JP2005125183A - Cured coating film forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cured coating film forming method capable of holding good repairing properties while forming a coating film excellent in scratch resistance. <P>SOLUTION: In the cured coating film forming method for curing the coating film formed after predetermined coating is applied to an article to be coated, two or more cured coating film forming processes 203 and 209 for curing the coating film are provided, and at least one process of the cured coating film forming processes 203 and 209 is provided after a coating quality inspection process 208. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for forming a cured coating film for curing a coating film after applying a predetermined paint to an object to be coated.

Generally, in an automobile manufacturing process, body parts are welded at a body factory to manufacture an automobile body, and then painting is performed at a painting factory.
As shown in FIG. 12, for example, the body factory 100 is roughly divided into a main body line 101 for a skeleton part of an automobile body and a subline 102 for a lid such as a door, a fender, a hood, a luggage, etc. The car body parts manufactured in the lines 101 and 102 are welded to complete the car body.
The completed automobile body is transported from the body factory 100 to the painting factory 200 and subjected to cleaning and electrodeposition coating such as degreasing and chemical conversion treatment in the cleaning / electrodeposition process 201, and then the intermediate coating process 202 and the top coating. It is sequentially sent to the painting process 203. In the top coating process 203, generally, in the case of a metallic color, a metallic base paint is first applied (in the case of an aqueous paint, a flash-off process for evaporating water is provided), and then a transparent clear paint is prepared. Applied. Thereafter, baking and drying are performed.
In a luxury car, after the baking and drying in the top coating process 203, a clear coating process 204 may be performed in which a clear coating is further applied and baking drying is performed (so-called double clear coating). As the clear paint, a thermosetting clear is used.

After each of the aforementioned coating processes, a quality inspection is performed in a quality inspection process 206. In each painting process, various defects such as so-called blisters, sagging, and pinholes are generated. Generally, about 2 to 10 defects are generated per vehicle. Most of them are light defects such as dust and the like, and are polished and repaired in a sharpening process 207 on the line. Defects that cannot be repaired by polishing are repaired in a spot repair process 212 outside the line, and in the case of a fatal defect, the process returns to the top coat process 203 and the top coat is repainted over the entire surface (repaint process 211).
After inspecting in the final painting inspection step 208 of the painting factory 200, the product is transported to the assembly factory 300, assembled in the assembly step 301 and completed as an automobile, and then inspected in the final quality inspection step 302. Although the number is not large, the painting factory 200 may be overlooked or the assembly process 301 may be damaged, so that the repair and polishing in the spot repair process 311 is also performed in the assembly factory 300.
The completed vehicle is dispatched to the dealer 400 in the shipping process 304, but the dealer 400 also checks the quality inspection process 401 before handing over the vehicle to the user 500 to check for defects that could not be found in the manufacturing process. The repair in the spot repair process 411 is performed accordingly.

On the other hand, there is a problem of scratches on the market, particularly for vehicles painted in deep colors. That is, although it is a bright color in the new car, as the day passes, a fine scratch is attached to the car and the like, and the value as a car decreases. Dust is more conspicuous as it is a dark colored vehicle, and it is necessary to wash the car. It will be to purchase.
In order to solve such problems, development and introduction of clear paints having excellent scratch resistance have been promoted.
As a clear paint excellent in scratch resistance, there is an ultraviolet curable acrylic hard coat agent. For example, like a paint shown in Patent Document 1, there is one in which a thermosetting resin composition is applied to an object to be coated and then irradiated with ultraviolet rays to cure the coating film.

JP 2003-53260 A

As described above, development and introduction of clear coating for curing a coating film by irradiation with ultraviolet rays has been progressed, but it has not been said that the improvement has been made sufficiently.
In other words, in order to take measures against scratches, it is necessary to increase the crosslink density of the paint to form a hard coating film. However, if a hard coating film is formed by ultraviolet irradiation, defects in the subsequent painting process and final process will occur. In the repair process, it becomes difficult to sharpen and remove paper for removing defects. Actually, the ultraviolet curable acrylic hard coating agent is excellent in scratch resistance, but it is almost impossible to perform the repair as described above.
Therefore, the present invention provides a method for forming a cured coating film that can maintain good repairability while forming a coating film having excellent scratch resistance.

The cured coating film forming method that solves the above problems has the following characteristics.
That is, according to the first aspect of the present invention, there is provided a cured coating film forming method in which a coating film is cured after a predetermined coating material is applied to an object to be coated. Provide more than the process.
Thereby, a strong hard coat film excellent in scratch resistance can be formed while maintaining good repairability.

Moreover, at least 1 process is provided after the coating quality inspection process among the said cured coating-film formation processes.
Thereby, after correcting all the defects generated in the coating process, the coating film can be made strong and excellent in scratch resistance, and a high-quality coating film can be formed.

Moreover, at least 1 process is an ultraviolet irradiation process which irradiates an ultraviolet-ray among the said cured coating film formation processes as described in Claim 3.
This makes it possible to use a UV-curable material as a clear paint and to install a UV irradiation device at a painting factory, assembly factory, or dealer. A hard coat film can be formed and good repairability can be maintained.

According to the fourth aspect of the present invention, in the ultraviolet irradiation step, ultraviolet rays containing 50% or more of the total irradiation energy in the wavelength region of 200 nm to 350 nm are irradiated.
Thereby, necessary and sufficient energy can be given to a coating film, and the coating film which was strong and excellent in the abrasion property can be completed.

In addition, as described in claim 5, at least one of the cured coating film forming steps has a Fischer hardness that can repair defects in the coating process and defects generated in the assembly process after coating. This is a primary cured coating film forming step in which the coating film is cured until it falls within the range of 200 to 300.
Thereby, in the primary cured coating film forming step, the UV clear paint can be cured until the hardness level is such that the repair can be performed relatively easily.

Moreover, as described in claim 6, in the first cured coating film forming step, an ultraviolet ray containing 50% or more of the total irradiation energy in a wavelength region of 350 nm to 450 nm is irradiated.
Thereby, in the primary cured coating film forming step, the UV clear paint can be cured until the hardness level is such that the repair can be performed relatively easily.

In the first cured coating film forming step, the energy of the irradiated ultraviolet ray is 1000 mj or more.
As a result, even if the object to be coated has a complicated shape, it is possible to cure the hardness of the coating film to a degree that can be repaired while suppressing a variation in the hardness of the coating film from each part to a uniform hardness. it can.

According to the present invention, it is possible to form a strong hard coat film excellent in scratch resistance while maintaining good repairability.
In this case, the UV clear paint is first cured to a uniform hardness until it reaches a hardness level that can be repaired relatively easily, and all defects generated in the painting process are corrected, and then the coating film is strong and scratch-resistant. It is possible to form a high-quality coating film.

Next, modes for carrying out the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a first embodiment of a process in a cured coating film forming method of the present invention in an automobile manufacturing process.
First, in the body factory 100, body parts manufactured by a main body line 101 for a skeleton part of an automobile body and a sub-line 102 for a lid such as a door, a fender, a hood, and a luggage are welded to complete an automobile body. .
The completed automobile body is transported from the body factory 100 to the painting factory 200, and after washing / electrodeposition coating in the cleaning / electrodeposition process 201, intermediate coating is performed in the intermediate coating process 202.

When the intermediate coating process 202 is completed, the automobile body is sent to the top coating process 203.
In the top coating process 203, generally, in the case of a metallic color, a metallic base paint is first applied (in the case of an aqueous paint, a flash-off process for evaporating water is provided), and then a transparent clear paint is prepared. Applied. Thereafter, heat drying is performed.
In a high-class vehicle, after the heat drying in the top coating process 203, a clear coating process 204 in which a clear paint is further applied and dried by heating may be passed (so-called double clear coating).

  As the clear paint in the present invention, an ultraviolet-type clear paint used in combination with thermosetting is used. This thermosetting UV clear can obtain the same hardness as a conventional thermosetting clear only by heat drying.

  After the above-described top coating process 203 or clear coating process 204, a quality inspection is performed in a quality inspection process 206. In each painting process, various defects such as so-called blisters, sagging, and pinholes are generated. Generally, about 2 to 10 defects are generated per vehicle. Most of them are light defects such as dust and the like, and are polished and repaired in a sharpening process 207 on the line. Defects that cannot be repaired by polishing are repaired in an off-line spot repair process 212. If the defect is fatal, the process returns to the top coat process 203 and the top coat is applied again over the entire surface (repaint process 211).

After the repair in the spot repair process 212 and the inspection in the final coating inspection process 208 are completed and the coating quality is satisfied, the coating surface is irradiated with ultraviolet rays in an ultraviolet irradiation process 209. Thereby, hardening of a coating film is advanced further and hardness is raised and it completes as a hard coat.
The automobile body whose coating has been cured is transferred to the assembly plant 300, assembled in the assembly process 301 and completed as an automobile, and then inspected in the final quality inspection process 302. When a defect is found in the inspection, repair or the like is performed in the spot repair process 311 as necessary.
Thereafter, the completed vehicle is dispatched to the dealer 400 in the shipping process 304, but the dealer 400 also performs an inspection in the quality inspection process 401 before delivering the vehicle to the user 500, and checks for defects that could not be found in the manufacturing process. If necessary, repair or the like in the spot repair process 411 is performed.

As described above, in the present cured coating film forming method, as the clear coating applied in the top coating process 203 and the clear coating process 204, the UV curing clear used together with the thermosetting is used, and the cured coating for curing the coating is used. As the film forming process, it is performed in the top coating process 203 and the clear coating process 204, and is performed in the primary cured coating film forming process in which the coating film is cured by heat drying and the ultraviolet irradiation process 209. It has a two-stage cured coating film forming step, which includes a secondary cured coating film forming step for progressing curing of the coating film.
These points are different from the conventional cured coating film forming method described above.

Further, the second cured coating film forming step can be performed not as the coating factory 200 but as the ultraviolet irradiation process 303 after the quality inspection process 302 at the assembly factory 300 as shown in FIG. .
Furthermore, the secondary cured coating film forming step can be performed as the ultraviolet irradiation step 402 at the dealer 400 as shown in FIG. 3 without being performed at the coating plant 200 and the assembly plant 300.

  Here, the thermosetting combined UV curable clear used in the present invention is a paint that can be cured by both heating and UV irradiation. First, by heating, it is equivalent to a conventional thermosetting clear. Can be cured to a hardness of. Thereafter, when ultraviolet irradiation is performed, the curing further proceeds to increase the hardness and complete the hard coat film.

In addition, when performing ultraviolet irradiation in the secondary cured coating film forming step, a hard coat film having high hardness and excellent scratch resistance can be obtained reliably by preheating the irradiated surface.
In this case, the pre-heating of the irradiated surface can be performed with an infrared lamp or the like, and when heated to about 80 ° C. to 100 ° C., the curability of the coating film is not adversely affected on various parts mounted on the automobile body. Can be improved.
Moreover, as an ultraviolet-ray irradiated in a secondary cured coating film formation process, the ultraviolet-ray which contains 50% or more of total irradiation energy in the wavelength range of 200 nm-350 nm is used, for example.
Furthermore, when the hardness of the coating film exceeds 300 in terms of Fischer hardness, it becomes difficult to repair, but the hardness at the end of the primary cured coating film forming process is in the range of about 200 to 300 in terms of Fischer hardness, and further about 250 The hardness at the end of the secondary cured coating film forming step is more than 300 in terms of Fischer hardness.

Therefore, after applying heat curing combined UV curable clear and applying heat curing, it can be handled in the same way as normal baking coating, and necessary repairs can be made. Is possible.
On the other hand, the UV curable clear after UV irradiation becomes an extremely strong hard coat film, so that it is almost impossible to repair or extremely difficult (the surface coated with a grinder or the like). However, it is difficult to repair while maintaining the value as a new car).

  Therefore, as a timing for completing the hard coat film by irradiating with ultraviolet rays, from the viewpoint of the coating quality when the automobile body reaches the user's 500 hand, it is handed over to the user 500 as shown in FIG. It is desirable to perform ultraviolet irradiation at the dealer 400 immediately before.

However, it may be difficult from the viewpoint of capital investment cost to provide all the dealers 400 that are present in large numbers with an ultraviolet irradiation device.
In such a case, as shown in FIG. 2, it is preferable to install an ultraviolet irradiation device in the assembly plant 300 and perform ultraviolet irradiation immediately before the vehicle is completed and shipped.
Further, from the viewpoint that the quality is guaranteed for each process, it can be said that it is preferable to perform ultraviolet irradiation after the repair is completed in the painting factory 200 as shown in FIG.

Thus, by providing a plurality of cured coating film forming steps, such as a primary cured coating film forming step and a secondary cured coating film forming step, it has excellent scratch resistance while maintaining good repairability. A strong hard coat film can be formed.
Further, among the plurality of cured coating film forming processes, an ultraviolet irradiation process 209, which is a secondary cured coating film forming process, is provided after the final coating inspection process 208, so that all defects generated in the coating process are corrected and then applied. The film can be made strong and excellent in scratch resistance, and a high-quality coating film can be formed.
Using a clear paint as a UV curable clear with heat curing, simply installing an UV irradiation device at the coating factory 200, assembly factory 300, or dealer 400 and providing an UV irradiation process makes it very difficult to scratch the coated surface. A strong hard coat film excellent in scratch resistance can be formed, and good repairability can be maintained.

Next, a second embodiment of the process in the method for forming a cured coating film of the present invention will be described.
As shown in FIG. 4, in this process, many lids are installed in a body factory 100 having a main body line 101 for a skeleton part of an automobile body and a subline 102 for a fender provided as necessary. The car body is completed with it removed. The automobile body completed at the body factory 100 is transported to the painting factory 200.
On the other hand, lids such as doors, hoods, and luggage that are not mounted on the car body at the body factory 100 are each completed at the line 601 of the parts welding factory 600 and conveyed to the parts painting factory 700.
For example, the parts welding factory 600 and the parts painting factory 700 are arranged in the same automobile manufacturing factory as the body factory 100 and the painting factory 200, respectively, or are provided as supplier sublines.

The automobile body with the lid transported from the body factory 100 is removed is subjected to painting at the painting factory 200 through the same process as in FIG.
That is, a plurality of cured coating film forming steps are provided, such as a top coating step 203 for heating and drying the clear coating, and an ultraviolet irradiation step 208 for performing ultraviolet irradiation, using an ultraviolet-type clear coating with heat curing.

In the parts painting factory 700, each part is painted separately, but the painting process itself is the same as the painting process in the painting factory 200.
That is, after the cleaning / electrodeposition step 701 and the intermediate coating step 702, the top base coating step 703 is applied with a metallic base coating and a clear coating, and is heated and dried as a primary cured coating film forming step. . Further, there is a case where double clear coating is performed in the clear coating step 704.
The above-described UV curing clear coating used in the part coating factory 700 is also used as the clear coating, and the hardness equivalent to that of the conventional thermosetting clear can be obtained only by heat drying.

After the above-described top coating step 703 or clear coating step 704, a quality inspection is performed in a quality inspection step 706, and if there is a defect, it is polished and repaired in a corner sharpening step 707. Defects that cannot be repaired by polishing are repaired in the spot repair process 712, and in the case of fatal defects, the process returns to the top coat process 703 and the top coat is repainted over the entire surface (repaint process 711).
After completing the repair in the spot repair process 712 and the inspection in the final coating inspection process 708 and satisfying the coating quality, the coating surface is irradiated with ultraviolet rays in the ultraviolet irradiation process 709 as a secondary cured coating film forming process. . Thereby, hardening of a coating film is advanced further and hardness is raised and it completes as a hard coat.

In this way, each part that has been painted is transferred to the parts assembly plant 800 and assembled in the parts assembly process 801.
Each assembled part and the automobile body that has been painted at the painting factory 200 are both transferred to the assembly factory 300 and assembled, and completed as a vehicle in the same process as in FIG.
Thereafter, as in the case of FIG. 1, the vehicle is delivered to the dealer 400 and delivered to the user 500.

Also in this embodiment, the secondary cured coating film forming step for the automobile body and each part is not performed in the painting factory 200 and the parts painting factory 700, but in the assembly factory 300 as shown in FIG. After the quality inspection process 302, it can also be performed as an ultraviolet irradiation process 303.
Further, the secondary cured coating film forming step may be performed as the ultraviolet irradiation step 402 at the dealer 400 as shown in FIG. 6 without being performed at the coating factory 200, the parts coating factory 700, or the assembly factory 300.

Next, a third embodiment of the process in the cured coating film forming method of the present invention will be described.
As shown in FIG. 7, in this process, many lids are installed in a body factory 100 having a main body line 101 for a skeleton part of an automobile body and a subline 102 for a fender provided as necessary. The car body is completed with it removed. The automobile body completed at the body factory 100 is transported to the painting factory 200.
On the other hand, lids such as doors, hoods, and luggage that are not mounted on the car body at the body factory 100 are each completed at the line 601 of the parts welding factory 600 and conveyed to the parts painting factory 700.
For example, the parts welding factory 600 and the parts painting factory 700 are arranged in the same automobile manufacturing factory as the body factory 100 and the painting factory 200, respectively, or are provided as supplier sublines.

The car body with the lid removed from the body factory 100 is subjected to washing / electrodeposition coating in the washing / electrodeposition process 201 at the painting factory 200 and then intermediate coating in the intermediate coating process 202. Is done.
Next, in the top coat process 203, in the case of a metallic color, first, a metallic base paint is applied (in the case of a water-based paint, a flash-off process for evaporating water is provided), and further a transparent clear paint is prepared. Applied.

Next, an ultraviolet curing type clear paint (so-called UV clear) is applied in the clear coating process 204, and the first ultraviolet irradiation is performed in a first ultraviolet irradiation process 205 as a primary cured coating film forming process. . By the first ultraviolet irradiation, the first stage curing of the UV clear is completed.
When the first stage curing in the first ultraviolet irradiation step 205 is completed, the UV clearing proceeds to a hardness equivalent to that of a conventional thermosetting clear.

  After the first ultraviolet irradiation step 205, a quality inspection is performed in a quality inspection step 206. If a defect is found in the quality inspection process 206, it is polished and repaired in a sharpening process 207 on the line. Defects that cannot be repaired by polishing are repaired in an off-line spot repair process 212. If the defect is fatal, the process returns to the top coat process 203 and the top coat is applied again over the entire surface (repaint process 211).

  After completing the repair in the spot repair process 212 and the inspection in the final coating inspection process 208 and satisfying the coating quality, ultraviolet rays are applied to the painted surface in the second ultraviolet irradiation process 209 as a secondary cured coating film forming process. Irradiate. Thereby, hardening of a coating film is advanced further and hardness is raised and it completes as a hard coat.

On the other hand, in the parts painting factory 700, each part is painted separately, but the painting process itself is the same as the painting process in the painting factory 200 in FIG.
That is, after the cleaning / electrodeposition step 701 and the intermediate coating step 702, the metallic base coating and the clear coating are applied in the top coating step 703.
Next, an ultraviolet curing type clear coating (so-called UV clear) is applied in a clear coating process 704, and the first ultraviolet irradiation is performed in a first ultraviolet irradiation process 705 as a primary cured coating film forming process. . By the first ultraviolet irradiation, the first stage curing of the UV clear is completed.
When the first stage curing in the first ultraviolet irradiation step 705 is completed, the UV clearing proceeds to a hardness equivalent to that of a conventional thermosetting clear.

  After the first ultraviolet irradiation step 705, a quality inspection is performed in a quality inspection step 706. If a defect is found in the quality inspection process 706, it is polished and repaired in a line sharpening process 707 on the line. Defects that cannot be repaired by polishing are repaired in an off-line spot repair process 712, and in the case of a fatal defect, the process returns to the top coat process 703 and the entire top coat is repainted over the entire surface (repaint process 711).

  After finishing the repair in the spot repair process 712 and the inspection in the final coating inspection process 708 and satisfying the coating quality, ultraviolet rays are applied to the painted surface in the second ultraviolet irradiation process 709 as a secondary cured coating film forming process. Irradiate. Thereby, hardening of a coating film is advanced further and hardness is raised and it completes as a hard coat.

In this way, each part that has been painted is transferred to the parts assembly plant 800 and assembled in the parts assembly process 801.
Each assembled part and the automobile body that has been painted at the painting factory 200 are both transferred to the assembly factory 300 and assembled, and completed as a vehicle in the same process as in FIGS.
Thereafter, as in the case of FIGS. 1 and 4, the vehicle is delivered to the dealer 400 and delivered to the user 500.

Also in the present embodiment, the secondary cured coating film forming process for the automobile body and each part is not performed in the painting factory 200 and the parts painting factory 700, but in the assembly factory 300 as shown in FIG. It can also be performed as a second ultraviolet irradiation step 303 after the quality inspection step 302.
Furthermore, the second cured coating film forming step is not performed in the coating factory 200, the parts coating factory 700, or the assembly factory 300, but may be performed as the second ultraviolet irradiation process 402 in the dealer 400 as shown in FIG. it can.

Here, as the UV clear applied in the clear coating step 204 and the clear coating step 704, for example, the following is used.
That is, benzoin ethyl ether as a polymerization initiator was added to an ultraviolet curable resin composed of 50 parts by weight of tris (acryloxyethyl) isocyanurate, 20 parts by weight of trimethylolpropane trimethacrylate, and 30 parts by weight of tripropylene glycol diacrylate. The added one can be used as a UV clear.
When this UV clear is actually applied, the UV clear is dissolved in a solvent composed of xylene, butyl alcohol, and butyl cellosolve to prepare a 70 wt% solution to obtain a paint.

The UV clear paint applied to the object to be coated is irradiated with ultraviolet rays in two stages, a primary cured coating film forming process and a secondary cured coating film forming process, as described above. Let
In the first-stage primary cured coating film forming step, the UV clear coating is cured until the hardness level is such that the repair can be performed relatively easily.
When the hardness of the cured coating exceeds 300 in terms of Fischer hardness, it becomes difficult to repair, so the hardness at the end of the primary cured coating film forming step is preferably within the range of about 200 to 300 in terms of Fischer hardness. Preferably it is about 250.

In order to cure to a hardness within the range of about 200 to 300 in the Fischer hardness, which is a hardness level that can be repaired relatively easily, in the primary cured coating film forming step, as shown in FIG. Ultraviolet irradiation may be performed using an ultraviolet lamp having an output characteristic in which 50% or more of the total irradiation energy is included in a wavelength region of 350 nm to 450 nm on the long wavelength side.
In this case, ultraviolet irradiation is performed with an irradiation energy of about 1000 mj / cm 2 or more, preferably with an irradiation energy of about 1500 mj / cm 2 or more.

When an object to be coated that has a three-dimensionally complicated shape is irradiated with ultraviolet rays, such as an automobile body, even when the lid is removed, the irradiation amount varies depending on the part. As a result, depending on the output characteristics of the irradiated ultraviolet wavelength and the amount of irradiation energy, the hardness may be partially insufficient, or conversely, the hardness may be too high and repair may be difficult.
The optimum UV lamp and optimum irradiation energy differ depending on the type of UV curable resin and polymerization initiator used, but generally the irradiation energy and UV clear paint of the long wavelength side are irradiated. Regarding the relationship of hardness, the hardness increases as the energy increases until the irradiation energy reaches 1000 mj / cm 2, but when it exceeds 1000 mj / cm 2, the hardness becomes substantially constant and no significant increase is observed.

  Therefore, even if the object to be coated has a complicated shape, it is possible to apply ultraviolet rays on the long wavelength side with irradiation energy of about 1000 mj / cm 2 or more, preferably about 1500 mj / cm 2. It is possible to cure the film to such a degree that it can be repaired while suppressing a variation in the film hardness to obtain a coating film having a uniform hardness.

As described above, in the primary cured coating film forming process, after repairs are made in a state where a repairable and uniform hardness coating film is formed and the defects are eliminated, the secondary cured coating film forming process is performed. Irradiate with UV to complete the hard coat.
In the secondary cured coating film forming step, it is desirable to irradiate ultraviolet rays having a wavelength region shorter than the wavelength region of the ultraviolet rays irradiated in the primary cured coating film forming step.
For example, as shown in FIG. 11, it is desirable to irradiate ultraviolet rays that include 50% or more of the total irradiation energy in the wavelength range of 200 nm to 350 nm.

  As described above, by irradiating ultraviolet rays in the wavelength region on the short wavelength side, necessary and sufficient energy can be given to the coating film, and a coating film that is strong and excellent in scratch resistance can be completed.

In the case of this embodiment as well, the UV clear after irradiating the ultraviolet light on the short wavelength side in the second ultraviolet irradiation step 209/709 which is the secondary cured coating film forming step is an extremely strong hard coat film. Therefore, the repair is almost impossible or extremely difficult. Therefore, when the hard coat film is completed by irradiating with ultraviolet rays, the time when the automobile body reaches the hand of the user 500 is reached. From the viewpoint of the coating quality, it is desirable to irradiate the dealer 400 with ultraviolet rays immediately before handing it over to the user 500 as shown in FIG.

  However, since it may be difficult from the viewpoint of capital investment cost to provide all of the dealers 400 that are present in large numbers, it is difficult to install the ultraviolet irradiation device in the assembly plant 300 as shown in FIG. Thus, it is preferable to irradiate with ultraviolet rays just before the vehicle is completed and shipped. From the viewpoint that quality is guaranteed for each process, it can be said that it is preferable to irradiate ultraviolet rays after the repair is completed at the coating factory 200, as shown in FIG.

  And, using UV clear as the clear paint, installing the UV irradiation device at the coating factory 200, assembly factory 300, or dealer 400 and providing the UV irradiation process makes it very difficult to scratch the coating surface, scratch resistance In addition, it is possible to form a strong hard coat film with excellent repairability and to maintain good repairability.

In 1st embodiment of the process in the cured coating film formation method of this invention, it is a figure which shows the example which provided the ultraviolet irradiation process after the coating final inspection process of a coating factory. Similarly, in the first embodiment, it is a diagram showing an example in which an ultraviolet irradiation process is provided after a quality inspection process in an assembly factory. Similarly, in the first embodiment, it is a diagram illustrating an example in which an ultraviolet irradiation process is provided after a quality inspection process at a dealer. In 2nd embodiment of the process in the cured coating-film formation method of this invention, it is a figure which shows the example which provided the ultraviolet irradiation process after the coating final inspection process of a coating factory and a parts coating factory. Similarly, in the second embodiment, it is a diagram showing an example in which an ultraviolet irradiation process is provided after a quality inspection process in an assembly factory. Similarly, in the second embodiment, it is a diagram illustrating an example in which an ultraviolet irradiation process is provided after a quality inspection process at a dealer. In the third embodiment of the process in the method for forming a cured coating film of the present invention, a first ultraviolet irradiation process is provided after the clear coating process of the coating factory and the parts coating factory, and a second ultraviolet irradiation process is performed after the final coating inspection process. It is a figure which shows the example provided. Similarly, in the third embodiment, the first ultraviolet irradiation process is provided after the clear coating process of the painting factory and the parts coating factory, and the second ultraviolet irradiation process is provided after the quality inspection process of the assembly factory. . Similarly, in the third embodiment, it is a diagram showing an example in which a first ultraviolet irradiation process is provided after a clear coating process in a painting factory and a parts coating factory, and a second ultraviolet irradiation process is provided after a quality inspection process at a dealer. . It is a figure which shows an example of the output characteristic of an ultraviolet lamp provided with the output characteristic in which 50% or more of all irradiation energy is contained in the wavelength range of 350 nm-450 nm on the long wavelength side. It is a figure which shows an example of the output characteristic of an ultraviolet lamp provided with the output characteristic in which 50% or more of all the irradiation energy is contained in the wavelength range of 200 nm-350 nm on the short wavelength side. It is a figure which shows the process of the conventional cured coating-film formation method.

Explanation of symbols

200 Coating Factory 203 Top coating process (first cured coating film forming process)
208 Final coating inspection process 209 UV irradiation process (second cured coating film forming process)

Claims (7)

A cured coating film forming method for curing a coating film after applying a predetermined paint to an object to be coated,
A cured coating film forming method comprising providing two or more cured coating film forming steps for curing the coating film.   The cured coating film forming method according to claim 1, wherein at least one of the cured coating film forming processes is provided after the coating quality inspection process.   3. The cured coating film forming method according to claim 1, wherein at least one of the cured coating film forming processes is an ultraviolet irradiation process of irradiating ultraviolet rays. 4.   4. The cured coating film forming method according to claim 3, wherein in the ultraviolet irradiation step, ultraviolet rays containing 50% or more of the total irradiation energy in a wavelength region of 200 nm to 350 nm are irradiated. Among the cured coating film forming steps, at least one step is:
A first cured coating film forming process in which the coating film is cured until the hardness of the coating film is within a range of 200 to 300 in terms of Fischer hardness, which can repair defective coating and scratches generated in the assembly process after coating. The method for forming a cured coating film according to any one of claims 1 to 3, wherein:   6. The cured coating film forming method according to claim 5, wherein in the first cured coating film forming step, ultraviolet rays containing 50% or more of the total irradiation energy are irradiated in a wavelength range of 350 nm to 450 nm. The method for forming a cured coating film according to claim 5 or 6, wherein in the first cured coating film forming step, the energy of the irradiated ultraviolet ray is 1000 mj or more.