JPH11293006A - White polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the subject film having improved light-shield, whiteness, and covering property by having a crosslinked resin dispersed into a white polyester film contg. a polyester resin and white inorganic microparticles. SOLUTION: One hundred pts.wt. of at least one kind of a resin selected from a polyester resin, an acrylic resin, and a urethane resin was added with such additives as a reaction initiator, a reaction accelerator, etc., and with 0.01-50 pts.wt. of a cross-linking agent, then made a crosslinking reaction to give a cross-linked resin in which a temp. at the 0 wt.-loss time in the heating- loss curve is 300 deg.C or above. Blending a polyester resin with 0.5-35 wt.%, pref. 10-25 wt.% of white inorganic microparticles having an average particle dia. of 0.05-5 μm, pref. 0.1-3 μm; 0.01-20 wt.%, pref. 0.1-15 wt.% or the crosslinked resin; and if necessary 0.005-1 wt.%, pref. 0.05-0.5 wt.% of a fluorescent whitening agent, and molding into a film form, give a white polyester film having a thickness of 10-500 μm, an optical density of 0.5-2, whiteness degree of 70-120%, and a color tone of b value (color-difference meter) or 2--5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a white polyester film. More specifically, the present invention relates to a white polyester film having a crosslinked resin inside the film and having excellent whiteness, hiding power, and the like.

[0002]

2. Description of the Related Art Calcium carbonate in polyester resin,
It is well known that a white polyester film is obtained by adding a large amount of white inorganic fine particles such as titanium oxide and barium sulfate. Various types of such white polyester films have been conventionally proposed, and are widely used for various uses such as magnetic recording cards, photographic papers, and receiving papers due to their excellent properties.

[0003]

However, in the conventional white polyester film, when the content of the white inorganic fine particles is increased in order to further improve the properties such as whiteness and concealing property, the surrounding area of the particles is reduced. Voids are formed in the vicinity, and particles having a large void-forming property increase the void amount following the content, so that the smoothness and denseness of the surface layer part are deteriorated,
Scratch resistance tends to decrease.

[0004] Furthermore, although the specific gravity per area may be reduced by increasing the voids, the amount of the white inorganic fine particles is increased due to the fact that the film itself becomes heavier and feels rough, There was a problem that dirt due to shavings was likely to occur.

[0005] The present invention solves the above problems,
It is an object of the present invention to provide a white polyester film that retains a high degree of light-shielding properties and has excellent whiteness, hiding properties, and the like.

[0006]

The white polyester film of the present invention which achieves this object is a white polyester film comprising a polyester resin and white inorganic fine particles as main constituents, wherein a crosslinked resin is contained in the white polyester film. It is a white polyester film characterized by being dispersedly compounded.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the white polyester film of the present invention will be described in more detail.

The film of the present invention is a white polyester film containing a polyester resin and white inorganic fine particles as main components, and is characterized in that a crosslinked resin is dispersed and compounded in the white polyester film.

In the present invention, "the polyester resin and the white inorganic fine particles are the main constituents" means that the polyester resin and the white inorganic fine particles are 50% by weight in the film,
Preferably, it refers to one occupying 60% by weight or more, and other substances other than these may be added as appropriate.

In the present invention, the crosslinked resin is a resin obtained by subjecting a resin or a resin to which an additive such as a reaction initiator or the like is added to undergo a crosslinking reaction by heat, light, electron beam or the like. Has a three-dimensional network structure.
Such a resin does not dissolve in the polyester resin and, when melt-mixed, is dispersed in the form of fine particles in the polyester resin, and may form fine voids at the interface between the particles by stretching. Furthermore, since the specific gravity is smaller than the white inorganic fine particles, when finely dispersed to the same extent as the white inorganic fine particles, the fine particles in the film under the same amount of addition are much more than the white inorganic fine particles. Becomes

As the cross-linked resin in the present invention, a thermoplastic resin or a thermosetting resin capable of performing a cross-linking reaction can be used.
Polyamide-based resins, polystyrene-based resins, polyurethane-based resins, polyolefin-based resins, acrylic resins, phenolic resins, epoxy resins, melamine resins, at least one selected from silicon resins and the like can be used. From the viewpoint of the crosslinking method, its reactivity, various properties of the crosslinked resin, etc., those which can achieve thermal crosslinking by using a crosslinking agent in combination can be more preferably used.

Further, in the present invention, the heat resistance and dispersibility of the crosslinked resin, the abrasion resistance and mechanical properties of the film of the present invention,
From the viewpoint of whiteness and the like, it is preferable to use a polyester resin, an acrylic resin, or a polyurethane resin among the above resins.

The crosslinked resin has a heating weight loss curve at a temperature at the time of weight loss of 10% (under a nitrogen atmosphere,
When the degree of cross-linking is increased by using a thermogravimetric analyzer TG-30M manufactured by Shimadzu Corporation at a temperature rise rate of 20 ° C./min) of 300 ° C. or more, preferably 350 ° C. or more, heat resistance and abrasion resistance are particularly high. Is more preferable.

The crosslinking agent in the present invention is a resin or a compound which undergoes a crosslinking reaction with a functional group present in the resin, for example, a hydroxyl group, a carboxyl group, a glycidyl group, an amide group, and the like. Rolled urea, melamine, acrylamide,
A polyamide resin, an epoxy compound, an isocyanate compound, a coupling agent, an aziridine compound, an oxazoline compound, or the like can be used. In the present invention, among these, it is particularly preferable to use a melamine-based, oxazoline-based, or isocyanate compound from the viewpoint of crosslinking reactivity and the like.

The crosslinking agent may be used alone or in combination of two or more in some cases. The amount of the cross-linking agent may be appropriately selected depending on the type of the cross-linking agent, but is usually preferably 0.01 to 50 parts by weight, and more preferably 0.2 to 30 parts by weight, based on 100 parts by weight of the resin solids.
A range of parts by weight is more preferred. It is more preferable to use a crosslinking catalyst together with the crosslinking agent because the crosslinking reaction proceeds more.
The crosslinking reaction of a resin to which a crosslinking agent is added is generally performed by heating.

The amount of the crosslinked resin dispersed in the film is not particularly limited.
% By weight, more preferably in the range of 0.1 to 15% by weight. When the amount of the dispersion is out of the above range, it is difficult to improve the properties such as whiteness and concealing property, or the smoothness and the denseness of the film surface may be deteriorated.

The average dispersion diameter of the crosslinked resin in the film is preferably 0.05 to 5 μm,
Those having a range of from 3 to 3 μm are more preferable. If the average dispersion diameter is out of the above range, uniform dispersion may be difficult or the smoothness of the film surface may be deteriorated, which is not preferable.

Further, as the crosslinked resin, a resin which has been subjected to a surface treatment or the like for improving dispersibility, abrasion resistance and the like may be used.

In the present invention, it is desirable to add a fluorescent whitening agent to the white polyester film of the present invention in order to give a high-quality image having sharper whiteness and blue tint.

In the present invention, the polyester resin is
A polymer obtained by condensation polymerization from a diol and a dicarboxylic acid, and examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid, and sebacic acid. Are represented by ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexane dimethanol and the like. Specifically, for example, polyethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene-
2,6-naphthalenedicarboxylate and the like can be used. In the case of the present invention, polyethylene terephthalate and polyethylene naphthalate are particularly preferred.

Of course, these polyester resins are
It may be a homopolyester or a copolyester. Examples of the copolymerization component include diol components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol, adipic acid, sebacic acid, phthalic acid, isophthalic acid, and the like. Dicarboxylic acid components such as 2,6-naphthalenedicarboxylic acid and 5-sodium sulfoisophthalic acid can be used.

In the polyester resin, if necessary, appropriate additives such as a heat stabilizer, an oxidation stabilizer, a weather stabilizer, and the like, as long as the effects of the present invention are not impaired. You may mix | blend an ultraviolet absorber, an antistatic agent, a dye, a dispersing agent, a coupling agent, etc.

The polyester resin used in the present invention is preferably polyethylene terephthalate. This is because the polyethylene terephthalate film is excellent in water resistance, durability, chemical resistance and the like.

The white inorganic fine particles in the present invention include:
For example, zinc carbonate, calcium carbonate, magnesium carbonate, titanium oxide, magnesium oxide, zinc oxide, silica, talc, kaolin, lithium fluoride, calcium fluoride, barium sulfate, zinc sulfide, alumina, calcium phosphate, mica, and the like can be used. it can. At least one selected from these may be used, but in the present invention, inorganic particles such as calcium carbonate, titanium oxide, and barium sulfate may be used particularly in view of whiteness and reflectance. More preferred. Further, the white inorganic fine particles may be in a form such as porous or hollow porous,
Further, a resin which has been subjected to a surface treatment for improving dispersibility in a resin may be used.

The average particle size of the white inorganic fine particles is 0.05
To 5 μm, more preferably 0.1 to 3 μm. If the average particle diameter is out of the above range, uniform dispersion may be difficult or the smoothness of the film surface may be unfavorably deteriorated. The amount of the white inorganic fine particles is not particularly limited, but is preferably 5 to 35% by weight, more preferably 10 to 25% by weight. If the amount is less than the above range, it is difficult to improve the properties of the film, such as whiteness and hiding power. On the other hand, if it is above the above-mentioned range, the film may be broken at the time of stretching or inconvenience such as generation of powder at the time of post-processing may occur.

In the present invention, in addition to the above-mentioned white inorganic fine particles, fine particles precipitated by the reaction of a catalyst residue with a phosphorus compound in a polyester resin polycondensation reaction system can be used in combination. As the precipitated fine particles, for example, those composed of calcium, lithium and phosphorus compounds or those composed of calcium, magnesium and phosphorus compounds can be used. The content of these particles in the resin is preferably in the range of 0.05 to 1 part by weight based on 100 parts by weight of the polyester resin.

In the present invention, the fluorescent whitening agent is a polymer that absorbs ultraviolet light in sunlight or artificial light, converts the ultraviolet light into visible light of purple to blue, and radiates the light. A compound that promotes whiteness without reducing the lightness of the substance. Examples of the fluorescent whitening agent include trade names "Ubitek" (Ciba-Geigy), "OB-1" (Eastman), "TBO" (Sumitomo Seika Co., Ltd.) and "Kay Coal" (Nippon Soda Co., Ltd.). , "Kayalite" (Nippon Kayaku Co., Ltd.), "Ryukopua" EGM (Client Japan Co., Ltd.) and the like can be used. The optical brightener is
There is no particular limitation.
More than one kind may be used in combination. In the present invention, it is desirable to select a resin that has particularly excellent heat resistance, has good compatibility with the polyester resin, can be uniformly dispersed, has little coloring, and does not adversely affect the resin.

The content of the fluorescent whitening agent is preferably from 0.005 to 1% by weight, more preferably from 0.05 to 0.5% by weight. If the content is lower than the above range, it is difficult to obtain a sufficient whitening effect, and if the content exceeds the above range, uniform dispersibility and whiteness tend to be reduced.

In the present invention, the thickness of the white polyester film is not particularly limited.
m, preferably in the range of about 20 to 300 μm, is preferred because of excellent handling properties in practical use as a substrate film.

The optical density of the white polyester film of the present invention is preferably 0.5 or more and 2 or less. More preferably, it is 0.8 or more and 1.5 or less. When the optical density is less than 0.6, the back side of the film is transparent because the concealing property of the film is small, which is generally not preferable.
In addition, in order for the optical density to exceed 2, it is necessary to include a large amount of particles, which may undesirably reduce the strength of the film.

In the white polyester film of the present invention, the whiteness is preferably 70% or more and 120% or less. More preferably, it is 80% or more and 110% or less. If the whiteness is less than 70%, the whiteness is insufficient and 110%
In order to obtain a whiteness exceeding 多量, it is necessary to add a large amount of particles and to form a large amount of voids, and the surface smoothness may be impaired or the film strength may decrease.

The white polyester film of the present invention, which is preferably produced, has a whiteness of generally 90% or more, more preferably 95% or more, and exhibits a very beautiful whiteness without dullness.

The white polyester film of the present invention preferably has a color tone b value determined by a color difference meter in the range of 2 to -5, preferably 0 to -3, since the whiteness becomes clearer. When the color tone b value is out of the above range, the apparent whiteness is insufficient, and when used as an image receiving substrate, the sharpness of the color tone is likely to deteriorate.

The white polyester film of the present invention has a surface gloss of 40% or more, preferably 50% or more. When the glossiness is 40% or less, it is difficult to form a high-definition image when used as an image receiving substrate.

The white polyester film of the present invention may be used alone, or may be used by being appropriately laminated to paper or the like as desired.

Next, some examples of the method for producing the white polyester film of the present invention will be described, but the present invention is not limited to only these examples.

A polyester resin chip, a white inorganic fine particle master chip, and a crosslinked resin are mixed, sufficiently vacuum-dried, and then supplied to an extruder heated to 270 to 300 ° C. At this time, the form of the crosslinked resin may be fine particles or a master chip, or may be a finely pulverized product coated on the surface of the polyester film. Particularly, a finely pulverized product coated on the film surface is preferable because of excellent dispersibility.

The melted sheet is subjected to a surface temperature of 10
On a drum cooled to 60 ° C., it is tightly cooled and solidified by static electricity to produce an unstretched film. The unstretched film is
Guided to a group of rolls heated to 0 to 120 ° C,
The film is stretched up to 5 times and cooled with a group of rolls at 20 to 30 ° C.

Subsequently, the film stretched in the longitudinal direction was guided to a tenter while gripping both ends of the film with clips, and the film was 90 to 14
The film is horizontally stretched in a direction perpendicular to the longitudinal direction in an atmosphere heated to 0 ° C.

The stretching ratio is 2 to 5 times each in the longitudinal and transverse directions, and the area ratio (longitudinal stretching ratio × lateral stretching ratio) is preferably 6 to 20 times. When the area magnification is less than 6 times, the whiteness of the obtained film becomes insufficient, and when it exceeds 20 times, the film tends to be easily broken during stretching.

In order to impart the flatness and dimensional stability of the biaxially stretched film thus obtained, 150
The film of the present invention can be obtained by heat-setting at ２３０230 ° C., cooling slowly and uniformly, and then cooling to room temperature.

[0042]

[Method of measuring and evaluating characteristics] The characteristic value of the present invention is as follows.
According to the following evaluation methods and evaluation criteria.

(1) Average Particle Size of Particles The particles are dispersed in ethanol, and measured using a centrifugal sedimentation type particle size distribution analyzer (CAPA4500 manufactured by Horiba, Ltd.), and the volume average diameter is calculated to obtain the average particle diameter. And

(2) Color Tone The surface color of the film was measured using a color difference meter ND- manufactured by Nippon Denshoku Industries Co., Ltd.
Measurement is performed using 6B, and the determination is made based on the obtained b value.

(3) Whiteness According to JIS-L-1015, U-manufactured by Shimadzu Corporation
When the reflectance at a wavelength of 450 nm and 550 nm is B% and G% using V-2600, the whiteness (%) is expressed by 4B-3G.

(4) Concealing property Obtained by optical density, an optical densitometer (TR92 manufactured by Macbeth)
It measured using 7). The greater the measured value, the higher the concealment property.

(5) Gloss Digital gonio-gloss meter UGV-5D (Suga Test Instruments Co., Ltd.)
Was obtained at a variable light angle of 60 ° and a light incident angle of 60 °.

(6) Content of Crosslinked Resin A certain amount of the film is dissolved or alkali-decomposed in orthochlorophenol, and the undissolved material is separated by centrifugation. Next, the undissolved matter was separated from the white inorganic fine particles by the difference in specific gravity, and the content (%) was determined from the difference in weight between each.

(7) Scratch resistance A film obtained by slitting the film into a tape having a width of 1/2 inch was moved on a stainless steel guide pin (surface roughness: 40 nm by Ra) using a hoop traveling tester at a traveling speed of 30 m. /
Min, wrap angle 90 °, output side tension 50g, number of runs 15
Run back and forth. After running, the powder adhering to the surface of the guide pin was visually observed, and the judgment was made based on the following criteria.

5 points with no powder attached 5 points with slight powder attached 3 points a large amount of powder attached 1 point 4 points between each point, 2 points higher than 4 points Was determined to have good scratch resistance.

[0051]

The present invention will be described with reference to the following examples and comparative examples, but the present invention is not limited to these examples.

Example 1 A polyethylene terephthalate chip was provided with 14% by weight of anatase type titanium oxide having an average particle diameter of 0.23 μm as white inorganic fine particles and a styrene-divinylbenzene crosslinked resin having an average particle diameter of 0.21 μm as a crosslinked resin. Raw materials containing 2.5% of a polymer and 0.04% by weight of an optical brightener “OB-1” (manufactured by Eastman) were mixed, and the mixture was mixed at 180 ° C.
After drying in vacuum for 3 hours, the mixture was supplied to an extruder, melted at 285 ° C. by a conventional method, and extruded into a sheet from a T-die die.

Next, the melt sheet was tightly cooled and solidified on a cooling drum kept at a surface temperature of 25 ° C. by an electrostatic charge method. Subsequently, the unstretched film was stretched 3.3 times using a group of rolls heated to 97 ° C. in the longitudinal direction according to a conventional method, and cooled with a group of rolls at 25 ° C. Further, the stretched film was guided to a tenter and stretched 3.5 times in a direction perpendicular to the longitudinal direction in an atmosphere heated to 120 ° C. Thereafter, the film was heat-set at 220 ° C. in a tenter, uniformly cooled, and then wound up to obtain a white polyester film having a thickness of 50 μm.

The properties of the white polyester film thus obtained are as shown in Table 1, and were excellent in whiteness, hiding properties and scratch resistance.

Example 2 Based on Example 1, as the raw material white inorganic fine particles to be supplied to the extruder of Example 1, a material obtained by adding 18% by weight of barium sulfate having an average particle diameter of 0.6 μm was used. A film was obtained in the same manner as in Example 1. As shown in Table 1, the properties of the white polyester film were excellent in each property.

Example 3 Based on Example 1, as a cross-linked resin as a raw material to be supplied to the extruder of Example 1, a paint having the following composition was coated on both sides before completion of orientation in a polyethylene terephthalate film forming process. 50 μm thick polyester film “Lumirror” having a final coating thickness of 0.4 μm applied to
The film was finely pulverized to 10 mm square or less using a cutting machine by using a film cutter (manufactured by Toray Industries, Inc.). A film was obtained in the same manner as in Example 1, except that the amount was 0.36% by weight. As shown in Table 1, the properties of the white polyester film were excellent in each property. In the coating in the film forming process, first, an unstretched film extruded on a cooling drum by a conventional method is stretched 3.2 times in a longitudinal direction at 95 ° C., and then the surface is subjected to a corona discharge treatment. Then, the paint was applied by a gravure coat method. Thereafter, the coating was dried and stretched 3.4 times at 125 ° C. while drying, and then subjected to a heat treatment in a 220 ° C. atmosphere while relaxing 3%.

[Coating composition] Resin: 2 parts each of methacrylic acid and glycidyl acrylate
0 mol% graft-bonded water-dispersible polyester copolymer (trade name: "Pesthresin" 604 manufactured by Takamatsu Yushi Co., Ltd.)
G) 100 parts by weight ・ Cross-linking agent: 10 parts by weight of melamine-based cross-linking agent (trade name: “Nikarac” MW12LF manufactured by Sanwa Chemical Co., Ltd.) ・ Additives: 2 parts by weight of silica sol (average particle size 0.14 μm) 4 Based on Example 3, a film was applied in the same manner as in Example 3 except that a coating material having the following composition was applied to both sides as a crosslinked resin as a raw material to be supplied to the extruder of Example 3. I got As shown in Table 1, the properties of the white polyester film were excellent in each property.

[Coating composition] Resin: Methyl methacrylate / ethyl acrylate (50/50) mol%, carboxyl group as a functional group,
100 parts by weight of a water-dispersible acrylic copolymer resin into which 2.5 parts by weight of each methylol group is introduced. 10 parts by weight of a melamine-based crosslinking agent (trade name: "Nikalac" MW12LF manufactured by Sanwa Chemical Co., Ltd.) Additive: silica sol (average particle size: 0.14 μm) 2 parts by weight Example 5 Based on Example 3, paint having the following composition was applied to both surfaces as a crosslinked resin as a raw material to be supplied to the extruder of Example 3 A film was obtained in the same manner as in Example 3, except that the film was used. As shown in Table 1, the properties of the white polyester film were excellent in each property.

[Coating composition] Resin: 100 parts by weight of a water-based self-emulsifying reactive urethane (trade name: "Elastron" E-37 manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Additive: silica sol (average particle diameter: 0.1%) 14 μm) 2 parts by weight Comparative Example 1 Based on Example 1, the raw material supplied to the extruder of Example 1 was a system excluding a crosslinked resin, and calcium carbonate having an average particle diameter of 1.2 μm was used as white inorganic fine particles. A film was obtained in the same manner as in Example 1 except that 16% by weight was used. Table 1 shows the properties of the white polyester film.
As shown in Table 1, the glossiness was low and the scratch resistance was poor.

Comparative Example 2 Based on Example 1, the raw material supplied to the extruder of Example 1 was a system excluding the crosslinked resin, and 14 wt. Of barium sulfate having an average particle diameter of 1.2 μm as white inorganic fine particles. A film was obtained in the same manner as in Example 1 except that the film containing% was used. Table 1 shows the properties of the white polyester film.
It was shown to. The film had low concealing light and poor scratch resistance.

[0061]

[Table 1]

[0062]

The white polyester film of the present invention is
A polyester resin and white inorganic fine particles were used as main components, and a cross-linked resin was further dispersed and compounded, so that light scattering effectively acted to obtain a high-white color, and the whiteness was based. When used for photographic paper or thermal transfer receiving paper, it can give a high-quality image different from conventional products.

Further, for the same reason, the white polyester film of the present invention also has excellent light-shielding properties, so that transmitted light is small and a beautiful white property can be exhibited. In addition, a particularly clear image can be provided.

Since the white polyester film of the present invention has the above-mentioned excellent properties, it can be used for a card, a seal,
It can be suitably used for a wide range of applications such as courier slips, video printer receiving paper, barcode printer receiving paper, inkjet receiving paper, posters, maps, dust-free paper, display boards, photographic paper, copy paper, etc. It is optimally used for a substrate to be printed or printed on, especially a color printing substrate.

Claims (9)

[Claims] 1. A white polyester film comprising a polyester resin and white inorganic fine particles as main components,
A white polyester film, wherein a crosslinked resin is dispersed and compounded in the white polyester film. 2. The dispersion compounding amount of the crosslinked resin is 0.01
The white polyester film according to claim 1, wherein the content is in the range of -20% by weight. 3. The crosslinked resin is a polyester resin,
The white polyester film according to claim 1, comprising at least one selected from an acrylic resin and a urethane resin. 4. The white polyester film according to claim 3, wherein the crosslinking is carried out by using a crosslinking agent in combination. 5. The white polyester film according to claim 1, wherein the white polyester film contains a fluorescent whitening agent. 6. A white polyester film according to claim 1, wherein the optical density is 0.5 or more and 2 or less, and the whiteness is 70% or more and 120% or less. . 7. The color tone b value obtained by the color difference meter is 2 to
The white polyester film according to any one of claims 1 to 6, wherein the white polyester film is in the range of (5). 8. The white polyester film according to claim 1, having a glossiness of 40% or more. 9. The white polyester film according to claim 1, wherein the crosslinked resin is supplied from a pulverized product coated on the surface of the polyester film.