JPH0820656A - Easy-adhesive polyester film for magnetic recording media - Google Patents

Abstract

(57) [Summary] [Purpose] Adhesiveness, processability, flatness, blocking resistance
Excellent adhesion polyester film for magnetic recording media
I will provide a. 【Structure】 The thickness is 2 ~ 8μm and at least one direction
Rate is 650 kg / mm ²More than oriented polyester
(A) 50% modulus on at least one side of the film
10 to 300 kg / mm², Breaking elongation of 200-900
% Block copolyester and (B) average particle size
Including fine particles of 5 to 1000 nm, and surface roughness Ra
Recording medium provided with a coating layer having a thickness of 2 to 10 nm
Easy-adhesive polyester film for use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easily adhesive polyester film for a magnetic recording medium, and more specifically, it has excellent surface flatness and adhesiveness to a magnetic layer and can form a flat magnetic layer surface. The present invention relates to an easily-adhesive polyester film for magnetic recording media, which is useful as a base film for tapes, magnetic disks and the like.

[0002]

2. Description of the Related Art As a base film for a magnetic recording medium,
Biaxially oriented polyester film, especially biaxially oriented polyethylene terephthalate film is used. But,
In recent years, the quality of magnetic recording media has been improved and the recording time has been extended, and along with this, the required characteristics of the base film have become more sophisticated. For example, there is a demand for a base film capable of coping with thinning of the magnetic layer and super flattening of the surface of the magnetic layer.

The biaxially oriented polyester film includes
Usually, an easily-adhesive primer layer (coating layer) is provided on the surface of the magnetic layer, but few conventional primers can sufficiently meet the required characteristics. In particular, it has been difficult to balance flatness, blocking resistance, workability, adhesiveness and the like. For example, JP-A-58-193149 describes that a coating layer containing a random copolymerized polyester and colloidal silica is provided on a two-layer film. It is hard to say that the flatness of the magnetic layer surface is sufficient.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide an easily adhesive polyester film for magnetic recording media, which is excellent in adhesiveness, workability, flatness and blocking resistance.

[0005]

The present invention has the following constitution in order to achieve the above object.

At least one side of the oriented polyester film having a thickness of 2 to 8 μm and a Young's modulus in at least one direction of 650 kg / mm ² or more, (A) 50% modulus of 10 to 300 kg / mm ² , fracture. Elongation is 200-90
An easy-to-use magnetic recording medium provided with a coating layer containing 0% of a block copolymerized polyester and (B) fine particles having an average particle size (d: nm) of 5 to 1000 nm and having a surface roughness Ra of 2 to 10 nm. Adhesive polyester film.

In the present invention, the polyester constituting the oriented polyester film is a linear saturated polyester synthesized from an aromatic dibasic acid or its ester-forming derivative and a diol or its ester-forming derivative. Specific examples of such polyesters include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylene dimethylene terephthalate), polyethylene-2.
Examples thereof include 6-naphthalene dicarboxylate, and copolymers of these or blends of these with small proportions of other resins are also included.

The linear polyester film of the present invention can be obtained by melt-extruding the linear saturated polyester resin, forming it into a film by a conventional method, and crystallizing it by orientation crystallization and heat treatment. The oriented polyester film is oriented such that the value measured by a differential scanning calorimeter in a nitrogen stream [at a temperature rising rate of 10 ° C./min] as a heat of fusion of crystals is usually 4 cal / g or more. preferable.

The oriented polyester film has a thickness of 2 to 8
μm, preferably 3 to 7 μm, and Young's modulus in at least one direction is 650 kg / mm ² or more, preferably 6
It should be 80 kg / mm ² or more. This thickness is 2
If it is less than μm, the strength becomes insufficient, while if it exceeds 8 μm, it causes an increase in weight in lengthening the tape, which is not preferable.
On the other hand, if the Young's modulus is less than 650 kg / mm ² , the base film is too thin to provide sufficient strength, which is not preferable.

The oriented polyester film can be produced by a conventionally known method or a method accumulated in the art. For example, molten polyethylene terephthalate is melted, extruded from a die onto a rotary cooling drum and rapidly cooled to obtain an unstretched film, and then the unstretched film is stretched in one direction (longitudinal direction or transverse direction), followed by this stretching method. Can be manufactured by stretching in a direction (transverse direction or longitudinal direction) at right angles to and heat setting. At that time, the stretching temperature is preferably not less than the second-order transition point (Tg) of polyester, and the stretching ratio is preferably not less than 8 times in terms of area ratio. However, the stretching ratio in at least one direction is such that the Young's modulus is 650 kg / mm ² or more. As a stretching method, a simultaneous biaxial stretching method, a sequential biaxial stretching method, a multi-stage stretching method,
A re-stretching method or the like can be used.

In the present invention, the easily adhesive coating layer is (A)
A coating layer containing a block copolymerized polyester having a 50% modulus of 10 to 300 kg / mm ² , a breaking elongation of 200 to 900%, and (B) fine particles having an average particle size of 5 to 1000 nm.

A typical polymer of the block copolymerized polyester (A) is a polyether ester block copolymer in which the soft segment is a polyalkylene ether glycol, and the soft segment has a low second-order transition point.
Alternatively, a polyester ester block copolymer made of an amorphous or hardly crystalline polyester, particularly an aliphatic polyester, may be mentioned, and of these, a polyether ester block copolymer is preferable.

The crystalline polyester or aromatic polyester having a high second-order transition point constituting the hard segment of the polyether ester block copolymer has an acid component of terephthalic acid,
Aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid and 4,4′-diphenyldicarboxylic acid as main components,
The glycol component is a polyester containing a short chain glycol such as ethylene glycol, propylene glycol, tetramethylene glycol, hexamethylene glycol, 1,4-cyclohexanedimethanol as a main component. As the copolymerizable component that can be used in a small proportion (30 mol% or less, preferably 20 mol% or less), isophthalic acid, phthalic acid,
Examples thereof include 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, neopentyl glycol, diethylene glycol, dipropyl glycol and xylylene glycol. Among these, those containing tetramethylene-2,6-naphthalene dicarboxylate or tetramethylene terephthalate as the main repeating component are preferable.

Preferred examples of the polyalkylene ether glycol constituting the soft segment of the polyether ester block copolymer include polyethylene glycol and polytetramethylene glycol. Of these, polytetramethylene glycol is preferred. The molecular weight of polyalkylene ether glycol is 30
It is preferably 0 to 3000, and more preferably 600 to 2000.

The polyether ester block copolymer can be produced by a known method, for example, by reacting a polyalkylene ether glycol with a raw material for producing an aromatic polyester.
In that case, a small proportion of a trifunctional or higher functional compound such as trimellitic acid, pyromellitic acid, glycerin, trimethylolpropane, etc. can be copolymerized in addition to the copolymerization component. Copolymerization of this compound can further improve the elastic properties. Further, a component that imparts hydrophilicity to the polyether ester block copolymer can be copolymerized.

The hard segment of the polyester ester block copolymer may be the same as the hard segment of the polyether ester block copolymer. Therefore, the hard segment of the polyester ester block copolymer is preferably one containing ethylene terephthalate, tetramethylene terephthalate or tetramethylene-2,6-naphthalene dicarboxylate as the main repeating component.

The aliphatic polyester constituting the soft segment of the polyester ester block copolymer has an acid component of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dimethylolpropionic acid, etc. Is a polyester whose main component is an aliphatic dicarboxylic acid and whose glycol component is an aliphatic glycol as a main component such as ethylene glycol, propylene glycol, tetramethylene glycol, and hexamethylene glycol. As the copolymerizable component which can be used in a small proportion (30 mol% or less, preferably 20 mol% or less), terephthalic acid, isophthalic acid, phthalic acid, 1,4-cyclohexanedicarboxylic acid, etc., diethylene glycol, dipropylene glycol, Xylylene glycol, ethylene oxide adduct of bisphenol A, 2,2-bis (β-
Examples thereof include hydroxyethoxyphenyl) propane and the like. Further, as the soft segment, an amorphous aromatic polyester, for example, a polyester containing isophthalic acid as a main acid component and α, ω-diol having 2 to 4 carbon atoms as a glycol component can be used. The amorphous or non-crystalline polyester having a low second-order transition point constituting the soft segment has a molecular weight of preferably 300 to 3,000, more preferably 600 to 2,000.

Such polyester ester block copolymer can be produced by a known method. For example, a polyester having a high second-order transition point or crystalline and a polyester having a low second-order transition point or an amorphous polyester are melted. It can be manufactured by reacting with to form a block copolymer.
At this time, if this reaction proceeds too much, it becomes a copolyester of random bond, and the properties of low elastic modulus disappear, so caution is required. Further, as in the case of the polyether ester block copolymer, a trifunctional or higher functional compound or a hydrophilicity-imparting compound can be copolymerized.

As the compound which imparts hydrophilicity to the block copolymerized polyester, a compound capable of introducing a sulfonate group, a carboxylate group or the like into the side chain of the polymer molecule, for example, 5-
Na sulfoisophthalic acid, 5-ammonium sulfoisophthalic acid, 4-Na sulfoisophthalic acid, 4-methylammonium sulfoisophthalic acid, 2-Na sulfoterephthalic acid, 5-K sulfoisophthalic acid, 4-K sulfoisophthalic acid, 2- K sulfoterephthalic acid, Na sulfosuccinic acid, mono-Na (or K) salt of trimellitic acid, monomethylammonium salt of trimesic acid, Na (or K) salt of pyromellitic acid, methylammonium salt of pyromellitic acid, etc. Examples thereof include compounds that can introduce an ether bond into the polymer molecule main chain, such as diethylene glycol, dipropylene glycol, and polyethylene glycol. Such a compound is preferably used in a proportion of 0.5 to 20 mol%, more preferably 1 to 18 mol%, based on all acid components or all glycol components.

The block copolymerized polyester (A) in the present invention has a 50% modulus of 10 to 300 kg / cm.
² , preferably 15 to 200 kg / cm ² , and a breaking elongation of 200 to 900%, preferably 220 to 750%. This 50% modulus is 10kg
If it is less than / cm ² , the blocking resistance tends to be low, while 30
If it exceeds 0 kg / cm ² , the flatness of the magnetic layer surface due to calendering is deteriorated, which is not preferable. If the breaking elongation is less than 200%, the flatness of the magnetic layer surface is poor, while 90
If it exceeds 0%, the blocking resistance decreases, which is not preferable.

The fine particles (B) in the present invention are fine particles having an average particle diameter of 5 to 1000 nm, preferably 6 to 500 nm. Examples of the fine particles include calcium carbonate,
Calcium oxide, aluminum oxide, kaolin, silicon oxide, zinc oxide, carbon black, silicon carbide, tin oxide,
Examples thereof include crosslinked acrylic resin particles and crosslinked polystyrene resin particles. If the average particle size of the fine particles is less than 5 nm, the blocking resistance is lowered, while if it exceeds 1000 nm, the surface of the coating layer or the magnetic layer surface is roughened, which is not preferable.

The average particle diameter (d: nm) of the fine particles is preferably 3 times or less the thickness (t: nm) of the coating layer. If the average particle size is more than 3 times the thickness, fine particles are likely to be scraped.

In the present invention, the coating layer (easy-adhesion primer layer) is formed by coating a coating solution containing the block copolymerized polyester (A) and the fine particles (B) on at least one side of the polyester film. The liquid is preferably an aqueous liquid. In particular, it is difficult to use an organic solvent system when applying in the film manufacturing process. In the coating liquid, if necessary, a surfactant, an antistatic agent, a dispersant, an antioxidant,
An antiblocking agent, a slip agent, an antifoaming agent, a softening agent, a crosslinking agent, a curing agent, a catalyst and the like can be added.

The coating solution may be applied to either an unstretched polyester film, a uniaxially stretched (orientation) film or a biaxially stretched (orientation) film, but especially to a uniaxially stretched (orientation) film stretched in the machine direction. It is preferable to stretch the film in the transverse direction after coating. After that, it can be further re-stretched in the machine direction or the transverse direction. When coating a biaxially stretched (orientated) film outside the film manufacturing process, an organic solvent-based coating liquid can also be used.

The coating can be carried out using a coater such as a roll coater, a die coater and a gravure coater.

The coating layer has a surface roughness Ra of 2 to 10 n.
m, preferably 3-9 nm. When the surface roughness Ra is less than 2 nm, the slipperiness is insufficient, while the surface roughness Ra is 10 nm.
If it exceeds, it is not preferable because it is too rough and the magnetic properties are deteriorated. Further, the surface roughness Ra is preferably smaller than the average particle diameter of the fine particles (B).

The easily-adhesive polyester film of the present invention has a strong adhesive force by the action of the block copolymerized polyester (A) when a magnetic layer is provided on the coating layer, and the surface of the magnetic layer is flattened by calendering. It is useful as a base film of a magnetic recording medium because it has a characteristic that the effect is remarkable, and further that the action of the fine particles (B) maintains the winding property and blocking resistance of the film.

[0028]

EXAMPLES The present invention will be further described below with reference to examples. The film characteristics in the examples were measured by the following methods.

1. Young's modulus of 1/2 "width sample film
The tensile load curve is measured at a speed of 0 mm / min. Young's modulus is obtained from the tangent gradient of this curve when the elongation is 0%.

2. 50% modulus, breaking elongation A dumbbell having a thickness of 0.5 mm is formed, and the dumbbell is pulled by a tensile tester at a speed of 50 mm / min, and the load when the elongation is 50% is 50% modulus (kg / cm ² ), And the elongation at break is defined as the elongation at break (%).

3. Surface roughness (Ra) In accordance with JIS B0601, using a high precision surface roughness meter SE-3FAT manufactured by Kosaka Laboratory Ltd., the radius of the needle is 2μ.
m, load 30 mg, magnification 200,000 times, cutoff 0.
A chart is placed under the condition of 08 mm, and a portion of the measurement length L is extracted from the surface roughness curve in the direction of its center line, and the center line of this extracted portion is taken as the X axis and the longitudinal magnification direction is taken as the Y axis. When the height curve is expressed by Y = f (x), the value given by the following equation is expressed in μm.

[0032]

[Equation 1]

In this measurement, the reference length is 1.25 mm and 4
Each is measured and the average value is shown.

4. Adhesiveness (Primer coating) A polyester film is coated with the following coating composition for evaluation so as to have a thickness after drying of about 0.8 μm with a Meyer bar, and dried at 100 ° C. for 3 minutes. After calendering, it was aged at 60 ° C for 24 hours, and then Scotch tape No. 600 (manufactured by 3M Co.) with a width of 12.7 mm and a length of 15 cm was adhered to it so that no air bubbles could enter it.
It is leveled with a manual load roll described in IS C2701 (1975), brought into close contact with it, and cut into a tape width. 18 this
The strength when peeled at 0 degrees is measured. [Evaluation paint] Urethane resin Nipporan 2304 25 parts by weight (manufactured by Nippon Polyurethane) PVC / vinyl acetate resin S-REC A 50 parts by weight (Sekisui Chemical Co., Ltd.) Dispersant Resion P 1 part by weight (manufactured by RIKEN VITAMINS) Magnetic Agent CTX-860 500 parts by weight (manufactured by Toda Chemical Co., Ltd.) is dissolved in a mixed solvent of methyl ethyl ketone / toluene / cyclohexanone to make a 40% solution, which is then subjected to 2 with a sand glider
Spread over time. After that, 25 parts by weight of Coronate L (in terms of solid content) as a cross-linking agent is added and well stirred to obtain a magnetic coating material.

5. Blocking property 10 after putting the front and back of the polyester film together
Cut into squares of 15 cm × 15 cm, and apply a load of 50 kg / cm ² for 17 hours in an atmosphere of 50 ° C. × 50% RH,
Then, the peel strength of this 10 cm width is measured. The peeling speed at this time is 100 mm / min.

[Example 1] Polyethylene 2,6-naphthalene dicarboxylate containing silicon oxide fine particles (lubricant) having an intrinsic viscosity of 0.66 was melted, cast from a die onto a cooling drum and rapidly cooled, It was stretched 4 times in the direction.
On one surface of the obtained uniaxially stretched film, terephthalic acid-isophthalic acid-5-Na sulfoisophthalic acid-1,4-butanediol-polyethylene glycol-polytetramethylene glycol block copolymer (A-1, 50% modulus 80 kg / Cm ² , breaking elongation 380%) 65w
t%, crosslinked acrylic resin fine particles with an average particle size of 48 nm (B
-1) A 4% aqueous liquid consisting of 20 wt%, 10 wt% of ethylene oxide / propylene oxide block copolymer and 5 wt% of polyoxyethylene nonylphenyl ether was applied by a gravure coater, dried, and then 5.2 times in the lateral direction. After stretching, heat setting treatment was performed at 232 ° C. The obtained biaxially oriented film had a thickness of 6.9 μm, the primer layer had a thickness of 50 nm, and the surface roughness (Ra) was 7 nm.
Met. The Young's modulus in the lateral direction of this film is 750k
g / mm ² . The characteristics of this film are shown in Table 1.

[Comparative Example 1] The same procedure as in Example 1 was carried out except that the coating treatment was not carried out. The properties of the obtained biaxially oriented polyester film are shown in Table 1.

[Examples 2-8, Comparative Examples 2-3] Example 1
In the same manner, except that the coating agent and the coating amount were changed as shown in Table 1. Table 1 shows the results.

[0039]

[Table 1]

Note) The symbols in the table are as follows. A-2: 2,6-naphthalenedicarboxylic acid-isophthalic acid-5-K sulfoisophthalic acid-diethylene glycol-1,4-butanediol-polytetramethylene glycol block copolymer (50% modulus 60 kg / c
m ² , breaking elongation 410%). A-3: terephthalic acid-isophthalic acid-5-Na sulfoisophthalic acid-ethylene glycol-neopentyl glycol random copolymer polyester (50% modulus 385 kg / cm ² , break elongation 16%). A-4: Terephthalic acid-5-Na Sulfoisophthalic acid-
1,4-butanediol-diethylene glycol-polytetramethylene glycol block copolymer (50% modulus 68 kg / cm ² , breaking elongation 392%). B-2: Silica fine particles having an average particle diameter of 12 nm. B-3: Crosslinked polystyrene fine particles having an average particle size of 50 nm. B-4: Crosslinked polystyrene fine particles having an average particle diameter of 150 nm.

[0041]

According to the present invention, it is possible to provide an easily-adhesive polyester film which is excellent in adhesiveness, workability, flatness and blocking resistance and which is useful as a base film of a magnetic recording medium.

Claims (5)

[Claims] 1. A thick is 2 to 8 m, at least the at least one surface of the oriented polyester film in one direction of the Young's modulus is 650 kg / mm ² or more, (A) 50% modulus of 10~300kg / mm ² , Breaking elongation of 200-9
An easy-to-use magnetic recording medium provided with a coating layer containing 00% of block copolymerized polyester and (B) fine particles having an average particle diameter (d: nm) of 5 to 1000 nm and having a surface roughness Ra of 2 to 10 nm. Adhesive polyester film. 2. The relationship between the thickness (t: nm) of the coating layer and the average particle diameter (d: nm) of the fine particles is 3t ≧ d.
The easily-adhesive polyester film described. 3. The easily adhesive polyester film according to claim 1, wherein the block copolymerized polyester is a polyether ester block copolymer. 4. The easily adhesive polyester film according to claim 3, wherein the soft segment component of the polyether ester block copolymer is polytetramethylene glycol. 5. The easily adhesive polyester film according to claim 1, wherein the oriented polyester film is made of a material of polyethylene terephthalate or polyethylene-2,6-naphthalene dicarboxylate.