Tdk Corporation

Konica Corporation

Eizo Tsunoda

Hideki Tanaka

Seiichi Tobisawa

Ryuji Hosogaya

Yutaka Shimizu

Akira Hatakeyama

Yoshihisa Osawa

Kazuo Katai

Naomi Yoshiike

Katsumi Onozawa

Eiichi Watanabe

Kaoru Kawasaki

Hiroshi Kawahara

Akihiko Seki

Yoshisuke Yamakawa

Yoshihiro Honjo

Kazuyuki Shimazaki

Masujiro Seki

A magnetic paint is extrusion coated to a length of splice jointed webs through a coating head by continuously feeding the length of webs across the head. When a splice joint passes across the head, the head is moved apart from the web before passage and contacted with the web after passage. Objectionable coating portions which are formed as a result of moving the head out of and into contact with the web are scraped off by a scraping roll downstream of the head.

Extrusion coating method

The center line average roughness (Ra) of the slit inner surfaces is made in a predetermined range of 5.0 .mu.m according to the present invention, and the straightness (W1) in the delivery direction of the coating solution thereof and the straightness (W2) in the perpendicular direction to the delivery direction thereof are made in predetermined ranges respectively in preferred embodiments. Thereby, development of wrinkles and inclined elongation in the tape itself are prevented when wound on a roll, the productivity is increased, and the product quality is improved.

Extrusion type coating head

A coating apparatus having an extrusion type coating head to form a coating on the surface of a support by extruding a coating liquid continuously or successively from a slit, wherein the slit is tapered so as to expand or become wider gradually from its inlet end so as to allow the coating liquid to be extruded toward its outlet end and apply the coating liquid onto the surface of the support and wherein an opening slit width (d1) at the inlet end of the slit and an opening slit width (d2) at the outlet end thereof satisfies the following relations:

Coating apparatus

In a coating apparatus having an extrusion coating head, the working value H of a back end edge which corresponds to an end portion at the downstream side of a support feeding direction of a back edge of the extrusion coating head is set to 25 .mu.m or less, and the straightness of said back end edge with respect to the coating width is set to 5 .mu.m or less. Accordingly, a coating operation to form coated films at a stable thickness can be stably performed without occurrence of streaks and coating unevenness on the films, and a judgment on coating surface characteristics can be readily performed without actually carrying the coating operation.

An extrusion coating head which is disposed between a drier for performing a non-contact drying operation and a support roll located at the upstream side of and nearest to the drier is designed so that a back edge surface thereof is designed to have an round surface having a radius of curvature R which satisfies the following inequality: 3 mm.ltoreq.R.ltoreq.30 mm, and the entire R-surface portion of the back edge of the coating head is located at a position higher than a tangential line drawn to the front edge surface at a slit-side edge point of the front edge so as to project toward the web side. The running web is coated with the coating liquid by the extrusion-type coating head, and then dried through a non-contact drying process.

Extrusion coating method and coating apparatus for coating both sides of

In an extrusion type coating head according to the present invention, a center line average roughness (Ra) of an inner wall surface of a pocket is made in a predetermined range of 3.5 .mu.m or less and preferably a curvature part is provided, in the part where a surface of a slit joins to a surface of the pocket, which has the radius of curvature R of within a predetermined range. By these configurations, an easiness of cleaning in the pocket of the extrusion type coating head which is difficult to be cleaned is remarkably improved in particular, the rate of operation is improved, labor is saved, and adverse effects are prevented that might be brought by insufficient cleaning on the product coating such as streak generated on the coating surface and thickness fluctuation in the coating.

A magnetic recording medium records two or more signals having different frequency bands by frequency multiplex recording. The non-magnetic substrate includes a first magnetic layer and a second magnetic layer on that order, said second magnetic layer having a thickness amounting to 70% or less of the shortest recording wavelength of the signals to be recorded.

Magnetic recording media and method for making them

In a coating method of extruding a coating liquid through a slit of an extrusion-type coating head to coat a running web, at a starting or restarting of the coating, the coating liquid is extruded through the slit of the coating head while the coating head is away from the web, and then the coating is started while a slightly large clearance is kept between the coating head and the web at the upstream side of the coating head, thereafter changing the coating state or arrangement to a steady coating state. Therefore, occurrence of a thicker portion of the coating film on the web at the start of the coating can be prevented. Further, at the end or interruption of the coating, the coating state or arrangement of the coating head is changed from the steady coating state to a state wherein a slightly large clearance is kept between the coating head and the web at the upstream side, and the coating head is moved away from the web to end the coating. Therefore, occurrence of a thicker portion of the coating film on the web at the end of the coating can be prevented. With this arrangement, at the start, restart, end and interruption of the coating, a uniformly coated film can be also formed on one surface of the web whose other surface has already been coated with a coating liquid.

Coating method

A mixture containing a magnetic powder, a binder, and an organic solvent is kneaded by passing it through a twin-shaft continuous kneader while the shearing force applied to the mixture is varied by changing the set angle of paddles used. The temperature of the mixture is controlled to be higher than Tg and lower than the boiling point of the organic solvent when it passes through the maximum shearing force zone, and to be lower than the temperature of the mixture upon its passage through the maximum shearing force zone, preferably lower than Tg when it passes through zones other than the maximum shearing force zone. There is obtained a magnetic recording medium which has improved dispersion of magnetic powder and excellent electromagnetic properties as well as a low coefficient of friction and improved transport stability.

Method for preparing magnetic recording medium

In a magnetic recording medium comprising a magnetic layer containing a magnetic powder, 5 to 20% by weight based on the weight of the magnetic powder of a non-magnetic abrasive having a Mohs hardness of at least 6, and a binder on a non-magnetic substrate, the magnetic layer becomes more durable while maintaining electromagnetic properties by distributing the abrasive in the magnetic layer such that its concentration is highest in a surface-adjoining portion and continuously decreases therefrom toward the substrate side. The medium is prepared by applying a magnetic coating to a substrate and continuously passing the coated substrate through reversing magnetic fields prior to curing of the coating.

Growing community of inventors

Komoro, Japan

Eizo Tsunoda