Apparatus for evaluating tempered glass, method for producing tempered glass, and tempered glass
阅读说明：本技术 强化玻璃的评价装置、强化玻璃的评价方法、强化玻璃的制造方法及强化玻璃 (Apparatus for evaluating tempered glass, method for producing tempered glass, and tempered glass ) 是由 今北健二 大神聪司 折原秀治 折原芳男 于 2019-02-25 设计创作，主要内容包括：本强化玻璃的评价装置具有：偏振光相位差可变构件,使激光的偏振光相位差相对于所述激光的波长变化一个波长以上；拍摄元件,以规定的时间间隔多次拍摄散射光并取得多个图像,所述散射光是通过将所述偏振光相位差变化了的激光向强化玻璃入射而发出的散射光；及运算部,使用所述多个图像,测定所述散射光的周期性的亮度变化,算出所述亮度变化的相位变化,基于所述相位变化来算出从所述强化玻璃的表面起的深度方向上的应力分布,并使用所述多个图像来测定与所述强化玻璃的强度有关的物理量。(The evaluation device for tempered glass comprises: a polarization phase difference varying member that varies a polarization phase difference of the laser light by one wavelength or more with respect to a wavelength of the laser light; an imaging element that captures a plurality of images at predetermined time intervals, and acquires a plurality of images, the scattered light being scattered light emitted by the laser light of which the polarization phase difference has been changed being incident on a tempered glass; and a calculation unit that measures a periodic luminance change of the scattered light using the plurality of images, calculates a phase change of the luminance change, calculates a stress distribution in a depth direction from a surface of the tempered glass based on the phase change, and measures a physical quantity related to a strength of the tempered glass using the plurality of images.)
1. An apparatus for evaluating a tempered glass, comprising:
a polarization phase difference varying member that varies a polarization phase difference of the laser light by one wavelength or more with respect to a wavelength of the laser light;
an imaging element that captures a plurality of images at predetermined time intervals, and acquires a plurality of images, the scattered light being scattered light emitted by the laser light of which the polarization phase difference has been changed being incident on a tempered glass; and
and a calculation unit that measures a periodic luminance change of the scattered light using the plurality of images, calculates a phase change of the luminance change, calculates a stress distribution in a depth direction from a surface of the tempered glass based on the phase change, and measures a physical quantity related to a strength of the tempered glass using the plurality of images.
2. The strengthened glass evaluation apparatus according to claim 1,
the calculation unit measures the brightness of the scattered light as the physical quantity.
3. The strengthened glass evaluation apparatus according to claim 1,
the plurality of images are provided with a speckle pattern,
the calculation unit measures a variance value of the luminance of the speckle pattern as the physical quantity.
4. The strengthened glass evaluation apparatus according to claim 1,
the calculation unit measures the refractive index of the tempered glass as the physical quantity.
5. The apparatus for evaluating a tempered glass according to any one of claims 1 to 4,
a first optical wavelength selection member having a relatively high transmittance of the wavelength of the laser light and a second optical wavelength selection member having a relatively low transmittance of the wavelength of the laser light are switchably inserted on an optical path on which the laser light enters the imaging element,
the calculation unit measures, as the physical quantity, a first luminance of the scattered light when the first light wavelength selection member is inserted on the optical path and a second luminance of the scattered light when the second light wavelength selection member is inserted on the optical path, and calculates a ratio of the first luminance to the second luminance.
6. The apparatus for evaluating a tempered glass according to any one of claims 1 to 4,
a first optical wavelength selection member that transmits laser light in a first wavelength band and a second optical wavelength selection member that transmits light in a second wavelength band are switchably inserted on an optical path on which the laser light enters the imaging element, in such a manner that the first optical wavelength selection member is selected when the laser light in the first wavelength band enters and the second optical wavelength selection member is selected when the laser light in the second wavelength band enters,
the calculation unit measures, as the physical quantity, a first luminance of the scattered light when the laser light in the first wavelength band is incident and the first light wavelength selection member is inserted on the optical path, and a second luminance of the scattered light when the laser light in the second wavelength band is incident and the second light wavelength selection member is inserted on the optical path.
7. The apparatus for evaluating a tempered glass according to any one of claims 1 to 6, wherein the apparatus further comprises a temperature sensor for detecting a temperature of the tempered glass,
the computing unit measures the physical quantity at a plurality of regions in a depth direction from a surface of the tempered glass.
8. The apparatus for evaluating a tempered glass according to any one of claims 1 to 7,
the polarized light phase difference variable member is a liquid crystal element.
9. The apparatus for evaluating a tempered glass according to any one of claims 1 to 7,
the polarization phase difference variable member is a transparent member having a value obtained by multiplying a photoelastic constant by a Young's modulus of 0.1 or more and generating the polarization phase difference by applying pressure.
10. The strengthened glass evaluation apparatus according to claim 9,
the transparent member is quartz glass or polycarbonate.
11. The apparatus for evaluating a tempered glass according to any one of claims 1 to 10,
the location of the minimum beam diameter of the laser is within the ion exchange layer of the strengthened glass,
the minimum beam diameter is 20 μm or less.
12. The apparatus for evaluating a tempered glass according to any one of claims 1 to 11,
the incidence plane of the laser light incident on the tempered glass is 45 ± 5 ° with respect to the surface of the tempered glass.
13. The strengthened glass evaluation apparatus according to claim 12,
the evaluation device for tempered glass has a light supply means for making the laser light with the changed polarization phase difference enter the tempered glass as a measurement object in an inclined manner with respect to the glass surface,
the angle of the surface of the light supply member on which the laser light is incident is set so that the angle of the surface of the strengthened glass on which the laser light is incident is 45 ± 5 ° with respect to the surface of the strengthened glass.
14. The apparatus for evaluating a tempered glass according to any one of claims 1 to 13, wherein the apparatus further comprises a temperature sensor for detecting a temperature of the tempered glass,
the evaluation device for tempered glass has a light supply means for making the laser light with the changed polarization phase difference enter the tempered glass as a measurement object in an inclined manner with respect to the glass surface,
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 supplying member and the tempered glass,
the thickness of the liquid is 10 [ mu ] m or more and 500 [ mu ] m or less.
15. The strengthened glass evaluation apparatus according to claim 14,
a recess having a depth of 10 to 500 [ mu ] m is formed on a surface of the light supplying member in contact with the tempered glass,
the liquid is filled in the recess.
16. The strengthened glass evaluation apparatus according to claim 14,
a protrusion portion that comes into contact with the tempered glass is provided on the surface of the light supplying member,
the protrusion is a part of an optical path of the laser light entering the tempered glass through the light supplying member,
a recess having a depth of 10 [ mu ] m or more and 500 [ mu ] m or less is formed on the side of the protrusion in contact with the tempered glass,
the liquid is filled in the recess.
17. The strengthened glass evaluation apparatus according to claim 16,
the projection is replaceably held on the surface of the light supply member.
18. The strengthened glass evaluation apparatus according to claim 16 or 17,
a flat outer edge portion is formed around the recess, and the flat outer edge portion serves as a surface that contacts the tempered glass.
19. The apparatus for evaluating a tempered glass according to any one of claims 15 to 18,
the recess is formed by a surface having a curved portion.
20. The apparatus for evaluating a tempered glass according to any one of claims 15 to 19, wherein the apparatus further comprises a temperature sensor for detecting a temperature of the tempered glass,
grooves for discharging the liquid are formed around the recesses.
21. The apparatus for evaluating a tempered glass according to any one of claims 15 to 20, wherein the apparatus further comprises a temperature sensor for detecting a temperature of the tempered glass,
in the case where the refractive index of the light supplying member is different from the refractive index of the tempered glass,
the refractive index of the tempered glass is obtained,
deriving a complementary angle of incidence when the laser light enters the tempered glass from a relationship between a trajectory of the laser light in the tempered glass obtained based on a refractive index of the tempered glass and an image of the laser light acquired by the imaging element,
correcting a stress distribution in a depth direction from a surface of the strengthened glass based on the value of the complementary angle of incidence.
22. The strengthened glass evaluation apparatus according to claim 21,
the refractive index of the tempered glass is derived based on the image of the laser light acquired by the imaging element.
23. The apparatus for evaluating a tempered glass according to any one of claims 1 to 22, wherein the apparatus further comprises a temperature sensor for detecting a temperature of the tempered glass,
when the thickness of the tempered glass is known, a phase change amount of the outermost surface of the tempered glass, which is to be in stress balance, is estimated based on the calculated stress distribution and the thickness of the tempered glass, and a surface stress value is corrected.
24. The apparatus for evaluating a tempered glass according to any one of claims 1 to 23, wherein the apparatus further comprises a temperature sensor for detecting a temperature of the tempered glass,
the device for evaluating tempered glass comprises means for measuring the thickness of the tempered glass,
the stress distribution and the thickness of the tempered glass are measured, and the amount of phase change of the outermost surface of the tempered glass is estimated based on the measured thickness of the tempered glass.
25. The apparatus for evaluating a tempered glass according to any one of claims 1 to 24, wherein the apparatus further comprises a temperature sensor for detecting a temperature of the tempered glass,
on the exit side of the laser light of the strengthened glass, the laser light in the strengthened glass satisfies the condition of total reflection.
26. The apparatus for evaluating a tempered glass according to any one of claims 1 to 25, wherein the apparatus comprises:
a second light supply member that causes light from a second light source to enter the surface layer of the tempered glass having the compressive stress layer;
a light extraction member that emits light propagating in the surface layer to the outside of the tempered glass;
a light conversion member that converts two light components contained in the light emitted through the light extraction member and vibrating parallel and perpendicular to an interface between the tempered glass and the light extraction member into two bright line rows each having two or more bright lines;
a second photographing element photographing the two bright line columns; and
a position measuring unit that measures positions of two or more bright lines in each of the two bright line arrays from an image obtained by the second imaging element,
the calculation unit combines a stress distribution of a first region in a depth direction from the surface of the tempered glass, which corresponds to the two types of optical components calculated based on the measurement result of the position measurement unit, with a stress distribution other than the first region calculated based on the phase change.
27. A method for evaluating a tempered glass, comprising:
a polarization phase difference varying step of varying a polarization phase difference of the laser light by one wavelength or more with respect to a wavelength of the laser light;
an imaging step of imaging a plurality of times at predetermined time intervals, and acquiring a plurality of images, the scattered light being emitted by causing the laser light whose polarization phase difference has been changed to enter the tempered glass; and
and a calculation step of measuring a periodic change in luminance of the scattered light using the plurality of images, calculating a phase change of the luminance change, calculating a first stress distribution in a depth direction from a surface of the tempered glass based on the phase change, and measuring a physical quantity related to a strength of the tempered glass using the plurality of images.
28. The method for evaluating a strengthened glass according to claim 27, wherein the glass is a glass having a glass transition temperature,
in the calculating step, the brightness of the scattered light is measured as the physical quantity.
29. The method for evaluating a strengthened glass according to claim 27, wherein the glass is a glass having a glass transition temperature,
the plurality of images are provided with a speckle pattern,
in the calculating step, a variance value of the luminance of the speckle pattern is measured as the physical quantity.
30. The method for evaluating a strengthened glass according to claim 27, wherein the glass is a glass having a glass transition temperature,
in the calculation step, the refractive index of the tempered glass is measured as the physical quantity.
31. The method for evaluating a strengthened glass according to any one of claims 27 to 30,
a first optical wavelength selection member having a relatively high transmittance of the wavelength of the laser beam and a second optical wavelength selection member having a relatively low transmittance of the wavelength of the laser beam are switchably inserted into an optical path on which the laser beam enters an imaging element used in the imaging step,
in the calculation step, a first luminance of the scattered light when the first light wavelength selection member is inserted on the optical path and a second luminance of the scattered light when the second light wavelength selection member is inserted on the optical path are measured as the physical quantities, and a ratio of the first luminance to the second luminance is calculated.
32. The method for evaluating a strengthened glass according to any one of claims 27 to 30,
a first optical wavelength selection member that transmits laser light in a first wavelength band and a second optical wavelength selection member that transmits light in a second wavelength band are switchably inserted on an optical path on which the laser light enters an imaging element used in the imaging step, such that the first optical wavelength selection member is selected when the laser light in the first wavelength band enters and the second optical wavelength selection member is selected when the laser light in the second wavelength band enters,
in the calculation step, a first luminance of the scattered light when the laser light in the first wavelength band is incident and the first light wavelength selection member is inserted on the optical path and a second luminance of the scattered light when the laser light in the second wavelength band is incident and the second light wavelength selection member is inserted on the optical path are measured as the physical quantities.
33. The method for evaluating a strengthened glass according to any one of claims 27 to 32,
in the calculation step, the physical quantity is measured at a plurality of regions in a depth direction from a surface of the tempered glass.
34. The method for evaluating a strengthened glass according to any one of claims 27 to 33, wherein the glass is a glass having a glass transition temperature,
in the polarized light phase difference varying step, the polarized light phase difference is varied by a liquid crystal element.
35. The method for evaluating a strengthened glass according to any one of claims 27 to 34, wherein the glass is a glass having a glass transition temperature,
the method for evaluating the tempered glass comprises the following steps: refractive index distributions of the P-polarized light and the S-polarized light are calculated based on the positions of bright lines of the light, and a second stress distribution is obtained based on a difference in refractive index distribution between the P-polarized light and the S-polarized light and a photoelastic constant of the tempered glass.
36. A method for evaluating a tempered glass,
with respect to at least one or more of the plurality of strengthened glasses produced in the same production process, a stress distribution is obtained by combining the first stress distribution and the second stress distribution obtained by the method for evaluating a strengthened glass according to claim 35, and with respect to the remaining strengthened glasses, a stress distribution is obtained by measuring only one of the first stress distribution and the second stress distribution.
37. A method for producing a tempered glass, characterized in that,
the method for evaluating tempered glass includes the steps of obtaining a characteristic value from a stress value obtained by a method for evaluating tempered glass, and determining shipment after confirming whether the characteristic value falls within a control value, the method including: a polarization phase difference varying step of varying a polarization phase difference of the laser light by one wavelength or more with respect to a wavelength of the laser light; an imaging step of imaging a plurality of times at predetermined time intervals, and acquiring a plurality of images, the scattered light being emitted by causing the laser light whose polarization phase difference has been changed to enter the tempered glass; and a calculation step of measuring a periodic change in luminance of the scattered light using the plurality of images, calculating a phase change of the luminance change, calculating a first stress distribution in a depth direction from a surface of the tempered glass based on the phase change, and measuring a physical quantity related to a strength of the tempered glass using the plurality of images.
38. The method for producing a strengthened glass according to claim 37,
in the polarized light phase difference varying step, the polarized light phase difference is varied by a liquid crystal element.
39. The method for producing a strengthened glass according to claim 37 or 38,
the method for producing the tempered glass comprises the following steps: refractive index distributions of the P-polarized light and the S-polarized light are calculated based on the positions of bright lines of the light, and a second stress distribution is obtained based on a difference in refractive index distribution between the P-polarized light and the S-polarized light and a photoelastic constant of the tempered glass.
40. The method for producing a strengthened glass according to claim 39,
at least one or more of the plurality of strengthened glasses produced in the same production process is subjected to a stress distribution obtained by combining the first stress distribution and the second stress distribution obtained by the evaluation method, and the remaining strengthened glasses are subjected to a stress distribution obtained by measuring only one of the first stress distribution and the second stress distribution.
41. The method for producing a strengthened glass according to claim 37 or 38,
comprising two or more strengthening steps of producing a strengthened glass obtained by strengthening a lithium-containing glass and judging shipment of the strengthened glass,
the respective strengthening processes perform the shipment judgment based on the first stress distribution obtained by the evaluation method.
42. The method for producing strengthened glass according to claim 41,
in the final strengthening step, the evaluation method includes the steps of: and calculating refractive index distributions of the P-polarized light and the S-polarized light based on the positions of bright lines of the light, obtaining a second stress distribution based on a difference between the refractive index distributions of the P-polarized light and the S-polarized light and a photoelastic constant of the tempered glass, and determining shipment based on the second stress distribution obtained by the evaluation method.
43. The method for producing a strengthened glass according to claim 42,
in the strengthening process except the final step, the shipment judgment is performed based on the stress value (CT) of the deepest portion of the glass derived from the first stress distribution and the glass depth (DOL _ zero) at which the stress value becomes 0.
44. The method for producing a strengthened glass according to claim 42 or 43,
in the final strengthening process, the shipment determination is performed by approximating the second stress distribution as a function.
45. The method for producing a strengthened glass according to claim 44,
the function approximation is performed using the following equation (2),
[ mathematical formula 2 ]
σf(x)＝a·x+CS2 …(2)
Where σ f (x) is the second stress profile, a is the slope, and CS2 is the most superficial stress value.
46. The method for producing a strengthened glass according to claim 44,
the function approximation is performed using the following equation (3),
[ mathematical formula 3 ]
σf(x)＝CS2·erfc(a·x) …(3)
Where σ f (x) is the second stress distribution, a is the slope, CS2 is the most superficial stress value, and erfc is the error function.
47. The method for producing a strengthened glass according to any one of claims 42 to 46,
in the strengthening step except the final step, the second stress distribution obtained in the strengthening step, the sheet thickness t of the strengthened glass, and the first stress distribution of the strengthened glass under the same condition measured in advance are used, the first stress distribution and the second stress distribution are combined, a stress value (CT) at the deepest portion of the glass is found from the combined stress distribution, a characteristic value is derived, and the shipment judgment is performed according to whether or not the characteristic value is within an allowable range.
48. The method for producing a strengthened glass according to any one of claims 42 to 47, wherein the glass is a glass having a glass transition temperature,
in the strengthening step other than the final step, the second stress distribution obtained in the strengthening step, the sheet thickness t of the strengthened glass, and the first stress distribution of the strengthened glass under the same condition measured in advance are used, the first stress distribution and the second stress distribution are combined, a stress value (CT) in the deepest portion of the glass where the integrated value of the combined stress distribution becomes 0 is found, a characteristic value is derived, and the shipment judgment is performed based on whether or not the characteristic value enters an allowable range.
49. The method for producing a strengthened glass according to any one of claims 42 to 47, wherein the glass is a glass having a glass transition temperature,
in the strengthening step except the final step, the second stress distribution obtained in the strengthening step, the sheet thickness t of the strengthened glass, and the first stress distribution of the strengthened glass under the same condition measured in advance are used, the first stress distribution and the second stress distribution are synthesized, the synthesized stress distribution is approximated by the following formula (5), a stress value (CT) in the deepest part of the glass where the integral value (x) of σ (x) is 0 to t/2) is found to derive a characteristic value, and the shipment judgment is performed depending on whether or not the characteristic value is within an allowable range,
[ math figure 5 ]
Wherein σ (x) is the stress distribution after synthesis, σ f (x) is the second stress distribution, t is the sheet thickness of the tempered glass,CS0and c is a parameter derived based on the first stress distribution.
50. The method for producing strengthened glass according to claim 49,
deriving the CS based on a previously determined first stress distribution of the tempered glass under the same conditions0And c, and c.
51. The method for producing strengthened glass according to claim 49,
deriving the CS based on CS0 'and c' derived from the first stress distribution obtained by the last previous reinforcement process and the following equations (6) and (7)0And c, a step of adding a metal oxide to the alloy,
[ mathematical formula 6 ]
CS0＝A1×CS0′ …(6)
[ mathematical formula 7 ]
c＝A2×c′ …(7)
Wherein, A1 and A2 are proportionality constants.
52. The method for producing strengthened glass according to claim 51, wherein the glass is a glass having a glass transition temperature,
a1 and A2 were derived based on the first stress distribution of the tempered glass under the same conditions measured in advance.
53. A tempered glass produced by the method for producing a tempered glass according to any one of claims 37 to 52.
54. The strengthened glass according to claim 53,
a glass containing 2 wt% or more of lithium is chemically strengthened.
55. The strengthened glass according to claim 53,
the tempered glass is produced by air-cooling tempering and then chemically tempering.
Technical Field
The present invention relates to a device for evaluating a tempered glass, a method for producing a tempered glass, and a tempered glass.
Background
In electronic devices such as mobile phones and smart phones, glass is often used for a display portion and a housing main body. With the recent reduction in thickness and weight of electronic devices, there is a demand for reduction in thickness of glass used for electronic devices. When the thickness of the glass is reduced, the strength is lowered. Therefore, in order to improve the strength of glass, it is common to use so-called chemically strengthened glass having improved strength by forming a surface layer (ion exchange layer) by ion exchange on the glass surface, measure the stress value of the surface by an optical method, confirm whether or not the glass is correctly strengthened, and deliver the glass to the market.
As a technique for measuring the stress of the surface layer of the tempered glass, for example, a technique for nondestructively measuring the compressive stress of the surface layer by utilizing the optical waveguide effect and the photoelastic effect when the refractive index of the surface layer of the tempered glass is higher than the refractive index of the inside (hereinafter, referred to as a nondestructive measurement technique) can be cited. In this nondestructive measurement technique, monochromatic light is made incident on the surface layer of the tempered glass to generate a plurality of modes by the optical waveguide effect, and light determined by the ray trajectory in each mode is extracted and imaged as a bright line corresponding to each mode by a convex lens. Note that the number of bright line presence patterns to be imaged is.
In this nondestructive measurement technique, light extracted from the surface layer is observed as bright lines of two light components, i.e., horizontal and vertical, in the light vibration direction with respect to the emission surface. Further, the refractive index of each light component is calculated from the position of the bright line corresponding to
On the other hand, based on the principle of the nondestructive measurement technique described above, a method has been proposed in which the stress (hereinafter referred to as a surface stress value) of the outermost surface of the glass is obtained by extrapolation from the positions of the bright lines corresponding to the
Further, a method has been proposed in which the tensile stress CT inside the glass is defined based on the surface stress value and the depth of the compressive stress layer measured by the above-described surface waveguide light measurement technique, and the strength of the tempered glass is controlled by the CT value (see, for example, patent document 2). In this method, the tensile stress CT is calculated using "CT ═ CS × DOL)/(t × 1000-2 × DOL) (expression 0). Here, CS is a surface stress value (MPa), DOL is a depth (unit: μm) of the compressive stress layer, and t is a sheet thickness (unit: mm).
Generally, if no external force is applied, the sum of the stresses is 0. Therefore, the tensile stress is generated substantially uniformly so that the value obtained by integrating the stress formed by the chemical strengthening in the depth direction is balanced in the central portion that is not chemically strengthened.
Further, a method has been proposed in which the stress distribution on the glass surface layer side from the glass depth (DOL _ TP) at the position where the stress distribution is bent is measured, and the stress distribution on the glass depth side from DOL _ TP is predicted based on the measurement result (measurement image) of the stress distribution on the glass surface layer side (for example, see patent document 4). However, this method has a problem that measurement reproducibility is poor because the stress distribution on the deep glass layer side of DOL _ TP is not measured.
However, chemically strengthened glass is also diversified due to the improvement in strength and performance, and conventional stress measurement methods cannot be sufficiently evaluated.
For example, there are tempered glass in which a stress distribution is controlled by ion-exchanging lithium-containing glass with two types of ions, i.e., potassium and sodium, and chemically tempered glass in which ion-exchanging is performed with transparent crystallized glass.
In the case of a conventional optical surface stress measuring device for chemically strengthened glass containing lithium glass, although the stress layer in the vicinity of the surface in which lithium is replaced with potassium can be evaluated, the stress layer in the interior in which lithium is replaced with sodium cannot be evaluated, and therefore the stress depth cannot be measured.
Among crystallized glasses, it is necessary to be transparent in order to be used particularly in a display portion, and therefore crystallized glass used here is crystallized glass having crystal grains much smaller than the wavelength of visible light, and is transparent in the visible region. Therefore, the stress of the surface formed by the chemical strengthening step can be measured by a conventional optical surface stress measuring apparatus.
However, the strength of the crystallized glass depends not only on the stress in the vicinity of the surface to be chemically strengthened, but also greatly on the crystal grain size, crystal grain density, crystal grain type, and the like generated by recrystallization, and the influence on the chemical strengthening step after recrystallization is also large. In addition, the crystal generated in the recrystallization step may be changed in the chemical strengthening step.
Therefore, in order to maintain the quality of diversified chemically strengthened glass, it is necessary to measure the distribution of stress managed to the deep part, the crystalline state of crystallized glass, and the like.
Prior art documents
Patent document
Patent document 1: japanese laid-open patent publication No. 53-136886
Patent document 2: japanese patent publication No. 2011-530470
Patent document 3: japanese patent laid-open publication No. 2016-142600
Patent document 4: U.S. patent publication 2016/0356760
Non-patent document
Non-patent document 1: Yogyo-Kyokai-Shi (journal of kiln Association) 87{3}1979
Non-patent document 2: Yogyo-Kyokai-Shi (journal of kiln Association) 80{4}1972
Disclosure of Invention
Problems to be solved by the invention
In recent years, lithium-aluminosilicate glasses have attracted attention as glasses which are easy to ion exchange, have a short time, have a high surface stress value, and can have a deep stress layer in a chemical strengthening step.
The glass was immersed in a high-temperature molten salt of a mixture of sodium nitrate and potassium nitrate to perform chemical strengthening treatment. Since both sodium ions and potassium ions are present in a high concentration in the molten salt, the sodium ions are ion-exchanged with lithium ions in the glass, but the sodium ions are more easily diffused into the glass, and therefore, the lithium ions in the glass are first ion-exchanged with the sodium ions in the molten salt.
Here, when sodium ions are ion-exchanged with lithium ions, the refractive index of the glass decreases, and when potassium ions are ion-exchanged with lithium ions or sodium ions, the refractive index of the glass increases. That is, the potassium ion concentration in the region ion-exchanged near the glass surface is higher than that in the portion not ion-exchanged in the glass, and the sodium ion concentration is higher when the region ion-exchanged is deeper. Therefore, the following features are provided: the refractive index decreases with depth in the vicinity of the outermost surface of the ion-exchanged glass, but increases with depth from a certain depth to a region where the ion-exchange is not performed.
Therefore, in the stress measuring device using the waveguide light on the surface described in the background art, the stress distribution in the deep portion cannot be measured only by the stress value or the stress distribution on the outermost surface, and the depth of the stress layer, the CT value, and the stress distribution as a whole cannot be known. As a result, development for finding appropriate chemical strengthening conditions cannot be achieved, and quality control of production cannot be performed.
In addition, when chemical strengthening is performed after air-cooling strengthening of aluminosilicate glass or soda glass, the stress distribution or the stress value can be measured by the stress measuring device using surface waveguide light described in the background art in the chemically strengthened portion. However, the change in refractive index of a portion that has not been chemically strengthened but has been air-cooled strengthened is small, and cannot be measured by the stress measuring apparatus using waveguide light on the surface described in the background art. As a result, the depth of the stress layer, the CT value, and the overall stress distribution cannot be known. As a result, development for finding appropriate chemical strengthening conditions cannot be achieved, and quality control of production cannot be performed.
On the other hand, the crystallized glass has higher strength than general glass. Therefore, the chemically strengthened crystallized glass can obtain higher strength than the ordinary strengthened glass. However, in the crystallized glass, physical properties such as strength are greatly affected by a crystalline state (particle diameter, crystal grain density, crystal type) and the like. Therefore, in the crystallized glass, it is necessary to measure physical quantities related to the strength of the crystallized glass together with the stress distribution by the chemical strengthening.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an apparatus for evaluating a tempered glass, which can measure a stress distribution of the tempered glass and can measure a physical quantity related to the strength of the tempered glass.
Means for solving the problems
The essential elements of the evaluation device for tempered glass are that the device comprises: a polarization phase difference varying member that varies a polarization phase difference of the laser light by one wavelength or more with respect to a wavelength of the laser light; an imaging element that captures a plurality of images at predetermined time intervals, and acquires a plurality of images, the scattered light being scattered light emitted by the laser light of which the polarization phase difference has been changed being incident on a tempered glass; and a calculation unit that measures a periodic luminance change of the scattered light using the plurality of images, calculates a phase change of the luminance change, calculates a stress distribution in a depth direction from a surface of the tempered glass based on the phase change, and measures a physical quantity related to a strength of the tempered glass using the plurality of images.
Effects of the invention
According to the disclosed technology, it is possible to provide an apparatus for evaluating a tempered glass, which can measure the stress distribution of the tempered glass and can measure a physical quantity related to the strength of the tempered glass.
Drawings
Fig. 1 is a diagram illustrating an evaluation apparatus according to a first embodiment.
Fig. 2 is a view of the evaluation apparatus of the first embodiment as viewed from the direction H of fig. 1.
Fig. 3 is a diagram illustrating a relationship between an applied voltage of the liquid crystal element and a phase difference of polarized light.
Fig. 4 is a diagram illustrating a circuit for generating a drive voltage by which the polarization phase difference of the liquid crystal element changes linearly in time.
Fig. 5 is a diagram illustrating a scattered light image at a certain moment of the laser light L imaged by the imaging element.
Fig. 6 is a graph illustrating temporal changes in scattered light luminance at points B and C of fig. 5.
Fig. 7 is a graph illustrating the phase of the change in scattered light according to the glass depth.
Fig. 8 is a diagram illustrating a stress distribution obtained by
Fig. 9 is a diagram illustrating actual scattered light images at different times t1 and
Fig. 10 is a diagram showing an unfavorable design example of the incident surface of the laser light L in the tempered glass.
Fig. 11 is a diagram showing a preferred design example of the incident surface of the laser light L in the tempered glass.
Fig. 12 is a diagram illustrating functional blocks of the
Fig. 13 is a flowchart (1 thereof) illustrating an evaluation method using the
Fig. 14 is a flowchart (2 thereof) illustrating an evaluation method using the
Fig. 15 is an image of scattered light at a certain time obtained by the
Fig. 16 is a graph showing temporal changes in average scattered light luminance in the region E in fig. 15 (a).
Fig. 17 is a graph illustrating a relationship between the scattering light luminance amplitude value As and the depth of the glass.
Fig. 18 is a diagram illustrating an evaluation apparatus according to
Fig. 19 is a diagram illustrating an evaluation apparatus according to
Fig. 20 is a diagram illustrating an evaluation apparatus according to
Fig. 21 is a diagram illustrating an evaluation apparatus according to modification 4 of the first embodiment.
Fig. 22 is an explanatory diagram of a polarization phase difference variable member utilizing the photoelastic effect.
Fig. 23 is a diagram illustrating an evaluation apparatus according to a second embodiment.
Fig. 24 is a graph in which the stress distributions measured by the
Fig. 25 is a flowchart illustrating an evaluation method using the
Fig. 26 is a diagram illustrating functional blocks of the arithmetic unit 75 of the
Fig. 27 is a diagram illustrating a stress distribution in the depth direction of the tempered glass.
Fig. 28 is a flowchart (1 thereof) of deriving a characteristic value based on a stress distribution.
Fig. 29 is a diagram showing an example in which each characteristic value is derived from the measured stress distribution.
Fig. 30 is a flowchart (2 thereof) of deriving a characteristic value based on a stress distribution.
Fig. 31 is a diagram (1) showing another example in which each characteristic value is derived from the measured stress distribution.
Fig. 32 is a flowchart (3 thereof) of deriving a characteristic value based on the stress distribution.
Fig. 33 is a view (fig. 2) showing another example in which each characteristic value is derived from the measured stress distribution.
Fig. 34 is a diagram showing an example of a flowchart for quality determination using characteristic values obtained by measurement of stress distribution.
Fig. 35 is a diagram showing another example of a flowchart for quality determination using each characteristic value obtained by measurement of the stress distribution.
Fig. 36 is an example of a flowchart (1) of quality determination when lithium-containing glass is strengthened two or more times.
Fig. 37 is an example of a flowchart (2) of quality determination when lithium-containing glass is strengthened two or more times.
Fig. 38 shows an example of a synthesis result of a stress distribution on the glass surface layer side and a stress distribution on the glass deep layer side.
FIG. 39 shows stress distributions obtained in comparative example 1 and examples 1 to 3.
Fig. 40 is a diagram illustrating an evaluation apparatus according to a third embodiment.
Fig. 41 is a view illustrating a scattered light image of the laser light L advancing at the interface between the light supplying member and the tempered glass.
Fig. 42 is a view illustrating a structural portion for sandwiching a liquid between a light supply member and tempered glass.
Fig. 43 is a diagram showing a second example of a structural portion for sandwiching a liquid between a light supply member and tempered glass.
Fig. 44 is a diagram showing a third example of a structural portion for sandwiching a liquid between a light supply member and tempered glass.
Fig. 45 is a diagram showing a fourth example of a structural portion for sandwiching a liquid between a light supply member and tempered glass.
Fig. 46 is a diagram showing a fifth example of a structural portion for sandwiching a liquid between a light supply member and tempered glass.
Fig. 47 is a diagram showing a sixth example of a structural portion for sandwiching a liquid between a light supply member and tempered glass.
Fig. 48 is a diagram showing a seventh example of a structural portion for sandwiching a liquid between a light supply member and tempered glass.
Fig. 49 is a diagram illustrating a case where the laser light L is incident into the tempered glass.
Fig. 50 is a diagram illustrating an image of a laser trace captured from the position of the imaging element of fig. 49.
Fig. 51 is a diagram illustrating definitions of angles and lengths of laser beams in the light supplying member or the tempered glass of fig. 49.
Fig. 52 is a plan view, a front view, and a side view of fig. 51.
Fig. 53 is a conceptual diagram of the laser light advancing through the light supplying member and the tempered glass.
Fig. 54 is a conceptual diagram of a laser beam advancing through a tempered glass.
Fig. 55 is an example of a flowchart for determining the complementary angle of incidence Ψ.
Fig. 56 is an example of a flowchart for determining the refractive index ng of the tempered glass.
Fig. 57 is another example of a flowchart for determining the complementary angle of incidence Ψ.
Fig. 58 is an example of a flowchart for determining θ L that does not change between the surface through which the laser light passes and the observation surface.
Fig. 59 is a diagram illustrating a stress distribution in the depth direction of the tempered glass.
Fig. 60 is a view illustrating an evaluation apparatus provided with a glass thickness measurement device.
Detailed Description
Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and overlapping description may be omitted.
< first embodiment >
Fig. 1 is a diagram illustrating an evaluation apparatus according to a first embodiment. As shown in fig. 1, the
The
As the
In order to improve the resolution in the depth direction of the tempered
Since the cross-sectional shape of the beam emitted from the semiconductor laser is generally an ellipse, the beam is shaped into a circle by the beam shaping member, thereby improving the spatial resolution and the measurement accuracy. Further, although the output distribution of the beam emitted from the semiconductor laser is gaussian in the beam shape, the measurement accuracy can be improved even if the output distribution shaping means shapes the beam into a constant distribution in the beam shape such as a top hat distribution.
The beam shaping member and the output distribution shaping member are interposed between the
The
The
A liquid having a refractive index substantially equal to that of the tempered
The laser light L passing through the tempered
The laser light L is emitted in a direction of θ with respect to the
Next, the
Between the
Further, regarding the lens in which a plurality of lenses are combined, by providing a telecentric lens in which the principal ray is parallel to the optical axis, only light mainly scattered in the 45 ° direction (imaging element direction) with respect to the glass surface of the tempered
Further, a light
As the
The
In this case, various functions of the
The polarization phase
The polarization phase
Since a cell gap of a typical liquid crystal cell is several μm, a maximum polarization phase difference is about 1/2 λ (several hundred nm). Further, in a display using a liquid crystal, etc., no change more than that is required. In contrast, when the wavelength of the laser beam is 630nm, for example, the liquid crystal device used in the present embodiment needs to change the polarization phase difference of about 2000nm, which is about 3 times as large as 630nm, and needs a cell gap of 20 to 50 μm.
The voltage applied to the liquid crystal element is not proportional to the phase difference of the polarized light. For example, fig. 3 shows the relationship between the applied voltage and the polarization phase difference of a liquid crystal element having a cell gap of 30 μm. In fig. 3, the vertical axis represents the polarization phase difference (the number of wavelengths of 630 nm), and the horizontal axis represents the voltage applied to the liquid crystal element (plotted logarithmically).
The voltage applied to the liquid crystal element is 0V to 10V, and the phase difference of the polarized light of about 8 λ (5000nm) can be changed. However, the liquid crystal element generally has unstable alignment of liquid crystal at a low voltage of 0V to 1V, and the polarization phase difference fluctuates due to temperature change or the like. When the voltage applied to the liquid crystal element is 5V or more, the change in the polarization phase difference with respect to the change in the voltage is small. In the case of this liquid crystal element, the polarization phase difference of 4 λ to 1 λ, that is, about 3 λ can be stably changed by using the liquid crystal element under an applied voltage of 1.5V to 5V.
When a liquid crystal device is used as the polarization phase
Fig. 3 is a diagram illustrating a relationship between an applied voltage of the liquid crystal element and a phase difference of polarized light. As shown in fig. 3, the applied voltage of the liquid crystal element and the phase difference of the polarized light do not change linearly. Therefore, it is necessary to generate a signal in which the polarization phase difference linearly changes within a certain time and apply the signal as a driving voltage to the liquid crystal element.
Fig. 4 is a diagram illustrating a circuit for generating a drive voltage by which the polarization phase difference of the liquid crystal element changes linearly in time.
In fig. 4, the digital
[ TABLE 1 ]
The clock
The
In the
Although not shown in fig. 4, the driving circuit of the liquid crystal element is synchronized with the circuit for controlling the
Fig. 5 is a diagram illustrating a scattered light image at a certain moment of the laser light L imaged on the imaging element. In fig. 5, the depth from the
Since a strong compressive stress acts on the surface portion of the tempered
The polarization phase
Fig. 6 is a graph illustrating a temporal change in the brightness (scattered light brightness) of scattered light at points B and C in fig. 5. The temporal change in the intensity of the scattered light periodically changes with the period of the wavelength λ of the laser light in accordance with the changed polarization phase difference of the polarization phase
When considered locally, the phase F of the periodic change in the scattered light luminance associated with the change in the temporal polarization phase difference of the polarization phase
In the present specification, since the laser light L is incident obliquely to the glass, when obtaining a stress distribution with respect to the depth in the vertical direction from the glass surface, conversion from the point s to the depth direction is necessary, as shown in formula 8 (formula 8) described later.
[ mathematical formula 1 ]
On the other hand, the polarization phase
The variation of the scattered light at each point of the scattered light image is periodic, and the period is constant regardless of the position. Therefore, the period T is determined from the change in the intensity of the scattered light at a certain point. Alternatively, the period T may be an average of periods at a plurality of points.
Since the polarization phase difference is changed by 1 wavelength or more (1 cycle or more) in the polarization phase
In the data of the periodic change of the scattered light at a certain point, the phase F at the certain point can be accurately obtained by the least squares method or fourier integration of the trigonometric function based on the determined period T.
In the least squares method or fourier integration of the trigonometric function at a previously known period T, only the phase component at the known period T is extracted, and the noise at other periods can be removed. The longer the temporal change of data is, the higher the removal capability is. In general, since the scattered light brightness is weak and the actually changing phase amount is small, measurement based on variable data of the polarization phase difference of several λ is necessary.
When the time-based change data of the scattered light at each point along the scattered light image of the laser light L on the image captured by the
In the phase F along the scattered light intensity of the laser light L, the differential value at the coordinate on the laser light L is calculated, and the stress value at the coordinate s on the laser light L can be obtained by
Fig. 9 shows an example of an actual scattered light image at different times t1 and t2, and point a in fig. 9 shows the surface of the tempered glass, and the surface scattered light is reflected by the roughness of the surface of the tempered glass. The center of the surface scattered light image corresponds to the surface of the tempered glass.
In fig. 9, it is understood that the scattered light image of the laser light has different brightness at each point, and that the brightness distribution at time t2 is different from the brightness distribution at time t1 even at the same point. This is due to the phase shift of the periodic scattered light brightness change.
In the
Fig. 10 is a diagram showing an unfavorable design example of the incident surface of the laser light L in the tempered glass. In fig. 10, the
Fig. 10(b) is a view seen from the direction H of fig. 10 (a). As shown in fig. 10(b), the
Fig. 11 is a diagram showing a preferred design example of the incident surface of the laser light L in the tempered glass. In fig. 11, the
Fig. 11(b) is a view seen from the direction H of fig. 11 (a). As shown in fig. 11(b), the
In particular, when a laser beam having a minimum beam diameter of 20 μm or less is used, the focal depth is shallow, and is at most about several tens of μm. Therefore, it is very important to obtain a good image if the
Fig. 12 is a diagram illustrating functional blocks of the
The
(measurement flow 1: measurement of stress distribution of tempered glass)
Fig. 13 is a flowchart (1) illustrating an evaluation method using the
The measurement shown in fig. 13 may be performed, for example, after the step of producing tempered glass by subjecting the original plate to a tempering treatment. The measurement shown in fig. 13 is performed after the step of producing crystallized glass by subjecting the original plate to crystallization treatment, and further producing reinforced crystallized glass by subjecting the produced crystallized glass to reinforcing treatment.
First, in step S401, the polarization phase difference of the laser light from the
Next, in step S402, the laser light whose polarization phase difference is changed is made to enter the tempered
Next, in step S403, the
Next, in step S404, the luminance change measurement means 701 of the
Next, in step S405, the phase change calculation means 702 of the
Next, in step S406, the stress distribution calculating means 703 of the
(measurement flow 2: measurement of stress distribution of tempered glass and measurement of physical quantity relating to Strength)
The
Fig. 14 is a flowchart (2) illustrating an evaluation method using the
The measurement shown in fig. 14 may be performed, for example, after the step of producing crystallized glass by subjecting the original plate to crystallization treatment, and further producing strengthened crystallized glass by subjecting the produced crystallized glass to strengthening treatment.
First, steps S401 to S403 are executed as in the case of fig. 13. Then, step S414 is executed in parallel with steps S404 to S406. In step S414, the physical quantity measuring means 704 of the
Here, the "physical quantity related to the strength of the strengthened glass" includes physical quantities such as a refractive index, a crystallization ratio, a crystal grain diameter, a crystal grain density, a haze, and an amount of defects or impurities in the glass, and parameters (a scattering light intensity amplitude value, an average scattering light intensity, a scattering light intensity variance value, and the like) necessary for obtaining these physical quantities. That is, the physical quantity measuring means 704 may measure only the amplitude value of the scattered light intensity or the average scattered light intensity without directly measuring the physical quantity such as the crystallization ratio. In this case, the strength of the tempered glass can also be estimated from the measurement result of the physical quantity measuring means 704.
The measurement of the physical quantity related to the strength of the tempered glass will be described in more detail below.
(measurement example 1 of physical quantity relating to Strength of tempered glass)
Fig. 15(a) is an image of scattered light at a certain time obtained by the
Typically, the scattered light comprises scattered light produced by several scattering mechanisms. Scattered light having the same wavelength as that of incident light differs in scattering property due to the relationship between the size and wavelength of the scattered particles. When the wavelength λ of the incident light is constant, the scattering particles are scattered by the scattering mechanism under rayleigh scattering when the size of the scattering particles is sufficiently small, and the scattering mechanism under mie scattering starts from position D ═ λ × 1/10, and becomes completely mie scattering at D ≧ λ.
The haze of the crystallized glass is determined by the crystal grain size, the crystal grain density, and the difference in refractive index between the crystal and the glass phase. Although haze is reduced as the refractive index difference between the crystal and the glass phase is smaller, it is difficult to completely match the refractive index between the crystal and the glass phase, and there is generally a refractive index difference of about 0.05 to 0.50. For example, when the difference in refractive index between the crystal and the glass phase is about 0.1, the crystal grain size (diameter of crystal grain) of the reinforced crystallized glass is transparent under visible light, and therefore, the crystal grain size of the reinforced crystallized glass is controlled to be sufficiently smaller than the wavelength of visible light by about 600nm and controlled to be 10nm to 100 nm. Therefore, although the rayleigh scattering mechanism is dominant in most cases, the influence of the mie scattering mechanism appears also at 100nm where the crystal grain size is the largest. The brightness of scattered light, whether rayleigh scattering or mie scattering, is in high order proportion to the diameter of the scattering particles and in proportion to the density of the scattering particles. In rayleigh scattering, the scattering particle diameter is proportional to the 6 th power, and in mie scattering, the scattering particle diameter is proportional to the 2 nd power, and this period can be considered in a region where the rayleigh scattering changes to the mie scattering mechanism. That is, in rayleigh scattering and mie scattering, which do not change in wavelength from incident light, the higher the scattering particle diameter, the higher the density, and the higher the scattering light intensity.
Further, there are fluorescence scattering and raman scattering as scattering in which the wavelength of scattered light is different from the wavelength of incident light. In general, fluorescence scattering occurs due to impurities or defects in the glass, and raman scattering occurs due to the composition or bonding state.
Among the scattering mechanisms described above, in rayleigh scattering, the brightness of scattered light differs depending on the polarization state of incident light. In the measurement of the stress, birefringence is generated due to the photoelastic effect of the internal stress, the laser light L advances in the glass, and the state of the polarized light changes, with which the scattered light brightness changes. This is used in the principle of the
In the
The scattering light intensity amplitude value As Is determined by the size of the crystal grains of the reinforced crystallized glass, which are scattering particles, and the crystal grain density, and the ratio of the average scattering light intensity Is to the scattering light intensity amplitude value As Is determined by the ratio of the rayleigh scattering component to the mie scattering component, and thus Is determined by the size of the crystal grains, which are scattering particles.
From the two measured values of the scattered light luminance amplitude value As and the average scattered light luminance Is, the absolute values of the direct scattered particle diameter and the scattered particle density cannot be calculated. However, in the strengthened crystallized glass having different scattering particle diameters, scattering particle densities, that Is, crystal particle diameters, and crystal particle densities, the values of the scattering luminance amplitude value As and the average scattering luminance value Is are different, and the differences can be observed independently from each other. That Is, although the absolute values of the scattering particle diameter and the scattering particle density cannot be directly calculated, by measuring the scattered light luminance amplitude value As or the average scattered light luminance Is, it Is possible to know the variation in the scattering particle diameter and the scattering particle density.
Further, the crystal grain size or the crystal grain density can be estimated by measuring the scattering grain size and the scattering grain density by another method and experimentally obtaining the relationship between the scattering brightness amplitude value As and the average scattering brightness Is and the crystal grain size or the crystal grain density.
For example, the relationship between the scattering light intensity amplitude value As and the average scattering light intensity Is and the crystal grain size or the crystal grain density Is experimentally obtained and stored in advance As a table or a function in the memory in the
The measured values of the amplitude value As of the scattered-light intensity and the average scattered-light intensity Is, which reflect the particle diameter and the particle density of the scattered particles, are values in the region E in fig. 15 (a). However, if the measurement region is moved from the glass surface of the laser image to each depth in the depth direction and measured, the scattering particle diameter and the scattering particle density in the depth direction of the reinforced crystallized glass can be known. This confirmed that the crystallized state was uniform in the depth direction from the surface.
(measurement example 2 of physical quantity relating to Strength of tempered glass)
As shown in fig. 15(b), the scattered light image is not uniform and is in a particle shape. This is because the incident light is laser light, and unevenness due to speckle is called a speckle pattern. The speckle pattern is determined by the size, density, and optics of the scattering particles.
The degree of unevenness in luminance of the speckle pattern, for example, the variance value of the luminance of the region E is calculated and set to be Ss. The variance value Ss reflects the scattering particle density. When the crystal grain size is small, the mie scattering component is small, and the intensity of the mie scattering component cannot be measured, the crystal grain size and the crystal grain density can be estimated from the variance value Ss of the luminance of the speckle pattern and the scattered light luminance amplitude value As.
That is, even if the absolute value of the scattering particle diameter or the scattering particle density is not directly calculated, the dispersion of the scattering particle diameter or the scattering particle density can be known by measuring the variance value Ss or the scattered light luminance amplitude value As. Similarly to the case of the scattered light intensity amplitude value As and the average scattered light intensity Is, the crystal grain diameter or the crystal grain density can be estimated by measuring the scattered particle diameter and the scattered particle density, experimentally obtaining the relationship between the variance value Ss and the scattered light intensity amplitude value As and the crystal grain diameter or the crystal grain density, and storing the relationship in advance As a table or a function in the memory in the
(measurement example 3 of physical quantity relating to Strength of tempered glass)
In fig. 15(a), θ is an angle along the beam of the laser light of the scattered light image. The angle θ is determined by the refractive index of the glass to be measured, and will be described later.
The refractive index of the light-supplying
On the other hand, in many cases, the refractive index of the glass itself is different from that of the precipitated crystal in the strengthened crystallized glass. For example, in a strengthened crystallized glass using a lithium aluminosilicate base material, the refractive index of the glass of the base material is 1.52, and the refractive index of the precipitated β spodumene is 1.66. The volume ratio of the precipitated crystal to the matrix is about 10 to 50%, and the refractive index of the whole crystal changes according to the volume ratio of the crystal. That is, the volume fraction of crystallization can be calculated by measuring the refractive index of the reinforced crystallized glass.
(measurement example 4 of physical quantity relating to Strength of tempered glass)
Fig. 17 illustrates the relationship between the amplitude value As of the scattered light luminance and the depth of the glass. The external haze value of the glass surface layer 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 of the inside of the glass. The transmittance can be estimated by using the external haze value and the internal haze value. When one of the haze values is small, the estimation may be performed using only the other haze value. Further, the chromaticity of the tempered glass may be estimated by estimating the transmittance at each wavelength by using a plurality of laser beams. Further, the surface of the glass may be determined by measuring both surfaces of the glass and examining the difference between the surface layers of the glass based on the difference in the amplitude value of the scattered light brightness or the difference in transmittance. Specifically, an antiglare surface, an antifingerprint surface, an AR coating surface, an antibacterial surface, an ITO surface, a floating transfer surface (tin surface), and the like can be considered.
The measured values of the amplitude value As of the scattered-light brightness, 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, but are also useful As numerical values indicating the quality such As defects, composition, unevenness, transparency, and the like of the glass, such As impurities or abnormal crystallization, in the non-crystallized reinforced glass. That is, the measurement shown in fig. 14 may be performed after the step of producing a strengthened glass (not a strengthened crystallized glass) by subjecting the original plate to a strengthening treatment. Further, physical quantities other than those shown in measurement examples 1 to 4 described above may be measured.
As described above, in the
The polarization phase difference of the laser beam is changed by 1 wavelength or more continuously in time with respect to the wavelength of the laser beam by the polarization phase
In the
<
In
Fig. 18 is a diagram illustrating an evaluation apparatus according to
The optical
The optical
The optical
In the
The optical wavelength selection members are not limited to two types, and three or more types may be arranged so as to be switchable.
<
In
Fig. 19 is a diagram illustrating an evaluation apparatus according to
The
The wavelengths of the
In the
The laser light source and the optical wavelength selection member are not limited to two types, and three or more types may be arranged so as to be switchable.
In addition, similar effects can be obtained even when a plurality of
<
In
Fig. 20 is a diagram illustrating an evaluation apparatus according to
In the evaluation apparatus 1C, the scattered light L generated on the
Although the reflection of the laser light L on the
Since the tempered
The scattered light L on the
Alternatively, as in the evaluation apparatus 1D shown in fig. 20(b), the scattered light L generated on the
Although the reflection of the laser light L on the
In both of the evaluation devices 1C and 1D, as in the
In particular, according to the evaluation apparatus 1D, the focal point of the laser light is set to the same position from the surface layer of the glass regardless of the thickness of the glass sheet. Therefore, even when the tempered glass having the same stress distribution is measured, the focal position of the laser light does not need to be adjusted or fine-tuned, and thus the effect of shortening the measurement time or further improving the repetition accuracy is obtained.
< modification 4 of the first embodiment >
In modification 4 of the first embodiment, another example of an evaluation apparatus having a different configuration from that of the first embodiment is shown. In modification 4 of the first embodiment, description of the same components as those of the above-described embodiment may be omitted.
Fig. 21 is a diagram illustrating an evaluation apparatus according to modification 4 of the first embodiment. As shown in fig. 21, the
In the
In the
< modification 5 of the first embodiment >
In modification 5 of the first embodiment, an example of a polarization phase difference variable member having a different configuration from that of the first embodiment is shown. In modification 5 of the first embodiment, description of the same components as those of the above-described embodiment may be omitted.
The polarization phase difference varying member may be made of a transparent material and may vary the polarization phase difference by applying pressure, using the photoelastic effect of the transparent material. Fig. 22 is an explanatory diagram of a polarization phase difference variable member utilizing the photoelastic effect.
In the polarization phase difference
The two
When a voltage is applied, the
In the
When a voltage in the direction in which the
For example, 10mm cubic polycarbonate is used as the polarized light phase
As the
Since the young's modulus of lead zirconate titanate, which is a material of the
For example, 10mm cubic quartz glass is used as the polarized light phase
When the polarizing retardation is produced by deforming the material in this way, the value obtained by multiplying the photoelastic constant by the young's modulus is important, and is 0.18 (no unit) in the case of polycarbonate and 0.26 (no unit) in the case of quartz. That is, it is important to use a transparent member having a value of 0.1 or more as the polarization phase
As described above, the polarization phase difference varying member is not limited to the liquid crystal device, and may be a mode using a piezoelectric element or any other mode as long as the polarization phase difference when entering the tempered
< second embodiment >
In the second embodiment, an example of an evaluation apparatus used in combination with the evaluation apparatus of the first embodiment is shown. In the second embodiment, description of the same components as those of the above-described embodiment may be omitted.
Fig. 23 is a diagram illustrating an evaluation apparatus according to a second embodiment. For example, Yogyo-Kyokai-Shi (journal of the kiln Association) 87{3}1979 and the like. As shown in fig. 23, the
In the
As the light source 15, for example, a Na lamp, which easily obtains light of a single wavelength, may be used, and the wavelength in this case is 589.3 nm. As the light source 15, a mercury lamp having a shorter wavelength than an Na lamp can be used, and the wavelength in this case is 365nm, which is a mercury I line, for example. However, since the mercury lamp has many bright lines, it is preferably used by passing through a band-pass filter that transmits only 365nm light.
In addition, an led (light Emitting diode) may be used as the light source 15. In recent years, many wavelength LEDs have been developed, but the spectral width of an LED is 10nm or more at half-width, the single wavelength property is poor, and the wavelength changes depending on temperature. Therefore, it is preferably used by passing through a band-pass filter.
When the light source 15 is an LED and is configured to pass through a band-pass filter, the single wavelength is not as good as that of an Na lamp or a mercury lamp, but it is preferable to use any wavelength from the ultraviolet region to the infrared region. Since the wavelength of the light source 15 does not affect the basic principle of the measurement by the
However, by using a light source for irradiating ultraviolet rays as the light source 15, the resolution of measurement can be improved. That is, since the surface layer of the tempered
The light supplying member 25 and the light extracting member 35 are placed in optical contact with the
As the light supplying member 25 and the light extracting member 35, for example, a prism made of optical glass can be used. In this case, in order to optically enter and exit light through these prisms in the
For example, when the tilt angle of the prism is 60 ° and the refractive index of the tempered
The image pickup device 65 is disposed in the direction of the light emitted from the light extraction member 35, and the light conversion member 45 and the polarization member 55 are interposed between the light extraction member 35 and the image pickup device 65.
The light conversion member 45 has a function of converting the light emitted from the light extraction member 35 into a bright line and condensing the bright line on the image sensor 65. As the light conversion member 45, for example, a convex lens may be used, but another member having the same function may be used.
The polarizing member 55 is a light separating means having a function of selectively transmitting one of two light components vibrating parallel and perpendicular to the interface between the
The interface between the
The image pickup device 65 has a function of converting light emitted from the light extraction member 35 and received through the light conversion member 45 and the polarization member 55 into an electric signal. As the imaging element 65, for example, the same element as the
The arithmetic unit 75 has a function of acquiring image data from the imaging device 65 and performing image processing or numerical calculation. The calculation unit 75 may have other functions (for example, a function of controlling the light amount of the light source 15 or the exposure time). The operation 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 a 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 necessary. However, a part or all of the arithmetic unit 75 may be realized by hardware only. The arithmetic unit 75 may also physically include a plurality of devices. As the arithmetic unit 75, for example, a personal computer can be used.
In the
Then, the light is converted into bright lines of P-polarized light and S-polarized light for each mode by the light conversion means 45 and the polarizing means 55, and the bright lines are imaged on the imaging element 65. The image data of the bright lines of P-polarized light and S-polarized light of the number of patterns generated in the image pickup device 65 is transmitted to the arithmetic unit 75. The arithmetic unit 75 calculates the positions of the bright lines of the P-polarized light and the S-polarized light on the image sensor 65 based on the image data transmitted from the image sensor 65.
With such a configuration, in the
In this way, the
On the other hand, in the scattered light image shown in fig. 9 of
The depth of the portion where the surface scattered light overlaps varies depending on the properties of the glass and the surface state of the glass, but is usually about 10 μm. In a tempered glass having a deep strengthened layer, a low surface stress value in which a change in stress in the depth direction is gradual, or a deep strengthened layer, in the vicinity of the outermost surface, for example, in a surface region having a depth of about 10 μm, even if the depth is within 10 μm, which cannot be accurately measured, the distribution of stress at a portion deeper than the depth can be extrapolated to the glass surface to estimate an accurate stress.
However, in the tempered glass in which the stress distribution of the tempered
By adding the stress value of the outermost surface, the stress value of the stress distribution in the vicinity of the outermost surface measured by the
Even when a sufficiently reliable depth region of the
Fig. 24 is a graph showing the stress distributions measured by the
In the example of fig. 24, there is a region B that is not measured by either the
(procedure of measurement)
Next, the flow of measurement will be described with reference to fig. 25 and 26. Fig. 25 is a flowchart illustrating an evaluation method using the
First, in step S407, light from the light source 15 is made incident into the surface layer of the tempered glass 200 (light supply step). Next, in step S408, the light propagating through the surface layer of the tempered
Next, in step S409, the light conversion member 45 and the polarizing member 55 convert two kinds of light components (P-polarized light and S-polarized light) of the emitted light, which vibrate parallel to and perpendicular to the emission surface, into two kinds of bright line arrays each having at least two bright lines (light conversion step).
Next, in step S410, the imaging element 65 images the two kinds of bright line sequences converted by the light conversion process (an imaging process). Next, in step S411, the position measurement unit 751 of the arithmetic unit 75 measures the position of each of the two bright lines from the image obtained in the imaging step (position measurement step).
Next, in step S412, the stress distribution calculating means 752 of the calculating unit 75 calculates the refractive index distribution in the depth direction from the surface of the tempered
Next, in step S413, the synthesizing unit 753 of the arithmetic unit 75 synthesizes the stress distribution calculated in step S412 with the stress distribution calculated by the stress
When the sufficiently reliable depth region of the
In addition to the configuration of fig. 26, the calculation unit 75 may include a CT value calculation unit that calculates a CT value, a DOL _ Zero value calculation unit that calculates a DOL _ Zero value, and the like. In this case, the CT value and DOL _ Zero value can be calculated based on the stress distribution calculated by the synthesizing unit 753.
Next, an example of deriving each characteristic value of the stress distribution will be described. Fig. 27 is a diagram illustrating a stress distribution in the depth direction of the tempered glass. In fig. 27, CS2 is the outermost stress value, CS _ TP is the stress value at the position where the stress distribution is bent, CT is the stress value at the deepest portion of the glass, DOL _ TP is the glass depth at the position where the stress distribution is bent, DOL _ zero is the glass depth at which the stress value becomes 0, and DOL _ tail is the glass depth at which the stress value becomes the same value as CT.
As shown in fig. 28, the stress distribution is 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 in fig. 30, the entire distribution of the stress distribution (entire solid line shown in fig. 29) is measured by the
In step S604, each characteristic value is derived as follows, for example. That is, as shown in fig. 29, two line segments, i.e., a line segment passing through CS2 and a line segment passing through DOL _ zero, are considered. When the difference between the two line segments and the measured stress distribution becomes minimum, the intersection point of the two line segments is CS _ TP and DOL _ TP. Then, the intersection of the line segment passing through DOL _ zero and CT is DOL _ tail.
This method can be applied to, for example, a lithium aluminosilicate-based tempered glass, a tempered glass that has been chemically tempered once with a mixed salt of sodium nitrate and potassium nitrate, a tempered glass that has been chemically tempered with a molten salt containing sodium nitrate and a molten salt containing potassium nitrate each used once or more, a tempered glass that has been both air-cooled tempered and chemically tempered, and the like.
Fig. 31 shows another example in which each characteristic value is derived from the measured stress distribution. For example, in step S601 in fig. 32, the entire distribution of the stress distribution is measured by the
Next, in step S603, the portion measured in step S602 is combined with the portion measured in step S601 on the deeper side than the portion measured in step S602. This makes it possible to obtain the stress distribution shown in fig. 31. Then, for example, each characteristic value can be derived in the same manner as step S604 of fig. 30.
Alternatively, in step S602, DOL _ zero and CT are measured in step S601, as described above. Then, in step S603, as shown in fig. 33, a straight line passing through 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.
The quality can be determined by using the characteristic values obtained by measuring the stress distribution. Fig. 34 is an example of a flowchart of quality determination using characteristic values obtained by measurement of stress distribution. In fig. 34, first, steps S601 to S603 are executed as in fig. 32. Next, in step S604, six characteristic values (hereinafter, may be referred to as only six measurement values) of CS2, CS _ TP, CT, DOL _ TP, DOL _ zero, and DOL _ tail are derived based on the data obtained in steps S601 and S602. Next, in step S605, it is determined whether the six characteristic values derived in step S604 fall within the allowable range determined by the prior requirement specification. In this method, two measurements in steps S601 and S602 are necessary for one quality determination.
Fig. 35 is another example of a flowchart of quality determination using characteristic values obtained by measurement of stress distribution. In fig. 35(a), first, preliminary data is acquired in step S600. Specifically, for example, for a predetermined number of batches, 6 characteristic values are derived using the
Next, in step S601, the
Next, in step S605, it is determined whether or not the six characteristic values measured in step S604 have entered the allowable range determined in step S600. In this method, only one measurement in step S601 is required for one quality determination, in addition to the number of measurements in the preliminary step. This can simplify the quality control flow as compared with the case of fig. 34.
Note that the plate thickness is also measured in the preliminary data of fig. 35(a), and by measuring the plate thickness also in step S601, the characteristic value can be derived in step S604 including the effect of the difference in plate thickness.
Alternatively, the same may be applied as shown in fig. 35 (b). In fig. 35(b), as in fig. 35(a), first, in step S600, preliminary data is acquired, and an allowable range of the characteristic value is determined.
Next, in step S602, the
Next, in step S605, it is determined whether or not the six characteristic values measured in step S604 have entered the allowable range determined in step S600. In this method, only one measurement in step S602 is required for one quality determination, in addition to the number of measurements in the preliminary step. In this case as well, the quality control flow can be simplified as compared with the case of fig. 34, as in fig. 35 (a).
Note that the plate thickness is also measured in the preliminary data of fig. 35(b), and by measuring the plate thickness also in step S602, the characteristic value can be derived in step S604 including the effect of the difference in plate thickness.
Fig. 36 is an example of a flowchart of quality judgment when lithium-containing glass (glass containing 2 wt% or more of lithium) such as lithium aluminosilicate-based tempered glass is tempered twice or more. In fig. 36, whether or not the strengthened glass of the strengthening process other than the final strengthening process is acceptable is determined based on the measurement result of the
Specifically, first, the first chemical strengthening is performed in step S650. Then, in step S651, the
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
As the next step, for example, a contact polishing step can be cited. The contact polishing step is a finish polishing step of polishing the surface of the tempered
After step S653, chemical strengthening and a pass/fail determination may be performed for the third time. In this case, in step S653, the strengthened glass for the second strengthening is determined to be acceptable based on the measurement result of the
Similarly, when the number of times of strengthening is further increased, whether or not the strengthened glass of strengthening other than the final strengthening is acceptable is determined based on the measurement result of the
Here, a specific method of the non-qualification determination (non-qualification determination) in step S653 will be described.
(data derivation for evaluation)
First, data for evaluation is derived in advance. Specifically, as shown in fig. 37, in step S660, the first chemical strengthening is performed. Then, in step S661, the
The evaluation data derivation is performed only by using a predetermined number for one batch. 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 in mass production.
(method of judging acceptability in step S653)
First, based on the measurement result obtained in step S653, the sheet thickness t of the glass that is chemically strengthened, and the evaluation data obtained as shown in fig. 37, the stress distribution on the glass surface layer side from DOL _ TP (second stress distribution) and the stress distribution on the glass depth layer side from DOL _ TP (first stress distribution) are synthesized. For example, the results shown in fig. 38 were obtained.
In fig. 38, FSM indicated by a solid line indicates a stress distribution (second stress distribution) on the glass surface layer side from DOL _ TP, and SLP indicated by a broken line indicates a stress distribution (first stress distribution) on the glass deep layer side from DOL _ TP. Further, t/2 represents the center of the thickness of the glass. And, CS0The first stress distribution (SLP) indicates a stress value of the surface when the surface side of the tempered glass is extended.
Next, each characteristic value is derived by finding CT from the synthesized stress distribution, and whether or not each characteristic value is within an allowable range is determined (shipment determination).
At this time, the second stress profile (FSM of fig. 38) may also be functionally approximated. As an example of the function approximation, a case of performing a straight line approximation by the following expression 2 (expression 2) can be cited.
[ mathematical formula 2 ]
σf(x)＝a·x+CS2…(2)
In
As another example of the function approximation, a curve approximation may be performed by the following expression 3 (expression 3).
[ mathematical formula 3 ]
σf(x)＝CS2·erfc(a·x)…(3)
In
[ mathematical formula 4 ]
As another example of the function approximation, polynomial approximation may be performed.
In addition, the first stress distribution (SLP of fig. 38) may be shifted in the up-down direction of fig. 38 (stress value axial direction). Specifically, for example, in the synthesized stress distribution shown in fig. 38, the first stress distribution (SLP) is moved in the stress value axial direction, and each characteristic value is derived by finding a CT in which the integral value of the synthesized stress distribution becomes 0. Then, whether or not the characteristic values are within the allowable range can be determined (shipment determination). In this case, the amount of vertical movement of the first stress distribution may be calculated by a theoretical equation based on the sheet thickness of the glass and the second stress distribution, or the amount of movement may be assumed, an integrated value of the synthesized stress distribution may be calculated, and a movement amount at which the integrated value becomes 0 may be found.
The synthesized stress distribution σ (x) is approximated by the following equation 5 (equation 5), and each characteristic value is derived by finding a CT in which the integral value (x is 0 to t/2: t is the thickness of the glass) of σ (x) becomes 0. Then, the acceptance determination (shipment determination) may be performed based on whether or not each characteristic value enters the allowable range.
[ math figure 5 ]
In formula 5, σ (x) is the stress distribution after synthesis, σ f (x) is the second stress distribution, t is the thickness of the strengthened glass, and CS is0And c is a parameter derived based on the first stress distribution.
In formula 5, t is known. And, CS0And c can be obtained from the measurement result of the
CS0And c can also be derived from simulations based on the intensification conditions.
Or, CS0And c can also be derived from the measurement result of the
[ mathematical formula 6 ]
CS0＝A1×CS0′…(6)
In
[ mathematical formula 7 ]
c＝A2×c′…(7)
In equation 7, a2 is a proportionality constant.
Here, a1 and a2 may be obtained from the measurement results of the
The approximation of σ (x) is not limited to expression 5, and may be a polynomial approximation, for example.
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