JPS5914181B2 - Surface stress measurement method for air-cooled tempered glass - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for measuring the surface stress of air-cooled tempered glass obtained by air-cooling tempered glass obtained by the float method.

As is well known, in order to manufacture this type of air-cooled tempered glass,
After forming a plate glass by the so-called float method, in which molten glass is brought into contact with and moved onto a molten tin bath, this plate glass is heated to a temperature that softens it, and then quenched by blowing air to generate compressive stress on the surface and mechanically Methods have been adopted to improve strength.

However, the compressive stress generated on the surface of the air-cooled tempered glass obtained by this method is large, and the thicker the layer where compressive stress occurs, the greater its strength. Therefore, measuring the amount of compressive stress is important in determining quality. Important for management. By the way, the following method has conventionally been adopted to measure the surface stress of the above-mentioned air-cooled tempered glass.

(1) A method in which photoelasticity is measured using light that passes parallel to the surface of air-cooled tempered glass, and surface stress is determined based on this measured value.

(2) Utilizing light waves propagating on the surface of air-cooled tempered glass,
A method of determining the photoelastic effect as a function of propagation distance along the surface and calculating the photoelastic effect and surface stress per unit distance of the surface from this.

(3) Place a prism with a high refractive index on the surface of air-cooled tempered glass, let light enter the glass surface, and measure the critical angle by changing the angle of the incident light while observing the intensity of the light reflected by the surface, A method to find the difference in critical angle between extraordinary light and ordinary light. However, each of the above measurement methods has the following drawbacks and is not practical.

That is, in the method (c) above, only the average stress over a fairly wide surface of the air-cooled tempered glass can be measured, making it difficult to accurately measure the stress in a limited area of the glass.

Furthermore, since the value of the photoelastic effect to be measured is large in the case of large plate glass, the measurement itself becomes difficult. As an improvement measure,
It is possible to use a small sample piece cut from a large piece of air-cooled tempered glass, but when this air-cooled tempered glass is cut out, the glass breaks into small pieces and the stress is almost alleviated, making it impossible to measure the stress. becomes. Also, the above (
In the method 2), the intensity of the light propagating on the surface of the air-cooled tempered glass is generally weak, so it is substantially difficult to measure the stress. Furthermore, the method (3) above is
Although it is possible to measure stress more accurately than method 2), changes in the intensity of reflected light depending on the angle at the critical angle are often not clear due to factors such as the refractive index distribution near the surface of the air-cooled tempered glass. However, there is a disadvantage that surface stress cannot be measured all the time. For this reason, the inventors of the present invention have conducted extensive research to eliminate the above-mentioned drawbacks, and have found that when monochromatic light is incident on the surface layer of glass obtained by the float method, it is diffused near the surface of the glass. Due to the formation of a so-called refractive index gradient, in which the refractive index becomes higher as the surface approaches the surface due to the presence of incoming tin ions, the incident monochromatic light repeats the roofing phenomenon and total reflection within the surface layer, and propagates without being diverged to the outside. It was found that the so-called optical waveguide effect is exhibited.

However, before wind-cooling, float glass actually has no stress, that is, no photoelastic effect, and the refractive index distribution within the surface layer is composed of waves of light components vibrating parallel to the glass surface (
The same is true for waves of optical components vibrating perpendicular to the glass surface (hereinafter abbreviated as TM waves), and as a result, TE waves and TM waves have the same mode. Form. On the other hand, in air-cooled tempered glass, which is made by wind-strengthening float glass, a stress distribution of compressive force on the surface layer and tension on the inside occurs, and due to the photoelastic effect caused by this stress, birefringence occurs, and the surface The refractive index distribution within the layer is larger for TM waves than for TE waves by an amount proportional to stress,
Therefore, it has been determined that the surface stress of air-cooled tempered glass can be determined as a value proportional to the difference in refractive index. Based on the above research results, the inventors of the present invention have discovered that by making monochromatic light incident on the surface layer of air-cooled tempered glass and propagating it within the surface layer of the glass, the light having TE waves and TM waves after propagation can be transmitted through the glass, for example. Inject it to the outside with a prism and separate it into TE waves and TM waves,
Convert these TE waves and TM waves into dark line arrays (or bright line arrays), and find the difference between the dark lines that propagated along the path closest to the surface of the wind-cooled tempered glass in each dark line array (or the bright line off the coast of Yokohama). As a result, we have discovered a method that can measure the regional (local) surface stress of large-sized air-cooled tempered glass extremely quickly and with high precision.

That is, in the method of the present invention, glass obtained by the float method is air-cooled strengthened, and in order to measure the surface stress of the air-cooled tempered glass, monochromatic light is incident into the surface layer of the air-cooled tempered glass. The light propagates through the surface layer of the glass, and the light after propagation is emitted to the outside and separated into two types of light components that vibrate parallel and perpendicular to the glass surface from which they are emitted. The method is characterized in that the surface stress of the air-cooled tempered glass is measured based on the dark line array or the bright line array.

Monochromatic light in the present invention is light obtained using, for example, a spectral lamp or a laser device as a light source. In the present invention, a glass prism or a frame containing a liquid such as methylene iodide or promoform is used for inputting and outputting monochromatic light, and these members have a refractive index that is equal to that of air-cooled tempered glass. Designed to be larger.

Note that the monochromatic light input member and output member may be separated, or may be integrated via a shielding film as the case may be. Next, embodiments of the present invention will be described with reference to the drawings.

Embodiment FIG. 1 is a schematic diagram of the surface stress measuring device used in this embodiment. In the figure, 1 is a surface stress measuring device with a fixed gap formed on the upper surface of the air-cooled tempered glass 2 via screws 3, 3 as vertical adjustment legs. A horizontally movable light source 4 is provided on this pedestal 1.

This light source 4 is composed of an outer tube 6 having an entrance hole 5 for monochromatic light, and a spectral lamp 7 housed within the outer tube 6. Further, an incident glass prism 8 for making monochromatic light from the light source 4 enter into the surface layer of the glass 2 is supported on the pedestal 1 so as to be horizontally movable and rotatable via a shaft 9. Furthermore, the mount 1 is provided with a light component wave (TE wave) that vibrates horizontally to the surface of the glass 2 and a wave (TE wave) of the light component that vibrates perpendicularly to the surface of the glass 2 to the outside of the glass 2. An emitting glass prism 10 that separates and emits light component waves (TM waves) is supported via a shaft 11 so as to be horizontally movable and rotatable. Note that each of the prisms 8 and 10 has a refractive index larger than that of the air-cooled tempered glass 2. A light converting member 12 is disposed on the mount 1 in the direction of emission of the TE waves and TM waves emitted from the glass prism 10 for injection, and converts the TE waves and TM waves into a dark line array or a bright line array, respectively. movably supported. This light conversion member 12 includes an objective lens 13 that collects the TE waves and TM waves from the glass prism 10 for ejection onto a focal plane, which will be described later, and one of the TE waves and TM waves re-emitted from the objective lens 13. A rotatable polarizing plate 14 that selectively transmits only the T
It is composed of a focal plane 15 that displays E waves or TM waves as a dark line array, and an eyepiece micrometer 16 that incorporates this focal plane 15 and is used to observe the dark line array on the focal plane 15. First, two sheets of plate glass obtained by the float method are used as air-cooled tempered glass.
A 5 mTn x 25 mm specimen was softened by heating at a temperature in the range of 6002 to 690°C and quenched by air blowing, and monochromatic light from the light source 4 was introduced into the surface layer of the air-cooled tempered glass 2 through a glass prism for incidence. 8. As shown in FIG. 2, the incident monochromatic light undergoes birefringence on the surface layer of the air-cooled tempered glass 2 due to the photoelastic effect corresponding to its compressive stress, and repeats the lip louver phenomenon and total reflection to pass through the path Sl. , S2... and the propagation progresses. Next, when the monochromatic light that has propagated through the surface layer of the air-cooled tempered glass 2 is emitted to the outside by the emitting glass prism 10,
As shown in FIG. 3, a light component wave 18 (TE wave) vibrates parallel to the interface (exit surface 17) between the air-cooled tempered glass 2 and the glass prism 10 for injection, and a light component wave 19 vibrates perpendicularly to the boundary surface (exit surface 17). (TM wave). Next, the TE wave 18 and the TM wave 19 are emitted from the emitting glass prism 8 and separated.
When the polarizing plate 14 of the member 12 is rotated, one of the TE wave 18 and the TM wave 19 (
For example, only the TM waves 19) are present at the focal plane 15 of the member 12.
A dark line array consisting of L1 . . . L7 as shown in FIG. On the other hand, when the polarizing plate 14 is further rotated 90 degrees, only the TE wave 18, which is the wave of the other light component, appears on the focal plane 15 of the light conversion member 12 as shown in FIG. This dark line array was observed with an eyepiece micrometer 16. Therefore, the lower dark line (L1) in the dark line array L1...L7 due to the TM wave 19 obtained in this example, and the lower dark line (L1) in the dark line array L1ζ...L7' due to the TE wave 18.
The difference (ΔL) from 1 Difference in surface refractive index (Δn) of air-cooled tempered glass for light with waves (TE waves, TM waves)
), and at the same time, this difference in surface refractive index (Δn) is correlated with the magnitude of birefringence due to the photoelastic effect according to the surface stress of the air-cooled tempered glass, so each of the dark lines Ll, L
The surface stress of the air-cooled tempered glass was measured by determining the difference in l7 (ΔL).

As a result, it was confirmed that the obtained measured value of surface stress was a regional (local) value of the large-sized air-cooled tempered glass, and its accuracy was also extremely high. On the other hand,
The surface stress measurement value obtained by the photoelastic measurement method (comparative example) by passing light parallel to the surface of a test piece of air-cooled tempered glass similar to the above example is the value of the surface stress of the entire glass. It was an average value, and local measurement was difficult. In addition, in the comparative example, a small test piece (25mm x 2571tm)
Although it is possible to measure the surface stress with relatively high accuracy, it has been found that as the size increases, it becomes difficult to accurately measure the surface stress due to the increased photoelastic effect. As detailed above, according to the present invention, by utilizing the fact that the surface layer of air-cooled tempered glass obtained by wind-strengthening glass obtained by the float method exhibits an optical waveguide effect, local The respective dark line arrays obtained from the two types of optical component waves (TE waves and TM waves) of the light propagated through the surface layer of the glass can be easily measured based on the bright line arrays, and the surface stress can be easily measured based on the bright line arrays. It has remarkable effects such as being able to measure the surface stress of air-cooled tempered glass non-destructively, quickly, with high precision, and always stably.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing one form of the surface stress measurement device for air-cooled tempered glass used in the examples of the present invention, and Fig. 2 is the propagation path of monochromatic light incident on the surface layer of the air-cooled tempered glass. 3 is a schematic diagram showing a state in which light propagated within the surface layer of air-cooled tempered glass is separated and emitted from the exit glass prism as two light component waves (TE wave, TM wave), Figures 4A and 4B are dark line arrays obtained by converting two types of light component waves (TE waves and TM waves) of light emitted outside the air-cooled tempered glass using a light conversion member. , FIG. 4a is a dark line characteristic diagram of the TM wave, and FIG. 4b is a dark line characteristic diagram of the TE wave. 1... Frame, 2... Air-cooled tempered glass,
4...Light source, 8...Glass prism for human emission, 10...Glass prism for emission, 12.
...Light conversion member, 14 ...Polarizing plate, 16
・・・・・・Ocular meter, 18・・・TE wave, 1
9...TM wave.

Claims (1)

[Claims] 1. To air-strengthen glass obtained by the float method and measure the surface stress of the air-cooled tempered glass, monochromatic light is incident on the surface layer of the air-cooled tempered glass to propagate, emit the propagated light to the outside, separate it into double light components vibrating parallel and perpendicular to the emitted glass surface, and then convert these light components into a dark line array or a bright line array, respectively, A method for measuring the surface stress of air-cooled tempered glass, which comprises measuring the surface stress of the air-cooled tempered glass based on these dark line arrays or bright line arrays.