PLATE SHAPED FERRITE PARTICLES HAVING METALLIC LUSTER FOR PIGMENT
20170349449 · 2017-12-07
Assignee
Inventors
Cpc classification
C09D5/36
CHEMISTRY; METALLURGY
H05K9/00
ELECTRICITY
C09D7/70
CHEMISTRY; METALLURGY
C01P2004/20
CHEMISTRY; METALLURGY
International classification
H05K9/00
ELECTRICITY
C09D5/36
CHEMISTRY; METALLURGY
Abstract
An object is to provide a plate shaped ferrite particle for a pigment, having both of electromagnetic wave shielding ability and designability, a resin molded material containing the plate shaped ferrite particle a pigment, and an electromagnetic wave shield housing for storing an electronic circuit manufactured by using the resin molded material. To achieve the object, the plate shaped ferrite particles for a pigment having a metallic luster, a resin molded material containing the plate shaped ferrite particles for a pigment, an electromagnetic wave shield housing for storing an electronic circuit manufactured by using the resin molded material are employed.
Claims
1. A plate shaped ferrite particle for a pigment characterized in having a metallic luster.
2. The plate shaped ferrite particle for a pigment according to claim 1, wherein the ferrite particle has a length in a minor axis direction of 3 to 100 μm, and a length in a major axis direction of 10 to 2000 μm.
3. A resin molded material containing the plate shaped ferrite particle for a pigment according to claim 1.
4. An electromagnetic wave shield housing for storing an electronic circuit made of the resin molded material according to claim 3.
5. A resin molded material containing the plate shaped ferrite particle for a pigment according to claim 2.
6. An electromagnetic wave shield housing for storing an electronic circuit made of the resin molded material according to claim 5.
Description
BRIEF DESCRIPTION OF DRAWINGS
[0031]
[0032]
[0033]
[0034]
PREFERRED EMBODIMENTS OF THE INVENTION
[0035] The embodiments of the present invention will be described.
[0036] <Plate Shaped Ferrite Particles According to the Present Invention>
[0037] The plate shaped ferrite particles according to the present invention are used for a pigment because the plate shaped ferrite particles has a metallic luster. The term “ferrite particles” in the present invention refer to a mass of individual ferrite particles unless otherwise noted, and the simple term “particles” refer to individual ferrite particles.
[0038] The metallic luster shows only for a ferrite particles surface having a smooth surface with light reflecting in the incident direction, the surface shines in a white color. If light does not reflect in the incident direction, a ferrite particle shows a black color inherent to the ferrite composition. The smoothness of the ferrite particles surface will be described later.
[0039] The plate shaped ferrite particles according to the present invention is preferable to have the length in the minor axis direction of 3 to 100 μm, and the length in the major axis direction of 10 to 2000 μm.
[0040] If the length in the minor axis direction is less than 3 μm, too thin ferrite particles cracks due to the poor strength. If so, a sufficient metallic luster may not be achieved. If the length exceeds 100 μm, ferrite particles project from the curved surface and no resin molded material having a smooth curved surface may be achieved when a molding having a curved surface should be manufactured by using a molded resin material containing ferrite particles. If the length in the major axis direction is less than 10 μm, incident light cannot be sufficiently reflected, and a metallic luster cannot be achieved. If the length exceeds 2000 μm, the particles may bond each other by melting in final firing and the thickness in the minor axis direction tends to increase. As a result, a plate shaped particle having a desired thickness cannot be manufactured.
[0041] <Determination of Lengths in Major Axis Direction and in Minor Axis Direction, and Aspect Ratio>
[0042] The length of the major axis direction (plate diameter) is determined as follows. Image of the particles are photographed with SEM at a magnification of 35, and the image is printed out on an A4-size paper for each visual field. The horizontal Feret diameter of a particle is examined with a ruler, and the arithmetic average of 100 particles is presumed as the average length in the major axis direction (average plate diameter).
[0043] The length of the minor axis direction (thickness) is determined after preparing the specimen for examination in the following method.
[0044] 9 g of the ferrite particles prepared and 1 g of powder resin are put in a 50-cc glass bottle, and are mixed with a ball mill for 30 minutes. The mixture is put in a dice with a diameter of 13 mm to pressure mold under a pressure of 30 MPa. The molded material in a vertically standing state is embedded in a resin and polished with a polishing machine to finish the specimen for examining the thickness, with the cross section of the molded material in a visible state. The specimen for examining the thickness is photographed with SEM at a magnification of 50, and the length in the minor axis direction (thickness) of the particle prepared is examined. The arithmetic average of 100 particles is presumed as the average length in the minor axis direction (average thickness).
[0045] The aspect ratio is calculated as (aspect ratio)=(average length in major direction)/(average length in minor axis direction) based on the average length in the major axis direction (average plate diameter) and the average length in the minor axis direction (average thickness) determined by the examining method described above.
[0046] The plate shaped ferrite particle according to the present invention is preferable to have the surface roughness (Ra) measured with a laser microscope of 0.01 to 3 μm. If the surface roughness (Ra) is in the range, the plate shaped ferrite particle achieves the metallic luster. The surface roughness (Ra) measured with a laser microscope never be less than 0.01 μm due to the slight difference in the growth rate of grains in the final firing. If the surface roughness exceeds 3 μm, the incident light is reflected or absorbed in various directions due to the large roughness of the surface and no metallic luster is achieved.
[0047] (Determination of the Surface Roughness (Ra) Measured with a Laser Microscope)
[0048] The examination is carried out in accordance with JIS B 0601-2001.
[0049] <Manufacturing Method of the Plate Shaped Ferrite Particles According to the Present Invention>
[0050] The manufacturing method of the plate shaped ferrite particles according to the present invention includes preparing of a hydrophilic ink containing a filler in advance. Examples of the filler include a metal oxide, a metal carbonate, a metal hydroxide, and the mixture thereof. The raw materials of ferrite are mixed with a Henschel mixer and the like, and the mixture is then pelletized with a roller compacter. The pellets are then calcined at a firing temperature of 1000° C. with a rotary kiln in the air atmosphere, for example.
[0051] The calcined material prepared is roughly pulverized and then finely pulverized. Then, water content is adjusted to finish a calcined material in a cake form. The calcined material in the cake form is added a dispersant and dispersed with a homogenizer to prepare the hydrophilic ink. Then, a binder is added to the hydrophilic ink.
[0052] The ink finished is coated on a film with a comma coater to make the thickness of the coated ink in the specific range. After coating, and water contained is removed, and the whole including the film is immersed in a solvent such as methyl ethyl ketone to peel the ink. Then, the solvent is removed to prepare the granulated material for plate shaped before firing (ferrite precursor).
[0053] The plate shaped granulated material prepared before firing (ferrite precursor) is subjected to binder removing followed by final firing. The fired product is then pulverized to manufacture the plate shaped ferrite particles in the specified form.
[0054] Surface roughness of the hydrophobic base material is preferable to be 5 μm or less in manufacturing of the plate shaped ferrite particles to achieve a metallic luster. If the surface roughness exceeds 5 μm, the irregularities on the surface of a coated ink tend to be large, and no metallic luster is achieved. The solid content of the ink is preferable to be 50 to 87 wt %, more preferable to be 65 to 85 wt %. If the solid content is less than 50 wt %, the hydrophilic ink is repelled by the hydrophobic base material, and no ink is coated. As a result, no plate shaped granulated material is manufactured. If the solid content exceeds 87 wt %, the ink has poor spreadability because the viscosity of the ink is too high, and it may makes coating of the ink impossible. The viscosity of the ink is preferable to be 500 to 2500 cp. If the viscosity is less than 500 cp, the hydrophilic ink is repelled by the hydrophobic base material, and no ink is coated. As a result, no plate shaped granulated material is manufactured. If the viscosity exceeds 2500 cp, the ink has poor spreadability and it may makes coating of the ink impossible.
[0055] <Resin Molded Material According to the Present Invention>
[0056] The resin molded material according to the present invention is manufactured by heat curing the resin molded material prepared by mixing the ferrite particles described above with a resin. The resin molded material contains 50 to 99.5 wt % of the plate shaped ferrite particle described above. If the content of the ferrite particle is less than 50 wt %, the properties of ferrite cannot be sufficiently achieved even the ferrite particles are contained. If the content of the ferrite particle exceeds 99.5 wt %, molding may be impossible because almost no resin is contained.
[0057] The resin used in the resin molded material is preferable to have flexibility. If the resin having flexibility is used, the curved surface is processed in the resin molded material. Examples of the resin include an epoxy resin, a phenol resin, a melamine resin, a urea resin and a fluorine-contained resin, and not specifically limited. The molded material contains a curing agent, a curing accelerator, and various additives such as silica particles according to needs.
[0058] The cross-sectional view of the resin molded material according to the present invention is shown in
[0059] <Electromagnetic Wave Shield Housing According to the Present Invention>
[0060] The cross-sectional view of an electromagnetic wave shield housing for storing an electronic circuit manufactured by using the resin molded material according to the present invention is shown in
[0061] The present invention will be more specifically described with reference to Examples as follows.
EXAMPLE 1
[0062] (Preparation of the Ink)
[0063] Iron oxide, nickel oxide, zinc oxide, and copper oxide were weighed to adjust composition Fe.sub.2O.sub.3: 49 mol, NiO: 15 mol, ZnO: 30 mol, and CuO: 6 mol were mixed with the Henschel mixer. Then, the mixture was pelletized with the roller compacter, and then calcined in a rotary kiln at a calcining temperature of 1000° C. in the air atmosphere.
[0064] The calcined material prepared was roughly pulverized with the rod mill and then finely pulverized with a wet bead mill. Then, the calcined material in the cake form with 80 wt % of solid content was prepared by adjusting the water content in the calcined material. The calcined material in the cake form was added the dispersant and dispersed with a homogenizer to prepare the hydrophilic ink. The binder (PVA) in the amount of 2 wt % relative to the water content of the hydrophilic ink was further added.
[0065] (Coating and Peeling from Coated Surface)
[0066] The hydrophilic ink prepared was coated on the commercially available PET film (thickness: 50 μm) with the comma coater to make the wet thickness 12 μm. After finishing the coating, water content was removed and the whole including the PET film was immersed in MEK to peel off the ink. The MEK was then removed to prepare the granulated material for plate shaped before firing (ferrite precursor).
[0067] (Firing)
[0068] The granulated material for plate shaped before firing (ferrite precursor) prepared was subjected to binder removing in the air at 650° C. Then final firing was carried out in the air atmosphere at 1220° C. for 4 hours. The fired material prepared has the plate shape. Then, the fired material was pulverized to manufacture the plate shaped ferrite particles having the length in the minor axis direction of 9 μm and the length in the major axis direction of 352 μm.
EXAMPLE 2
[0069] The plate shaped ferrite particles were prepared in the same manner as in Example 1, except that the solid content of the ink is 85 wt %.
EXAMPLE 3
[0070] The plate shaped ferrite particles were prepared in the same manner as in Example 1, except that the solid content of the ink is 70 wt %.
EXAMPLE 4
[0071] The plate shaped ferrite particles were prepared in the same manner as in Example 1, except that the firing temperature is 1165° C.
EXAMPLE 5
[0072] The plate shaped ferrite particles were prepared in the same manner as in Example 1, except that the wet thickness in the coating is 38 μm.
EXAMPLE 6
[0073] The plate shaped ferrite particles were prepared in the same manner as in Example 1, except that the wet thickness in the coating is 8 μm.
COMPARATIVE EXAMPLE 1
[0074] The plate shaped ferrite particles were prepared in the same manner as in Example 1, except that the firing temperature is 1050° C.
COMPARATIVE EXAMPLE 2
[0075] The plate shaped ferrite particles were prepared in the same manner as in Example 1, except that the firing temperature is 1310° C.
[0076] Table 1 shows the molar ratio of the raw materials charged, the calcination conditions (firing temperature and firing atmosphere), the fine pulverization (slurry particle diameter) and the hydrophilic ink (solid content, binder content and viscosity) in Examples 1 to 6 and Comparative Examples 1 to 2. Table 2 shows the coating conditions (coating method, film traveling speed, film surface temperature, and liquid for peeling), the binder removing conditions (treatment temperature and treatment atmosphere), and the final firing conditions (firing temperature and firing atmosphere). Table 3 shows the properties of the plate shaped ferrite particle (presence/absence of metallic luster, length in major axis direction, length in minor axis direction, aspect ratio, surface roughness measured with the laser microscope, BET specific surface area, magnetic permeability, and magnetic properties).
[0077] The BET specific surface area, the magnetic permeability, and the magnetic properties in Table 3 are determined as follows. The other examination methods are as described above.
[0078] (Determination of BET Specific Surface Area)
[0079] The BET specific surface area was examined by the specific surface area analyzer (Macsorb HM model 1208 (manufactured by Mountech Co.)). The sample in the amount of about 5 to 7 grams was placed in the standard sample cell for the exclusive use in the specific surface area analyzer and was accurately weighed with an analytical balance, and the sample (ferrite particles) was set in an examination port to start the examination. The examination was carried out by the one-point method. After finishing the examination, BET specific surface area is automatically calculated by input of the weight of the sample. As the pre-treatment before examination, the sample in the amount of about 20 grams was separately taken onto the medicine wrapping paper and then degassed to −0.1 MPa with the vacuum dryer. After confirming that the degree of vacuum reached −0.1 MPa or less, the sample was heated at 200° C. for 2 hours.
[0080] Environment: temperature; 10 to 30° C., humidity; relative humidity at 20 to 80%, without condensation.
[0081] (Determination of the Frequency Properties of the Complex Magnetic Permeability)
[0082] The frequency properties of the complex magnetic permeability were examined as follows.
[0083] The examination was carried out using the RF impedance/material analyzer E4991A manufactured by Agilent Technologies Inc., with an electrode for examining magnetic material 16454A.
[0084] The sample for examining the frequency properties of complex magnetic permeability (hereinafter simply referred to as “sample for examining complex magnetic permeability”) was prepared as follows. 9 grams of composite magnetic powder for suppressing noise and 1 gram of the binder resin (Kynar 301F: polyvinylidene fluoride) were weighed and placed in the 50-cc glass bottle for stirring and mixing for 30 minutes with the ball mill at 100 rpm.
[0085] After finishing stirring, about 0.6 grams of the mixture was weighed and injected into the dice with the inner diameter of 4.5 mm and the outer diameter of 13 mm for pressing under the pressure of 40 MPa for 1 minute with the press machine. The molded material prepared was left standing at 140° C. for 2 hours in the hot air dryer to prepare the specimen for examining the complex magnetic permeability. The outer diameter, the length in the minor axis direction, and the inner diameter of the molded specimen for examination were measured and input into the examination apparatus before examination. The complex magnetic permeability (real part magnetic permeability: μ′ and imaginary part magnetic permeability: μ″) was examined at the amplitude of 100 mV with a logarithmic sweep in the range of 1 MHz to 1 GHz. Note that the magnetic permeability μ′ in Table 3 is the value at 13.56 MHz.
[0086] (Determination of the Magnetic Properties)
[0087] The magnetic properties were examined by using the vibrating sample magnetometer (model: VSM-C7-10A (manufactured by Toei Industry Co., Ltd.)). The cell with the inner diameter of 5 mm and the height of 2 mm was filled with the sample to be examined (ferrite particle) and set in the apparatus. In the examination, sweeping was carried out up to 5K.Math.1000/4π.Math.A/m under applied magnetic field. Subsequently the applied magnetic field was reduced to draw the hysteresis curve on the recording paper. Based on the hysteresis curve, the magnetization under the applied magnetic field of 5K.Math.1000/4π.Math.A/m was determined. The residual magnetization and the coercive force were determined in the same manner.
TABLE-US-00001 TABLE 1 Fine Hydrophilic ink pulverization Binder Firing condition Slurry component Raw material charged Firing particle Solid (10 wt % PVA (mol) temperature Firing diameter content aqueous Viscosity Fe.sub.2O.sub.3 NiO ZnO CuO (° C.) atmosphere (μm) (wt %) solution) (cps) Example 1 49 15 30 6 1000 Air 0.965 80 2 1500 Example 2 49 15 30 6 1000 Air 0.965 85 2 2500 Example 3 49 15 30 6 1000 Air 0.965 70 2 1000 Example 4 49 15 30 6 1000 Air 0.965 80 2 1500 Example 5 49 15 30 6 1000 Air 0.965 80 2 1500 Example 6 49 15 30 6 1000 Air 0.965 80 2 1500 Comparative 49 15 30 6 1000 Air 0.965 80 2 1500 Example 1 Comparative 49 15 30 6 1000 Air 0.965 80 2 1500 Example 2
TABLE-US-00002 TABLE 2 Coating conditions Binder removing Film Film conditions Final firing conditions Coating traveling surface Liquid Treatment Firing Coating thickness speed temperature for temperature Firing temperature Firing method (μm) (m/min) (° C.) peeling (° C.) atmosphere (° C.) atmosphere Example 1 Comma 12 5 63 MEK 650 Air 1220 Air coater Example 2 Comma 12 5 63 MEK 650 Air 1220 Air coater Example 3 Comma 12 5 63 MEK 650 Air 1220 Air coater Example 4 Comma 12 5 63 MEK 650 Air 1165 Air coater Example 5 Comma 38 5 59 MEK 650 Air 1220 Air coater Example 6 Comma 8 5 68 MEK 650 Air 1220 Air coater Comparative Comma 8 5 68 MEK 650 Air 1050 Air Example 1 coater Comparative Comma 8 5 68 MEK 650 Air 1310 Air Example 2 coater
TABLE-US-00003 TABLE 3 Properties of plate shaped particle prepared Surface Magnetic properties at roughness BET 5K .Math. 1000/4π .Math. A/m Length in Length in measured specific (VSM) major axis minor axis with laser surface Magnetic Residual Coercive Metallic direction direction Aspect microscope area permeability Magnetization magnetization force luster (μm) (μm) ratio (Ra)(μm) (m.sup.2/g) μ′ (Am.sup.2/kg) (Am.sup.2/kg) (A/m) Example 1 Present 9 352 39.11 1.89 0.0892 28 48.13 2.43 25.09 Example 2 Present 11 463 42.09 0.98 0.0785 27 47.77 3.27 25.82 Example 3 Present 8 278 34.75 2.02 0.1039 28 47.33 3.07 26.75 Example 4 Present 10 410 41 2.78 0.1188 28 47.84 3.25 27.38 Example 5 Present 32 958 29.94 1.76 0.0689 25 47.49 2.73 27.4 Example 6 Present 6 189 31.5 1.87 0.0811 30 47.46 3.31 27.94 Comparative Absent 7 54 7.71 3.33 0.1589 19 45.4 2.4 26.86 Example 1 Comparative Absent In amorphous form 0.0543 12 48 2.56 27.46 Example 2
[0088] As shown in Table 3, the plate shaped ferrite particles having the small surface roughness with the metallic luster are prepared in Examples 1 to 6. In contrast, sufficient metallic luster is not achieved in Comparative Example 1 because the excessively low firing temperature made the grain growth insufficient, and increased the surface roughness. No plate shaped ferrite particle is prepared in Comparative Example 2 because the excessively high firing temperature make the ferrite particles bond to each other by melting. Furthermore, the magnetic permeability in Comparative Examples 1 and 2 are lower than that in Examples 1 to 6, and magnetic shielding effect in Comparative Examples 1 and 2 is poor.
EXAMPLE 7
[0089] (Preparation of the Resin Molded Material)
[0090] The mixture of 60 wt % of a binder rein (10 wt % PVA aqueous solution) and 40 wt % of the plate shaped ferrite particle prepared in Example 1 were mixed, dispersed, and coated on a PET film with the applicator (10 mil). The coated film was dried to remove water content and then peeled from the PET film to prepare the resin molded material. The resin molded material was confirmed to have the metallic luster and excellent designability.
EXAMPLE 8
[0091] (Manufacturing of the Housing Using the Resin Molded Material)
[0092] A plurality of resin molded materials prepared in Example 7 were stacked and put between beveled dies to manufacture the housing and then heated and pressed. The housing curved surface processed is confirmed to have the metallic luster and excellent designability.
INDUSTRIAL APPLICABILITY
[0093] As the plate shaped ferrite particle for a pigment according to the present invention has a metallic luster, not only electromagnetic wave shielding ability but also designability can be achieved. As a result, a resin molded material can be prepared by using the plate shaped ferrite particle for a pigment, and an electromagnetic wave shield housing for storing an electronic circuit can be manufactured by using the resin molded material. As the resin molded material formed by using the ferrite particle is not in a tile form and a resin has flexibility, the electromagnetic wave shield housing according to the present invention can be formed by curved surface processing, and also has designability. Furthermore, since the ferrite as oxide causes no surface oxidation, a stable state for a long period is assured