ELECTRODEPOSITION COATED ARTICLE AND METHOD FOR PRODUCING SAME

Abstract

A method for producing an electrodeposition coated article, in which an insulating film is formed by forming an insulating layer on a surface of an article to be coated according to an electrodeposition method by using an electrodeposition coating material, and then by performing a baking treatment, the electrodeposition coating material contains a solvent containing polyamide imide and an organic solvent added to the electrodeposition coating material, a boiling point of the organic solvent is higher than 100° C., and a Hansen solubility parameter is similar to the polyamide imide and has high compatibility.

Claims

1. A method for producing an electrodeposition coated article, in which an insulating film is formed by forming an insulating layer on a surface of an article to be coated according to an electrodeposition method by using an electrodeposition coating material, and then by performing a baking treatment, wherein the electrodeposition coating material contains a solvent containing polyamide imide and an organic solvent added to the electrodeposition coating material, and a boiling point of the organic solvent is higher than 100° C., and a relationship of D.sub.(S−P)<6 is satisfied, D.sub.(S−P) being represented by an expression described below,
D.sub.(S−P)=[(dD.sup.S−dD.sup.P).sup.2+(dP.sup.S−dP.sup.P).sup.2+(dH.sup.S−dH.sup.P).sup.2].sup.1/2   (1) in the expression, dD.sup.S is a dispersion component of an HSP value of an organic solvent, dD.sup.P is a dispersion component of an HSP value of polyamide imide, dP.sup.S is a polarization component of an HSP value of an organic solvent, dP.sup.P is an polarization component of an HSP value of an polyamide imide, dH.sup.S is a hydrogen bonding component of an HSP value of an organic solvent, and dH.sup.P is a hydrogen bonding component of an HSP value of polyamide imide.

2. The method for producing an electrodeposition coated article according to claim 1, wherein a case in which a mixed liquid of the polyamide imide and the organic solvent becomes transparent is set to an organic solvent having solubility with respect to the polyamide imide, a case in which a mixed liquid of the polyamide imide and the organic solvent becomes opaque is set to an organic solvent not having solubility with respect to the polyamide imide, dD.sup.S, dP.sup.S, and dH.sup.S of the organic solvent are formed into a three-dimensional graph, a center of a minimum sphere on which all points indicating the organic solvent having solubility with respect to the polyamide imide enter is estimated as dD.sup.P, dP.sup.P, and dH.sup.P of the polyamide imide, and an organic solvent satisfying the relationship of D.sub.(S−P)<6 is selected.

3. The method for producing an electrodeposition coated article according to claim 1, wherein the electrodeposition coating material is water dispersible or water soluble, and the organic solvent is a hydrophilic solvent.

4. The method for producing an electrodeposition coated article according to claim 1, wherein the organic solvent is N,N-dimethyl acetamide, N,N-dimethyl formamide, propylene carbonate, dimethyl sulfoxide, 4-butyrolactone, or N-methyl-2-pyrrolidone.

5. The method for producing an electrodeposition coated article according to claim 1, wherein the article to be coated is a copper wire.

6. An electrodeposition coated article, wherein in an insulating film formed on a surface of an article to be coated, the number of pinholes on a film sectional surface measured by being observed with SEM is less than or equal to 50 items/10 μm square, and surface roughness Ra measured according to JISC0601 is less than or equal to 40 nm.

7. The electrodeposition coated article according to claim 6, wherein the article to be coated is a copper wire.

8. The method for producing an electrodeposition coated article according to claim 2, wherein the electrodeposition coating material is water dispersible or water soluble, and the organic solvent is a hydrophilic solvent.

9. The method for producing an electrodeposition coated article according to claim 2, wherein the organic solvent is N,N-dimethyl acetamide, N,N-dimethyl formamide, propylene carbonate, dimethyl sulfoxide, 4-butyrolactone, or N-methyl-2-pyrrolidone.

10. The method for producing an electrodeposition coated article according to claim 3, wherein the organic solvent is N,N-dimethyl acetamide, N,N-dimethyl formamide, propylene carbonate, dimethyl sulfoxide, 4-butyrolactone, or N-methyl-2-pyrrolidone.

11. The method for producing an electrodeposition coated article according to claim 8, wherein the organic solvent is N,N-dimethyl acetamide, N,N-dimethyl formamide, propylene carbonate, dimethyl sulfoxide, 4-butyrolactone, or N-methyl-2-pyrrolidone.

12. The method for producing an electrodeposition coated article according to claim 2, wherein the article to be coated is a copper wire.

13. The method for producing an electrodeposition coated article according to claim 3, wherein the article to be coated is a copper wire.

14. The method for producing an electrodeposition coated article according to claim 4, wherein the article to be coated is a copper wire.

15. The method for producing an electrodeposition coated article according to claim 8, wherein the article to be coated is a copper wire.

16. The method for producing an electrodeposition coated article according to claim 9, wherein the article to be coated is a copper wire.

17. The method for producing an electrodeposition coated article according to claim 10, wherein the article to be coated is a copper wire.

18. The method for producing an electrodeposition coated article according to claim 11, wherein the article to be coated is a copper wire.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a diagram schematically illustrating an electrodeposition coating device of an embodiment of the present invention.

[0026] FIG. 2 is an SEM picture diagram in which a sectional surface of an insulating portion of an insulating copper wire of Example 1 is enlarged.

[0027] FIG. 3 is an SEM picture diagram in which a sectional surface of an insulating portion of an insulating copper wire of Comparative Example 1 is enlarged.

Embodiments to Carry Out the Invention

[0028] Next, an embodiment of the present invention will be described on the basis of the drawings.

[0029] As illustrated in FIG. 1, the present invention is a method in which a rectangular conductive wire 101b is coated with polyamide imide and an organic solvent by an electrodeposition coating device 100, and the coated rectangular conductive wire 101b is subjected to a heat treatment, and thus, an insulating conductive wire which is an electrodeposition coated article including an insulating film of cured polyamide imide is formed on a surface is produced.

[0030] In the characteristic configuration of the present invention, an electrodeposition coating material 102 which is prepared by adding a predetermined organic solvent selected by a selection method using a known Hansen solubility parameter described below to an electrodeposition coating material made from a solvent containing polyamide imide is used as a coating material of an electrodeposition coating device 100. Thus, the electrodeposition coating material 102 containing the organic solvent is set to a coating material of electrodeposition coating, and thus, it is possible to simply prepare the electrodeposition coating material 102 which forms a desired insulating film, and it is possible to perform the electrodeposition coating without separately providing a step of applying the organic solvent.

[0031] A producing process of an electrodeposition coated article of the present invention will be described in detail with reference to FIG. 1. FIG. 1 illustrates a mode of performing an electrodeposition step, a baking step, and the like continuously in a vertical direction, but it is possible to perform the electrodeposition coating of the present invention by any mode such as a method of performing each step continuously in a horizontal direction or a batch mode of collectively performing one step, and then, of performing the next step.

[0032] FIG. 1 is a diagram illustrating an example of a producing process of forming an insulating film on a conductive wire 101 by the electrodeposition coating device 100. An anode 104 which is connected to a positive electrode of a direct current power source 103 is disposed on a conductive wire 101a having a circular sectional surface which is wound into the shape of a cylinder. The circular conductive wire 101a is pulled up in a direction of an arrow 105 and passes through each step. First, as a first step, the circular conductive wire 101a is rolled into the shape of a rectangle through a pair of rolling rollers 106, and thus, the rectangular conductive wire 101b having a rectangular sectional surface is obtained. Next, as a second step, the rectangular conductive wire 101b passes through an electrodeposition tank 107 filled with the electrodeposition coating material 102 in which the organic solvent is added to a solvent containing polyamide imide. In the electrodeposition coating material 102 of the electrodeposition tank 107, a cathode 108 which is connected to a negative electrode of the direct current power source 103 is disposed around the rectangular conductive wire 101b passing through the electrodeposition tank 107. When the rectangular conductive wire 101b passes through the electrodeposition tank 107, a direct current voltage is applied by the direct current power source 103, and dissolved polyamide imide is subjected to electrodeposition on the surface of the rectangular conductive wire 101b. Next, as a third step, the rectangular conductive wire 101b pulled up from the electrodeposition tank 107 passes through a baking furnace 109, and polyamide imide which has been subjected to the electrodeposition is baked on the rectangular conductive wire 101b, and thus, an insulating conductive wire is formed. Furthermore, in this specification, the “insulating conductive wire” indicates a conductive wire in which an insulating film is formed on a surface. Examples of the conductive wire include a copper wire, an aluminum wire, a copper wire, a copper alloy wire, and the like.

[0033] It is preferable that the temperature of the electrodeposition coating material 102 is 5° C. to 60° C., a concentration of polyamide imide is 1 to 40% by mass, a direct current voltage is 1 to 300 V, an energizing time is 0.01 to 30 seconds, and a baking temperature is 200° C. to 600° C. Furthermore, in the concentration of the organic solvent, the lower limit is set to the extent of not generating a crack in the insulating film, the upper limit may be set to a value to the extent of not making film formation according to the electrodeposition difficult due to a decrease in conductivity of the electrodeposition coating material, and a range of approximately 1 to 70% by mass is preferable.

[0034] Here, the selection method of the organic solvent of the present invention will be described in detail.

[0035] First, an organic solvent having a boiling point of higher than or equal to 100° C. is selected as the organic solvent. This is because the electrodeposition coating material containing water and polyamide imide is used, and thus, water is initially evaporated at the time of performing baking, that is, in a case where the organic solvent is evaporated before water, it is not possible to expect the swelling and dissolving effect of polyamide imide due to the organic solvent at the time of performing baking. In the swelling, the organic solvent enters between the polymer chains configuring polyamide imide, and polyamide imide is swollen and gelated, and thus, an effect of improving a viscosity is expected. In addition, the organic solvent enters between the polymer chains, and the polymer chains are rarely bonded to each other, and thus, an effect of dissolving polyamide imide is also expected. This is because polyamide imide is dissolved by the organic solvent, and thus, curing does not to start from an original curing temperature of polyamide imide of 80° C., and even after moisture is evaporated, it is possible to perform baking in a state where polyamide imide which is dissolved without being cured is evenly attached onto the surface of the conductive wire as a fluid.

[0036] Next, an organic solvent having excellent solubility with respect to polyamide imide is selected based on a Hansen solubility parameter.

[0037] First, polyamide imide powder and various organic solvents are mixed, and thus, a solution including 1% by mass each of polyamide imide and the organic solvent is prepared. Respective solutions are classified into a group of a transparent liquid in which the powder is gelated and a group of an opaque liquid in which the powder is precipitated. Next, a dispersion term dD.sup.S, a polarization term dP.sup.S, and a hydrogen bonding term dH.sup.S of a Hansen solubility parameter of each organic solvent are formed into a three-dimensional graph, a sphere having a minimum radius is prepared such that the group of the transparent liquid is on the inside and the group of the opaque liquid is on the outside, and the center of the sphere is estimated as a Hansen solubility parameter of polyamide imide. An organic solvent in which a value obtained by inputting the estimated Hansen solubility parameter of polyamide imide and the Hansen solubility parameter of the organic solvent into Expression (1) described below is D.sub.(S−P)<6 is selected as an organic solvent having excellent solubility with respect to polyamide imide.

D.sub.(S−P)=[(dD.sup.S-dD.sup.P).sup.2+(dP.sup.S−dP.sup.P).sup.S+(dH.sup.S−dH.sup.P).sup.2.sub.].sup.1/2   (1)

[0038] Here, dD.sup.S is a dispersion component having an HSP value of an organic solvent, dD.sup.P is a dispersion component of an HSP value of polyamide imide, dP.sup.S is a polarization component of an HSP value of an organic solvent, dP.sup.P is an polarization component of an HSP value of an polyamide imide, dH.sup.S is a hydrogen bonding component of an HSP value of an organic solvent, and dH.sup.P is a hydrogen bonding component of an HSP value of polyamide imide.

EXAMPLES

[0039] Next, examples of the present invention will be described in detail along with comparative examples.

Example 1

[0040] A rectangular copper wire having a width of 2 mm and a thickness of 0.1 mm was set to an anode of electrodeposition, the rectangular copper wire, and an electrodeposition tank was prepared into which an electrodeposition coating material obtained by adding N,N-dimethyl formamide (DMF) of 6% by mass to polyamide imide (water dispersible polyamide imide varnish) of 5% by mass as an organic solvent was put. Next, the rectangular copper wire passed through the electrodeposition tank at a linear velocity of 15 m/min for 2 seconds in a state where a direct current voltage of 5 V was applied, and then, the rectangular copper wire which had been subjected to electrodeposition was allowed to pass through a baking furnace in an atmosphere of 300° C., and was subjected to a baking treatment, and thus, an insulating copper wire having an insulating film thickness of 0.01 mm was prepared.

Example 2

[0041] An insulating copper wire having an insulating film thickness of 0.01 mm was prepared by the same method as that in Example 1 except that the organic solvent was changed to dimethyl sulfoxide (DMSO) of 6% by mass.

Example 3

[0042] An insulating copper wire having an insulating film thickness of 0.01 mm was prepared by the same method as that in Example 1 except that the organic solvent was changed to 4-butyrolactone (4B) of 6% by mass.

Example 4

[0043] An insulating copper wire having an insulating film thickness of 0.01 mm was prepared by the same method as that in Example 1 except that the organic solvent was changed to N-methyl-2-pyrrolidone (NMP) of 6% by mass.

Example 5

[0044] An insulating copper wire having an insulating film thickness of 0.01 mm was prepared by the same method as that in Example 1 except that the organic solvent was changed to DMF of 0.5% by mass.

Example 6

[0045] An insulating copper wire having an insulating film thickness of 0.01 mm was prepared by the same method as that in Example 1 except that the organic solvent was changed to DMF of 50% by mass.

Comparative Example 1

[0046] An insulating copper wire having an insulating film thickness of 0.01 mm was prepared by the same method as that in Example 1 except that the organic solvent was not added, but mist of DMF was added to the rectangular copper wire after the rectangular copper wire passed through the electrodeposition tank.

Comparative Example 2

[0047] An insulating copper wire having an insulating film thickness of 0.01 mm was prepared by the same method as that in Example 1 except that the organic solvent was not added.

Comparative Example 3

[0048] An insulating copper wire having an insulating film thickness of 0.01 mm was prepared by the same method as that in Example 1 except that the organic solvent was changed to formamide of 6% by mass.

Comparative Example 4

[0049] An insulating copper wire having an insulating film thickness of 0.01 mm was prepared by the same method as that in Example 1 except that the organic solvent was changed to acetone of 6% by mass.

Contrast between Examples and Comparative Examples

[0050] In the insulating copper wires obtained in each of the examples and the comparative examples, the number of pinholes was evaluated by an SEM picture, surface roughness Ra was evaluated by a surface step profiler (using a stylus type surface shape measuring instrument manufactured by ULVAC, Inc.), and voltage resistance was evaluated (using an AC voltage resistance tester TOS5000 manufactured by KIKUSUI ELECTRONICS CORP.). The evaluation results are shown in Table 1.

TABLE-US-00001 TABLE 1 Evaluation Item Additive Presence Amount Boiling or Surface Pinhole Voltage (% by Point Absence Roughness (Item/10 μm Resistance Type mass) (° C.) D(S-P) of Crack Ra (nm) Square) (kV) Example 1 DMF 6 153 3.8 Absent 50 0 1.5 Example 2 DMSO 6 189 2.7 Absent 40 0 1.5 Example 3 4B 6 204 4.5 Absent 40 0 1.5 Example 4 NMP 6 202 2.6 Absent 50 0 1.5 Example 5 DMF 0.5 153 3.8 Absent 50 0 1.5 Example 6 DMF 50 153 3.8 Absent 50 0 1.5 Comparative DMF Mist — 153 3.8 Absent 250  16  1.5 Example 1 Treatment Comparative Not being — — — Present — — — Example 2 Added Comparative Formamide 6 211 18.6  Absent 200  50  0.3 Example 3 Comparative Acetone 6  57 5.8 Present — — — Example 4

[0051] In Examples 1 to 6, the insulating copper wires having excellent insulating properties were obtained in which any crack or any pinhole was not generated, the surface roughness was 40 to 50 nm, and the voltage resistance was 1.5 kV.

[0052] In Comparative Examples 1 and 3, any crack was not generated, but the surface roughness was 200 to 250 nm, the number of pinholes was 16 to 50 items/10 μm square, and the voltage resistance was 0.3 to 1.5 kV, and thus, each evaluation item had an inferior result, compared to the examples.

[0053] In both of Comparative Examples 2 and 4, a crack was generated, and in the other evaluation items, data for comparative evaluation was not obtained.

[0054] Next, the state of the structure on the sectional surface of the insulating copper wires of Example 1 and Comparative Example 1 was observed by an SEM picture. The SEM picture was imaged by using S-4300SE manufactured by Hitachi, Ltd. The results are illustrated in FIG. 2 and FIG. 3.

[0055] As illustrated in FIG. 2 and FIG. 3, in Example 1, any pinhole was not observed, whereas in Comparative Example 1, a plurality of pinholes were observed.

[0056] From the results described above, it was confirmed that electrodeposition baking is performed by using the electrodeposition coating material simply prepared by using the organic solvent which had a boiling point of higher than or equal to 100° C. and was selected by the Hansen solubility parameter, and thus, it was possible to obtain an insulating copper wire including an insulating film which had a dense and smooth surface and high voltage resistance without any pinhole in a safe producing environment.

INDUSTRIAL APPLICABILITY

[0057] It is possible to use the electrodeposition coated article of the present invention in a personal computer, a power inductor for a power source of a smart phone, a transformer of an on-vehicle inverter, and the like.

EXPLANATION OF REFERENCE NUMERALS

[0058] 102: electrodeposition coating material