JPS608726B2 - Device for measuring the thickness of metal or metal oxide coatings applied to the surface of glass, etc. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for measuring the thickness of a metal or metal oxide coating applied to the surface of glass, etc., and particularly to a device for measuring the thickness of a metal or metal oxide coating applied to the surface of a glass bottle, such as a tin oxide coating applied to the surface of a glass bottle. The present invention relates to a device suitable for measuring the thickness of a metallic oxide film.

A widely used method is to form a metallic oxide film such as Sn02 (stannic oxide) or Ti02 on the surface of a glass bottle in order to provide smoothness to the surface of the glass bottle and prevent scratches caused by contact between glass bottles. ing.

To form a Sn02 film on the surface of a glass bottle, apply Sn02 to the surface of the glass bottle when it is in a high temperature state immediately after molding.
A method of contacting the vapor of a metal compound such as C14 is used. SnC14 reacts with oxygen in water vapor to form Sn0
2 particles and adhere to the glass surface in a layered manner. If this film is too thin, it will not be effective in preventing scratches, and if it is too thick, the surface of the bottle will shine in rainbow colors due to light interference, reducing the product value of the pin.
The thickness of the coating is 30 to 50 angst.

preferably within the range of For this reason, a few coating thickness measuring devices have been developed so far. A typical conventional measurement device immerses a glass bottle in a liquid such as monochlorobenzene that has almost the same refractive index as glass, projects visible light, and measures the film thickness based on the amount of reflected light. It is something.

Other devices have also been developed that use reflection of infrared rays instead of visible light, but in all of these devices, the glass bottle is coated with monochrome benzene to eliminate the effects of reflection that occur at the interface between glass and air. It is necessary to immerse the pin in liquid such as liquid, and if this is to be applied to 100% inspection of bottles, a process to remove the liquid adhering to the surface of the pin is required, which increases running costs and makes it impractical. There was a problem with how to do it. Other things. Clobenzene is volatile and its use in large quantities poses hygiene problems, so these conventional devices could only be used for spot checks. The present invention has been made in order to provide a new measuring device which solves the above-mentioned drawbacks of the prior art. An object of the present invention is to provide a device for measuring the thickness of applied metal or metal oxide coatings.

Another object of the present invention is to provide an apparatus that can measure the thickness of the coating without contact. The gist of the present invention, which has been made to achieve these objects, is as follows:
A light projection means for projecting linearly polarized light vibrating parallel to the plane of incidence at a Brewster's angle determined by the refractive index of the glass onto a surface of glass having a metal or metal oxide coating on the surface, and a light projection means placed in the reflected optical path. The present invention relates to an apparatus for measuring the thickness of a metal or metal oxide coating applied to a surface of glass or the like, characterized by comprising a photoelectric conversion means with a photoelectric conversion means. It is known that when natural light (ordinary light) is incident on the surface of glass or the like at a specific angle of 0, the reflected light becomes pure linearly polarized light that vibrates perpendicular to the plane of incidence.

If the refractive index of the substance at this angle is n, then n8
is given by This is called Brewster's Law, and 8 is called Blue Star's Law. It is also known that such a polarization phenomenon does not occur on the surface of metal or metal oxide. Natural light here means light that equally contains linearly polarized light that vibrates in all directions.

Among these linearly polarized light components, the polarized light component that vibrates parallel to the plane of incidence is completely absorbed by the surface of glass etc. and is not reflected. If the light is projected onto a surface such as glass at a star angle, the reflected light will be zero. Furthermore, since the surface of metal or metal oxide reflects incident light regardless of the direction of vibration, if there is a coating of metal or metal oxide on the surface of glass or the like, reflected light will occur. The present invention was made based on the above findings, and by projecting linearly polarized light vibrating parallel to the incident plane at the Brewster angle, the surface of a metal or metal oxide coating applied to the surface of glass, etc. The purpose is to generate reflected light only from the surface and determine the thickness of the coating based on the amount of light.

The present invention will be explained in more detail below according to Examples. FIG. 1 is a front view of the apparatus of the embodiment.

A glass bottle 1 whose surface is coated with SN02 is transported by a star wheel 2 to an inspection position, where it is rotated about an axis by a roller 3 and a drive roller (not shown). At the inspection position, a laser oscillator 4,
A light projecting means 6 consisting of a polarizing plate 5 and a chopper 7 is provided, and the light projecting means 6 is provided with an incident angle a on the surface of the glass bottle I as shown in the figure.
The laser beam is projected so that is Brewster's angle. The laser beam is natural light as defined above, and is not polarized in a specific direction, so the polarizing plate 5 converts it into linearly polarized light that vibrates parallel to the plane of incidence. A laser beam is most suitable as a light source for use in the present invention because it is a nearly perfectly parallel beam. The chopper 7 is a disc that is rotated at a constant speed by a motor 8, and a large number of holes are provided at regular intervals on the green part of the periphery. The chopper converts the laser beam into intermittent light of a constant frequency, and by amplifying only the beam of that frequency on the receiving side, disturbances caused by other beams can be prevented. If the glass bottle 1 is made of ordinary soda-lime glass, its refractive index is approximately 1.52.

At this time, the Brewster angle is 56.6o. In practice, it is not necessary to strictly match the Brewster's angle, and measurements can be made without major problems as long as it is within a range of about plus or minus 100. For the above-mentioned reason, if there is no Sn02 coating on the surface of the glass bottle, no reflected light will be generated, and therefore no output will be generated even if the light exchange means 10 is placed in this reflected optical path.

However, if the surface of the glass bottle is covered with a Sn02 coating, the projected laser beam will be reflected from the surface and produce an output from the photoelectric conversion means. results of the experiment,
It was found that there is a relationship as shown in FIG. 2 between the thickness of the Sn02 film and the output of the photoelectric conversion means 10. By utilizing this relationship, the thickness of the Sn02 coating can be measured. Although it is not necessarily clear why the amount of reflected light changes depending on the thickness of the Sn02 film,
According to the inventor's speculation, the following explanation seems possible.

That is, it is thought that Sn02 adheres to the glass surface in the form of fine particles, and these particles overlap in many layers to form a Sn02 coating. Therefore, a portion of the laser beam projected onto the surface of the Sn02 coating is reflected by the Sn02 particles in the surface layer, and a portion of the laser beam passes through the Sn02 particles, hits the Sn02 particles below, and is reflected by the surface.
Furthermore, some light rays pass through the particles and reach the surface of the Sn02 particles below. Also, part of the laser beam is Sn
The light may reach the glass surface directly through the gaps between the 02 particles, where reflection may occur. As mentioned above, the laser beam is polarized light that vibrates parallel to the plane of incidence, so the laser beam that passes through two S particles and reaches the glass surface, or the S
The particles that directly reach the glass surface from the gaps between the n02 particles are absorbed by the glass surface and do not cause reflection. Therefore,
It is thought that only the light reflected from the surface of the SnQ particles becomes reflected light, and the thicker the SN02 coating, the greater the probability that it will be reflected from the surface of the Sn02 particles before reaching the glass surface, and the amount of reflected light will increase. It will be done. In the embodiment, the output of the photoelectric conversion means 10 is amplified by the amplifier 11 and inputted to the pass/fail determining circuit 12, and the glass pins determined to be defective are removed from the line by the rejecting device 13.

However, when used simply as a measuring device, the output of the photoelectric conversion means 10 may be displayed on a suitable display device. In the apparatus of the embodiment, the measurement is performed while rotating the glass bottle, so the thickness of the coating can be measured over the entire circumference. As explained above, the device of the present invention uses Brewster's law to eliminate reflected light from the surface of a substrate such as glass, and only removes reflected light from the metal or oxidized metal surface, which varies depending on the thickness of the coating. By using photoelectric conversion means, it is possible to accurately measure the thickness of these coatings.

Furthermore, according to the present invention, there is no need to consider reflected light at the interface between glass and air, so there is no need to immerse a glass bottle or the like in the liquid as in conventional devices, making measurements easier. Became. Further, according to the present invention, the thickness of the coating can be measured without contact, which is convenient for on-line measurement and inspection of a large number of glass pins. The above explanation has focused on measuring the thickness of the Sn02 coating on the surface of a glass bottle, but the present invention is not limited to this, but can also be applied to measuring the thickness of metal or metal oxide coatings formed on the surfaces of ceramics, plastics, etc. It is also possible to apply

[Brief explanation of drawings]

FIG. 1 is a front view of the device of the example, and FIG. 2 is a front view of the device of the example.
2 is a graph showing the relationship between the thickness of the coating and the output of the photoelectric conversion means. 1... Glass bottle, 4... Laser oscillator, 5... Polarizing plate, 10... Photoelectric conversion means. Poly/acid polyz diagram

Claims (1)

[Scope of Claims] 1. Light projecting means for projecting linearly polarized light vibrating parallel to the plane of incidence at a Brewster's angle determined by the refractive index of the glass, etc. onto the surface of glass, etc. having a metal or metal oxide coating on the surface. and a photoelectric conversion means placed in the reflected optical path. 2. The device according to claim 1, wherein the light projecting means includes a laser oscillator and a chopper.