JPS6161228A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a medium having low light transmittivity and excellent transfer characteristic by using iron oxide magnetic powder to constitute the magnetic powder to be incorporated into a magnetic layer made into double-layered structure, incorporating Fe<2+> at a lower ratio into the magnetic powder used for the layer on the surface side and incorporating the Fe<2+> at a higher ratio into the magnetic powder used for the layer on the inside of the substrate side. CONSTITUTION:The magnetic powder incorporated into the 1st layer adjacent to the non- magnetic substrate and the 2nd layer adjacent to said layer of a magnetic recording medium provided with the magnetic layer made of the double layer structure consisting of said layers on said substrate consists of the iron oxide magnetic powder having >=30m<2>/g specific surface area by a nitrogen adsorption method. The ratio of the Fe<2+> of the magnetic powder to be used for the 1st layer is required to be >=3.5wt%. The light transmittivity of the magnetic layer increases and the detection of a tape end by the effect of light is made difficult if the ratio is below said value. The tendency toward the difficulty in erasing of the magnetic record is admitted if the ratio is too high and therefore the ratio is usually preferably limited up to 10wt%. The magnetic powder to be used for the 2nd layer is required to have <3.5wt%, more preferably <=3.0wt% content of the Fe<2+>. The transfer characteristic is not satisfactory if the ratio exceeds said value.

Description

【発明の詳細な説明】 〔産業上の利用分野〕 この発明は磁気テープその他の磁気記録媒体に関するも
のである。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to magnetic tapes and other magnetic recording media.

〔従来の技術〕[Conventional technology]

近年、ビデオテープは高密度記録、高ＳＮ比化が進めら
れ、それに伴い用いる磁性粉も微粒子化が図られ、窒素
吸着法による比表面積が３０ｄ／ｇ以上の粒子径の小さ
いものが用いられている。In recent years, high-density recording and high signal-to-noise ratios have been promoted in video tapes, and with this, the magnetic powder used has also been made finer, with small particle diameters having a specific surface area of 30 d/g or more by nitrogen adsorption method being used. There is.

一方磁性粉の種類としては適切な保磁力で記録再生する
ため、また取り扱いの便宜その他の点からｒ−ＦｅｚＯ
ｔおよびＣＯ含有ｒ−Ｆｅ２ｏ３などのような酸化鉄系
磁性粉が一般的に使用されている。On the other hand, as a type of magnetic powder, r-FezO
Iron oxide-based magnetic powders such as t- and CO-containing r-Fe2o3 are commonly used.

しかるに、これら酸化鉄系磁性粉は茶色〜茶かつ色を呈
しており、このような磁性粉が微粒子化されると磁性層
の光透過率が太き（なり、ＶＨ３方式ビデオテープレコ
ーダなどのように光でテープの末端を検出する方式では
誤動作が発生しやすくなる。However, these iron oxide-based magnetic powders exhibit a brown to brown color, and when such magnetic powders are made into fine particles, the light transmittance of the magnetic layer increases (as in VH3 video tape recorders, etc.). A method that uses light to detect the end of the tape is prone to malfunctions.

この欠点を解決するために、従来は、カーボンブラック
などの光じゃへい性の大きい顔料を増量するという対策
をとっていたが、上記顔料の分散性が悪かったり磁性層
中に占める割合が多くなるため、磁性層の表面平滑性お
よび電磁変換特性の低下を招いていた。また、磁性層の
厚みを増し光透過率を小さくすることも考えられるが、
ｆ＋４１気テープはそれぞれの用途によってテープ厚み
の規格が定まっており、磁性層の厚みを増した分だけポ
リエステルフィルムのような支持体の厚みを減らさなけ
ればならず、テープの機械的強度が低下しトラブルにつ
ながる。In order to solve this drawback, conventional measures have been taken to increase the amount of pigments with high photoresistance such as carbon black, but these pigments have poor dispersibility or occupy a large proportion in the magnetic layer. Therefore, the surface smoothness and electromagnetic conversion characteristics of the magnetic layer deteriorate. It is also possible to increase the thickness of the magnetic layer and reduce the light transmittance.
For F+41 tape, tape thickness standards are determined depending on each application, and as the thickness of the magnetic layer increases, the thickness of the support such as polyester film must be reduced, which reduces the mechanical strength of the tape. It will lead to trouble.

そこで、この発明者は、酸化鉄系磁性粉の色に着目し、
この磁性粉に含まれるＦｅ　Ｚ　’の含有量が少ない程
明るい茶色を呈し、逆にＦｅ２＋の含有量が多い程茶か
っ色〜黒色を呈する傾向があることより、後者のＦ　ｅ
　！４含有量の多いたとえばＦｅ　Ｚ　＋の含有量がＦ
ｅＯ換算で７．０重量％以上となるような酸化鉄系磁性
粉を用いて磁気テープを作製したところ、前述の如き顔
料の増量などの対策をとることな（磁性層の光透過率を
低下できることを見出した。Therefore, this inventor focused on the color of iron oxide magnetic powder,
The lower the content of Fe Z ' contained in this magnetic powder, the brighter brown it appears, and conversely, the higher the content of Fe2+, the more brownish to black it tends to be.
! 4.For example, the content of Fe Z + is F
When a magnetic tape was manufactured using iron oxide magnetic powder containing 7.0% by weight or more in terms of eO, it was found that without taking measures such as increasing the amount of pigment as described above (decreasing the light transmittance of the magnetic layer). I found out what I can do.

しかるに、引き続く検討により、上記の如きＦｅ２゛の
含を量の多い磁性粉を用いると、磁性層の光透過率を低
下できる反面、磁気テープめ転写特性が悪（なり（磁気
記録の転写が起こりやすくなり）、これが原因で磁気テ
ープとして実用化しにくい問題があることが判明した。However, subsequent studies revealed that using magnetic powder with a high content of Fe2 as described above can lower the light transmittance of the magnetic layer, but on the other hand, the transfer characteristics of the magnetic tape become poor (transfer of magnetic recording occurs). It was discovered that this was a problem that made it difficult to put it into practical use as a magnetic tape.

そこで、この問題を解決するために、上記の如きＦｅ”
含有量の多い磁性粉とともにＦｅ　ｌ　４含有量の少な
いたとえばＦｅＯ換算で２．０重量％以下の磁性粉を混
合することを試みたが、Ｆｅｚ′″含有量の少ない磁性
粉を多く配合すると光透過率を満足できず、逆にＦｅ１
ｈ含有量の多い磁性粉を多く配合すると転写特性が悪（
なり、両配合割合を種々検討してみても両特性を共に満
足させることはできなかった。Therefore, in order to solve this problem, the above-mentioned Fe”
An attempt was made to mix a magnetic powder with a low FeI4 content, for example, 2.0% by weight or less in terms of FeO, with a magnetic powder with a high content, but when a large amount of magnetic powder with a low Fez''' content was mixed, the optical Unable to satisfy the transmittance, on the contrary Fe1
If a large amount of magnetic powder with a high h content is blended, the transfer characteristics will be poor (
Therefore, even though various mixing ratios of both were investigated, it was not possible to satisfy both characteristics.

〔発明が解決しようとする問題点〕[Problem that the invention seeks to solve]

この発明は、以上の観点から、微粒子状の酸化鉄系磁性
粉のＦｅ”含有量を多くして光透過率を低くする場合の
転写特性の低下という問題点を解決して、光透過率と転
写特性とをともに満足する磁気記録媒体を得ることを目
的とする。From the above points of view, the present invention solves the problem of deterioration of transfer characteristics when the light transmittance is lowered by increasing the Fe content of fine particulate iron oxide magnetic powder, and improves the light transmittance. The object of the present invention is to obtain a magnetic recording medium that satisfies both transfer characteristics.

〔問題点を解決するための手段〕[Means for solving problems]

この発明者は、上記目的を達成するために鋭意検討した
結果、まずＦｅ２°含有量の設定により光透過率と転写
特性との両立を図るには磁性層が単層構成では既述のと
おりどうしても無理があるものと考え、この考えのちと
に磁性層を二層構成として転写特性に影響を与える表面
側の層にＦｅ”含有量の少ない磁性粉を用い、支持体に
隣接する内側の層にＦｅ　！　＋含有量の多い磁性粉を
用いてみたところ、従来の単層構成では不可能であった
光透過率が低くてかつ転写特性にすぐれる磁気記録媒体
が得られるものであることを知り、この発明を完成した
。As a result of intensive studies to achieve the above object, the inventor found that in order to achieve both light transmittance and transfer characteristics by setting the Fe2° content, it is impossible to achieve both light transmittance and transfer characteristics if the magnetic layer has a single layer structure, as described above. Considering this idea to be unreasonable, we created a two-layer magnetic layer, using magnetic powder with a low Fe content in the surface layer that affects transfer characteristics, and in the inner layer adjacent to the support. When we tried using magnetic powder with a high Fe!+ content, we found that it was possible to obtain a magnetic recording medium with low light transmittance and excellent transfer characteristics, which was impossible with conventional single-layer structures. , completed this invention.

すなわち、この発明は、非磁性支持体上にこの支持体に
隣接する第一の層とこの層に隣接する第二の層とからな
る二層構造の磁性層を設けてなる磁気記録媒体において
、上記両層に含まれるＧｆｆ性粉は窒素吸着法による比
表面積がいずれも３０ｍ／ｇ以上の酸化鉄系磁性粉から
なり、かつ第一の層の上記磁性粉中に占めるＦｅ２＋の
割合はＦｅＯ換算で３．５重量％以上、第二の層の上記
磁性粉中に占めるＦｅ２＋の割合はＦｅＯ換算で３．５
重世％未満であることを特徴とする磁気記録媒体に係る
ものである。That is, the present invention provides a magnetic recording medium in which a magnetic layer having a two-layer structure consisting of a first layer adjacent to the support and a second layer adjacent to this layer is provided on a non-magnetic support, The Gff powder contained in both of the above layers is composed of iron oxide magnetic powder with a specific surface area of 30 m/g or more determined by the nitrogen adsorption method, and the proportion of Fe2+ in the magnetic powder of the first layer is equivalent to FeO. The proportion of Fe2+ in the magnetic powder of the second layer is 3.5% by weight or more in terms of FeO.
The present invention relates to a magnetic recording medium characterized in that the magnetic recording medium is less than 1%.

〔発明の構成・作用〕[Structure and operation of the invention]

この発明において第一および第二の磁性層に用いる磁性
粉は、いずれも窒素吸着法による比表面積（以下、ＢＥ
Ｔ法比表面積という）が３０Ｍ／ｇ以上、好ましくは３
０〜６０ｍ／ｇの酸化鉄系磁性粉であり、これには酸化
鉄磁性粉のばか酸化鉄磁性粉にＧｏなどの他種金属を種
々の方法で含ませた他種金属含有酸化鉄磁性粉が含まれ
る。上記の如き微粉を用いることにより高密度記録や高
’　　ＳＮ比化に容易に対応させることができる。In this invention, the magnetic powder used for the first and second magnetic layers has a specific surface area (hereinafter referred to as BE) determined by the nitrogen adsorption method.
T-method specific surface area) is 30 M/g or more, preferably 3
0 to 60 m/g of iron oxide magnetic powder, which includes iron oxide magnetic powder containing other metals such as Go in various ways. is included. By using the above-mentioned fine powder, high-density recording and high signal-to-noise ratios can be easily achieved.

第一の層に用いる上記磁性粉のＦｅ２＋の割合はＦｅＯ
換算（以下、単にＦｅ”含有量という）で３．５重量％
以上であることが必要であり、上記値より少なくなると
磁性層の光透過率が高くなり光によるテープ端末の検出
が難しくなる。なお、上記割合があまりに多くなりすぎ
ると消去特性つまり磁気記録の消去が難しくなる傾向が
みられるため、通常は上記Ｆｅ”含有量が１０重量％ま
でとするのがよい。The proportion of Fe2+ in the magnetic powder used for the first layer is FeO
3.5% by weight (hereinafter simply referred to as "Fe" content)
If it is less than the above value, the light transmittance of the magnetic layer becomes high and it becomes difficult to detect the end of the tape by light. Note that if the above ratio becomes too large, the erasing characteristics, that is, the erasing of magnetic recording tends to become difficult, so it is usually preferable that the above Fe'' content is up to 10% by weight.

また、第二の層に用いる上記磁性粉は、上記同様のＦｅ
２−含有量が３．５重量％未満、好ましくは３．０重量
％以下であることが必要である。上記値以上となると転
写特性を満足できなくなる。なお、上記割合があまりに
少なくなりすぎると第一の層の磁性粉におけるＦｅ　２
＋含有量が前記範囲内での少な目である場合やこの第二
の層が肉薄である場合などにｔｎ性層の光透過率が多少
高くなる傾向がみられるから、通常は０．１重量％以上
となるようにするのが好ましい。Further, the magnetic powder used for the second layer is Fe similar to the above.
2-It is necessary for the content to be less than 3.5% by weight, preferably less than 3.0% by weight. When the value exceeds the above value, the transfer characteristics cannot be satisfied. In addition, if the above ratio becomes too small, Fe 2 in the magnetic powder of the first layer
+ The light transmittance of the tn layer tends to be somewhat high when the content is a little within the above range or when this second layer is thin, so it is usually 0.1% by weight. It is preferable to set it to the above value.

酸化鉄系磁性粉のＦｅ”＋含有量を上記の如く設定する
には、たとえばｒ−Ｆｅｚｅ３扮を適宜の手段で所望程
度還元処理するかあるいはＦｅ５０＜粉を適宜の手段で
所望程度酸化処理するなど従来公知の手法にて簡単に行
うことができ、また市販品として各種Ｆｅ２°含有量と
されたものを容易に入手することができる。To set the Fe''+ content of the iron oxide magnetic powder as described above, for example, r-Feze3 is reduced to a desired degree by an appropriate means, or Fe50< powder is oxidized to a desired degree by an appropriate means. This can be easily carried out using conventionally known methods such as, and commercially available products with various Fe2° contents can be easily obtained.

この発明の磁気記録媒体を得るには、たとえば第一およ
び第二の層に用いる上記特定の磁性粉をそれぞれ適宜の
結合剤に混合分散させた各要用の磁性塗料を調製し、ま
ず第一の要用の磁性塗料をポリエステルフィルムなどの
非磁性支持体上に任意の塗布手段で塗布乾燥して第一の
層を設は常法によりカレンダー処理を行ったのち、この
第一の層上に第二の要用の磁性塗料を上記同様にして塗
布乾燥しカレンダー処理を行って第二の層を設けるよう
にすればよい。In order to obtain the magnetic recording medium of the present invention, for example, each required magnetic paint is prepared by mixing and dispersing the above-mentioned specific magnetic powders used in the first and second layers in an appropriate binder, and then A first layer is formed by applying and drying the required magnetic paint onto a non-magnetic support such as a polyester film using any coating method. The second necessary magnetic paint may be applied and dried in the same manner as described above, followed by calendering to form the second layer.

上記第一および第二の層からなる磁性層の厚みとしては
、３〜８μｍ位が好ましく、さらに第一の層／第二の層
の厚み比が一般に１／４〜６／１、好ましくは２／３〜
４／１とするのがよい。特に第一の層／第二の層の厚み
比を上記の如く設定することにより、光透過率および転
写特性にともに好結果を得ることができる。The thickness of the magnetic layer consisting of the first and second layers is preferably about 3 to 8 μm, and the thickness ratio of the first layer/second layer is generally 1/4 to 6/1, preferably 2 /3～
It is better to set it as 4/1. In particular, by setting the thickness ratio of the first layer/second layer as described above, good results can be obtained in both light transmittance and transfer characteristics.

上記に用いる結合剤としては、塩化ビニル系樹脂、繊維
素系樹脂、ポリウレタジ系樹脂、ポリエステル系樹脂、
イソシアネート化合物などの従来公知の結合剤をいずれ
も使用可能である。各磁性塗料には、カーボンブラック
、α−Ｆｅ！０３、Ａ１）０３　、Ｃｒｚ　Ｏｓ等従来
公知の塗膜補強用充填剤や、脂肪酸、脂肪酸エステル、
シリコーン系潤滑剤、フッ素系潤滑剤の如き潤滑剤など
の各種添加剤を任意に添加することができる。また、磁
性塗料は有機溶剤タイプであっても水分散タイプであっ
てもよい。The binder used above includes vinyl chloride resin, cellulose resin, polyurethane resin, polyester resin,
Any conventionally known binder such as isocyanate compounds can be used. Each magnetic paint contains carbon black, α-Fe! 03, A1) 03, Crz Os, etc., conventionally known paint film reinforcing fillers, fatty acids, fatty acid esters,
Various additives such as lubricants such as silicone-based lubricants and fluorine-based lubricants can be optionally added. Further, the magnetic paint may be an organic solvent type or a water dispersion type.

〔発明の効果〕〔Effect of the invention〕

以上のように、この発明においては、磁性粉として微粒
子状の酸化鉄系磁性粉を用いるにあたって、磁性層を二
層構成として、かつ表面側の層に用いる上記磁性粉のＦ
ｅ”含有量を少なく逆に支持体側の内側の層に用いる上
記磁性粉のＦｅｉ＋含有量を多くする構成としているか
ら、これにより光透過率が低く、しかも転写特性にすぐ
れる磁気記録媒体を得ることができる。As described above, in this invention, when using fine particulate iron oxide magnetic powder as the magnetic powder, the magnetic layer has a two-layer structure, and the F of the magnetic powder used for the surface layer is
Since the magnetic powder is configured to have a low e'' content and a high Fei+ content of the magnetic powder used in the inner layer on the support side, a magnetic recording medium with low light transmittance and excellent transfer characteristics can be obtained. be able to.

〔実施例〕〔Example〕

以下に、この発明の実施例を比較例と対比して記載する
。なお、以下において部とあるのは重量部を意味するも
のとする。Examples of the present invention will be described below in comparison with comparative examples. In addition, in the following, parts shall mean parts by weight.

実施例Ｉ ＣＯ含有ｒ−Ｆｅ、Ｏ，粉 ｒｓＥＴ？ｎ比７″４貴４０％／ｇ、　　　１ｏｏ、。Example I CO-containing r-Fe, O, powder rsET? n ratio 7″4 noble 40%/g, 1oo.

Ｆｅ”９．０重量％） カーボンブラック （平均粒子径２４　ｍ　ｕ　）　　　　　　　４．５　
＠Ｂ粒状α−ＦｅｚＯ：＋粉 （平均粒子径１．ｏμｍ）　　　　　　　５．２＠Ｉｓ
ステアリン酸亜鉛　　　　　　　　　０．５　＠ｎシク
ロへキサノン　　　　　　　　　９ｏ＠じトルエン　　
　　　　　　　　　　　９０合Ｂ上記の配合成分を高速
攪拌機で５〜ｌｏｌ寺間予備混合し、その後サンドミル
で分散を完了させた組成物に、下記の配合成分を適宜の
順序でカロえ高速攪拌機で混合して第一の要用の磁性塗
料を８間装した。Carbon black (average particle size 24 mu) 4.5
@B granular α-FezO: + powder (average particle size 1.0 μm) 5.2 @Is
Zinc stearate 0.5 @ncyclohexanone 9o@ditoluene
90 Go B The above ingredients are pre-mixed with a high-speed stirrer for 5~lol Terama, and then the following ingredients are mixed in an appropriate order with a high-speed stirrer into the composition that has been completely dispersed with a sand mill. Eight coats of magnetic paint were applied.

ミリスチン酸　　　　　　　　　　　　　２＠ｂシクロ
へキサノン　　　　　　　　　　４０＠ｂトルエン　　
　　　　　　　　　　　４１）Ｓつぎに、上記のｔ茎１
性塗料を孔隙１μｍのフィルターを通過させたのち、厚
み１３μｍの表面平滑性の良いポリエステルフィルム上
に塗布乾燥しその後カレンダ処理を行って厚みが２．０
μｍの第一の磁性層を形成した。Myristic acid 2@b cyclohexanone 40@b Toluene
41) S Next, the above t stem 1
The paint was passed through a filter with a pore size of 1 μm, then applied onto a 13 μm thick polyester film with good surface smoothness, dried, and then calendered to a thickness of 2.0 μm.
A first magnetic layer with a thickness of .mu.m was formed.

一方、下記の配合成分を高速攪拌機で５〜ＩＯ時間予備
混合し、その後サンドミルでよく分散させた。On the other hand, the following ingredients were premixed using a high-speed stirrer for 5 to 10 hours, and then well dispersed using a sand mill.

Ｃｒｚ０３粉（平均粒子径１．０．ｔ＋ｍ）０．８部Ａ
　ｌ　ｚ　Ｏｙ粉（平均粒子径０．４μｍ）２．０部ス
テアリン酸亜鉛　　　　　　　　　０．５部シクロヘキ
サノン　　　　　　　　　９０部トルエン　　　　　　
　　　　　　　９０部得られた組成物に、下記の配合成
分を適宜の順序で加え高速攪拌機で混合して第二の履用
の磁性塗料を調製した。Crz03 powder (average particle size 1.0.t+m) 0.8 part A
l z Oy powder (average particle size 0.4 μm) 2.0 parts Zinc stearate 0.5 parts Cyclohexanone 90 parts Toluene
To 90 parts of the resulting composition, the following ingredients were added in an appropriate order and mixed using a high-speed stirrer to prepare a second magnetic paint for wear.

ミリスチン酸　　　　　　　　　　　　２部ステアリン
酸ｎ−ブチル　　　　　　　１部シクロへキサノン　　
　　　　　　　４０部トルエン　　　　　　　　　　　
　　４０部この磁性塗料を孔隙１μｍのフィルターを通
過させたのち、前記の第一の層上に塗布乾燥しその後カ
レンダー処理を行って厚みが３．０μｍの第二の磁性層
を形成した。しかるの元、１／２インチ幅にスリットを
行いこの発明の磁気テープを作製した。Myristic acid 2 parts n-butyl stearate 1 part cyclohexanone
40 parts toluene
40 parts of this magnetic paint was passed through a filter with a pore size of 1 .mu.m, then coated on the first layer and dried, followed by calendering to form a second magnetic layer having a thickness of 3.0 .mu.m. Under these conditions, slits were made to a width of 1/2 inch to produce a magnetic tape of the present invention.

実施例２ 第一の層に用いたＣｏ含含有−Ｆｅｔｕｓ粉のＦｅ　２
＋含有量を９．０重量％から７．０重量％に変更し、か
つ第二の層に用いたＣＯ含含有−Ｆｅ、０３粉のＦ　ｅ
　ｔａ含有量を１．０重量％から２．０重量％に変更し
た以外は、実施例１と同様にして磁気テープを作製した
。Example 2 Fe 2 of Co-containing Fetus powder used in the first layer
+The content was changed from 9.0% by weight to 7.0% by weight, and the CO-containing -Fe, Fe of 03 powder used in the second layer
A magnetic tape was produced in the same manner as in Example 1 except that the ta content was changed from 1.0% by weight to 2.0% by weight.

実施例３ 第一の層に用いたＣＯ含有ｒ−Ｆｅ、Ｏ，扮のＦｅ”″
含有量を９．０重量％から５．０重量％に変更し、かつ
第二の層に用いたＣＯ含含有−ＦｅｚＯ３粉のＦｅ”含
有量を１．０重量％から３．０重量％に変更した以外は
、実施例１と同様にしても■ステープを作製した。Example 3 CO-containing r-Fe used in the first layer, O, and Fe""
The content was changed from 9.0% by weight to 5.0% by weight, and the Fe'' content of the CO-containing -FezO3 powder used for the second layer was changed from 1.0% by weight to 3.0% by weight. (2) A staple was produced in the same manner as in Example 1 except for the following changes.

実施例４ 第一の層に用いたＣＯ含含有−ＦｅｚＯ３粉のＦｅｔ゛
含を量を９．０重量％から３．５重量％に、その厚みを
２．０μｍから３．０μｍに変更し、かつ第二の層に用
いたＣＯ含存γ−ＦｅｚＯ：＋粉のＦ’ｅ２゛含を量を
１．０重量％から３．０重量％に、その厚みを３．０μ
ｍから２．０μｍに変更した以外は、実施例１と同様に
して［５ｉ気テープを作製票゛こ。Example 4 The Fet content of the CO-containing -FezO3 powder used for the first layer was changed from 9.0% by weight to 3.5% by weight, and the thickness was changed from 2.0 μm to 3.0 μm, In addition, the F'e2 content of the CO-containing γ-FezO:+ powder used for the second layer was increased from 1.0% by weight to 3.0% by weight, and its thickness was increased to 3.0μ.
A 5i tape was prepared in the same manner as in Example 1, except that the thickness was changed from m to 2.0 μm.

実施例５ 第一の層に用いたＣｏ含有ｒ−ＦｅｚＯｓ粉のＢＥＴ法
比表面積を３０ｒｒｆ／ｇに、Ｆｅｔ゛含有量を９．０
重量％から３．５重量％に変更し、かつ第二の層に用い
たＣｏ含存ｒ−ＦｅｚＯ３粉のＢＥＴ法比表面積を３０
ｍ２／ｇに、Ｆｅ”含有量を１．０重量％から３．０重
量％に変更した以外は、実施例１と同様にして磁気テー
プを作製した。Example 5 The BET method specific surface area of the Co-containing r-FezOs powder used for the first layer was set to 30rrf/g, and the Fet content was set to 9.0.
The BET method specific surface area of the Co-containing r-FezO3 powder used for the second layer was changed from 3.5% by weight to 30% by weight.
A magnetic tape was produced in the same manner as in Example 1, except that the Fe'' content was changed from 1.0% by weight to 3.0% by weight.

比較例１ 第一の層に用いたＧｏ含有ｒ−Ｆｅ、Ｏ，、粉のＦｅ”
含有量を９．０重量％から１．０重量％に変更し、かつ
第二の層に用いたＣｏ含含有−ＦｅｚＯ３粉のＦｅ”含
有量を１．０重量％から３．０重量％に変更した以外は
、実施例１と同様にして比較用の磁気テープを作製した
。Comparative Example 1 Go-containing r-Fe, O, powdered Fe” used in the first layer
The content was changed from 9.0% by weight to 1.0% by weight, and the Fe'' content of the Co-containing -FezO3 powder used for the second layer was changed from 1.0% by weight to 3.0% by weight. A magnetic tape for comparison was produced in the same manner as in Example 1 except for the changes.

比較例２ 第一の層に用いたＣｏ含［ｒ　　Ｆｅｚｅｓ粉のＦｅ”
含有量を９．０重量％から３．５重量％に変更し、かつ
第二の層に用いたＧｏ含有ｒ−ＦｅｔＯｙ粉のＦｅ”含
有量を１．０重量％から７．０重量％に変更した以外は
、実施例１と同様にして比較用の磁気テープを作製した
。Comparative Example 2 Co-containing [r Fezes powder used in the first layer]
The content was changed from 9.0% by weight to 3.5% by weight, and the Fe'' content of the Go-containing r-FetOy powder used for the second layer was changed from 1.0% by weight to 7.0% by weight. A magnetic tape for comparison was produced in the same manner as in Example 1 except for the changes.

比較例３ 第一の層に用いたＣＯ含有７−ｐ’ｅ、０３粉のＢＥＴ
法比表面積を３０ｍ／ｇに、Ｆｅ”含有量を９．０重量
％から３．５重量％に変更するとともに、その厚みを２
．０μｍから３．０μｍに変更し、かつ第二の層に用い
たＣＯ含有ｒ−ＦｅｚＯ３粉のＢＥＴ法比表面積を３０
ｒ＋（７ｇに、Ｆｅ”含有量を１．０重量％から７．０
重量％に変更するとともに、その厚みを３．０．１７　
ｍから２．０μｍに変更した以外は、実施例１と同様に
して比較用の磁気テープを作製した。Comparative Example 3 BET of CO-containing 7-p'e, 03 powder used in the first layer
The specific surface area was changed to 30 m/g, the Fe content was changed from 9.0% by weight to 3.5% by weight, and the thickness was changed to 2.
．． The BET method specific surface area of the CO-containing r-FezO3 powder used for the second layer was changed from 0 μm to 3.0 μm, and the BET method specific surface area was changed from 0 μm to 3.0 μm.
r+ (7g, Fe” content from 1.0% by weight to 7.0%
Change the weight% and the thickness to 3.0.17
A magnetic tape for comparison was produced in the same manner as in Example 1 except that the thickness was changed from m to 2.0 μm.

比較例４ 第一の層を設けないで、ＣＯ含有Ｔ　　ＦｅｚＯ３粉の
Ｆｅ　ｌ＋含有量を１．０重量％から０．３重量％に変
更した以外は実施例１の第二の履用の磁性塗料と同様の
配合組成からなる磁性塗料を調製し、これを実施剤１と
同様のポリエステルフィルム上に同様の操作で直接塗布
乾燥しカレンダ処理を行って厚みが５．０μｍの磁性層
を形成し、比較用の磁気テープを作製した。Comparative Example 4 Magnetic properties of the second wear of Example 1 except that the first layer was not provided and the Fe l+ content of the CO-containing T FezO3 powder was changed from 1.0% by weight to 0.3% by weight. A magnetic paint having the same composition as the paint was prepared, and this was applied directly onto the same polyester film as in Example 1 using the same procedure, dried, and calendered to form a magnetic layer with a thickness of 5.0 μm. A magnetic tape was prepared for comparison.

比較例５ 第一の層を設けないで、Ｃｏ含含有−ＦｅｚＯ３粉のＦ
ｅ”含有量を１．０重量％から９．０重量％に変更した
以外は実施例１の第二の履用の磁性傅料と同様の配合組
成からなる磁性塗料を調製し、これを実施剤１と同様の
ポリエステルフィルム上に同様の操作で直接塗布乾燥し
カレンダ処理を行って厚みが５．０μｍの磁性層を形成
し、比較用の磁気テープを作製した。Comparative Example 5 F of Co-containing -FezO3 powder without providing the first layer
A magnetic paint having the same composition as the second magnetic material for wear in Example 1 was prepared, except that the e'' content was changed from 1.0% by weight to 9.0% by weight, and this was carried out. A comparative magnetic tape was prepared by directly coating the same polyester film as Agent 1, drying it, and calendering to form a magnetic layer having a thickness of 5.0 μm.

上記の実施例１〜５および比較例１〜５の各磁気テープ
につき、光透過率および転写特性を下記の方法で測定評
価した。結果は、後記の表に示されるとおりであった。The light transmittance and transfer characteristics of each of the magnetic tapes of Examples 1 to 5 and Comparative Examples 1 to 5 described above were measured and evaluated using the following methods. The results were as shown in the table below.

なお、測定条件はＶＨ３方式ビデオカセットシステム規
格に準じた。The measurement conditions were in accordance with the VH3 video cassette system standard.

く光透過率〉 ９．０００オングストロームの光源とフォトセンサの間
に磁気テープをおき、磁気テープを透過した光をフォト
センサで測定した。Light transmittance> A magnetic tape was placed between a 9.000 angstrom light source and a photosensor, and the light transmitted through the magnetic tape was measured with the photosensor.

く転写特性〉 ＶＨ３方式ＶＴＲを用い規定バイアス電流で規定レベル
より１０ｄＢ高いＩＫＩ（ｚの信号を記録した一枚の磁
気テープと記録してない磁気テープを１０枚交互に重ね
巻き、３０℃、６５％ＲＨの環境下で２４時間保存した
磁気テープを再生し、記録した部分の再生出力と、転写
部の再生出力の差を測定した。Transfer characteristics> Using a VH3 system VTR, the IKI was 10 dB higher than the specified level with a specified bias current (1 magnetic tape with a z signal recorded and 10 magnetic tapes without recording were wound alternately, 30°C, 65°C). A magnetic tape stored for 24 hours in an environment of %RH was played back, and the difference between the playback output of the recorded portion and the playback output of the transfer section was measured.

上記の結果より明らかなように、ＢＥＴ法比表面積３０
ｉ／ｇ以上の酸化鉄系磁性粉を用いる場合、第一の層に
用いる上記磁性粉のＦｅ”含有量を３．５重量％以上、
第二の層に用いる上記磁性粉のＦｅ　ｇ　＊含有量を３
．５重量％未満とした磁気テープ（実施例１〜５）では
、光透過率が低（転写特性も良好である。これに対し、
いずれかの層のＦｅ　ｇ’−含有量がこの発明の範囲外
となる磁気テープ（比較例１〜３）および磁性層が単層
の磁気テープ（比較例４．５）では、光透過率が高いか
あるいは転写特性が悪くなっている。As is clear from the above results, the BET method specific surface area is 30
When using iron oxide magnetic powder of i/g or more, the Fe'' content of the magnetic powder used for the first layer is 3.5% by weight or more,
Fe g *content of the above magnetic powder used for the second layer is 3
．． In the magnetic tapes containing less than 5% by weight (Examples 1 to 5), the light transmittance was low (the transfer characteristics were also good.
In the magnetic tapes in which the Fe g'-content of any layer is outside the range of the present invention (Comparative Examples 1 to 3) and in the magnetic tape with a single magnetic layer (Comparative Example 4.5), the light transmittance is It is either high or the transfer characteristics are poor.

Claims (1)

【特許請求の範囲】[Claims] （１）非磁性支持体上にこの支持体に隣接する第一の層
とこの層に隣接する第二の層とからなる二層構造の磁性
層を設けてなる磁気記録媒体において、上記両層に含ま
れる磁性粉は窒素吸着法による比表面積がいずれも３０
ｍ＾２／ｇ以上の酸化鉄系磁性粉からなり、かつ第一の
層の上記磁性粉中に占めるＦｅ＾２＾＋の割合はＦｅＯ
換算で３．５重量％以上、第二の層の上記磁性粉中に占
めるＦｅ＾２＾＋の割合はＦｅＯ換算で３．５重量％未
満であることを特徴とする磁気記録媒体。(1) A magnetic recording medium comprising a two-layered magnetic layer comprising a first layer adjacent to this support and a second layer adjacent to this layer on a non-magnetic support, in which both of the above layers are provided. The magnetic powder contained in the powder has a specific surface area of 30% by nitrogen adsorption method.
m^2/g or more of iron oxide magnetic powder, and the proportion of Fe^2^+ in the magnetic powder of the first layer is FeO
A magnetic recording medium characterized in that the proportion of Fe^2^+ in the magnetic powder of the second layer is 3.5% by weight or more in terms of FeO, and less than 3.5% by weight in terms of FeO.