JPH10278209A - White film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inexpensively obtain a white film satisfying required characteristics in a well-balanced state. SOLUTION: This film has a laminated structure of two or more layers and is composed of a polyester type resin containing titanium oxide particles. In this case, the content of titanium oxide particles of the respective layers is 6-35 wt.% (1) and the particle distributions of titanium oxide particles contained in the respective layers are different (2) and a coating layer of water- soluble or water-dispersible paint is provided to at least the single surface of the film (3) and the surface roughness Ra of at least the single layer having the coating layer is 0.005-0.3 μm (4) and whiteness is 85% or more (5) and optical density (in terms of 188 μm-thickness) is 0.9 or more (6).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white film made of a polyester resin, and more particularly to a white film having excellent workability as a base material for magnetic recording cards and various printed materials.

[0002]

2. Description of the Related Art Conventionally, as a white polyester film, (A) a copolymer component of a polymer of 2 to 50 mol% and an inorganic filler of 1 to 20% by weight are added (for example, Japanese Patent Application Laid-Open No. No. 13542), (B) a film obtained by suppressing the heat of crystal fusion of a film to 6 cal / g or less and adding 5 to 30% by weight of white inorganic particles (for example,
241492), (C) average particle size of 0.1 to 25 μm
m × 10 ⁸ particles / mm ³ , melting point 210
To 245 ° C. (for example, see JP-A-5-17094).
No. 2), and the like.

[0003] However, when such a white polyester film is used for a relatively thick magnetic recording medium such as a magnetic recording card, for example, not only film forming properties but also
In addition to being required to satisfy various characteristics in a well-balanced manner, such as desired whiteness and optical density, desired characteristics of each surface on which a magnetic layer and a print layer are provided, a white film satisfying these various characteristics can be manufactured at a low cost. However, conventional white polyester films have not been sufficient to meet these requirements.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a white film which satisfies the above various required characteristics in a well-balanced manner and can be manufactured at low cost.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, a white film of the present invention has a laminated structure of two or more layers and is made of a polyester resin containing titanium oxide particles, The content of titanium oxide particles contained in each layer is 6% by weight
Not less than 35% by weight, the particle size distribution of the titanium oxide particles contained in each layer is different, and at least one surface has a coating layer of a water-soluble or water-dispersible paint, and at least one surface having a coating layer Roughness R
a is 0.005 μm or more and 0.3 μm or less, whiteness is 85% or more, and optical density (188 μm thickness conversion) is 0.9 or more.

The magnetic recording medium according to the present invention comprises such a white film provided with a magnetic layer on one side and a printed layer on the other side.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The white film of the present invention is a film having a laminated structure of two or more layers, and is a film made of a polyester resin containing titanium oxide particles in each layer.

The number of layers in the laminated structure may be two or three or more. In the case of two layers, one is a thicker core layer and the other is a thinner core layer. Preferably, it is a surface layer. In the case of three layers, it is preferable that the center layer be a thicker core layer and both surface layers be thinner layers.

Factors that affect the suitability of the white film for processing such as coating and printing of the magnetic layer include surface roughness and the presence or absence of coarse projections. Most of these are determined by the particles present in the very surface layer of the film, and the particles present in the inner layer of the film exclusively contribute to optical properties such as opacity and whiteness.

[0010] The white film of the present invention has a laminated structure of two or more layers, so that the layer requiring control of the surface roughness and the coarse protrusion as described above is oxidized by controlling the average particle size and the particle size distribution. Titanium particles are used, and for other layers, relatively inexpensive titanium oxide having a large particle size and a wide particle size distribution is used, so that desired optical characteristics can be easily achieved.

The polyester resin constituting the white film of the present invention contains, as an acid component, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid and naphthalenedicarboxylic acid, adipic acid, azelaic acid, sebacic acid and decane. Aliphatic dicarboxylic acids such as dicarboxylic acids, alicyclic dicarboxylic acids such as cyclohexanecarboxylic acids, and tricarboxylic acids such as trimellitic acid can be used. As alcohol components, ethylene glycol, diethylene glycol, polyethylene glycol, 1,4 −
Butanediol, neopentyl glycol, cyclohexane dimethanol, polytetramethylene glycol and the like can be used.

The polyester resin in the present invention includes:
Other monomers and prepolymers may be copolymerized within the range of 10 mol%. Further, if it is within 40% by weight, it may be blended with various polymers.

As the transesterification catalyst for the polyester resin as described above, Ca, Li, Mn, Zn, Ti and the like can be used. Alternatively, terephthalic acid may be directly transesterified. As the polymerization catalyst, S
b ₂ O ₃ , germanium oxide, or the like can be used.

A white film is obtained by adding titanium oxide particles to each layer made of such a polyester resin.

[0015] The content of titanium oxide particles in each layer is from 6% by weight to 35% by weight. If it is less than 6% by weight, it is difficult to obtain a desired whiteness, and if it exceeds 35% by weight, the content of particles becomes too large, and film breakage occurs frequently in the film forming process.

Basically, by adjusting the content of the titanium oxide particles, the whiteness and the optical density of the film as a whole can be controlled. In the film of the present invention,
By setting the whiteness to 85 or more and the optical density (188 μm thickness conversion) to 0.9 or more, a desired hiding property of the film is ensured.

The average particle size of the titanium oxide particles contained in each layer is not particularly limited, but in order to achieve a predetermined whiteness while ensuring film forming properties, the average particle size is in the range of 0.1 to 1.2 μm. Is preferred.

The particle size distribution is not particularly limited, but the surface roughness Ra (center line average roughness) is 0.005 μm.
It is necessary to sharpen the particle size distribution of the titanium oxide contained in the layer forming the surface controlled to at least 0.3 μm. Specifically, the filter filtration pressure rise (20 μm cut) at a liquid flow rate of 1.11 kg / cm ² was 70 kg / c.
It is preferable that the distribution be sharp such that it is less than m ² , preferably less than 50 kg / cm ² , more preferably less than 20 kg / cm ² .

In the film of the present invention, at least one surface has a surface roughness Ra of not less than 0.005 μm and not more than 0.3 μm. In particular, this range of the surface roughness is optimal for the surface on the magnetic layer application side. By setting the thickness to 0.005 μm or more, a moderately low coefficient of friction is obtained, and by setting the thickness to 0.3 μm or less, coating omission of the magnetic layer and the like are suppressed. However, this surface roughness is also suitable as the surface on the printing layer application side.

The type of the titanium oxide particles contained is not particularly limited, and may be an anatase type, a rutile type, a vulcarite type, or the like. As a production method, there is a sulfuric acid method for the anatase type. The rutile type includes a sulfuric acid method and a hydrochloric acid method, but the sulfuric acid method is more preferable. In the production of particles, for example, drying at 105 ° C. for an appropriate time,
% Is preferable.

It is preferable that the titanium oxide particles have been subjected to a surface treatment. The surface treatment includes an inorganic treatment and an organic treatment.

Examples of the inorganic treatment include an alumina treatment, a silica treatment, a titania treatment, a zirconia treatment, a tin oxide treatment, an antimony oxide treatment, and a zinc oxide treatment. Among them, the alumina treatment is preferable. As the organic treatment, a treatment with a polyol such as pentaerythritol or trimethylolpropane, an amine such as triethanolamine or trimethylolamine, a silicone resin or a silicone such as alkylchlorosilane can be used.

The film of the present invention can be an unstretched film or a uniaxially stretched film, but is preferably a biaxially stretched film in view of strength, durability and the like when used for a magnetic recording medium. More preferably, it is a simultaneous biaxially stretched film. Simultaneous biaxial stretching eliminates the difference in thermal history between the front and back sides, unlike the longitudinal stretching process of the sequential two-stage stretching, and facilitates control of thermal shrinkage, so that twist curl and width shrinkage can be suppressed. Further, the amount of polymer terminal COOH groups on the surface of the substrate having the coating layer is 70 or more and 1
It is preferably 20 or less. The presence of a large number of polymer terminal COOH groups increases the affinity with the coating resin, and enhances the adhesion between the film and the coating layer. However, when the amount of polymer terminal COOH groups exceeds 120, film formation becomes somewhat unstable.

The kind of resin to be applied is not particularly limited.
Polyester resins, acrylic resins, urethane resins, styrene resins, alkyd resins, resins obtained by grafting various monomers and oligomers to resins such as polyester and acrylic, or mixtures of these resins can be used. As the acrylic resin, an acrylic resin containing methyl methacrylate as a main component and an acrylate such as ethyl acrylate or butyl acrylate, or styrene, vinyl toluene, vinyl acetate, acrylonitrile, or the like is preferable. As polyester resin,
As the acid component, terephthalic acid, isophthalic acid, phthalic acid, aromatic dicarboxylic acids such as naphthalenedicarboxylic acid,
Aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decane dicarboxylic acid; alicyclic dicarboxylic acids such as cyclohexane carboxylic acid; and tricarboxylic acids such as trimellitic acid, and ethylene alcohol and diethylene glycol as alcohol components. And polyesters using polyethylene glycol, 1,4-butanediol, neopentyl glycol, cyclohexane dimethanol, polytetramethylene glycol, and the like. As the urethane resin, an aromatic polyisocyanate such as tolylene diisocyanate or diphenylmethane diisocyanate, or an aliphatic polyisocyanate such as hexamethylene diisocyanate or isophorone diisocyanate is used as a polyisocyanate component, and a polyoxypropylene polyol or a polyether polyol is used as a polyol component. Polyether polyols such as polyadipate polyols and polyester polyols such as polycaprolactone diol, and urethanes using hydrocarbons such as polybutadiene polyols and polyacrylate polyols are preferred.

Preferably, the main component of the polymer is an acrylic resin, and the glass transition temperature (Tg) is-
An acrylic resin satisfying 10 ° C. ≦ Tg ≦ 45 ° C. is particularly preferred.

By applying such a resin, good adhesion to the magnetic layer and the printed layer can be obtained. These resins may be cross-linked and cured with various melamines, isocyanates and the like.

Further, the white film according to the present invention can be made into a film having antistatic properties by including an antistatic agent in the coating layer. In the antistatic film, the type of antistatic agent contained is not particularly limited, but various surfactants and amino-based, boron-based, styrenesulfonic acid-based, or sulfonic acid group-containing resin, phosphate group-containing resin, and the like, Alternatively, a substance which forms a charge transfer complex with a metal compound is preferable. The amount to be added is not particularly limited, but is 3% of the total paint solids.
It is preferably from 50 to 50 parts by weight. When the amount is less than 3 parts by weight, a sufficient antistatic effect cannot be obtained, and when the amount is more than 50 parts by weight, the adhesiveness is adversely affected.

By adding such an antistatic agent, in the coating of a magnetic layer, printing, and other processing steps,
The effect of static electricity can be prevented.

If necessary, inorganic particles such as silicon oxide, calcium carbonate, alumina, zirconia, titanium oxide, etc. may be contained in the white film and the coating layer.
Styrene, acrylic, polyethylene, imide,
Modified olefin-based, polypropylene-based crosslinked or non-crosslinked organic particles, composite particles of organic and inorganic substances, aggregated,
It may be added in the form of a true sphere, a bead, a complex shape or the like.

Further, if necessary, various antioxidants, organic or inorganic colorants, brighteners, ultraviolet absorbers and heat stabilizers may be added to the white film and the coating layer if necessary. You may add in the range which does not impair the objective and effect of this invention.

The coating treatment may be performed on a biaxially stretched film, or may be performed after the treatment.
The treatment may be water-based or solvent-based, but in terms of cost, after application and drying on a water-based uniaxially stretched film,
Stretching and heat treatment are effective.

[Measurement Method] (1) Whiteness Measured according to JIS-L1015 (unit:%).

(2) Optical density The optical density was measured according to JIS-K7605. However, the value was converted to a film thickness of 188 μm.

(3) Surface Roughness The center line average roughness Ra (unit: μm) was measured based on JIS-B0601.

(4) Workability The magnetic layer is formed by applying a urethane resin kneaded with a magnetic material to a final thickness of 1.5 μm using a reverse coater and drying. The case where the number of coating omissions of 1 mm or more was 1 or more per 10 m ² was rated “x”, and the case of less than 1 mm was rated “「 ”.

(5) Adhesiveness The print layer is coated with FDOG black and cured by UV irradiation (ultraviolet irradiation). This coating layer was evaluated by 90 ° rapid peeling using cellophane tape. Evaluation criteria ◎: No peeling ：: Residual rate is 90% or more △: Residual rate is 60% or more and less than 90% ×: Residual rate is less than 60%

(6) Average Particle Size Titanium oxide powder was 6.12 × 10 ⁻⁴ m using an electron microscope.
Photographs were taken at an area of m ² 20,000 times and the particle size distribution was measured by a TV image processor to calculate the average particle size.

(7) Increase in Filter Filtration Pressure 3.5 kg of a master chip (titanium oxide concentration: 50%) was extruded with a screw type extruder under the following conditions, and the pressure was measured. The time when the colored resin began to come out was defined as the initial pressure, and the time when the chips disappeared from the raw material supply hopper and the screw was seen was defined as the final pressure. The difference between the final pressure and the initial pressure was defined as an increase in filtration pressure. Extrusion conditions Extruder caliber: 25 mm Filtration area: 3.14 cm ² Screw rotation speed: 40 rpm Filter: sintering 20 μm cut Extrusion temperature: 300 ° C.

(8) Curling property A film sample (150 mm × 100 mm) was hung with a clip, heat-treated at 80 ° C. × 10 minutes, placed on a flat surface, and the lifting height from a square surface was measured. 4
The average of the corner heights was evaluated as the curl height of the sample. Evaluation Criteria ：: The curl height is less than 0.5 mm △: The curl height is 0.5 or more and less than 2.0 mm ×: The curl height is 2.0 mm or more

[0040]

【Example】

Examples 1 to 6 and Comparative Examples 1 to 5 Table 1 shows films having a laminated structure shown in Table 1 (Comparative Examples 1 and 2 are single films, other Comparative Examples and Examples are three layers of A / B / A). Titanium oxide particles having the average particle size and the increased filtration pressure shown in Table 1 were added in the amounts shown in Table 1, supplied to an extruder, melt-extruded at 280 ° C, discharged into a sheet from a die, and cast at 40 ° C. Unstretched sheets of Examples and Comparative Examples except for Example 6 are:
After longitudinal stretching at a stretching temperature of 92 ° C. and a stretching ratio of 3 times, the film was transversely stretched at a stretching temperature of 140 ° C. and a stretching ratio of 3.3 times with a tenter and heat-treated to produce a biaxially stretched white polyester film having a thickness of 188 μm. Filmed. In addition, films other than Comparative Examples 3, 4, and 5 were coated with the following various paints after longitudinal stretching, then applied on both sides, dried, laterally stretched, and heat-treated. Example 6
Applies both coatings shown below to the unstretched sheet,
After drying, it was subjected to simultaneous biaxial stretching (longitudinal stretching ratio of 3 times, transverse stretching ratio of 3.3 times) and heat treatment to form a 188 μm thick biaxially stretched white polyester film.

Paint A: Acrylic emulsion / Antistatic agent (AS) / Melamine = 60/40/10 (Tg = 25 ° C.) (polyphosphate group-containing system) Paint B: Acrylic emulsion (Tg = 25 ° C.) Paint C: Acrylic emulsion (Tg = 65 ° C) Paint D: Polyester emulsion

Paint A was applied in Examples 1 and 6 and Comparative Example 2. Paint B was applied in Example 2. Paint C was used in Example 3,
It was applied in Example 5 and Comparative Example 1. Paint D was applied in Example 4.

[0043]

[Table 1]

[0044]

As described above, according to the white film of the present invention, particularly, as a magnetic recording medium such as a magnetic recording card, it is excellent in workability, adhesion to a magnetic layer or a print layer, and whiteness. An inexpensive white film can be obtained.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI B32B 27/30 B32B 27/30 A C08K 3/22 C08K 3/22 C08L 33/12 C08L 33/12 67/02 67/02 G11B 5/704 G11B 5/704 // B29C 55/12 B29C 55/12 C08J 7/04 CFD C08J 7/04 CFDJ CFDG B29K 67:00 105: 16 B29L 9:00

Claims (7)

[Claims] 1. A film having a laminated structure of two or more layers and comprising a polyester resin containing titanium oxide particles, wherein the content of titanium oxide particles contained in each layer is 6% by weight.
Not less than 35% by weight, the particle size distribution of the titanium oxide particles contained in each layer is different, and at least one surface has a coating layer of a water-soluble or water-dispersible paint, and at least one surface having a coating layer Roughness R
A white film, wherein a is 0.005 μm or more and 0.3 μm or less, whiteness is 85% or more, and optical density (188 μm thickness conversion) is 0.9 or more. 2. The white film according to claim 1, wherein the main component of the polymer of the coating layer is an acrylic resin. 3. The white film according to claim 1, wherein the coating layer contains an antistatic agent. 4. The white film according to claim 1, wherein a surface treatment is applied to the titanium oxide particles. 5. The white film according to claim 1, wherein the amount of polymer terminal COOH groups of the substrate having the coating layer is 70 or more and 120 or less. 6. A magnetic recording medium comprising a white film according to claim 1 and a magnetic layer provided on one side and a printed layer provided on the other side. 7. The white film according to claim 1, wherein the white film is a simultaneous biaxially stretched film.