JPS6344965A - Formation of multilayer film - Google Patents

Abstract

PURPOSE:To enhance the interlaminar adherence of a multilayer film by a simple process, in applying under coat and top coat to an article to be coated by overlap coating, by applying low temp. plasma treatment to the surface of a primer film. CONSTITUTION:As a low temp. plasma atmosphere, high frequency glow discharge generated under a reduced pressure of about 0.1-10torr by high frequency discharge of a frequency of about 10<3>-10<21>Hz or corona discharge generated under atmospheric pressure or reduced pressure under such a condition that power source voltage is 10-50kV and frequency is 1-100kHz are utilized. For example, at the time of high frequency glow discharge using RF as high frequency, the internal pressure of a bell jar is adjusted to predetermined gas pressure and a RF power source 5 is operated to apply RF to an exciting electrode 2 and the gas present between said electrode 2 and an opposed electrode 3 is excited to generate a low temp. plasma atmosphere 8. The an active species generated as a result attacks the surface of a primer film 6 to form a functional group contributing to the adherence of a top coat film.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a method for forming multilayer coatings.

[Background technology]

For example, when applying a base paint and a second coat of paint to an object to be coated, if the adhesion between the two is not sufficient, there is a risk of peeling between the eyebrows. Therefore, conventionally, the surface of the base coat is modified by some method before the top coat is applied.

Methods for modifying the surface of the base coating include, for example, chemical treatment methods using acids, alkalis, etc., methods of treatment by irradiation with ultraviolet rays, methods of treatment using flames, and the like.

However, chemical treatment methods using acids, alkalis, etc. require wet processes such as cleaning and drying, which complicates the process and poses problems such as disposal of waste liquid.

The method of treating by irradiating ultraviolet rays is not effective for treating objects with complicated shapes because the ultraviolet rays travel in a straight line.

According to the method of treatment using flame, the base coat is exposed to high temperatures, so there are problems such as restrictions on the type of paint that can be used for the base coat, the shape of the object to be coated, and the processing time. be.

[Purpose of the invention]

This invention was made in view of the above problems; the process is simple, there is no need to dispose of waste liquid, and it also eliminates restrictions such as the shape of the object to be coated, the type of base coating, and the processing time. The object of the present invention is to provide a method for obtaining a multilayer coating film with excellent interlayer adhesion without being damaged.

[Disclosure of the invention]

In order to achieve the following objects, the gist of the present invention is a method for forming a multilayer coating film, in which the surface of the base coating film is subjected to low-temperature plasma treatment, and then a top coat film is coated on the surface of the base coating film.

Various low-temperature plasma atmospheres can be used in this invention, but for example, 0.1 to 1
Under reduced pressure of about 0 torr, frequency 103~10”fi
High frequency glow discharge generated by high frequency discharge of about Z, under atmospheric pressure or reduced pressure, power supply voltage 10 to 50 kV,
Corona discharge with a frequency of 1 to 100 klIZ is preferred.

The method for forming a multilayer coating film of this invention includes a urethane resin paint,
It can be applied to coatings using all kinds of paints, such as algide resin paints, melamine resin paints, and acrylic resin paints.

The present invention will be described in detail below with reference to the drawings showing an example of an apparatus for carrying out low temperature plasma treatment of a base coating film, which is one step thereof.

Figure 1 shows a device for treating the surface of a base coating film by generating a low-temperature plasma atmosphere using high-frequency glow discharge.
An example of one using a frequency of about 0.09 Hz) is shown below.

- Inside Luger 1, there is an excitation electrode 2 and this excitation electrode 2.
A counter electrode 3 facing the is provided. Excitation electrode 2
is connected to an RF power source 5 via a matching unit 4, and a workpiece 7 on which a base coating film 6 is formed is placed on the counter electrode 3.

When using this device, first, the air inside the Pel Jar 1 is exhausted from the exhaust port in the direction of arrow Y in the figure by an exhaust system not shown in the figure, thereby reducing the pressure inside the Pel Jar 1.

Next, a gas for plasma generation is introduced between the two electrodes from X in the figure, so that the gas pressure in the Pelger 1 becomes a predetermined value.

The gas for plasma generation is not particularly limited in this example, but for example, the following can be selected and used depending on the purpose.

Air, hydrogen, ammonia, carbon dioxide, carbon tetrafluoride,
Reactive gases such as nitrogen, non-reactive gases such as argon and helium.

Among the above gases, gases containing oxygen such as air, or oxygen itself are preferred in this example.

The gas pressure in the herger is not particularly limited in this example, but for example, when using each of the above gases, the gas pressure is preferably in the range of 0.1 to 10 torr, and preferably in the range of 1 to 5 torr. It is more preferable that there be.

The reason why the gas pressure in the Pelger is limited to the above range is as follows. That is, if the gas pressure in the Pelger exceeds 1 Qtorr, it becomes difficult to generate a low-temperature plasma atmosphere, and even if it does occur, it is unstable and high processing efficiency cannot be obtained. Gas pressure is Q, l t, or
If it is less than r, the concentration of active species generated by the low-temperature plasma atmosphere will not be sufficient, so there is a tendency that high processing effects cannot be obtained. On the other hand, if the gas pressure in the Pelger is within the above range, a stable low-temperature plasma atmosphere can be obtained, and thus it is thought that high processing efficiency can be obtained.

After setting the gas pressure inside the Pelger 1 to a predetermined level as described above, the RF power source 5 is activated to apply RF to the excitation electrode 2 to excite the gas existing between the two electrodes and generate a low-temperature plasma atmosphere 8. let

The frequency of RF applied to the excitation electrode 2 is not particularly limited in this example, but is preferably 10'' to 109 Hz.If the frequency of RF is outside the above range, the stability of the low temperature plasma atmosphere 8 may decrease. Alternatively, it may not be possible to generate a low-temperature plasma atmosphere.Also, there is a risk that sufficient processing effects may not be obtained in such an unstable low-temperature plasma atmosphere.And,
Among the above ranges, 1 3.56 MHz or 2 MHz, which is generally used for high frequency ion brating etc.
RF at a frequency of 7.12 MHz or the like is preferred for this embodiment in view of the combination of the RF power source and the processing device such as the Pelger, the excitation efficiency for discharge, etc.

The activated species generated by the low-temperature plasma atmosphere 8 attack the surface of the base coat 6 and generate functional groups on the surface that contribute to the adhesion of the top coat, thereby causing the top coat applied thereon to form functional groups. It is thought that the adhesion between the coating film and the base coating film 6 is improved. Furthermore, if the conditions for the low-temperature plasma atmosphere 8 are within the preferable ranges of gas pressure and frequency, the surface of the base coat 6 is less likely to be degraded by the plasma, so that the top coat and the base Adhesion with the coating film 6 can be further improved. In this example, the low temperature plasma atmosphere 8 is
As shown in the figure, it is generated in a spatial manner within the Pelger 1, so even if the object to be coated has a complicated shape, the surface of the base coat 6 formed thereon can be treated uniformly over the entire surface. Can be done.

The processing time and the output of the RF power source are not particularly limited in this example, and may be appropriately selected depending on conditions such as the type of base coating, the size of the object to be coated, and the capacity of the processing apparatus.

The object to be coated 7 whose surface has been treated with the base coating film 6 as described above
If the top coat is applied to the surface of the treated base coat 6 after taking it out from the Pelger 1, a multilayer coat with sufficient adhesion can be obtained. In addition, since the base coating film 6 treated in this way has improved wettability,
The topcoat film formed thereon has high image clarity.

Figure 2 shows a device for treating the surface of a base coating film by generating a low-temperature plasma atmosphere using high-frequency glow discharge.
The following is an example of a system using llz).

The apparatus of this example takes advantage of the fact that microwaves generally have a longer lifespan than the above-mentioned RF.
0 extends outside the room, and a microwave transmitter 11, a plunger 12, and a gas cylinder 13 containing gas for plasma generation are connected to the tip thereof, respectively.

When using this device, first, the air in the processing chamber 9 is exhausted from the exhaust port in the direction of arrow Y in the figure by an exhaust system not shown in the figure, and the inside of the processing chamber 9 is brought into a reduced pressure state. do.

Next, the same gas as in the previous RF case is introduced into the quartz tube 10 from the gas cylinder 13 so that the gas pressure in the quartz tube 10 and the processing chamber 9 becomes a predetermined value. The gas pressure in the quartz tube 10 and the processing chamber 9 is not particularly limited in this example, but for the same reason as in the previous case, it is between 0.1 and 2.
Preferably 10 torr, 1 to 5 torr
More preferably, it is r.

After the quartz tube 10 and the processing chamber 9 are brought to a predetermined gas pressure as described above, the microwave transmitter 11 is activated to generate a low-temperature plasma atmosphere 14 within the quartz tube 10. The plunger 12 has the function of reflecting microwaves generated by the microwave transmitter 11, and can adjust the distance between it and the microwave transmitter 11 by moving it in the axial direction (in the vertical direction in the figure). , is used to adjust the intensity of the microwave applied to the gas quartz tube 10.

The frequency and output of the microwave from the microwave oscillator 11 are not particularly limited in this example, but if the frequency is 10'
It is preferable that the frequency is within the range of ~1012 Hz and the output is within the range of 800 to 4000 W. Among the above ranges, the frequency is 2450H, which is commonly used.
Microwave, which is z, is preferred for the same reason as in the case of RF. Further, the reason why the output of the microwave oscillator 11 is limited to the above range is that if the output is less than 800W, a sufficient processing effect cannot be obtained.
This is because if it exceeds W, the surface of the base coating film 6 may be damaged.

The active species generated by the low-temperature plasma atmosphere 14 are carried by the gas from the gas bomb 13 and blown from the end of the quartz tube 10 onto the base coating film 6 on the object 7 to be coated, and the surface of this base coating film 6 is A substance that attacks and produces functional groups on its surface that contribute to the adhesion of the top coat film, thereby improving the adhesion between the top coat film applied thereon and the base coat 6. it is conceivable that. Further, when the conditions for generating the low temperature plasma atmosphere 14 are set within the preferable ranges of the gas pressure and frequency, the surface of the base coating film 6 is less likely to be degraded by the plasma.
” The adhesion between the two-coat coating film and the base coating film 6 can be further improved. In this example, the activated species generated by the low-temperature plasma atmosphere 14 have a long life as described above, and are mixed with gas and blown onto the object with a spatial spread. Even if the base coat 6 has a complicated shape, the entire surface of the base coat 6 formed thereon can be uniformly treated.

Conditions such as treatment time are not particularly limited in this example, and may be appropriately selected depending on conditions such as the type of base coating, the size of the object to be coated, and the capacity of the treatment apparatus.

The object to be coated 7 whose surface has been treated with the base coating film 6 as described above
After taking it out from the processing chamber 9, if a top coat is applied to the surface of the treated base coat 6, a multilayer coat with sufficient adhesion can be obtained as in the previous case. .

Further, as in the previous case, the wettability of the treated base coating film 6 is improved, and the sharpness of the top coat film formed thereon is also improved.

Next, another example of an apparatus for low-temperature plasma processing will be explained with reference to FIG.

FIG. 3 shows an example of an apparatus for treating the surface of a base coating film by generating a low-temperature plasma atmosphere by corona discharge.

This device includes an excitation electrode 15 and a counter electrode 16 facing the excitation electrode 15. A high voltage power supply 17 is connected to the excitation electrode 15, and a workpiece 7 on which a base coating film 6 is formed is placed on the counter electrode 16 via an insulator 18. .

When using this apparatus, first, the object to be coated 7 on which the base coating film 6 has been formed is set on the insulator 18 . Then, the contactor which is a part of the excitation electrode 15], 5 a,
As shown in the figure, it lightly contacts the base coating film 6.

Next, the counter electrode 16 on which the object to be coated 7 is placed is moved in the Z direction in the figure, and a voltage is applied from the high voltage power supply 17 between both electrodes while sweeping the surface of the base coating film 6 with the contact L5a. Then, a low-temperature plasma atmosphere 19 is generated by corona discharge at the contact portion between the contactor 1.5a and the base coating film 6.

The power supply voltage applied to the excitation electrode 15 is not particularly limited in this example, but the power supply voltage is 10 to 50 kV and the frequency is 1 to 1. Preferably it is OOkHz. Further, within the above range, it is more preferable that the power supply voltage is 10 to 30 kV. If the power supply voltage applied to the excitation electrode 9 is less than LO kV, it is difficult to generate discharge, and if it exceeds 50 kV, there is a risk of damaging the base coating film 6. Further, if the frequency is outside the above range, it is difficult to stabilize the discharge, and there is a possibility that a sufficient treatment effect may not be obtained.

In principle, it is possible to generate a corona discharge even with direct current, but direct current is not preferable for the present invention because electric charges tend to accumulate unilaterally, so a sufficient treatment effect cannot be obtained.

The corona discharge treatment in this example may be performed under atmospheric pressure or under reduced pressure. When the corona discharge treatment is performed under atmospheric pressure, there is a drawback that the area of the low-temperature plasma atmosphere 19 is difficult to expand. By forming a flexible string and arranging a large number of them so that they can sufficiently follow the shape of the object to be coated, it becomes possible to handle objects with complex shapes. When performing corona discharge treatment under reduced pressure, the low-temperature plasma atmosphere 19 has a spatial spread as in the previous example, so even if the contact 15a cannot sufficiently follow the shape of the object to be coated, complex Can be applied to objects of various shapes.

The gas for plasma generation is not particularly limited in this example, but gases similar to those in the previous two examples can be selected and used depending on the purpose.

The activated species generated by the low-temperature plasma atmosphere 19 attack the surface of the base coat 60, as in the case of FIG. 1, and generate functional groups on the surface that contribute to the adhesion of the top coat. It is thought that this improves the adhesion between the top coat applied to this layer and the base coat 6. In addition, the conditions for generating the low temperature plasma atmosphere 19 are as follows:
When the power supply voltage and frequency are within the preferable ranges, the surface of the base coat 6 is less likely to be degraded by plasma, so that the adhesion between the top coat and the base coat 6 can be further improved. become.

The processing time and the output of the high voltage power supply are not particularly limited in this example, and may be appropriately selected depending on conditions such as the type of base coating, the size of the object to be coated, and the capacity of the processing apparatus.

The object to be coated 7 whose surface has been treated with the base coating film 6 as described above
After removing the base coat from the apparatus, if a top coat is applied to the surface of the treated base coat 6, a multilayer coat with sufficient adhesion can be obtained. As in the previous case, the wettability of the treated base coating film 6 is improved, and the sharpness of the top coating film formed thereon is also improved.

Next, the apparatus for low-temperature plasma processing shown in FIG. 4 will be explained.

This device, like the device shown in FIG.
0 and a counter electrode 21 facing the electrode. Excitation electrode 2
0 is connected to the high voltage power supply 17, and the counter electrode 21 is grounded. Then, as in the previous apparatus, the object 7 to be coated on which the base coat 6 is formed is placed on the counter electrode 21, and the base coat 6 is processed. Excitation electrode 2
The power supply voltage and frequency applied to 0 need only be on the same order of magnitude as those of the device shown in FIG.

This device differs from the previous device in that the tip of the excitation electrode 20 is not in contact with the base coat 6.

In this way, the tip of the excitation electrode 20 is coated with the base coat 1'l! The reason for avoiding contact with the base coating film 6 is that depending on the type of the base coating film 6, there is a risk of scratches on the coating film surface if the device is a contact type like the previous device.

When the tip of the excitation electrode 20 is not in contact with the base coating film 6 as in this device, the low-temperature plasma atmosphere 22 due to corona discharge cannot have a wide spatial spread. Therefore, in order to uniformly treat the entire surface of the base coating film 6, it is necessary to move the counter electrode 21 on which the object to be coated 7 is placed, as in the previous device, or, conversely, to move the excitation electrode 20. be. If the object 7 to be coated is small and has a simple shape, it is sufficient to move the object 7 to be coated.

If the object 7 to be coated has a complicated shape, such as an automobile body, and is large and heavy, the excitation electrode 20
Try to move towards the At this time, if the excitation electrode 20 is moved along the coating film using a robot, for example, the uniformity of the process will be further improved.

FIG. 5 shows the state of processing for such a workpiece 7 having a complicated shape. The excitation electrode 20 is
As described above, the robot moves along the object 7 to uniformly treat the surface of the base coat 6. In other respects, it is the same as the previous device,
The treatment is performed by generating a low-temperature plasma atmosphere 22 by corona discharge using an excitation electrode 20 whose tip does not come into contact with the base coating film 6. The power supply voltage and frequency applied to the excitation electrode 20 may also be approximately the same.

This figure differs from the device shown in FIG. 4 in that the counter electrode 21 is omitted and the tip of the excitation electrode 20 is covered with a dielectric layer 23. These differences are due to the following reasons.

That is, when the object 7 to be coated is made of a conductive material such as metal, the counter electrode 21 can be omitted as shown in the figure. However, in this way, the object to be coated 7
If it is made of a material with good conductivity, such as metal, there is a risk that local sparks will occur between it and the excitation electrode 20.

Therefore, as described above, the tip of the excitation electrode 20 is covered with a dielectric layer 23 made of glass or the like to prevent sparks from being generated from the tip of the excitation electrode 20 toward the object 7 to be coated.

Next, the apparatus for low-temperature plasma treatment shown in FIG. 6 will be explained.

This device is characterized in that a low-temperature plasma atmosphere is generated by creeping discharge, which is a type of corona discharge. Creeping discharge uses an electrode device A in which a dielectric layer 26 is sandwiched between an excitation electrode 24 (here, arranged in a comb shape and spread in a planar manner) and a counter electrode 25 that spreads in a planar manner. A high frequency voltage is applied between these two electrodes to generate a low temperature plasma atmosphere 27 around the picture electrode.

The power supply voltage and frequency applied to the excitation electrode 24 from the high frequency power supply device 29 may be approximately the same as those of the device shown in FIG. 3 above. In this device, as shown in the figure, the low-temperature plasma atmosphere 27 spreads around the electrode bag WA in a planar manner. By using the electrode device A, the entire surface of the base coating film 6 can be treated without moving either the device or the object 7 to be coated.

If the object 7 to be coated is large and heavy with a complicated shape, it is still necessary to move the electrode device A as shown in FIG. In the apparatus shown in the figure, a robot or the like may be used to move the electrode device A.

The other structure is the same as that of the device shown in FIG. It is configured. A power supply device 29 is connected to the electrode device A. In addition, in this device, since the object to be coated 7 is made of a conductive material such as metal as in the previous case, there is a risk of local sparks occurring between the object to be coated 7 and the excitation electrode 24. There is. Therefore, a dielectric layer 28 made of glass or the like is formed on the entire surface of the excitation electrode 24 to prevent sparks from occurring between the excitation electrode 24 and the object 7 to be coated.

According to the apparatus shown in this figure as described above, the treatment on the base coating film 6 is performed not in dots or lines as in the apparatuses shown in FIGS. 3 to 5, but in a planar manner. efficiency can be further improved.

Up to now, the method for forming a multilayer coating film according to the present invention has been explained only based on seven examples using the apparatus shown in the figure. It is not limited to. For example, in the seven examples above, a high-frequency glow discharge such as RF or microwave, or a corona discharge was used as the low-temperature plasma atmosphere, but a low-temperature plasma atmosphere generated by a DC glow discharge is used. It doesn't matter if you do it like this. In addition, in all of the above examples, the multilayer film has two layers, a base coat film and a top coat film, but the present invention can also be applied to improving the adhesion between each layer of a multilayer film with three or more layers. Needless to say. In short, if the surface of the base coat is subjected to low-temperature plasma treatment, and then the top coat is applied and formed on the surface of the base coat,
Other configurations are not particularly limited.

Next, examples of the present invention will be described together with comparative examples.

(Examples 1 to 8) A 5 an x 5 cm polypropylene plate was used as the object to be coated, and a two-component polyester type urethane paint (main agent/curing agent - 5/1) shown in Table 1 was applied to the surface of the plate. It was applied and cured under the following conditions to form a base coating film with a thickness of 100 capes.

The polypropylene plate on which the base coating film has been formed is set in the RF discharge treatment apparatus shown in Fig. 1, and after the inside of the Pel jar is evacuated by the exhaust system, oxygen is introduced as a gas and the inside of the Pel jar is heated to 1 to 5 torr. The degree of pressure reduction was set to . R
Activate the F power supply and apply RF output of IO ~ 30W to the excitation electrode.
was applied to generate oxygen plasma, and the surface of the base coat was treated in a low-temperature plasma atmosphere. After 10 to 60 seconds, the RF power source was stopped to complete the process, and the polypropylene plate was taken out from the apparatus. After this, a two-component polyester urethane paint (
Apply base agent/curing agent = 4/1) under the conditions shown in Table 1.
It was cured to form a top coat film with a film thickness of 100 μm, thereby forming a multilayer coating film.

Table 1 The adhesion of the obtained multilayer film was evaluated by the substrate eye test and 180
Evaluated by peel adhesion strength test.

In addition, the image clarity of the obtained multilayer film was visually observed.

The results are shown in Table 3.

(Examples 9 to 12) The base coating film was treated using the microwave discharge treatment apparatus shown in FIG.
Multilayer coatings were prepared in the same manner as in Examples 1 to 8, except that the coating was carried out under the conditions of 50 MI (z), and their adhesion and image clarity were measured. The results are also shown in Table 3.

(Examples 13 to 15) The base coating film was treated in the atmosphere using the corona discharge treatment apparatus shown in Fig. 3 under the conditions of a power supply voltage of 20 kV and a frequency of 5 kllz, and the treatment time was 5 to 15 seconds. A multilayer coating film was prepared in the same manner as in Examples 1 to 8, except that the adhesion and image clarity were measured. Same result as 3rd
Shown in the table.

(Examples 16 to 18) The base coating film was treated in the atmosphere using the corona discharge treatment apparatus shown in FIG. 4 under the conditions of a power supply voltage of 20 kV and a frequency of 5 kt (z), A multilayer coating film was created in the same manner as Examples 1 to 8, except that the time was 15 seconds.
The adhesion and image clarity were measured. The results are also shown in Table 3.

(Examples 19 to 21) The base coating film was treated using the creeping discharge treatment apparatus shown in FIG. 6 under the conditions of a power supply voltage of 20 kV and a frequency of 5 kHz.
Multilayer coating films were prepared in the same manner as in Examples 1 to 8, except that the processing was carried out in the atmosphere and the processing time was 5 to 15 seconds, and the adhesion and image clarity were measured. The results are also shown in Table 3.

(Example 22) The same procedure as Examples 16 to 18 was carried out, except that an alkyd resin paint was applied and cured under the conditions shown in Table 2 to form a base coat with a thickness of 100 mm. A multilayer coating was created and its adhesion and image clarity were measured. The results are also shown in Table 3.

(Example 23) A multilayer coating was prepared in the same manner as in Examples 16 to 18, except that a melamine resin-based paint was applied and cured under the conditions shown in Table 2 to form a base coat with a thickness of 1100 f. A coating film was prepared and its adhesion and image clarity were measured. The results are also shown in Table 3.

(Example 24) The same procedure as Examples 16 to 18 was carried out, except that an acrylic resin paint was applied and cured under the conditions shown in Table 2 to form a base coat with a thickness of 100 mm. A multilayer coating was created and its adhesion and image clarity were measured. The results are also shown in Table 3.

Table 2 (Comparative Example 1) Multilayer films were prepared in the same manner as in Examples 1 to 15, except that the surface of the base coating was not treated in a low-temperature plasma atmosphere, and their adhesion and image clarity were measured. did. The results are also shown in Table 3.

From the results in Table 3, it was found that Examples 1 to 24 all had better interlayer adhesion and image clarity than the Comparative Example.

(Examples 25 and 26) A multilayer film was formed in the same manner as in Examples 1 to 24 above, except that a metal plate was used as the object to be coated, and the equipment shown in Figures 5 and 7 was used as the processing equipment. When fabricated, it was possible to obtain a uniform multilayer film with high adhesion and sharpness.

(Comparative Example 2.3) A multilayer coating film was created in the same manner as in Examples 25 and 26, except that the excitation electrode surface was not covered with a dielectric layer, but many spark marks remained on the base coating film. , it was not possible to obtain a uniform multilayer film.

〔Effect of the invention〕

The method for forming a multilayer coating film according to the present invention is as described above, and after the surface of the base coat is subjected to low-temperature plasma treatment, a top coat is applied and formed on the surface of the base coat. It is easy to use, there is no need to treat waste liquid, and
It becomes possible to obtain a multilayer coating film with excellent interlayer adhesion and image clarity without being restricted by the shape of the object to be coated, the type of base coating film, processing time, etc.

[Brief explanation of drawings]

Figure 1 shows that among the steps of this invention, low-temperature plasma treatment is performed using RF
FIG. 2 is an explanatory diagram illustrating an apparatus for performing low-temperature plasma treatment using microwave discharge among the steps of this invention, and FIG. 3 is an explanatory diagram illustrating an apparatus for performing low temperature plasma treatment using microwave discharge. FIG. 4 is an explanatory diagram illustrating an apparatus for performing low-temperature plasma treatment using corona discharge in the process of FIG. Figure 5 is an explanatory diagram illustrating the configuration of a low-temperature plasma treatment apparatus using corona discharge when the object to be coated is a conductive material, and Figure 6 is an illustration for performing low-temperature plasma treatment using creeping discharge among the steps of this invention. FIG. 7 is an explanatory diagram illustrating the configuration of a low-temperature plasma processing apparatus using creeping discharge when the object to be coated is a conductive material. 6... Base coating film 8.14-. 19,22.27...
・Low-temperature plasma atmosphere agent Patent attorney Takehiko Matsumoto Figure 1 Figure 2 Figure 3 Figure 4

Claims (4)

[Claims] (1) A method for forming a multilayer coating film, in which the surface of the base coating film is subjected to low-temperature plasma treatment, and then a top coat film is formed on the surface of the base coating film. (2) The method for forming a multilayer coating film according to claim 1, wherein the low-temperature plasma treatment is performed by exposing the surface of the base coating film to a low-temperature plasma atmosphere generated by RF discharge. (3) The method for forming a multilayer coating film according to claim 1, wherein the low-temperature plasma treatment is performed by spraying active species generated in a low-temperature plasma atmosphere by microwave discharge onto the base coating film. (4) The method for forming a multilayer coating film according to claim 1, wherein the low-temperature plasma treatment is performed by exposing the surface of the base coating film to a low-temperature plasma atmosphere generated by corona discharge.