JPH09157553A - Insulation coating material and method for insulation coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an insulation coating material by the use of which the coating work can be accomplished within a short time without forming pinholes, etc., and to provide a method for insulation coating therewith. SOLUTION: This insulation coating material for applying insulation coating to the surface of a heated object 3 comprises a coating base material 1 having a specified insulation effect, a solvent 2 which dissolves the base material 1 and a particulate material 4 comprising an insulation material and imparting shape stability during the coating work. The melting point of the base material 1 is higher than any of the boiling point of the solvent 2 and the heating temperature of the object 3, the boiling point of the solvent 2 is higher than the heating temperature of the object 3, and the melting point of the particulate material 4 is higher than the boiling point of the solvent 2. The simulation coating material fed into the surface of the object can be brought into a tack-free state within a short time because the solvent 2 is evaporated by the heat of the object, and the particulate material 4 protrudes beyond the surface of the layer of the base material 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating coating technique necessary for manufacturing electronic parts and the like, and particularly to an insulating coating technique using an insulating coating material obtained by dissolving a coating substrate in a solvent. It is about.

[0002]

2. Description of the Related Art In the manufacture of electronic parts such as small coils, transformers and capacitors, it is often necessary to apply an insulating coating to the surface of a predetermined member. For example,
In an electronic component such as a ferrite core used in a high frequency transformer or the like, a thickness of 10 or less is formed on the surface of a member made of a small tubular or ring ferrite having a diameter of about 3 to 15 mm.
Insulation coating is applied to about 100 μm.

Insulating coating of the above-mentioned small electronic parts is mainly performed by a powder coating method. The powder coating method is a method in which an object is embedded in a powdery coating material, an insulating coating material is attached to the surface, and the material is melted by heating to fix the coating material on the surface. However, this powder coating method has a drawback that it is difficult to control the film thickness and the insulating film cannot be coated with a uniform thickness. In the powder coating method, 100 μm
There is also a drawback that a thin insulating film cannot be formed when a thin insulating film is required because a thin film having a thickness of not more than a certain degree cannot be formed and a space for winding a coil is wide.

In order to eliminate such drawbacks, recently, an insulating coating by a spraying method has been often carried out. FIG. 2 is a schematic view for explaining a conventional insulating coating material by a spray method and a conventional coating method. The spray method is a method of spraying an insulating coating material with a spray gun or the like to fix it on an object. As the insulating coating material, a coating base material 1 such as an epoxy resin dissolved in a solvent 2 such as toluene is used. In the case of the spray method, the insulating coating material is sprayed and applied to the surface of the object 3 while holding the object 3 by hand or holding it by a holder of an automatic machine. After that, the object 3 is left for a predetermined time, and when the solvent 2 is evaporated and the coating substrate 1 is cured, the insulating coating is completed.

However, in the spray method, when it is necessary to coat the entire surface of the object 3, it is not possible to apply the insulating coating material to the entire surface by one injection, so at least twice from different directions. It is necessary to spray the insulating coating material and then cure it. This point is the same when the object 3 is held by some kind of holder, and since the insulating coating material cannot be applied to the contact portion of the holder, the holding portion is changed and the insulating coating material is sprayed again. Then, leave it to cure.

In the above-mentioned insulating coating, it is necessary to apply a coating having a considerably thick film thickness in order to obtain necessary insulating characteristics. In this case, it is difficult to perform such a thick insulating coating with one coating. That is, when the insulating coating material is applied thickly by one-time coating, it is difficult to evaporate the solvent 2 inside, and the coating substrate 1 is not completely cured.
Therefore, usually, the application and curing of the insulating coating material is repeated to perform laminated coating for stacking thin layers within about 5 μm. For example, when applying an insulating coating of about 200 μm, application and curing of the insulating coating material is repeated 1,000 to several thousand times.

[0007]

As described above, the insulating coating by the spray method is superior to the powder coating method in the uniformity of the film thickness and the like, but the insulating coating film of the required thickness is formed. In order to obtain it, it is necessary to repeat the spraying and curing of the insulating coating material 1000 to several thousand times, which takes a very long time. In the conventional method in which the solvent is left as it is, it may take about one day until the solvent is completely removed from the insulating coating material, which is a great obstacle to improvement in productivity.

Further, as mentioned above, one layer of coating is not completed by spraying and curing the insulating coating material once, and it is necessary to spray and cure at least twice.
With conventional insulation coating materials and insulation coating methods, the object cannot be touched until the insulation coating material is completely cured, resulting in poor work efficiency, and this is another obstacle to improving productivity. .

As another problem, in the above-described conventional insulation coating method, the solvent remaining inside the insulation coating film escapes from the insulation coating film by heating or the like in the final stage of the coating operation. There were cases where pinholes were generated.
Such pinholes cause deterioration of the insulation characteristics of the insulation coating film and mechanical characteristics such as peel strength. The invention of the present application has been made in order to solve the above problems, and provides an insulating coating material and an insulating coating method capable of completing a coating operation in a short time without generating pinholes or the like. Providing it is a problem to be solved.

[0010]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present application is an insulating coating material for applying an insulating coating to the surface of a heated object, which is a predetermined insulating material. A coating substrate having an action, and a solvent that dissolves the coating substrate, the melting point of the coating substrate is higher than the boiling point of the solvent and the heating temperature of the object, and the boiling point of the solvent is the heating of the object. It has a structure that is higher than the temperature. Similarly, in order to solve the above-mentioned problems, in the invention of claim 2 of the present application, in the structure of claim 1, a granular material made of an insulating material having a predetermined diameter for maintaining shape stability during the coating operation is added. The melting point of the granular material is higher than the boiling point of the solvent. Similarly, in order to solve the above problems, the invention according to claim 3 of the present application, the first step of supplying the insulating coating material according to claim 1 or 2 to the surface of a heated object, and the object An insulating coating method characterized in that a predetermined laminated coating is applied to the surface of an object by repeating the second step of evaporating the solvent by heat and the first and second steps.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a schematic diagram illustrating an insulating coating material and an insulating coating method according to an embodiment of the present invention. First, the insulating coating material of the present embodiment is largely different from the conventional one in that it is premised on being applied to the surface of the heated object 3. The insulating coating material of the present embodiment is composed of a coating base material 1 having a predetermined insulating action and a solvent 2 in which the coating base material 1 is melted, and a granular material 4 having a predetermined diameter.
Has been added.

The coating substrate 1 is made of various condensation type or addition type compounds and has a melting point of 15 such as polyimide resin.
It is preferable to use a high melting point material having a temperature of 0 ° C. or higher. This is because the object 3 is heated to a predetermined temperature in the present embodiment as described above, so that the coating substrate 1 does not melt even when heated. Further, the melting point of the coating substrate 1 needs to be higher than the boiling point of the solvent 2 at a minimum. If it is lower than the boiling point of solvent 2,
This is because the coating substrate 1 may also be melted out as the solvent 2 evaporates. An example of such a coating substrate 1 is "PYRE M" manufactured by DuPont.
L "(trade name) and the like can be preferably used.

Further, in order to improve the adhesion to the base material, it is preferable to add a small amount of epoxy resin. As the epoxy resin, for example, a solid bisphenol A type epoxy resin mixed with a phenol curing agent can be used. As the solvent 2, it goes without saying that the coating substrate 1 can be dissolved, but a solvent having a boiling point higher than the heating temperature of the object 3 is preferably used. This is because if the boiling point is lower than the heating temperature of the object 3, the solvent 2 will boil and foam when applied to the surface of the object 3. Examples of such a high boiling point solvent include enmethylpyrrolidone (NMP, boiling point 205 ° C.) and the like. The amount of the solvent 2 used with respect to the coating base material 1 is preferably, for example, about 5 times to 30 times the weight of the coating base material 1 of the solvent 2.

The granular material 4 is preferably made of a fluororesin such as polytetrafluoroethylene (PTFE). Such a fluororesin has a melting point of 2
The temperature is as high as about 90 ° C., which is suitable because deformation does not occur when the coating substrate 1 is heated and cured as described below. Granular material 4
Is preferably used with a diameter of about 1 μm to 10 μm. The amount used is 1 to 100 for the solvent.
A range of about 10% by weight is suitable.

Next, the insulating coating method of this embodiment using the above-mentioned insulating coating material will be described with reference to FIG. First, as the target object 3, when a ferrite core is manufactured, the target object 3 is a tubular or ring-shaped member made of ferrite. When oil or fat is present on the surface of the object 3 as described above, the adhesive force of the insulating coating material is reduced, and therefore degreasing treatment is performed in advance. Then, the target object 3 is accommodated in a container that can rotate or vibrate. It should be noted that FIG. 1 schematically shows an enlarged cross-sectional portion of the object 3.

First, prior to coating, the object 3 is preheated to a predetermined heating temperature. The heating temperature is appropriately determined in consideration of the heat resistant temperature of the object 3, the boiling point of the solvent 2, the melting point of the granular material 4, etc., but is usually in the range of about 75 ° C to 130 ° C. For example, when the target object 3 is the above-mentioned ferrite, the temperature is set to about 100 ° C. The heating is performed by means of radiant heating such as an infrared lamp, blast heating such as a blast heater, or the like. In this state, the insulating coating material having the above-described composition is sprayed to the surface of the object 3 to 1 μm to 10 μm.
Insulation coating material is applied to a thickness of about m (Fig. 1
(A)). At this time, since the target object 3 is heated as described above, the applied insulating coating material is heated by the heat of the target object 3 to a temperature close to the heating temperature of the target object 3 in a short time. As a result, the solvent 2 in the insulating coating material evaporates, and the concentration of the coating substrate 1 becomes thick. Since the boiling point of the solvent 2 is higher than the heating temperature, the solvent 2 gradually evaporates without boiling.

When the solvent 2 is evaporated to a considerable extent, the thickness of the insulating coating material becomes thin, and the granular material 4 is projected from the surface of the insulating coating material as shown in FIG. 1 (B). Even before the solvent 2 is completely evaporated and the coating base material 1 is completely cured, if the granular material 4 is projected by about 0.5 μm, it is tack-free (dry when touched with a finger). Alternatively, it is determined to be cured, and is also referred to as touch-free state). Next, object 3
The container containing the is rotated or vibrated to change the posture of the object 3, and the insulating coating material is sprayed and applied from the other direction. The applied insulating coating material is in a state in which the solvent 2 is evaporated and the granular material 4 is projected as in the above.

In this way, after the insulating coating material is sprayed from different directions at least twice to complete the application of the insulating coating material on the entire surface of the object 3, until the solvent 2 is completely evaporated. When the heating of the object 3 is continued and the solvent 2 is completely evaporated and the coating substrate 1 is cured, further coating is completed (FIG. 1 (C)). Then, by repeating the above-mentioned ABC process, laminated coating is performed. Incidentally, “curing” does not mean only “hardening” literally, but of course has a broad meaning of fixing and stabilizing the insulating coating material on the surface of the object 3. . still,
The coating of the upper layer can be performed even before the coating substrate 1 of the lower layer is completely cured. In this case, a small amount of solvent 2 may remain in the lower layer,
This solvent 2 is evaporated by the heating during the coating of the upper layer and released through the upper layer.

As is apparent from the above description, in the method of this embodiment, the object 3 is preheated when the insulating coating material is applied, so that the evaporation of the solvent 2 is promoted and the object 2 is shortened. The curing of the coating substrate 1 is completed. Further, even if the coating substrate is in a state before being completely cured, the protrusion of the granular material 4 causes the tack-free state, so that the next operation can be performed in a short time.
In the present embodiment, the object 3 is housed in a container that rotates or vibrates, and the posture of the object 3 is changed by the rotation or vibration of the container to shorten the time. This is made possible by adopting the method of this embodiment in which the coating substrate 1 is cured. From these points, according to the insulating coating material and the insulating coating method of the present embodiment, the time required for the entire coating operation is significantly shortened.

As the granular material 4, any material may be used as long as it is an insulator capable of maintaining the shape stability during the coating operation. That is, any material may be used as long as it is insoluble in the solvent 2, has a melting point equal to or higher than the heating temperature of the object 3, and does not change its shape due to a reaction with the coating substrate 1. For example, in addition to the above-mentioned fluororesin, materials such as silica, alumina, quartz, calcium carbonate, iron oxide, and silicon can be used as the material of the granular material 4.

[0021]

EXAMPLES Next, examples of the invention of the above embodiment will be described. For example, inner diameter 3.5mm, outer diameter 4.5mm, height 3
An example is given in which a surface of the cylindrical object 3 made of ferrite of about mm is coated with an insulating coating with a thickness of 30 μm. As the insulating coating material, DSDA (diphenylsulfone tetracarboxylic acid anhydride (acid dianhydride)) polyimide which is a kind of polyimide resin as the coating substrate 1, enmethylpyrrolidone as the solvent 2, and an additive material for improving the adhesion to the substrate A solid bisphenol A type epoxy resin / phenol curing agent mixture, which is a type of epoxy resin, is used as
The mixture is used in a weight ratio of 0: 300: 10.
To this, a granular material 4 made of PTFE which is a kind of fluororesin and having a diameter of 3 μm is further added. As the addition amount,
It is about 3.3% by weight with respect to the solvent 2.

Using the insulating coating material having such a composition, the object 3 was heated in advance to about 100 ° C. and sprayed onto the surface of the object 3 to apply it. The thickness of one coating is about 5 μm. The applied insulating coating material is
In a time of about 0.3 minutes, the granular material 4 protruded by about 1 μm and became a tack-free state. Then, the container accommodating the target object 3 is rotated or vibrated to change the posture of the target object 3, and the insulating coating material is similarly sprayed from different directions to finish the application of one layer, and then about 3 to 5 minutes. When the heating was maintained and allowed to stand, the solvent 2 was completely evaporated and the coating substrate 1 was cured.

In order to obtain a film thickness of about 30 μm, it is necessary to stack about 20 layers of the above-mentioned insulating coating. Therefore, it is necessary to repeat the above-mentioned work of insulating-coating for one layer 40 times or more. When coating was actually carried out under the above conditions, it took about 1 hour. On the other hand, it took about 24 hours to apply the same insulating coating by the conventional method using the conventional insulating coating material. Therefore, it was found that the insulating coating material and the insulating coating method of the present example can significantly improve the productivity.

In addition, it was confirmed that no structural defects such as pinholes were present in the obtained insulating coating film, and that the quality of the obtained film was also improved. this is,
Since heating is performed each time the insulating coating material is applied once, the internal residue of the solvent 2 that is conventionally seen is reduced, and even if there is internal residue, the boiling point of the solvent 2 is higher than the heating temperature. Since it is much higher, it is considered that the solvent 3 gradually evaporates without boiling. Although the object 3 may be heated in the conventional method only once in the final stage of coating, in the conventional insulating coating material using a solvent having a low boiling point, the heating in this final stage is not performed. At that time, the residual solvent boiled to form pinholes and the like.

Although the posture of the object 3 is changed each time the insulating coating material is sprayed and heated in the above-mentioned embodiments and examples, the container accommodating the object 3 is always rotated or vibrated. It is also possible to spray and heat the insulating coating material.

The insulating coating material and the insulating coating method of the present invention can be applied to the production of various electronic parts and electric parts including the above-mentioned ferrite core. Although not included in the scope of the invention of the present application, the same idea can be applied to the coating of a sliding film or the like intended to reduce the frictional force.

[0027]

As described above, according to the insulating coating material of claim 1 or the insulating coating method of claim 3 of the present application, it is possible to complete the coating work in a short time while pinholes and the like are completed. It is possible to obtain a high-quality insulating coating film that does not generate. Therefore, it is possible to contribute not only to improving the productivity of the coating operation but also to improving the insulating coating film. Also,
According to the insulating coating material of claim 2, the above-mentioned claim 1
In addition to the above effect, tack-free is realized by the protrusion of the granular material even before the coating substrate is cured, and as a result, the time required for coating can be further shortened.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating an insulating coating material and an insulating coating method according to an embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a conventional insulating coating material and a conventional coating method.

[Explanation of symbols]

 1 Coating substrate 2 Solvent 3 Object 4 Granular material

Claims (3)

[Claims] 1. An insulating coating material for applying an insulating coating to the surface of a heated object, which comprises a coating base material having a predetermined insulating action and a solvent that dissolves the coating base material. The insulating coating material is characterized in that the melting point of the material is higher than the boiling point of the solvent and the heating temperature of the object, and the boiling point of the solvent is higher than the heating temperature of the object. 2. A granular material made of an insulating material having a predetermined diameter for maintaining shape stability during coating operation is added, and the melting point of the granular material is higher than the boiling point of the solvent. Insulation coating material described. 3. A first step of supplying the insulating coating material according to claim 1 or 2 to the surface of a heated object,
A second step of curing the coating substrate with the particulate material protruding from the surface of the layer of the coating substrate while evaporating the solvent by the heat of the object, and further, the first and second steps An insulating coating method, characterized in that a predetermined laminated coating is applied to the surface of an object by repeating the above step.