JPH01118755A - Method for diagnosing coating film deterioration with laser beam - Google Patents

Abstract

PURPOSE:To diagnose the degree of deterioration of the coating film of a building, etc., quantitatively without any destruction by irradiating the coating film with a laser beam having specific wavelength, measuring its reflected light, and diagnosing the degree of deterioration of the coating film from the detected value. CONSTITUTION:When a laser driving power source 2 is turned on, a variable wavelength laser device 3 emits a variable-wavelength laser beam, which is projected on the coating film 1 at a specific position through a convergence optical system 4. The projected light is reflected by the surface of the coating film 1 at an angle theta2 of reflection matching with its angle theta1 of incidence, and the light is passed through the convergence optical system 5; and a detector 6 detects the intensity of the laser beam and the intensity of the reflected light with the wavelength is detected by an X-Y recorder 8 through an amplifier 7. Then if the coating film 1 deteriorates, resin constituting the resin film 1 reacts on ultraviolet rays, etc., and is decomposed to change in its molecular structure, thereby obtaining the light intensity corresponding to the degree of its deterioration. The degree of the deterioration is therefore found from the reflected light intensity and incident light intensity.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for diagnosing the degree of deterioration of a coating film on a structure such as a wooden beam, and in particular, uses a laser beam. The present invention relates to a method for diagnosing paint film deterioration.

[Conventional technology] The paint films of structures such as Fukuliang are exposed to sunlight, wind and rain, which can cause them to peel off or fade.
This needs to be inspected regularly.

, conventionally, for example? ! Scaffolding was erected around the beams, and workers were performing various maintenance tasks and inspecting the coating.

[Problems to be Solved by the Invention] However, even if the state of the paint film is visually inspected, it is difficult to determine the extent to which the deterioration of the paint film has progressed. There are various problems such as the need to erect scaffolding for this purpose.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for diagnosing paint film deterioration using a laser beam, which allows more accurate diagnosis of paint film deterioration in a non-contact manner.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention irradiates a coating film of a building etc. with a laser beam of a specific wavelength, measures the reflected light, and uses the detected value to determine the coating film. This is designed to diagnose membrane deterioration.

[Function] Generally, the deterioration of a coating film progresses as the resin (or color vehicle) constituting the coating film is decomposed by the action of external radiation, oxygen, etc.

The molecular structure of these resins changes as they decompose, so the degree of deterioration can be detected by detecting the specific molecular structure that appears or is lost due to deterioration using the absorption spectrum of an infrared laser beam. In other words, if a paint film is irradiated with a laser beam of a specific wavelength and deterioration progresses, the absorbance at that wavelength will change (larger or smaller), so if you look at the change in absorbance over time, you can tell the degree of deterioration. The degree of progression can be diagnosed.

[Embodiments] Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, 1 is a painted surface of a building such as a bridge, 2 is a laser driving power source, and 3 is a variable wavelength laser device consisting of an infrared diode, which outputs a laser beam with a transmission wavelength of 2 to 12 μm. Reference numeral 4 denotes a condensing optical system on the light projecting side, which guides a laser beam cutter to irradiate a predetermined location on the coating surface 1 with the laser beam from the variable wavelength laser beam device 3. 5 is a condensing optical system for condensing the laser beam IL* reflected from the coating surface 1, and 6 is a laser beam L+e from the optical system 5.
7 is an amplifier for the detection signal from the detector 6, and 8 is an X-Y recorder for recording absorbance with respect to wavelength.

First, the laser drive ON source 2 is turned on to emit a variable wavelength laser beam, and the laser beam Lx is irradiated from the condensing optical system 4 to a predetermined location on the coating surface 1.

Upon irradiation, the laser beam L4 is reflected on the surface of the coating M1 at a reflection angle Q8 commensurate with the incident angle QX, and the light intensity of the laser beam L4 is detected by the detector 6 via the condensing optical system 5. The Y recorder 8 detects the intensity of the reflected light at that wavelength.

When the coating film 1 deteriorates, the resin (or color vehicle) constituting the coating film 1 reacts with ultraviolet rays, oxygen, etc. and decomposes, changing its molecular structure and structure. For example, if the coating film 1 is made of epoxy resin or the like, the double bonds of the benzene nuclei are broken by oxygen to form quinoids.

Since this quinoid-formed molecule has an absorption band at 1650 cm, the coating film 1 is irradiated with the laser beam LZ at a wavelength that allows detection of the absorption band.

As a result of this irradiation, the laser beam is absorbed according to the concentration of quinoid molecules in the coating film 1, so that the reflected laser beam LP has a light intensity that corresponds to the concentration of the quinoid molecules, that is, the degree of deterioration.

In addition, since the intensity of the reflected light varies depending on the distance between the condensing optical system 4.5 and the coating film 1 and the weather conditions at the time of measurement, the intensity of the incident light is measured in advance under the same conditions as a reference, and the reflected light The absorbance (degree of deterioration) is determined from the intensity ■ and the incident light intensity ■0.

This will be explained with reference to FIGS. 2 to 4.

First, as shown in FIG. 2, the incident light intensity ■0 and the reflected light intensity ■ are determined.

These light intensities are determined by Beer-Lambert's law, where k
is the extinction coefficient determined by the substance, and C is m.

Therefore, the logarithmic ratio of the above-mentioned incident light intensity 1o and reflected light intensity I (
Iog1o/I) is determined as shown in FIG. 3, and the concentration of the degraded product is determined from that value.

In addition, since the degree of deterioration of the coating film 1 gradually increases over time as shown in Fig. 4, depending on the type of the coating film 1,
The degree of deterioration corresponding to the concentration of the deteriorating substance is determined by experiment, and the degree of deterioration is determined based on this.

[Effects of the Invention] As is clear from the above explanation, the present invention exhibits the following excellent effects.

(1) The degree of deterioration of the paint film can be diagnosed by irradiating the paint film with a specific laser beam that can detect the degree of deterioration of the paint film and detecting the reflected light.

(D) Paint film deterioration can be diagnosed non-destructively and quantitatively.

[Brief explanation of the drawing]

Figure gJ41 is a diagram showing an example of an apparatus for carrying out the method of the present invention, Figures 2 and 3 are diagrams showing absorption spectra in the present invention, and Figure 4 is a diagram showing changes in the degree of deterioration over time. In the figure, 3 is a wavelength changing laser device, 4.5 is a condensing optical system, and 6 is a detector. Patent applicant: Patent attorney representing Ishikawajima-Harima Heavy Industries Co., Ltd.
Nobuo KinutaniLl, LR--loop ring formation. Decay length - (cm-') Figure 2

Claims (1)

[Claims] A laser beam of a specific wavelength is irradiated onto the paint film of buildings, etc.
A method for diagnosing paint film deterioration using a laser beam, characterized by measuring the reflected light and diagnosing paint film deterioration based on the detected value.