JPS6352550B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method and apparatus for managing variations in the adhesion strength of a coating film formed by coating with plasma pretreatment in order to improve the adhesion of the coating film, particularly to olefinic resins. Conventionally, in microwave plasma processing equipment used for this type of equipment, plasma generation parameters are set in advance to generate a predetermined amount of plasma, and the treatment effect is determined by the contact angle of water droplets on the object to be treated and the coating film after painting. This was confirmed later based on adhesion (peel) strength. For example, in the microwave plasma processing apparatus shown in FIG. 1 (described later), the microwave oscillator 1
output and oscillation time, the type and flow rate of the processing gas in the gas cylinder 6, and the degree of vacuum in the reaction chamber 13,
These are parameters that define the amount of plasma generated, and these can be monitored using the power monitor 3, gas flow meter 7, and vacuum gauge (not shown), but this is not only complicated, but also allows for monitoring fluctuations in the amount of plasma generated during plasma processing. It was difficult to detect accurately. Therefore, the present invention provides a coating film that can easily and reliably prevent fluctuations such as a reduction in coating film adhesion strength caused by fluctuations in the amount of plasma generated in a microwave plasma processing device when painting using the method described at the beginning. An object of the present invention is to provide a bond strength management method and device. The present invention also provides coating film adhesion strength,
That is, based on the confirmation that there is a correlation between the amount of plasma generated and the phenomenon of plasma light emission, the above object was achieved by monitoring the emission spectrum intensity or amount of light emission of the plasma during plasma processing and detecting its fluctuations. FIG. 1 shows an apparatus for experimentally confirming the correlation between the relative spectral intensity and coating adhesion strength in such plasma emission. That is, 1 is a microwave oscillator, 2 is an isolator, 3 is a power monitor, 4 is a matching device, 6 is a gas cylinder filled with processing gas, 7 is a gas flow meter, and 10 is supplied through the waveguide 5. A plasma generation furnace that generates microwave plasma by adding microwaves to the processing gas supplied through a pipe 8, 11 a quartz tube that transmits the microwave plasma, 12 a Teflon joint, and 13 a vacuum pump that passes through an exhaust port 14. A reaction chamber 15 is evacuated by a vacuum cleaner (not shown), and a plasma irradiation tube 15 irradiates the object to be treated with plasma in the reaction chamber 13 . Such plasma processing apparatuses 1-8, 10-1
5 itself is the same as before, but an optical fiber 1 is attached to the quartz tube 11 of this device to send the plasma emission to a spectral intensity measuring device 18 that displays the plasma emission as a spectral relative intensity after spectroscopy.
7 is installed. On the other hand, a test piece to be coated after plasma treatment and to measure the strength of the coating film is manufactured as follows. That is, the polypropylene flat plate molded product 22 was first suspended in a trichloroethane vapor bath for cleaning, exposed for 2 minutes, then lifted and dried, and then subjected to plasma treatment under various conditions using the apparatus shown in FIG. Let's do it. Next, urethane paint was applied to a thickness of 50 μm and dried at 120°C for 30 minutes to form a coating film 20 on the flat molded product 22, and the central part was cut out into a rectangular shape of 50 x 10 mm. do. To test the coating film adhesion strength of the test piece 23 manufactured in this way, as shown in FIG. After sandwiching it in a sandwich shape, the coating film 20
The flat plate molded part 22a from which the peeled part 22a and the cellophane tape 21 were fixed to the chuck of a tensile tester, and the test was carried out at a tensile speed of 50 mm/min. Next, the above-mentioned plasma processing apparatuses 1 to 8, 10 to
Experimental results of the correlation between the relative spectral intensity of plasma emission and the coating film adhesion strength, which were confirmed by the intensity test method for the above-mentioned test piece 23 and 15 and plasma emission spectral intensity measuring device 18, will be explained. Prior to the plasma treatment of the polypropylene flat plate molded product 22, in order to confirm the reproducibility of the emission spectrum, the processing gas was dry air at a constant flow rate, the output power of the microwave oscillator 1 was 1 kW, and the vacuum degree of the reaction chamber 13 was 1 Torr and 4 Torr. The emission spectrum was measured twice (Fig. 3 a, b, Fig. 4 a,
b). And from the emission spectrum, the wavelength is 320nm,
Spectra with maximum values near 345 nm, 360 nm, 600 nm, and 670 nm were selected, and the relative intensity of the emission spectra was determined by the baseline method (Table 1).

[Table] As a result, the difference in the relative intensity of the emission spectrum at each wavelength between the first and second times is 0 to 5.8%,
It can be seen that good reproducibility is obtained and that the emission spectrum exhibits a constant relative intensity under a given input system setting. In order to confirm the correlation between the relative intensity of the emission spectrum and the adhesion strength of the coating film, a polypropylene flat plate molded product 22 that had been subjected to torchloroethane steam cleaning was subjected to microwave output: 1 KW, processing time: 30 seconds,
Under the conditions of process gas: dry air, the degree of vacuum in the reaction chamber 13 was varied to 0.5, 1, 4, and 8 Torr, and the relative intensities of the emission spectra shown in FIGS. 5a to 5d were first measured. Table 2 shows the relative intensities of the maximum emission spectra around wavelengths 320, 345, 360, 600 and 670 nm that exhibit peaks at each degree of vacuum in this measurement, and the coating films corresponding to these plasma emission states conducted using the method described above. Adhesion strength test results are also listed.

[Table] Figures 6a, b, and c show the correlation between the maximum relative intensity of the emission spectrum near wavelengths of 320, 345, and 360 nm and the coating film adhesion strength based on these measurement and test results. From the relationship shown in Figure 6, the relative intensity of the emission spectrum in the ultraviolet region is 0.08~
It can be seen that the coating film adhesion strength becomes constant above 0.14, and decreases rapidly below it. Similarly, FIGS. 7a and 7b show the correlation with the maximum emission spectra around 600 and 670 nm. From the relationship shown in FIG. 7, it can be seen that in the visible region, the relative intensity reaches approximately 0, rapidly increases above it, and becomes constant. By monitoring the relative intensity of the emission spectrum for a specific wavelength from the relative relationship between the relative intensity of the plasma emission spectrum and the coating film adhesion strength confirmed as above, and monitoring its fluctuation from the reference level, it is possible to determine the coating film adhesion strength. It turns out that fluctuations can be detected. Also,
Since a change in the relative intensity of the emission spectrum corresponds to a change in the absolute value of the intensity of the emission spectrum, the absolute intensity may be measured. As can be seen from Figure 5, the fluctuations in the relative intensity of the emission spectra vary at the same rate over the entire emission wavelength range, so it is possible to integrate the relative intensity of each emission spectrum without having to deliberately select the wavelength to be monitored. It is sufficient to measure the value or the total amount of light emission over a certain wavelength range. Next, an apparatus for carrying out the method according to the invention will be described. In FIG. 8, 30 indicates a specific wavelength, for example, from the emission spectrum intensity measuring device 18 of FIG.
A holding circuit that holds the maximum emission spectrum intensity signal in the vicinity of 320 nm in an analog manner, 31 is the relative intensity of the emission spectrum that can reliably maintain the coating adhesion strength of the object to be coated at a constant level, and holds it from a reference level corresponding to, for example, 0.15. A comparator 32 detects a downward change in the output signal of the circuit 30, and a warning device 32 is activated by the output signal of the comparator to issue an acoustic or optical alarm. That is, the comparator 31 monitors the output signal of the holding circuit 30 following the emission spectrum intensity measuring device 18 as a plasma luminescence measuring device, and when the signal falls below a reference level, the alarm 32 issues an alarm, thereby detecting plasma generation. Abnormal reductions in the amount of plasma can be detected, and abnormalities in the plasma processing equipment can be immediately checked. If a light intensity measuring device is configured with a microcomputer equipped with an A/D converter on the input side and a D/A converter on the output side instead of the holding circuit 30 and the spectral intensity measuring device 18, it is possible to integrate the emission spectrum intensity in a specific wavelength range. It becomes possible to compare the value, or the average or integral value for multiple wavelength ranges, with a reference level. Furthermore, the reference level is set to correspond to the arbitrary coating film adhesion strength in the rising region in Figure 6a, and the comparator detects that the emission spectrum intensity signal fluctuates by a predetermined amount in the direction of increase or decrease from this reference level. If you let
Adhesive strength can be controlled within any desired range. In FIG. 9, the optical fiber 17 of FIG.
A photoelectric conversion circuit 3 serves as a plasma luminescence measurement device that outputs an electrical signal at a level corresponding to the amount of incident light.
5. Comparator 36 and alarm 37 follow.
In this case, by measuring the correlation between the output signal level of the photoelectric conversion circuit 35 and the coating film adhesion strength in advance and setting the reference level of the comparator 36 according to the result, the spectral intensity can be adjusted. Measurement is not required, making the device simple and inexpensive. It is also possible to perform servo control to keep the emission spectrum intensity or emission amount constant by feedback-controlling an error signal with respect to a reference level of the emission spectrum intensity or emission amount to an input parameter system that sets the plasma generation amount. As described above, by monitoring the fluctuations in plasma emission spectrum intensity or luminescence amount when implementing a coating method involving microwave plasma pretreatment according to the present invention, it is possible to easily reduce the adhesion strength of a coating film caused by fluctuations in the amount of plasma generation. It becomes possible to manage the coating film adhesion strength to reliably prevent deterioration or ensure the desired adhesion strength with precision. That is, abnormalities in plasma processing can be detected with high reliability during processing, and defects in the object to be processed can be reliably prevented. Furthermore, if necessary, it becomes possible to automatically control the plasma generator based on the adhesion strength.

[Brief explanation of the drawing]

FIG. 1 shows the schematic configuration of a plasma processing apparatus and a plasma emission spectrum measuring apparatus according to the present invention, and FIG.
The figure is an explanatory diagram of the method for testing the adhesion strength of a painted specimen after plasma treatment using the apparatus shown in Fig. 1, and Figs. 3 and 4 show the relative intensity of the emission spectrum of the plasma generated by the apparatus shown in Fig. 1. Figure 5 shows the measurement results of the relative intensity of the plasma emission spectrum when varying the degree of vacuum in the reaction chamber of the apparatus shown in Figure 1.
7 and 7 show the experimental results of the correlation between the relative intensity of the emission spectrum of the plasma and the coating adhesion strength, and FIGS. 8 and 9 show the apparatus for carrying out the method according to the invention. 1...Microwave oscillator, 6...Gas cylinder, 10
...Plasma generation furnace, 17...Optical fiber, 13...Reaction chamber, 14...Exhaust port.

Claims (1)

[Scope of Claims] 1. In a method for managing adhesion strength fluctuations of a coating film on an object to be coated formed by coating with microwave plasma pre-treatment, an emission spectrum of plasma for treating an object to be coated with microwave plasma A method characterized by monitoring the intensity or amount of luminescence, and detecting changes in coating film adhesion strength based on fluctuations in the emission spectrum intensity or amount of luminescence. 2. A plasma generating furnace that generates microwave plasma by being supplied with processing gas and microwaves, and a vacuum reaction chamber that stores the object to be coated, is installed to control the emission spectrum intensity or luminescence of microwave plasma. a plasma luminescence measuring device for measuring the amount of light emitted from the plasma; An apparatus for controlling adhesion strength of a coating film in a coating method involving plasma pretreatment, characterized by comprising an alarm activated by a detection signal of the comparator.