JP2001167917A - R-Fe-B PERMANENT MAGNET AND MANUFACTURING METHOD OF THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provided an R-Fe-B permanent magnet, exhibiting superior corrosion resistance, electrical insulation and heat resistance, which are necessary for a magnet to be used in an automobile motor, and a simple manufacturing method of the magnet which uses a solution method. SOLUTION: On the surface of this R-Fe-B permanent magnet, an aluminum coating film is formed, on which a polyimide resin coating film is formed via an oxide film layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an R-Fe-B permanent magnet and a method for producing the same. More specifically, the present invention relates to an R-Fe-B-based permanent magnet exhibiting excellent corrosion resistance, electrical insulation, and heat resistance required for a magnet used for an automobile motor and the like, and a simple method for producing the same.

[0002]

2. Description of the Related Art R-Fe-B permanent magnets typified by Fe-B-Nd-based permanent magnets use abundant and inexpensive materials as resources compared to Sm-Co-based permanent magnets, and Because of its high magnetic properties, it has been put to practical use in various applications. However, since the R-Fe-B-based permanent magnet contains highly reactive R and Fe, it is easily oxidized and corroded in the air, and when used without any surface treatment, a slight amount of acid or Corrosion progresses from the surface due to the presence of alkali, moisture, etc., and rust is generated, which leads to deterioration and variation in magnet characteristics. Furthermore, when the rusted magnet is incorporated into a device such as a magnetic circuit, the rust may scatter and contaminate peripheral components.

In view of the above, in order to improve the corrosion resistance of R-Fe-B permanent magnets, a metal plating film having corrosion resistance is formed on the magnet surface by a wet plating method such as electroless plating or electroplating. The proposed magnet has already been proposed (see Japanese Patent Publication No. 3-74012). However, in this method, an acidic solution or an alkaline solution used in the pretreatment of the plating treatment may remain in the magnet hole, and the magnet may corrode with time. Further, since the magnet has poor chemical resistance, the surface of the magnet may be corroded during plating. Further, even if a metal plating film is formed on the magnet surface as described above, when the corrosion resistance test is performed under the conditions of a temperature of 60 ° C. and a relative humidity of 90%, after 100 hours, the magnetic property is 10% lower than the initial value. The above may be deteriorated.

A method of forming an oxidation-resistant chemical conversion film such as a phosphate film or a chromate film on the surface of an R—Fe—B permanent magnet has also been proposed (Japanese Patent Publication No. 4-2200).
No. 8, the coating obtained by this method is excellent in terms of adhesion to a magnet, but has a temperature of 60 ° C. and a relative humidity of 90.
%, The magnetic properties may deteriorate by 10% or more from the initial value after 300 hours.

Further, a method of forming an aluminum film by a vapor phase growth method and then performing a chromate treatment, that is, a so-called aluminum-chromate treatment method (proposed to improve the corrosion resistance of R—Fe—B permanent magnets) has been proposed. 6-661
No. 73) significantly improves the corrosion resistance of the magnet. However, the chromate treatment used in this method uses hexavalent chromium, which is environmentally undesirable,
The wastewater treatment method is complicated. In addition, since the coating obtained by this method contains hexavalent chromium in a trace amount,
There are also concerns about the effects on the human body when handling magnets.

[0006]

On the other hand, R-Fe-B-based permanent magnets incorporated and used in automobile motors include:
Not only corrosion resistance, but also excellent electrical insulation and heat resistance are required.
Chromate treatment cannot provide excellent electrical insulation and heat resistance. Therefore, in the present invention,
An object of the present invention is to provide an R-Fe-B permanent magnet exhibiting excellent corrosion resistance, electrical insulation, and heat resistance required for magnets used in automobile motors and the like and a simple manufacturing method using a solution method. I have.

[0007]

Means for Solving the Problems The present inventors have made intensive studies in view of the above points, and as a result, have formed an aluminum film on the surface of an R-Fe-B-based permanent magnet and formed a polyimide resin film thereon. By doing so, they have conceived to exert excellent electrical insulation and heat resistance in addition to excellent corrosion resistance. R-
Forming an aluminum coating on the surface of the Fe-B permanent magnet;
A technique for forming a polyimide resin film thereon has already been disclosed in Japanese Patent Application Laid-Open No. 8-279407.
However, the method of forming a polyimide resin film in this technique is to form a condensation type polyimide resin film by vapor deposition polymerization using two kinds of raw material monomers (aromatic carboxylic dianhydride and aromatic diamine). Although this technique is valuable as a method of forming a polyimide resin film having excellent performance on an aluminum film, a large-scale apparatus is required to perform the vapor deposition polymerization method. In addition, pretreatment such as cleaning must be strictly performed. Therefore, it causes an increase in manufacturing cost and is not always satisfactory from the viewpoint of mass production.

In view of the above points, the present inventors conducted further intensive studies, and as a result, formed an oxide film layer on the surface of an aluminum film on an R-Fe-B-based permanent magnet, and formed a polyimide resin film thereon. Then, due to the presence of the oxide film layer,
It has been found that the polyimide resin coating adheres firmly to the aluminum coating surface and exhibits excellent corrosion resistance, electrical insulation and heat resistance together with the aluminum coating. In addition, it has been found that a reaction of forming a polyimide resin film proceeds efficiently on the oxide film layer, and a film having excellent adhesion to the aluminum film surface can be obtained even by a solution method.

The present invention has been made based on such findings, and the permanent magnet of the present invention has the following features.
An aluminum coating on the surface of the Fe-B permanent magnet;
It is characterized in that a polyimide resin film is provided on the surface of the aluminum film via an oxide film layer. A permanent magnet according to a second aspect is characterized in that, in the permanent magnet according to the first aspect, the polyimide resin film is an additional type polyimide resin film. A permanent magnet according to a third aspect is characterized in that, in the permanent magnet according to the second aspect, the addition type polyimide resin film is a film obtained from bisallylnadiimide. The permanent magnet according to claim 4 is the permanent magnet according to any one of claims 1 to 3, wherein the thickness of the aluminum coating is 0.01 μm to 50 μm.
m. A permanent magnet according to a fifth aspect is characterized in that, in the permanent magnet according to any one of the first to fourth aspects, the thickness of the oxide film layer is 0.01 μm to 2 μm. A permanent magnet according to a sixth aspect is characterized in that, in the permanent magnet according to any one of the first to fifth aspects, the film thickness of the polyimide resin film is 1 μm to 15 μm. Further, according to the method of manufacturing a permanent magnet of the present invention, an aluminum film is formed on the surface of an R-Fe-B-based permanent magnet, and then the surface of the aluminum film is oxidized in an oxygen atmosphere. Forming a polyimide resin film on the surface of the oxide film layer, and applying a polyimide resin film forming treatment liquid on the surface of the oxide film layer, followed by heat treatment to form a polyimide resin film. Also,
According to a eighth aspect of the present invention, in the method of the seventh aspect, the aluminum film is formed by a vapor deposition method. According to a ninth aspect of the present invention, in the manufacturing method of the eighth aspect, the film thickness is 0.01.
It is characterized in that an aluminum coating of μm to 50 μm is formed. According to a tenth aspect of the present invention, in the manufacturing method of the seventh aspect, the R-Fe-B-based permanent magnet and the aluminum piece are placed in a processing container, and both are subjected to vibration in the processing container. And / or stirring both to form an aluminum coating. The manufacturing method according to claim 11 is the same as the manufacturing method according to claim 10.
In the manufacturing method described above, the film thickness is 0.01 μm to 1 μm
Forming an aluminum film of According to a twelfth aspect of the present invention, in the manufacturing method according to any one of the seventh to eleventh aspects, the oxidation treatment in an oxygen atmosphere is performed under an ordinary pressure of an oxygen concentration of 0.01% to 20%.
Alternatively, the heat treatment is performed at 10 ° C. to 500 ° C. under a reduced pressure of oxygen pressure (partial pressure) of 0.1 Pa to 2 × 10 ⁴ Pa.
The manufacturing method according to claim 13 is the method according to claims 7 to 12.
Wherein the polyimide resin coating is an addition type polyimide resin coating. A manufacturing method according to a fourteenth aspect is characterized in that, in the manufacturing method according to the thirteenth aspect, the addition type polyimide resin coating is a coating obtained from bisallylnadiimide.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The permanent magnet of the present invention
An aluminum coating is provided on the surface of the B-based permanent magnet, and a polyimide resin coating is provided on the aluminum coating surface via an oxide coating layer.

The method for forming an aluminum film on the surface of the R-Fe-B permanent magnet is not particularly limited.
However, considering that the magnet and the aluminum coating are easily oxidized and corroded, the following method using a vapor phase growth method, an R-Fe-B-based permanent magnet and an aluminum piece are placed in a processing vessel, and And apply vibration to both,
And / or a method of stirring both is a desirable method.

(1) Method by vapor phase epitaxy The vapor phase epitaxy that can be employed for forming an aluminum film includes known methods such as vacuum deposition, ion sputtering, and ion plating. Can be The aluminum film may be formed under general conditions in each method, but the denseness of the formed film,
From the viewpoint of the uniformity of the film thickness, the film formation speed, and the like, it is desirable to employ a vacuum evaporation method or an ion plating method. In addition, cleaning, degreasing,
It goes without saying that a known cleaning treatment such as sputtering may be performed.

[0013] The temperature of the magnet during the film formation is 200
It is desirable that the temperature be set in the range of 500C to 500C. The temperature is 20
If the temperature is lower than 0 ° C., a film having excellent adhesion to the magnet surface may not be formed. If the temperature exceeds 500 ° C., a crack occurs in the cooling process after the film is formed, and the film peels off from the magnet. This is because there is a fear.

The thickness of the aluminum film is 0.01 μm
If it is less than 50 μm, excellent corrosion resistance may not be exhibited. If it exceeds 50 μm, not only may the production cost be increased, but also the effective volume of the magnet may be reduced, so that 0.01 μm to 50 μm is desirable. But,
0.05 μm to 25 μm is more desirable.

(2) A method in which an R-Fe-B-based permanent magnet and an aluminum piece are placed in a processing vessel, and both are vibrated and / or agitated in the processing vessel. The aluminum piece to be used may have various shapes such as a needle shape (wire shape), a column shape, and a lump shape. From the viewpoint of efficiently generating aluminum fine powder which is a constituent source of the aluminum film, It is desirable to use a needle-shaped or column-shaped one with a sharp end.

The size (major axis) of the aluminum piece is preferably from 0.05 mm to 10 mm, more preferably from 0.3 mm to 5 mm, and still more preferably 0 mm, from the viewpoint of efficiently producing aluminum fine powder. .
5 mm to 3 mm. The aluminum pieces having the same shape and the same size may be used, or the aluminum pieces having different shapes and different sizes may be mixed and used.

The vibration and / or stirring of the magnet and the aluminum piece are desirably performed dry in consideration of the fact that both are easily oxidized and corroded.
It can be performed at room temperature. The processing vessel that can be used in the present invention does not require a complicated apparatus, and may be, for example, a processing chamber of a barrel apparatus. As the barrel device, a known device such as a rotary type, a vibration type, and a centrifugal type can be used. In the case of a rotary type, the rotation speed is 20 rpm to 50 r.
pm is desirable. In the case of the vibration type, the frequency is 50 Hz to 100 Hz, and the vibration amplitude is 0.3 mm to 10 mm.
mm. In the case of the centrifugal type, it is desirable that the rotation speed be 70 rpm to 200 rpm.

The amount of the magnet and the aluminum piece to be put in the processing container is 20 vol% to 90 vol% of the volume in the processing container.
Is desirable. If the amount is less than 20 vol%, the treatment amount is too small to be practical, and if it exceeds 90 vol%, it may not be possible to form a film efficiently.
Further, the ratio of the magnet and the aluminum piece put in the processing container is desirably 3 or less in terms of volume ratio (magnet / aluminum piece). If the volume ratio exceeds 3, it may take a long time to form a coating film, which may not be practical. Also,
Although the processing time depends on the processing amount, it is usually 1 hour to 10 hours.
Time.

According to the above-described method, aluminum fine powder generated from aluminum pieces is applied to the magnet surface to form an aluminum coating. The phenomenon that the aluminum fine powder adheres to the magnet surface is considered to be a kind of mechanochemical reaction, and the aluminum fine powder adheres firmly to the magnet surface, and the resulting aluminum coating shows excellent corrosion resistance. From the viewpoint of ensuring sufficient corrosion resistance, as described above,
The thickness is desirably 0.01 μm or more. Although the upper limit of the film thickness is not particularly limited, the film thickness is 1 μm.
This method is suitable as a method for forming an aluminum film having a film thickness of 1 μm or less because it takes time to form an aluminum film exceeding m.

As a step prior to forming an oxide film layer on the aluminum film surface, shot peening (a method of modifying the surface by colliding hard particles) may be performed. By performing shot peening, the aluminum film is smoothed, the corrosion resistance of the aluminum film itself is improved, and a uniform oxide film layer is easily formed, forming a polyimide resin film having excellent performance even in a thin film. Can be easier. As the powder used for shot peening, a powder having a hardness equal to or higher than the hardness of the formed aluminum film is desirable. For example, a spherical hard powder having a Mohs hardness of 3 or more, such as a steel ball or a glass bead, may be used. When the average particle size of the powder is less than 30 μm, the pressing force against the aluminum film is small, and it takes time to process. On the other hand, 300
If it exceeds 0 μm, the surface roughness may be too rough and the finished surface may be non-uniform. Therefore, the average particle size of the powder is desirably 30 μm to 3000 μm, and 40 μm.
m to 2000 μm is more desirable. The injection pressure in shot peening is 1.0 kg / cm ^{2 to} 5.0 kg /
cm ² is desirable. If the injection pressure is less than 1.0 kg / cm ² , the pressing force on the metal film is small and it takes time to process, and if it exceeds 5.0 kg / cm ² , the pressing force on the metal film becomes uneven and the surface roughness is increased. This is because the degree of deterioration may be caused. The injection time in shot peening is preferably 1 minute to 1 hour. If the injection time is less than 1 minute, uniform treatment may not be performed on the entire surface, and if it exceeds 1 hour, the surface roughness may be deteriorated.

After forming an aluminum coating on the magnet surface, heat treatment can be performed to increase the adhesion between the magnet surface and the aluminum coating. If the temperature of the heat treatment is less than 200 ° C., the interface reaction between the magnet and the aluminum coating may not sufficiently proceed to improve the adhesion, and if it exceeds 500 ° C., the magnetic properties of the magnet may be deteriorated. The aluminum coating may be dissolved. Therefore, the heat treatment is desirably performed at 200 ° C. to 500 ° C., but is more desirably performed at 200 ° C. to 350 ° C. from the viewpoint of productivity and manufacturing cost. The same effect can be obtained by a heat treatment after applying a polyimide resin film forming treatment liquid to the surface of the oxide film layer described later.

As a method of forming an oxide film layer on the surface of the aluminum film, for example, an oxidation treatment method in an oxygen atmosphere, an oxidation treatment method in an atmosphere containing steam (including general steam treatment) and the like can be mentioned. Can be As an oxidation treatment method in an oxygen atmosphere, for example, there are a method in which oxygen concentration and temperature are controlled in a treatment chamber and a natural oxidation in the air. As the processing conditions, the oxygen concentration is 0.01%.
Under normal pressure of ~ 20% or oxygen pressure (partial pressure) 0.1 Pa
It is desirable to carry out at a temperature of 10 ° C. to 500 ° C. under a reduced pressure of ２2 × 10 ⁴ Pa. The normal pressure condition in which the oxygen concentration is 0.01% to 20% may use the atmosphere itself or may be adjusted to a desired component composition using an inert gas such as a nitrogen gas or an argon gas. It may be something. Oxygen pressure (partial pressure) is 0.1 Pa to 2 × 10 ⁴ Pa.
The composition may be adjusted only by oxygen pressure, or may be adjusted to a desired component composition or pressure using an inert gas such as nitrogen gas or argon gas. The reason why it is desirable to perform the oxidation treatment at 10 ° C to 500 ° C is as follows.
If the temperature exceeds 00 ° C., the magnetic properties of the magnet may be deteriorated and the aluminum coating may be deformed. Also, as the processing temperature increases, it becomes difficult to form a dense and thin oxide film layer, or the surface roughness of the oxide film layer becomes rough, which adversely affects the formation of the polyimide resin film, resulting in This is because a magnet having excellent performance such as corrosion resistance may not be obtained. The processing time when performing the oxidation treatment in the processing chamber under the above processing conditions is usually 5 minutes to 48 hours. As an oxidation treatment method in an oxygen atmosphere, in addition to the above-described methods, the above-described shot peening or shot blasting of the aluminum coating surface, sputtering treatment under a weak voltage, or under oxygen plasma formation by high frequency. Oxidation treatment. The oxidation treatment method (including general steam treatment) in an atmosphere containing steam is carried out while controlling the steam concentration and the temperature. % To 100%, processing temperature is 1
0 ° C to 300 ° C.

The thickness of the oxide film layer formed by the above method is desirably 0.01 μm or more. This is because if the film thickness is less than 0.01 μm, it may not contribute to excellent adhesion of the polyimide resin film to the surface of the aluminum film. On the other hand, the thickness of the oxide film layer is desirably 2 μm or less. If the thickness exceeds 2 μm, excellent adhesion of the polyimide resin film to the surface of the aluminum film may be adversely affected. Further, in consideration of a demand based on miniaturization of the magnet itself, the thickness of the oxide film layer is more preferably 1 μm or less.

Next, a method for forming a polyimide resin film on the surface of the oxide film layer will be described. The polyimide resin coating may be an addition type polyimide resin coating or a condensation type polyimide resin coating, but is preferably an addition type polyimide resin coating. The addition type polyimide resin has an unsaturated group at the terminal of the resin molecule and is obtained by three-dimensional crosslinking by addition reaction or radical reaction.However, since water is not generated during curing, the magnet is oxidized and corroded. It is a very convenient resin considering that it is easy to perform. Examples of the addition type polyimide resin include a resin obtained from bisallylnadiimide (BANI: see FIG. 1) which is an imide monomer synthesized from allylnadic anhydride and a diamine and having an allyl group at both ends after completion of the dehydration ring closure reaction. Other, nadic acid type polyimide resin (PMR),
Known resins such as bismaleimide type polyimide resin and acetylene terminal type polyimide resin can be used.

[0025]

Embedded image

Examples of the condensation type polyimide resin include a pyromellitic type polyimide resin obtained by a dehydration condensation reaction from pyromellitic dianhydride and 4,4′-diaminodiphenyl ether. Condensation type polyimide resin generates water upon curing, but the oxide film layer plays a role as a so-called protective layer on the magnet surface so that water does not easily come into contact with the magnet surface, so a polyimide resin film having excellent adhesion is provided. It can be formed on the aluminum coating surface.

The formation of the polyimide resin film on the surface of the oxide film layer is performed by applying a polyimide resin film forming treatment solution to the surface of the oxide film layer and heat-treating the solution (so-called solution method). This is desirable in that it can be performed simply and easily and can be mass-produced without increasing the manufacturing cost.

The solution for forming a polyimide resin film may be prepared by dissolving the polyimide resin itself, a monomer or oligomer used as a raw material of the polyimide resin in an organic solvent, if necessary. For example, bisallylnadiimide is a low molecular weight imide monomer having a bulky structure, and is soluble in most organic solvents except aliphatic hydrocarbons and aliphatic alcohols. A solution for forming a pyromellitic polyimide resin film is prepared by, for example, dissolving pyromellitic dianhydride and 4,4′-diaminodiphenyl ether in a highly polar solvent, N-methyl-2-pyrrolidone. I just need.

As a method of applying the polyimide resin film forming treatment solution to the surface of the oxide film layer, a dip coating method, a spray method, a spin coating method, or the like can be used.

The heat treatment after applying the polyimide resin film forming treatment solution to the surface of the oxide film layer is desirably performed at 200 ° C. to 400 ° C. If the temperature is lower than 200 ° C., the curing reaction may not proceed sufficiently, and if it exceeds 400 ° C., the coating may be deteriorated. The heat treatment time is usually 5 minutes to 24 hours. Before the heat treatment, a drying treatment for removing the organic solvent (for example, at a temperature of 60 ° C. to 90 ° C. for 5 minutes to 1 hour) may be performed, if necessary.

The formation of the polyimide resin film on the surface of the oxide film layer is not limited to a method of applying the above-mentioned treatment solution for forming a polyimide resin film to the surface of the oxide film layer and subjecting it to a heat treatment. Good. For example, in the case where a pyromellitic polyimide resin film is formed on the surface of the oxide film layer by vapor deposition polymerization, a magnet with an aluminum film having an oxide film layer on the surface may have a degree of vacuum of 1 Pa to 10 Pa.
^-3 Pa in a vacuum vessel, and pyromellitic dianhydride and 4,4′-diaminodiphenyl ether at 200 ° C.
A method of forming a polyamic acid film by heating and vapor-depositing at a temperature of from about 250 ° C. to about 250 ° C., and then performing an imidization treatment at 280 ° C. to 380 ° C. under normal pressure (see Japanese Patent Application Laid-Open No. 8-279407).

Since the polyimide resin film formed by the above method is firmly adhered to the surface of the aluminum film via the oxide film layer, if the film thickness is 1 μm or more, it exhibits excellent performance such as corrosion resistance. I do. The upper limit of the thickness of the polyimide resin film is not limited,
From the demand based on miniaturization of the magnet itself, it is preferably 15 μm or less, more preferably 10 μm or less. It is needless to say that the application of the polyimide resin film forming treatment liquid to the surface of the oxide film layer and the subsequent heat treatment may be repeated a plurality of times as necessary. Furthermore, in order to enhance the various performances (abrasion resistance, slipperiness, etc.) of the polyimide resin film, fine particles of a metal such as titanium or nickel, fine particles of a ceramic or metal oxide such as alumina or silica, and Teflon in the film. Fine particles of a synthetic resin such as (registered trademark) or various fine particles used as an organic pigment or an inorganic pigment may be dispersed. For example, a particle size of 1
By dispersing about 20% by weight of μm Teflon spheres, the slipperiness of the polyimide resin film can be improved. The size and shape of the fine particles to be added are appropriately selected in consideration of the performance and the thickness of the coating film to be formed, but fine particles having a particle size of 0.01 μm to 5 μm can be usually used.

The rare earth element (R) in the R—Fe—B permanent magnet used in the present invention is Nd, Pr, D
at least one of y, Ho, Tb, and Sm, or La, Ce, Gd, Er, Eu, Tm, Yb,
A material containing at least one of Lu and Y is desirable.
In general, one kind of R is sufficient, but in practice, a mixture of two or more kinds (such as misch metal and dymium) can be used for convenience and other reasons. R
-The content of R in the Fe-B-based permanent magnet is 10 atomic%.
If it is less than 1, the crystal structure becomes a cubic structure having the same structure as that of α-Fe, so that it has high magnetic properties, particularly high coercive force (HcJ).
On the other hand, if it exceeds 30 atomic%, the R-rich nonmagnetic phase increases, the residual magnetic flux density (Br) decreases, and a permanent magnet having excellent characteristics cannot be obtained. It is desirably about 30 at%.

If the Fe content is less than 65 atomic%, B
When r decreases and exceeds 80 atomic%, a high HcJ cannot be obtained. Therefore, the content of 65 to 80 atomic% is desirable.
Further, by substituting a part of Fe with Co, the temperature characteristics can be improved without impairing the magnetic characteristics of the obtained magnet. However, when the Co substitution amount exceeds 20 atomic% of Fe, the magnetic characteristics become poor. It is not desirable because it deteriorates. When the amount of Co substitution is 5 atomic% to 15 atomic%, Br increases in comparison with the case where no substitution is made, and thus it is desirable to obtain a high magnetic flux density.

If the content of B is less than 2 atomic%, the rhombohedral structure becomes the main phase, and a high HcJ cannot be obtained.
If it exceeds 0.005%, the B-rich non-magnetic phase increases, so that Br decreases and a permanent magnet having excellent characteristics cannot be obtained.
The content of about 28 atomic% is desirable. Further, in order to improve the manufacturability of the magnet and to reduce the price, the content of P of 2.0 wt% or less;
At least one of S at 0 wt% or less may be contained in a total amount of 2.0 wt% or less. Further, by replacing a part of B with 30 wt% or less of C, the corrosion resistance of the magnet can be improved.

Further, Al, Ti, V, Cr, Mn, B
i, Nb, Ta, Mo, W, Sb, Ge, Sn, Zr,
Addition of at least one of Ni, Si, Zn, Hf, and Ga is effective in improving the coercive force and the squareness of the demagnetization curve, improving the manufacturability, and reducing the cost. In order to set the maximum energy product (BH) max to 159 kJ / m ³ or more, Br is required to be at least 0.9 T or more. Therefore, it is preferable to add Br in a range that satisfies the condition. The R-Fe-B permanent magnet includes R, Fe, B
In addition to these, those containing impurities that are inevitable in industrial production may be used.

The R-Fe used in the present invention
-Among the B-based permanent magnets, the average crystal grain size is 1 μm to 80 μm.
The magnet having a main phase of a compound having a tetragonal crystal structure in the range of m and containing 1% to 50% by volume of a nonmagnetic phase (excluding an oxide phase) is HcJ ≧ 80k
A / m, Br> 0.4T, (BH) max ≧ 80 kJ /
indicates m ^3, the maximum value of (BH) max is 199kJ / m
Reaches ³ or more.

It is to be noted that another film may be laminated on the polyimide resin film of the present invention. By adopting such a configuration, the characteristics of the polyimide resin film can be enhanced or supplemented, and further functionality can be imparted.

[0039]

For example, as described in U.S. Pat. No. 4,770,723, 17Nd-1Pr obtained by pulverizing a well-known casting ingot, performing pulverization, forming, sintering, heat treatment and surface processing. -75Fe-7
The following experiment was performed using a sintered magnet having a B composition and a size of 23 mm × 10 mm × 6 mm (hereinafter referred to as “magnet test piece”). In the following experiments, the film thickness of the aluminum film, the film thickness of the oxide film layer, and the film thickness of the polyimide resin film were measured by observing the fracture surface with an electron microscope. The present invention is not limited to the application to the R-Fe-B based sintered magnet, but is also applicable to the R-Fe-B based bonded magnet.

Experimental Example 1: A magnet test piece was placed in a vacuum vessel, and the inside of the test piece was evacuated to 1 × 10 ⁻⁴ Pa or less.
Sputtering was performed for 15 minutes under the conditions of an Ar gas pressure of 10 Pa and a bias voltage of -400 V to clean the magnet surface. Next, an Ar gas pressure of 10 Pa and a bias voltage of -50
Under a condition of V and a magnet temperature of 250 ° C., metal ion was used as a target and arc ion plating was performed for 20 minutes to form an aluminum film on the magnet surface and allowed to cool. The thickness of the obtained aluminum film is 1.1 μm.
Met. The magnet with the aluminum coating obtained by the above method is immediately housed in the processing chamber, and subjected to an oxidation treatment at a temperature of 200 ° C. for 10 minutes under normal pressure with an oxygen concentration of 5% (for details, see Table 1). An oxide film layer was formed on the substrate. The thickness of the formed oxide film layer was 0.3 μm. BANI-
M (trade name, manufactured by Maruzen Petrochemical Co., Ltd.) was diluted to 20% (vol / vol) using toluene as an organic solvent to prepare a solution. This was applied by a spray method to the aluminum-coated magnet having an oxide coating layer on the surface obtained by the above method. Subsequently, after drying at 80 ° C. for 10 minutes, heat treatment was performed at 250 ° C. for 15 minutes to form a polyimide resin film on the surface of the oxide film layer. The film thickness of the formed polyimide resin film was 5 μm. A magnet having an aluminum coating on the surface and having a polyimide resin coating on the surface of the aluminum coating via the oxide coating layer obtained by the above method was subjected to high temperature and high humidity conditions of 70 ° C. × 90% relative humidity. The sample was allowed to stand below for an accelerated corrosion resistance test. As a result, no rusting or peeling of the film was observed even after 500 hours from the start of the test, indicating excellent corrosion resistance. When the electrical insulation was evaluated by volume resistivity (ρ),
An excellent value of 1 × 10 ¹⁵ Ω · cm or more was shown. The volume resistivity was determined by applying an electrode to the sample, measuring the resistance between the coating surface and the magnet, and calculating from the equation of ρ = R · S / l (R: resistance (Ω), S: electrode area ( cm ² ),
l: Polyimide resin film thickness (cm)). When the heat resistance was evaluated by the heat distortion temperature, an excellent value of 280 ° C. or more was shown. The heat deformation temperature was a temperature at which the film was left at that temperature for 20 hours in the air to cause discoloration, cracks and the like of the film.

Experimental Example 2 A film having a thickness of 10 μm was obtained under the same conditions as in Experimental Example 1 except that heat treatment was performed after coating and drying were repeated once again by the spray method.
m of a polyimide resin film was formed. The magnet having the aluminum coating on the surface obtained by the above method and having the polyimide resin coating on the surface of the aluminum coating via the oxide coating layer was subjected to a corrosion resistance acceleration test under the same conditions as in Experimental Example 1. Was. As a result, no rusting or peeling of the film was observed even after 500 hours from the start of the test, indicating excellent corrosion resistance. When the electrical insulation was evaluated by volume resistivity (ρ), it showed an excellent value of 1 × 10 ¹⁵ Ω · cm or more. When the heat resistance was evaluated by the heat distortion temperature, an excellent value of 280 ° C. or more was shown.

Experimental Example 3: Experimental example 1 for a magnet body test piece
Sputtering was performed under the same conditions as described above to clean the magnet surface. Next, under conditions of an Ar gas pressure of 1 Pa and a voltage of 1.5 KV, an aluminum wire was used as a coating material, which was heated and evaporated to be ionized, subjected to ion plating for 2.5 minutes, and an aluminum film was formed on the magnet surface. Formed and allowed to cool. The thickness of the obtained aluminum coating was 2 μm. Thereafter, spherical glass bead powder having an average particle size of 120 μm and a Mohs hardness of 6 was sprayed together with a pressurized gas consisting of N ₂ gas at an injection pressure of 1.5 kg / cm ^{2 for} 10 minutes.
In addition, shot peening was performed by spraying on the aluminum coating surface. The magnet with the aluminum coating obtained by the above method was immediately housed in the processing chamber, and under normal pressure with an oxygen concentration of 0.1% (for details, see Table 1) at a temperature of 250 ° C.
For 7 minutes to form an oxide film layer on the aluminum film surface. The thickness of the formed oxide film layer is 0.
It was 2 μm. Experimental Example 1 was applied to an aluminum-coated magnet having an oxide layer on the surface obtained by the above method.
A polyimide resin film having a thickness of 5 μm was formed under the same conditions as in Experimental Example 1 by using the same polyimide resin film forming treatment liquid as that used in Example 1. The magnet having the aluminum coating on the surface obtained by the above method and having the polyimide resin coating on the surface of the aluminum coating via the oxide coating layer was subjected to a corrosion resistance acceleration test under the same conditions as in Experimental Example 1. Was. As a result, no rusting or peeling of the film was observed even after 500 hours from the start of the test, indicating excellent corrosion resistance. When the electrical insulation was evaluated by volume resistivity (ρ), it showed an excellent value of 1 × 10 ¹⁵ Ω · cm or more. When the heat resistance was evaluated by the heat distortion temperature, an excellent value of 280 ° C. or more was shown.

Experimental Example 4 A film having a thickness of 10 μm was obtained under the same conditions as in Experimental Example 3 except that heat treatment was performed after coating and drying were repeated once by the spray method.
m of a polyimide resin film was formed. The magnet having the aluminum coating on the surface obtained by the above method and having the polyimide resin coating on the surface of the aluminum coating via the oxide coating layer was subjected to a corrosion resistance acceleration test under the same conditions as in Experimental Example 1. Was. As a result, no rusting or peeling of the film was observed even after 500 hours from the start of the test, indicating excellent corrosion resistance. When the electrical insulation was evaluated by volume resistivity (ρ), it showed an excellent value of 1 × 10 ¹⁵ Ω · cm or more. When the heat resistance was evaluated by the heat distortion temperature, an excellent value of 280 ° C. or more was shown.

Experimental Example 5: 100 magnet body test pieces (apparent capacity 0.35 liters, weight 1.1 kg) and a diameter of 0.
An 8 mm, 1 mm long, short cylindrical aluminum piece (20 liters in apparent capacity, 100 kg in weight) is charged into the processing chamber of a 50 liter vibrating barrel apparatus (total input volume is 30 vol% of the processing chamber volume), and the vibration frequency is 60 Hz. The treatment was performed dry for 7 hours under the condition of a vibration amplitude of 1.8 mm to form an aluminum coating on the magnet surface. The thickness of the obtained aluminum film was 0.2 μm. The magnet with the aluminum coating obtained by the above method is immediately accommodated in the processing chamber, and subjected to an oxidation treatment at a temperature of 180 ° C. for 6 minutes under normal pressure with an oxygen concentration of 0.2% (for details, see Table 1). An oxide film layer was formed on the surface of the film. The thickness of the formed oxide film layer was 0.1 μm. For the aluminum-coated magnet having an oxide film layer on the surface obtained by the above method, using the same polyimide resin film forming treatment liquid as used in Experimental Example 1, under the same conditions as in Experimental Example 1,
A polyimide resin film having a thickness of 5 μm was formed. The magnet having the aluminum coating on the surface obtained by the above method and having the polyimide resin coating on the surface of the aluminum coating via the oxide coating layer was subjected to a corrosion resistance acceleration test under the same conditions as in Experimental Example 1. Was. As a result, 5
No rusting or peeling of the coating was observed even after 00 hours,
It showed excellent corrosion resistance. When the electrical insulation was evaluated by volume resistivity (ρ), 1 × 10 ¹⁵ Ω · cm
The above values were excellent. When the heat resistance was evaluated by the heat distortion temperature, an excellent value of 280 ° C. or more was shown.

Experimental Example 6: Obtained in the same manner as in Experimental Example 1,
A magnet with an aluminum coating having a film thickness of 1.1 μm was immediately housed in the processing chamber, and was reduced under an oxygen pressure of 10 Pa (see Table 1 for details).
Oxidized at a temperature of 220 ° C. for 15 minutes to form an oxide film layer on the surface of the aluminum film. The film thickness of the formed oxide film layer was 0.6 μm. For the aluminum-coated magnet having an oxide film layer on the surface obtained by the above method, using the same polyimide resin film forming treatment liquid as used in Experimental Example 1, under the same conditions as in Experimental Example 1, A polyimide resin film having a thickness of 5 μm was formed. Having an aluminum coating on the surface obtained by the above method,
A magnet having a polyimide resin film on the surface of the aluminum film via an oxide film layer was subjected to a corrosion resistance acceleration test under the same conditions as in Experimental Example 1. As a result, no rusting or peeling of the film was observed even after 500 hours from the start of the test, indicating excellent corrosion resistance. In addition, when the electrical insulation was evaluated by volume resistivity (ρ), 1 × 10 ¹⁵ Ω ·
cm or more. When the heat resistance was evaluated by the heat distortion temperature, an excellent value of 280 ° C. or more was shown.

[0046]

[Table 1]

Comparative Example 1: Experimental Example 1 for a magnet test piece
Sputtering was performed under the same conditions as described above to clean the magnet surface. Next, arc ion plating was performed under the same conditions as in Experimental Example 1, an aluminum film was formed on the magnet surface, and the magnet was allowed to cool. The thickness of the obtained aluminum coating was 1.
It was 5 μm. Next, without forming an oxide film layer on the surface of the aluminum film, the same polyimide resin film forming treatment solution as used in Experimental Example 1 was used, and a polyimide film having a thickness of 5 μm was formed under the same conditions as in Experimental Example 1. A resin coating was formed directly. Obtained by the above method, having an aluminum coating on the surface, directly on the aluminum coating surface,
A magnet having a polyimide resin film was subjected to an accelerated corrosion resistance test under the same conditions as in Experimental Example 1. As a result, peeling of the film was observed 150 hours after the start of the test.

Comparative Example 2 A film having a thickness of 10 μm was obtained under the same conditions as in Comparative Example 1 except that heat treatment was performed after coating and drying were repeated once again by the spray method.
Was formed. The magnets having an aluminum coating on the surface and having a polyimide resin coating directly on the surface of the aluminum coating obtained by the above method were subjected to a corrosion resistance acceleration test under the same conditions as in Experimental Example 1.
As a result, film peeling was observed 250 hours after the start of the test.

Experimental Examples 7 to 12: Under the same conditions as in Experimental Examples 1 to 6, an aluminum film was formed on the surface of the magnet test piece, and an oxide film layer was formed on the surface. The same conditions and film thicknesses as in each experimental example except that a mixed solvent of toluene, ethyl acetate and cyclohexanone (volume ratio 65:15:20) were used instead of toluene used for preparing the polyimide resin film forming treatment solution in the examples. Thus, a polyimide resin film was formed on the surface of the oxide film layer. Each sample was subjected to the same corrosion resistance acceleration test, electrical insulation evaluation, and heat resistance evaluation as those of Experimental Example 1. As a result, all the samples showed the same results as those of the experimental examples.

[0050]

The permanent magnet according to the present invention has an aluminum coating on the surface of the R-Fe-B-based permanent magnet and has a polyimide resin coating on the aluminum coating surface via an oxide coating layer. However, due to the presence of the oxide film layer, it is firmly adhered to the surface of the aluminum film, and exhibits excellent corrosion resistance, electric insulation and heat resistance together with the aluminum film. In addition, since the polyimide resin film forming reaction proceeds efficiently on the oxide film layer, a polyimide resin film having excellent adhesion to the aluminum film surface can be formed by the solution method.

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Claims (14)

[Claims] 1. A permanent magnet having an aluminum coating on the surface of an R—Fe—B-based permanent magnet, and a polyimide resin coating on the surface of the aluminum coating via an oxide coating layer. 2. The permanent magnet according to claim 1, wherein the polyimide resin film is an addition type polyimide resin film. 3. The permanent magnet according to claim 2, wherein the addition type polyimide resin film is a film obtained from bisallylnadiimide. 4. The thickness of the aluminum film is 0.01 μm.
The permanent magnet according to any one of claims 1 to 3, wherein the thickness of the permanent magnet is from 50 to 50 m. 5. The oxide film layer has a thickness of 0.01 μm to 2 μm.
The permanent magnet according to any one of claims 1 to 4, wherein m is m. 6. The polyimide resin film has a thickness of 1 μm to 1 μm.
The permanent magnet according to any one of claims 1 to 5, wherein the permanent magnet has a thickness of 5 µm. 7. After forming an aluminum film on the surface of the R—Fe—B permanent magnet, an oxide film layer is formed on the surface of the aluminum film by an oxidation treatment in an oxygen atmosphere. A method for manufacturing a permanent magnet, comprising forming a polyimide resin film by applying a polyimide resin film forming treatment liquid and performing heat treatment. 8. The method according to claim 7, wherein the aluminum film is formed by a vapor growth method. 9. The method according to claim 8, wherein an aluminum film having a thickness of 0.01 μm to 50 μm is formed. 10. An R—Fe—B-based permanent magnet and an aluminum piece are placed in a processing container, and both are vibrated and / or agitated to form an aluminum coating in the processing container. The method according to claim 7, wherein: 11. The method according to claim 10, wherein an aluminum film having a thickness of 0.01 μm to 1 μm is formed. 12. The oxidation treatment in an oxygen atmosphere is carried out under normal pressure with an oxygen concentration of 0.01% to 20% or under reduced pressure with an oxygen pressure (partial pressure) of 0.1 Pa to 2 × 10 ⁴ Pa. ° C ~
The method according to claim 7, wherein the method is performed at 500 ° C. 12. 13. The method according to claim 7, wherein the polyimide resin film is an addition type polyimide resin film. 14. The production method according to claim 13, wherein the addition type polyimide resin film is a film obtained from bisallylnadiimide.