JPS5829124A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having superior magnetic characteristics, superior surface smoothness of the magnetic layer and superior durability and contg. magnetic powder with high dispersibility and fillability by hardening a coated film contg. a specified coupling agent and a specified oligomer under radiation so as to produce the magnetic layer. CONSTITUTION:A coated film contg. a titanium coupling agent represented by the general formula, an oligomer of urethane acrylate or urethane methacrylate having urethane bond in the molecule and acrylic double bond at one or both of the terminals, and magnetic powder, is formed on a substrate and hardened by irradiation to lay a magnetic layer. Besides said oligomer, to the film may be added an oligomer obtd. by bonding acrylic acid or methacrylic acid to a terminal of polyalkylene glycol or polyol by esterification. The preferred amount of the coupling agent to be used is 0.1-10wt% of the amount of the magnetic powder in the magnetic layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and the object thereof is to have good dispersibility and filling properties of magnetic powder, excellent magnetic properties and surface smoothness of the iB underlayer, and excellent durability. The purpose of the magnetic recording medium is to provide a magnetic recording medium, which is usually made by applying a magnetic paint consisting of a magnetic powder, a binder component, an organic solvent, and other necessary components onto a substrate such as friester film, and drying it. made by
It is required to have excellent magnetic properties and surface smoothness, as well as excellent durability.

Therefore, by improving the dispersibility of the magnetic powder by selecting a binder component with excellent dispersibility of the magnetic powder, or by treating the magnetic powder with a dispersant such as alkyl titanium, the magnetic properties can be improved. Attempts have been made to improve the surface smoothness and abrasion resistance of the magnetic layer, but these methods have not yet been fully satisfactory.Furthermore, this method has the disadvantage of dissolving the binder component during the preparation of the magnetic coating. There is a problem with pollution due to the use of large amounts of organic solvents.

Therefore, in recent years, various oligomers such as urethane acrylate oligomers have been developed as a way to improve this problem. A proposed method is to prepare a magnetic paint by dispersing - with magnetic powder and other necessary ingredients, apply this magnetic paint onto a substrate, and then irradiate it with radiation to make the oligomers overlap with the radiation to form a magnetic layer. However, although this method improves the pollution-related interlayer, the improvement in the dispersibility and filling properties of the magnetic powder are still insufficient, and fully satisfactory results have not yet been obtained.

The inventors conducted various studies in view of the current situation and found that the general formula %) (in the formula, R is a hydrocarbon group, and X is 100 or -so
, -Q or -PO(OH)-0-POSY is a hydrocarbon group or →O-R, ), and R1 is an alkyl group. ), an oligomer of urethane acrylate or urethane methacrylate having a urethane bond in the molecule and an acrylic double bond at one or both ends, and magnetic powder. When a magnetic layer is formed by coating the oligomer and then irradiating it with radiation to polymerize and harden the oligomer, the dispersibility and filling properties of the magnetic powder are sufficiently improved, and the magnetic properties and the surface of the magnetic layer are improved without causing any pollution problems. The smoothness has been further improved, and the above-mentioned O! It was discovered that the magnetic properties and surface smoothness of the magnetic layer as well as durability can be further improved by using an oligomer in which acrylic at or meta-9-ru is ester bonded to the end of darylkylene glycol or polyhydric alcohol together with sesame. He came up with an invention.

When the titanium coupling agent of the general formula used in this invention comes into contact with magnetic powder, it reacts strongly with the water enzymatic group on the surface of the powder particles, and the bond between the titanium atom and -OR is broken, and the titanium atom becomes magnetic. It is strongly bonded to the powder surface via oxygen. Therefore, when this type of titanium coupling agent is contained in the magnetic layer, it adheres firmly to the particle surface of the magnetic powder, forming a film and sufficiently improving the dispersibility of the magnetic powder. Since the coupling agent is particularly effective in reducing the viscosity of the magnetic paint, it can sufficiently improve the filling properties of the magnetic powder, thereby further improving the magnetic properties and surface smoothness of the magnetic layer. As a specific example of such a titanium coupling agent, for example, Kenritshipe)-Prenact TTiPlenac) 9, manufactured by Chemical Co., Ltd., is represented by the following structural formula.
O PreneAc) 95 (Isopropyl tridecylpene (sulfonyl titanate)) PreneAc) 388 (Isopropyl tridecyl titanate) (Diotatylbairo Honsufuni)) Titanate] These titanium coupling agents can be prepared by dissolving them in a suitable solvent and adding the solution obtained by this dissolution when preparing magnetic paint, or by adding magnetic powder to this solution. It is contained in a magnetic paint by a method such as pre-surface treatment of magnetic powder by soaking in the magnetic powder, and preparing a magnetic paint using this magnetic powder.
used. The amount used is α1 based on the magnetic powder in the magnetic layer.
If the weight is too low, the desired effect will not be obtained, and if the weight is 10 -
If it exceeds a1~, there is a risk of bleed-out.
It is preferably within the range of 10 weight strokes, 0.5 to 5
It is more preferable to use within the range of parts by weight.

In addition, oligomers of urethane acrylate (urethane acrylate) or urethane methacrylate (urethane acrylate) or urethane methacrylate (urethane acrylate or urethane methacrylate) having a urethane bond in the molecule and an acrylic type or a double bond at one or both ends, which are used in the present invention, include, for example, the general formula: , k is H or CH3, and m is an integer from 1 to 1O.) Those having a molecular weight of soo-go or ooo are preferably used. ☆Rethane Atari Relay) Kai or Urethane Methacrylate Resioligo! The structure of - is not limited to this, but isol compounds such as preethers, preesters, and preols, isocyanate compounds such as 2.4-) luene diincyane F1 hequinamethylene diisocyanesi, and adipine san. A urethane oligomer made of a dibasic acid or the like may have an ac9yl double bond at the end or both ends. This kind of urethane acrylate or urethane methacrylate oligo!
- When used in combination with the titanium coupling agent mentioned above, the viscosity is lowered, so the filling properties of the magnetic powder are sufficiently improved, and the magnetic properties and surface smoothness of the magnetic layer are further improved. In addition, when the substrate is coated with magnetic powder and the titanium coupling agent and then irradiated with radiation, the double bonds at both ends open and cross-link, forming an appropriately polymerized and hardened magnetic layer. It is also highly praised for its wear resistance.

It is preferable that the amount used is within the range of 20 to 60% by weight based on the total amount of magnetic powder and 9. If it is too small, the desired effect will not be obtained, and if it is too large, the content of magnetic powder will be low. If it becomes too much, good electromagnetic conversion characteristics cannot be obtained.

In this invention, oligo of urethane acrylate or urethane methacrylate! An oligomer in which acrylic acid type or methacrylic acid is ester bonded to the end of polyalkylene glycol used together with - has the general formula α-C-■-←0-R8 key OCR.

(However, CM or CM is a hydrocarbon group, and I is an integer of 1-!!@) Oligo! -, molecular weight 100~tso.

The latter is preferably used, and the oligomer in which acrylic acid or methacrylic acid is ester-bonded to the terminal of a polyhydric alcohol has the general formula % Kyl group, R, OR or R40R, and at least one of them is used. The above is necessarily R4OR, where R1 and R4 are hydrocarbon groups, and R1 is CH, -CH-Co- or CHs
-C(CHI) -C0-1P is an integer from 1 to 10. ) Oligomers having a molecular weight of 100 to 2,000 are preferably used. This type of oligomer, in which acrylic acid or methacrylic acid is ester-bonded to the end of polyalkylene glycol or polyhydric alcohol, has a coating hardness that changes depending on the degree of polymerization of the polyalkylene glycol. When the degree is 7 or less, it becomes hard. This kind of oligo with such low viscosity! When - is used in combination with the relatively high viscosity urethane acrylate or urethane methacrylate F oligomer, the viscosity of the mixed base oligomer is adjusted appropriately - and the titanium coupling agent is further used in combination with this. The viscosity is appropriately reduced, the dispersibility and filling properties of the magnetic powder are improved, and the magnetic properties and surface smoothness of the magnetic layer are further improved. Furthermore, after these oligomers are coated on a substrate together with magnetic powder and the titanium coupling agent mentioned above, when radiation is irradiated, the double bond at the end of each oligomer opens and the same or different oligomers are cross-linked and used together. The hardness is also improved by the oligomer with low viscosity and hardness, and a polymerized and hardened magnetic layer with appropriate elasticity is formed, and the wear resistance of the magnetic layer is also improved by two steps.

The mixing ratio of the oligomer of polyalkylene glycol or polyhydric alcohol with acrylic acid or methacrylic acid ester-bonded to the oligomer of urethane acrylate or urethane methacrylate is within the range of 1:3 to 3:1 on a heavy duty basis. If the oligomer content of urethane acrylate F or urethane methacrylate resin is too small, the abrasion resistance of the coating film will decrease, and if it is too large, the viscosity of the oligomer will become too high, which will affect the dispersibility and filling of the magnetic powder. Not sexual enough. In addition, the amount of oligomer mixed with both is 2 times the total amount of magnetic powder.
The amount is preferably in the range of 0 to 60% by weight; if it is too small, the desired effect cannot be obtained, and if it is too large, the content of magnetic powder becomes too low and good electromagnetic conversion characteristics cannot be obtained.

Said oligo! The radiation used to polymerize and crosslink - is preferably β-rays such as electron beams, ultraviolet rays, or r-rays such as xIlil. A sensitizer is used at the same time to increase the sensitivity. It is best to use radiation with an accelerating voltage of 150 to 750 KV for such radiation irradiation so that the absorbed dose is 3 to 15 Mrad; if the absorbed dose is too small, crosslinking of the oligomers may be insufficient. The desired effect cannot be obtained.

Examples of the magnetic powder used in this invention include r-F
ez03 powder, Fe, 04 powder, Co-containing - Fe, O
s powder, Co-containing Fe, O, powder, Cry, powder, etc.
A wide variety of conventionally known magnetic powders are included, such as metal powders such as Fe powder, Co powder, and Fe-Ni powder.In particular, when metal powders are used with a thin oxide layer formed on their surfaces, the titanium coupling agent described above can be easily absorbed. The effect is greater when used together.

In order to form the magnetic layer of the present invention on a substrate, the above-mentioned urethane acrylate) or urethane methacrylate oligo! - or the aforementioned titanium coupling agent dissolved in magnetic powder and solvent in an oligomer mixed with polyalkylene glycol or an oligomer in which acrylic acid or methacrylic acid is ester bonded to the end of polyhydric alcohol. A magnetic paint is prepared by dispersing and mixing the above-mentioned titanium cup 9' or magnetic powder whose surface has been previously treated with the above-mentioned titanium cup 9'/gluing agent. After coating this on a substrate such as a polyester film, radiation is applied Either by irradiation and polymerization and curing, or by dissolving the above oligomer or a mixture of the two oligomers in an organic solvent, and surface-treating the solution with magnetic powder and a titanium coupling agent or a titanium coupling agent in the same manner as above. A magnetic paint is prepared by dispersing and mixing magnetic powder, which is applied onto a substrate such as a polyester film, preheated to remove the organic solvent contained in the magnetic paint, and then irradiated with radiation to polymerize. This is done by curing. In this case, when an organic solvent is used, the viscosity of the magnetic paint becomes lower, so that the filling properties of the magnetic powder are further improved, and the magnetic properties and surface smoothness of the magnetic layer are further improved. As such an organic solvent, any of the solvents conventionally used in preparing magnetic paints, such as methyl isobutyl ketone, cyclohexanone, silene, and dimethylformamide, can be suitably used. Therefore, low boiling point and low toxicity solvents such as ethanol, n-hebutane, and n-hexane can also be suitably used. Therefore, if these low boiling point and low toxicity solvents are used, there will be no pollution problem. This problem is solved, and since these low-boiling point solvents are easily removed by preheating after applying the magnetic paint, recovery of the solvent is also facilitated.

In addition, various commonly used additives such as dispersants, abrasives, antistatic agents, etc. may be appropriately added to the magnetic coating material as necessary.

Next, embodiments of the invention will be described.

Example 1 Using a urethane acrylic oligomer represented by the structural formula, Co-containing r-Fe 20g magnetic powder 60 parts by weight Urethane acrylic oligomer 40 #Plenact 9
8 (manufactured by Kenritzhi 21 Betroker Corporation, isopp pyltridecylbenzenesulfonyl titanium)) A composition consisting of ethyl alcohol/methyl ether 25 1 methyl ketone mixed solvent (mixing ratio 1/1) Mix and disperse in a mill for 72 hours to prepare magnetic paint, and apply this magnetic paint to a thickness of 15 μm.
The film was coated on a polyester base film with a coating thickness of 4 tones. Next, after preheating at 90°C for 1 minute to remove the ethyl alcohol/methyl ethyl ketone mixed solvent, it was cured by irradiating with an electron beam at an irradiation dose of 7 Mrrod using EPS Near 5G manufactured by Nissin High Voltage Co., Ltd. A magnetic tape was made by cutting it into a predetermined width after calendering. Example 2 In the composition of the magnetic paint in Example 1, urethane acrylic oli! ! Magnetic I made a tape.

Example 3 In the composition of the magnetic paint in Example 2, the ethyl alcohol/methyl ethyl ketone mixed solvent was omitted, the amount of urethane acrylic oligomer used was changed from 20 parts by weight to 15 parts by weight, and tetraethylene glycol dimethacrylate was used. The amount was changed from 20 parts by weight to 30 parts by weight,
Furthermore, a magnetic tape was produced in the same manner as in Example 2 except that preheating was omitted.

Comparative Example 1 A magnetic tape was produced in the same manner as in Example 1 except that Preact 9S was omitted from the composition of the magnetic paint in Example 1.

Comparative Example 2 In the composition of the magnetic paint in Example 1, Tetrastearyl Titanium) (Ti(Q
A magnetic tape was produced in the same manner as in Example 1 except that the same amounts of Cl, HB), ) were used.

Regarding the magnetic tapes obtained in each example and comparative example,
To measure the video SN ratio and color SN ratio, and further examine the durability, each magnetic tape was loaded into a tape recorder, and the running speed was set at approximately 3.3 a at 40°C and 80% RH.
m/se (The output fluctuation was measured after running 300 times.The video S/N ratio and color S/N ratio were measured using
The magnetic tape was loaded into the magnetic tape and recorded and reproduced, and measured using a Color Video Noise Meter 925C manufactured by Sibaku Corporation. Ta.

The table below shows the results.

As is clear from the above table, the magnetic tapes obtained by the present invention (Examples 1 to 3) have a higher video SN ratio and color SN ratio than conventional magnetic tapes (Comparative Examples 1 and 2). are high and the output fluctuations are small, and the malt rice obtained in Examples 2 and 3 is particularly good. Therefore, the magnetic recording medium obtained by this invention has excellent dispersibility and filling properties of magnetic powder. It can be seen that the magnetic properties and surface smoothness of the magnetic layer as well as durability are further improved, and those obtained in Examples 2 and 3 have particularly remarkable improvements in these.

Claims (1)

[Claims] L on the substrate, general formula % formula %) (However, in the formula, 鵞 is a hydrocarbon group, and
, -C> or -PO(OH)-0-PO, a catfish hydrocarbon group or →0-11) and R1 is an alkyl group. A coating film containing an oligomer of urethane acrylate (having a urethane bond and a 7-acrylate double bond at one or both ends) or urethane methacrylate and 1 magnetic powder was formed, and the film was cured by irradiating it with radiation. Magnetic recording medium 2 characterized in that a magnetic layer is provided on a substrate (general formula % formula %) (wherein R is a hydrocarbon group, X is -CO or -8O
, -C> or -PO(OH) -0-PO, Y is a hydrocarbon group or 10-R18, and R8 is an atomyl group), and a titanium coupling agent represented by An oligomer of urethane acrylate or urethane methacrylate having a urethane bond at the end or both ends, and an ester of acrylic acid or methacrylic acid at the end of a polyalkylene glycol or polyhydric alcohol. A magnetic recording medium characterized by forming a coating film containing bonded oligomers and magnetic powder, and providing a magnetic layer that is cured by irradiating the coating film with radiation.