JPH02132633A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a medium with excellent durability and to avoid contraction deformation during a coating layer cured by using a binder essentially comprising specific polyurethane resin and zero or very little amount of a crosslinking agent and providing the coating layer which contains the binder on at least one side of the medium. CONSTITUTION:The coating layer is provided on at least one side of the medium and the binder component of the layer contains 40wt.% or more cyclohexane polyurethane resin and 0-10wt.% crosslinking agent. Particularly, in an preferable embodiment, the coating layer is a magnetic layer or a back coating layer. When such polyurethane resin having specific molecular structures is used as a binder component in a coating layer, the coating layer has enough strength even with very small amount of crosslinking agent. By this method, deterioration of the toughness or contraction deformation during curing can be avoided and the medium has excellent durability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, such as a magnetic tape or a magnetic disk, which includes a magnetic layer on a non-magnetic support.

[Conventional technology]

This type of magnetic recording media includes those that have a coated magnetic layer made of oxide magnetic powder or metal magnetic powder bound with a binder on a non-magnetic support such as a polyester film, and those that have a coated magnetic layer on a non-magnetic support such as a polyester film, and those that have a coated magnetic layer on a non-magnetic support such as a polyester film. It is known that a magnetic layer is provided with a vapor-deposited magnetic layer made of a thin metal film. In addition, in magnetic tapes, in order to improve running stability and prevent static electricity, non-magnetic inorganic powder and conductive powder are bound together with a binder on the back surface of the support, that is, the surface opposite to the magnetic layer. Some products are provided with a back coat layer.

The binder components of the above-mentioned coated magnetic layer and back coat layer include polyurethane resin, vinyl chloride-vinyl acetate copolymer, polyester resin, petitral resin, vinylidene chloride resin, phenol resin, and amine resin. Polyurethane resins are used singly or in a mixture of two or more types, and among these, polyurethane resins in particular are said to provide coating films with good abrasion resistance.

In addition, in recent years, polymers having polar groups such as OH groups, COOH groups, and NH groups are used as at least a part of the above binder components, and low molecular weight polyfunctional isocyanate compounds are used in combination as crosslinking agents. , a three-dimensional network structure is formed in the layer through crosslinking due to the reaction between the above polar groups and isocyanate groups, increasing the mechanical and physical strength of the coating film and improving abrasion resistance, heat resistance, solvent resistance, etc. Improvements are generally made to improve durability (
JP-A-54-33005, JP-A-5433006,
Publications such as JP-A-5-4-3-3-7-0-2).

[Problem to be solved by the invention]

However, when the binder of the coating layer is a crosslinked type,
In order to obtain a sufficient crosslinking effect, it is necessary to use a large amount of crosslinking agent.
Approximately 30% by weight is used, but as the amount of crosslinking agent increases, the stiffness of the coating film increases due to the increase in crosslink density, but on the other hand, the toughness decreases due to the increase in the number of small molecular weight bonds in the layer. The coating deteriorates and becomes brittle, and the coating film tends to break due to external forces such as shearing force and impact force, and also tends to shrink and deform during curing. This trend is
This was remarkable even when a normal polyurethane resin, which is said to have a large effect of improving wear resistance as a polymer having a polar group, was used.

Therefore, even if both the coated magnetic layer and the backcoat layer of conventional magnetic recording media are crosslinked to improve durability by increasing the crosslinking density, the improvement effect will not be achieved, especially due to the negative effect of the decrease in toughness mentioned above. There is a natural limit to the magnetic layer, for example, in the still characteristics of a videotape, sufficient results cannot be obtained, and the back coat layer is prone to abrasion, and the abraded powder transfers to the surface of the magnetic layer, increasing dropout. There was the problem of inviting

It should be noted that if the amount of crosslinking agent used is reduced, it goes without saying that rigidity will be insufficient due to a decrease in crosslinking density, and thermal properties such as low glass transition temperature and flow temperature, which are characteristics of uncrosslinked binders, will appear as a drawback. , the durability deteriorates further, and more uncrosslinked binder components remain, so during recording and reloading, the friction coefficient against the magnetic head in the magnetic layer and the running guide system in the back coat layer tends to fluctuate partially, resulting in poor running stability. In addition, in magnetic tapes having both of the above layers, blocking may occur at the interface between the magnetic layer and the back coat layer at the same time as winding.

In view of the above-mentioned circumstances, this invention prevents coating layers of magnetic recording media, such as coating-type magnetic layers and backcoat layers, from causing a decrease in toughness and shrinkage deformation during curing as in conventional cross-linked types. The aim is to provide greater rigidity and achieve far superior durability compared to conventional products.

[Means to solve the problem]

As a result of intensive studies to achieve the above object, the inventors discovered that polyurethane having a specific molecular structure can be used as a binder component of coating layers in magnetic recording media such as coated magnetic layers and back coat layers. When resin is used, sufficient rigidity can be imparted to the coating layer even if the amount of crosslinking agent used is very small, or even if no crosslinking agent is used at all. The present inventors have discovered that a decrease in toughness due to use and shrinkage deformation during curing can be avoided, thereby providing a high-quality magnetic recording medium with extremely excellent durability, and have thus come up with the present invention.

That is, the present invention provides a magnetic recording medium having a magnetic layer on a non-magnetic support.
The present invention relates to a magnetic recording medium characterized by having a coating layer containing 40% by weight or more of a cyclohexane ring-containing polyurethane resin and 0 to less than 10% by weight of a crosslinking agent in a binder component, and in this medium, in particular, the above-mentioned Preferred embodiments include a configuration in which the coating layer is a magnetic layer and a configuration in which the coating layer is a back coat layer.

[Structure and operation of the invention]

The magnetic recording medium targeted by this invention has a coating layer on at least one of the front and back surfaces, and the magnetic layer is a coated type in which the magnetic layer is formed by coating a paint containing magnetic powder on a non-magnetic support. It includes both a magnetic metal thin film and a vapor deposition type in which a magnetic metal thin film is formed by vapor deposition on the same support. The coating layer referred to here refers to the above-mentioned coated magnetic layer and the back surface formed on the back surface of the non-magnetic support, that is, the surface opposite to the surface on which the magnetic layer is provided, for the purpose of improving running stability. A typical coating layer is a top coat layer, which is sometimes provided on the surface of the magnetic layer for the purpose of imparting lubricity, surface protection, corrosion prevention, etc., and a layer between the magnetic layer and the support. It also includes an intermediate layer that may be provided for the purpose of imparting conductivity, light-shielding properties, buffering properties, etc.

The greatest feature of this invention is the use of a cyclohexane ring-containing polyurethane resin as the binder component of the coating layer as described above, which allows the amount of crosslinking agent to be used in the binder component to be extremely reduced. Even without using any cross-linking agent, sufficient rigidity and toughness are imparted to the coating layer, and the coating layer has high elasticity, high breaking strength, and large elongation, which increases its durability. Consequently, the durability of the magnetic recording medium as a whole is significantly improved. Furthermore, in the present invention, since the amount of crosslinking agent can be reduced or eliminated as described above, it is possible to completely prevent shrinkage and deformation during curing of the coating layer.

The reason for the excellent durability described above is not clear, but the polymer molecules of the polyurethane resin mainly consist of a relatively hard part consisting of a cyclohexane ring, that is, a hard segment, and a linear structure without this cyclohexane ring. The rigidity of the coating film, which was conventionally imparted by increasing the crosslinking density, is carried by the hard segments. By doing so, the formation of a large amount of small molecular weight binders and the resulting embrittlement of the coating film due to the conventional combination of a large amount of crosslinking agent can be avoided, and the flexibility and elasticity of the soft segment directly appears as the toughness of the coating film. As a result of the above-mentioned rigidity and toughness being expressed in a well-balanced manner, a coating layer having excellent mechanical properties such as hardness and abrasion resistance as well as physical properties such as heat resistance and solvent resistance can be obtained. It is estimated that the durability of the material will be significantly improved.

The above-mentioned cyclohexane ring-containing polyurethane resins include those in which the cyclohexane ring is bonded to the terminal or main chain of the polymer molecule as a cyclohexyl group, those in which the cyclohexane ring is bonded to the chain structure of the polymer molecule as a cyclohexylene group, and both of these groups. It can be any of the following. The content of such cyclohexane rings is 1.0 to 2.8
It is preferably on the order of mmol/g; if it is too small, the ratio of hard segments will decrease, resulting in insufficient rigidity of the coating film, and if it is too large, the ratio of soft segments will decrease, resulting in insufficient toughness of the coating film.

In addition, the number average molecular weight of this polyurethane resin is 30,
A value of about 000 to 50,000 is suitable; if it is too small, both the mechanical and physical properties of the coating layer will deteriorate, and if it is too large, the magnetic powder and non-magnetic powder blended in the layer will deteriorate. This causes problems in the dispersibility of solid powders such as magnetic inorganic powders and conductive powders, and makes it difficult to form them into paints.

In order to obtain such a cyclohexane ring-containing polyurethane resin, a cyclohexane ring-containing component may be used for at least a portion of one or both of the above components when synthesizing the polyurethane resin from a polyol component and a polyisocyanate component. In addition, in order to obtain a polyurethane resin that imparts sufficient toughness and mechanical strength to the coating layer, at least a portion of the above polyol components should include polyester polyol, polyether polyol, polyurethane polyol, polyprolactone polyol, It is desirable to use high molecular weight polyols such as polycarbonate polyols.

The cyclohexane ring-containing polyol component includes cyclohexane-1-2-diol as a low molecular weight polyol,
Cyclohexane-1,3-diol, cyclohexane-1
・4-diol, cyclohexane-1,2,3-triol, cyclohexane-1,2,4-triol, cyclohexane-1,3,5-triol, etc. may be used, or a cyclohexane ring may be used as a high molecular weight polyol. You may use the one containing.

High molecular weight polyols containing a cyclohexane ring are synthesized from raw materials such as polybasic acids and polyhydric alcohols for polyester polyols, polyhydric alcohols for polyether polyols, and polyisocyanate compounds and at least part of polyhydric alcohols for polyurethane polyols. can be easily obtained by using a compound containing a cyclohexane ring.

Examples of the polybasic acid containing a cyclohexane ring include hexahydrophthalic acid, hexahydro-isophthalic acid, and hexahydro-terephthalic acid, and examples of the polyhydric alcohol containing a cyclohexane ring include the same low molecular weight polyols as mentioned above.

In addition, the raw material components of the cyclohexane ring-containing polyurethane resin used in the present invention naturally include, in addition to the cyclohexane ring-containing component described above, a polyol component and a polyisocyanate component that do not contain a cyclohexane ring. Is it used in the synthesis of polyurethane resin? Any of the raw material components can be used.

Suitable commercial products of the cyclohexane ring-containing polyurethane resin used in this invention include Resin CA-139 (cyclohexane ring content 2.7 mmol/g, number average molecular weight i 134,000) manufactured by Morton Co., Ltd.;
118 (same content 2.8 mmol/g, number average molecular weight 37.000), and other B. F (；■od
Estan-5706 manufactured by Rich (cyclohexane ring content 4.0 mmol/g, number average molecular weight 50,000
)and so on.

In this invention, the above cyclohexane ring-containing polyurethane resin accounts for 40% by weight or more, preferably 50% by weight or more of the binder component of the coating layer. That is, if the amount of the polyurethane resin in the binder component is less than 40%, the above-mentioned effects will not be sufficiently exhibited, and the durability of the coating layer and the magnetic recording medium as a whole will deteriorate.

Further, in this invention, a crosslinking agent may or may not be blended into the binder of the coating layer, but when blended, the amount used is preferably less than 10% by weight of the binder component as described above. should be less than 5% by weight. That is, in the magnetic recording medium of the present invention, the rigidity of the coating layer is sufficiently supported by the hard segments of the polyurethane resin, so if the amount of crosslinking agent used is 10% by weight or more in the binder component, the rigidity becomes excessive, causing a relative decrease in toughness and, on the contrary, deteriorating durability.

As the above-mentioned crosslinking agent, a polyfunctional isocyanate compound, which has conventionally been widely used as a crosslinking agent for binders containing polar group-containing polymers such as polyurethane resins, is suitably used.

As such a polyfunctional isocyanate compound, any compound having two or more isocyanate groups in the molecule can be used, but in particular, 3 moles of a diisocyanate such as tolylene diisocyanate or hexamethylene diisocyanate and trimethylol can be used. Preferred compounds include reactants with 1 mole of propane, polyphenylmethane polyisocyanates, modified diphenylmethane diisocyanates, and the like.

These compounds are available from Nippon Polyurethane ■ as "Coronate", "Coronet HLJ", [Coronet 2030J,
[With product names such as Millionate MRJ and Millionate MTLJ, "Desmodule Shi", "Desmodule N", and "Desmodule IL" are manufactured by Sumitomo Bayer Urethane ■.
It is commercially available from Takeda Pharmaceutical Co., Ltd. under the trade names of Takenate D-102J, Takenate D-110NJ, Takenate D-202J, etc., under trade names such as Desmodur HLJ.

In addition, in the present invention, polymers that can be used in combination with the above-mentioned cyclohexane ring-containing polyurethane resin as a binder component of the coating layer are not particularly limited, and include cellulose resins such as nitrocellulose, polar groups such as hydroxyl groups and carboxyl groups Examples include vinyl chloride-vinyl acetate copolymers that contain or do not contain cyclohexane rings, ordinary polyurethane resins that do not contain cyclohexane rings, phenol resins, amino resins, polyester resins, and butyral resins. When using the above-mentioned crosslinking agent, it is particularly recommended to use a polymer containing a polar group.

In order to form the above coating layer in the present invention, a binder component containing a cyclohexane ring-containing polyurethane resin, optionally less than 10% by weight of a crosslinking agent, and 60% by weight or less of other polymers, and A paint is prepared by adding and mixing other ingredients required depending on the type into an organic solvent, and this paint is applied to a non-magnetic support such as a polyester film or a layer previously formed on it. When the coating layer is a coated magnetic layer, which can be applied to the surface and dried, the other ingredients mentioned above include magnetic powder as an essential component, as well as fatty acids and their esters, which are added as necessary. Dispersants such as
Lubricants such as silicone oil and fluorine oil, Aez
Os powder, Cr203 powder, Si3N4 powder, SiC powder, Si
There are various additives conventionally known for use in magnetic coatings, such as abrasives such as O2 powder, and antistatic agents such as carbon black and graphite powder.

As the above-mentioned magnetic powder, any of those conventionally known as magnetic recording elements for magnetic recording media can be used, such as Fe, CO, Ni, alloys of these, other metals, or small amounts of non-metals. Metal powder consisting of an alloy containing elements, or r Fe2 0:
l , F e= Oa , these intermediate oxides, CO
Containing 7-Fe,03, CO containing Fe30. Examples include acicular iron oxide powder such as ferrite, hexagonal plate-shaped ferrite powder such as barium ferrite, and strontium ferrite.

Among the above magnetic powders, needle-shaped powders usually have an average major axis diameter of about 0.20 to 0.30 μm and an average axial ratio (average major axis diameter/average minor axis diameter) of about 6 to 10. preferable. In addition, the average particle size of plate-shaped powder is 0.05 to 0.10μ.
A material of the order of m is preferably used. The amount of these magnetic powders used is usually in the range of about 380 to 420% by weight based on the binder.

When the coating layer is a back coat layer, the above-mentioned compounding agent usually has an average particle size of 0.05 mm, which imparts an appropriate surface roughness to the layer surface and provides a reinforcing effect. There are nonmagnetic inorganic compound powders with a particle size of about 3 to 0.8 μm, and conductive powders such as carbon black, which plays a role in preventing static electricity, and whose average particle size is usually about 5 to 50 mm. In addition to these, other compounding agents that may be used as needed include the same lubricants and dispersants as in the case of the magnetic layer.

As the above-mentioned inorganic compound powder, any of various non-magnetic powders conventionally blended into the back coat layer of magnetic recording media can be used.
! , (:r203 , TiOz, (X F(3z
o3, BaSO4, CaCO, , BaCO3, M
Examples include powders such as gCO* and S i C, and two or more of these may be used in combination.

The amount of the inorganic compound powder and the conductive powder to be used is preferably such that the total amount of both accounts for 30 to 80% by weight of the entire back coat layer, and if it is too small, the strength of the back coat layer will be insufficient. On the other hand, if the amount is too large, the binding force of the binder decreases and powder falls off easily.

When the coating layer is a top coat layer formed on the magnetic layer, the above-mentioned compounding agents include a lubricant similar to the above, which is responsible for reducing the coefficient of friction on the surface of the magnetic layer, and a lubricant similar to the above, which is responsible for reducing the coefficient of friction on the surface of the magnetic layer. Rust inhibitors, such as nitrogen-containing heterocyclic compounds such as penzotriazole and aliphatic amines such as triethanolamine, which are used for the purpose of preventing corrosion of the metal magnetic materials used when the coating type is used, can be mentioned. Further, when the coating layer is an intermediate layer interposed between a non-magnetic support and a magnetic layer, the compounding agent may include conductive fine powder such as carbon black, graphite powder, metal powder, dispersion of the same as above. Examples include agents.

Examples of the above-mentioned organic solvents for paint preparation include methyl ethyl ketone and cyclohexanone, ester solvents such as ethyl acetate, isobrobyl alcohol and other alcohol solvents, and toluene and other aromatic hydrocarbon solvents. can be used, and two or more of these may be used in combination.

When the coating layer is the above-mentioned magnetic layer, the film thickness is generally about 2.0 to 3.0 μm, and when it is the above-mentioned back coat layer, the film thickness is usually about 0.0 μm. The thickness is preferably about 3 to 1.0 μm. Further, in the case of a top coat layer, an intermediate layer, etc., the normal film thickness is appropriately set depending on each layer.

In addition, the metal magnetic materials constituting the vapor-deposited magnetic layer include:
Ferromagnetic metals such as C, O, Ni, and Fe, alloys of these metals, alloys of these metals with other metals such as Cu, Zn, Mn, Cr, and Al, or these containing small amounts of nonmetallic elements. There are things like that. The thickness of this magnetic layer is generally 0. The thickness is approximately 1 to 0.2 μm.

As is clear from what has already been described, the magnetic recording medium of the present invention includes a coated magnetic layer, a back coat layer, a top coat layer, and a coating layer using a binder containing the cyclohexane ring-containing polyurethane resin. , an intermediate layer, etc., on at least one of the front and back surfaces. For example, even if the magnetic layer does not have a back coat layer or the magnetic layer is a vapor deposition type, the back coat layer and/or top coat layer may be provided. Those who have are also included. In addition, for magnetic recording media that have multiple coating layers, it is desirable to use the above polyurethane resin for all of the coating layers, but even if it is applied to only a portion of the coating layer, the durability will be improved commensurately. Effects can be obtained.

As a preferred embodiment of this invention, by using the above-mentioned polyurethane resin for the coated magnetic layer and back coat layer, particularly high durability can be obtained, and the still characteristics etc. of the magnetic layer are significantly improved. However, the back coat layer prevents abrasion and significantly reduces dropouts due to wear particles.

〔Effect of the invention〕

A magnetic recording medium according to the present invention is a magnetic recording medium having a magnetic layer on a non-magnetic support, and has a binder component mainly composed of a specific polyurethane resin and a crosslinking agent in an amount of zero or very small on at least one of the front and back surfaces. This coating layer has both high rigidity and toughness, so it exhibits extremely high durability and completely avoids shrinkage and deformation during curing of the coating layer. be done.

In addition, in a structure in which the coating layer is a coated magnetic layer and/or a back coat layer, the above-mentioned durability improvement effect is particularly large, and the magnetic layer significantly improves still characteristics, and the pack coat layer significantly improves the durability. Scraping is prevented and dropouts due to wear particles are significantly reduced.

〔Example〕

Hereinafter, the present invention will be explained in more detail by describing examples. In addition, in the following, parts mean parts by weight.

The components used in the binders of the magnetic layers of Examples 1 to 3 and Comparative Examples 1 to 5 and the back coat layers of Examples 4 to 7 and Comparative Examples 6 to 9 are as follows.

b4; Number average weight per thousand weight approximately 24,000) Examples 1 to 3 Binder components (listed in Table 1) 50 parts n-butyl stearate 2 parts myristic acid
Bipartite cyclohexanone 18
0 parts Toluene 180 parts A magnetic paint having the above composition was applied to a non-magnetic support made of a polyethylene terephthalate film with a dry thickness of 3.0 μm and a thickness of 10 μm.
Apply so that it becomes m. It was dried to form a magnetic layer, calendered, and then cut into 8 mm widths to produce video tapes.

Comparative Examples 1 to 5 Video tapes were produced in the same manner as Examples 1 to 3, except that the binder component had the composition shown in Table 1 below.

For each of the video tapes of Examples 1 to 3 and Comparative Examples 1 to 5, the still characteristics were determined by incorporating the tape into a video cassette and playing it in still mode using an 81m video deck, and the playback output level was set to the initial value. From lo
When the time (minutes) until the dB decrease was measured, the results shown in Table 1 below were obtained. In addition, in order to find out the binder properties of the magnetic layer, we prepared a 20 μm thick clear film consisting only of the binder component used in each of the magnetic layers in the above Examples and Comparative Examples, and measured its Young's modulus, breaking strength, and elongation. did. The results are added to Table 1 below.

From the results in Table 1 above, it can be seen that in the video tapes of the present invention (Examples 1 to 3) in which a cyclohexane ring-containing polyurethane resin was used as the binder component of the magnetic layer, the magnetic layer had high elasticity, high breaking strength, and elongation. It can be seen that excellent durability is exhibited based on the binder property of being large, and even when the binder is not a crosslinked type (Example 2), it shows the same durability as the crosslinked type.

On the other hand, in videotapes using ordinary polyurethane resins that do not contain cyclohexane rings as the binder component of the magnetic layer (Comparative Examples 3 to 5), good results were not obtained regardless of the amount of crosslinking agent used. In particular, when the amount of crosslinking agent is very small (Comparative Example 5), the durability is significantly inferior, and conversely, even if the amount of crosslinking agent is very large (Comparative Example 3), it is not possible to expect much improvement in durability due to the decrease in toughness. That is clear.

In addition, even when a cyclohexane ring-containing polyurethane resin is used as the same binder component, the blending ratio in the binder is too small or the amount of crosslinking agent is too large (Comparative Example 1,
It can be seen that in case 2), the excellent durability of the magnetic layer as in the videotape of the present invention cannot be obtained.

Examples 4 to 7 A back coat paint having the following composition was applied to the back of a non-magnetic support provided with a magnetic layer in the same manner as in Comparative Example 4 to a dry thickness of 1.0.
A hack coat layer was formed by coating and drying to a thickness of .mu.m, followed by calendering and cutting into 8 mm width to produce a videotape. In Examples 6 and 7, the amounts of n-butyl stearate and myristic acid, which are lubricants, were both doubled as shown below.

Binder component (listed in Table 2) Stearate n-butyl myristate cyclohexanone toluene Comparative Examples 6 to 9 50 parts 0.5 parts 0.25 parts 250 parts 250 parts As the binder component, those having the compositions listed in Table 2 below were used. Video tapes were produced in the same manner as in Examples 4 to 7, except that

For each of the video tapes of Examples 4 to 7 and Comparative Examples 6 to 9, the rate of increase in dropouts, the degree of abrasion of the back coat layer, and the degree of tape curl were examined. The results are shown in Table 2 below. The rate of increase in dropouts was determined by measuring the number of dropouts at the beginning and after running the tape 500 times using an 81m video deck.
It was expressed as the increase rate of dropouts after the run compared to the initial stage. On the other hand, the degree of abrasion was determined by visually observing the surface of the back coat layer after running, and the degree of tape curl was visually observed by visually observing the tape after production. ○ is when almost no abrasion or curl is observed, and △ is when a little is observed. The evaluation was made on a three-level scale, with "×" indicating the most significant.

From the results in Table 2 above, it can be seen that the videotapes of the present invention (Examples 4 to 7) in which a cyclohexane ring-containing polyurethane resin was used as the binder component of the back coat layer were made using ordinary polyurethane resin that does not contain a cyclohexane ring in the binder component. Compared to videotape using resin (Comparative Example 8.9),
It can be seen that the strength of the back coat layer is very high, dropout due to transfer of abrasion powder to the surface of the magnetic layer is significantly reduced, and shrinkage deformation due to hardening of the back coat layer does not occur. On the other hand, even when a cyclohexane ring-containing polyurethane resin is used as the binder component, if the blending ratio in the binder component is too low or the crosslinking agent is too large (Comparative Examples 6 and 7), the videotape of the present invention It can be seen that the excellent durability of the back coat layer cannot be obtained.

Patent applicant: Hitachi Maxell, Ltd.

Claims (3)

[Claims] (1) In a magnetic recording medium comprising a magnetic layer on a non-magnetic support, at least one of the front and back surfaces contains 40% by weight or more of a cyclohexane ring-containing polyurethane resin and 0 to less than 10% by weight of a crosslinking agent in the binder component. A magnetic recording medium characterized by having a coating layer containing. (2) The magnetic recording medium according to claim (1), wherein the coating layer is a magnetic layer. (3) Claim (1) wherein the coating layer is a back coat layer formed on the surface of the nonmagnetic support opposite to the surface on which the magnetic layer is provided.
) or the magnetic recording medium according to (2).