JP2005012162A - Sheet magnet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stable thin rare-earth magnet sheet with no degradation in its strength and magnetic characteristics, and also to provide a manufacturing method therefor. <P>SOLUTION: This magnet sheet manufacturing method includes: a mixture process of mixing a magnetic material, resin and/or rubber, and an organic solvent to produce a mixed composition; an application process of applying the mixed composition produced in the mixture process on an adherend body; and a peeling process of peeling the adherend body, which was used in the application process, away from the mixed composition. The magnet sheet manufacturing method and a magnet sheet for micro motors manufactured thereby are provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a sheet magnet, and a flexible sheet magnet that can be suitably used as a permanent magnet incorporated in a small motor mainly used in IT-related equipment, a permanent magnet for a magnet roll incorporated in a laser printer, and the like, and It relates to the manufacturing method.

  Due to the necessity of miniaturization of motors accompanying the increase in speed and miniaturization of IT-related equipment, thin sheet-like permanent magnets that can be used for small motors have been required.

  As a small motor, a cylindrical housing and a rotatable rotor arranged concentrically on the inner peripheral side of the housing are provided, and a permanent magnet is fixed to the inner peripheral surface of the housing facing the rotor. DC motors are known. In addition, for example, a brushless motor is used, which includes a stator and a rotor disposed concentrically with the stator, and a permanent magnet is fixed to the inner peripheral side of the rotor so as to face the stator. ing.

  The permanent magnet used for the motor or the like is, for example, injection molding using a mold (see, for example, Patent Document 1), compression molding method (for example, see Patent Document 2) or extrusion molding (for example, Patent Document). 3).

  FIG. 5 shows the manufacturing process of the sheet magnet manufacturing method by an extrusion method. As shown in the drawing, a sheet magnet is manufactured through a magnetic material kneading step → an extrusion step → a cutting step.

  Specifically, a rare earth magnet powder is first produced using a gas atomization method or a melt quench method. Next, in the magnetic material kneading step, a rare earth magnet powder, resin and / or rubber, and additives such as a flow aid are kneaded at a predetermined mixing ratio to prepare a kneaded composition. And in the extrusion process for making a kneaded composition into a predetermined shape, the melted kneaded composition is extruded through a mold of an extruder. Finally, the molded product is cut into a predetermined size in a cutting process to obtain a sheet magnet.

JP-A-6-260314 (paragraph number [0011]) Japanese Patent Laid-Open No. 11-265812 (paragraph number [0032] to paragraph number [0037], FIG. 2) Japanese Unexamined Patent Publication No. 2003-19738 (paragraph number [0015], FIG. 1) Japanese Patent Laid-Open No. 5-315174 (paragraph number [0027], FIG. 2)

  The above-described compression molding and injection molding are composed of a series of cycles such as filling a magnetic material into a mold, molding, and taking out a molded product in a molding process, and are basically a batch production system. Therefore, productivity is limited. Furthermore, when the thickness of the sheet magnet which is a molded product is changed, it is necessary to replace the mold corresponding to the thickness in accordance with the thickness, and the manufacturing efficiency tends to be lowered.

  On the other hand, the quality of moldability in extrusion molding depends on the fluidity of the kneaded composition melted by heating. If a lubricant or plasticizer is added to improve the fluidity, the moldability can be improved. However, the strength of the sheet magnet, which is a molded product, decreases, or the magnetic material filling rate decreases. It is difficult to stably produce a thin sheet magnet having both magnet strength and magnetic characteristics.

  Therefore, an object of the present invention is to provide a stable method for producing a thin sheet magnet without degrading the strength and magnetic properties of the thin sheet magnet.

  When the sheet magnet is incorporated into a motor housing such as a small motor, the sheet magnet is bent into a cylindrical shape by an assembly machine or the like and inserted into the housing. Therefore, in order to smoothly insert the sheet magnet into the housing, a certain degree of surface roughness is required on the surface that contacts the inner surface of the housing.

  In the above-described manufacturing methods such as injection molding and extrusion molding, it is necessary to newly provide another process for obtaining a predetermined surface roughness or to process the mold in advance. Cost. Further, it is difficult to impart surface roughness to the sheet magnet of the molded product because the magnet sheet itself is very thin and may be damaged.

  Therefore, an object of the present invention is to provide a thin sheet magnet that can be used for a small motor, and has a surface roughness on the front and back surfaces of the sheet magnet.

  The first aspect of the production method of the present invention for achieving the above object is obtained by a kneading step of kneading a magnetic material, resin and / or rubber, and an organic solvent to prepare a kneaded composition, and the kneading step. The adhering step of adhering the kneaded composition to the adherend and a peeling step of exfoliating the adherend used in the adhering step from the kneaded composition. Furthermore, in the above-described method aspect, the method further includes a peeling step of peeling the adherend from a dried kneaded composition or a solvent-kneaded kneaded composition.

  Moreover, according to the 2nd aspect of the manufacturing method of this invention, the said adhesion process is a process of apply | coating the said kneading | mixing structure to the said to-be-adhered body.

  According to the third aspect of the production method of the present invention, the kneading step has a first kneading step and a second kneading step, and the first kneading step comprises an organic solvent, a resin and / or a rubber. , And a step of preparing a kneaded composition by kneading a magnetic material, wherein the second kneading step is performed by using the organic solvent or resin and / or the kneaded composition prepared in the first kneading step. This is a step of adding and kneading a substance that changes the properties of rubber.

  According to the 4th aspect of the manufacturing method of this invention, it is a manufacturing method provided with the bridge | crosslinking process which accelerates | stimulates bridge | crosslinking of a kneaded composition after the said peeling process.

  Furthermore, according to the 5th aspect of the manufacturing method of this invention, the rolling process is built in before or after a bridge | crosslinking process, and the process for making the surface roughness of a sheet magnet into a predetermined value by roll rolling etc. is provided. Is the method.

  According to a sixth aspect of the production method of the present invention, the magnetic material is a rare earth metal.

  A first aspect of a sheet magnet for a small motor according to the present invention is a sheet magnet formed by coating and bonding a powder made of a magnetic material with a resin and / or rubber, and having an uneven surface. It is.

  Furthermore, the 2nd aspect of the sheet magnet for small motors of this invention is a sheet magnet from which the surface roughness (surface roughness) of a surface and a back surface differs.

  The third aspect of the sheet magnet for a small motor according to the present invention includes a magnetic material, has a thickness of 1.5 mm or less, and has a surface roughness of 1.0 μm to 6 μm at least on one surface facing the thickness direction. It is.

  According to the 4th aspect of the small magnet sheet magnet of this invention, a sheet magnet contains resin and / or rubber | gum further, The weight ratio of the said magnetic material and the said resin and / or rubber | gum is 15: 1. 50: 1. A more preferred weight ratio is 17: 1.

  According to the fifth aspect of the sheet magnet for a small motor of the present invention, the magnetic material of the sheet magnet is a rare earth metal.

  As described above, by kneading a lacquer solution containing a resin and an organic solvent and a magnetic material, the resin and / or rubber uniformly wraps the magnetic material, and the strength of the sheet magnet that is a molded product is secured. Sex can be imparted.

  In addition, since the organic solvent used for obtaining the fluidity of the kneaded composition has volatility, even when an organic solvent is added in the production of the sheet magnet, the organic solvent is volatilized later, The content of the magnetic material relative to the molded product can be made higher than that of a conventional sheet magnet.

  Furthermore, the surface roughness of the surface and back surface which opposes the thickness direction of a sheet magnet can be varied. Therefore, by increasing the surface roughness on the side that rubs against the small motor housing, the sheet magnet can be easily inserted into the motor housing.

The resin used in the present invention is preferably a thermosetting resin such as an epoxy resin or a polyurethane resin, or a thermoplastic resin such as a polyester resin, a polyamide resin, or a polyvinyl resin. Further, NBR or the like is desirable as the rubber used in the present invention.
Further, in the present invention, the sheet magnet for a small motor means a sheet magnet that is mounted in a motor housing, that is, a sheet magnet that is bent and formed into a cylindrical shape and has an inner diameter of 20 mm or less. It is not limited to a specific motor.

According to the present invention, it is possible to stably manufacture a thin sheet magnet that cannot be obtained by a conventional manufacturing method using extrusion molding.
In addition, since a resin and / or rubber is kneaded with a magnetic material as a lacquer solution in which an organic solvent is dissolved, the organic solvent is volatilized in a drying process after manufacturing the sheet magnet, so that a sheet in which a conventional solid lubricant remains Compared with a magnet, the content rate of the magnetic material with respect to a sheet magnet molding can be made high. Therefore, a sheet magnet having the same magnetic force can be manufactured with less magnet material than a conventional magnet.
Furthermore, the sheet magnet manufactured by conventional extrusion molding, injection molding, or the like is difficult to be molded so that the surface roughnesses of the front and back surfaces are different from each other, but the manufacturing method having the adhesion step of the present invention According to this, the degree of freedom in setting the surface roughness increases.
The sheet magnet for a small motor according to the present invention is a molded product having a thickness that cannot be obtained by conventional extrusion molding or injection molding, and has a surface having a relatively high surface roughness. Specifically, the sheet magnet for a small motor manufactured by the manufacturing method of the present invention has a thickness of about 0.15 to 1.5 mm, and the surface roughness Ra of the front and back surfaces is 1.0 μm or more. I was able to. As a result, the sheet magnet can be easily inserted into the housing of the small motor.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a sheet magnet and a manufacturing method thereof will be described in detail below with reference to the drawings.

  As shown in FIG. 1, the sheet magnet manufacturing method of the present invention is composed of a lacquer making process → first kneading process → second kneading process → attachment process → drying process → peeling process → crosslinking process → cutting process. It is what is done. Each step will be described below. In the present invention, the sheet magnet is a thin plate having a thickness of 1.5 mm or less.

  First, in a lacquer preparation process for preparing a lacquer solution, a nitrile butadiene rubber resin is dissolved in a mixed solution of methyl ethyl ketone (hereinafter referred to as MEK), which is an organic solvent, and toluene in a weight ratio of 1: 1 to prepare a lacquer solution. To do.

  The lacquer solution preferably has a viscosity that allows a strong shearing force to act on the magnetic material or the like during the kneading operation and enables the lacquer solution and the rare earth magnet powder to be dispersed and mixed. When the viscosity is insufficient, the kneaded composition cannot be uniformly dispersed and mixed, and not only the adhesion between the magnet powder and the resin and / or rubber is deteriorated, but also the resin and / or rubber is uniform throughout the magnet powder. This is because the coating cannot be performed, so that the strength of the sheet magnet may be reduced and rust may be generated on the exposed portion of the magnet.

  As the organic solvent, acetone, methyl isobutyl ketone (MIBK), cyclohexanone, or the like can be used.

  The first kneading step is a step of kneading a spherical rare earth magnet powder (magnetic material) produced by a conventionally known gas atomizing method and a lacquer solution produced in the lacquer producing step. In this step, the lacquer solution and the kneaded composition are uniformly dispersed and mixed. If it is not uniformly dispersed and mixed, not only the adhesion between the magnet powder and the resin and / or rubber is deteriorated, but also the resin cannot uniformly coat the entire magnet powder, so that the strength of the sheet magnet is reduced and the exposed part of the magnet is rusted. This is because it may occur.

  For kneading, an automatic mortar, a kneading extruder, a pressure kneader, a Banbury mixer, or the like can be used as appropriate.

  The weight ratio of the resin and / or rubber and magnet powder contained in the lacquer solution is preferably 1:15 to 1:50. When the ratio of the magnet powder is larger than 50, the sheet magnet that is a molded product cannot obtain sufficient flexibility. On the other hand, if the ratio of the magnet powder is less than 15, the sheet magnet cannot obtain a sufficient magnetic force.

  In the second kneading step, a mixed solution composed of MEK and toluene used in the lacquer preparation step, an organic peroxide that is 2,5-dimethyl-2,5-di-t-butylperoxy hexane as a crosslinking agent, MgO and ZnO as crosslinking accelerators are further kneaded in addition to the kneaded composition prepared in the first kneading step, after changing the properties of the organic solvent or resin and / or rubber.

  In the second kneading step, the viscosity of the kneaded composition produced in the first kneading step is reduced, and the viscosity is such that the kneaded composition flows and flattenes on the adherend member in the subsequent adhering step. The purpose is to grant. If it does in this way, it is suitable when applying a kneading composition in an adhesion process. The viscosity is appropriately changed depending on the application method and speed.

  Moreover, it is desirable that the above crosslinking accelerator is appropriately changed depending on the physical properties of the resin used.

  Furthermore, in the attaching step, an adherend such as a PET film whose surface is coated with a release agent is prepared and kneaded prepared in the second kneading step using a conventionally used applicator coater coating device. The composition is applied to the surface of the adherend with a predetermined thickness. Here, as the release agent, silicon resin, fluorine resin, paraffin or the like can be used. The adherend is not limited to a PET film, and film-like members such as PE, PP, and PEN, and various plate-like members can be used. In short, any member can be used as long as it can adhere the kneaded composition and can be peeled from the kneaded composition.

  In the adhesion step, application by an applicator coater was performed, but an immersion method in which the material is immersed in a solution of the kneaded composition and adhered to the adherend may be used. That is, the present invention is not limited to the above-described attachment method as long as it is a technique capable of attaching the kneaded composition to the adherend with a uniform thickness.

  Thereafter, in the drying step, the adherend to which the kneaded composition is adhered is dried, and an organic solvent such as MEK, toluene, methyl isobutyl ketone, and cyclohexanone is volatilized. By this, the magnet filling rate in the kneading composition used as a sheet magnet can be raised.

  Next, in the peeling step, the adherend is peeled from the dried kneaded composition to obtain a sheet magnet having a thin plate shape and a predetermined thickness.

  In addition, the sheet magnet is heated by a known method in the crosslinking step to promote the crosslinking of the sheet magnet.

  In the final cutting step, the crosslinked sheet magnet is cut into a predetermined size to produce a rare earth sheet magnet.

  In the above example, the cross-linking step and the cutting step are performed in this order, but the order of the cross-linking step and the cutting step may be interchanged. Specifically, the cutting step may be performed before the cross-linking step in which processing such as cutting is easier, and then the cross-linking step may be performed.

  Next, a modification of the sheet magnet manufacturing method will be described. FIG. 2 is a diagram showing a manufacturing flow of the manufacturing method.

  As shown in FIG. 2, a modified example of the sheet magnet manufacturing method is as follows: lacquer making process → first kneading process → second kneading process → attachment process → drying process → peeling process → rolling process → crosslinking process → cutting It consists of steps.

  The difference from the manufacturing method of FIG. 1 is that a rolling process for controlling the roughness of the magnet sheet is added, and the other processes are the same as those of the manufacturing method described above.

  This modification is a preferable method when it is necessary to adjust the surface roughness of the sheet magnet obtained in the attaching step. For example, the surface roughness can be adjusted by rolling the sheet magnet with a roll having a friction material or the like attached to the surface.

  In brushless motors, it is not necessary to increase the surface roughness because the sheet magnet is fixed on the rotor side. However, when the flexibility of the sheet magnet is required, the flexibility is achieved by adding a rolling process. This modification is preferable.

  Furthermore, although the rolling process is arranged before the bridging process in the above-described modification, changes such as arranging the rolling process after the bridging process can be appropriately performed.

  FIG. 3 shows a state in which the sheet magnet 1 according to the present invention is mounted inside a housing 3 of a small motor such as a DC motor. 4 is a cross-sectional view taken along line IV-IV in FIG. For the sake of clarity, the hatching showing the cross section of the housing in FIG. 4 is omitted.

  The sheet magnet 1 is manufactured by the manufacturing method described above. A sheet magnet, which is a molded product, is bent into a cylindrical shape by a known method and inserted into a cylindrical housing 3. The surface 5 of the sheet magnet 1 is a surface that contacts the inner surface of the housing, and the back surface 7 is a radially inward surface. Since the surface 5 has a higher surface roughness than the back surface 7, it can be easily inserted into the housing 3 by an assembly machine or the like.

  According to the knowledge of the present inventor, the sheet magnet used for a small motor or the like has a thickness of 1.5 mm or less in view of its structure, and the surface 5 that contacts the inner surface of the housing 3 in consideration of assembly properties It has been confirmed that the roughness Ra needs to be 1.0 μm or more. More preferably, the surface roughness Ra of 1.3 μm or more specifically shown in the examples described later is desirable, and according to this manufacturing method, a sheet magnet that satisfies this requirement can be provided.

  Since the sheet magnet 1 according to the above manufacturing method has flexibility, even if it is bent when assembled in the housing 3, the sheet does not break, such as cracks or breaks. It is a magnet.

Examples of the present invention will be described below together with comparative examples.
(Examples 1-5)
Nitrile butadiene rubber (hereinafter referred to as NBR) is dissolved in a 1: 1 mixed solution of methyl ethyl ketone (hereinafter referred to as MEK) and toluene (hereinafter referred to as a mixed solvent) to prepare a lacquer solution having a concentration of 20 wt%, Then, a magnetic material composed of spherical NdFeB powder produced by a gas atomizing method and a lacquer solution were mixed and kneaded for 30 minutes in an automatic mortar (ANM1000 type manufactured by Aichi Electric Works). Specifically, about 4.96 g of NBR, 20 g of a mixed solvent, and 100 g of a magnetic material were added and kneaded.

  Further, a mixed solvent was added so that the lacquer concentration of the kneaded composition was 12 wt%, and 2,5-dimethyl-2,5-di-t-butylperoxyhexane was added as a crosslinking agent to 0.8 wt% with respect to the resin. As a crosslinking accelerator, MgO was added at 1.5 wt% with respect to the resin, and ZnO was added at 4.0 wt% with respect to the resin. Specifically, about 0.0397 g of MgO was added. Here, the resin component in the lacquer solution is 5 g composed of NBR (about 4.96 g) and a cross-linking material (0.0397 g), and the magnetic material is 100 g. Thus, the weight ratio of NBR to magnetic material in the lacquer is about 1:20. Further, the added mixed solvent is about 16.66 g.

The magnetic coating material prepared above is coated on a silicon resin-coated PET film (Toyo Metallizing Co., Ltd., 75 μm thick) with an applicator coater (manufactured by TDK), dried, the PET film is peeled off, and the thickness is 0.15 mm. , 0.3 mm, 0.5 mm, 1.0 mm, and 1.5 mm sheet magnets were manufactured.
(Comparative Examples 1-5)
A magnetic material composed of NBR and NdFeB powder produced by a gas atomization method is made to have a weight ratio of 1:20, and 2,5-dimethyl-2,5-di-t-butylperoxyhexane is used as a crosslinking agent. 0.8 wt% relative to the resin, 1.5 wt% MgO as the crosslinking accelerator and 4.0 wt% ZnO relative to the resin, and a pressure kneader (DS-3-7.5 manufactured by Moriyama Seisakusho) A kneader for 60 minutes to obtain a kneaded composition. The input amount of the magnetic material was 2 kg.

  This kneaded composition is molded with an extrusion molding machine (lab blast mill 30C150 manufactured by Toyo Seiki Seisakusho Co., Ltd.), and sheet magnets having thicknesses of 0.3 mm, 0.5 mm, 1.0 mm, 1.5 mm, and 2.0 mm Manufactured.

各実施例及び比較例で用いるシート磁石のサンプルは、１００ｍｍｘ６００ｍｍの大きさで、粗さＲａはサンプルの１０点における測定結果の平均値である。また、表面粗さの測定には、小坂研究所製のＳＥ−３４００を使用し、測定条件は、測定長５ｍｍ、触圧０．７ｍＮ、触針Ｒ２．０μｍ、カットオフ値０．８ｍｍとした。 Table 1 below shows the results of the comparative example and the example.

The sample of the sheet magnet used in each example and comparative example has a size of 100 mm × 600 mm, and the roughness Ra is an average value of measurement results at 10 points of the sample. In addition, the surface roughness was measured using SE-3400 manufactured by Kosaka Laboratory, and the measurement conditions were a measurement length of 5 mm, a contact pressure of 0.7 mN, a stylus R of 2.0 μm, and a cutoff value of 0.8 mm. .

  In addition, the “surface” in the table is a surface on the front side when the manufactured sheet magnet adheres to the PET film, and the “back surface” is a surface that appears when the PET film is peeled off.

  As shown in Examples 1 to 5, the manufactured sheet magnets did not show defects such as breakage and chipping regardless of the thickness. On the other hand, in Comparative Examples 4 and 5, it can be removed in a good state from the extruder, but when removing Comparative Example 1 (thickness 0.3 mm) or Comparative Example 2 (thickness 0.5 mm). The product was broken and deformed in Comparative Example 3 (thickness 1.0 mm).

  Furthermore, in Examples 1-5, the surface roughness of the surface and back surface of the manufactured sheet magnet is varied. The surface roughness depends on the accuracy of the applicator coater for applying the kneaded composition, the particle size of the magnet powder, the ratio of the magnet powder and the resin, and the back surface depends on the surface roughness of the PET film. Therefore, the surface roughness of one surface of the sheet magnet can be set by changing the surface roughness of the PET film.

  On the other hand, in the comparative example, there is almost no difference in the surface roughness between the front and back surfaces of the sheet magnet.

  As can be seen from the above comparison, in the conventional manufacturing method, it is difficult to stably manufacture a thin sheet, but in the manufacturing method of the present invention, 0.15 mm, 0.3 mm, 0.5 mm, and 1.0 mm. A sheet with a thickness of 1.5 mm can be manufactured.

  In the conventional manufacturing method, the surface roughness of the sheet magnet is not different between the front surface and the back surface, but according to the manufacturing method of the present invention, the surface roughness of the front surface and the back surface can be set as appropriate.

  In particular, when a sheet magnet having a surface roughness Ra of less than 1.0 μm is inserted into the housing of a small motor, the workability is poor due to poor sliding. However, the sheet magnets of the examples are suitable for use in small motors because the surface roughness can be increased while realizing the sheet thickness that would break in the comparative example.

  In the above embodiment, rare earth-based NdFeB is used as the magnetic material, but a ferrite-based magnetic material may be used. Further, Pr, La, Ce, Sm, Pm, etc. can be used as appropriate as Nd substitution elements, Co, Ni, Mn, Cu, etc. can be used as Fe substitution elements, and B substitution elements can be used as Si, P , C, N, etc. can be used as appropriate. Further, other elements can be added as necessary.

  Further, in the above examples, NBR was used as the rubber constituting the kneaded composition, but as the resin constituting the kneaded composition, thermosetting resins such as epoxy resins and polyurethane resins, polyester resins, and polyamide resins. Thermoplastic resins such as polyvinyl resins can be used as appropriate, and the same effects as NBR can be obtained.

  In addition to MEK, acetone, methyl isobutyl ketone, cyclohexanone, etc. can be used as the organic solvent.

  Further, in addition to the cross-linking agent, for example, for the purpose of improving the wettability between the magnetic material and the resin and / or rubber, a further additive may be added depending on the physical property value required for the sheet magnet or the material used for manufacturing the sheet magnet. May be added.

  A PET film or the like is used as the adherend, but film-like members such as PE, PP, and PEN, and various plate-like members can be used.

  The present invention can be embodied in many forms without departing from its essential characteristics. Therefore, it is needless to say that the above-described embodiments are only illustrative and do not limit the present invention.

It is a figure which shows the process flow of the manufacturing method of this invention. It is a figure which shows the process flow which is a modification of the manufacturing method of this invention. It is a perspective view which shows the state which incorporated the sheet magnet manufactured by the method of this invention in the housing of a small motor. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. It is a figure which shows the process flow of the conventional manufacturing method.

Explanation of symbols

1 Sheet magnet 3 Motor housing

Claims (9)

  A kneading step of kneading a magnetic material, resin and / or rubber, and an organic solvent to prepare a kneaded composition, an attaching step of attaching the kneaded composition obtained in the kneading step to an adherend, and the attaching step And a peeling step for peeling the used adherend from the kneaded composition.   The sheet magnet manufacturing method according to claim 1, wherein the adhering step applies the kneaded composition to the adherend.   The kneading step includes a first kneading step and a second kneading step, and the first kneading step kneads an organic solvent, a resin and / or rubber, and a magnetic material to produce a kneaded composition. The second kneading step is a step of further kneading the kneaded composition prepared in the first kneading step with further adding a substance that changes the characteristics of the organic solvent or resin and / or rubber. The method for producing a sheet magnet according to claim 1, wherein the sheet magnet is provided.   The method for producing a sheet magnet according to claim 1, further comprising a crosslinking step that promotes crosslinking of the kneaded composition after the peeling step.   The method for manufacturing a sheet magnet according to claim 1, wherein the magnetic material is a rare earth metal. A sheet magnet formed by covering and bonding the powder with a resin and / or rubber, including at least a powder made of a magnetic material,
A sheet magnet for a small motor, wherein the surface magnet has a surface roughness different from that of the back surface.   A sheet magnet for a small motor, comprising a magnetic material, having a thickness of 1.5 mm or less, and having a surface roughness of at least one surface facing in the thickness direction of 1.0 μm to 6 μm.   8. The small motor seat according to claim 7, further comprising a resin and / or rubber, wherein a weight ratio of the magnetic material to the resin and / or rubber is 15: 1 to 50: 1. magnet. The sheet magnet for a small motor according to any one of claims 6 to 8, wherein the magnetic material is a rare earth metal.

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