JPH0332139B2

JPH0332139B2 -

Info

Publication number: JPH0332139B2
Application number: JP60269512A
Authority: JP
Inventors: Kuniharu Fujiki; Ikuo Matsumoto
Original assignee: Victor Company of Japan Ltd
Current assignee: Victor Company of Japan Ltd
Priority date: 1985-12-02
Filing date: 1985-12-02
Publication date: 1991-05-10
Also published as: JPS62129939A

Description

[Detailed description of the invention]

〔産業上の利用分野〕本発明は、例えばビデオ用テープ、オーデイオ
用テープ等の磁気テープ、又はフロツピーデイス
ク、ハードデイスク等の磁気デイスクといつた磁
気記録媒体の製造法に関するものである。〔従来技術とその問題点〕従来より、磁気記録媒体の耐摩耗性及び耐衝撃
性向上の為に、磁気記録媒体の磁性層表面に各種
の保護膜、例えば熱可塑性又は熱硬化性の樹脂
よりなる保護膜、磁性塗膜中に放射線重合性の
滑剤を含ませておき、放射線照射により硬化させ
てなる保護膜を構成することが提案されている。これらのうち、例えば特開昭47−24804号公報
等に示されている上記の技術にあつては、磁性
塗膜層構成の為に用いたバインダが熱可塑性のも
のであるか又は熱硬化型のものであるかによつて
４通りの場合があるものの、保護膜が熱可塑性樹
脂よりなる場合には耐摩耗性が充分でない欠点が
あり、又、特に磁性塗膜層構成の為に用いたバイ
ンダが熱硬化性のものであつて、かつ保護膜が熱
可塑性のものである場合には、磁性塗料を塗布し
て構成した磁性塗膜層を硬化させた後に保護膜の
塗料を塗布といつた工程を経なければならないの
で、すなわち保護膜の塗料を塗布した後に硬化作
業を行なうとブロツキングが起きるので、それだ
け製造が面倒である欠点があり、又、保護膜が熱
硬化型樹脂よりなる場合には、保護膜の塗料を塗
布後熱硬化反応を行なわなければならないのでブ
ロツキングが生じてしまう欠点がある。又、特開昭57−24028号公報等に示されている
上記の技術にあつては、塗膜強度の向上は充分
なものとは言えず、又、磁性層への転写を防ぐこ
とが出来ず、Ｃ／Ｎが低下するといつた欠点があ
る。〔発明の開示〕本発明者は、前記の問題点に対する研究を行な
つた結果、非磁性支持体上に磁性粉及びバインダ
を含む磁性塗料を塗布した後、この上に紫外線硬
化型樹脂又は電子線硬化型樹脂を含む塗料を塗布
し、その後表面平滑化処理を行なつた後紫外線照
射又は電子線照射して硬化処理することによつて
磁気記録媒体を製造すると、この場合にはブロツ
キングが起きないものとなり、又、表面平滑化処
理の前に磁性層上に紫外線硬化型樹脂又は電子線
硬化型樹脂を含む塗料を塗布するので、磁性層表
面の空隙あるいは凹部にこの塗料が入り込み、こ
の結果磁性層への紫外線硬化型樹脂又は電子線硬
化型樹脂の稠密性が高くなり、磁気記録媒体の耐
摩耗性及び耐衝撃性が向上し、又、再生出力の低
下は極めて小さく、又、磁性層と反対側面の転写
の問題が起きにくい磁気記録媒体が得られること
を見い出したのである。尚、非磁性支持体としては、例えばポリエステ
ルフイルム、ポリイミドフイルム、ポリフエニレ
ンスルフイドフイルム等があり、又、磁性粉とし
ては、例えばγ−Fe₂O₃、Co含有γ−Fe₂O₃、
Fe₃O₄、Co含有γ−Fe₃O₄、CrO₂、Fe、Fe−Co
−Ni、バリウムフエライト等があり、又、バイ
ンダとしては、例えばポリエステル樹脂、ポリウ
レタン樹脂、エポキシ樹脂、塩化ビニル−酢酸ビ
ニル−ビニルアルコール共重合体、硝化綿、ニト
リルゴム等がある。又、紫外線又は電子線照射型樹脂としては、例
えばポリウレタンアクリレート、エポキシアクリ
レート、ポリエステルアクリレート、シリコーン
樹脂アクリレート、又はジメチルアミノメタクリ
レート等がある。尚、非磁性支持体上に塗布される磁性塗料中に
は、上記磁性粉及びバインダの他に、通常分散
剤、潤滑剤、研磨剤、帯電防止剤等の添加剤が必
要に応じて所定量添加されており、又、磁性塗膜
上に塗布される紫外線硬化型樹脂又は電子線硬化
型樹脂を含む塗料中には、必要に応じて単官能ア
クリレートモノマ、二官能アクリレートモノマ、
多官能アクリレートモノマ等の反応性希釈剤、及
びベンジルジメチルケタール、ベンゾフエノン等
の重合開始剤が所定量添加されている。又、非磁性支持体上に磁性塗料を塗布すること
によつて設けられる磁性塗膜層の厚みは従来から
の磁気記録媒体のものと同様に約１〜5μｍ厚あ
れば良く、又、この磁性塗膜層上に塗布すること
によつて設けられる紫外線硬化型樹脂又は電子線
硬化型樹脂の層は約0.5μｍ以下の厚みであること
が、より一層好ましくは約0.05〜0.2μｍの厚みで
あることが望ましい。尚、磁性塗膜層構成の為に用いたバインダが熱
硬化性樹脂である場合には、紫外線照射又は電子
線照射の前に熱処理によつて熱硬化反応を行う
と、非磁性支持体上の磁性層と非磁性支持体の裏
面側とが、ロール状に巻回した場合に互いに接触
し、その状態で熱硬化炉に入れると、熱により磁
性層が軟化して接触する非磁性支持体の裏面側の
表面が転写またはブロツキングを起こすことがあ
り、従つて紫外線照射又は電子線照射の後に熱硬
化反応を行う方が望ましい。実施例１ Co含有γ−Fe₂O₃100重量部、塩化ビニル−酢
酸ビニル−ビニルアルコール共重合体（米国U.
C.C.社のVAGH）10重量部、ポリウレタンエラ
ストマー（日本ポリウレタン工業(株)製のN2304）
10重量部、レシチン１重量部、カーボンブラツク
５重量部、アルミナ粉末５重量部、ステアリン酸
イソアミル１重量部、トルエンとメチルエチルケ
トンとメチルイソブチルケトンの等量混合溶剤
300重量部を、サンドミル約20時間混合分散し、
これに硬化剤としてポリイソシアネート（日本ポ
リウレタン工業(株)製のコロネートＬ）を５重量部
加え、このようにして得られた磁性塗料を約75μ
ｍ厚のポリエステルフイルムからなる非磁性支持
体上に約2.5μｍ厚塗布し、乾燥する。次に、このようにして構成された磁性塗膜層上
に、下記の構造式で表わされるポリエステルアクリレート70重量
部、トリメチロールプロパントリアクリレート20
重量部、ヒドロキシエチルアクリレート５重量
部、ベンゾフエノン３重量部、ジメチルアミノエ
タノール２重量部からなる塗料を約0.2μｍ厚塗布
し、そしてその後スチールロール又はプラスチツ
クロール等のカレンダーによつて表面平滑化処理
を行なう。この表面平滑化処理の後、紫外線照射装置を用
いて紫外線照射処理を行なつて表面硬化反応を行
なわしめ、続いて50℃で48時間の熱硬化反応を行
なわしめる。そして、最終的に約130mmの径に打ち抜いて磁
気デイスク等の磁気記録媒体を作製する。実施例２ γ−Fe₂O₃100重量部、ポリエステル樹脂（東
洋紡績製のバイロン＃200）27重量部、ポリウレ
タンエラストマー（日本ポリウレタン工業(株)製の
N2304）３重量部、レシチン１重量部、カーボン
ブラツク５重量部、アルミナ粉末10重量部、オレ
イン酸４重量部、トルエンとメチルエチルケトン
の混合溶剤300重量部を、サンドミルで約20時間
混合分散し、この磁性塗料を実施例１と同様な非
磁性支持体上に同様に塗布して乾燥する。次に、このようにして構成された磁性塗膜層上
に、実施例１と同様な紫外線硬化型の樹脂を含む
塗料を同様に塗布し、その後同様な表面平滑化処
理を行なう。この表面平滑化処理の後、紫外線照射装置を用
いて紫外線照射処理を行ない表面硬化反応を行な
わしめる。そして、最終的に実施例１と同様にして磁気記
録媒体を作製する。実施例３実施例１において作製した磁性塗膜層上に、ジ
メチルアミノメタクリレート10重量部、ポリウレ
タンアクリレート（分子量約5000）５重量部、ト
リメチロールプロパントリアクリレート７重量
部、トリラウリルホスフエート５重量部、トルエ
ン100重量部からなる塗料を約0.2μｍ厚塗布し、
そして実施例１と同様な表面平滑化処理を行な
う。この表面平滑化処理の後、電子線照射装置を用
いて10Mradの電子線照射処理を行なつて表面硬
化反応を行なわしめ、続いて実施例１と同様な熱
処理を行なつて熱硬化反応を行なわしめる。そして、最終的に実施例１と同様にして磁気記
録媒体を作製する。比較例１実施例１において、紫外線硬化型の樹脂を用い
ないで同様に行ない、磁気記録媒体を作製する。比較例２実施例２において、紫外線硬化型の樹脂を用い
ないで同様に行ない、磁気記録媒体を作製する。比較例３実施例１において、紫外線硬化型の樹脂を含む
塗料を磁性塗膜層上に塗布する前に、磁性膜層の
表面平滑化処理を行ない、その後熱硬化反応を行
なわしめた後、紫外線硬化型の樹脂を含む塗料を
塗布し、そして同様な紫外線照射処理を行なつて
表面硬化反応を行なわしめ、そし最終的に実施例
１と同様にして磁気記録媒体を作製する。比較例４実施例２において、紫外線硬化型の樹脂を含む
塗料を磁性塗膜層上に塗布する前に、磁性塗膜層
の表面平滑化処理を行ない、その後紫外線硬化型
の樹脂を含む塗料を塗布し、そして同様な紫外線
照射処理を行なつて表面硬化反応を行なわしめ、
そし最終的に実施例２と同様にして磁気記録媒体
を作製する。比較例５実施例１において、紫外線硬化型の樹脂を含む
塗料の代りに、ポリビニルホルマール90重量部、
メラミン樹脂10重量部、イソプロピルアルコール
200重量部よりなる熱硬化型の樹脂の塗料を用い
て磁性塗膜層上に同様に塗布し、そして表面平滑
化処理及び50℃で48時間の熱硬化処理を行ない、
最終的に実施例１と同様にして磁気記録媒体を作
製する。比較例６ Co含有γ−Fe₂O₃100重量部、塩化ビニル−酢
酸ビニル−ビニルアルコール共重合体（米国U.
C.C.社製のVAGH）10重量部、ポリウレタンエ
ラストマー（日本ポリウレタン工業(株)製の
N2304）10重量部、レシチン１重量部、カーボン
ブラツク５重量部、アルミナ粉末５重量部、CH₂
＝CHCOOC₁₃H₂₇1重量部、及び溶剤300重量部を
サンドミルで約20時間混合分散し、そしてこれに
硬化剤としてポリイソシアネート（日本ポリウレ
タン工業(株)製のコロネートＬ）を５重量部加え、
この磁性塗料を実施例３と同様な非磁性支持体上
に同様に塗布し、乾燥後表面平滑化処理を同様に
行ない、そして実施例３と同様な電子線処理を行
ない、その後最終的に実施例３と同様にして磁気
記録媒体を作製する。〔特性〕上記各例で得た磁気記録媒体について、そのパ
ス回数（耐久性）、表面研磨によるスクラツチの
発生の有無、及び2F信号の出力を調べると、表
に示す通りである。 [Industrial Field of Application] The present invention relates to a method for manufacturing magnetic recording media such as magnetic tapes such as video tapes and audio tapes, or magnetic disks such as floppy disks and hard disks. [Prior art and its problems] Conventionally, in order to improve the abrasion resistance and impact resistance of magnetic recording media, various protective films, such as thermoplastic or thermosetting resin, have been applied to the surface of the magnetic layer of magnetic recording media. It has been proposed to construct a protective film by impregnating a radiation-polymerizable lubricant in a magnetic coating film and curing it by irradiation with radiation. Among these, in the above-mentioned technology disclosed in, for example, JP-A No. 47-24804, the binder used for forming the magnetic coating layer is thermoplastic or thermosetting. There are four types depending on the type of protective film, but when the protective film is made of thermoplastic resin, it has the disadvantage of not having sufficient wear resistance. When the binder is thermosetting and the protective film is thermoplastic, the protective film is applied after the magnetic paint is applied and the magnetic coating layer is cured. In other words, if the protective film is cured after the coating is applied, blocking will occur, so manufacturing is complicated.Also, if the protective film is made of thermosetting resin, This method has the disadvantage that blocking occurs because a heat curing reaction must be carried out after the coating for the protective film is applied. Furthermore, with the above-mentioned technology disclosed in Japanese Patent Application Laid-open No. 57-24028, etc., the strength of the coating film cannot be improved sufficiently, and transfer to the magnetic layer cannot be prevented. First, there is a drawback that the C/N ratio decreases. [Disclosure of the Invention] As a result of conducting research on the above-mentioned problems, the present inventor coated a magnetic paint containing magnetic powder and a binder on a non-magnetic support, and then coated it with an ultraviolet curable resin or an electronic coating. If a magnetic recording medium is manufactured by applying a paint containing a line-curable resin, then smoothing the surface, and then curing it by irradiating it with ultraviolet rays or electron beams, blocking may occur in this case. Furthermore, since a paint containing an ultraviolet curable resin or an electron beam curable resin is applied to the magnetic layer before the surface smoothing treatment, this paint gets into the voids or recesses on the surface of the magnetic layer, resulting in The density of the ultraviolet curable resin or electron beam curable resin in the magnetic layer is increased, the abrasion resistance and impact resistance of the magnetic recording medium are improved, and the reduction in reproduction output is extremely small. They discovered that it is possible to obtain a magnetic recording medium that is less prone to the problem of transfer on the opposite side. Examples of non-magnetic supports include polyester films, polyimide films, polyphenylene sulfide films, etc., and examples of magnetic powders include γ-Fe ₂ O ₃ , Co-containing γ-Fe ₂ O ₃ ,
Fe ₃ O ₄ , Co-containing γ-Fe ₃ O ₄ , CrO ₂ , Fe, Fe-Co
Examples of the binder include polyester resin, polyurethane resin, epoxy resin, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, nitrified cotton, and nitrile rubber. Examples of the ultraviolet ray or electron beam irradiation type resin include polyurethane acrylate, epoxy acrylate, polyester acrylate, silicone resin acrylate, and dimethylamino methacrylate. In addition to the above-mentioned magnetic powder and binder, additives such as dispersants, lubricants, abrasives, antistatic agents, etc. are usually added in predetermined amounts as necessary to the magnetic paint coated on the non-magnetic support. Additionally, monofunctional acrylate monomers, difunctional acrylate monomers,
Reactive diluents such as polyfunctional acrylate monomers and polymerization initiators such as benzyl dimethyl ketal and benzophenone are added in predetermined amounts. In addition, the thickness of the magnetic coating layer provided by coating a magnetic coating material on a non-magnetic support should be about 1 to 5 μm, similar to that of conventional magnetic recording media; The layer of ultraviolet curable resin or electron beam curable resin provided by coating on the coating layer has a thickness of about 0.5 μm or less, more preferably about 0.05 to 0.2 μm. This is desirable. If the binder used to form the magnetic coating layer is a thermosetting resin, if a thermosetting reaction is performed by heat treatment before UV irradiation or electron beam irradiation, the When the magnetic layer and the back side of the non-magnetic support are wound into a roll, they come into contact with each other, and when they are placed in a thermosetting oven in that state, the magnetic layer softens due to the heat and the back side of the non-magnetic support that comes in contact with it. Transfer or blocking may occur on the back surface, so it is preferable to carry out a thermosetting reaction after UV irradiation or electron beam irradiation. Example 1 100 parts by weight of Co-containing γ-Fe ₂ O ₃ , vinyl chloride-vinyl acetate-vinyl alcohol copolymer (U.S.
CC VAGH) 10 parts by weight, polyurethane elastomer (N2304 manufactured by Nippon Polyurethane Kogyo Co., Ltd.)
10 parts by weight, 1 part by weight of lecithin, 5 parts by weight of carbon black, 5 parts by weight of alumina powder, 1 part by weight of isoamyl stearate, a mixed solvent of equal amounts of toluene, methyl ethyl ketone, and methyl isobutyl ketone.
Mix and disperse 300 parts by weight in a sand mill for about 20 hours,
To this, 5 parts by weight of polyisocyanate (Coronate L manufactured by Nippon Polyurethane Industries Co., Ltd.) was added as a hardening agent, and the magnetic paint thus obtained was coated with approximately 75μ
It is coated to a thickness of about 2.5 μm on a non-magnetic support made of a polyester film of m thickness and dried. Next, on the magnetic coating layer constructed in this way, the following structural formula is applied. 70 parts by weight of polyester acrylate, 20 parts by weight of trimethylolpropane triacrylate
A coating consisting of 1 part by weight, 5 parts by weight of hydroxyethyl acrylate, 3 parts by weight of benzophenone, and 2 parts by weight of dimethylaminoethanol was applied to a thickness of about 0.2 μm, and then the surface was smoothed using a calender such as a steel roll or a plastic roll. Let's do it. After this surface smoothing treatment, ultraviolet irradiation treatment is performed using an ultraviolet irradiation device to perform a surface hardening reaction, followed by a heat curing reaction at 50° C. for 48 hours. Finally, it is punched out to a diameter of about 130 mm to produce a magnetic recording medium such as a magnetic disk. Example 2 100 parts by weight of γ-Fe ₂ O ₃ , 27 parts by weight of polyester resin (Vylon #200 manufactured by Toyobo Co., Ltd.), polyurethane elastomer (manufactured by Nippon Polyurethane Industry Co., Ltd.)
3 parts by weight of N2304), 1 part by weight of lecithin, 5 parts by weight of carbon black, 10 parts by weight of alumina powder, 4 parts by weight of oleic acid, and 300 parts by weight of a mixed solvent of toluene and methyl ethyl ketone were mixed and dispersed in a sand mill for about 20 hours. A magnetic paint is similarly applied onto the same non-magnetic support as in Example 1 and dried. Next, a paint containing an ultraviolet curable resin similar to that in Example 1 is applied onto the magnetic coating layer thus constructed, and then the same surface smoothing treatment is performed. After this surface smoothing treatment, ultraviolet irradiation treatment is performed using an ultraviolet irradiation device to cause a surface hardening reaction. Finally, a magnetic recording medium is manufactured in the same manner as in Example 1. Example 3 On the magnetic coating layer prepared in Example 1, 10 parts by weight of dimethylamino methacrylate, 5 parts by weight of polyurethane acrylate (molecular weight approximately 5000), 7 parts by weight of trimethylolpropane triacrylate, and 5 parts by weight of trilauryl phosphate. , apply a paint consisting of 100 parts by weight of toluene to a thickness of approximately 0.2 μm,
Then, the same surface smoothing treatment as in Example 1 is performed. After this surface smoothing treatment, an electron beam irradiation treatment of 10 Mrad was performed using an electron beam irradiation device to perform a surface hardening reaction, and then a heat treatment similar to that in Example 1 was performed to perform a thermosetting reaction. Close. Finally, a magnetic recording medium is manufactured in the same manner as in Example 1. Comparative Example 1 A magnetic recording medium is produced in the same manner as in Example 1 without using the ultraviolet curable resin. Comparative Example 2 A magnetic recording medium is produced in the same manner as in Example 2 without using the ultraviolet curable resin. Comparative Example 3 In Example 1, before applying a paint containing an ultraviolet curable resin onto the magnetic coating layer, the surface of the magnetic film layer was smoothed, and after a thermosetting reaction was performed, ultraviolet rays were applied. A paint containing a curable resin is applied, and a similar ultraviolet irradiation treatment is performed to effect a surface curing reaction, and finally a magnetic recording medium is produced in the same manner as in Example 1. Comparative Example 4 In Example 2, the surface of the magnetic coating layer was smoothed before the coating containing an ultraviolet curable resin was applied onto the magnetic coating layer, and then the coating containing an ultraviolet curable resin was applied. Then, a similar ultraviolet irradiation treatment is applied to cause a surface hardening reaction.
Finally, a magnetic recording medium is produced in the same manner as in Example 2. Comparative Example 5 In Example 1, 90 parts by weight of polyvinyl formal was used instead of the paint containing the ultraviolet curable resin.
10 parts by weight of melamine resin, isopropyl alcohol
A thermosetting resin paint consisting of 200 parts by weight was similarly coated on the magnetic coating layer, and then subjected to surface smoothing treatment and heat curing treatment at 50°C for 48 hours.
Finally, a magnetic recording medium is produced in the same manner as in Example 1. Comparative Example 6 100 parts by weight of Co-containing γ-Fe ₂ O ₃ , vinyl chloride-vinyl acetate-vinyl alcohol copolymer (U.S.
10 parts by weight of VAGH (manufactured by CC), 10 parts by weight of polyurethane elastomer (manufactured by Nippon Polyurethane Kogyo Co., Ltd.)
N2304) 10 parts by weight, lecithin 1 part by weight, carbon black 5 parts by weight, alumina powder 5 parts by weight, CH ₂
= 1 part by weight of CHCOOC ₁₃ H ₂₇ and 300 parts by weight of a solvent were mixed and dispersed in a sand mill for about 20 hours, and 5 parts by weight of polyisocyanate (Coronate L manufactured by Nippon Polyurethane Industry Co., Ltd.) was added as a hardening agent.
This magnetic paint was applied on the same non-magnetic support as in Example 3, and after drying, the surface was smoothed in the same manner, and then subjected to the same electron beam treatment as in Example 3, and then finally carried out. A magnetic recording medium is produced in the same manner as in Example 3. [Characteristics] Regarding the magnetic recording media obtained in each of the above examples, the number of passes (durability), the occurrence of scratches due to surface polishing, and the output of the 2F signal were investigated as shown in the table.

〔effect〕

本発明に係る磁気記録媒体の製造法は、非磁性
支持体上に磁性粉及びバインダを含む磁性層を塗
設し、さらに前記磁性層上に紫外線硬化型樹脂又
は電子線硬化型樹脂を含む保護層を塗設してなる
磁気記録媒体の製造法であつて、前記保護層に紫
外線又はい子線を照射して硬化処理を行つた後
に、前記磁性層の熱硬化処理を行うので、得られ
る磁気記録媒体の磁性塗膜層表面には紫外線硬化
型樹脂又は電子線硬化型樹脂の保護膜が設けられ
ているから耐久性及び耐摩耗性に富んでおり、
又、表面平滑化処理の前に紫外線硬化型樹脂又は
電子線硬化型樹脂を含む塗料を磁性塗膜層上に塗
布するので、紫外線硬化型樹脂又は電子線硬化型
樹脂の保護膜層によるスペーシングロスで再生出
力が低下するといつたことはほとんどなく、又、
製造に際してブロツキングが起きることもない等
の特長を有する。 The method for producing a magnetic recording medium according to the present invention includes coating a magnetic layer containing magnetic powder and a binder on a non-magnetic support, and further coating the magnetic layer with a protective layer containing an ultraviolet curable resin or an electron beam curable resin. A method for producing a magnetic recording medium formed by coating a layer, in which the protective layer is hardened by irradiating ultraviolet rays or insulating beams, and then the magnetic layer is subjected to a thermosetting treatment, so that the magnetic layer is obtained. Since the surface of the magnetic coating layer of the magnetic recording medium is provided with a protective film of ultraviolet curable resin or electron beam curable resin, it is highly durable and wear resistant.
In addition, since a paint containing an ultraviolet curable resin or an electron beam curable resin is applied onto the magnetic coating layer before the surface smoothing treatment, spacing due to the protective film layer of the ultraviolet curable resin or electron beam curable resin is applied. I have rarely experienced a drop in playback output due to loss, and
It has features such as no blocking occurring during manufacturing.

Claims

[Claims]

1. A magnetic recording medium in which a magnetic layer containing magnetic powder and a binder is coated on a non-magnetic support, and a protective layer containing an ultraviolet curable resin or an electron beam curable resin is further coated on the magnetic layer. 1. A method for manufacturing a magnetic recording medium, the method comprising: curing the protective layer by irradiating the protective layer with ultraviolet rays or electron beams, and then subjecting the magnetic layer to a thermosetting process.