JPH02137117A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve electromagnetic characteristics, traveling property and durability by consisting a binder of the reaction product obtd. by making to react polyester, namely, the reaction product of a specific diol and adipic acid with the reaction product of dicarboxylic acid and 1, 4-cyclohexanedimethanol, a chain extender ternary amine and aliphat, or arom. diisocyanate. CONSTITUTION:The binder is the reaction product obtained by making to react the polyester, namely, the reaction product (A) of the diol selected from ethylene glycol, propylene glycol, etc., and adipic acid, with the reaction product (B) of the dicarboxylic acid selected from the azipic acid, azelaic acid, 1, 12 dodecanic acid, and the mixture composed thereof, and the 1, 4- cyclohexanedimethanol, the chain extender (C) consisting of the 1, 4- cyclohexanedimethanol and the ternary amine (D). The magnetic recording medium which has the high durability, the low friction and the good traveling property is obtd, in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a magnetic recording medium, and particularly to a magnetic recording medium with excellent electromagnetic properties, runnability, and durability.

(Prior Art) Conventional tape-shaped magnetic recording media are often coated with a back layer on the back surface thereof, that is, the surface opposite to the magnetic layer. As the amount of information recorded on magnetic recording media increases, recording at shorter wavelengths becomes necessary. It is well known that a back layer is used to solve problems such as friction due to a significant improvement in the surface smoothness of the layer and unwinding due to thinning of the tape. Such a back layer is formed by coating a binder mixed and dispersed with antistatic agents such as carbon black and graphite, smooth lubricants, and inorganic particles such as silicon oxide and alumina on the back surface of the support. .

Thermosetting resins, particularly thermosetting polyurethane resins, are well known as binder resins used for this purpose. That is, a polyurethane prepolymer and a polyisocyanate with an excess of OH are usually used as binder components, and inorganic powders such as lubricants, antistatic agents, and reinforcing agents are mixed and dispersed therein, and then the back side of the nonmagnetic support, that is, the magnetic It is coated on the side opposite to the side on which the layer is supported, and finally cured with heat to form a back layer. This type of back layer forms an extremely strong adhesive film, has excellent durability, and has various excellent properties such as having a good effect on the magnetic layer, but because it is a thermosetting type, it has a short pot life. Problems: Because it takes a long time to cure, there are problems such as adhesion between layers when wound into a magnetic tape, or the roughness of the back surface tends to be transferred to the magnetic surface, impairing smoothness. Therefore, it would be desirable to be able to provide a binder resin comparable to a thermosetting type without using a curing agent or a crosslinking agent.

(Object of the Invention) Therefore, the object of the present invention is to achieve an effect equivalent to or better than that of a back layer using a conventional thermosetting polyurethane binder without thermosetting or crosslinking. An object of the present invention is to provide a back layer that can provide a secondary magnetic recording medium with high strength, low friction, and good running performance.

(Summary of the Invention) The present invention provides a magnetic recording medium having a magnetic layer on a support and a back layer containing carbon black, inorganic powder, and a binder on the opposite surface, wherein the binder is (
A) Ethylene glycol, propylene glycol, 1.
4-butanediol, 1.3-butanediol, 1.5
- a polyester which is a reaction product of a diol selected from the group consisting of pentacaol, 1,6-hexanediol, and adipic acid; (B) adipic acid, azelaic acid, 1.12 dodecanoic acid; a reaction product of a dicarboxylic acid selected from the group consisting of a mixture of 1,4-cyclohexaline methanol;
a chain extender consisting of cyclohexaline methanol;
D) A magnetic recording medium characterized in that it is a reaction product of an aliphatic or aromatic diisocyanate, preferably in an amount approximately the same as the total molar amount of the polyester and chain extender, and (E) a tertiary amine. provide.

The present invention also provides (A) a diol selected from the group consisting of ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pencunediol, 1,6-hexanediol. and (B) a dicarboxylic acid selected from the group consisting of adipic acid, azelaic acid, 1,12 dodecanoic acid, and mixtures thereof, and 1,4-cyclohexalinemethanol. (C) a chain extender consisting of 1,4-cyclohexalinemethanol; and (D) an aliphatic or aromatic diisocyanate, preferably in an amount approximately equal to the total molar amount of the polyester and chain extender. (E) Carbon black and inorganic powder are mixed and dispersed in a binder made of a reaction product with a tertiary amine, and the resulting paint is applied to the opposite side of the support of the magnetic recording medium that supports the magnetic layer. Provided is a method for manufacturing a magnetic recording medium, which is characterized in that it is coated on a surface.

(Operations and Effects of the Invention) According to the present invention, a back layer having excellent properties equivalent to or better than those obtained when a conventional thermosetting polyurethane binder is used without using a curing agent is provided. Compared to the prior art described above, the dispersibility of powders such as inorganic powders is improved, and the mechanical strength of the back layer is also increased, resulting in increased durability.

(Detailed description of the invention) The invention will be explained in detail below with reference to examples.

The present invention provides the above (A), (B), and (D) or (A),
Carbon black and inorganic powder are mixed and dispersed in a binder made of the reaction products of (B), (C) and (D), and the resulting paint is applied to the surface of the support of the magnetic recording medium that supports the magnetic layer. This is a method of manufacturing a magnetic recording medium characterized by coating on opposite sides, and a magnetic recording medium obtained in this manner.

Among the above-mentioned polyurethane resins that do not use a curing agent and are suitable for the present invention, the components (A) and (B) constituting the polyester are
), (C), and (D) may be those described in Japanese Patent Publication No. 58-8053. The binder described in the above publication is used for the magnetic layer. Not used for back layer. Furthermore, the binder made of only these four components described in the above-mentioned publication does not give sufficiently satisfactory results. That is, the polyurethane resin binder described therein does not sufficiently disperse powders such as inorganic powders, and does not have sufficient strength, which causes scratches and causes problems in durability.

Component (A) is a diol selected from the group consisting of ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pencunediol, 1°6-hexanediol; It is a polyester that is a reaction product with adipic acid. The polyester is used in equivalent reactant or OH excess. The terminal hydroxyl groups obtained in the latter case react with the diisocyanate of component (C). The case of excess OH is described in the above publication. Although various dicarboxylic acids are described in the above publication, acids other than adipic acid are not very effective in the present invention.

Component (B) is a polyester which is the reaction product of 1,4-cyclohexalinemethanol and a dicarboxylic acid selected from the group consisting of adipic acid, azelaic acid, 1.12 dodecanoic acid, and mixtures thereof. The reason why two types of components are used in this way is to adjust the solubility and dispersibility in the solvent. (A) and (B) have different solubility, and appropriate dispersibility can be obtained for each. It is a combination that can be used.

Component (C) is a chain extender, and in particular must be 1,4-cyclohexaline methanol. Although various chain extenders are described in the above publication, other ones are not very effective in the present invention. None.

Component (D) reacts with the above three components and the tertiary amine to produce a binder with extremely good properties. As examples of diisocyanates, various aliphatic diisocyanates and aromatic dicyanates described in the above-mentioned publications can be used.

The tertiary amine of component (E) is an important component for improving the properties of the binder of the present invention, and as a preferable example, HO-Rt-N-Rs-0)ICR+R,:C=1 ~5 R, :C=1~1°R, :C=1~10, etc. can be used.

The inorganic powder used in the present invention may be any powder conventionally used for back layers, such as lubricants, antistatic agents, reinforcing agents, etc. Lubricants include myristic acid, stearic acid, butyl stearate, butyl myristate, etc., and reinforcing agents include Cr1O=, Q-Alias, TiOx,
a-Fat's, y-AhOs, a-5iC1β-3
EC etc. can be used.

(Explanation of Examples) In the following, component (A) is of the OH-excess type.

In addition, although MDI was used as component (D), TDI, HD
I, IPDI, NDI, etc. can be used.

Example 1 Polyurethane resin ■ (■ Polybutylene adipate and polyhexamethylene adipate, ■ Ester of 1.4 cyclohexane dimetatool and dicarboxylic acid, ■ MDI, ◎ 1,4 cyclohexane dimetatool, ■ Tertiary amine Reaction product of compound (n = 60,000, Tg = 50°C) 50 parts by weight Polyurethane resin ■ P-223 (■ Polybutylene adipate, ■ 1.4 butanediol, ■ MDI) 50 parts by weight Carbon black 10 parts by weight Lubricant
1 part by weight reinforcing agent (C manufactured by Ciba Gaiki Co., Ltd.
rz Os ) 0.3 parts by weight Polyisocyanate Nippo C-30415 parts by weight The above composition was thoroughly mixed in a disperser, cross-dispersed to make a paint, and this was dried on the back side of a magnetic recording medium having a magnetic recording layer. A back coat was formed to have a back thickness of 1.5 mm and was subjected to evaluation.

Example 2 The polyurethane resins ■ and ■ in Example 1 were each 70%
A magnetic recording medium was obtained in the same manner as in Example 1 except that 30 parts by weight were used.

Example 3 Polyurethane (Tg 85°C) @ 60 parts by weight Polyurethane p-22S ■ 40 parts by weight Others are Example 1
A magnetic recording medium was obtained in the same manner.

Example 4 Vinyl chloride/vinyl acetate/vinyl alcohol maleic acid copolymer resin 30 parts by weight Polyurethane resin 30 parts by weight Polyurethane resin 4 o parts by weight A magnetic recording medium was obtained in the same manner as in Example 1 except for the following.

Comparative Example 1 A magnetic recording medium was obtained in the same manner as in Example 1, except that vinyl chloride/vinyl acetate/vinyl alcohol maleic acid copolymer resin 50 parts by weight Polyurethane P-22S 50 parts by weight.

Comparative Example 2 Nitrified cotton resin 50 parts by weight Polyurethane P-22S 50 parts by weight A magnetic recording medium was obtained in the same manner as in Example 1 except for the following.

Comparative Example 3 Polyurethane resin @ 50 parts by weight (not containing tertiary amine compound) Polyurethane resin (2) 50 parts by weight A magnetic recording medium was obtained in the same manner as in Example 1 except for the following.

Each material corresponding to Examples 1 to 4 and Comparative Examples 1 to 3 was prepared as follows for each sample of the magnetic recording medium described above: Samples #A, #B, #C1, #D, #E, #F, #G. I conducted a test. The results are shown in Table 1 and Figure 1.

(1) Surface roughness Ra The surface roughness Ra of the coating film was measured using a stylus type surface roughness meter (Taylor Hobson Co., Ltd. surface roughness meter).

(2) Change in coefficient of dynamic friction The sample was stored at 70°C and 95% RH, taken out every day, and the back coat a side was run at 20 mm/sec on a fixed stainless steel ball surface with a diameter of 5 mmφ before storage and 7 The value after 1 day is shown.

(3) Durability after storage The running sample was stored at 70° C. and 95% RH, and was taken out every week and run on a VH3 type video tape recorder for 20 bus runs to show whether it was stored or removed when a problem occurred.

(4) Using a device that measures the dynamic friction coefficient of back coat side scratches, perform 3 in the same manner as in (2).
The appearance of scratches during the 00 pass was visually determined and shown as × for the size of the scratch, Δ for the presence of a slight scratch, and O for no scratch.

As is clear from Table 1 and Figure 1, polyurethane resin a
All magnetic recording media having back coats using the above have good characteristics. In particular, the storage properties are stable.

4. of. Figure 1 is a graph showing changes over time in the coefficient of dynamic friction of a magnetic recording medium.

Claims (4)

[Claims] (1) A magnetic recording medium having a magnetic layer on a support and a back layer containing carbon black, inorganic powder, and a binder on the opposite surface, wherein the binder is (A).
Ethylene glycol, propylene glycol, 1,4-
a polyester which is a reaction product of adipic acid and a diol selected from the group consisting of butanediol, 1,3-butanediol, 1,5-pentanediol, and 1,6-hexanediol; (B) adipine a reaction product of a dicarboxylic acid selected from the group consisting of azelaic acid, 1,12 dodecanoic acid, and mixtures thereof with 1,4-cyclohexalinemethanol;
a chain extender consisting of cyclohexaline methanol;
D) A magnetic recording medium characterized by being a reaction product with a tertiary amine. (2) In addition to components (A), (B), (C), and (D) before the reaction, it further contains an aliphatic or aromatic diisocyanate in an amount approximately the same as the total molar amount of the polyester and chain extender. The magnetic recording medium according to item 1 above. (3) (A) a diol selected from the group consisting of ethylene glycol, propylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, and 1,6-hexanediol; (B) a dicarboxylic acid selected from the group consisting of adipic acid, azelaic acid, 1,12 dodecanoic acid, and mixtures thereof;
The reaction product of 4-cyclohexaline with methanol and (
C) A chain extender consisting of 1,4-cyclohexalinemethanol and (D) a tertiary amine are reacted, carbon black and inorganic powder are mixed and dispersed in the resulting binder, and the resulting paint is mixed and dispersed. 1. A method for producing a magnetic recording medium, which comprises applying the coating to the opposite side of the magnetic layer supporting surface of the support of the magnetic recording medium. (4) In addition to the components (A), (B), (C), and (D),
4. The manufacturing method according to item 3, wherein the binder is obtained by further reacting an aliphatic or aromatic diisocyanate in an amount approximately equal to the total molar amount of the polyester and chain extender.