JPS60179938A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium which excels in the traveling performance and durability with reduced noise, by forming a back coat layer to the main surface at one side of a nonmagnetic supporter and then a magnetic layer to the other main surface of said supporter after applying the calendar processing to the surface of said back coat layer. CONSTITUTION:A back coat agent containing a pigment and a binder is applied to the main surface at one side of a nonmagnetic supporter and dried to obtain a back coat layer. Then the calendar processing is applied on the surface of the back coat layer by inserting through said nonmagnetic supporter between rolls opposite to each other under certain heating conditions with pressure. Thus the smoothness is improved on the surface of the back coat layer. Thus the back transcription is suppressed to the surface of a magnetic layer and furthermore the mechanical strength is improved. In such a way, the magnetic layer is formed to the other main surface of the nonmagnetic supporter.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic chip used in audio equipment, video equipment, computers, etc. This article relates to a method for manufacturing magnetic recording media such as magnets and magnetic sheets.

(Conventional structure and melting point) In recent years, with the trend toward compact density recording, this type of magnetic recording medium has been developed with highly smooth Attempts are being made to obtain a highly smooth magnetic layer surface using a non-magnetic support. However, the highly smooth non-magnetic support lacks runnability and durability, so there may be carcasses on the back side of the support. A back coat layer was formed of an inorganic powder such as carbon black, calcium carbonate, barium sulfate, or titanium tungsten and a resin binder.

However, although runnability is significantly improved by forming a back coat layer, dropouts increase due to shedding of inorganic powder, and furthermore, the surface protrusions of the back coat layer are imprinted, causing magnetic The layer surface becomes rough and AM
Inconveniences such as an increase in sex modulation noise have occurred.

(Object of the invention) The present invention was made in view of the runner-up of the above conventional examples, and
The present invention provides a method for manufacturing a magnetic recording medium that can produce a magnetic recording medium that has excellent runnability and durability and has less noise.

(Structure of the Invention) In order to achieve the above object, the present invention forms a back coat layer on one main surface of a non-magnetic support, and after calendering the surface of the back coat layer, A magnetic layer is formed on the other main surface of the body, and by calendering the back coat layer, the smoothness of the back coat layer surface is improved and transfer to the sulfuric layer surface is prevented. In addition to being able to suppress the occurrence of wrinkles, the back coat layer is compressed and its apparent density increases, so that its mechanical strength can be improved.

(Explanation of Examples) Examples of the present invention will be described in detail below.

First, a back coat agent consisting of a pigment and a binder is applied to a ml of non-magnetic support and dried.

A coat layer is formed. The back coating agent may be one or more of inorganic pigments such as carzen black, graphite, calcium carbonate, barium sulfate, titanium oxide, aluminum, or various organic pigments, nitrocellulose, and polyurethane.

It is dispersed in a binder such as polyester, vinyl chloride/acetate copolymer, polyimide, etc., and a dispersant, curing agent, etc. are added as necessary. Further, the particle size of the pigment is preferably 1 μm or less, and optimally 0.02 to 0.5 μm. Next, the surface of one coat layer is calendered. Here, the surface treatment is carried out by applying pressure by tracing the non-magnetic support on which the back coat layer is formed between opposing rolls under heated conditions, and the calender used for this surface treatment is It is composed of a combination of rolls, cotton rolls, resin rolls, glass rolls, ceramic rolls, etc. In addition, the calendering conditions vary depending on the combination of rolls and the number of calendering stages, but excessive calendering damages the surface of the back coat layer and increases its friction coefficient. k
g/cm and a speed VL of 10 to 200 m/'A are suitable.

After the back coat layer is calendered in this way, a magnetic layer is formed on the other main surface of the nonmagnetic support. Note that the magnetic layer may be formed using any of a coating method, a plating method, and a vapor deposition method.

Next, specific examples of the present invention will be described.

Example 1 A calendering process was carried out with an omnidirectional roll sandwiched between two resin rolls, and the number of processing stages was 22, 76. Then, using a wide base film with a thickness of 14 μm as a non-magnetic support, a back coating agent was applied to the main surface of the base film to a thickness of 1 μm and dried (after forming a coating layer, The surface of this /N Tsuku coat layer is the above calendar tree JJW
Two nitsols were calendered in contact with a roll. The calendering conditions at this time were a temperature of 70°C.
, the pressure was 1 o kg/α, and the speed was 100 m/min. After the back coat layer is calendered in this way, Co-γ-Fe 205, a binder, and additives added as necessary are added to the main surface of the base film opposite to the 142-coat layer. A magnetic paint consisting of the following was applied, oriented and dried, and this magnetic paint film was surface treated to form a medium-wide magnetic tape with a total thickness of 20 μm.

Then, this magnetic tape was wound into a roll and cut into a width of 172 inches to produce a video tape.

Example 2 A calender with one nip processing stage was constructed, consisting of a metal roll and one resin roll. Then, the back coat layer formed on the base film in the same manner as in Example 1 was calendered so as to come into contact with the metal roll of the above calender.

The calendering conditions are: temperature 40℃, pressure 5oyu/Crn.
A videotape was made with a z-speed of 10 and a speed of 1 and 0.

Comparative Example A videotape similar to Example 1 was made without calendering the backcoat layer.

And the power of Example 1, Example 2, and Comparative Example 5-
The SN ratio, the number of dropouts during 100 normal runs, and the presence or absence of moth-eaten demagnetization were investigated, and the results are shown in the table.

In addition, in the table, the color SN ratio is
Using Y-8200 (manufactured by Kenko Denki ■), input 100% chrominance signal to 925D color video noise measuring device (manufactured by Shibaku), measure the 8N ratio when using 1k-50014 (z filter), and compare. The example is OdB and the relative value of both examples is shown.The number of dropouts is VH
Using an 8-system VTR, NY-8200, instantaneous dropouts (15 μs, 16 dB) in the video playback signal were measured with a dropout counter, and the average value over 1 minute is shown.

Moth-eaten demagnetization is V'H8 method VTR.

Using NV-8200, the enperoso of the video reproduction signal was observed with an oscilloscope, and the number of missing lines of 3 dB or more was counted.

Calendering and smoothing the magnetic layer suppresses transfer marks on the magnetic layer and improves the mechanical strength of the backcoat layer, so the backcoat layer is not calendered as in the past. Compared to the comparative example, color SN
In addition to improving the ratio, dropouts and moth-eaten demagnetization can be significantly reduced.

Incidentally, although a magnetic tape has been described as an example, it goes without saying that the present invention can be applied not only to magnetic tape but also to other magnetic recording media such as magnetic sheets and magnetic cards.

(Effects of the Invention) As explained above, according to the present invention, it is possible to improve the S/N ratio of a magnetic recording medium and to suppress dropouts and moth-eaten demagnetization, thereby improving running performance, durability, and electromagnetic conversion characteristics. A magnetic recording medium with excellent properties can be easily manufactured, and its practical value is great.

Claims (1)

[Claims] A pack coating agent consisting of a fine powder and a binder is applied to one main surface of the non-magnetic support and dried to form a back coat layer, and after calendering the surface of the back coat layer, the non-magnetic support is A method of manufacturing a magnetic recording medium, comprising forming a magnetic layer on the other main surface of the magnetic recording medium.