JPH069811A - White polyester film - Google Patents

Abstract

PURPOSE:To obtain a white polyester film high in hiding power and few in yellow. CONSTITUTION:A white film having 20% whole light transmittance of 25mum thickness and -0.5 to 4.0 color b value is attained by jointly using white pigment and blue dye.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white polyester film having excellent hiding power and sufficient whiteness when used for labels, posters, recording papers, packaging materials and the like.

[0002]

2. Description of the Related Art White film, which is a paper substitute mainly made of synthetic resin, has higher water resistance, moisture absorption dimensional stability, surface stability, printing gloss and sharpness, and mechanical strength than natural paper. And so on. In recent years, application development has been promoted by making use of these advantages. Polyethylene, polypropylene, polyester, etc. are used as the main raw material of the white film. Among them, polyester typified by polyethylene terephthalate has a high heat resistance,
It is excellent in that it is strong and can be applied to a wide range of applications.

As a method for obtaining a white film mainly made of polyester, a method of adding a white pigment such as titanium dioxide, barium sulfate or calcium carbonate has been disclosed. However, there is a limit to how much the hiding power can be imparted by the white pigment, and when the white film is thin, the hiding power is particularly insufficient. In addition, there is a shortage in whiteness by adding only a white pigment, and it is common to improve the apparent whiteness by adding a fluorescent whitening agent, etc. The current situation is that there is also a problem with sex.

[0004]

DISCLOSURE OF THE INVENTION The present invention is to improve the whiteness of a white polyester film and to improve the above-mentioned drawbacks, that is, the hiding power and lack of whiteness of the white film, such as labels, posters and recording papers. It is intended to provide a base material suitable for the above.

[0005]

[Means for Solving the Problems] That is, the above-mentioned problems are at least one surface of a polyester mixture layer (A) in which 1 to 40 parts by weight of titanium dioxide and 0.01 to 1.00 parts by weight of a blue dye are added to polyester. 2 for polyester
By providing the white polyester layer (B) containing 1 to 40 parts by weight of titanium oxide, the total light transmittance of 25 μm is 20% or less, and the color b value is −0.5.
Achievable with a white film in the range of -4.0.

By adding a thermoplastic resin which is incompatible with polyester to the layer A of such a film, it is possible to impart paper-like writability as well as cushioning properties and lightweight properties. It is possible. The polyester in the present invention is produced by polycondensing an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, or naphthalenedicarboxylic acid or an ester thereof with a glycol such as ethylene glycol, diethylene glycol, 1,4-butanediol or neopentyl glycol. Polyester. These polyesters may be obtained by directly reacting an aromatic dicarboxylic acid with a glycol, and then transesterifying an alkyl ester of an aromatic dicarboxylic acid with a glycol, followed by polycondensation, or a diglycol ester of an aromatic dicarboxylic acid. Is produced by a method such as polycondensation. A typical example of such polyester is polyethylene terephthalate,
Examples thereof include polyethylene butylene terephthalate and polyethylene 2,6 naphthalate. This polyester may be a homopolymer or a copolymer of a third component. In any case, in the present invention, a polyester in which the ethylene terephthalate unit, the butylene terephthalate unit or the ethylene-2,6-naphthalate unit is 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more is preferable.

The crystal system of titanium dioxide as a white pigment used in the present invention may be anatase type or rutile type, and may be subjected to various surface treatments. The 2
The addition of 1 to 40 parts by weight of titanium oxide is for ensuring the concealing property and the whiteness. When it is 1 part by weight or less, the concealing property and the whiteness cannot be obtained, which is not preferable, and 40 parts by weight or more. In that case, the stretchability is significantly reduced,
Not preferable.

The blue dye of the present invention is an organic compound having a strong absorption in the visible region, for example, triphenylmethane type,
Indamine, azine, oxazine, thiazine,
Examples include anthraquinone type and indigoid type.
The reason why these dyes are added in an amount of 0.01 to 1.00 parts by weight is to obtain a hiding power by absorbing visible parts and to emphasize the bluish color of the entire film to obtain whiteness. 0.01
If it is less than 1 part by weight, a sufficient effect cannot be obtained, which is not preferable. If it is more than 1.00 part by weight, not only is it disadvantageous in terms of cost, but also due to the interaction with the polyester,
By-products are generated and cause deterioration of the polyester, which is not preferable.

The resin incompatible with the polyester of the present invention may be either a polyolefin type or a polystyrene type, and the polyolefin type may be polypropylene, polyethylene, poly 4-methylpentene or the like, and the polystyrene type may be polystyrene or a butadiene-styrene copolymer. Etc. In the present invention, such a resin mixture may be prepared by kneading the above-mentioned resin and additive in an extruder, or the resin and each additive may be kneaded in advance in a kneader and melt-extruded from the extruder. . The mixture thus obtained is melt-extruded onto a cooling drum, cooled and solidified, and the sheet is stretched at least uniaxially.
It is possible to obtain a white polyester film having paper-like writability and cushioning properties and increased mechanical strength. Further, by heat-treating such a film, a white polyester film having good thermal dimensional stability can be obtained.

In the present invention, it is necessary to form a so-called composite film in which the surface layer and the center layer are laminated, but the method is not particularly limited. However, from the viewpoint of productivity, it is most preferable to use a so-called co-extrusion method in which raw materials for the surface layer and the central layer are extruded from different extruders, introduced into one die to obtain an unstretched sheet, and then oriented at least uniaxially. .

In the present invention, it is particularly important that 1 to 40 parts by weight of titanium dioxide and 0.01 to 1.00 of a blue dye are added to at least one side of the layer (A) of polyester 60. By stacking the layer (B) in which 1 to 40 parts by weight of titanium dioxide is added to ˜99 parts by weight, the total light transmittance of 25 μm is 20% or less and the color b value is −0. .5 to -4.
Achievable with a white film in the 0 range. Absorption of visible light by the blue dye of the layer A not only greatly improves the hiding power, but also has the effect of improving the whiteness.

Such a white polyester film has not only a dramatically improved hiding power but also a significantly improved whiteness as compared with conventionally proposed white films, and therefore the white polyester film of the present invention. When is used as a base material, labels, posters, recording papers, packaging materials and the like can be thinned and can be developed into high-grade applications such as photographic paper.

[0013]

EXAMPLES Examples and comparative examples of the present invention will be described below. The measurement / evaluation methods used in the present invention are shown below. 1) Measurement of light transmittance (T%) In accordance with JIS-B0601-1982, Poic integrating sphere type H. T. The light transmittance of the film was measured using an R meter (manufactured by Nippon Seimitsu Optical Co., Ltd.). The smaller this value is, the higher the hiding property is. 2) Measurement of apparent specific gravity (SG) A film is accurately cut into a square of 5.00 cm × 5.00 cm, and its thickness is measured at 50 points to obtain an average thickness of t microns, and the weight thereof is measured to 0.1 mg. And Wg
And calculated by the following formula.

SG = W / 5 × 5 × t × 10000 3) Measurement of whiteness J using a color difference meter Z-1001 (manufactured by Nippon Denshoku Industries Co., Ltd.)
It was measured by the B method (two-wavelength method) of IS-L1015-1981.

[0015]

Example 1 As a raw material, rutile type 2 was added to 94.9 parts by weight of polyethylene terephthalate having an intrinsic viscosity of 0.62.
5 parts by weight of titanium oxide, blue dye (anthraquinone type,
The resin mixture prepared by mixing 0.10 part by weight of Solvent Blue 94) with 90 parts by weight of polyethylene terephthalate having an intrinsic viscosity of 0.62 and 10 parts by weight of rutile type titanium dioxide has a thickness after biaxial stretching of 2. 5/20 / 2.5
Multi-layered pieces were extruded from a T-die by a co-extrusion method so as to have a micron size, and electrostatically adhered and solidified on a cooling rotary roll to obtain a white polyester sheet. This sheet was continuously stretched at 90 ° C. by a factor of 3.8 with a roll stretching machine, further stretched at 135 ° C. by a factor of 3.5, and heat-set at 220 ° C. to obtain a white polyester film.

The film had a total light transmittance of 20% and a whiteness of 95, and was a film having excellent hiding power and whiteness.

[0017]

Comparative Example 1 A white polyester film was obtained in the same manner as in Example 1, except that the red dye (aminoketone type, Butred 33) was used instead of the blue dye as the raw material for the center layer. The total light transmittance of this film is 20% and the whiteness is 70.
The hiding power was excellent, but the film had low whiteness.

[0018]

Example 2 A white polyester film was obtained in the same manner as in Example 1, except that 15 parts by weight of general-purpose polystyrene was added to the central layer as a void developing agent. The total light transmittance of this film is 15% and the whiteness is 1
00, the hiding power and the whiteness were excellent, and the apparent specific gravity was 1.10, and it had a writing property like paper.

[0019]

Comparative Example 2 A white polyester film was obtained in the same manner as in Example 2, except that the blue dye in the central layer was changed to the red dye (the same product as in Comparative Example 1). The total light transmittance of this film was 15%, which was excellent in hiding power, and had an apparent specific gravity of 1.10 and had a writing property similar to paper.
The film had a whiteness of 73 and a lack of whiteness.

[0020]

The white polyester film of the present invention is
Compared with conventional white polyester film, this white polyester film has excellent hiding power and has especially improved whiteness, so it has sufficient hiding power when used for labels, posters, recording paper, packaging materials, etc. Since it has, the film can be thinned, the overwriting property of the delivery slip and the like can be improved, or the entire thickness of the dictionary and the like can be reduced.

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Claims (2)

[Claims] 1. A total light transmittance of 20 at a thickness of 25 μm.
% Or less and a color b value of -0.5 to -4.0, a white polyester film. 2. A white polyester film having a feature that the white polyester film according to claim 1 contains fine voids therein.