JPH11354361A - Rare earth magnet with good surface cleanliness and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve surface cleanliness by washing, while rubbing, the surface of a rare earth magnet coated with a corrosion resistant coat. SOLUTION: Firstly, surfaces 10a and 10b of a rare earth magnet 10 such as an R-T-B group anisotropic baked magnet are coated with a corrosion resistant coat such as Ni plating by a method such as barrel electrolytic Ni plating. Then, a sponge 20 of a rubbing member 30 is rotated while the surface of the sponge 20 is pressed against the surface 10a of the rare earth magnet 10, so that the rare earth magnet surface 10a is rubbed with the sponge 20 surface. At rubbing, the surface 10a is wetted with a pure water or a washing liquid wherein the pure water is added with a washing agent comprising an interfacial active agent, or both. Then, the rare earth magnet 10 is turned upside-down so that the rear surface 10b faces up, and the rear surface 10b is contacted with the sponge 20 for rubbing in the same way. Thus, the particles sticking to the front surface 10a and the rear surface 10b are removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface cleanness useful for a high-precision positioning drive of a recording / reproducing head mounted on a recording / reproducing apparatus of a magnetic type, a magneto-optical type, an optical type, etc. The present invention relates to a good rare earth magnet and a method for manufacturing the same.

[0002]

2. Description of the Related Art R-T-B rare earth permanent magnets (R is one or more rare earth elements including Y, T is Fe or Fe and Co) have excellent magnetic properties and excellent cost performance. For this reason, rare earth magnets are currently the mainstream. A general R-T-B rare earth permanent magnet,
-T-B based rare earth sintered magnets are manufactured by pulverizing, shaping and sintering an alloy lump produced by melting or the like and then heat-treating, processing and surface-treating or processing, heat-treating and surface-treating. Due to the poor properties, a process of coating the surface with a corrosion-resistant film is performed. In particular, a highly reliable Ni plating or the like is essential for use in a recording / reproducing device such as a hard disk drive.

[0003] Further, an RTB-based rare earth magnet obtained by a casting / hot working (rolling) method other than the sintering method (for example, JP-A-6-302419, JP-A-64-704, etc.), Using a ribbon obtained by the super-quenching method, the density is increased by hot pressing or the like, and then plastically deformed in the warm state to make R anisotropic.
-TB rare earth magnets (for example, see JP-A-64-7504).
Also, Ni plating and the like are indispensable.

However, a large number of fine particles adhere to the surface of the rare earth magnet coated with Ni plating or the like, and the recording / reproducing error occurs in a recording / reproducing apparatus due to the adhered particles.
R-T-B used for applications such as voice coil motor (VCM) for hard disk drives
It is desired that the rare earth magnets have good surface cleanliness and minimize the attachment of ferromagnetic fine particles. The means for improving the surface cleanliness is generally, for example, ultrasonic cleaning in pure water.

[0005]

The adhered particles which cause a recording / reproducing error are mainly ferromagnetic fine powders produced in the process of manufacturing an RTB-based rare earth magnet. -It is one which is attached to the surface of the TB rare earth magnet in a free state.

More specifically, ferromagnetic particles having a circle-equivalent diameter of about 1 to 50 μm in area approximation obtained by image processing of a photograph taken of the state of adhesion by a scanning electron microscope or the like poses a problem.

For example, fine particles of RTB-based rare earth magnets generated by collision of magnets before coating with a corrosion-resistant coating or collision between coatings of Ni plating, etc., accompanying Ni plating Ni fine particles and the like that are generated as a result.
Although it is possible to reduce the amount of particles attached to the surface to some extent by conventional ultrasonic cleaning in pure water that has not been degassed,
It is difficult to cope with high surface cleanliness required with the increase in recording density.

In particular, fine powder particles of rare earth magnets, such as fine powder particles of RTB-based rare earth magnets, have a strong magnetic attraction, so that they are sufficiently removed by the conventional washing in pure water. It was difficult.

[0009] Further, since the Ni particles are generated in a form of falling off the Ni plating layer, some of the Ni particles are coming off in addition to those completely falling off the Ni plating layer. For this reason, the adhesion of the Ni particles is not uniform, and it has been difficult to remove these particles to obtain a clean surface state in which the recording / reproducing error is not a problem.

If these particles are used while being adhered to the surface of the rare earth magnet, there is a concern that recording / reproducing errors of a hard disk or the like may be induced. Rare earth magnets used for such purposes must have good surface cleanliness.

An object of the present invention is to provide a rare-earth magnet having a high surface cleanness incorporated in a high-precision positioning drive of a recording / reproducing head of a recording / reproducing apparatus of any of a magnetic type, a magneto-optical type and an optical type. It is to provide a manufacturing method thereof.

[0012]

Means for Solving the Problems In order to obtain a rare earth magnet having a high surface cleanliness coated with a corrosion resistant film,
Attachment particles, especially fine powder particles of rare earth magnets, including fine powder particles of RTB based rare earth magnets having a strong attraction force, N
As a result of intensive studies on a method of reducing the adhesion of ferromagnetic fine particles such as Ni particles dropped from the i-plated layer, it was found that the rare-earth magnet was coated with a corrosion-resistant coating and washed while being rubbed, or the rare-earth magnet was removed. The surface of the corrosion-resistant coating layer is cleaned by ultrasonic cleaning in pure water or a cleaning solution containing a surfactant, or by using both cleaning methods in combination, to obtain a rare-earth magnet with high surface cleanliness. It has been found that the present invention has been achieved.

In the present invention, the surface of the rare earth magnet coated with the corrosion resistant coating is cleaned by rubbing with a rubbing member capable of rubbing the surface of a brush or the like. By using a rubbing member,
Compared to the case of conventional ultrasonic cleaning in pure water that has not been degassed, the ability to remove particles adhered to the surface can be increased, and a high cleaning ability can be obtained.

Further, by using an elastic body having high elasticity as the rubbing member, it is easy to adjust the rubbing force on the rare earth magnet surface during cleaning. In particular, by using a brush and / or a sponge, it is possible to secure a reliable contact and rubbing force corresponding to the irregularities on the surface of the rare-earth magnet, and to prevent the surface of the rare-earth magnet from being damaged by this rubbing operation.

The material and shape of the brush and sponge may be any material that does not damage the surface of the rare earth magnet and that does not contaminate the surface of the rare earth magnet during rubbing. For example, polyamide and PVA materials are used. can do. In addition, by using a rotary motion for the rubbing operation, the number of rubs and the rubbing time can be substantially increased, and a high cleaning ability can be obtained.

The mechanism of the rotary rubbing movement of the rubbing member is not particularly limited. For example, a mechanism having a rotation axis perpendicular or parallel to the surface of the rare earth magnet can be used.
The procedure for cleaning each surface of the rare-earth magnet is not particularly limited, but a method of cleaning one surface and then cleaning another surface by a displacement operation such as inversion and movement, and simultaneously cleaning each surface with a plurality of rubbing members. A method, a method of cleaning each surface by a displacement operation of the rubbing member, or the like can be applied.

Further, a rubbing member such as a brush and a sponge
It can be used alone, singly or once, but one or more types can be used to enhance the cleaning ability.
It is possible to increase the cleaning ability by contacting and cleaning one or two or more, one or two or more times in combination.

The cleaning conditions, such as the cleaning time and the number of revolutions, are determined according to the desired surface cleanliness of the rare earth magnet to be cleaned. The cleaning needs to be performed by rubbing the rubbing member in a state where the surface of the object to be cleaned is wet with a liquid in order to obtain appropriate lubricity and promote removal of adhered particles.

For cleaning, it is preferable to use pure water from the viewpoint of environment and handling. Further, a cleaning liquid containing a surfactant is more preferable, and the wettability of cleaning the surface of the rare earth magnet is improved, and the release of adhered particles is prevented and reattachment is prevented, thereby improving the cleaning ability.

According to the present invention, a sufficient cleaning ability can be obtained, but other cleaning methods such as ultrasonic cleaning, jet water cleaning and the like can be performed as pre- and / or post-treatments. In particular, in the case where a cleaning agent containing a surfactant is added to pure water for cleaning, in order to remove the cleaning agent remaining in the cleaning section, ultrasonic cleaning with pure water and / or jet water cleaning after cleaning in the present invention, etc. It is preferable to add a washing step. The method of drying after washing is not particularly limited, and for example, drying with warm air at room temperature to 100 ° C, drying under heating and reduced pressure, and the like can be applied.

In the present invention, the surface of the rare earth magnet coated with the corrosion resistant film is ultrasonically cleaned in degassed pure water. By degassing the pure water, the effect of ultrasonic cleaning is enhanced,
Compared with conventional ultrasonic cleaning using pure water that has not been degassed, the total number of particles adhering to the surface and the ratio of ferromagnetic particles can be reduced.

As the degassed pure water, it is preferable to use one having a dissolved oxygen content of 50% or less of the saturated dissolved oxygen content in order to enhance the effect of removing adhered particles by washing. The method of degassing is not particularly limited. For example, the cleaning device according to the present invention can be miniaturized by utilizing degassing under reduced pressure, in particular, depressurized degassing by aspiration.

When the cleaning liquid obtained by adding a cleaning agent containing a surfactant to pure water is degassed and then subjected to ultrasonic cleaning, the wettability of the cleaning liquid on the surface of the rare earth magnet coated with the corrosion resistant coating is reduced. In addition to the improvement, the release of the adhered particles is promoted and the re-adhesion is prevented, thereby improving the cleaning ability.

The arrangement and the number of the ultrasonic transducers with respect to the rare earth magnet coated with the corrosion-resistant coating as the object to be cleaned are not particularly limited.
Or it can be arranged on the upper side. In order to obtain uniform surface cleanliness, it is preferable to arrange the ultrasonic transducers symmetrically on the upper and lower sides.

The cleaning conditions, such as the intensity of the ultrasonic wave, are selected according to the surface cleanliness of the rare earth magnet to be cleaned. According to the present invention, a sufficient cleaning ability is obtained, but it is also possible to combine other cleaning methods with the pre-processing and / or post-processing.

When cleaning is performed using a cleaning liquid obtained by adding a cleaning agent containing a surfactant to pure water, ultrasonic cleaning with pure water, jet cleaning, and jetting are performed to remove the cleaning agent remaining in the cleaning section. It is preferable to add washing steps such as water washing and shower washing. The drying method after the washing is not particularly limited, and for example, hot air drying, heating and drying under reduced pressure can be applied.

In order to achieve a good washing action, the washing solution containing a surfactant used in the present invention is used in an amount of 0.1 to 10% by volume of soap or various synthetic detergents with respect to pure water or degassed pure water. It can be prepared by adding a detergent (detergent) containing the above surfactant as a main component. If the content of the cleaning agent in the cleaning liquid is less than 0.1% by volume, the cleaning improvement effect is not recognized,
If the content exceeds 10% by volume, the removal of the detergent requires a large number of post-cleaning steps, and the adhesive strength of the finally obtained rare earth magnet may undesirably decrease due to the detergent remaining on the surface.

As the synthetic detergent, a detergent containing a surfactant as a main component produced by the synthesis of sodium alkylbenzene sulfonate, sodium alpha olefin sulfonate and the like can be used. In particular, it is preferable to use a detergent containing a phosphoric acid-based neutral surfactant as a main component for rust prevention.

Further, the cleaning solution of the present invention comprises the following surfactants and chemical detergents in a total amount of 0.1 to 0.1 with respect to the pure water.
It can be prepared by adding 10% by volume of a composite. As the surfactant, for example, any of an anionic surfactant, a cationic surfactant, an amphoteric surfactant, and a nonionic (neutral) surfactant can be used.

As the chemical detergent, for example, any of soda salts, silicates and phosphates can be used. In particular, sodium phosphates (NaH ₂ PO ₄ ) and sodium phosphates (Na ₂ H), which are chemical detergents for phosphates, are used.
PO ₄ ), sodium tertiary phosphate (Na ₃ PO ₄ ), sodium tripolyphosphate (Na ₅ P ₃ O ₁₀ ), sodium pyrophosphate (Na ₄ P ₂ O ₇ ), sodium hexametaphosphate (NaP
Any of O ₃ ) ₂ is preferable for rust prevention (anti-oxidation) at the time of cleaning and improvement of surface cleaning.

In the combination of the surfactant and the chemical detergent, the neutral surfactant and any one of the phosphate-based chemical detergents are combined in a total amount of 0.1 to 10% by volume with the pure water. The washing solution added to the above is preferable.

The volume ratio of the surfactant and the chemical detergent in the cleaning solution is preferably in the range of 30 to 70:70 to 30 in order to prevent rust and improve surface cleanliness.

As the surfactant used in the present invention, any of conventionally used anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants can be used. Good.

The present invention is particularly directed to an RTB-based rare earth magnet body having an R ₂ T ₁₄ B type intermetallic compound as a main phase (R is one or more rare earth elements including Y, and T is Fe or F
e and Co) are effective for cleaning the surface of an RTB-based magnet whose surface is coated with electrolytic plating and / or electroless plating.

Before electrolytic plating and / or electroless plating, the rare-earth magnet is treated with an acidic solution using a strong acid such as sulfuric acid or hydrochloric acid in order to remove the deteriorated layer of the rare-earth magnet and activate it before plating. It is better to do. In particular,
The first etching with 10% by volume of nitric acid, followed by the second etching with a mixed acid composed of 5 to 10% by volume of hydrogen peroxide, 10 to 30% by volume of nitric acid and the balance of pure water is preferable.

Subsequently, as the electrolytic plating, for example, single-layer Ni plating using a Watt bath can be adopted. Further, a Ni plating layer composed of a matte Ni layer and a glossy Ni layer sequentially formed on the surface of the rare earth magnet body (for example, see Japanese Patent No. 2599753) can be adopted.

Electrolytic Ni strike plating using a Watt bath formed sequentially on the surface of the rare earth magnet body, electrolytic Cu plating using a Cu pyrophosphate bath, electrolytic Ni plating using a Watt bath
Three-layer plating consisting of plating (for example,
26) may be used.

The average total thickness of these corrosion resistant coatings is 10 to 2
5 μm is preferred. If it is less than 10 μm, it is difficult to impart sufficient corrosion resistance, and if it exceeds 25 μm, flux loss and magnetic force decrease due to an increase in the gap to the yoke or the like are caused.

Either one of the above-described single-layer Ni plating, a Ni plating layer composed of a matte Ni plating layer and a glossy Ni plating layer, and three-layer plating of Ni plating / Cu plating / Ni plating by electroless plating. Can be. Also,
Ni-P plating by electroless can be adopted. Similar to the above, the average total thickness of the electroless plating is preferably 10 to 25 μm.

In the case of a multilayer plating structure, electrolytic plating and electroless plating may be used in combination. Also,
A chromate treatment in which the plated material is immersed in an aqueous solution of chromate and then dried, or an alkali treatment in which the chromated material is immersed in a solution of NaOH or KOH, washed with water, and dried, can also be performed.

The present invention can of course be applied to a rare earth magnet coated with a known corrosion-resistant coating other than the above.

Next, in the present invention, the method of cleaning the surface by rubbing the rubbing member such as the brush and the ultrasonic cleaning using a deaerated water or a cleaning liquid containing a surfactant are combined. It was found that the synergistic effect of both cleaning methods significantly improved the surface cleanliness.

According to the method for producing a rare earth magnet having good surface cleanliness of the present invention, the total number of adhered particles, Nd-Fe-
Both the fine powder particles of rare earth magnets, such as the fine powder particles of B-based magnets, and the number of adhered ferromagnetic fine particles such as Ni particles can be greatly reduced.

In order to suppress recording / reproducing errors, it is necessary to first reduce the total number of adhered particles, and it is preferable that the total number be 250 or less per 10 cm ² of the rare earth magnet surface of the present invention.
More preferably, it is 200 pieces / 10 cm ² or less.

Permanent magnet fine powder particles such as Nd-Fe-B magnet powder particles (1 to 50 μm in the circle equivalent diameter described above)
m), the total number of adhered particles is 250 particles / 10 cm ²
It is preferable that the ratio to the total number of the adhered particles is 1.0% or less after being suppressed to the following.

It is desirable that the number of ferromagnetic particles including Ni particles (the above-described one having a circle equivalent diameter of 1 to 50 μm) is 70% or less, preferably 50% or less, based on the total number of adhered particles. In particular, it is preferable that the number of fine powder particles attached to the permanent magnet is 1 or less per 10 cm ² .

[0047]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be specifically described below with examples, but the present invention is not limited to these embodiments.

(Embodiment 1) In this embodiment, the surface of a rare earth magnet whose surface is covered with a corrosion-resistant coating is rubbed with a rubbing member such as a rotary brush, and the surface is rubbed with the rubbing member. A rare-earth magnet having good surface cleanliness by removing particles adhered to the surface of the rare-earth magnet and improving the surface cleanliness of the rare-earth magnet will be described.

The rare earth magnet of the present embodiment is:
It may be a sintered magnet or a magnet other than a sintered magnet. For example, a material suitable for VCM, such as an RTB-based anisotropic sintered magnet having an R ₂ T ₁₄ B type intermetallic compound as a main phase, may be mentioned.

For example, in such an RTB-based anisotropic sintered magnet, first, a metal raw material is mixed, melted and cast in accordance with a required composition, and then an ingot of an RTB-based magnet alloy is cast. Get.
The production of such an ingot may be performed by a conventionally known production method, for example, by producing a strip-shaped alloy piece by a strip casting method or the like.

Thereafter, the magnet alloy piece is spontaneously disintegrated after absorbing hydrogen under appropriate conditions to coarsen powder, and then sieved to about 32 mesh under. Thereafter, the obtained coarse powder is finely pulverized in an inert gas by a jet mill, and then molded in a magnetic field, and the obtained molded article having a predetermined shape is sintered at a predetermined temperature.

After sintering, machine processing, heat treatment or heat treatment, and machine processing are performed on barrel processing (chamfering processing).
Then, after performing a plating pretreatment, the surface of the magnet body is coated with Ni plating as a corrosion-resistant coating by a method such as barrel electrolytic Ni plating. After coating, the RT attached to the Ni plating surface
-Attaching particles including ferromagnetic particles such as fine powder particles and Ni fine particles of a B-based magnet are removed by rubbing the surface to produce a rare-earth magnet having good surface cleanliness.

In this embodiment, as shown in FIG. 1, when the surface of the rare earth magnet 10 is rubbed,
0 was performed using a rubbing member 30 configured to be rotatable. The sponge 20 (for example, made of PVA) has a thickness sufficiently larger than the thickness of the rare-earth magnet 10, is formed in a substantially hollow cylindrical shape (disk shape) with a hollow portion 21 provided in the center,
A rotation shaft 23 is provided at the center of the substantially hollow cylindrical surface via a sponge support portion 22 and is rotatable.

The rotating shaft 23 may be configured so that the motor can be rotated by a conventionally known mechanism (not shown) so that the number of rotations can be adjusted.

The sponge 20 of the rubbing member 30 having such a configuration
As shown in FIG. 1, the surface of the sponge 20 is pressed against the surface 10a of the rare-earth magnet 10 while the surface is rotated, and the surface 10a is rubbed with the sponge 20 surface. When rubbing,
The surface 10a is pure water, or a cleaning liquid containing a detergent containing a surfactant added to the pure water (a diluted solution of a detergent containing a surfactant in pure water), or a combination of the two,
0a is preferably performed in a wet state.

Thus, the particles adhering to the surface 10a are removed by the rubbing of the sponge 20.
After rubbing the surface 10a as described above, the rare-earth magnet 10
Is turned upside down, the back surface 10b is turned to the front side, and the sponge 20 is brought into contact with the back surface 10b and rubbed, whereby the adhered particles on both surfaces can be removed.

The peripheral end face 10 of the rare earth magnet 10
c, as shown in FIG. 1, when the sponge 20 is pressed against the front surface 10a or the back surface 10b, the soft / sponge 20 is appropriately distorted, and the inner / outer peripheral surface 10d is appropriately distorted.
Since it also contacts the inner / outer peripheral surface 10d, these 10c surfaces,
The 10d surface is simultaneously rubbed to remove the adhered particles on the 10c surface and the 10d surface.

When a cleaning agent is used for the rubbing, the cleaning agent is removed from the surface by removing pure particles after removing the adhered particles, and dried with warm air.

As the rubbing member, a rubbing member other than the sponge 20 may be used. For example, as shown in FIG. 2, a rotating shaft 33 is provided at a center of a brush 31 formed in a substantially hollow cylindrical shape via a brush supporting portion 32 to form a rotating brush 40.
And the rare earth magnet 50 may be rubbed. The brush 31 may be made of, for example, a synthetic resin material such as polyamide or PVA.

The material of the sponge 20 and the brush 31, the number of rotations during rubbing, the pressing force, and the like may be appropriately set so as not to damage the corrosion-resistant coating such as Ni plating. Further, when the surface of the rare earth magnet is flat, other than the sponge or brush, for example, a nonwoven fabric may be provided on a rotatable disk surface to remove adhered particles with the nonwoven fabric.

In the above description, the case of Ni plating as the corrosion-resistant coating applied to the rare-earth magnet has been described. However, it is needless to say that the present invention is also effective when a corrosion-resistant coating other than the above-described Ni plating is coated.

In the above description, the rubbing means for rotating the sponge 20 or the brush 31 by the motor has been described. However, in some cases, the brush may be held in hand to rub the surface of the rare-earth magnet. Further, in a factory or the like, a plurality of rotating rubbing members are provided in the middle of a line using a belt conveyor or the like, and while the plurality of rare earth magnets flow through the line, the adhered particles are removed by the rubbing members. It can also be configured as follows.

In the above description, the case where the sponge 20 and the brush 31 are individually used as the rubbing members has been described. However, the sponge 20 and the brush 31 may be used in combination.

For example, initially, a brush 31 made of a material relatively harder than the sponge 20 is used to remove large adhered particles, and then the sponge 20 which is softer than the brush 31 and has a higher degree of adhesion to the surface is used. Alternatively, finely adhered particles may be removed.

If the relatively large adhered particles are removed from the beginning using the brush 31, even if the sponge 20 is used thereafter, it is necessary to keep the large adhered particles in the sponge 20 having high adhesion. As described above, the surface does not need to be rubbed, which is effective in preventing the corrosion-resistant coating from being damaged.

The present embodiment will be described more specifically with reference to the following examples.

(Example 1) Flat VCM coated with electrolytic Ni plating (average film thickness: 20 μm) as a corrosion resistant film
Nd-Fe-B based sintered magnet for nylon brush 3 while dropping pure water in substantially the same manner as shown in FIG.
1 was rotated to wash. The brush 31 was rotated on a rotation axis perpendicular to the cleaning surface, and cleaning was performed under the conditions of a rotation speed of 200 rpm and a cleaning time of 10 seconds. After washing, it was rinsed with pure water and dried with warm air.

A conductive adhesive tape was stuck on the washed surface of the dried Nd-Fe-B sintered magnet, and the attached particles were transferred to the conductive adhesive tape.

In this transfer operation, an operation of attaching a conductive adhesive tape of a predetermined size to the washed arbitrary surface and transferring the adhered particles to the conductive adhesive tape is performed once, and then the conductive adhesive tape is removed. The second transfer is performed by attaching to an untransferred arbitrary cleaning surface, and then finally using the same conductive adhesive tape of the predetermined size to the above-mentioned cleaned untransferred arbitrary cleaning surface. A total of 10 transfers were performed.

Next, particles having a circle equivalent diameter of 1 μm or more in the area of 1 cm × 1 cm of the conductive pressure-sensitive adhesive tape after the tenth transfer (all the adhered particles had a circle equivalent diameter of 1 to 50 μm). Was counted and analyzed by SEM / EDX.

That is, the above-mentioned washed Nd-Fe
Particles adhering to the surface 10 cm ² of -B based sintered magnet means that it is transferring.

As shown in Table 1, the total number of adhered particles per 10 cm ² of the surface
-Both the number of particles of the Fe-B based magnet and the number of Ni particles were very small, and a rare earth magnet having good surface cleanliness was obtained.

(Example 2) In the same manner as in Example 1, as shown in FIG. 2, a Ni plating coating Nd composed of an electrolytic matte Ni plating layer and an electrolytic gloss Ni plating layer (average total thickness 20 μm) 1% by volume in pure water for Fe-B based sintered magnet
The nylon brush 31 was rotated while the cleaning solution to which the detergent containing the surfactant was added was added dropwise to perform cleaning.

The brush 31 was rotated on a rotation axis perpendicular to the cleaning surface, and the cleaning was performed under the conditions of a rotation speed of 200 rpm and a cleaning time of 10 seconds. After the cleaning, the substrate was subjected to ultrasonic cleaning with pure water for 5 minutes and then dried with warm air.

The state of the adhered particles on the washed arbitrary surface of the dried Nd—Fe—B sintered magnet was counted and analyzed by SEM / EDX in the same manner as in Example 1, and the results were as follows:
It is shown in Table 1. Table 1 shows that this example is also a rare earth magnet having good surface cleanliness.

(Example 3) Strike Ni plating / Cu plating / Ni plating by electrolysis (average total thickness 20 μm)
Into a three-layer plated Nd-Fe-B sintered magnet, which is sequentially coated from the surface side of the Nd-Fe-B based sintered magnet body,
The washing was performed by rotating the PVA sponge 20 in substantially the same manner as shown in FIG. 1 while dropping a washing solution obtained by adding a washing agent containing 1% by volume of a surfactant to pure water.

The sponge 20 was rotated on a rotation axis perpendicular to the cleaning surface, and the cleaning was performed under the conditions of a rotation speed of 200 rpm and a cleaning time of 10 seconds. After the cleaning, the substrate was subjected to ultrasonic cleaning with pure water for 5 minutes and then dried with warm air.

The state of the adhered particles on the washed arbitrary surface of the Nd—Fe—B sintered magnet dried after washing was counted and analyzed by SEM / EDX in the same manner as in Example 1. As a result, as shown in Table 1, a rare-earth magnet having good surface cleanliness substantially similar to that of the above example was obtained.

Next, the following comparative experiments were performed as Comparative Examples 1 and 2 in order to compare with Examples 1 to 3 described above.

(Comparative Example 1) In Comparative Example 1, using the same Ni-plated Nd-Fe-B-based sintered magnet as in Example 1, adhesion was performed on an uncleaned arbitrary surface without going through a cleaning step. The state of the particles was changed to SEM / ED in the same manner as in Example 1.
It was counted and analyzed by X. Table 1 shows the results. As shown in Table 1, Comparative Example 1 shows that the total number of adhered particles and Nd-
The number of particles and the number of Ni particles of the Fe-B-based magnet were as shown in Table 1, indicating that the surface cleanliness was very poor.

(Comparative Example 2) In Comparative Example 2, degassing was performed using an electrolytic Ni-plated Nd-Fe-B-based sintered magnet made of the same matte Ni plating and bright Ni plating as in Example 2. Not pure water (dissolved oxygen content is 9% of saturated dissolved oxygen content)
(0%) for 20 minutes, followed by hot air drying.
The state of the adhered particles on an arbitrary surface of the dried product was counted and analyzed by SEM / EDX in the same manner as in Example 1.

The results are as shown in Table 1 below.
Both the number of particles and the number of Ni particles of the Nd—Fe—B-based magnet were much larger than in Example 2, and the surface cleanliness was very poor.

[0083]

[Table 1]

(Embodiment 2) In this embodiment, a cleaning solution containing a detergent containing a surfactant added to pure water or pure water obtained by degassing a rare earth magnet whose surface is covered with a corrosion resistant film is used. A rare-earth magnet with good surface cleanliness that has been ultrasonically cleaned using the method and a method for manufacturing the same will be described.

The rare earth magnet of the embodiment is also
This is a rare earth magnet similar to that of the first embodiment.

Particles containing ferromagnetic particles such as RTB-based magnet powder particles and Ni particles adhere to, for example, the Ni-plated surface of such a rare-earth magnet.
Ultrasonic cleaning is performed using a cleaning solution containing pure water or a surfactant that is degassed to a dissolved oxygen content of 50% or less of the saturated dissolved oxygen content, thereby increasing the surface cleanliness of the rare earth magnet.

As the ultrasonic cleaning device used for such cleaning, a conventional cleaning device may be used. Degassed pure water or the above-mentioned cleaning liquid in which the dissolved oxygen amount is suppressed to 50% or less of the saturated dissolved oxygen amount by degassing under reduced pressure such as aspiration is put into the washing tank. A rare earth magnet with particles adhered to the surface is put into deaerated pure water in the cleaning tank or the above-mentioned cleaning liquid, and cleaning is performed by ultrasonic waves. After washing, it may be dried with warm air.

As the degassed cleaning liquid, a cleaning agent containing a surfactant may be added to pure water and used after degassing. Alternatively, the surface of the rare earth magnet may be wetted with a detergent containing a surfactant diluted to an appropriate concentration, and then placed in degassed pure water for ultrasonic cleaning.

Further, after adding a detergent containing a surfactant to pure water, a rare earth magnet whose surface has been wetted with the detergent containing a surfactant diluted as described above is added to the degassed washing solution. Ultrasonic cleaning may be used.

In any of the above cases, when a detergent containing a surfactant is used, after the ultrasonic cleaning, the substrate is rinsed by ultrasonic cleaning with ordinary pure water to which no detergent is added. Therefore, it is necessary to remove the detergent. After rinsing, it may be dried with warm air. At the time of rinsing, means such as jet water washing, shower washing, etc. may be used, and further, rubbing and washing means using a brush may be used in combination, and it is essential that the washing agent can be sufficiently removed. I just need.

When applying ultrasonic waves in the cleaning tank, the ultrasonic vibrator for generating ultrasonic waves may be installed on the lower side of the rare earth magnet, on the upper side, or on both the upper and lower sides. However, in order to obtain uniform cleanliness, it is preferable to arrange them symmetrically on the upper and lower sides.

(Example 4) Nd-Fe as a corrosion resistant film
Strike Ni plating / Cu plating / Ni plating (average total thickness 2
(0 μm) and a flat-shaped Nd—Fe—B-based sintered magnet for VCM coated with three layers and sequentially coated on a stainless steel net, and subjected to ultrasonic cleaning in degassed pure water for 3 minutes. . The amount of dissolved oxygen in the degassed pure water is 1.8 m at 27 ° C.
g / l (23% of the amount of saturated dissolved oxygen).

After the washing, the substrate was further rinsed with pure water and dried with warm air. The condition of the adhered particles on an arbitrary surface of the dried Nd—Fe—B based sintered magnet was set to SE in the same manner as Example 1.
It was counted and analyzed by M / EDX.

As shown in Table 2, the total number of adhered particles, the number of particles of the Nd-Fe-B-based magnet powder, and the number of Ni particles were very small, and the Nd-Fe-B-based baked material having a good surface cleanliness was obtained. A magnet was obtained.

(Example 5) A detergent containing 1% by volume of a surfactant (Dia Kite PD.
Example 2 The cleaning solution consisting of M3) and the remaining pure water was degassed, and
A Nd-Fe-B-based sintered magnet coated with Ni plating, consisting of a non-glossy plating Ni plating layer and a gloss plating layer (average total thickness 20 µm) by the same electrolysis as above, was placed on a stainless steel net and subjected to ultrasonic cleaning for 3 minutes. . The dissolved oxygen content of the degassed cleaning solution was 2.0 mg / l at 28 ° C. (26% of the saturated dissolved oxygen content). After the cleaning, the substrate was subjected to ultrasonic cleaning for 3 minutes with pure water (dissolved oxygen content is 90% of saturated dissolved oxygen content) which had not been degassed, and then dried with warm air.

The state of the adhered particles on an arbitrary surface of the dried product was counted and analyzed by SEM / EDX in the same manner as in Example 1.

As shown in Table 2, the contaminant particles were further reduced as compared with Example 4, indicating that the cleaning method of the present invention has a high cleaning ability.

Further, the following comparative experiments were performed as Comparative Examples 3 and 4 in order to compare with the above Examples 4 and 5.

(Comparative Example 3) In Comparative Example 3, the uncleaned three-layer plating coating V before being subjected to the ultrasonic cleaning in Example 4 was used.
The state of the adhered particles on an arbitrary surface of the Nd—Fe—B sintered magnet for CM was counted and analyzed by SEM / EDX in the same manner as in Example 1.

As shown in Table 2, the total number of adhered particles, the number of particles of the Nd-Fe-B magnet, and the number of Ni particles were much larger than those of Examples 5 and 6.

Comparative Example 4 In Comparative Example 4, the same three-layer plating-coated Nd—Fe—B sintered magnet as in Example 4 was used in pure water without degassing (dissolved oxygen content is saturated dissolved oxygen content). 92%)
After performing ultrasonic cleaning for 6 minutes, hot air drying was performed. The state of the adhered particles on an arbitrary surface of the dried product was counted and analyzed by SEM / EDX in the same manner as in Example 1.

The results are as shown in Table 2 below.
Both the number of particles and the number of Ni particles of the Nd—Fe—B-based magnet were much larger than those of Example 4 or 5, indicating that the surface cleanliness was very poor.

[0103]

[Table 2]

(Embodiment 3) In the present embodiment, the cleaning method by rubbing the surface with the rubbing member described in the first embodiment and the deaerated pure water or the deaerated water described in the second embodiment will be described. A rare earth magnet with good surface cleanliness was manufactured by combining the cleaning method with ultrasonic cleaning using a cleaning liquid.

After cleaning with a rubbing member using a sponge, ultrasonic cleaning using deaerated pure water or a cleaning liquid may be performed, or cleaning with a rubbing member using a brush and this ultrasonic cleaning may be used. Even with the combination of the above, better results were obtained than when each of the washing methods was used alone.

Further, the present inventors have proposed a cleaning method using a rubbing member composed of a brush, a cleaning method using a rubbing member composed of a sponge, and an ultrasonic cleaning method using deaerated pure water or a cleaning liquid. It has been found that the combination of the method and the method can more effectively reduce the attached particles. Hereinafter, the details thereof will be specifically described with reference to the sixth embodiment.

(Example 6) Using a flat Nd-Fe-B sintered magnet for VCM coated with Ni plating as a corrosion-resistant film, nylon The cleaning was performed using a brush made under the conditions of a rotation speed of 200 rpm and a cleaning time of 10 seconds. The nylon brush was provided such that a rotating shaft was provided in a direction perpendicular to the cleaning surface on the surface of the rare earth magnet, and the cleaning surface was rubbed against the nylon brush surface.

Thereafter, in the same manner as in Example 3, cleaning was performed using a sponge under the conditions of a rotation speed of 200 rpm and a cleaning time of 10 seconds. The sponge surface was rubbed against the cleaning surface of the rare earth magnet surface.

Using the rare-earth magnet thus cleaned by rubbing with both the brush and the sponge, a cleaning agent containing 1% by volume of a surfactant was added to pure water in the same manner as in Example 5. The cleaning solution obtained by adding was degassed and placed on a stainless steel net in a cleaning tank filled with the degassed cleaning solution. The dissolved oxygen content of the degassed washing liquid was 30% of the saturated dissolved oxygen content.

Under such conditions, ultrasonic cleaning was performed for 3 minutes. Thereafter, ultrasonic cleaning was performed for 3 minutes using pure water that was not degassed, and the surfactant was rinsed, and then dried with warm air.

The condition of the adhered particles on an arbitrary surface of the Nd-Fe-B-based rare earth sintered magnet dried after washing was counted and analyzed by SEM / EDX in the same manner as in Example 1.
Table 2 shows the results.

It is understood from the results of Example 6 that both the total number of adhered particles and the number of Ni particles are significantly smaller than those of the other Examples 1 to 5. The ratio of the number of ferromagnetic particles to the total number of adhered particles is also 50% or less, and the method of the present embodiment in which the cleaning methods shown in Examples 1 to 5 are combined is significantly more effective than the case where each of the cleaning methods is used alone. It shows that the effect is excellent.

[0113]

According to the present invention, by rubbing the surface of the corrosion-resistant coating of the rare-earth magnet, the amount of adhered particles such as ferromagnetic particles adhered to the surface can be significantly reduced as compared with the prior art.

In the present invention, the sponge and / or the brush can be rubbed, so that the sponge or the like can be rubbed by being deformed or the like while being appropriately adapted to the irregularities of the rare earth magnet surface, so that deformation is less likely to occur. Adhered particles can be removed more effectively even when there is unevenness on the magnet surface than when rubbing with a hard object.

In the present invention, since the surface of the corrosion-resistant coating of the rare earth magnet can be rubbed with the cleaning liquid containing pure water or a surfactant, appropriate lubricity can be obtained at the time of rubbing. In addition, the removal of attached particles is promoted. In particular, when a cleaning solution containing a surfactant is used, the wettability of the surface is significantly improved, and the release of adhered particles can be promoted and re-adhesion can be prevented.

In the present invention, the surface of the rare earth magnet is adhered to the surface of the corrosion-resistant coating by ultrasonic cleaning with a cleaning solution containing pure water or a surfactant degassed to a dissolved oxygen content of 50% or less of the saturated dissolved oxygen content. Adhered particles such as ferromagnetic particles can be reduced as compared with the conventional case.

In the present invention, when the ultrasonic cleaning is performed with pure water or a cleaning liquid containing a surfactant degassed to a dissolved oxygen content of 50% or less of the saturated dissolved oxygen content, a cleaning agent containing a surfactant is further added to the rare earth magnet. Since the particles can be adhered to the surface, the adhered particles can be more effectively removed than when no surfactant is used.

In the present invention, a method of rubbing the surface of a corrosion-resistant coating of a rare-earth magnet for cleaning, and a cleaning solution containing pure water or a surfactant deaerated to a dissolved oxygen content of 50% or less of a saturated dissolved oxygen content. By performing the method in combination with the ultrasonic cleaning method, the amount of adhered particles can be further reduced as compared with the case where the cleaning is performed independently.

Since the rare earth magnet of the present invention is covered with an oxidation-resistant film such as wet electrolytic plating and / or electroless plating having better surface cleanliness than the conventional one,
If this rare earth magnet is mounted on a high-precision drive for positioning the recording / reproducing head in a magnetic, magneto-optical or optical type recording / reproducing apparatus, a recording / reproducing error can be induced. Sex can be kept very low.

[Brief description of the drawings]

FIG. 1A is a perspective view showing a state of cleaning the surface of a rare earth magnet by rubbing according to an embodiment of the present invention.
(B) is a sectional view showing the situation of (a).

FIG. 2 is a perspective view showing another method of cleaning the surface of a rare earth magnet by rubbing according to the present invention.

[Description of sign]

 DESCRIPTION OF SYMBOLS 10 Rare earth magnet 10a Front surface 10b Back surface 20 Sponge 21 Hollow part 22 Rotation support part 23 Rotation axis 30 Sliding member 31 Brush 32 Rotation support part 33 Rotation axis 40 Rotation brush 50 Rare earth magnet

Claims (12)

[Claims] 1. A method for manufacturing a rare-earth magnet having good surface cleanliness, wherein the surface of the rare-earth magnet is coated with a corrosion-resistant coating and the surface of the rare-earth magnet is rubbed and washed. 2. The method for manufacturing a rare-earth magnet having good surface cleanliness according to claim 1, wherein the surface of the rare-earth magnet is rubbed using a brush and / or a sponge. A method for producing a rare earth magnet having good surface cleanliness. 3. The method for producing a rare earth magnet having good surface cleanliness according to claim 1 or 2, wherein the surface of the rare earth magnet is wetted with pure water or a cleaning liquid containing a surfactant when rubbing. A method for producing a rare-earth magnet having a good surface cleanliness. 4. A method for ultrasonically cleaning a rare earth magnet having a surface of a rare earth magnet covered with a corrosion resistant film in pure water in which the amount of dissolved oxygen is degassed to 50% or less of the amount of saturated dissolved oxygen. A method for producing a rare earth magnet having good surface cleanliness. 5. Ultrasonic cleaning of a rare earth magnet having the surface of a rare earth magnet body coated with a corrosion resistant film in a cleaning solution containing a surfactant deaerated to a dissolved oxygen content of 50% or less of a saturated dissolved oxygen content. A method for producing a rare earth magnet having good surface cleanliness. 6. The method for producing a rare-earth magnet having good surface cleanliness according to any one of claims 1 to 3, or the method for producing a rare-earth magnet having good surface cleanliness according to claim 4 or 5. A method for producing a rare-earth magnet having good surface cleanliness, characterized in that one of them is a pre-process and the other is a post-process. 7. The method for producing a rare-earth magnet having good surface cleanliness according to claim 1, wherein the corrosion-resistant coating is electrolytic plating and / or electroless plating. Of manufacturing rare earth magnets with good surface cleanliness. 8. The method according to claim 7, wherein the rare-earth magnet is an R-T-B-based permanent magnet whose main phase is an R ₂ T ₁₄ B-type intermetallic compound. (R is one or two or more rare earth elements including Y, and T is Fe or Fe and Co). A method for producing a rare earth magnet having good surface cleanliness. 9. The total number of particles adhering to the surface of a rare earth magnet covered with a corrosion resistant film is 10 cm ²
A rare earth magnet having good surface cleanliness, wherein the magnet is 250 or less. 10. A rare-earth magnet having good surface cleanliness, wherein the number of ferromagnetic particles in the total number of particles adhering to the surface of the rare-earth magnet coated with the corrosion-resistant coating is 70% or less. . 11. The rare-earth magnet with good surface cleanliness according to claim 9, wherein the number of magnet powder particles in the total number of the attached particles is 1% or less. Rare earth magnet. 12. The rare earth magnet according to any one of claims 9 to 11, wherein the rare earth magnet body has an R ₂ T ₁₄ B type intermetallic compound as a main phase. A B-based permanent magnet (R is one or more rare earth elements including Y, T is Fe or Fe and Co), and the corrosion-resistant coating is electrolytic plating and / or electroless plating Rare earth magnet with good surface cleanliness characterized by: