JPS6351504B2 - - Google Patents
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- Publication number
- JPS6351504B2 JPS6351504B2 JP17481281A JP17481281A JPS6351504B2 JP S6351504 B2 JPS6351504 B2 JP S6351504B2 JP 17481281 A JP17481281 A JP 17481281A JP 17481281 A JP17481281 A JP 17481281A JP S6351504 B2 JPS6351504 B2 JP S6351504B2
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- Prior art keywords
- magnetic
- paint
- magnetization
- magnetic field
- particles
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 239000003973 paint Substances 0.000 claims description 68
- 230000005415 magnetization Effects 0.000 claims description 59
- 239000006249 magnetic particle Substances 0.000 claims description 45
- 239000006185 dispersion Substances 0.000 claims description 17
- 238000000034 method Methods 0.000 claims description 13
- 238000001514 detection method Methods 0.000 claims description 10
- 239000006247 magnetic powder Substances 0.000 description 11
- 238000010586 diagram Methods 0.000 description 7
- 238000005259 measurement Methods 0.000 description 6
- 239000002245 particle Substances 0.000 description 5
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000003993 interaction Effects 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 2
- 238000000691 measurement method Methods 0.000 description 2
- 238000004062 sedimentation Methods 0.000 description 2
- 229920000297 Rayon Polymers 0.000 description 1
- 229920002433 Vinyl chloride-vinyl acetate copolymer Polymers 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229920001577 copolymer Polymers 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 230000005381 magnetic domain Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000000049 pigment Substances 0.000 description 1
- 229920002037 poly(vinyl butyral) polymer Polymers 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
Landscapes
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analyzing Materials By The Use Of Magnetic Means (AREA)
Description
この発明は磁気テープなどに用いられる磁性塗
料における磁性粒子の分散度の測定方法およびそ
の装置に関するものである。
磁気記録用の磁性塗料における一つの課題とし
て、高保磁力の磁性粒子を高充填、高配向させる
ことがある。この高充填、高配向のためには、磁
性塗料において一つ一つの磁性粒子を破壊させる
ことなく一次粒子近くまで分散させる必要があ
り、したがつて磁気テープ等の製造にあたつて上
記塗料の分散性を適確に評価できることが要求さ
れる。
ところで、一般塗料の場合の顔料分散の評価
は、つぶゲージ、沈降分析、沈降電位法、コール
カウンタ法、光学測定法あるいは誘電率の測定等
の各種方法が適用されるが、上記磁性塗料におけ
る磁性粒子の場合は、磁性粒子間の磁気的相互作
用が強いうえ、磁性粉含有率が高く、粒子径が
1μｍ以下で分散程度が著しく高いため、上述の
各種方法では分散状態を高精度に評価することが
困難であつた。このため現状では、間接的評価、
すなわち磁気テープ製造後のテープ表面平滑度、
磁気ヒステリシスループの角型比、電磁変換特性
であるDCノイズ、Ｓ／Ｎ比等からの評価に任す
のを余儀なくされている。
この発明は、上記事情に鑑みてなされたもの
で、磁性塗料に磁場を与えると磁性粒子が回転を
始めることに着眼して、磁性粒子の磁気モーメン
トが反転しない程度の三角波正弦波もしくは矩形
波による交番微小磁場を磁性塗料に印加しなが
ら、上記塗料の磁化量の変化を検出することによ
り、磁性塗料中の磁性粒子の分散性を高精度で直
接評価できる方法およびその装置を提供すること
を目的としている。
ここで、低磁場による磁性粒子の挙動を説明す
る。第１図は針状方向が磁化容易軸で単磁区構造
をもつた１個の磁性粒子の回転モデルを示すもの
である。磁性塗料に磁場を与えると、磁性粒子が
回転を始めるが、外部磁場が存在しないときは、
磁気モーメントが磁化容易軸方向を向いている。
印加磁場Ｈがｘ軸方向にかかると、まず磁気モー
メントが瞬時的に磁化容易軸を離れて磁場方向に
回転する。つづいて、磁性粒子は磁化容易軸が磁
気モーメントの方向と同じになるように回転す
る。これにより更に磁気モーメントが印加磁場方
向に配向し、また粒子も回転する。そして、この
運動を繰り返して単一粒子であれば、最終的には
印加磁場、磁気モーメントおよび磁化容易軸がｘ
軸方向に並ぶ。多数の磁性粒子を含む磁性塗料中
における磁性粒子の回転による磁化の変化はつぎ
のようである。
ランダムに配向したｎ個の磁性粒子が反転する
（磁化容易軸の一方向に向いている磁気モーメン
トが反転する）磁場以下の磁場によつて回転する
場合、時間ｔにおける初期磁化Mt iは、印加磁場
により磁気モーメントが磁化容易軸から離れるこ
とに伴う磁化Mt inと磁性粒子の回転により磁気モ
ーメントが更に磁場方向に配向することに伴う磁
化Mt ipの和で表わされる。
Mt i＝Mt in＋Mt ip ………(1)
ここで、Mt inは印加磁場に対してほぼ瞬時的に
応答して一定値をとるので、磁気モーメントが反
転しない印加磁場では、Mim成分とMip成分とを
区別することが可能となる。したがつて、Mt iの
時間変化を測定することにより、粒子の配向成分
Mt ipを追跡することができる。
この発明の方法では、磁性塗料に対して磁性粒
子の磁気モーメントが反転しない程度の微小磁場
を交番的に印加させ、これによつて磁性塗料中で
の磁性粒子の応動にもとづく磁化量の変化を検出
して上記磁性粒子の分散性を評価するものであ
る。磁性塗料中の磁性粒子が凝集していると、上
記Mioの値はほとんど零になるが、よく分散して
いると、磁性粒子が回転できるようになり値をも
つ。すなわち、磁性粒子の分散性が良ければ、磁
性粒子は相互間の影響を受けることなく動き始め
易く、これは大きな磁化量として検出され、逆に
磁性粒子の分散性が悪ければ磁気モーメントの傾
きに対しても動きにくく、これは小さな磁化量と
して検出される。
ところで、印加磁場による磁性塗料の磁化量は
磁性粉の量に左右されることは明らかである。そ
こで所定の微小磁場を印加した際の所定時間tp後
の磁化Mt iｏをその塗料の飽和磁化Msで除した値
を分散性のパラメータとし、この値の違いから分
散性の良否を判断できることになる。
分散性＝Mto i／Ms ………(2)
つぎに、以上説明してきたことにつき、第５〜
７図を用いてさらに補足説明することにする。
まず、第５図はある磁性塗料と凝集磁性粉（磁
性粒子のみを密につめた磁性粒子群の意味）の磁
気ヒステリシス曲線であり、ここでは上記塗料と
上記磁性粉との飽和磁化量が異なるため各磁場
（の強さＨ）における磁化Miを飽和磁化Msで除し
たMi／Msを縦軸にとることによつて両者を対比
的に示しており、図中、実線が磁性塗料の磁気ヒ
ステリシス曲線、点線が凝集磁性粉の磁気ヒステ
リシス曲線である。第６図は、上記の磁気ヒステ
リシス曲線における初期磁化曲線（微小磁場での
磁化曲線）を拡大して示したもので、曲線−ａが
磁性塗料、曲線−ｂが凝集磁性粉である。
この第５、６図から明らかなように、磁性塗料
の初期磁化の立ち上がりは凝集磁性粉のそれに較
べて非常に急峻であることが判る。このような初
期磁化の立ち上がりの差異は、磁性塗料では磁気
モーメントが回転するだけでなく、磁性粒子が塗
料中で回転し、一方凝集磁性粉では磁気モーメン
トが回転するだけで磁性粒子の回転が困難である
ことに基づいている。
すなわち、このことを、微小磁場での磁化とし
て示した前記の式(1)；
Mt i＝Mt in＋Mt ip ……(1)
にあてはめて説明すれば、凝集磁性粉では磁性粒
子の回転が困難なためMt ip成分が０となり、磁気
モーメントの回転に伴う磁化Mt in成分のみが検出
され、これに対し、磁性塗料では上記のMt ip成分
とMt in成分の合計の磁化として検出されることに
なり、そのために磁性塗料では初期磁化曲線の立
ち上がりが凝集磁性粉の場合に比し急峻となるの
である。
一方、磁場の強さが一定値を超えるようになる
と、第６図の曲線−ｂ（凝集磁性粉）に示される
ように、Mt in成分のみからなる磁化を示す曲線−
b′からはずれてきて磁化曲線が徐々に立ち上がり
始める。これは、磁気モーメントが磁場方向に働
く（磁場方向に回転する）だけでなく、完全に反
転してこの反転に伴う磁化成分が加わることに起
因する。このことから、上記反転が生じるような
磁場をかければ、磁性塗料においても全く同じ反
転現象が生じ、磁性塗料の磁化には上記反転に伴
う磁化成分が加わるものであることが理解され
る。
したがつて、磁性塗料の磁化の検出において、
前記式(1)が成立して、そのMt ip成分、つまり磁性
粒子の回転に伴う磁化成分を検出することによつ
てこの塗料の磁性粒子の回転のしやすさ、すなわ
ち磁性粒子の分散性の良否を判定するためには、
磁気モーメントの反転が生じない微小磁場、つま
り第５，６図に示す例では、100エルステツド以
下とする必要があるのである。もちろん、この磁
場の大きさは用いる磁性粉末の種類などによつて
相違するから、それに応じて決めればよい。
第７図は、上記した第５、６図の如き磁気ヒス
テリシス曲線を示す磁性塗料に対して、上述のよ
うな微小磁場を印加しその際の磁化の変化を測定
する方法を、上記ヒステリシス曲線に対応させて
模式的に示したものである。なお、ここでは、微
小磁場として三角波を用いているが、この三角波
のように、微小磁場を交番的に印加させる理由
は、一定磁場の継続的印加では磁性粒子間で磁気
的相互作用が生じやすく、これをさけるためであ
る。
このように微小交番磁場を印加させると、磁性
塗料の磁化の変化が磁場の大きさの異なる経時的
な変化として求められる。そして、この変化にお
ける一定磁場での磁化が大きいほど前記のMt ip成
分が大きい、つまり磁性粒子の分散性にすぐれる
ものであると評価することができるのである。
たとえば、後記の実施例では、その角型比にて
確認しうる分散性の異なる三種の磁性塗料Ａ、
Ｂ、Ｃにつき、微小交番磁場として第３図に示さ
れるような±50エルステツドの磁場が一周期３秒
となる三角波を印加して、上述のようにして磁化
（Mi／Ms）の変化を求め、これを第４図Ａ，Ｂ，
Ｃとして表わしたものであり、また後記の表では
上記磁化の変化における印加９秒後（初期）およ
び印加60秒後（所定時間経過後）の一定磁場（−
50エルステツド）での磁化（Mi／Ms）を示した
ものである。
これらの結果は、磁性塗料の角型比と全く一致
している。すなわち、角型比の一番大きい磁性塗
料Ａの上記磁化が最も大きくなつており、逆に角
型比の一番小さい磁性塗料Ｃの上記磁化が最も小
さくなつている。なお、上述の印加９秒後という
初期の磁化と印加60秒後という一定時間経過後の
磁化（いずれも−50エルステツドとなる一定磁
場）との対比から、磁性粒子の分散安定性の良否
も評価できることになる。
すなわち、良く分散した磁性塗料中の磁性粒子
は、放置すると磁気的相互作用により時間ととも
に凝集するから、磁性塗料に対する微小交番磁場
の初期時点tpでの磁化Mto iとこの時点tpから所定時
間経過後の時点tpでの磁化Mt iＰとの比をとれば、
分散安定性を知ることができる。
分散安定性＝Mt iＰ／Mto i ………(3)
上記微小交番磁場の発生に要する信号は、正弦
波、矩形波ならびに鋸歯状波を含めた三角波など
の中から適宜選択することができる。周波数を高
くして測定時間を短縮する観点からは、特に三角
波もしくは正弦波を用いるのが好ましい。
つまり、矩形波の場合、正負の半サイクルごと
の反転が急峻であるから、それによる磁場に対し
て磁性塗料中の磁性粒子の反応が遅れて時間がか
かる。これに対し三角波や正弦波では正負の半サ
イクルごとの反転が矩形波に比し、緩慢であるか
ら、印加磁場に対しての磁性粒子の反応が早く、
したがつて適確な分散安定性を知るために要する
時間が短縮される。なお、この場合、正弦波は下
式で定義されるものであればよい。
Ｉ＝Asin（ωt＋α）0゜≦α≦180゜ ………(4)
（但し、Ａは振幅、ωtは電気角、αは位相であ
る。）
上記三角波、正弦波もしくは矩形波による微小
磁場の最大強さは前述したように磁気モーメント
が反転しない程度、一般には200エルステツド以
下であればよく、好ましくは100エルステツド以
下である。
つぎに、この発明による測定方法を実施するた
めに有用な測定装置の一例につき、第２図を用い
て説明する。
同図において、１は加振器、２は加振器１に連
結されて磁性塗料Ｗを保持する保持体、３は三角
波、正弦波もしくは矩形波を発生する信号発生
器、４は信号発生器３からの出力信号を増幅する
電流増幅器、５，５は上記信号発生器３からの出
力信号に応じて上記磁性塗料Ｗに微小磁場を印加
する磁場発生用のコイルである。６，６は検出コ
イルであり、上記磁場の印加によつて磁化された
磁性塗料Ｗの磁化量の変化を検出するものであ
る。７は検出コイル６からの検出信号を増幅する
増幅器、８は位相検波器、９は直流増幅器、１０
は記録装置である。
上記の測定装置において、信号発生器３からの
信号に応じて電流増幅器４および磁場発生用のコ
イル５を介して磁性塗料Ｗに200エルステツド以
下の微小磁場を印加する。この印加により磁性塗
料Ｗ中の磁性粒子が動き磁化量が変化することに
なる。この時磁性塗料Ｗは加振器１によつて上下
振動しているため、上記磁性粒子からの磁力線が
検知コイル６，６を横切ることになり、このため
この検知コイル６，６で上記磁化量の変化が検出
され、検出信号は増幅器７を介して位相検波器８
に入力される。位相検波器８では加振器１の振動
周波数と同期をとることによつて上記信号を直流
変換したのち、増幅器９を介して記録装置１０に
記録させる。この場合、記録装置１０によつて測
定データを印字記録するだけでなく、ブラウン管
またはパネルデータなどの表示装置に測定データ
を表示しても良い。
つぎに、上記の測定装置を用いて実際に各種の
磁性塗料の磁化量の変化を調べた結果を、以下に
示す。なお、以下の実施例で用いた磁性塗料Ａ、
Ｂ、Ｃとは下記の組成を有するものである。
＜磁性塗料Ａ＞
Co含有γ−Fe2O380重量部とエスレツクBLS
（積水化学社製のポリビニルブチラール）20重量
部とを、メチルエチルケトン／トルエンの１／１
混合溶媒150重量部に溶解分散させてなる磁性塗
料。
＜磁性塗料Ｂ＞
エスレツクBLSの代りにVYHH（UCC社製塩
化ビニル−酢酸ビニル共重合体）を用いた以外は
上記磁性塗料Ａと同様の組成である。
＜磁性塗料Ｃ＞
エスレツクBLSの代りにアクリナール（三菱
レーヨン社製のアクリル酸−メチルメタクリル酸
エステル共重合体）を用いた以外は上記磁性塗料
Ａと同様の組成である。
実施例 １
信号発生器３からの信号を三角波（第３図参
照）とし、その出力を、磁場発生用コイル５から
磁性塗料Ｗに付与される磁場の強さが50エルステ
ツドとなるように設定した。各塗料Ａ、Ｂ、Ｃに
ついて前述の方法で磁化量の変化を追跡してみた
ところ、Mi／Msは、それぞれ第４図Ａ，Ｂ，Ｃ
に示される如く、印加磁場に対して速かに応答し
て、つぎの表に示される値となつた。
なお、表中の角型比としては、各塗料をそれぞ
れ15μ厚のポリエステルベースフイルム上に4μ厚
に塗着してなる磁気テープを作製し、このテープ
の角型比を常法により測定したものである。
The present invention relates to a method and apparatus for measuring the degree of dispersion of magnetic particles in a magnetic paint used for magnetic tapes and the like. One of the challenges in magnetic coatings for magnetic recording is to highly fill and orient magnetic particles with high coercive force. In order to achieve this high filling and high orientation, it is necessary to disperse each magnetic particle in the magnetic paint close to the primary particle without destroying it. It is required to be able to accurately evaluate dispersibility. By the way, various methods such as crush gauge, sedimentation analysis, sedimentation potential method, call counter method, optical measurement method, and dielectric constant measurement are applied to evaluate pigment dispersion in general paints. In the case of particles, the magnetic interaction between magnetic particles is strong, the magnetic powder content is high, and the particle size is small.
Since the degree of dispersion is extremely high at 1 μm or less, it has been difficult to evaluate the dispersion state with high precision using the various methods described above. Therefore, at present, indirect evaluation,
In other words, the tape surface smoothness after manufacturing the magnetic tape,
We are forced to rely on evaluations based on the squareness ratio of the magnetic hysteresis loop, DC noise as electromagnetic conversion characteristics, S/N ratio, etc. This invention was made in view of the above circumstances, and focused on the fact that magnetic particles begin to rotate when a magnetic field is applied to magnetic paint. The purpose of the present invention is to provide a method and apparatus for directly evaluating the dispersibility of magnetic particles in magnetic paint with high precision by detecting changes in the amount of magnetization of the paint while applying an alternating minute magnetic field to the magnetic paint. It is said that Here, the behavior of magnetic particles due to a low magnetic field will be explained. FIG. 1 shows a rotation model of one magnetic particle having a single magnetic domain structure with the axis of easy magnetization in the acicular direction. When a magnetic field is applied to magnetic paint, the magnetic particles begin to rotate, but when there is no external magnetic field,
The magnetic moment points in the direction of the easy magnetization axis.
When an applied magnetic field H is applied in the x-axis direction, the magnetic moment instantaneously leaves the axis of easy magnetization and rotates in the direction of the magnetic field. Subsequently, the magnetic particles are rotated so that the axis of easy magnetization is in the same direction as the magnetic moment. This further orients the magnetic moment in the direction of the applied magnetic field and also rotates the particles. If a single particle repeats this motion, the applied magnetic field, magnetic moment, and easy axis of magnetization will eventually change to x
aligned in the axial direction. The change in magnetization due to the rotation of magnetic particles in a magnetic paint containing a large number of magnetic particles is as follows. If n randomly oriented magnetic particles are rotated by a magnetic field that is less than or equal to the magnetic field that reverses (the magnetic moment pointing in one direction of the easy axis of magnetization reverses), the initial magnetization M t i at time t is: It is expressed as the sum of the magnetization M t in caused by the magnetic moment moving away from the axis of easy magnetization due to the applied magnetic field, and the magnetization M t ip caused by the magnetic moment further oriented in the direction of the magnetic field due to the rotation of the magnetic particles. M t i = M t in + M t ip (1) Here, since M t in responds almost instantaneously to the applied magnetic field and takes a constant value, in an applied magnetic field where the magnetic moment does not reverse, It becomes possible to distinguish between the Mim component and the Mip component. Therefore, by measuring the change in M t i over time, we can determine the orientation component of the particles.
M t ip can be tracked. In the method of the present invention, a minute magnetic field is alternately applied to the magnetic paint to an extent that does not reverse the magnetic moment of the magnetic particles, thereby suppressing changes in the amount of magnetization due to the response of the magnetic particles in the magnetic paint. The dispersibility of the magnetic particles is evaluated by detection. If the magnetic particles in the magnetic paint are aggregated, the above Mio value will be almost zero, but if they are well dispersed, the magnetic particles will be able to rotate and will have a value. In other words, if the dispersibility of the magnetic particles is good, the magnetic particles will easily start moving without being influenced by each other, and this will be detected as a large amount of magnetization, whereas if the dispersibility of the magnetic particles is poor, the gradient of the magnetic moment will change. This is detected as a small amount of magnetization. By the way, it is clear that the amount of magnetization of the magnetic paint due to the applied magnetic field depends on the amount of magnetic powder. Therefore, the value obtained by dividing the magnetization M tio after a predetermined time t p when a predetermined minute magnetic field is applied by the saturation magnetization M s of the paint is taken as a dispersibility parameter, and the quality of the dispersibility can be determined from the difference in this value. You will be able to judge. Dispersibility = M to i / M s ………(2) Next, regarding what has been explained above,
A further supplementary explanation will be given using Figure 7. First, Figure 5 shows the magnetic hysteresis curve of a certain magnetic paint and agglomerated magnetic powder (meaning a magnetic particle group in which only magnetic particles are tightly packed), and here the saturation magnetization of the paint and the magnetic powder is different. Therefore, the two are shown in contrast by plotting M i /M s , which is obtained by dividing the magnetization M i by the saturation magnetization M s in each magnetic field (strength H), on the vertical axis. The magnetic hysteresis curve of the paint, and the dotted line is the magnetic hysteresis curve of the aggregated magnetic powder. FIG. 6 is an enlarged view of the initial magnetization curve (magnetization curve in a minute magnetic field) in the above magnetic hysteresis curve, where curve-a is the magnetic paint and curve-b is the agglomerated magnetic powder. As is clear from FIGS. 5 and 6, the rise of the initial magnetization of the magnetic paint is much steeper than that of the aggregated magnetic powder. This difference in the rise of initial magnetization is due to the fact that with magnetic paint, not only the magnetic moment rotates, but also the magnetic particles rotate in the paint, whereas with agglomerated magnetic powder, only the magnetic moment rotates, making it difficult for the magnetic particles to rotate. It is based on the fact that That is , if we apply this to the above equation (1), which is expressed as magnetization in a micromagnetic field ; Since rotation is difficult, the M t ip component becomes 0, and only the magnetization M t in component accompanying the rotation of the magnetic moment is detected. On the other hand, with magnetic paint, the sum of the above M t ip component and M t in component is detected. This is detected as magnetization, and for this reason, the rise of the initial magnetization curve in magnetic paint is steeper than in the case of agglomerated magnetic powder. On the other hand, when the strength of the magnetic field exceeds a certain value, as shown in curve-b (agglomerated magnetic powder) in Figure 6, a curve showing magnetization consisting only of the M t in component.
The magnetization curve begins to rise gradually as it deviates from b'. This is due to the fact that the magnetic moment not only acts in the direction of the magnetic field (rotates in the direction of the magnetic field), but also is completely reversed and a magnetization component accompanying this reversal is added. From this, it is understood that if a magnetic field that causes the above-mentioned reversal is applied, exactly the same reversal phenomenon will occur in the magnetic paint, and a magnetization component accompanying the above-mentioned reversal will be added to the magnetization of the magnetic paint. Therefore, in detecting the magnetization of magnetic paint,
If the above formula (1) holds true, by detecting the M t ip component, that is, the magnetization component accompanying the rotation of the magnetic particles, we can determine the ease of rotation of the magnetic particles of this paint, that is, the dispersibility of the magnetic particles. In order to judge the quality of
In the case of a minute magnetic field in which no reversal of the magnetic moment occurs, that is, in the examples shown in FIGS. 5 and 6, it is necessary to set it to 100 oersted or less. Of course, the magnitude of this magnetic field varies depending on the type of magnetic powder used, so it can be determined accordingly. Figure 7 shows a method of applying a minute magnetic field as described above to a magnetic paint exhibiting a magnetic hysteresis curve as shown in Figures 5 and 6 above and measuring the change in magnetization at that time. They are shown schematically in correspondence. Note that here, a triangular wave is used as the minute magnetic field, but the reason why the minute magnetic field is applied alternately like this triangular wave is that magnetic interactions tend to occur between magnetic particles when a constant magnetic field is continuously applied. , to avoid this. When a minute alternating magnetic field is applied in this way, changes in the magnetization of the magnetic paint can be determined as changes in the magnitude of the magnetic field over time. The larger the magnetization in a constant magnetic field during this change, the larger the above-mentioned M t ip component, that is, it can be evaluated that the dispersibility of the magnetic particles is excellent. For example, in the example described later, three types of magnetic paints A, which have different dispersibility that can be confirmed by their squareness ratio,
For B and C, a triangular wave with a magnetic field of ±50 oersted each period of 3 seconds as shown in Fig. 3 is applied as a minute alternating magnetic field, and the magnetization (M i /M s ) is changed as described above. , and calculate this as Fig. 4 A, B,
It is expressed as C, and in the table below, the constant magnetic field (-
50 oersted ) . These results are completely consistent with the squareness ratio of the magnetic paint. That is, the magnetization of the magnetic paint A having the largest squareness ratio is the largest, and conversely, the magnetization of the magnetic paint C having the smallest squareness ratio is the smallest. In addition, the quality of the dispersion stability of the magnetic particles was also evaluated by comparing the initial magnetization described above, 9 seconds after application, and the magnetization after a certain period of time, 60 seconds after application (both in a constant magnetic field of -50 oersteds). It will be possible. In other words, the well-dispersed magnetic particles in the magnetic paint will aggregate over time due to magnetic interaction if left to stand, so the magnetization M to i at the initial time point t p of a minute alternating magnetic field on the magnetic paint and the predetermined value from this time point t p If we take the ratio of the magnetization M t i P at time tp after time has elapsed, we get
You can know the dispersion stability. Dispersion stability = M t i P / M to i ...... (3) The signal required to generate the above-mentioned minute alternating magnetic field should be appropriately selected from sine waves, rectangular waves, triangular waves including sawtooth waves, etc. I can do it. From the viewpoint of increasing the frequency and shortening the measurement time, it is particularly preferable to use a triangular wave or a sine wave. In other words, in the case of a square wave, since the reversal of the positive and negative half cycles is steep, the reaction of the magnetic particles in the magnetic paint is delayed in response to the resulting magnetic field, and it takes time. On the other hand, with triangular waves and sine waves, the reversal of positive and negative half cycles is slower than with rectangular waves, so the reaction of magnetic particles to the applied magnetic field is faster.
Therefore, the time required to determine appropriate dispersion stability is shortened. In this case, the sine wave may be defined by the following formula. I=Asin(ωt+α)0゜≦α≦180゜ ………(4) (However, A is the amplitude, ωt is the electrical angle, and α is the phase.) As mentioned above, the maximum strength is such that the magnetic moment is not reversed, generally 200 oersted or less, preferably 100 oersted or less. Next, an example of a measuring device useful for carrying out the measuring method according to the present invention will be explained using FIG. 2. In the figure, 1 is a vibrator, 2 is a holder connected to the vibrator 1 and holds the magnetic paint W, 3 is a signal generator that generates a triangular wave, a sine wave, or a rectangular wave, and 4 is a signal generator. A current amplifier 5, 5 amplifies the output signal from the signal generator 3, and a coil for generating a magnetic field applies a minute magnetic field to the magnetic paint W in accordance with the output signal from the signal generator 3. Reference numerals 6 and 6 denote detection coils, which detect changes in the amount of magnetization of the magnetic paint W magnetized by the application of the magnetic field. 7 is an amplifier for amplifying the detection signal from the detection coil 6; 8 is a phase detector; 9 is a DC amplifier; 10
is a recording device. In the above measuring device, a minute magnetic field of 200 oersted or less is applied to the magnetic paint W via the current amplifier 4 and the magnetic field generating coil 5 in response to a signal from the signal generator 3. This application causes the magnetic particles in the magnetic paint W to move and the amount of magnetization to change. At this time, since the magnetic paint W is vibrated up and down by the vibrator 1, the lines of magnetic force from the magnetic particles cross the detection coils 6, 6, and therefore the detection coils 6, 6 detect the amount of magnetization. A change in is detected, and the detection signal is sent to a phase detector 8 via an amplifier 7.
is input. The phase detector 8 converts the signal into DC by synchronizing it with the vibration frequency of the vibrator 1, and then records it in the recording device 10 via the amplifier 9. In this case, the measurement data may not only be printed and recorded by the recording device 10, but also be displayed on a display device such as a cathode ray tube or panel data. Next, the results of actually investigating changes in the amount of magnetization of various magnetic paints using the above measuring device are shown below. In addition, magnetic paint A used in the following examples,
B and C have the following composition. <Magnetic paint A> 80 parts by weight of Co-containing γ-Fe 2 O 3 and Eslec BLS
(polyvinyl butyral manufactured by Sekisui Chemical Co., Ltd.) 20 parts by weight and 1/1 of methyl ethyl ketone/toluene.
A magnetic paint made by dissolving and dispersing it in 150 parts by weight of a mixed solvent. <Magnetic paint B> The composition was the same as that of magnetic paint A above, except that VYHH (vinyl chloride-vinyl acetate copolymer manufactured by UCC) was used instead of Eslec BLS. <Magnetic paint C> This has the same composition as the above-mentioned magnetic paint A, except that Acrynal (acrylic acid-methyl methacrylate ester copolymer manufactured by Mitsubishi Rayon Co., Ltd.) was used instead of Eslec BLS. Example 1 The signal from the signal generator 3 was a triangular wave (see Figure 3), and its output was set so that the strength of the magnetic field applied from the magnetic field generating coil 5 to the magnetic paint W was 50 oersteds. . When we tracked the changes in the amount of magnetization for each paint A, B, and C using the method described above, we found that Mi/Ms was as shown in Figure 4 A, B, and C, respectively.
As shown in Figure 2, it quickly responded to the applied magnetic field and reached the values shown in the table below. In addition, the squareness ratio in the table is based on a magnetic tape made by applying each paint to a thickness of 4μ on a 15μ thick polyester base film, and the squareness ratio of this tape was measured using a conventional method. It is.
【表】
上記の試験結果から明らかなように、この発明
法により磁化量の変化を測定したMi／Msによつ
て各磁性塗料Ａ，Ｂ，Ｃの磁性粒子の分散性を直
接評価できるものであることが判る。また、磁性
粒子の応答が早いため、分散安定性を見際める測
定時間も比較的短時間でよいことが明らかになつ
た。
実施例 ２
信号発生器３からの信号を正弦波とした点以外
は上記実施例１の場合と同じ条件で測定した。こ
の場合も実施例１の場合とほぼ同様に分散性を評
価できた。
実施例 ３
信号発生器３からの信号を矩形波とした点以外
は上記実施例１の場合と同じ条件で測定した。こ
の場合も分散性を直接評価することができた。た
だし、分散安定性を見際めるには通常10分以上を
要し実施例１、２の場合よりも多くの時間を費し
た。すなわち、周波数を高めようとしても、１周
期10秒以下では安定性の判定は困難であつた。こ
の結果は、分散安定性を非常に短時間に知るため
には、実施例１、２の三角波もしくは正弦波を用
いた方がより好ましいものであることを意味して
いる。
以上のように、この発明によれば、磁性塗料に
三角波、正弦波もしくは矩形波による微小交番磁
場を印加し、それによる上記磁性塗料の磁化量の
変化を検出することにより、上記磁性塗料中の磁
性粒子の分散度を直接高精度に評価できるととも
に、分散安定性も短時間のうちに判定できる効果
がある。[Table] As is clear from the above test results, the dispersibility of magnetic particles of each magnetic paint A, B, and C can be directly evaluated by Mi/Ms, which measures changes in magnetization using the method of this invention. It turns out that there is something. It has also been revealed that because the magnetic particles have a quick response, the measurement time needed to assess dispersion stability can be relatively short. Example 2 Measurement was carried out under the same conditions as in Example 1 above, except that the signal from the signal generator 3 was a sine wave. In this case as well, the dispersibility could be evaluated in substantially the same manner as in Example 1. Example 3 Measurement was carried out under the same conditions as in Example 1 above, except that the signal from the signal generator 3 was a rectangular wave. In this case as well, the dispersibility could be directly evaluated. However, it usually took 10 minutes or more to assess the dispersion stability, which was longer than in Examples 1 and 2. That is, even if an attempt was made to increase the frequency, it was difficult to judge the stability if one cycle was less than 10 seconds. This result means that it is more preferable to use the triangular wave or sine wave of Examples 1 and 2 in order to know the dispersion stability in a very short time. As described above, according to the present invention, a minute alternating magnetic field with a triangular wave, a sine wave, or a rectangular wave is applied to the magnetic paint, and a change in the amount of magnetization of the magnetic paint due to this is detected. This method has the advantage that the degree of dispersion of magnetic particles can be directly evaluated with high precision, and the dispersion stability can also be determined in a short time.
第１図は磁性粒子の回転を示す模式図、第２図
はこの発明に係る分散度の測定装置の一例を示す
ブロツク図、第３図は印加磁場の波形図、第４図
Ａ〜Ｃは異なる磁性塗料の各分散度特性図、第５
図はこの発明に係る分散度の測定方法を説明する
ための磁気ヒステリシス曲線を示す模式図、第６
図は上記磁気ヒステリシス曲線における初期磁化
曲線を示す模式図、第７図は微小交番磁場の印加
と磁性塗料の磁化の変化との関係を上記第５図の
磁気ヒステリシス曲線と対応させて示す模式図で
ある。
１……振動手段、２……保持手段、５……微小
磁場発生手段、６……検出手段、１０……記録手
段、Ｗ……磁性塗料。
Fig. 1 is a schematic diagram showing the rotation of magnetic particles, Fig. 2 is a block diagram showing an example of the dispersity measuring device according to the present invention, Fig. 3 is a waveform diagram of the applied magnetic field, and Fig. 4 A to C are Dispersion characteristic diagrams of different magnetic paints, 5th
The figure is a schematic diagram showing a magnetic hysteresis curve for explaining the dispersion measurement method according to the present invention.
The figure is a schematic diagram showing the initial magnetization curve in the above magnetic hysteresis curve, and Figure 7 is a schematic diagram showing the relationship between the application of a minute alternating magnetic field and the change in magnetization of the magnetic paint in correspondence with the magnetic hysteresis curve in Figure 5 above. It is. DESCRIPTION OF SYMBOLS 1... Vibration means, 2... Holding means, 5... Minute magnetic field generation means, 6... Detection means, 10... Recording means, W... Magnetic paint.
Claims (1)
転しない程度の三角波、正弦波もしくは矩形波に
よる微小交番磁場を上記塗料に印加しながら、上
記塗料の磁化量の変化を検出し、この磁化量の変
化を飽和磁化量で除した値を上記磁性粒子の分散
性のパラメータとしたことを特徴とする磁性塗料
における磁性粒子の分散度の測定方法。 ２ 磁性塗料を保持する保持手段と、三角波、正
弦波もしくは矩形波による微小交番磁場を上記磁
性塗料に印加させる微小磁場発生手段と、微小磁
場中において上記磁性塗料を振動させる手段と、
上記磁性塗料の磁化量の変化を検出する検出手段
と、上記検出出力を表示する手段とを具備したこ
とを特徴とする磁性塗料における磁性粒子の分散
度の測定装置。[Claims] 1. Detecting changes in the amount of magnetization of the paint while applying a minute alternating magnetic field of triangular, sine, or rectangular waves to the paint to the extent that the magnetic moment of the magnetic particles in the magnetic paint does not reverse. A method for measuring the degree of dispersion of magnetic particles in a magnetic paint, characterized in that a value obtained by dividing the change in the amount of magnetization by the amount of saturation magnetization is used as a parameter for the dispersibility of the magnetic particles. 2. A holding means for holding the magnetic paint, a minute magnetic field generating means for applying a minute alternating magnetic field with a triangular wave, a sine wave, or a rectangular wave to the magnetic paint, and a means for vibrating the magnetic paint in the minute magnetic field;
An apparatus for measuring the degree of dispersion of magnetic particles in a magnetic paint, comprising: a detection means for detecting a change in the amount of magnetization of the magnetic paint; and a means for displaying the detection output.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17481281A JPS5876758A (en) | 1981-10-30 | 1981-10-30 | Method and apparatus for measuring dispersion level of magnetic particles in magnetic paint |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP17481281A JPS5876758A (en) | 1981-10-30 | 1981-10-30 | Method and apparatus for measuring dispersion level of magnetic particles in magnetic paint |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5876758A JPS5876758A (en) | 1983-05-09 |
| JPS6351504B2 true JPS6351504B2 (en) | 1988-10-14 |
Family
ID=15985092
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP17481281A Granted JPS5876758A (en) | 1981-10-30 | 1981-10-30 | Method and apparatus for measuring dispersion level of magnetic particles in magnetic paint |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5876758A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006112976A (en) * | 2004-10-15 | 2006-04-27 | Asahi Kasei Corp | Test material analyzing apparatus and its quantifying method |
| JP2006525506A (en) * | 2003-04-15 | 2006-11-09 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | Method for determining state variables and changes in state variables |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0103655B1 (en) * | 1982-09-22 | 1987-02-11 | Ibm Deutschland Gmbh | Device to determine the properties of magnetic particle dispersions |
-
1981
- 1981-10-30 JP JP17481281A patent/JPS5876758A/en active Granted
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2006525506A (en) * | 2003-04-15 | 2006-11-09 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | Method for determining state variables and changes in state variables |
| JP4768603B2 (en) * | 2003-04-15 | 2011-09-07 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | Method for determining state variables and changes in state variables |
| JP2006112976A (en) * | 2004-10-15 | 2006-04-27 | Asahi Kasei Corp | Test material analyzing apparatus and its quantifying method |
| JP4669259B2 (en) * | 2004-10-15 | 2011-04-13 | 旭化成株式会社 | Test substance analyzer and quantitative method |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5876758A (en) | 1983-05-09 |
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