glass and the light extraction member are two types of light, each having two or more bright lines. A light conversion member that converts into linear heat,
a second imaging element for imaging the two types of bright line rows;
It has position measuring means for measuring the positions of two or more bright lines of each of the two types of bright line rows from the image obtained by the second imaging device,
The calculation unit calculates the stress distribution in the first region in the depth direction from the surface of the tempered glass corresponding to the two types of light components calculated based on the measurement results of the position measuring means, and the phase change. An evaluation device for tempered glass, characterized in that it synthesizes stress distributions other than the first region. A polarization phase difference variable process for varying the polarization phase difference of the laser light by more than one wavelength with respect to the wavelength of the laser light,
An imaging process of capturing scattered light emitted when the laser light with the variable polarization phase difference is incident on tempered glass a plurality of times at predetermined time intervals to acquire a plurality of images;
Using the plurality of images, the periodic luminance change of the scattered light is measured, a phase change of the luminance change is calculated, and a first stress distribution in the depth direction from the surface of the tempered glass is calculated based on the phase change. In addition, a method for evaluating tempered glass, comprising a calculation step of measuring a physical quantity related to the strength of the tempered glass using the plurality of images. According to clause 27,
A method for evaluating tempered glass, wherein in the calculation step, the luminance of the scattered light is measured as the physical quantity. According to clause 27,
The plurality of images have a speckle pattern,
A method for evaluating tempered glass, wherein in the calculation step, the dispersion value of the luminance of the speckle pattern is measured as the physical quantity. According to clause 27,
A method for evaluating tempered glass, characterized in that, in the calculation step, the refractive index of the tempered glass is measured as the physical quantity. According to any one of claims 27 to 30,
A first optical wavelength selecting member having a relatively high transmittance of the wavelength of the laser light and a second optical wavelength selecting member having a relatively low transmittance of the wavelength of the laser light are incident on the imaging element used in the imaging process. is switchably inserted into the optical path,
In the calculation process, the physical quantities include the first luminance of the scattered light when the first light wavelength selecting member is inserted on the optical path, and the above when the second light wavelength selecting member is inserted on the optical path. A method for evaluating tempered glass, comprising measuring a second luminance of scattered light and calculating a ratio of the first luminance and the second luminance. According to any one of claims 27 to 30,
When the laser light in the first wavelength band is incident, the first optical wavelength selecting member that transmits the laser light in the first wavelength band and the second optical wavelength selecting member that transmits the light in the second wavelength band are 1. On the optical path through which the laser light is incident on the imaging device used in the imaging process, such that when the optical wavelength selection member is selected and the laser light in the second wavelength band is incident, the second optical wavelength selection member is selected. is convertibly inserted into,
In the calculation process, the physical quantities include the first luminance of the scattered light when the laser light in the first wavelength band is incident and the first optical wavelength selection member is inserted into the optical path, and the second wavelength band. An evaluation method of tempered glass, characterized by measuring the second luminance of the scattered light when laser light is incident and the second light wavelength selection member is inserted into the optical path. According to any one of claims 27 to 30,
An evaluation method for tempered glass, wherein, in the calculation step, the physical quantity is measured in a plurality of regions in the depth direction from the surface of the tempered glass. According to any one of claims 27 to 30,
In the polarization retardation variable process, a method for evaluating tempered glass, characterized in that the polarization retardation is varied using a liquid crystal element. According to any one of claims 27 to 30,
A process of calculating each refractive index distribution based on the positions of the bright lines of P-polarized light and S-polarized light, and calculating a second stress distribution based on the difference in refractive index distribution of the P-polarized light and the S-polarized light and the photoelastic constant of the tempered glass. A method for evaluating tempered glass, characterized in that: For at least one sheet of tempered glass among a plurality of tempered glasses made in the same manufacturing process, the first stress distribution and the second stress distribution obtained by the tempered glass evaluation method described in item 35 are synthesized to obtain a stress distribution. , An evaluation method of tempered glass, characterized in that, with respect to the remaining tempered glass, a stress distribution is obtained by measuring only one of the first stress distribution and the second stress distribution. A process for varying the polarization phase difference of the laser light by more than one wavelength with respect to the wavelength of the laser light, and imaging the scattered light emitted when the laser light with the changed polarization phase difference is incident on the tempered glass multiple times at predetermined time intervals. , an imaging process for acquiring a plurality of images, measuring a periodic luminance change of the scattered light using the plurality of images, calculating a phase change of the luminance change, and measuring the surface of the tempered glass based on the phase change. A characteristic value from the stress value obtained by the evaluation method of tempered glass having a calculation process for calculating a first stress distribution in the depth direction and measuring a physical quantity related to the strength of the tempered glass using the plurality of images. A method of manufacturing tempered glass, characterized in that the shipment judgment is made after obtaining and confirming whether the characteristic values are within the control values. According to clause 37,
In the polarization phase difference variable process, a method of manufacturing tempered glass, characterized in that the polarization phase difference is varied by a liquid crystal element. According to clause 37 or 38,
A process of calculating each refractive index distribution based on the positions of the bright lines of P-polarized light and S-polarized light, and calculating a second stress distribution based on the difference in refractive index distribution of the P-polarized light and the S-polarized light and the photoelastic constant of the tempered glass. A method of manufacturing tempered glass, characterized in that: According to clause 39,
Among the plurality of tempered glasses made in the same manufacturing process, for at least one sheet of tempered glass, a stress distribution is obtained by combining the first stress distribution and the second stress distribution obtained by the evaluation method, and for the remaining tempered glass, A method of manufacturing tempered glass, characterized in that the stress distribution is obtained by measuring only one of the first stress distribution and the second stress distribution. According to clause 37 or 38,
A strengthening process of manufacturing tempered glass strengthened with lithium-containing glass and determining the shipment of the tempered glass is included at least twice,
A method for manufacturing tempered glass, wherein each of the strengthening steps makes the shipment judgment based on the first stress distribution obtained by the evaluation method. According to clause 41,
In the final strengthening process, the evaluation method calculates each refractive index distribution based on the positions of the bright lines of P-polarized light and S-polarized light, and calculates the refractive index distribution difference between the P-polarized light and the S-polarized light and the photoelastic constant of the tempered glass. A method for manufacturing tempered glass, comprising a step of calculating a second stress distribution based on the second stress distribution, and making a shipment judgment based on the second stress distribution obtained by the evaluation method. According to clause 42,
In the strengthening process excluding the final step, the shipping judgment is made based on the stress value (CT) at the deepest part of the glass derived from the first stress distribution and the glass depth (DOL_zero) at which the stress value becomes zero. A manufacturing method of tempered glass characterized by: According to clause 42,
A method of manufacturing tempered glass, characterized in that, in the final strengthening process, the second stress distribution is approximated to a function and the shipment judgment is made. According to clause 44,
A method for producing tempered glass, characterized in that the function approximation is performed using the following equation (2).

However, σf(x) is the second stress distribution, a is the slope, and CS2 is the stress value of the outermost surface. According to clause 44,
A method for producing tempered glass, characterized in that the function approximation is performed using the following equation (3).

However, σf(x) is the second stress distribution, a is the slope, CS2 is the stress value of the outermost surface, and erfc is the error function. According to clause 42,
In the strengthening process excluding the final, the first stress distribution is performed using the second stress distribution obtained in the strengthening process, the plate thickness t of the tempered glass, and the first stress distribution of the tempered glass under the same conditions measured in advance. and the second stress distribution are synthesized, the stress value (CT) at the deepest part of the glass is found from the synthesized stress distribution, a characteristic value is derived, and the shipment judgment is made based on whether the characteristic value is within the allowable range. A method of manufacturing tempered glass, characterized in that: According to clause 42,
In the strengthening process excluding the final, the first stress distribution is performed using the second stress distribution obtained in the strengthening process, the plate thickness t of the tempered glass, and the first stress distribution of the tempered glass under the same conditions measured in advance. and the second stress distribution are synthesized, the stress value (CT) at the deepest part of the glass where the integral value of the stress distribution after synthesis is zero is found, a characteristic value is derived, and whether the characteristic value is within the allowable range. A method for producing tempered glass, characterized in that the shipment judgment is performed by. According to clause 42,
In the strengthening process excluding the final, the first stress distribution is performed using the second stress distribution obtained in the strengthening process, the plate thickness t of the tempered glass, and the first stress distribution of the tempered glass under the same conditions measured in advance. and the second stress distribution are synthesized, the stress distribution after synthesis is approximated by the equation (5) below, and the integral value of σ(x) (x = 0 to t/2) is zero in the deepest part of the glass. A method of manufacturing tempered glass, characterized in that the stress value (CT) of is found, the characteristic value is derived, and the shipment judgment is made based on whether the characteristic value is within an allowable range.

However, σ(x) is the stress distribution after synthesis, σf(x) is the second stress distribution, t is the tempered glass plate thickness, and CS ₀ and c are parameters derived based on the first stress distribution. According to clause 49,
A method of manufacturing tempered glass, characterized in that the CS ₀ and c are derived based on a first stress distribution of tempered glass under the same conditions measured in advance. According to clause 49,
The CS ₀ and c are derived based on CS0' and c' derived from the first stress distribution obtained in the strengthening process before the final round and the following equations (6) and (7). Method of manufacturing tempered glass.


However, A1 and A2 are proportionality constants. According to clause 51,
A1 and A2 are a method of manufacturing tempered glass, characterized in that they are derived based on the first stress distribution of tempered glass under the same conditions measured in advance. Tempered glass manufactured by the method for producing tempered glass according to claim 37 or 38. According to clause 53,
Tempered glass, characterized in that glass containing 2 wt% or more of lithium has been chemically strengthened. According to clause 53,
Tempered glass manufactured by being wind-cooled and then chemically strengthened.

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