JPH0668450A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve traveling durability by incorporating a bromine-contg. phosphate modified phenoxy resin as a binder into a back coating layer. CONSTITUTION:This magnetic recording medium is constituted by forming a magnetic layer I on one surface of a nonmagnetic base 2 and the back coating layer 3 on the other surface. The magnetic recording medium contains the bromine-contg. phosphate modified phenoxy resin having the constituting unit A expressed by formula I and the constituting unit B expressed by formula II as the binder in this back coating layer 3. The traveling durability is improved without degrading the electromagnetic conversion characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium used for audio tapes, video tapes, magnetic disks and the like.

[0002]

2. Description of the Related Art In recent years, particularly in video tapes, the rigidity of the magnetic layer has been increased to improve the durability. However, when a high-rigidity resin is used as a binder for the magnetic layer, the shrinkage of the tape in the tape width direction progresses toward the magnetic layer, causing the phenomenon of curling of the tape. Also, it is necessary to strictly regulate the tape running in the VCR running system, and the curled tape as described above is forcibly pulled while running in the direction opposite to the curl direction, so tape running and wear resistance And the running durability were deteriorated. In order to solve these problems, the backcoat layer provided on the non-magnetic support on the side opposite to the magnetic layer is made to have high rigidity to reduce curling to the magnetic layer side and improve tape running property. As a result of examination, we found that there is an improvement tendency by using a phenoxy resin as a binder for the back coat layer. However, the conventional phenoxy resin has extremely poor dispersibility, and the effect of improving the running property is not sufficient. As a measure for improving the dispersibility of the phenoxy resin, many proposals have been made so far. For example, JP-A-62-38524, JP-A-62-159336, JP-A-62-202319 and JP-A-63-
52321, JP-A-63-52322, JP-A-63-52323, and JP-A-63-52324.
JP-A-63-63126, JP-A-63-63
63127, JP-A-63-63128, JP-A-63-63129, and JP-A-3-63927, in which a hydrophilic group is introduced as a functional group in the structural formula. Have been proposed.

[0003]

However, with only the above-mentioned constitution, the viscosity of the back coat paint is increased, the coatability is lowered, or the compatibility with other binders is poor. As a result, the surface smoothness of the back coat layer is inferior, and after forming the magnetic layer and the back coat layer on the front and back of the non-magnetic support respectively, the magnetic tape, the magnetic disk, etc. which reach the final product through the winding process. In the above magnetic recording medium, since the projection shape on the surface of the back coat layer was transferred to the surface of the magnetic layer, it was difficult to obtain good electromagnetic conversion characteristics at the same time. The present invention provides a magnetic recording medium having excellent electromagnetic conversion characteristics, running properties, and running durability.

[0004]

The present invention relates to a magnetic recording medium having a magnetic layer formed on one surface of a non-magnetic support and a back coat layer on the other surface of the non-magnetic support. ,

[0005]

[Chemical 5]

A structural unit A represented by

[0007]

[Chemical 6]

A magnetic recording medium comprising a bromine-containing phosphate-modified phenoxy resin having a structural unit B represented by:

[0009]

The present invention has the above-mentioned constitution, that is, by containing a bromine-containing phosphate ester-modified phenoxy resin as a binder in the back coat layer, the dispersibility of the back coat paint and the surface smoothness of the back coat layer are improved. It is possible to suppress the curling property in the tape width direction, and as a result, to improve the running durability of the tape without impairing the surface smoothness of the magnetic layer, that is, without lowering the electromagnetic conversion characteristics. Can be provided.

[0010]

The present invention will be specifically described below.

The bromine-containing phosphate ester-modified phenoxy resin used in the present invention comprises the structural unit A represented by (Chemical formula 5) and (Chemical formula 6) or

[0012]

[Chemical 7]

Or

[0014]

[Chemical 8]

It is preferable that the content of bromine and halogen in the phenoxy resin is 20 wt% or more and 30 wt% or less. If the amount of bromine or halogen element is less than 20 wt%, the viscosity of the back coat coating becomes high, and if it is more than 30 wt%, it becomes difficult to dissolve the phenoxy resin in the organic solvent. Further, the structural unit A and the structural unit B
The phosphoric acid ester group contained in the phenoxy resin is 1 g.
0.01 mmol or more and 0.2 mmol or less per unit is desirable. When it is less than 0.01 mmol, dispersibility and coating stability are deteriorated, and when it is more than 0.2 mmol, dissolution in an organic solvent becomes difficult. As the binder used in the back coat layer, in addition to the bromine-containing phosphate ester-modified phenoxy resin, nitrocellulose-based resin, polyurethane-based resin, polyester-based resin, polycarbonate-based resin, etc. may be used alone or in combination of two or more kinds. You can

The amount of the binder is preferably 60 parts or more and 100 parts or less, based on the weight of the pigment used in the back coat being 100, and the addition amount of the bromine-containing phosphate ester-modified phenoxy resin in the binder. Is preferably 10% or more and 80% or less of the weight of the binder.

As the pigment used in the back coat layer, calcium carbonate, furnace black, thermal black, color black, acetylene black, conductive carbon and the like can be used alone or in combination of two or more kinds. As an abrasive, alumina, chromium oxide, silicon oxide,
Red iron oxide and the like can be used as necessary. Similarly, as the lubricant, higher fatty acid, higher fatty acid ester, or various surfactants can be used alone or in combination of two or more kinds.

The magnetic layer for a magnetic recording medium obtained in the present invention comprises a layer comprising a ferromagnetic powder, a binder, an abrasive, and optionally an antistatic agent and a lubricant, which is a non-magnetic support (usually It can be formed on a plastic film by a known method. As the non-magnetic support, polyethylene terephthalate (hereinafter abbreviated as PET), polyethylene naphthalate (hereinafter abbreviated as PEN), aromatic polyamide,
There are aromatic polyimides and the like.

The ferromagnetic powder used in the magnetic layer includes metal magnetic powder, cobalt-coated magnetic iron oxide, barium ferrite magnetic powder and the like. Examples of the abrasive include alumina, chromium oxide, silicon oxide, red iron oxide and the like. Conductive carbon can be used as the antistatic agent. As the lubricant, higher fatty acids, higher fatty acid esters, or various surfactants can be used alone or in combination of two or more kinds.

In kneading and dispersing the coating material for the magnetic layer and the back coat layer, which are the constituent layers of the tape-shaped magnetic recording medium obtained in the present invention, various kneading machines such as roll mill, kneader, attritor, double planetary mixer, high speed Mixer high speed stone mill, agitator mill, sand mill,
A pin mill, a ball mill, a high speed agitator, an ultrasonic disperser or the like can be used alone or in combination of two or more kinds.

The present invention will be described below with reference to examples. (Example 1) Preparation of coating material for magnetic layer Cobalt-coated magnetic iron oxide 100 parts (BET 5 * 10 ⁴ m ² / kg) (σs 1 * 10 ^-4 Wbm / kg) (Hc 6.2 * 10 ⁴ A / M) Alumina 8 parts Carbon black 1 part Vinyl chloride-vinyl acetate copolymer resin 10 parts Polyurethane resin 10 parts Mixed solvent 400 parts Myristic acid 1 while stirring with a disperser to a magnetic paint dispersed with a pressure kneader and a sand mill 1 Parts n-butyl stearate 1 part polyisocyanate 5 parts were added to prepare a magnetic layer coating material. At this time, the mixed solvent used was methyl ethyl ketone / toluene / cyclohexanone in a weight ratio of 3/2/1. This paint 1
After coating on a PET support having a thickness of 1.5 μm and drying, a mirror surface processing by calendering was applied to produce a magnetic layer having a thickness of 3.0 μm.

Preparation of coating for back coat layer Carbon black 100 parts Bromine-containing phosphate-modified phenoxy resin (bromine amount 25 wt%) (chemical formula 5) and chemical formula 7 (chemical formula 7) (phosphoric acid ester amount 0) .1 mmol / g) 40 parts Polyurethane resin 40 parts Methyl ethyl ketone 200 parts Toluene 200 parts Stiric acid 1 part Polyisocyanate 20 parts while stirring with a disperser to the paint prepared by dispersing the above composition in a pressure kneader and a sand mill. And Apply these two paints on the support on the side opposite to the magnetic layer and dry to 0.7μ
An m-thick back coat layer was prepared and cut into a 1/2 inch width to obtain a video tape sample.

(Example 2) A video tape sample was prepared in the same manner as in Example 1 except that the bromine content in the phenoxy resin in Example 1 was changed to 28 wt%.

(Example 3) A videotape sample was prepared in the same manner as in Example 1 except that the bromine content in the phenoxy resin in Example 1 was changed to 22% by weight.

(Example 4) The amount of the phosphoric acid ester in the phenoxy resin in (Example 1) was 0.05 mmol / g.
A video tape sample was prepared in the same manner as in (Example 1) except that the above was used.

(Example 5) The amount of phosphoric acid ester in the phenoxy resin used in (Example 1) was 0.15 mmo.
A video tape sample was prepared in the same manner as in (Example 1) except that the amount was changed to 1 / g.

(Example 6) The content of the phenoxy resin and the content of the polyurethane resin in Example 1 were 32, respectively.
Parts were prepared in the same manner as in (Example 1) except that the parts were 32 parts.

(Example 7) The contents of the phenoxy resin and the polyurethane resin in (Example 1) were set to 48, respectively.
Parts were prepared in the same manner as in (Example 1) except that the parts were 48 parts.

(Embodiment 8) The contents of the phenoxy resin and the polyurethane resin in (Embodiment 1) were each 20
Parts were prepared in the same manner as in (Example 1) except that 60 parts were used.

(Example 9) The contents of the phenoxy resin and the polyurethane resin in (Example 1) were each 60
Parts were prepared in the same manner as in (Example 1) except that the parts were made 20 parts.

(Comparative Example 1) A video tape sample was prepared in the same manner as in (Example 1) except that the phenoxy resin in (Example 1) was changed to a phosphoric acid ester-modified phenoxy resin containing no bromine.

(Comparative Example 2) A video tape sample was prepared in the same manner as in (Example 1) except that the phenoxy resin in (Example 1) was changed to a phosphate ester-modified phenoxy resin having a bromine content of 35 wt%. .

Comparative Example 3 A videotape sample was prepared in the same manner as in (Example 1) except that the phenoxy resin in (Example 1) was changed to nitrocellulose resin.

[0034]

[Table 1]

The following evaluations were performed on each of the obtained samples. (1) Running durability Matsushita Electric Industrial Co., Ltd. S-VHS video deck NV-F
Running durability by visual observation of tape after 100 passes of reproduction / rewinding using S1 (2) C / N [dB] Matsushita Electric Industrial Co., Ltd. S-VHS video deck NV-F
The ratio (C / N) of the signal of 7 MHz and the noise of 5 MHz was measured using S1, and S-VHS manufactured by Matsushita Electric Industrial Co., Ltd.
C / N comparing video tape XD120 as 0 dB (3) Tape curl (Fig. 1) As shown in (Fig. 1), a tape slit in a 1/2 inch width was left still so that it was convex on a horizontal plane, and Measure the height. If the back coat layer side is a convex surface, the symbol "+" is added to the height, and if the magnetic layer side is a convex surface, the symbol "-" is added.

[0036]

[Table 2]

[0037]

As described in detail above, according to the present invention, the electromagnetic conversion characteristics are deteriorated by including the bromine-containing phosphate ester-modified phenoxy resin in the back coat layer as a binder. Without, it is possible to improve the running durability. In this example, only the result of the phenoxy resin modified with bromine-containing phosphate was shown, but the same result was obtained even when other halogen elements were used.

[Brief description of drawings]

FIG. 1 is a sectional view of a tape according to the present invention.

[Explanation of symbols]

 1 magnetic layer 2 non-magnetic support 3 back coat layer 4 height h

Claims (3)

[Claims] 1. A magnetic recording medium in which a magnetic layer is formed on one surface of a non-magnetic support and a back coat layer is formed on the other surface, wherein the back coat layer comprises: A structural unit A represented by A magnetic recording medium comprising a bromine-containing phosphate-modified phenoxy resin having a structural unit B represented by as a binder. 2. A magnetic recording medium in which a magnetic layer is formed on one surface of a non-magnetic support and a back coat layer is formed on the other surface of the non-magnetic support. The structural unit A shown, and The magnetic recording medium according to claim 1, further comprising, as a binder, a bromine-containing phosphate-modified phenoxy resin having a structural unit B represented by 3. A magnetic recording medium in which a magnetic layer is formed on one surface of a non-magnetic support and a back coat layer is formed on the other surface of the non-magnetic support. The structural unit A shown, and And a halogen element-containing phosphoric acid ester-modified phenoxy resin having a structural unit B represented by