JP6995324B2 - Tempered glass evaluation device, tempered glass evaluation method, tempered glass manufacturing method, tempered glass - Google Patents

Description

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

In electronic devices such as mobile phones and smartphones, glass is often used for the display unit and the main body of the housing. With the recent thinning and weight reduction of electronic devices, thinning of glass used for electronic devices is also required. The strength of glass decreases as the plate thickness decreases. Therefore, in order to increase the strength of glass, so-called chemically strengthened glass, whose strength is increased by forming a surface layer (ion exchange layer) by ion exchange on the glass surface, is used, and surface stress is applied by an optical method. It was common to measure the value, make sure it was properly fortified, and 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 optical waveguide effect and the photoelastic effect are used to obtain the surface layer. A technique for measuring compressive stress in a non-destructive manner (hereinafter referred to as a non-destructive measurement technique) can be mentioned. In this non-destructive measurement technology, monochromatic light is incident on the surface layer of tempered glass to generate multiple modes by the optical waveguide effect, the light whose ray trajectory is fixed in each mode is extracted, and the emission line corresponding to each mode is taken out by a convex lens. To form an image. There are as many bright lines as the number of modes formed.

Further, in this non-destructive measurement technique, the light extracted from the surface layer can observe the emission lines of two types of light components whose vibration directions are horizontal and vertical with respect to the emission surface. Then, the light of mode 1 having the lowest order uses the property of passing through the side closest to the outermost surface of the surface layer, and from the position of the emission line corresponding to mode 1 of the two types of light components, about each light component. The refractive index is calculated, and the stress near the surface of the tempered glass is obtained from the difference between the two types of refractive index and the photoelastic constant of the glass (see, for example, Patent Document 1).

On the other hand, based on the principle of the above non-destructive measurement technique, the stress on the outermost surface of the glass (hereinafter referred to as the surface stress value) is obtained by extrapolation from the position of the emission line corresponding to the mode 1 and the mode 2. Assuming that the refractive index distribution of the surface layer changes linearly, a method of obtaining the depth of the compressive stress layer from the total number of emission lines has been proposed (see, for example, Patent Document 3 and Non-Patent Document 1).

Further, a method of defining the tensile stress CT inside the glass based on the surface stress value measured by the above-mentioned measurement technique using surface waveguide light and the depth of the compressive stress layer, and managing the strength of the tempered glass by the CT value. Has been proposed (see, for example, Patent Document 2). In this method, the tensile stress CT is calculated by "CT = (CS x DOL) / (t x 1000-2 x DOL)" (Equation 0). Here, CS is the surface stress value (MPa), DOL is the depth of the compressive stress layer (unit: μm), and t is the plate thickness (unit: mm).

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

In addition, the stress distribution on the glass surface layer side is measured from the glass depth (DOL_TP) at the position where the stress distribution bends, and based on the measurement result (measurement image) of the stress distribution on the glass surface layer side, the glass deep layer side than DOL_TP. A method for predicting the stress distribution of the glass has also been proposed (see, for example, Patent Document 4). However, this method does not actually measure the stress distribution on the deeper side of the glass than DOL_TP, so that there is a problem that the measurement reproducibility is poor.

However, chemically strengthened glass is also diversified in order to improve its strength and performance, and it is not possible to make a sufficient evaluation by the conventional stress measuring method.

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

For chemically strengthened glass of lithium-containing glass, the conventional optical surface stress measuring device can evaluate the stress layer near the surface where lithium is exchanged for potassium, but evaluates the internal stress layer where lithium is exchanged for sodium. Since it cannot be done, the stress depth cannot be measured.

Since the crystallized glass must be transparent to be used especially for the display part, the crystallized glass used here is a crystallized glass whose crystal grains are sufficiently smaller than the wavelength of visible light, and is in the visible range. , Transparent. Therefore, it is possible to measure the stress of the surface formed in the chemical strengthening step with a conventional optical surface stress measuring device.

However, the strength of the crystallized glass largely depends not only on the stress near the chemically strengthened surface but also on the crystal grain size, crystal grain density, crystal grain species, etc. generated by recrystallization, and recrystallization. It also has a large effect on the subsequent chemical strengthening process. Furthermore, the crystals produced in this recrystallization step may also change in the chemical strengthening step.

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

Japanese Unexamined Patent Publication No. 53-136886 Japanese Patent Publication No. 2011-530470 Japanese Unexamined Patent Publication No. 2016-142600 U.S. Patent Publication 2016/0356760

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

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

This glass is immersed in a hot mixed molten salt of sodium nitrate and potassium nitrate to be chemically strengthened. Both sodium and potassium ions exchange ions with lithium ions in the glass due to their high concentration in the molten salt, but since sodium ions are more likely to diffuse into the glass, they first exchange with the lithium ions in the glass. Sodium ions in the molten salt are exchanged.

Here, the refractive index of the glass is lower when sodium ions are ion-exchanged with lithium ions, and higher when potassium ions are ion-exchanged with lithium ions or sodium ions. That is, the potassium ion concentration is higher in the ion-exchanged region near the glass surface than in the non-ion-exchanged portion of the glass, and the sodium ion concentration is higher in the deeper ion-exchanged region. Therefore, the refractive index near the outermost surface of the ion-exchanged glass decreases with the depth, but has the characteristic that the refractive index increases with the depth from a certain depth to the region where the ion exchange is not performed.

Therefore, the stress measuring device using the waveguide light on the surface described in the background technology cannot measure the stress distribution in the deep part only by the stress value on the outermost surface or the stress distribution, and the depth of the stress layer and the CT value. , The overall stress distribution could not be known. As a result, it was not possible to develop to find appropriate chemical strengthening conditions, and it was not possible to control the quality of manufacturing.

Further, when the aluminosilicate glass or soda glass is chemically strengthened after being air-cooled, the chemically strengthened portion can measure the stress distribution or the stress value by the stress measuring device using the waveguide light on the surface described in the background art. However, the portion that has not been chemically strengthened and has only been wind-cooled has a small change in the refractive index and cannot be measured by the stress measuring device using the waveguide light on the surface described in the background technique. As a result, it was not possible to know the depth of the stress layer, the CT value, and the overall stress distribution. As a result, it was not possible to develop to find appropriate chemical strengthening conditions, and it was not possible to control the quality of manufacturing.

On the other hand, crystallized glass has higher strength than general glass. Therefore, chemically strengthened crystallized glass can obtain higher strength than ordinary tempered glass. However, in the crystallized glass, physical performance such as strength is greatly affected by the crystal state (particle size, crystal grain density, crystal species) and the like. Therefore, in crystallized glass, it is necessary to measure the stress distribution due to chemical strengthening as well as the physical quantity related to the strength of the crystallized glass.

The present invention has been made in view of the above points, and provides an evaluation device for tempered glass capable of measuring the stress distribution of tempered glass and measuring the physical quantity related to the strength of the tempered glass. The purpose.

In the evaluation device of this tempered glass, a polarization phase difference variable member that changes the polarization phase difference of the laser light by one or more wavelengths with respect to the wavelength of the laser light, and the laser light having the variable polarization phase difference are used as the strengthened glass. The scattered light emitted by being incident is imaged a plurality of times at predetermined time intervals, and the image pickup element for acquiring a plurality of images and the plurality of images are used to measure the periodic brightness change of the scattered light. The phase change of the brightness change is calculated, the stress distribution in the depth direction from the surface of the tempered glass is calculated based on the phase change, and the physical quantity related to the strength of the tempered glass is measured using the plurality of images. It is a requirement to have a calculation unit to be used.

According to the disclosed technique, it is possible to provide a tempered glass evaluation device capable of measuring the stress distribution of tempered glass and measuring the physical quantity related to the strength of the tempered glass.

It is a figure which illustrates the evaluation apparatus which concerns on 1st Embodiment. It is a figure which looked at the evaluation apparatus which concerns on 1st Embodiment from the H direction of FIG. It is a figure which illustrates the relationship between the applied voltage of a liquid crystal element, and the polarization phase difference. It is a figure which illustrates the circuit which generates the drive voltage which changes the polarization phase difference linearly with time in the liquid crystal element. It is a figure which illustrates the scattered light image at a certain moment of the laser beam L imaged on the image sensor. It is a figure which illustrates the time change of the scattered light brightness at the point B and the point C of FIG. It is a figure which illustrates the phase of the scattered light change according to the glass depth. It is a figure which illustrates the stress distribution obtained by the equation 1 based on the phase data of the scattered light change of FIG. 7. It is a figure which illustrates the actual scattered light image at different time t1 and t2. It is a figure which shows the unfavorable design example of the incident surface of the laser beam L in the tempered glass. It is a figure which shows the preferable design example of the incident surface of the laser beam L in the tempered glass. It is a figure which illustrates the functional block of the arithmetic unit 70 of the evaluation apparatus 1. It is a flowchart (the 1) which illustrates the evaluation method using the evaluation apparatus 1. It is a flowchart (the 2) which illustrates the evaluation method using the evaluation apparatus 1. It is an image of the scattered light at a certain time obtained by the image sensor 60. It is a graph of the time change of the average scattered light luminance in the region E of FIG. 15A. It is a figure which illustrates the relationship between the scattered light luminance amplitude value As and the depth of a glass. It is a figure which illustrates the evaluation apparatus which concerns on the modification 1 of the 1st Embodiment. It is a figure which illustrates the evaluation apparatus which concerns on the modification 2 of the 1st Embodiment. It is a figure which illustrates the evaluation apparatus which concerns on the modification 3 of the 1st Embodiment. It is a figure which illustrates the evaluation apparatus which concerns on the modification 4 of the 1st Embodiment. It is explanatory drawing of the polarization phase difference variable member using a photoelastic effect. It is a figure which illustrates the evaluation apparatus which concerns on 2nd Embodiment. It is a figure which showed the stress distribution measured by the evaluation apparatus 1 and 2 in the same graph. It is a flowchart which illustrates the evaluation method using the evaluation apparatus 2. It is a figure which illustrates the functional block of the arithmetic unit 75 of the evaluation apparatus 2. It is a figure which illustrates the stress distribution in the depth direction of tempered glass. It is a flowchart (the 1) which derives a characteristic value based on a stress distribution. It is a figure which shows the example which derived each characteristic value from the measured stress distribution. It is a flowchart (2) which derives a characteristic value based on a stress distribution. It is a figure (the 1) which shows the other example which derived each characteristic value from the measured stress distribution. It is a flowchart (3) which derives a characteristic value based on a stress distribution. It is a figure (No. 2) which shows another example which derived each characteristic value from the measured stress distribution. It is a figure which shows an example of the flowchart of the quality judgment using each characteristic value obtained by the measurement of a stress distribution. It is a figure which shows the other example of the flowchart of the quality judgment using each characteristic value obtained by the measurement of a stress distribution. This is an example (No. 1) of the flow chart of quality judgment when the lithium-containing glass is toughened twice or more. This is an example (No. 2) of the flow chart of quality judgment when the lithium-containing glass is toughened twice or more. This is an example of the combined 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. It is a stress distribution obtained in Comparative Example 1 and Examples 1 to 3. It is a figure which illustrates the evaluation apparatus which concerns on 3rd Embodiment. It is a figure which illustrates the scattered light image of the laser beam L traveling through the interface between a light supply member and tempered glass. It is a figure which illustrated the structural part for sandwiching a liquid between a light supply member and tempered glass. It is a figure which showed the 2nd example of the structural part for sandwiching a liquid between a light supply member and tempered glass. It is a figure which showed the 3rd example of the structural part for sandwiching a liquid between a light supply member and tempered glass. It is a figure which showed the 4th example of the structural part for sandwiching a liquid between a light supply member and tempered glass. It is a figure which showed the 5th example of the structural part for sandwiching a liquid between a light supply member and tempered glass. It is a figure which showed the sixth example of the structural part for sandwiching a liquid between a light supply member and tempered glass. It is a figure which showed the 7th example of the structural part for sandwiching a liquid between a light supply member and tempered glass. It is a figure explaining that the laser beam L is incident in the tempered glass. It is a figure explaining the image of the laser locus taken from the position of the image sensor of FIG. 49. It is a figure explaining the definition of the angle and the length of the laser beam in the light supply member or the tempered glass of FIG. 49. It is a top view, a front view, and a side view of FIG. 51. It is a conceptual diagram of the laser beam traveling through a light supply member and tempered glass. It is a conceptual diagram of a laser beam traveling through tempered glass. This is an example of a flowchart for obtaining the incident margin angle Ψ. This is an example of a flowchart for obtaining the refractive index ng of tempered glass. This is another example of the flowchart for obtaining the incident margin angle Ψ. This is an example of a flowchart for obtaining θL in which the surface through which the laser beam passes and the observation surface do not change. It is a figure which illustrates the stress distribution in the depth direction of tempered glass. It is a figure which illustrates the evaluation apparatus which installed the glass thickness measuring apparatus.

Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same components may be designated by the same reference numerals and duplicate explanations may be omitted.

<First Embodiment>
FIG. 1 is a diagram illustrating an evaluation device according to the 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, a light conversion member 50, an image pickup element 60, and a calculation unit 70. And the light wavelength selection member 80.

Reference numeral 200 is tempered glass to be the object to be measured. The tempered glass 200 is, for example, glass that has been tempered by a chemical tempering method, an air cooling tempering method, or the like. The tempered glass referred to in the present application also includes crystallized glass that has been tempered. Here, the crystallized glass is a glass produced through a crystallization step, in other words, a glass having crystals intentionally precipitated. In the present application, the strengthened crystallized glass may be referred to as a strengthened crystallized glass, if necessary.

The laser light source 10 is arranged so that the laser light L is incident on the surface layer of the tempered glass 200 from the light supply member 40, and a polarization phase difference variable member 30 is provided between the laser light source 10 and the light supply member 40. It has been inserted.

As the laser light source 10, for example, a semiconductor laser, a helium neon laser, or an argon laser can be used. Semiconductor lasers are usually polarized, and semiconductor lasers having 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 beam, the smaller the beam diameter and the higher the spatial resolution. Further, the shorter the wavelength of the laser beam, the smaller the noise tends to be, which is preferable. The laser beam needs to pass through 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 beam is in the ion exchange layer of the tempered glass 200 and the minimum beam diameter is 20 μm or less. It is more preferable that the position of the minimum beam diameter of the laser beam is the surface 210 of the tempered glass 200. Since the beam diameter of the laser beam has 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 a width of 1 / e ² (about 13.5%) when the brightness at the center of the beam is maximized, and when the beam shape is an elliptical shape or a sheet shape, the beam diameter is the minimum width. Means. However, in this case, the minimum width of the beam diameter needs to face the glass depth direction.

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

The beam shaping member and the output distribution shaping member are inserted, for example, between the laser light source 10 and the polarization phase difference variable member 30. Examples of the beam shaping member include a cylindrical lens, an anamorphic prism, a diaphragm, and the like. Examples of the output distribution shaping member include an aspherical lens, a DOE (Diffractive Optical Element), 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 beam L emitted by the laser light source 10 is not polarized, the polarizing member 20 is inserted between the laser light source 10 and the polarization phase difference variable member 30. When the laser beam L emitted by the laser light source 10 is polarized, the polarizing member 20 may or may not be inserted. Further, the laser light source 10 and the polarizing member 20 are installed so that the polarization plane of the laser beam 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 or the like can be used, but other members having the same function may be used.

The light supply member 40 is placed in a state of being 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 incident light from the laser light source 10 onto 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 beam is optically incident on the surface 210 of the tempered glass 200 through the prism, the refractive index of the prism needs to be substantially the same as the refractive index of the tempered glass 200 (within ± 0.2). be.

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

The laser beam L passing through the tempered glass 200 generates a small amount of scattered light _LS . The brightness of the scattered light _LS changes depending on the polarization phase difference of the scattered portion of the laser light L. Further, the laser light source 10 is installed so that the polarization direction of the laser beam L is 45 ° (within ± 5 °) of θ _s2 in FIG. 2 with respect to the surface 210 of the tempered glass 200. 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 beam L travels through the tempered glass, the polarization phase difference also changes, and the brightness of the scattered light _LS changes accordingly. Also changes. The polarization phase difference is a phase difference (retardation) caused by birefringence.

Further, the laser beam L is set so that θ _s1 is 10 ° or more and 30 ° or less with respect to the surface 210 of the tempered glass. This is because when the temperature is lower than 10 °, the laser beam propagates on the glass surface due to the optical waveguide effect, and the information inside the glass cannot be obtained. On the contrary, if it exceeds 30 °, the depth resolution inside the glass with respect to the laser optical path length decreases, which is not preferable as a measurement method. Therefore, it is preferably set to θ _s1 = 15 ° ± 5 °.

Next, the image pickup device 60 will be described with reference to FIG. FIG. 2 is a view of the evaluation device according to the first embodiment as viewed from the H direction of FIG. 1, and is a diagram showing the positional relationship of the image pickup device 60. Since the polarization of the laser beam L is incident on the surface 210 of the tempered glass 200 at an angle of 45 °, the scattered light _LS 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 _LS radiated at 45 ° with respect to the surface of the tempered glass, the image sensor 60 is installed in the direction of 45 ° with respect to the surface 210 of the tempered glass 200 in FIG. ing. That is, in FIG. 2, θ _s2 = 45 °.

Further, a light conversion member 50 is inserted between the image pickup element 60 and the laser beam L so as to form an image of the scattered light _LS by the laser beam L on the image pickup element 60. As the light conversion member 50, for example, a convex lens made of glass or a lens in which a plurality of convex lenses or concave lenses are combined can be used. At this time, when the numerical aperture (NA) of the lens is large, the noise is small, which is preferable.

Further, for a lens in which a plurality of lenses are combined, a telecentric lens in which the main light beam is parallel to the optical axis is used, so that the scattered light scattered in all directions from the laser beam L is mainly applied to the glass surface of the tempered glass 200. An image can be formed only with light scattered in the 45 ° direction (image pickup element direction). As a result, unnecessary light such as diffused reflection on the glass surface can be reduced.

Further, an optical wavelength selection member 80 for removing light unnecessary for stress measurement is inserted between the laser beam L and the image pickup element 60. The light wavelength selection member 80 does not transmit light having a wavelength other than the wavelength of the laser beam L by 50% or more, preferably 90% or more. Further, the width of the wavelength transmitted through the light wavelength selection member 80 is preferably about 10 nm or less. By inserting the light wavelength selection member 80, Raman scattered light, fluorescent light and extraneous light generated from the laser light L, which are unnecessary for stress measurement, are removed, and only the scattered light _LS necessary for stress measurement is captured by the image pickup element 60. Can be collected in. As the optical wavelength selection member 80, for example, a bandpass filter having a multilayer of dielectric films or a shortpass filter can be used.

As the image pickup device 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 is a control circuit that controls the element and extracts an electric signal of an image from the element, and digital image data generation that converts the electric signal into digital image data. It is connected to a circuit and a digital recording device that records multiple pieces of digital image data. Further, the digital image data generation circuit and the digital recording device are connected to the arithmetic unit 70.

The calculation unit 70 has a function of taking image data from the image pickup element 60, a digital image data generation circuit connected to the image pickup element 60, or a digital recording device, and performing image processing and numerical calculation. The calculation unit 70 may be configured to have other functions (for example, a function of controlling the light amount and the exposure time of the laser light source 10). The arithmetic unit 70 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a main memory, and the like.

In this case, various functions of the arithmetic unit 70 can be realized by reading the program recorded in the ROM or the like into the main memory and executing the program by the CPU. The CPU of the arithmetic unit 70 can read and store data from the RAM as needed. However, a part or all of the arithmetic unit 70 may be realized only by hardware. Further, the arithmetic unit 70 may physically have a plurality of devices and the like. As the arithmetic unit 70, for example, a personal computer can be used. Further, the arithmetic unit 70 may be provided with 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 with time. The polarization phase difference to be changed is one or more times the wavelength λ of the laser beam. The polarization phase difference must be uniform with respect to the wavefront of the laser beam L. For example, in a quartz wedge, the wavefront of the laser beam is not uniform because the polarization phase difference is not uniform in the direction in which the inclined surface of the wedge is attached. Therefore, it is not preferable to use a quartz wedge as the polarization phase difference variable member 30.

As the polarization phase difference variable member 30 capable of uniformly varying the polarization phase difference on the wavefront of the laser beam by 1λ or more electrically, for example, a liquid crystal element can be mentioned. In the liquid crystal element, the polarization phase difference can be changed by the voltage applied to the element. For example, when the wavelength of the laser beam is 630 nm, the wavelength of 3 to 6 can be changed. In the liquid crystal element, the maximum value of the polarization phase difference that can be changed by the applied voltage is determined by the size of the cell gap.

Since a normal liquid crystal element has a cell gap of several μm, the maximum polarization phase difference is about 1 / 2λ (several 100 nm). Further, in a display using a liquid crystal display or the like, no further change is required. On the other hand, in the liquid crystal element used in the present embodiment, when the wavelength of the laser beam is, for example, 630 nm, it is necessary to change the polarization phase difference of about 2000 nm, which is about three times that of 630 nm, and the polarization phase difference is 20 to 50 μm. A cell gap is required.

The voltage applied to the liquid crystal element and the polarization phase difference are not proportional. As an example, FIG. 3 shows the relationship between the applied voltage of a liquid crystal element having a cell gap of 30 μm and the polarization phase difference. In FIG. 3, the vertical axis represents the polarization phase difference (the number of wavelengths with respect to the wavelength of 630 nm), and the horizontal axis represents the voltage applied to the liquid crystal element (drawn in logarithm).

The voltage applied to the liquid crystal element is 0V to 10V, and the polarization phase difference of about 8λ (5000 nm) can be varied. However, in a liquid crystal element, the orientation of the liquid crystal is generally not stable at a low voltage of 0 V to 1 V, and the polarization phase difference fluctuates due to a temperature change or the like. Further, when the voltage applied to the liquid crystal element is 5 V or more, the change in the polarization phase difference is small with respect to the change in the voltage. In the case of this liquid crystal element, the polarization phase difference of 4λ to 1λ, that is, about 3λ can be stably changed by using the liquid crystal element at an applied voltage of 1.5V to 5V.

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 image pickup element 60. At this time, it is necessary to change the polarization phase difference linearly in time and synchronize with the timing of imaging by the image pickup device 60.

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

FIG. 4 is a diagram illustrating a circuit that generates a drive voltage in a liquid crystal element such that the polarization phase difference changes linearly with time.

In FIG. 4, the digital data storage circuit 301 corresponds to the polarization phase difference for changing the polarization phase difference at regular intervals based on the data obtained by measuring the applied voltage of the liquid crystal element to be used and the polarization phase difference in advance. The voltage values to be applied are recorded in the order of addresses as digital data within the range of the required change in polarization phase difference. Table 1 illustrates a part of the digital data recorded in the digital data storage circuit 301. The voltage column in Table 1 is the recorded digital data, and is the voltage value for each change of the polarization phase difference of 10 nm.

クロック信号発生回路３０２は、水晶振動子等を使い、周波数が一定であるクロック信号を発生させる。クロック信号発生回路３０２の発生したクロック信号は、デジタルデータ記憶回路３０１とＤＡコンバータ３０３に入力される。

The clock signal generation circuit 302 uses a crystal oscillator or the like to generate a clock signal having 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. According to the clock signal generated by the clock signal generation circuit 302, the digital data of the voltage values sequentially stored from the digital data storage circuit 301 is read out and sent to the DA converter 303.

The DA converter 303 converts the digital data of the voltage value read out at regular time intervals into an 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.

Although not shown in FIG. 4, the drive circuit of this liquid crystal element is synchronized with the circuit for controlling the image pickup element 60 of FIG. 2, and when the application of the drive voltage to the liquid crystal element is started, the image pickup element 60 is started. Start continuous imaging in time.

FIG. 5 is a diagram illustrating an image of scattered light at a certain moment of the laser beam L imaged on the image sensor. In FIG. 5, the depth of the tempered glass 200 from the surface 210 becomes deeper toward the top. In FIG. 5, the point A is the surface 210 of the tempered glass 200, and since the scattered light of the surface 210 of the tempered glass 200 is strong, the scattered light image spreads in an elliptical shape.

Since a strong compressive stress is applied to the surface portion of the tempered glass 200, the polarization phase difference of the laser beam L changes with the depth due to birefringence due to the photoelastic effect. Therefore, the scattered light brightness of the laser beam L also changes with the depth. The principle that the scattered light brightness of the laser light changes due to the internal stress of the tempered glass is described in, for example, Yogyo-Kyokai-Shi (Ceramics Association Journal) 80 {4} 1972.

The polarization phase difference variable member 30 can continuously change the polarization phase difference of the laser beam L before it is incident on the tempered glass 200 in time. As a result, at each point of the scattered light image of FIG. 5, the scattered light brightness changes according to the polarization phase difference changed by the polarization phase difference variable member 30.

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

Locally considered, the phase F of the periodic change in scattered light brightness 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 beam L is set to the laser. With respect to the function F (s) represented by the position s along the light L, the differential value dF / ds with respect to s is the amount of birefringence generated by the in-phase 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 the point S can be calculated by the following equation 1 (Equation 1).

In the present specification, since the laser beam L is obliquely incident on the glass, it is necessary to convert from the point s to the depth direction when obtaining the stress distribution with respect to the depth in the vertical direction from the glass surface. It is shown in Equation 8 (Equation 8) described later.

一方、偏光位相差可変部材３０は、ある時間内に時間的に連続に偏光位相差を１波長以上変化させる。その時間内に、撮像素子６０により、複数枚の時間的に連続したレーザ光Ｌによる散乱光像を記録する。そして、この連続撮影をした散乱光像の各点における時間的な輝度の変化を測定する。

On the other hand, the polarization phase difference variable member 30 continuously changes the polarization phase difference by one wavelength or more in a certain time. Within that time, the image sensor 60 records a plurality of temporally continuous scattered light images by the laser light L. Then, the change in brightness with time at each point of the scattered light image obtained by this continuous shooting is measured.

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

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

In the data of the periodic change of the scattered light at a certain point, the phase F at that point can be accurately obtained by the least squares method of the trigonometric function or the Fourier integral based on the period T determined above.

In the previously known method of least squares of trigonometric functions in period T and Fourier integral, only the phase component in known period T is extracted, and noise in other periods can be removed. Moreover, the removal ability becomes higher as the time change of the data becomes longer. Usually, the scattered light brightness is weak and the amount of phase that actually changes is small, so it is necessary to measure with data by changing the polarization phase difference of several λ.

When the data of the temporal change of the scattered light at each point of the scattered light image along the laser beam L on the image taken by the image pickup element 60 is measured and the phase F is obtained for each by the same method as described above. The phase F of the scattered light brightness along the laser light L can be obtained. FIG. 7 is an example of the phase of the scattered light change according to the glass depth.

In the phase F of the scattered light brightness along the laser beam L, the differential value at the coordinates on the laser beam L can be calculated, and the stress value at the coordinates s on the laser beam L can be obtained by Equation 1. Further, if the coordinates s are converted into the distance from the glass surface, the stress value with respect to the depth from the surface of the tempered glass can be calculated. FIG. 8 is an example in which the stress distribution is obtained from Equation 1 based on the phase data of the scattered light change in FIG. 7.

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

In FIG. 9, it can be seen that the scattered light image of the laser light has different luminance at each point, and even at the same point, the luminance distribution at time t2 is not the same as the luminance distribution at time t1. I understand. This is because the phase of the periodic change in scattered light luminance is out of phase.

In the evaluation device 1, the incident surface of the laser beam L is preferably tilted by 45 ° with respect to the surface 210 of the tempered glass 200. This will be described with reference to FIGS. 10 and 11.

FIG. 10 is a diagram showing an unfavorable design example of the incident surface of the laser beam L in the tempered glass. In FIG. 10, the incident surface 250 of the laser beam L in the tempered glass 200 is perpendicular to the surface 210 of the tempered glass.

10 (b) is a view seen from the direction H of FIG. 10 (a). As shown in FIG. 10B, the image pickup device 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 the two different points, points A, and B on the laser beam L to the image pickup device 60 are the distance A and the distance B, the distances are different. That is, the points A and B cannot be focused at the same time, and the scattered light image of the laser beam L in the required region cannot be obtained as a good image.

FIG. 11 is a diagram showing a preferable design example of the incident surface of the laser beam L in the tempered glass. In FIG. 11, the incident surface 250 of the laser beam L in the tempered glass 200 is tilted by 45 ° with respect to the surface 210 of the tempered glass 200.

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

In particular, when a laser beam having a minimum beam diameter of 20 μm or less is used, the depth of focus is shallow, and the depth of focus is about several tens of μm at most. Therefore, it is possible to incline the incident surface 250 of the laser beam L in the tempered glass 200 by 45 ° with respect to the surface 210 of the tempered glass 200 so that the distance to the image pickup element 60 is the same at any point on the tempered glass L. It is extremely important to obtain a good image.

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

The evaluation device 1 can measure the stress distribution of the tempered glass by the luminance change measuring means 701, the phase change calculating means 702, and the stress distribution calculating means 703 of the calculation unit 70. The physical quantity measuring means 704 is a part having a function of measuring a physical quantity related to the strength of the tempered glass, and the physical quantity measuring means 704 may not be used when only measuring the stress distribution of the tempered glass.

(Measurement flow 1: Measurement of stress distribution of tempered glass)
FIG. 13 is a flowchart (No. 1) illustrating an evaluation method using the evaluation device 1, and is a flowchart illustrating a method for measuring the stress distribution of the tempered glass in the evaluation device 1. The flow of measuring the stress distribution of the tempered glass in the evaluation device 1 will be described with reference to FIGS. 12 and 13.

The measurement shown in FIG. 13 can be performed, for example, after the step of applying a tempering treatment to the base plate to produce tempered glass. Further, the measurement shown in FIG. 13 may be performed after the step of subjecting the base plate to a crystallization treatment to prepare a crystallized glass and further subjecting the prepared crystallized glass to a strengthening treatment to prepare a strengthened crystallized glass. good.

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 continuously converted into the laser light wavelength by the polarization phase difference variable member 30. On the other hand, it is variable by one or more wavelengths (polarization phase difference variable step).

Next, in step S402, the laser beam having a variable polarization phase difference is obliquely incident on the surface 210 into the tempered glass 200 to be measured via the light supply member 40 (light supply step). ..

Next, in step S403, the image pickup element 60 captures the scattered light generated by the laser beam having a variable polarization phase difference traveling through the tempered glass 200 a plurality of times at predetermined time intervals, and acquires a plurality of images (imaging). Process).

Next, in step S404, the luminance change measuring means 701 of the arithmetic unit 70 was varied by the polarization phase difference variable step using a plurality of images obtained at time intervals of the scattered light obtained in the imaging step. The periodic luminance change of the scattered light accompanying the temporal change of the polarization phase difference is measured (luminance change measuring step).

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 beam 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 uses the tempered glass 200 based on the phase change of the periodic brightness change of the scattered light along the laser beam incident on the tempered glass 200. The stress distribution in the depth direction from the surface 210 of the surface 210 is calculated (stress distribution calculation step). The calculated stress distribution may be displayed on a display device (liquid crystal display or the like).

(Measurement flow 2: Measurement of stress distribution of tempered glass and measurement of physical quantity related to strength)
The evaluation device 1 measures the stress distribution of the tempered glass by the brightness change measuring means 701, the phase change calculating means 702, the stress distribution calculating means 703, and the physical quantity measuring means 704 of the calculation unit 70, and the physical quantity related to the strength of the tempered glass. Can be measured.

FIG. 14 is a flowchart (No. 2) illustrating an evaluation method using the evaluation device 1, illustrating a method for measuring the stress distribution of the tempered glass in the evaluation device 1 and a method for measuring the physical quantity related to the strength of the tempered glass. It is a flowchart. With reference to FIGS. 12 and 14, a flow for measuring the stress distribution of the tempered glass in the evaluation device 1 and measuring the physical quantity related to the strength of the tempered glass will be described.

The measurement shown in FIG. 14 is performed after, for example, a step of subjecting a base plate to a crystallization treatment to prepare a crystallized glass and further subjecting the prepared crystallized glass to a strengthening treatment to prepare a strengthened crystallized glass. be able to.

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

Here, the "physical quantity related to the strength of the tempered glass" is, for example, a physical quantity such as a refractive index, a crystallization rate, a crystal grain size, a crystal grain density, a haze, an amount of defects and impurities in the glass, and these physical quantities. It is assumed that the parameters necessary for obtaining the above (scattered light brightness amplitude value, average scattered light brightness, scattered light brightness dispersion value, etc.) are included. That is, the physical quantity measuring means 704 may measure only the scattered light brightness amplitude value or the average scattered light brightness without directly measuring the physical quantity such as the crystallization rate. Even in this case, the strength of the tempered glass can be estimated from the measurement result of the physical quantity measuring means 704.

The measurement of physical quantities related to the strength of tempered glass will be described in more detail below.

(Measurement example 1 of physical quantity related to the strength of tempered glass)
15 (a) is an image of scattered light at a certain time obtained by the image sensor 60, and FIG. 15 (b) is an enlarged view of the region E of FIG. 15 (a). Further, FIG. 16 is a graph of the temporal change of the average scattered light luminance in the region E of FIG. 15 (a). When the phase difference of the laser beam L incident by the polarization phase difference variable member 30 changes, the scattered light brightness also changes accordingly. Therefore, in the graph of the temporal change of the scattered light brightness shown in FIG. 16, the scattered light brightness changes periodically with the change of the phase difference of the laser light. The amplitude value of the change in the scattered light brightness is defined as the scattered light brightness amplitude value As, and the average value of the change in the scattered light brightness is defined as the average scattered light brightness Is.

Usually, the scattered light includes scattered light due to some scattering mechanism. Scattered light whose wavelength is the same as that of incident light has different scattering properties depending on the relationship between the size of the scattered particles and the wavelength. Assuming that the diameter of the scattered particles is D, the wavelength of the incident light is λ, and the wavelength λ of the incident light is constant, if the scattered particles are sufficiently small, they are scattered by the scattering mechanism by Rayleigh scattering, and D = λ × 1/10. Therefore, it begins to change to the scattering mechanism in Me-scattering, and when D ≧ λ, it becomes completely Me-scattering.

The magnitude of the haze of the crystallized glass is determined by the crystal grain size, the crystal grain density, and the difference in the refractive index between the crystal and the glass phase. The smaller the difference in refractive index between the crystal and the glass phase, the smaller the haze, but it is difficult to completely match the refractive index between the crystal and the glass phase, and there is a difference in refractive index of about 0.05 to 0.50. It is common. For example, when the difference in refraction between the crystal and the glass phase is about 0.1, the crystal grain size (diameter of the crystal grain) of the strengthened crystallized glass is transparent with visible light, so that the strengthened crystallized glass is transparent. The crystal grain size of the glass is sufficiently smaller than the visible light wavelength of about 600 nm and is controlled to 10 nm to 100 nm. Therefore, in many cases, the Rayleigh scattering mechanism is dominant, but when the crystal grain size is 100 nm, which is the maximum, the influence of the Mie scattering mechanism also appears. Further, the scattered light brightness is highly proportional to the diameter of the scattered particles and proportional to the scattered particle density in both Rayleigh scattering and Mie scattering. In Rayleigh scattering, it is proportional to the sixth power of the scattered particle size, in Mie scattering, it is proportional to the square, and it is considered to be in the meantime in the region where the Rayleigh scattering changes to the Mie scattering mechanism. That is, in Rayleigh scattering and Mie scattering whose wavelength is the same as that of incident light, the larger the scattered particle diameter and the higher the density, the higher the scattered light brightness.

Further, there are fluorescence scattering and Raman scattering as scattering in which the wavelength of the scattered light is different from the wavelength of the incident light. Usually, fluorescent scattering is generated by impurities and defects in the glass, and Raman scattering is generated by the composition and the bonding state.

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

In the evaluation device 1, an optical wavelength selection member 80 that transmits only the vicinity of the wavelength of the laser beam is provided between the light supply member 40 and the image pickup element 60. Since the width of the wavelength transmitted through the light wavelength selection member 80 is as narrow as about 10 nm or less, the image pickup element 60 captures only scattered light having a wavelength substantially the same as the wavelength of the laser light. For example, the scattered light does not contain fluorescent scattering and Raman scattering components having different wavelengths. 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 intensity amplitude value As is determined by the size of the scattered particles, that is, the crystal grains of the strengthened crystallized glass, and the crystal grain density. Since it is determined by the ratio of components, it is determined by the size of scattered particles, that is, crystal grains.

It is not possible to directly calculate the absolute values of the scattered particle diameter and the scattered particle density from the two measured values of the scattered light brightness amplitude value As and the average scattered light brightness Is. However, in the strengthened crystallized glass having different scattered particle size and scattered particle density, that is, crystal grain size and crystal grain density, the values of the scattered light intensity amplitude value As and the average scattered light intensity Is are different, and they are independent of each other. It is possible to see the difference. That is, even if the absolute values of the scattered particle diameter and the scattered particle density are not calculated directly, the variation of the scattered particle diameter and the scattered particle density can be known by measuring the scattered light brightness amplitude value As and the average scattered light brightness Is. be able to.

Further, by measuring the scattered particle size and the scattered particle density by another method, and experimentally obtaining the relationship between the scattered light intensity amplitude value As and the average scattered light intensity Is and the crystal grain size and the crystal grain density, the crystal can be crystallized. The particle size and crystal grain density can be estimated.

For example, the relationship between the scattered light brightness amplitude value As and the average scattered light brightness Is and the crystal grain size and the crystal grain density is experimentally obtained and stored in the memory in the calculation unit 70 as a table or a function. Then, the physical quantity measuring means 704 of the calculation unit 70 measures the scattered light brightness amplitude value As and the average scattered light brightness Is using the image obtained in the imaging step of step S403, and uses a table or a function to measure the scattered light brightness amplitude. The crystal grain size and the crystal grain density can be estimated from the measured values of the value As and the average scattered light brightness Is.

The measured values of the scattered light brightness amplitude value As and the average scattered light brightness Is reflecting the scattered particle diameter and the scattered particle density are the values in the region E of FIG. 15 (a). However, if the region to be measured is moved from the glass surface of the laser image to each depth in the depth direction and measured, the scattered particle diameter and the scattered particle density in the depth direction of the strengthened crystallized glass can be known. This makes it possible to confirm that the crystallization state is uniform in the depth direction from the surface.

(Measurement example 2 of physical quantity related to the strength of tempered glass)
As shown in FIG. 15B, the scattered light image is not uniform but is in the form of particles. This is 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 scattered particles and the optical system.

The degree of unevenness of the luminance of the speckle pattern, for example, the dispersion value of the luminance in the region E is calculated and used as Ss. The dispersion value Ss reflects the scattered particle density. When the size of the crystal grain is small, the Mie scattering component is small, and the intensity of the Mie scattering component cannot be measured, the crystal grain size and crystal are determined by the dispersion value Ss of the brightness of this speckle pattern and the scattered light brightness amplitude value As. The grain density can be estimated.

That is, it is possible to know the variation in the scattered particle diameter and the scattered particle density by measuring the dispersion value Ss and the scattered light intensity amplitude value As without directly calculating the absolute values of the scattered particle diameter and the scattered particle density. can. As in the case of the scattered light intensity amplitude value As and the average scattered light intensity Is, the scattered particle size and the scattered particle density are measured, and the dispersion value Ss and the scattered light intensity amplitude value As are combined with the crystal grain size and the crystal grain density. By experimentally obtaining the relationship between the above and storing it in the memory in the arithmetic unit 70 as a table or a function, the crystal grain size and the crystal grain density can be estimated.

(Measurement example 3 of physical quantity related to the strength of tempered glass)
In FIG. 15A, θ is an angle along the beam of the laser beam of the scattered light image. As will be described later, this angle θ is determined by the refractive index of the glass to be measured.

Ideally, the refractive index of the light supply member 40 is exactly the same as that 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. .. 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. In addition, the refractive index of tempered glass also varies. When the refractive index of the light supply member 40 and the tempered glass 200 are different, the incident angle θ _s1 of the laser beam L into the tempered glass 200 is different from the refraction angle θ _s1 ′ incident in the tempered glass. The angle is determined by the position and angle of the laser light source 10, the angle of each surface of the light supply member 40, the refractive index, the position and angle of the image pickup element, and the refractive index of the tempered glass. If known, the refractive index of the tempered glass can be calculated by measuring the angle θ along the beam of the laser beam L of the scattered light image.

On the other hand, in the tempered crystallized glass, the refractive index of the original glass and the refractive index of the crystal to be precipitated are different in many cases. For example, in the tempered crystallized glass using a lithium aluminosilicate-based base material, the refractive index of the base glass is 1.52, and the refractive index of the precipitating beta spodium is 1.66. The volume ratio of the precipitated crystals to the base material is about 10 to 50%, and the total refractive index changes depending on the volume ratio of crystallization. That is, the volume ratio of crystallization can be calculated by measuring the refractive index of the reinforced crystallized glass.

(Measurement example 4 of physical quantity related to the strength of tempered glass)
FIG. 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 can be estimated from the amplitude value of the glass surface. Further, the internal haze value can be estimated from the attenuation curve of the amplitude value inside the glass. Furthermore, the transmittance can be estimated by using the external haze value and the internal haze value. If one haze value is small, it may be estimated using only the other haze value. Further, by using a plurality of laser beams, the transmittance for each wavelength may be estimated and the color of the tempered glass may be estimated. Further, by measuring both sides of the glass, the difference in the glass surface layer may be investigated from the difference in the scattered light luminance amplitude value and the difference in the transmittance, and the surface of the glass may be determined. Specifically, an anti-glare surface, an anti-fingerprint surface, an AR coating surface, an antibacterial surface, an ITO surface, a float transport surface (tin surface) and the like can be considered.

The measured values of the scattered light brightness amplitude value As, the average scattered light brightness Is, the dispersion value Ss and the refractive index of the glass shown in the above measurement examples 1 to 4 are not limited to the reinforced crystallized glass and are not crystallized. Even in tempered glass, it is useful as a numerical value indicating glass defects such as impurities and abnormal crystals, composition, and quality such as non-uniformity and transparency. That is, the measurement shown in FIG. 14 may be performed after the step of applying a tempering treatment to the base plate to produce tempered glass (not tempered crystallized glass). Further, physical quantities other than those shown in the above measurement examples 1 to 4 may be measured.

As described above, unlike the stress measuring device using the waveguide light on the surface, the evaluation device 1 does not perform the stress measurement depending on the refractive index distribution of the tempered glass, but performs the measurement based on the scattered light. Therefore, regardless of the refractive index distribution of the tempered glass (regardless 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 can be measured for lithium-aluminosilicate-based tempered glass, which has the characteristic that the refractive index increases with depth from a certain depth.

Further, the polarization phase difference of the laser light is continuously changed by one or more wavelengths with respect to the wavelength of the laser light by the polarization phase difference variable member 30. Therefore, the phase of the periodic luminance change of the scattered light can be obtained by the least squares method of trigonometric functions or the Fourier integral. In the least squares method of trigonometric functions and the Fourier integral, unlike the conventional method of detecting the phase by changing the position of the peak or valley of the wave, all the data of the wave is handled and the period is known in advance. Since it is based on it, it is possible to remove noise of other periods. As a result, it is possible to easily and accurately determine the phase of the periodic luminance change of the scattered light.

Further, in the evaluation device 1, the physical quantity related to the strength of the tempered glass can be measured by using the same image as the image captured for measuring the stress distribution. As a result, physical quantities related to strength can be efficiently measured, and tempered glass can be widely evaluated.

<Modification 1 of the first embodiment>
Modification 1 of the first embodiment shows an example of an evaluation device having a different configuration from that of the first embodiment. In the first modification of the first embodiment, the description of the same component as that of the above-described embodiment may be omitted.

FIG. 18 is a diagram illustrating an evaluation device according to a modification 1 of the first embodiment. As shown in FIG. 18, the evaluation device 1A differs 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. In FIG. 18, the calculation unit is not shown.

The optical wavelength selection members 81 and 82 are, for example, two types of bandpass filters having different transmission wavelength bands, and can be switched manually or automatically.

Similar to the light wavelength selection member 80 of the first embodiment, the light wavelength selection member 81 does not transmit light having a wavelength other than the wavelength of the laser beam L by 50% or more, preferably 90% or more. Further, the width of the wavelength transmitted through the light wavelength selection member 81 is preferably about 10 nm or less.

The optical wavelength selection member 82 is a bandpass filter that transmits light having a wavelength different from the wavelength of the laser beam L, and the center wavelength coincides with, for example, the Raman scattering wavelength peculiar to the tempered glass to be measured or the fluorescence scattering wavelength. Can be made to. The width of the wavelength of the light transmitted through the light wavelength selection member 82 does not necessarily have to be as narrow as that of the light wavelength selection member 81.

In the evaluation device 1A, first, the light wavelength selection member 81 is used to measure the stress and the scattered light brightness. Next, the light wavelength selection member 81 is switched to the light wavelength selection member 82, and the scattered light brightness is measured. Then, the ratio of the scattered light brightness when the light wavelength selection member 81 is used and the scattered light brightness when the light wavelength selection member 82 is used is calculated. This makes it possible to know information about crystals precipitated in the tempered glass, a specific amount of impurities, and the like.

The light wavelength selection member is not limited to two types, and three or more types may be switchably arranged.

<Modification 2 of the first embodiment>
In the second modification of the first embodiment, another example of the evaluation device having a different configuration from the first embodiment is shown. In the second modification of the first embodiment, the description of the same component as that of the above-described embodiment may be omitted.

FIG. 19 is a diagram illustrating an evaluation device according to a 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 light wavelength selection member 80 is replaced with the light wavelength selection members 81 and 82. 1) is different. In FIG. 19, the calculation unit is not shown.

The laser light sources 11 and 12 are two types of lasers having different oscillating wavelengths. The optical wavelength selection members 81 and 82 are, for example, two types of bandpass filters having different transmission 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, so that the switching can be performed manually or automatically.

The wavelengths of the laser light sources 11 and 12 can be appropriately selected from, for example, 405 nm, 520 nm, 640 nm, 850 nm and the like. For the optical wavelength selection members 81 and 82, a bandpass filter that transmits only the vicinity of the wavelengths of the selected laser light sources 11 and 12 can be appropriately selected.

In the evaluation device 1B, the scattered light brightness amplitude value As, the average scattered light brightness Is, the dispersion value Ss and the like can be measured by using the laser light sources 11 and 12 having different wavelengths and the light wavelength selection members 81 and 82. Since the scattered light brightness and behavior sensitively affect the relationship between the wavelength and the scattered particle size, it is possible to know a more reliable crystallization state by obtaining information from the scattered light at a plurality of wavelengths.

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

Further, the same effect can be obtained by using a plurality of evaluation devices 1 provided with lasers having different wavelengths and optical wavelength selection members instead of the evaluation device 1B.

<Modification 3 of the first embodiment>
Modification 3 of the first embodiment shows still another example of the evaluation device having a different configuration from that of the first embodiment. In the third modification of the first embodiment, the description of the same component as that of the above-described embodiment may be omitted.

FIG. 20 is a diagram illustrating an evaluation device according to a modification 3 of the first embodiment. As shown in FIG. 20A, in the evaluation device 1C, the light wavelength selection member 80, the light conversion member 50, and the image pickup element 60 are arranged on the opposite side of the tempered glass 200 from the light supply member 41. Further, the light extraction member 42 is arranged so as to be in contact with the back surface 220 of the tempered glass 200, which is different from the evaluation device 1 (see FIG. 1). In FIG. 20, the calculation unit is not shown.

In the evaluation device 1C, the scattered light _LS2 generated on the back surface 220 side of the tempered glass 200 is incident on the image sensor 60 via the light extraction member 42 such as a prism, the light wavelength selection member 80, and the light conversion member 50. Then, a plurality of images are taken by the image sensor 60 at intervals of time within a certain period of time. Other configurations and operations are the same as those in the first embodiment.

By providing the light supply member 41, the reflection of the laser beam L on the surface 210 of the tempered glass 200 can be reduced, but if the reflection of the laser beam L on the surface 210 of the tempered glass 200 is not a problem, the reflection can be reduced. The laser beam L may be directly incident on the strengthened 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 surfaces, the scattered light Ls on the front surface 210 side (incident side of the laser beam L) of the tempered glass 200 is detected as in the first embodiment. Alternatively, as in the first modification of the first embodiment, the scattered light LS2 on the back surface 220 side (emission side of the laser beam L) of the _tempered glass 200 may be detected.

When detecting the scattered light _LS2 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 condition of total reflection. This is because if the laser light is totally reflected on the back surface 220 of the tempered glass 200, the diffused reflection on the back surface 220 of the tempered glass 200 can be reduced and unnecessary light can be prevented from being incident on the image pickup element 60. By adjusting the incident angle of the laser beam on the tempered glass 200, the laser beam can satisfy the condition of total internal reflection on the back surface 220 of the tempered glass 200.

Alternatively, as in the evaluation device 1D shown in FIG. 20B, the scattered light _LS3 generated on the front surface 210 side of the tempered glass 200 and emitted to the back surface 220 side is selected by the light extraction member 42 such as a prism and the optical wavelength selection. A plurality of images may be captured by the image pickup device 60 at intervals of time within a certain period of time by incident on the image pickup element 60 via the member 80 and the light conversion member 50. Other configurations and operations are the same as those in the first embodiment.

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

In both cases of the evaluation devices 1C and 1D, similarly to the evaluation device 1, the tempered glass 200 is based on the phase change of the periodic luminance change of the scattered light along the laser beam L incident on the tempered glass 200. The stress distribution in the depth direction from the back surface 220 of the glass can be calculated.

In particular, according to the evaluation device 1D, the focal point 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 a similar stress distribution, it is not necessary to adjust the focal position of the laser, or fine adjustment is sufficient, so the measurement time is short and the repeatability is further improved. It plays the effect.

<Variation Example 4 of the First Embodiment>
Modification 4 of the first embodiment shows still another example of the evaluation device having a different configuration from that of the first embodiment. In the fourth modification of the first embodiment, the description of the same component as that of the above-described embodiment may be omitted.

FIG. 21 is a diagram illustrating an evaluation device according to a modification 4 of the first embodiment. As shown in FIG. 21, in the evaluation device 1E, the light wavelength selection member 80A, the light conversion member 50A, and the image pickup element 60A are arranged on the opposite side of the tempered glass 200 from the light supply member 40, and further. It differs from the evaluation device 1 (see FIG. 1) in that the light extraction member 42 is arranged so as to be in contact with the back surface 220 of the tempered glass 200. In FIG. 21, the calculation unit is not shown.

Similar to the evaluation device 1, the evaluation device 1E can detect the scattered light _LS emitted from the surface 210 side of the tempered glass 200. Further, in the evaluation device 1E, the scattered light _LS2 emitted from the back surface 220 side of the tempered glass 200 is passed through the light extraction member 42 such as a prism, the light wavelength selection member 80A, and the light conversion member 50A to the image sensor 60A. And a plurality of images are taken by the image sensor 60A at intervals of time within a certain period of time. The operation other than this is the same as that of the first embodiment.

With the configuration of FIG. 21, the evaluation device 1E can simultaneously calculate the stress distribution in the depth direction from the front 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. It is effective when measuring tempered glass whose front and back surfaces do not have the same stress distribution, or when it is desired to confirm whether or not the front and back surfaces have the same stress distribution in any tempered glass.

<Variation Example 5 of the First Embodiment>
Modification 5 of the first embodiment shows an example of a variable polarization phase difference member having a different configuration from that of the first embodiment. In addition, in the modification 5 of the first embodiment, the description of the same component as the already described embodiment may be omitted.

As the polarization phase difference variable member, the photoelastic effect of the transparent material can be utilized, and the polarization phase difference can be changed by pressurization. FIG. 22 is an explanatory diagram of a polarization phase difference variable member utilizing a photoelastic effect.

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

The two surfaces 310a and 310b facing each other in the direction perpendicular to the surface of the material 310 for generating the polarization phase difference, which is in contact with the piezo element 312, are mirror-processed so that the polarized light rays Q can pass through. As the material for generating the polarization phase difference 310, a transparent material having a large photoelastic effect, for example, quartz glass for glass and polycarbonate for 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 depends on whether the voltage is positive or negative. Although not shown in FIG. 22, a piezo element drive voltage generation circuit that controls the voltage applied to the piezo element 312 is connected to the piezo element 312.

When a voltage that extends the piezo element 312 is applied by the piezo element drive voltage generation circuit, the length of the piezo element 312 tends to increase in the direction in which the voltage is applied, but the polarization phase difference generating material 310 in the extending direction. The piezo element 312 is arranged so that

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

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

As the piezo element 312, for example, a laminated piezo element in which high-dielectric ceramics having a perovskite crystal structure such as lead zirconate titanate having a large piezo effect are alternately stacked with electrodes can be used. For example, in a laminated piezo element, by setting the thickness of one layer to 200 μm to 100 layers and the length to about 20 mm, it is possible to obtain an elongation of 10 μm or more at 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 10 times or more that of polycarbonate, almost all the elongation of the piezo element 312 is the compression of polycarbonate, and when the piezo element 312 is extended by 10 μm, it is 10 mm. The cubic polycarbonate is compressed by 0.1%, and the compressive stress at that time is 2.5 MPa. When the light ray Q passes through the 10 mm polarization phase difference generating material 310, a polarization phase difference of 1750 nm is generated, and if the wavelength is 630 nm, the polarization phase difference of 2.8λ can be varied.

For example, a 10 mm cubic quartz glass is used as the polarization retardation generating material 310. The photoelastic constant of quartz glass is about 35 nm / cm / MPa, and 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 the same level as that of quartz, the elongation of the piezo element 312 is almost half of the compression of quartz glass, and when the piezo element 312 is extended by 10 μm, it is 10 mm. The cubic polycarbonate is compressed by about 0.05%, and the compressive stress at that time is about 35 MPa. When the light ray 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 deforming the material in this way to create a polarization phase difference, the value obtained by multiplying the photoelastic constant and Young's modulus is important. In the case of polycarbonate, 0.18 (no unit), and in the case of quartz, 0.26 (no unit). ). That is, it is important to use a transparent member having this value of 0.1 or more as the polarization phase difference generating material 310.

As described above, the variable polarization phase difference member is not limited to the liquid crystal element, and the polarization phase difference when incident on the tempered glass 200 can be changed with time, and the changing polarization phase difference is the laser. As long as it can be realized that the wavelength is 1 times or more of the wavelength λ of light, the form may be an application of the piezo element, or any other form may be used.

<Second embodiment>
The second embodiment shows an example of an evaluation device used in combination with the evaluation device according to the first embodiment. In the second embodiment, the description of the same component as that of the above-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 (Ceramics Association Journal) 87 {3} 1979 and the like. 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, a polarizing member 55, an image pickup element 65, and a calculation unit 75. .. The evaluation device 2 can be used in combination with the evaluation device 1 shown in FIG. The evaluation device 2 may be used in combination with 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 1E shown in FIG.

In the evaluation device 2, the light source 15 is arranged so that the light ray La is incident on 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 single wavelength that provides a simple light / dark display.

As the light source 15, for example, a Na lamp that can easily obtain light having a single wavelength can be used, and the wavelength in this case is 589.3 nm. Further, as the light source 15, a mercury lamp having a shorter wavelength than that of the Na lamp may be used, and the wavelength in this case is, for example, 365 nm, which is a mercury I line. However, since the mercury lamp has many emission lines, it is preferable to use it through a bandpass filter that transmits only the 365 nm line.

Further, an LED (Light Emitting Diode) may be used as the light source 15. In recent years, LEDs having many wavelengths have been developed, but the spectral width of the LED is 10 nm or more in half width, the monochromaticity is poor, and the wavelength changes depending on the temperature. Therefore, it is preferable to use it through a bandpass filter.

When the light source 15 is configured by passing an LED through a bandpass filter, it is not as monochromatic as a Na lamp or a mercury lamp, but it is preferable in that an arbitrary wavelength can be used from the ultraviolet region to the infrared region. Since the wavelength of the light source 15 does not affect the basic principle of measurement of the evaluation device 2, a light source other than the wavelengths exemplified above may be used.

However, by using a light source that irradiates ultraviolet rays as the light source 15, the resolution of 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. do. On the other hand, if a light source that irradiates light having a wavelength longer than that of ultraviolet rays is used as the light source 15, the number of interference fringes is reduced and the resolution is lowered.

The light supply member 25 and the light extraction member 35 are placed in a state of being 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 incidenting the light from the light source 15 onto the tempered glass 200. The light extraction member 35 has a function of emitting light propagating through 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, on the surface 210 of the tempered glass 200, the refractive index of these prisms needs to be larger than the refractive index of the tempered glass 200 in order for light rays to be optically incident and emitted through these prisms. Further, it is necessary to select a refractive index such that the incident light and the emitted light pass substantially vertically on the inclined surface of each prism.

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. As the light supply member 25 and the light extraction member 35, other members having the same function may be used instead of the prism. Further, the light supply member 25 and the light extraction member 35 may be integrated. Further, in order to ensure stable optical contact, the refractive index of the light supply member 25 and the light extraction member 35 and the refractive index of the tempered glass 200 are set between the light supply member 25 and the light extraction member 35 and the tempered glass 200. It may be filled with a liquid (which may be in the form of a gel) having a refractive index that is between the values.

The image pickup element 65 is arranged in the direction of the light emitted from the light extraction member 35, and the light conversion member 45 and the polarizing member 55 are inserted between the light extraction member 35 and the image pickup element 65.

The light conversion member 45 has a function of converting light rays emitted from the light extraction member 35 into an emission line train and condensing them on the image pickup device 65. As the light conversion member 45, for example, a convex lens can be used, but other members having the same function may be used.

The polarizing member 55 is a light separation means having a function of selectively transmitting one of two types of light components that vibrate parallel and perpendicular to the boundary surface 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 or the like can be used, but other members having the same 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 vertically is P-polarized light.

The boundary surface between the tempered glass 200 and the light extraction member 35 is perpendicular to the emission surface of the light emitted to the outside of the tempered glass 200 via the light extraction member 35. Therefore, the light component that vibrates perpendicularly to the emission surface of the light emitted to the outside of the tempered glass 200 via the light extraction member 35 is S-polarized light, and the light component that vibrates in parallel is P-polarized light. May be good.

The image pickup device 65 has a function of converting the light emitted from the light extraction member 35 and received through the light conversion member 45 and the polarizing member 55 into an electric signal. As the image sensor 65, for example, the same element as the image sensor 60 can be used.

The calculation unit 75 has a function of taking image data from the image sensor 65 and performing image processing and numerical calculation. The calculation unit 75 may be configured to have other functions (for example, a function of controlling the light amount and the exposure time of the light source 15). The arithmetic unit 75 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), a main memory, and the like.

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

In the evaluation device 2, the light rays La incident on the surface layer of the tempered glass 200 from the light source 15 through the light supply member 25 propagate in the surface layer. Then, when the light ray La propagates in the surface layer, a mode is generated by the optical waveguide effect, and the light ray La is taken out of the tempered glass 200 by the light extraction member 35 along some fixed paths.

Then, the light conversion member 45 and the polarizing member 55 form an image on the image pickup device 65 as bright lines of P-polarization and S-polarization for each mode. The image data of the P-polarized and S-polarized emission lines of the number of modes generated on the image sensor 65 is sent to the calculation unit 75. The calculation unit 75 calculates the positions of the P-polarized and S-polarized emission lines on the image sensor 65 from the image data sent from the image sensor 65.

With such a configuration, the evaluation device 2 obtains the refractive index distributions of the P-polarized and the S-polarized particles in the depth direction from the surface of the surface layer of the tempered glass 200 based on the positions of the emission lines of the P-polarized and the S-polarized glass. Can be calculated. Further, the stress distribution in the depth direction from the surface of the surface layer of the tempered glass 200 can be calculated based on the calculated difference in the refractive index distributions of the P-polarization and the S-polarization and the photoelastic constant of the tempered glass 200.

As described above, the evaluation device 2 is an evaluation device capable of measuring the stress distribution by using the waveguide light of the surface layer of the tempered glass. Here, the waveguide light on the glass surface is generated in the layer in which the refractive index of the tempered glass 200 becomes lower as it gets deeper from the surface. As the depth increases, waveguide light is not generated in the layer where the refractive index increases. For example, in lithium-aluminosilicate glass, the refractive index decreases as the refractive index increases only near the outermost surface of the glass, but the refractive index increases with the depth from a certain depth. In the case of such tempered glass, the waveguide light is generated only in the outermost surface layer which becomes lower as the refractive index becomes deeper, and the stress distribution can be measured at that portion, that is, at the depth where the refractive index distribution is inverted.

On the other hand, in the image of the scattered light shown in FIG. 9 of the first embodiment, the point A in FIG. 9 is the glass surface, and the surface scattered light is strongly spread around. This spread surface scattered light reflects the information of the surface points. At the surface point A, the information is correct, but for example, the scattered light of the laser beam L in the deep part of the glass from the surface point A is the scattered light reflecting the original stress of the glass at that point, and the surface point A. It is a state in which scattered light reflecting the stress in the above is mixed, and it is difficult to measure the stress correctly in the portion where the surface scattered light overlaps.

The depth of the portion where the 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 tempered glass is deep, and in the vicinity of the outermost surface, for example, in the surface region with a depth of about several tens of μm, the change in the stress depth direction is gradual, the surface stress value is low, or the tempered layer is deeply tempered. With glass, accurate stress can be estimated even if the depth is within 10 μm, which is not measured accurately, even if the stress distribution in the deeper part is extrapolated to the glass surface.

However, in tempered glass in which the stress distribution of the tempered glass 200 suddenly increases near the outermost surface, for example, between the surface of the tempered glass 200 and a depth of 10 μm, the stress value near the outermost surface due to extrapolation. There is a large error in the estimated value of. In particular, the stress value on the outermost surface has a large error. However, the stress distribution can be accurately measured as an absolute value except in the region where the surface scattered light interferes.

Of the stress value or stress distribution measured by the evaluation device 2 for the stress value on the outermost surface or the stress distribution near the outermost surface, and the stress distribution measured by the evaluation device 1, sufficient from the outermost surface that is not obstructed by the surface scattered light. By matching the stress distribution in the deep part, the overall stress distribution can be measured accurately.

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

FIG. 24 is a diagram showing the stress distribution measured by the evaluation devices 1 and 2 in the same graph. More specifically, the outermost surface of the tempered glass having a stress distribution chemically strengthened in two steps, which has a region where the stress gradient changes suddenly in the vicinity of a depth of 10 μm from the surface, is measured by the evaluation device 2. The stress distribution in the vicinity (region A) and the stress distribution in a sufficiently reliable region measured by the evaluation device 1 (region C) 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, the curve obtained by the least squares method using the function of the stress distribution expected in region B is shown by the dotted line. In this case, even if there is no actual data of the region including the bending point, the bending point position can be estimated from the curve obtained by the least squares method.

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

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

Next, in step S409, the light conversion member 45 and the polarizing member 55 each have at least two types of optical components (P-polarization and S-polarization) that vibrate parallel and perpendicular to the emission surface of the emitted light. It is converted as two kinds of emission line trains having two or more emission lines (optical conversion step).

Next, in step S410, the image pickup device 65 images two types of emission line trains converted by the optical conversion step (imaging step). Next, in step S411, the position measuring means 751 of the calculation unit 75 measures the position of each emission line of the two types of emission line trains from the image obtained in the imaging step (position measurement step).

Next, in step S412, the stress distribution calculation means 752 of the calculation unit 75 is deep from the surface of the tempered glass 200 corresponding to the two types of light components from the positions of at least two or more emission lines in each of the two types of emission line trains. Calculate the index of refraction distribution over the vertical direction. Then, the stress distribution from the surface of the tempered glass 200 to the depth direction is calculated based on the difference in the refractive index distributions of the two types of light components and the photoelastic constant of the glass (stress distribution calculation step).

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

When 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 arithmetic unit 75 may be, for example, as shown in FIG. 24. At least two based on the stress distribution in the region A calculated by the stress distribution calculation means 752 of the calculation unit 75 of the evaluation device 2 and the stress distribution in the region C calculated by the stress distribution calculation means 703 of the calculation unit 70 of the evaluation device 1. Calculate the stress distribution in region B by multiplication or the like.

In addition to the configuration of FIG. 26, the calculation unit 75 may include a CT value calculation means for calculating a CT value, a DOL_Zero value calculation means for calculating a DOL_Zero value, and the like. In this case, the CT value and the 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. FIG. 27 is a diagram illustrating the stress distribution in the depth direction of the tempered glass. In FIG. 27, CS2 is the stress value on 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 stress value. Is the glass depth at which zero, and DOL_til 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 based on the stress distribution measured in step S501 in step S502. This will be described in more detail below.

FIG. 29 shows an example in which each characteristic value is derived from the measured stress distribution. For example, in step S601 of FIG. 30, the entire distribution of the 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, for example, each characteristic value is derived 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. Then, when the difference between the two line segments and the measured stress distribution is minimized, the intersections of the two line segments are defined as CS_TP and DOL_TP. Further, the intersection of the line segment passing through DOL_zero and CT is defined as DOL_tail.

This method uses, for example, lithium-aluminosilicate tempered glass, tempered glass that has been chemically strengthened once using a mixed salt of sodium nitrate and potassium nitrate, and a molten salt containing sodium nitrate and a molten salt containing potassium nitrate. It can be applied to tempered glass that has been chemically strengthened by using and once or more, and tempered glass that has been chemically strengthened by both wind cooling and chemical strengthening.

FIG. 31 shows another example in which each characteristic value is derived from the measured stress distribution. For example, in step S601 of FIG. 32, the entire distribution of the stress distribution is measured by the evaluation device 1. Next, in step S602, the glass surface layer side of DOL_TP is measured by the evaluation device 2. It is difficult for the evaluation device 2 to measure the deeper side than DOL_TP. Step S601 and step S602 are in no particular order.

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

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

Quality judgment can be made using each characteristic value obtained by measuring the stress distribution. FIG. 34 is an example of a flow chart for quality judgment using each characteristic value obtained by measuring the stress distribution. In FIG. 34, first, steps S601 to S603 are executed in the same manner as in FIG. 32. Next, in step S604, based on the data obtained in steps S601 and S602, six characteristic values of CS2, CS_TP, CT, DOL_TP, DOL_zero, and DOL_tail (hereinafter, may be simply referred to as six measured values). Is derived. Next, in step S605, it is determined whether or not the six characteristic values derived in step S604 are within the permissible range defined in the prior required specifications. In this method, two measurements of steps S601 and S602 are required for one quality judgment.

FIG. 35 is another example of a flow chart of quality judgment using each characteristic value obtained by measuring the stress distribution. In FIG. 35A, first, preliminary data is acquired in step S600. Specifically, for example, six characteristic values are derived for a predetermined quantity per lot by using the evaluation devices 1 and 2. Then, the allowable range of the characteristic value is determined based on the required specifications of the product and the derived characteristic value.

Next, in step S601, the deep glass side of DOL_TP is measured by 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 or not the six characteristic values measured in step S604 fall within the allowable range determined in step S600. In this method, for the quantity other than the quantity measured in the preliminary step, only one measurement in step S601 is required for one quality determination. Therefore, the quality control flow can be simplified as compared with the case of FIG. 34.

In the preliminary data of FIG. 35 (a), the plate thickness may be measured together, and the plate thickness may be measured in step S601 to derive the characteristic value including the effect of different plate thickness in step S604.

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

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

Next, in step S605, it is determined whether or not the six characteristic values measured in step S604 fall within the allowable range determined in step S600. In this method, for the quantity other than the quantity measured in the preliminary step, only one measurement in step S602 is required for one quality determination. Therefore, in this case as well, the quality control flow can be simplified as compared with the case of FIG. 34 (a).

In the preliminary data of FIG. 35 (b), the plate thickness may be measured together, and the plate thickness may be measured in step S602 to derive the characteristic value including the effect of different plate thickness in step S604.

FIG. 36 is an example of a flow chart for quality judgment when a lithium-containing glass (glass containing 2 wt% or more of lithium) such as a lithium-aluminosilicate tempered glass is toughened twice or more. In FIG. 36, the tempered glass related to the strengthening other than the final round is judged to pass or fail based on the measurement result of the evaluation device 1, and the tempered glass related to the strengthening of the final round is judged to pass or fail based on the measurement result of the evaluation device 2.

Specifically, first, the first chemical strengthening is performed in step S650. Then, in step S651, the stress distribution on the deep glass side of DOL_TP (hereinafter, may be referred to as the first stress distribution) is measured by the evaluation device 1. If there is a problem with the measurement result in step S651 (in the case of NG), the tempered glass will not be shipped. 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 the second chemical strengthening is performed. The pass / fail determination (OK / NG determination) in step S651 can be performed based on all or a part (for example, CT and DOL_zero) of the six characteristic values derived from the measurement result of the evaluation device 1.

Next, in step S653, the stress distribution on the glass surface layer side of DOL_TP (hereinafter, may be referred to as a second stress distribution) is measured by the evaluation device 2. If there is a problem with the measurement result in step S653 (in the case of NG), the tempered glass will not be shipped. 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 of step S654. A specific method of pass / fail determination (OK / NG determination) in step S653 will be described later.

Examples of the next step include a touch polish step. The touch polishing step is, for example, a finish polishing step of polishing the surface of the tempered glass 200 with a relatively low surface pressure. However, it is not essential to provide the touch polish step, and step S653 may be the final step.

Further, after step S653, the third chemical strengthening and pass / fail determination may be performed. In this case, in step S653, the tempered glass related to the second strengthening is judged as pass / fail based on the measurement result of the evaluation device 1 in the same manner as in step S651, and the tempered glass related to the third strengthening (final strengthening) is used. A pass / fail judgment is made based on the measurement result of the evaluation device 2.

The same applies when the number of times of strengthening is further increased. The tempered glass related to the strengthening other than the final round is judged as pass / fail based on the measurement result of the evaluation device 1, and the tempered glass related to the final round of strengthening is measured by the evaluation device 2. Pass / fail judgment is made based on the result. This makes it possible to shorten the evaluation time while maintaining the measurement reproducibility.

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

(Derivation of evaluation data)
First, evaluation data is derived in advance. Specifically, as shown in FIG. 37, the first chemical strengthening is performed in step S660. Then, in step S661, the deep glass side of DOL_TP is measured by the evaluation device 1 (first measurement). Subsequently, the second chemical strengthening is performed in step S662. Then, in step S663, the deep glass side of 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.

The evaluation data is derived using only a predetermined quantity per lot. Further, the first chemical strengthening and the second chemical strengthening in the derivation of the evaluation data are performed under the same conditions as the first chemical strengthening and the second chemical strengthening at the time of mass production.

(Method of pass / fail determination in step S653)
First, based on the measurement results obtained in step S653, the plate thickness t of the chemically strengthened glass, and the evaluation data obtained as shown in FIG. 37, the stress distribution on the glass surface layer side of DOL_TP (second). The stress distribution) and the stress distribution on the deep glass side of DOL_TP (first stress distribution) are combined. For example, the result shown in FIG. 38 is obtained.

In FIG. 38, the FSM shown by the solid line shows the stress distribution on the glass surface layer side of DOL_TP (second stress distribution), and the SLP shown by the broken line shows the stress distribution on the glass deep layer side of DOL_TP (first stress distribution). ) Is shown. Further, t / 2 indicates the center of the thickness of the glass. Further, CS ₀ indicates the stress value of the surface when the first stress distribution (SLP) is extended toward the surface side of the tempered glass.

Next, CT is found from the stress distribution after synthesis, each characteristic value is derived, and pass / fail judgment (shipment judgment) is performed depending on whether or not each characteristic value is within the allowable range.

At this time, the second stress distribution (FSM in FIG. 38) may be function-approximate. As an example of function approximation, linear approximation can be given by the following equation 2 (Equation 2).

式２において、σｆ（ｘ）は第２の応力分布、ａは傾き、ＣＳ２は最表面の応力値である。

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

As another example of function approximation, curve approximation can be given by the following equation 3 (Equation 3).

式３において、σｆ（ｘ）は第２の応力分布、ａは傾き、ＣＳ２は最表面の応力値、ｅｒｆｃは式４（数４）に示す誤差関数である。

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

関数近似の更に他の例としては、多項式近似することが挙げられる。

Yet another example of function approximation is polynomial approximation.

Further, the first stress distribution (SLP in FIG. 38) may be moved in the vertical direction (stress value axis direction) in FIG. 38. Specifically, for example, in the stress distribution after synthesis shown in FIG. 38, the first stress distribution (SLP) is moved in the stress value axis direction, and a CT in which the integrated value of the stress distribution after synthesis becomes zero is found. Each characteristic value is derived. Then, a pass / fail determination (shipment determination) can be performed depending on whether or not each characteristic value is within the allowable range. At this time, the amount of vertical movement of the first stress distribution is assumed to be the amount of movement even if calculated from a theoretical formula based on the glass plate thickness and the second stress distribution, and after synthesis. The integrated value of the stress distribution may be calculated to find the amount of movement at which the integrated value becomes zero.

Further, the stress distribution σ (x) after synthesis is approximated by the following equation 5 (Equation 5), and the integral value of σ (x) (x = 0 to t / 2: t is the glass plate thickness) becomes zero. Find the CT and derive each characteristic value. Then, a pass / fail determination (shipment determination) may be performed depending on whether or not each characteristic value is within the allowable range.

式５において、σ（ｘ）は合成後の応力分布、σｆ（ｘ）は第２の応力分布、ｔは強化ガラスの板厚、ＣＳ_０及びｃは第１の応力分布に基づいて導出されるパラメータである。

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

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

CS ₀ and c may be obtained from a simulation based on the strengthening condition.

Alternatively, CS ₀ and c are CS _0'and c'derived from the measurement results of the tempered glass evaluation device 1 related to the strengthening one time before the final round in mass production, and the following formulas 6 (Equation 6) and 7 It may be obtained by (Equation 7).

式６において、Ａ１は比例定数である。

In Equation 6, A1 is a constant of proportionality.

式７において、Ａ２は比例定数である。

In Equation 7, A2 is a constant of proportionality.

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

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 two chemical strengthenings, was derived three times for the same sample by the method described with reference to FIG. 34, and the evaluation time and measurement reproducibility were derived. I checked.

In Example 2, CS_TP (MPa), which is a characteristic value of the stress distribution of the tempered glass subjected to two chemical strengthenings, was derived three times for the same sample by the methods described in FIGS. 36 to 38, and the evaluation time was set. The measurement reproducibility was investigated. Specifically, the second stress distribution (FSM) is based on the measurement result obtained in step S653 of FIG. 36, the plate thickness t of the chemically strengthened glass, and the evaluation data obtained as shown in FIG. 37. ) And the first stress distribution (SLP), move the first stress distribution (SLP) in the direction of the stress value axis, and find a CT in which the integrated value of the stress distribution after synthesis becomes zero. CS_TP was derived.

In Example 3, CS_TP (MPa), which is a characteristic value of the stress distribution of the tempered glass subjected to two chemical strengthenings, was derived three times for the same sample by the methods described in FIGS. 36 to 38, and the evaluation time was set. The measurement reproducibility was investigated. Specifically, the second stress distribution (FSM) is based on the measurement result obtained in step S653 of FIG. 36, the plate thickness t of the chemically strengthened glass, and the evaluation data obtained as shown in FIG. 37. ) And the first stress distribution (SLP), the stress distribution σ (x) after synthesis is approximated by Equation 5, and the integrated value of σ (x) (x = 0 to t / 2: t). Found a CT with zero glass plate thickness) and derived CS_TP.

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

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

表２より、比較例１では、同一サンプルについて３回導出したＣＳ_ＴＰの値が毎回ばらついており、測定再現性が良くない。これに対して、実施例１～３では、同一サンプルについて３回導出したＣＳ_ＴＰの値のばらつきが少なく、比較例１に比べて測定再現性が大幅に向上している。特に、実施例２及び３では、測定再現性が優れている。又、実施例１は評価時間が長いが、実施例２及び３では評価装置１による測定回数が減ったため、評価時間が短く、かつ測定再現性に優れていることが確認できた。

From Table 2, in Comparative Example 1, the value of CS_TP derived three times for the same sample varies every time, and the measurement reproducibility is not good. On the other hand, in Examples 1 to 3, the variation in the value of CS_TP derived three times for the same sample is small, and the measurement reproducibility is significantly improved as compared with Comparative Example 1. In particular, in Examples 2 and 3, the measurement reproducibility is excellent. Further, it was confirmed that the evaluation time was long in Example 1, but the number of measurements by the evaluation device 1 was reduced in Examples 2 and 3, so that the evaluation time was short and the measurement reproducibility was excellent.

<Third embodiment>
In the third embodiment, an example in which a liquid is sandwiched between the light supply member and the tempered glass is shown. In the third embodiment, the description of the same component as that of the above-described embodiment may be omitted.

FIG. 40 is a diagram illustrating the evaluation device according to the third embodiment, and shows a cross section in the vicinity of the interface between the light supply member and the tempered glass.

As shown in FIG. 40, in the present embodiment, a liquid 90 having a refractive index substantially equal to that of the tempered glass 200 is sandwiched between the light supply member 40 and the tempered glass 200. This is because the refractive index of the tempered glass 200 differs slightly depending on the type of tempered glass, and therefore, 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 replacement work is inefficient, a liquid 90 having a refractive index almost equal to that of the tempered glass 200 is sandwiched between the light supply member 40 and the tempered glass 200, so that the laser can be efficiently contained in the tempered glass 200. Light L can be incident.

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

At this time, the difference in refractive index 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. In the absence of the liquid 90, scattered light is generated between the tempered glass 200 and the light supply member, and data cannot be obtained within a range of about 20 μm.

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

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

When the thickness of the liquid 90 is thin, the points A and D become substantially the same points, and the surface scattering light is obtained by adding the surface scattering of the tempered glass 200 and the surface scattering of the light supply member 40. When many tempered glasses 200 are measured, the surface of the light supply member 40 is often scratched. Then, a very large surface scattered light is generated.

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

FIG. 42 is a diagram illustrating a structural portion for sandwiching the liquid 90 between the light supply member 40 and the tempered glass 200. As shown in FIG. 42 (a), a recess 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 in the recess 40x to stabilize the thickness of the liquid 90 to 10 μm. You can do the above. The depth of the dent 40x may be any number in principle, but it is preferably 500 μm or less in consideration of ease of processing.

Further, instead of forming a recess 40x on the surface of the light supply member 40, as shown in FIG. 42B, a thin film forming technique such as vacuum deposition or sputtering is used to form a metal, an oxide, or the like on the surface of the light supply member 40. A land member 100 having a thickness of 10 μm or more may be formed of a resin or the like to form a land of liquid 90 held by the land member 100. By holding the liquid 90 in the land member 100, the thickness of the liquid 90 can be stably increased to 10 μm or more. The thickness of the land member 100 may be any number in principle, but is preferably 500 μm or less in consideration of ease of processing.

<Modified example of the third embodiment>
In the modified example of the third embodiment, an example different from FIG. 42 of the structural portion for sandwiching the liquid 90 between the light supply member 40 and the tempered glass 200 is shown. In the modified example of the third embodiment, the description of the same component as that of the above-described embodiment may be omitted.

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

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

The recess 40x can be easily formed into a spherical recess by the same manufacturing method as that of the concave lens. Since the liquid 90 filled in the recess 40x has the same refractive index as the light supply member 40, the lens has no effect due to the liquid 90 in the spherical recess, and the trajectory of the laser light and the scattered light of the camera are captured. There is no effect on the image.

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

The one-sided concave lens 43 becomes a part of the optical path of the laser beam incident on the tempered glass 200 via the light supply member 40. For example, a spherical recess 43x is formed in the one-sided concave lens 43. The depth of the recess 43x is, for example, 10 μm or more and 500 μm or less.

The light supply member 40 and the one-sided concave lens 43 are 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 one-sided concave lens 43.

Since the optical adhesive that adheres the light supply member 40 and the one-sided concave lens 43 is exposed to laser light for a long time, it is desirable to use a highly durable adhesive.

In particular, when the wavelength of the light source is short and is close to ultraviolet rays or ultraviolet rays, for example, at a wavelength of 500 nm or less, the deterioration of the optical adhesive is remarkable. , It is desirable to use an inorganic adhesive or low melting point glass. Alternatively, it is desirable to bond the light supply member 40 and the one-sided concave lens 43 by an optical contact or the like that does not use an adhesive.

In the processing of general optical elements, the technique of forming a prism formed only by a flat surface and the process of forming a lens forming a spherical surface are different, and it is difficult to form a prism having a spherical surface shape, and many of them are used. The process is required, the productivity is poor, and the manufacturing cost is very high. That is, it is difficult to integrate the light supply member 40, which is a prism, with the one-sided concave lens 43.

However, the light supply member 40, which is a prism, and the one-sided concave lens 43 alone can be easily formed by the respective processing techniques. Further, a glass plate having substantially the same refractive index as the light supply member 40 and the one-sided concave lens 43 may be inserted between the light supply member 40 and the one-sided 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, the optical adhesive for adhering the light supply member 40 and the glass plate and the optical adhesive for adhering the glass plate and the one-sided concave lens 43 have a short wavelength of the light source and are inorganic when they are close to ultraviolet rays or ultraviolet rays. It is desirable to use adhesive or low melting point glass. Alternatively, it is desirable to bond the light supply member 40 and the glass plate, and the glass plate and the one-sided concave lens 43 by 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 sandwiching 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 one-sided concave lens 43. In the structure shown in FIG. 45, since the flat outer edge portion 43e is a surface in contact with the tempered glass 200, when the tempered glass 200 is brought into contact with the light supply member 40, it can be accurately paralleled to the tempered glass 200. Damage such as scratches can be eliminated.

FIG. 46 is a diagram showing a fifth example of a structural portion for sandwiching the liquid 90 between the light supply member 40 and the tempered glass 200. As shown in FIG. 46, the light supply member 40 and the one-sided concave lens 43 are not fixed with an optical adhesive, but a liquid having the same refractive index such as liquid 90 is sandwiched between the support 44 and the removable support 44. It may be fixed from the outer peripheral side surface so as not to move by using it.

By configuring the support 44 so that it can be opened and closed by using a spring or the like, only the one-sided concave lens 43 can be easily replaced. For example, when the single-concave lens 43 is damaged or scratched due to contact with the tempered glass 200, or when the single-concave lens 43 is changed to a single-concave lens 43 having a recess of another shape, a plurality of single-concave lenses 43 are manufactured and replaced. All you have to do is do it.

The shape and structure of the support 44 may be any shape as long as the one-sided concave lens 43 can be held interchangeably.

FIG. 47 is a diagram showing a sixth example of a structural portion for sandwiching the liquid 90 between the light supply member 40 and the tempered glass 200. As shown in FIG. 47, a groove 43y for discharging the liquid 90 may be formed in the flat outer edge portion 43e formed around the one-sided concave lens 43. The groove 43y communicates with the recess 43x.

When the liquid 90 is dropped into the recess 43x and the tempered glass 200 is placed on the recess 43x, bubbles may remain in the recess 43x. By providing a groove 43y for discharging the liquid 90 around the recess 43x, the liquid 90 is dropped into the recess 43x, and when the tempered glass 200 is placed, bubbles are also discharged from the groove 43y together with the liquid 90, so that the inside of the recess 43x It is possible to make it difficult for bubbles to remain.

As shown in FIG. 48, a groove 40y communicating with the recess 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 the groove 40y around the recess 40x to discharge the liquid 90, the liquid 90 is dropped into the recess 40x, and when the tempered glass 200 is placed, bubbles are also formed from the groove 40y together with the liquid 90. Since it is discharged, it is possible to prevent bubbles from remaining in the recess 40x.

In FIGS. 43 to 48, the intersecting curves drawn in the recesses 40x and 43x and the vertical lines drawn on the side surface of the one-sided concave lens 43 are drawn for convenience in order to make the drawing easier to see. It does not indicate an existing line (thin groove, protrusion, etc.).

Further, in the above, the recesses 40x and 43x have been described as spherical recesses, but the recesses 40x and 43x are not limited to spherical surfaces, and any surface having a curved portion may be used. The recess 40x or 43x may be, for example, an aspherical recess. Further, the groove shape and the number of grooves 40y and 43y may be arbitrarily set.

<Fourth Embodiment>
In the fourth embodiment, an example of an evaluation method considering the refractive index of tempered glass is shown. In the fourth embodiment, the description of the same component as that of the above-described embodiment may be omitted.

In the formula for obtaining the stress St from the polarization phase difference Rt at the depth D of the laser light, the photoelastic constant of the tempered glass is C, and the angle between the surface 210 of the tempered glass 200 of the laser light, that is, the incident margin angle (refraction angle). If Ψ, the following equation 8 (equation 8) is obtained.

式８において、最後のΨの項は、応力による複屈折のレーザ光への寄与分の補正である。すなわち、強化ガラス２００の強化による内部応力は表面２１０と平行であり、一方レーザ光は表面２１０に対し斜めに入射する。そのため、応力による複屈折のレーザ光への寄与分の補正が必要であり、式８の最後のΨの項が補正分となる。なお、この式でＳｔを用いているが、式１とは応力分布の座標系が異なるため、便宜上別の記号を用いている。

In Equation 8, the last Ψ term is the correction of the contribution of birefringence to the laser beam due to stress. That is, the internal stress due to the strengthening of the tempered glass 200 is parallel to the surface 210, while the laser beam is obliquely incident on the surface 210. Therefore, it is necessary to correct the contribution of birefringence to the laser beam due to stress, and the last Ψ term in Equation 8 is the correction. Although St is used in this equation, a different symbol is used for convenience because the coordinate system of the stress distribution is different from that in Equation 1.

FIG. 49 is a diagram illustrating that the laser beam L is incident on the tempered glass 200. In FIG. 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 in contact with the upper surface of the light supply member 40 and the upper surface of the light supply member 40 is located at xyz coordinates with the XZ plane as the XZ plane. is doing. Then, the laser beam L is incident on the incident end surface of the light supply member 40, passes through the boundary between the upper surface of the light supply member 40 and the surface of the tempered glass 200, and is incident on the tempered glass 200. The image sensor 60 captures a laser locus (trajectory of laser light L) from diagonally below 45 °.

FIG. 50 is a diagram illustrating an image of a laser trajectory taken from the position of the image pickup device 60 of FIG. 49. Let Cpass be the laser locus on the image captured by the image pickup element 60, Pc be the length, χ be the angle on the image of the laser locus, Lx be the horizontal distance on the image, and V be the vertical distance on the image. .. In the evaluation device 1, image analysis is performed from the image from the image pickup element 60 of the laser beam L (correctly, the scattered light from the laser beam L), and finally the stress in the tempered glass 200 is measured.

However, since the image acquired by the image sensor 60 is an image from diagonally 45 ° below, the length Pc of the laser locus Cpass on the image is not always the same as the actual length of the laser beam L, and the image. The upper angle χ is also not the actual incident margin Ψ. Therefore, in order to obtain the stress from the image of the laser beam L using the equation 8, a conversion formula for obtaining the actual distance P of the laser beam L and the incident margin angle Ψ is required.

FIG. 51 is a diagram illustrating definitions of an angle and a length of a laser beam in the light supply member 40 or the tempered glass 200 of FIG. 49. Here, consider a rectangular parallelepiped whose apex is abcdefgh. Let Lx be the length of the side bf, H be the length of the side ab, and D be the length of the side fg. D is the same as the depth of the light supply member 40 or the tempered glass 200. In FIG. 51, the laser beam L travels from the apex c to the apex e, and the Pass shows the locus of the laser beam L.

It is assumed that the upper surface abfe is parallel to the upper surface of the light supply member 40 of FIG. 49 and the surface of the tempered glass 200. Let P be the length ce of the trajectory Pass of the laser beam, and let Ψ be the incident margin angle with respect to the surface of the tempered glass 200. Further, the surface acge is equivalent to the incident surface of the laser beam L.

52 is a top view, a front view, and a side view of FIG. 51. The locus seen from the upper surface of the laser beam L is Upass, the length is Pu, the locus seen from the front is Fpass, the length is Pf, the locus seen from the side surface is Lpass, and the length is Pl. The angle ω of the locus Lpass of the laser beam L seen from the side surface is the incident surface angle of the laser beam L. φ is the Z-axis rotation angle of the laser beam L, and θ is the Y-axis rotation angle.

In FIG. 51, when H = D, ω is 45 ° and the incident surface of the laser beam L is 45 °. When H = D, the Z-axis rotation angle φ and the Y-axis rotation angle θ of the laser beam L are equal to each other in FIG. 52. Therefore, in order to make the incident surface of the laser beam L in the tempered glass 200 45 °, It can be seen that the angles of rotation of the Z-axis and the Y-axis of the laser beam L should be made equal.

Further, the length P of the laser beam trajectory Pass is given by the following equation 9 (Equation 9).

又、Ｌｘを単位長さ、例えば１とすると、φ、θより、Ｄ、Ｈ、Ｐｕは求まり、レーザ光の強化ガラス表面に対する入射余角ΨはＰａｓｓとＵｐａｓｓの角であるので、これらより、レーザ光Ｌの長さＰ、強化ガラス２００の表面に対する入射余角Ψは容易に求まる。

Further, when Lx is a unit length, for example, 1, D, H, and Pu can be obtained from φ and θ, and the incident margin angle Ψ with respect to the tempered glass surface of the laser beam is the angle between Pass and Upass. The length P of the laser beam L and the incident margin angle Ψ with respect to the surface of the tempered glass 200 can be easily obtained.

(When the refractive index of the light supply member is ng = the refractive index of tempered glass is ng)
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 and relationships of these lasers are the same in the light supply member 40 and the tempered glass 200. For example, the light supply member has a Y-axis rotation angle θ = 15 °, a Z-axis rotation angle φ = 15 °, and a refractive index ng = 1.516 of the tempered glass 200 in the light supply member 40 or the tempered glass 200. If the refractive index of 40 is also the same as that of the tempered glass, np = 1.516, the incident surface angle ω = 45 ° in the tempered glass 200 and the incident margin angle Ψ = 14.5 °.

From FIG. 50, if the incident surface is 45 °, the image is an image viewed perpendicular to the incident surface, and the distance Pc of the laser trajectory Cpass shown in FIG. 50 is the same as the distance P of the actual laser trajectory Pass. The actual depth D from the depth V on the image can be obtained by the following equation 10 (Equation 10).

これらより、レーザ光の撮像素子６０の画像より、強化ガラスの応力を算出可能である。

From these, the stress of the tempered glass can be calculated from the image of the image sensor 60 of the laser beam.

(In the case of the refractive index ng of the light supply member 40 ≠ the refractive index ng of the tempered glass 200)
The above description is for the case where the light supply member 40 and the tempered glass 200 have the same refractive index, and the laser beam advances without refraction 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 are strengthened. The laser light in the glass 200 is parallel. However, in reality, the refractive indexes of the light supply member 40 and the tempered glass 200 are not necessarily the same.

When the refractive indexes of the light supply member 40 and the tempered glass 200 are different, the Z-axis rotation angle of the laser beam does not change, and only the Y-axis rotation angle changes. Therefore, even if the incident surface of the laser beam in the tempered glass 200 is 45 ° when the refractive indexes of the light supply member 40 and the tempered glass 200 are the same, the refractive index of the tempered glass 200 is the refractive index of the light supply member 40. If it is different from the above, the incident surface of the laser beam of the tempered glass 200 deviates from 45 °. Then, the distance Pc of the laser locus Cpass shown in FIG. 50 is different from the distance P of the actual laser locus Pass (Pc ≠ P), and the equation 10 does not hold.

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

Further, since the laser light is incident on the light supply member 40 from the air, the angle formed by the angle before the laser light is incident on the light supply member 40 and the angle formed by the laser light on the incident end surface where the laser light of the light supply member 40 is incident. As a result, the laser light is refracted and incident on the light supply member 40. Therefore, the incident margin before the laser light is incident on the light supply member 40 and the angle of the incident end surface of the light supply member 40 are also taken into consideration, and the required incident margin and the incident surface angle of the laser light in the tempered glass 200 are considered. ..

In order to separate φ and θ in FIG. 52 from those in the tempered glass 200, the inside of the tempered glass 200 is φg and θg, the inside of the light supply member 40 is φp and θp, and the one before being incident on the light supply member 40 is φL and θL. Further, the Z-axis rotation angle β and the Y-axis rotation angle α of the incident end face on which the laser of the light supply member 40 is incident are set. Further, the refractive index of the light supply member 40 is np, and the refractive index of the tempered glass 200 is ng.

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

Here, the angles of rotation φL and θL before the light supply member 40 of the laser beam is incident, the angles of rotation β and α of the incident end face on which the laser beam of the light supply member 40 is incident, and the refractive index np of the light supply member 40 are determined. Determined by device design and known. The refractive index of the tempered glass 200 can be known by 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 by the device design, and the refractive index of the tempered glass 200, φg of the laser beam in the tempered glass 200, θg, incident margin angle Ψ, and incident surface angle ω are obtained, and a conversion formula from Pc and χ of the image of the image pickup element 60 of the laser light to the incident margin angle Ψ and the incident surface angle ω of the laser light in the tempered glass 200. The stress distribution in the tempered glass can be measured from Equation 8. A specific example is shown below.

FIG. 53 is a conceptual diagram of the laser beam traveling through the light supply member and the tempered glass. Although the angle is actually three-dimensional, it is shown two-dimensionally in FIG. 53 for convenience. FIG. 54 is a conceptual diagram of the laser beam traveling through the tempered glass, and FIG. 215 schematically shows the observation surface observed from the image pickup device 60 in a satin pattern.

In FIGS. 53 and 54, θL is an angle (laser side) formed by 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. Further, θ _P1 is the angle formed by 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), and θ _P2 is strengthened from the light supply member 40. It is an angle (on the light supply member 40 side) formed by the laser beam incident on the glass 200 and the normal line of the emission surface 40b of the light supply member 40. 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 at right angles, θ _P1 + θ _P2 = 90 ° is not always the case.

Further, θg is the angle formed by the laser beam incident on the tempered glass 200 from the light supply member 40 and the normal line of the emission surface 40b of the light supply member 40 (the tempered glass 200 side), and Ψ is the surface 210 (evaluation surface) of the tempered glass 200. ) And the incident margin angle (90-θg) formed by the laser beam in the tempered glass 200. Further, χ is the inclination of the laser beam observed from the image sensor 60. When considering θ, Ψ, etc. in three dimensions, they may be considered separately as shown in FIG. 52.

The incident margin 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 θ L and np. θ _P1 can be obtained from θL and np by 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 by 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 various types of tempered glass and the refractive indexes are different. However, the optical glass forming the light supply member 40 is not necessarily glass having exactly the same refractive index as tempered glass.

For example, the most commonly used optical glass S-BSL7 (manufactured by OHARA) has np = 1.516, the bottom is S-FSL5 (manufactured by OHARA) np = 1.487, and the top is S-TIL6 (manufactured by OHARA). Np = 1.5317 etc. can be obtained.

Therefore, when measuring tempered glass having a refractive index in a certain range, it is necessary to use a light supply member 40 made of optical glass having a refractive index close to that range. For example, when the refractive index of the tempered glass is ng = 1.51, the incident margin angle Ψ in the tempered glass is 13.7 ° and the incident surface angle ω is 43 °. From this, a conversion formula can be obtained, and an accurate stress can be obtained by the formula 8.

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 image pickup device 60. That is, the refractive index ng of the tempered glass 200 may be derived based on the image of the laser beam acquired by the image pickup device 60.

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

Next, in step S713, the incident margin angle Ψ is obtained from the relationship derived in step S711 using the angle χ measured in step S712. Further, θg = 90-Ψ can be obtained, and ng can be derived from the known θ _P2 , np, and θg by 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 image pickup element 60, and a conversion formula is obtained based on the refractive index ng of the tempered glass 200 to obtain the stress distribution of the tempered glass 200. It is also possible to measure.

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 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 accuracy, it is possible to measure the refraction coefficient ng of the tempered glass 200 in advance by another method (measurement with a refraction measuring device, etc.). preferable.

It is also possible to calibrate the incident margin angle Ψ from the angle χ of the laser image of the image sensor 60. For example, in step S711 of the flowchart shown in FIG. 57, the relationship between the incident margin angle Ψ and the angle χ is derived in the same manner as in FIG. To measure. Then, in step S714, the incident margin angle Ψ is derived from the relationship derived in step S711 using the angle χ measured in step S712. By applying the incident margin angle Ψ derived in step S714 to Equation 8, an accurate stress can be obtained.

Further, when the value of the refractive index ng of the tempered glass 200 is known in advance, it is also effective to design the optimum light supply member 40 in consideration of the value of the refractive index ng of the tempered glass 200.

The incident margin angle Ψ and the incident surface angle ω in the tempered glass 200 can be known by calculation, but when the difference between the refractive index ng of the tempered glass 200 and the refractive index np of the light supply member 40 becomes large, the incident surface angle Ψ There is a lot of deviation from 45 °. As a result, when the depth of focus of the lens of the image sensor 60 is exceeded, the focus shifts, the spatial decomposition decreases, and the correct stress distribution cannot be measured.

For example, when the refractive index of the tempered glass 200 is ng = 1.49, the incident margin angle Ψ of the laser beam in the tempered glass 200 is 10.3 °, and the incident surface angle ω is 35 °. In this case, the incident margin angle Ψ can be corrected by calculation, but the incident surface angle ω deviates from 45 ° by 10 °, and the measurement accuracy cannot be maintained only by the correction by calculation.

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

For example, when the distance of the laser trajectory is 300 μm, when the incident surface angle ω deviates by 10 °, the difference in the distance from the image pickup element 60 to the laser beam in the tempered glass 200 becomes 52 μm, and an image is formed on the image pickup element 60. The depth of focus of the lens is exceeded, and the focus is not uniform over the entire distance of the laser trajectory imaged by the image sensor 60, which deteriorates the measurement accuracy.

Therefore, 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 in which the surface through which the laser beam passes and the observation surface do not change is obtained.

For example, when the refraction of the tempered glass 200 is ng = 1.49, the Y rotation angle θL = 15 ° and the Z rotation angle φL = 15 ° of the laser beam are the same, and the rotation angle β = of the incident end face of the light supply member 40. If it is formed at 15 ° and a Z rotation angle α = 24.5 °, the laser beam can have an incident margin angle of 14.4 ° and an incident surface angle of 44.8 ° in the tempered glass 200, which are almost as designed. .. Therefore, the measurement accuracy is not deteriorated.

The light supply member 40 having this specification is manufactured, the laser light source 10 is left as it is, and only the light supply member 40 is replaced. The stress distribution can be measured accurately. Further, when the surface of the tempered glass 200 and the surface on which the laser light is incident on the light supply member 40 is slightly shifted (about 0.5 to 1 °) in order to eliminate the return light to the laser light source 10, it can be corrected by the formula 8. be.

<Fifth Embodiment>
In the fifth embodiment, an example of an evaluation device having a function of measuring the glass thickness is shown. In the fifth embodiment, the description of the same component as that of the above-described embodiment may be omitted.

In thin plate-shaped tempered glass, compressive stress is formed on the surface for strengthening. Then, as a whole, tensile stress is generated inside in order to balance the stress.

FIG. 59 is a diagram illustrating the stress distribution in the depth direction of the tempered glass. With respect to the compressive stress formed on the surface, tensile stress is generated in the central portion, and in principle, the stress becomes 0 as a whole. That is, the integrated value (stress energy) of the stress distribution becomes 0 from the front surface to the back surface in the depth direction.

In other words, the integral value of the compressive stress on the surface (compressive energy) and the integral value of the tensile stress at the center (tensile energy) are equal. Further, in the chemical strengthening step, since the chemical strengthening of both sides of the glass is usually 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 is also 0.

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

The evaluation device 1 has a drawback that when the laser beam is diffusely reflected on the outermost surface of the tempered glass and the 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 cannot be measured correctly.

Therefore, the phase value of the center point of the tempered glass is used and used for the phase value of the change in the scattered light luminance on the outermost surface or for the correction thereof. Thereby, for example, the stress values on and near the outermost surface of the tempered glass and the stress distribution can be accurately measured. When 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 and used as the phase value of the center of the tempered glass.

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

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

The glass thickness measuring device 120 has a laser light source (not shown), a light receiving unit, and a calculation unit. The laser light Lg emitted from the laser light source of the glass thickness measuring device 120 is reflected by the front surface 210 and the back surface 220 of the tempered glass 200, and is received by the light receiving portion 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 can be measured by the evaluation device 1 in the depth direction from the surface of the tempered glass 200 from the change in the brightness of the scattered light in the tempered glass 200 due to the laser light from the laser light source 10. At the same time, the evaluation device 3 can measure the thickness of the tempered glass 200 by the glass thickness measuring device 120.

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

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

<Modification example for determining the phase value>
The following modifications are possible for determining the phase value of the change in the brightness of scattered light on the outermost surface.

As described above, the evaluation device 1 has a drawback that when the laser beam is diffusely reflected on the outermost surface of the tempered glass 200 and the 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 cannot be measured correctly. .. In order to make up for the shortcoming, the following method may be further used.

First, two sets of a laser light source 10, a polarizing member 20, and a polarization phase difference variable member 30 are prepared, and laser beams L and L'are incident from two different angles θ _s1 and angles _θ's1 . May be good. At that time, the scattered light from the laser beam L and the scattered light from the laser beam L'are measured separately. Of the two sets of laser light, the one using the laser light incident from a smaller angle has a smaller error in the phase value of the outermost surface of the tempered glass 200 due to the influence of diffused reflection on the surface of the tempered glass 200, while the error is smaller. It may not be possible to measure deep inside the tempered glass 200. Therefore, the phase value of the outermost surface of the tempered glass 200 is determined by the measurement using the laser beam incident from a smaller angle, and the result is the phase value of the outermost surface of the measurement using the laser beam incident from a larger angle. By doing so, the measurement accuracy may be improved and the deep part of the tempered glass 200 may be measured.

Secondly, in order to suppress diffuse reflection of the laser light on the outermost surface of the tempered glass 200, there may be a step of cleaning the surface of the tempered glass 200 with a cleaning system before the step S601. The cleaning system may be cleaning with a wet or dry washer, wiping, or the like.

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

That is, since the sum of DOL_zero (front surface) and DOL_zero (back surface) is the thickness of the tempered glass 200, the midpoint thereof is the midpoint of the glass. Since the integrated 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 is 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. Further, the position of the origin of the phase may be extrapolated and calculated so that the outermost surface of the tempered glass has the phase of the midpoint of the glass.

The DOL_zero (back surface) is the length measured from the front surface 210 side of the tempered glass 200 at the point where the stress value on the back surface 220 side becomes zero. Further, in order to measure DOL_zero (back surface) with high accuracy, the liquid 90 may be installed on the back surface 220 side. By doing so, diffused reflection on the front surface on the back surface 220 side is suppressed. Further, a light-shielding function such as a light-shielding plate may be provided between the glass and the camera so that light from the back surface side does not enter.

Fourth, in the fifth embodiment, when the means for calculating the value of DOL_zero is further provided, DOL_zero (front surface) on the glass front surface 210 side and DOL_zero (back surface) on the back surface 220 side are used. The phase of the outermost surface on the glass surface 210 side may be estimated as follows. That is, since the sum of DOL_zero (front surface) and DOL_zero (back surface) is the glass thickness, the stress distribution as a whole is determined by determining the position of the outermost surface so that this sum matches the value measured by the glass thickness measuring device. Is required 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 step (S405), there may be a step of evaluating whether or not the calculated origin position of the phase change is appropriate. At that time, a method may be used in which the origin position of the phase change calculated in S405 is displayed at the corresponding position of the image obtained in the imaging step (S403) using a display, and the measurer visually evaluates the position. By doing so, when the origin position of the phase change is greatly deviated due to noise at the time of measurement or light scattering due to dust, bubbles, disturbance light, etc., it is possible to easily determine the remeasurement. If the cause is ambient light, 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 are made to the above-mentioned embodiment without departing from the scope of the claims. Can be added.

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 not to have a light source. As the 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 Polarizing member 25, 40, 41 Light supply member 30, 30A Polarized phase difference variable member 35, 42 Light extraction member 40a Incident surface of light supply member 40b Emission surface of light supply member 40x, 43x Depression 40y, 43y Groove 43 Single concave lens 43e Outer edge 44 Support 45, 50, 50A Light conversion member 60, 60A, 65 Imaging element 70 , 75 Computation unit 80, 80A, 81, 82 Light wavelength selection member 90 Liquid 100 Land member 120 Glass thickness measuring device 200 Reinforced glass 210 Reinforced glass surface 215 Observation surface 220 Reinforced glass back surface 250 Laser light incident surface 301 Digital data Storage circuit 302 Clock signal generation circuit 303 DA converter 304 Voltage amplification circuit 310 Polarized phase difference generating material 311 313 Fixing jig 312 Piezo element 701 Brightness change measuring means 702 Phase change calculating means 703 Stress distribution calculating means 704 Physical quantity measuring means 751 Position Measuring means 752 Stress distribution calculation means 753 Synthesis means

Claims (55)

A polarization phase difference variable member that changes the polarization phase difference of the laser light by one or more wavelengths with respect to the wavelength of the laser light.
An image pickup device that acquires a plurality of images by capturing the scattered light emitted by the laser beam having a variable polarization phase difference incident on the tempered glass multiple times at a predetermined time interval.
The periodic brightness change of the scattered light is measured using the plurality of images, the phase change of the brightness change is calculated, and the stress distribution in the depth direction from the surface of the tempered glass is calculated based on the phase change. An evaluation device for tempered glass, which comprises a calculation unit for measuring a physical quantity related to the strength of the tempered glass using the plurality of images. The tempered glass evaluation device according to claim 1, wherein the calculation unit measures the brightness of the scattered light as the physical quantity. The plurality of images have a speckle pattern and
The tempered glass evaluation device according to claim 1, wherein the calculation unit measures the dispersion value of the brightness of the speckle pattern as the physical quantity. The tempered glass evaluation device according to claim 1, wherein the calculation unit measures the refractive index of the tempered glass as the physical quantity. The first light wavelength selection member having a relatively high wavelength transmission rate of the laser light and the second light wavelength selection member having a relatively low wavelength transmission rate of the laser light are described by the laser light. Switchably inserted on the optical path incident on the image pickup element,
The calculation unit has, as the physical quantity, the first luminance of the scattered light when the first light wavelength selection member is inserted on the optical path, and the second light wavelength selection member on the optical path. Any of claims 1 to 4, wherein the second luminance of the scattered light when inserted is measured, and the ratio of the first luminance to the second luminance is calculated. The tempered glass evaluation device according to item 1. The first light wavelength selection member that transmits the laser light of the first wavelength band and the second light wavelength selection member that transmits the light of the second wavelength band are the laser light of the first wavelength band. The first light wavelength selection member is selected when incident, and the second light wavelength selection member is selected when laser light in the second wavelength band is incident. The laser beam is switchably inserted into the optical path incident on the image pickup element, and is inserted.
The calculation unit has, as the physical quantity, the first brightness of the scattered light when the laser light in the first wavelength band is incident and the first light wavelength selection member is inserted into the optical path, and the said. The present invention is characterized in that the second brightness of the scattered light when a laser beam of a second wavelength band is incident and the second light wavelength selection member is inserted into the optical path is measured. The tempered glass evaluation device according to any one of 1 to 4. The tempered glass evaluation device according to any one of claims 1 to 6, wherein the calculation unit measures the physical quantity in a plurality of regions in the depth direction from the surface of the tempered glass. The tempered glass evaluation device according to any one of claims 1 to 7, wherein the variable polarization phase difference member is a liquid crystal element. The invention is characterized in that the polarization phase difference variable member is a transparent member having a value obtained by multiplying a photoelastic constant and Young's modulus by 0.1 or more and generating the polarization phase difference by pressurization. The tempered glass evaluation device according to any one of 1 to 7. The tempered glass evaluation device according to claim 9, wherein the transparent member is quartz glass or polycarbonate. The position of the minimum beam diameter of the laser beam is in the ion exchange layer of the tempered glass.
The tempered glass evaluation device according to any one of claims 1 to 10, wherein the minimum beam diameter is 20 μm or less. The evaluation of the tempered glass according to any one of claims 1 to 11, wherein the incident surface of the laser beam incident on the tempered glass is 45 ± 5 ° with respect to the surface of the tempered glass. Device. It has a light supply member that allows the laser beam with a variable polarization phase difference to be obliquely incident on the glass surface in the tempered glass that is the object to be measured.
The feature is that the angle of the surface of the light supply member to which the laser light is incident is set so that the incident surface of the laser light incident on the tempered glass is 45 ± 5 ° with respect to the surface of the tempered glass. The tempered glass evaluation device according to claim 12. It has a light supply member that allows the laser beam with a variable polarization phase difference to be obliquely incident on the glass surface in the tempered glass that is the object to be measured.
A liquid having a refractive index difference of 0.03 or less from the refractive index of the tempered glass is provided between the light supply member and the tempered glass.
The tempered glass evaluation device according to any one of claims 1 to 13, wherein the thickness of the liquid is 10 μm or more and 500 μm or less. A recess 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.
The tempered glass evaluation device according to claim 14, wherein the recess is filled with the liquid. 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 beam incident on the tempered glass via the light supply member.
A recess having a depth of 10 μm or more and 500 μm or less is formed on the side of the protrusion in contact with the tempered glass.
The tempered glass evaluation device according to claim 14, wherein the recess is filled with the liquid. The tempered glass evaluation device according to claim 16, wherein the protrusion is interchangeably held on the surface of the light supply member. The tempered glass evaluation device according to claim 16 or 17, wherein a flat outer edge portion is formed around the recess, and the flat outer edge portion serves as a surface in contact with the tempered glass. The tempered glass evaluation device according to any one of claims 15 to 18, wherein the recess is composed of a surface having a curved portion. The tempered glass evaluation device according to any one of claims 15 to 19, wherein a groove for discharging the liquid is formed around the recess. When the refractive index of the light supply member and the refractive index of the tempered glass are different,
Obtain the refractive index of the tempered glass
When the laser light is incident on the tempered glass from the relationship between the locus 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 image pickup element. Derived the incident margin of
The tempered glass evaluation apparatus according to any one of claims 15 to 20, wherein the stress distribution in the depth direction from the surface of the tempered glass is corrected based on the value of the incident margin. .. The tempered glass evaluation device according to claim 21, wherein the refractive index of the tempered glass is derived based on an image of the laser beam acquired by the image pickup element. When the thickness of the tempered glass is known, the amount of phase change on the outermost surface of the tempered glass is estimated based on the calculated stress distribution and the thickness of the tempered glass so that the stress can be balanced, and the surface stress value. The tempered glass evaluation device according to any one of claims 1 to 22, wherein the tempered glass is corrected. A means for measuring the thickness of the tempered glass is provided.
Any of claims 1 to 23, wherein the stress distribution and the thickness of the tempered glass are measured, and the amount of phase change on the outermost surface of the tempered glass is estimated based on the measured thickness of the tempered glass. The tempered glass evaluation device described in item 1. The tempered glass according to any one of claims 1 to 24, wherein the laser light in the tempered glass satisfies the condition of total internal reflection on the emission side of the laser light of the tempered glass. Evaluation device. A second light supply member for incident light from the second light source into the surface layer having the compressive stress layer of the tempered glass, and
A light extraction member that emits light propagating in the surface layer to the outside of the tempered glass.
Two types of light components that vibrate parallel and perpendicular to the interface between the tempered glass and the light extraction member, which are contained in the light emitted through the light extraction member, each have two or more emission lines. An optical conversion member that converts into two types of emission line trains,
A second image sensor that captures the above two types of emission line trains, and
It has a position measuring means for measuring the positions of two or more emission lines of each of the two types of emission lines from the image obtained by the second image pickup element.
The calculation unit is based on the stress distribution in the first region from the surface of the tempered glass corresponding to the two types of optical components calculated based on the measurement results of the position measuring means to the depth direction, and the phase change. The tempered glass evaluation device according to any one of claims 1 to 25, which comprises synthesizing a stress distribution other than the first region calculated in the above-mentioned method. A polarization phase difference variable step of varying the polarization phase difference of the laser light by one or more wavelengths with respect to the wavelength of the laser light.
An imaging step of acquiring a plurality of images by imaging the scattered light generated by the laser beam having a variable polarization phase difference incident on the tempered glass a plurality of times at a predetermined time interval.
The periodic brightness change of the scattered light is measured using the plurality of images, the phase change of the brightness change is calculated, and the first stress in the depth direction from the surface of the tempered glass is calculated based on the phase change. A method for evaluating tempered glass, which comprises a calculation step of calculating a distribution and measuring a physical quantity related to the strength of the tempered glass using the plurality of images. The method for evaluating tempered glass according to claim 27, wherein in the calculation step, the brightness of the scattered light is measured as the physical quantity. The plurality of images have a speckle pattern and
The method for evaluating tempered glass according to claim 27, wherein in the calculation step, the dispersion value of the brightness of the speckle pattern is measured as the physical quantity. The method for evaluating tempered glass according to claim 27, wherein in the calculation step, the refractive index of the tempered glass is measured as the physical quantity. The first light wavelength selection member having a relatively high transmittance of the wavelength of the laser light and the second light wavelength selection member having a relatively low transmittance of the wavelength of the laser light are described by the laser light. It is switchably inserted on the optical path incident on the image pickup element used in the image pickup process.
In the calculation step, as the physical quantity, the first luminance of the scattered light when the first light wavelength selection member is inserted into the optical path and the second light wavelength selection member are placed on the optical path. Any of claims 27 to 30, wherein the second luminance of the scattered light when inserted is measured, and the ratio of the first luminance to the second luminance is calculated. The evaluation method for tempered glass according to item 1. The first light wavelength selection member that transmits the laser light of the first wavelength band and the second light wavelength selection member that transmits the light of the second wavelength band are the laser light of the first wavelength band. The first light wavelength selection member is selected when incident, and the second light wavelength selection member is selected when laser light in the second wavelength band is incident. The laser beam is switchably inserted into the optical path incident on the image pickup element used in the image pickup process.
In the calculation step, as the physical quantity, the first brightness of the scattered light when the laser light in the first wavelength band is incident and the first light wavelength selection member is inserted into the optical path, and the said. The present invention is characterized in that the second brightness of the scattered light when a laser beam of a second wavelength band is incident and the second light wavelength selection member is inserted into the optical path is measured. The method for evaluating a tempered glass according to any one of 27 to 30. The method for evaluating tempered glass according to any one of claims 27 to 32, 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. The method for evaluating tempered glass according to any one of claims 27 to 33, wherein the polarization phase difference variable step changes the polarization phase difference by a liquid crystal element. The refractive index distribution of each is calculated based on the positions of the emission lines of P-polarization and S-polarization, and the second stress distribution is calculated based on the difference in refractive index distribution between the P-polarization and S-polarization and the photoelastic constant of the tempered glass. The method for evaluating a tempered glass according to any one of claims 27 to 34, which comprises a required step. The first stress distribution and the second stress distribution obtained by the tempered glass evaluation method according to claim 35 for at least one tempered glass among a plurality of tempered glasses made in the same manufacturing process. To obtain a stress distribution, and for the remaining tempered glass, measure only one of the first stress distribution and the second stress distribution to obtain a stress distribution. Evaluation methods. Scattered light emitted by a polarization phase difference variable step in which the polarization phase difference of the laser light is changed by one or more wavelengths with respect to the wavelength of the laser light, and when the laser light having the variable polarization phase difference is incident on the tempered glass. Is imaged a plurality of times at predetermined time intervals to acquire a plurality of images, and the periodic brightness change of the scattered light is measured using the plurality of images, and the phase change of the brightness change is calculated. Then, the first stress distribution in the depth direction from the surface of the tempered glass is calculated based on the phase change, and the calculation step of measuring the physical quantity related to the strength of the tempered glass using the plurality of images. A method for manufacturing tempered glass, which comprises obtaining a characteristic value from a stress value obtained by an evaluation method for tempered glass having a tempered glass, confirming whether the characteristic value is within the control value, and then making a shipping decision. The method for manufacturing tempered glass according to claim 37, wherein the polarization phase difference variable step changes the polarization phase difference by a liquid crystal element. The refractive index distribution of each is calculated based on the positions of the emission lines of P-polarization and S-polarization, and the second stress distribution is calculated based on the difference in refractive index distribution between the P-polarization and S-polarization and the photoelastic constant of the tempered glass. The method for producing tempered glass according to claim 37 or 38, which comprises the required step. The stress distribution is obtained by synthesizing the first stress distribution and the second stress distribution obtained by the evaluation method for at least one tempered glass among a plurality of tempered glasses made in the same manufacturing process. The method for producing tempered glass according to claim 39, wherein the stress distribution is obtained by measuring only one of the first stress distribution and the second stress distribution with respect to the remaining tempered glass. .. It includes two or more tempering steps to prepare tempered glass that is tempered with lithium-containing glass and determine the shipment of the tempered glass.
The method for producing tempered glass according to claim 37 or 38, wherein each tempering step makes a shipping determination based on the first stress distribution obtained by the evaluation method. In the final strengthening step, the evaluation method calculates the respective refractive index distributions based on the positions of the emission lines of P-polarized light and S-polarized glass, and the difference in refractive index distribution between the P-polarized light and the S-polarized glass and the light of the tempered glass. The tempered glass according to claim 41, further comprising a step of obtaining a second stress distribution based on an elastic constant, and making a shipping decision based on the second stress distribution obtained by the evaluation method. Manufacturing method. In the tempering step other than the final step, the shipping determination 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. 42. The method for producing tempered glass according to claim 42. The method for producing tempered glass according to claim 42 or 43, wherein in the final tempering step, the shipping determination is performed by function-approximing the second stress distribution. The method for producing tempered glass according to claim 44, wherein the function approximation is performed by the following formula (2).

However, σf (x) is the second stress distribution, a is the slope, and CS2 is the stress value on the outermost surface. The method for producing tempered glass according to claim 44, wherein the function approximation is performed by the following formula (3).

However, σf (x) is the second stress distribution, a is the slope, CS2 is the stress value on the outermost surface, and erfc is an error function. In the tempering step except the final step, the second stress distribution obtained in the tempering step, the plate thickness t of the tempered glass, and the first stress distribution of the tempered glass under the same conditions measured in advance are used. , The first stress distribution and the second stress distribution are combined, the stress value (CT) in the deepest part of the glass is found from the stress distribution after synthesis, and the characteristic value is derived, and the characteristic value falls within the allowable range. The method for producing tempered glass according to any one of claims 42 to 46, wherein the shipping determination is made depending on whether or not the product is shipped. In the tempering step except the final step, the second stress distribution obtained in the tempering step, the plate thickness t of the tempered glass, and the first stress distribution of the tempered glass under the same conditions measured in advance are used. , The first stress distribution and the second stress distribution are combined, the stress value (CT) in the deepest part of the glass where the integrated value of the combined stress distribution becomes zero is found, and the characteristic value is derived, and the characteristic value is derived. The method for producing tempered glass according to any one of claims 42 to 47, wherein the shipping determination is made depending on whether or not is within the permissible range. In the tempering step except the final step, the second stress distribution obtained in the tempering step, the plate thickness t of the tempered glass, and the first stress distribution of the tempered glass under the same conditions measured in advance are used. , The first stress distribution and the second stress distribution are combined, the combined stress distribution is approximated by the following equation (5), and the integrated value of σ (x) (x = 0 to t / 2). 42 to 47, wherein the stress value (CT) in the deepest part of the glass where becomes zero is found, the characteristic value is derived, and the shipping determination is made based on whether or not the characteristic value is within the allowable range. The method for producing tempered glass according to any one of the above.

However, 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 the parameters derived based on the first stress distribution. be. The method for producing tempered glass according to claim 49, wherein CS ₀ and c are derived based on a first stress distribution of tempered glass under the same conditions measured in advance. The CS ₀ and c are derived based on the CS 0'and c'derived from the first stress distribution obtained in the strengthening step one time before the final round, and the following equations (6) and (7). The method for producing tempered glass according to claim 49.

However, A1 and A2 are proportional constants. The method for producing tempered glass according to claim 51, wherein A1 and A2 are derived based on a first stress distribution of tempered glass under the same conditions measured in advance. A tempered glass produced by the method for producing tempered glass according to any one of claims 37 to 52. The tempered glass according to claim 53, wherein the glass containing 2 wt% or more of lithium is chemically strengthened. The tempered glass according to claim 53, which is manufactured by being chemically fortified after being air-cooled.

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