JPS5937451B2 - Surface stress measuring device for chemically strengthened glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved surface stress measuring device for chemically strengthened glass.

As is well known, in order to manufacture chemically strengthened glass, the glass is immersed in potassium salt (for example, KNO3) molten at high temperature, and the Na+ ions near the glass surface are exchanged with larger ion diameters. Generates compressive stress on the glass surface through ion exchange to prevent breakage from occurring due to external force (
In other words, the so-called ion exchange method is used to improve the strength.

By the way, the chemically strengthened glass obtained by the above method has a large compressive stress generated on the surface, and the thicker the layer where compressive stress is generated, the higher its strength, so measuring the amount of compressive stress is a quality control method. It is important in the above.

For this reason, the conventional method for measuring the stress on the surface of chemically strengthened glass is to cut the tempered glass to a thickness of 0.
．． A method is used in which the stress on the surface of the tempered glass and the layer thickness where the stress exists are measured by polishing the glass into a thin piece of about 1 to 0.5 m771 and observing its cross section with a photoelastic microscope.

However, the above method has various problems as described below and is not practical.

In other words, the first problem is that it is a destructive measurement method.
Skilled work 5 when producing thin sections as test materials
The drawback is that it requires a large amount of time and effort to manufacture. The second problem is that when manufacturing thin sections, the surface stress is relaxed by a proportion corresponding to the Poisson's ratio of the glass, resulting in a considerable zero deviation between the true value and the measured value. That's true. Third
The problem with this is that it is difficult to measure the true photoelastic effect on a glass surface under a microscope, so there is an unavoidable risk of personal error. The present invention has been made in order to solve the above-mentioned various problems all at once, and by utilizing the fact that the surface layer of chemically strengthened glass exhibits an optical waveguide effect, it is possible to reduce the surface stress of chemically strengthened glass. It is an object of the present invention to provide a device that can non-destructively measure the thickness of a compressive stress layer quickly and with high accuracy.

10, one embodiment of the present invention will be described below with reference to the drawings.

In the figure, reference numeral 1 denotes an incident glass prism as a light supplying member that is placed on one end of the surface of the chemically strengthened glass 2 and makes monochromatic light (visible light) enter the surface layer of the glass 2. The refractive index is made larger than that of glass 2.

Further, on the other end of the surface of the chemically strengthened glass 2, an emitting glass prism 3 is mounted as a light extraction member for emitting light propagated within the surface layer to the outside of the glass 2, and this prism Similarly to the prism 1, the refractive index of the glass 3 is larger than that of the chemically strengthened glass 2. Then, in the emission direction of the propagated light, two types of light are vibrated in parallel and perpendicular to the interface between the chemically strengthened glass surface 2 and the glass prism 3 for injection, that is, the emission surface 4. A light conversion member 5 is provided which separates the light into components and converts each of these light components into a bright line array. This light conversion member 5
is a convex lens 6 that focuses the propagating light on a focal plane, which will be described later, and selectively selects one of two types of light components that vibrate the light re-emitted from the convex lens 6 in parallel and perpendicular to the exit surface 4. It has a built-in rotatable polarizing plate 7 that allows light to pass through, and a focal plane 8 that shows the selectively transmitted light components as an array of bright lines.
an eyepiece micrometer 9 for observing the emission line array on the focal plane 8;
It consists of According to this configuration, when monochromatic light is made to enter the surface layer of the chemically strengthened glass 2 from the incident glass prism 1, within the surface layer, K+ ions are concentrated on the + surface and thinly distributed inside. , the K ion is Na
Since the polarizability force in response to the photoelectric field is lower than that of + ions, the refractive index is higher at the surface, so the monochromatic light is absorbed by silkworms in the surface layer of the chemically strengthened glass 2, as shown in FIG. While repeating the tower development and total reflection, the paths S, , S2,
..., propagates, and is ejected from the injection prism 3 to the outside of the glass 2.

In this way, in the process of monochromatic light propagating within the surface layer, the monochromatic light undergoes a birefringence phenomenon due to the photoelastic effect according to the compressive stress within the surface layer, and the light emitted from the exit prism 3 It has two types of light components vibrating parallel and perpendicular to 4. However, the propagating light emitted from the emitting glass prism 3 is guided to the light conversion member 5,
When the polarizing plate 7 of the member 5 is rotated, only one light component of the propagating light (for example, the light component vibrating perpendicularly to the exit surface 4) is directed to the focal plane 8 of the member 5. Diagram A
This appears as a line of bright lines consisting of L1...L, and this line of bright lines can be observed with the eyepiece micrometer 9. On the other hand, when the polarizing plate 7 is further rotated by 900 rotations, only the other light component of the propagating light (the light component vibrating parallel to the exit surface 4) appears on the focal plane 8 of the light conversion member 5. This appears as a bright line array consisting of L,'...L7' as shown in FIG. Of the light propagated within the surface layer of the chemically strengthened glass 2,
The difference (Δn) in the surface refractive index of the tempered glass for light having two types of light components passing through the path closest to the surface (S1 in Figure 2τ) is the difference (Δn) in the vertically vibrating light obtained by the device of the present invention. Lower emission line in the emission line array of the component (L, in Figure 3 A)
and the lower emission line in the emission line array of light components vibrating in parallel ′)
(L1' in Figure 3B) and (ΔL), and at the same time, the difference in surface refractive index (Δn) can be calculated as the magnitude of birefringence due to photoelasticity depending on the surface stress of chemically strengthened glass. Since they are correlated, the surface stress of the chemically strengthened glass can be measured by determining the difference (ΔL) between the bright lines L, , Ll'. Further, the thickness of the compressive stress layer in chemically strengthened glass can be easily measured from the number of bright lines in the obtained bright line array.

This is because the thicker the stress layer, the more types of light paths that can pass through it. Note that the light supply member and light extraction member used in the device of the present invention are not limited to the above embodiments, and may include, for example, a frame surrounding the surface of chemically strengthened glass;
A liquid of methylene iodide and promoform contained in the frame so as to be in contact with the glass surface;
good. Further, the positional relationship between the light supply member and the light extraction member used in the device of the present invention is not limited to the above embodiment, and each member may be arranged next to each other, for example.

As detailed above, according to the present invention, by utilizing the fact that the surface layer of chemically strengthened glass exhibits a light conduit effect, the surface stress of the glass and the thickness of the compressive stress layer are propagated through the surface layer. Since it can be easily measured from the difference (ΔL) between the lowest emission lines in each emission line array obtained from two types of light components of light and the number of emission lines in the emission line array, it exhibits various effects as listed below. can. (1) The surface stress of chemically strengthened glass and the thickness of the compressive stress layer can be measured non-destructively. There is no need to manufacture a thin section, and therefore the measurement work can be simplified and the measurement speed can be significantly increased.

(2) There is no need to cut or polish the chemically strengthened glass, and the chemically strengthened glass itself, which is not subject to external deformation, can be measured, making it possible to obtain measured values close to the true values.

(3) Since the surface stress of chemically strengthened glass can be measured from a bright line array that can be clearly and easily observed, there is no room for individual error in the measurement results, and stress can be measured with extremely high accuracy.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the surface stress measuring device for chemically strengthened glass according to the present invention, and FIG. 2 is a schematic diagram showing the propagation path of monochromatic light irradiated into the surface layer of chemically strengthened glass. Figures 3A and 3B are bright line arrays obtained by converting the two light components of the light emitted outside the chemically strengthened glass by the light conversion member, and Figure 3A is perpendicular to the exit surface. FIG. 3B is a characteristic diagram of an emission line array of a light component vibrating parallel to the exit surface. DESCRIPTION OF SYMBOLS 1... Glass prism for entrance, 2... Chemically strengthened glass, 3... Glass prism for injection, 5... Light conversion member, 7... Polarizing plate, 9... Eyepiece micrometer.

Claims (1)

[Claims] 1. A light supply member that allows monochromatic light to enter the surface layer of the chemically strengthened glass, a light extraction member that outputs the light propagated within the surface layer of the glass to the outside of the glass, and a light extraction member that allows the light emitted from the light extraction member to enter the surface layer of the glass. , comprising a light conversion member that separates into two types of light components vibrating parallel and perpendicular to the interface between the glass and the light extraction member and converts these light components into an array of bright lines, respectively. Surface stress measuring device for chemically strengthened glass.