Stress measurement device for strengthened glass, stress measuring method for strengthened glass, manufacturing method of strengthened glass, and strengthened glass

Patent metadata

Field	Value
Publication number	US-11274981-B2
Application number	US-201916363010-A
Country	US
Kind code	B2
Filing date	Mar 25, 2019
Priority date	Sep 26, 2016
Publication date	Mar 15, 2022
Grant date	Mar 15, 2022

Abstract

A stress measurement device for strengthened glass includes a polarization phase difference variable member configured to vary a polarization phase difference of a laser light by one wavelength of the laser light or more; an imaging element configured to image a plurality of times at a predetermined time interval a scattered light emitted according to the laser light with the varied polarization phase difference entering the strengthened glass, and obtain a plurality of images; and an arithmetic unit configured to measure a periodic change in luminance of the scattered light using the plurality of images, calculate a change in a phase of the change in luminance, and calculate a stress distribution in a depth direction from a surface of the strengthened glass based on the change in the phase.

First claim

What is claimed is:

1. A stress measurement device for strengthened glass comprising:
a polarization phase difference variable member configured to vary a polarization phase difference of a laser light by one wavelength of the laser light or more;
an imaging element configured to image a plurality of times at a predetermined time interval a scattered light emitted according to the laser light with the varied polarization phase difference entering the strengthened glass, and obtain a plurality of images; and
an arithmetic unit configured to measure a periodic change in luminance of the scattered light using the plurality of images, calculate a change in a phase of the change in luminance, and calculate a stress distribution in a depth direction from a surface of the strengthened glass based on the change in the phase.

2. The stress measurement device for strengthened glass according to claim 1 ,
wherein the polarization phase difference variable member is a liquid crystal element.

3. The stress measurement device for strengthened glass according to claim 1 ,
wherein a product of a photoelastic constant and a Young's modulus of the polarization phase difference variable member is 0.1 or more, and
wherein the polarization phase difference variable member is a transparent member that generates the polarization phase difference by applying a stress.

4. The stress measurement device for strengthened glass according to claim 1 ,
wherein the transparent member is configured of quartz glass or polycarbonate.

5. The stress measurement device for strengthened glass according to claim 1 ,
wherein a position of a smallest beam diameter of the laser light is located in an ion exchange layer of the strengthened glass, and
wherein the smallest beam diameter is 20 μm or less.

6. The stress measurement device for strengthened glass according to claim 1 ,
wherein an incident surface of the laser light incident on the strengthened glass is inclined by 45±5° with respect to the surface of the strengthened glass.

7. The stress measurement device for strengthened glass according to claim 6 further comprising:
a light supply member for causing the laser light with the varied polarization phase difference to enter the strengthened glass, which is a subject to be measured, obliquely with respect to the surface of the strengthened glass,
wherein an angle of a surface of the light supply member on which the laser light is incident is set so that the incident surface of the laser light incident on the strengthened glass is inclined by 45±5° with respect to the surface of the strengthened glass.

8. The stress measurement device for strengthened glass according to claim 1 further comprising:
a light supply member for causing the laser light with the varied polarization phase difference to enter the strengthened glass, which is a subject to be measured, obliquely with respect to the surface of the strengthened glass; and
a liquid between the light supply member and the strengthened glass, a difference between a refractive index of the liquid and a refractive index of the strengthened glass being 0.03 or less,
wherein a thickness of the liquid is 10 μm or more and 500 μm or less.

9. The stress measurement device for strengthened glass according to claim 8 ,
wherein a recess having a depth of 10 μm or more and 500 μm or less is formed on a surface of the light supply member in contact with the strengthened glass, and
wherein the recess is filled with the liquid.

10. The stress measurement device for strengthened glass according to claim 8 ,
wherein a projection part in contact with the strengthened glass is provided on a surface of the light supply member,
wherein the projection part forms a part of an optical path of the laser light incident into the strengthened glass via the light supply member,
wherein a recess having a depth of 10 μm or more and 500 μm or less is formed on the projection part on a side in contact with the strengthened glass, and
wherein the recess is filled with the liquid.

11. The stress measurement device for strengthened glass according to claim 10 ,
wherein the projection part is held attachably or detachably to/from a surface of the light supply member.

12. The stress measurement device for strengthened glass according to claim 10 ,
wherein a flat outer edge portion is formed around the recess, and
wherein the flat outer edge portion is a surface in contact with the strengthened glass.

13. The stress measurement device for strengthened glass according to claim 9 ,
wherein the recess includes a surface provided with a curved portion.

14. The stress measurement device for strengthened glass according to claim 9 ,
wherein a groove for discharging the liquid is formed on a periphery of the recess.

15. The stress measurement device for strengthened glass according to claim 9 ,
wherein when a refractive index of the light supply member and the refractive index of the strengthened glass are different from each other,
the refractive index of the strengthened glass is acquired,
an incident complementary angle when the laser light is incident on the strengthened glass is derived from a relation between a trajectory of the laser light in the strengthened glass obtained based on the refractive index of the strengthened glass and an image of the laser light acquired by the imaging element,
a stress distribution that is in a depth direction from the surface of the strengthened glass is corrected based on a value of the incident complementary angle.

16. The stress measurement device for strengthened glass according to claim 15 ,
wherein the refractive index of the strengthened glass is obtained based on the image of the laser light acquired by the imaging element.

17. The stress measurement device for strengthened glass according to claim 1 ,
wherein when a thickness of the strengthened glass is known, a phase change amount with respect to an outermost surface of the strengthened glass that balances a stress balance is estimated based on the calculated stress distribution and the thickness of the strengthened glass, and a surface stress value is corrected.

18. The stress measurement device for strengthened glass according to claim 1 further comprising:
a means for measuring a thickness of the strengthened glass,
wherein the stress distribution and the thickness of the strengthened glass are measured, and a phase change amount with respect to an outei most surface of the strengthened glass is estimated based on the measured thickness of the strengthened glass.

19. The stress measurement device for strengthened glass according to claim 1 ,
wherein on an emission side of the laser light of the strengthened glass, the laser light in the strengthened glass satisfies a condition of total reflection.

20. The stress measurement device for strengthened glass according to claim 1 further comprising:
a second light supply member for causing a light from a second light source to be incident into a surface layer having a compressive stress layer of the strengthened glass;
a light extraction member for emitting a light propagated in the surface layer to the outside of the strengthened glass;
a light conversion member for converting two kinds of light components oscillating in parallel to and orthogonal to a boundary surface between the strengthened glass and the light extraction member included in the light emitted via the light extraction member, into two kinds of bright line array

Assignees

• Orihara Ind Co Ltd
• Agc Inc

Inventors

• Orihara Shuji
• Orihara Yoshio
• Ogami Satoshi
• Inaba Seiji

Classifications

• G02F1/13

  based on liquid crystals, e.g. single liquid crystal display cells · CPC title

• G01L5/0047 Primary

  measuring forces due to residual stresses · CPC title

• C03C21/002

  to perform ion-exchange between alkali ions (C03C21/005 takes precedence) · CPC title

• G01L1/00

  Measuring force or stress, in general (measuring force due to impact G01L5/00) · CPC title

• C03B18/12

  Making multilayer, coloured or armoured glass (chemical aspects C03C) · CPC title