JPH11300915A - White polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To upgrade the glare protection properties, whiteness, concealing properties and pliability by laminating a polyester layer composed mainly of a polyester resin and white inorganic microparticles on one of the surface layer of a polyester layer composed mainly of the polyester resin, white inorganic microparticles and a crosslinked resin, as a base layer. SOLUTION: A polyester layer A is composed mainly of a polyester resin, white inorganic microparticles and a crosslinked resin as a base layer, and on at least one of the surface layers, a polyester layer B composed mainly of the polyester resin and the white inorganic microparticles is laminated. The polyester layer A and the polyester layer B may be of the same polyester composition or may be of a different polyester composition from each other. The white inorganic microparticles to be used are inorganic particles such as a calcium carbonate, a titanium oxide and a barium sulfate from the viewpoint of whiteness and reflectance. Thus it is possible to improve the glare protection properties, whiteness, concealing properties and pliability.

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 multilayer structure, having a layer containing a crosslinked resin, and having excellent whiteness, concealing properties, 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 applied to various uses such as magnetic recording cards, photographic papers, and receiving papers due to their excellent properties. Among them, as a white polyester film, the film itself has a multi-layer structure, and in a film in which the content of the white inorganic fine particles in the base layer portion and the surface layer portion is changed, characteristics such as scratch resistance and punching property are improved. It is known that As such a white polyester film, for example, JP-A-7-
187904, JP-A-63-87231 and the like are disclosed.

[0003]

However, in the conventional white polyester film, when the content of the white inorganic fine particles in each layer is increased in order to further improve the properties such as whiteness and concealing property, the particle size of the particles is increased. Voids are formed around and in the vicinity, and particles having a large void-forming property increase in the amount of voids in accordance with the content thereof, so that the smoothness and the denseness of the surface layer portion are deteriorated, and the scratch resistance is likely to be reduced.

Further, increasing the amount of white inorganic fine particles not only deteriorates the mechanical properties, but also causes the film itself to become heavier and lumpy, and is liable to be stained by shavings in post-processing. was there.

[0005] The present invention solves the above problems,
Maintains a high degree of light shielding, and has excellent whiteness, hiding power,
An object is to provide a white polyester film having flexibility and the like.

[0006]

The white polyester film of the present invention that achieves this object has a polyester layer (A) containing a polyester resin, white inorganic fine particles and a crosslinked resin as main components, and a surface layer of the polyester layer (A). A white polyester film comprising a polyester layer (B) mainly composed of a polyester resin and white inorganic fine particles laminated on at least one surface.

[0007]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a polyester resin is a polymer obtained by condensation polymerization of a diol and a dicarboxylic acid. Examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, and adipine. Acids, sebacic acid and the like, and diols are ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexanedimethanol 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. Also, in this polyester resin, if necessary, appropriate additives within a range not impairing the effects of the present invention, for example, heat stabilizers, oxidation stabilizers, weather stabilizers, ultraviolet absorbers, antistatics Agents, dyes,
You may mix | blend a dispersing agent, a coupling agent, etc.

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

In the present invention, the polyester layer (A)
The polyester layer (B) is provided on the surface layer of the above. In this case, even if each layer is the same polyester composition,
Different polyester compositions may be used. In particular, it is more preferable that each layer has a different composition, for example, the polyester layer (A) is a homopolyester and the polyester layer (B) is a copolyester, because characteristics such as easy adhesion can be obtained. Further, it is preferable that the polyester layer (A) is polyethylene terephthalate and the polyester layer (B) is polyethylene naphthalate, because the effects of improving weather resistance and rigidity can be obtained.

In the present invention, the term "layer comprising the main component" refers to a layer whose component occupies 50% by weight, preferably 60% by weight or more in the layer. You may.

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. 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 the form of a porous or hollow porous material, or may be those subjected to a surface treatment for improving dispersibility in a resin.

The average particle diameter 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 more than the above range, inconveniences such as tearing of the film at the time of stretching and generation of powder at the time of post-processing may occur. The properties and form of the white inorganic fine particles may be the same or different in each layer.

In the present invention, in addition to the above-mentioned white inorganic fine particles, fine particles precipitated by a reaction between a catalyst residue and a phosphorus compound in a polycondensation reaction system of a polyester resin 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 content of the white inorganic fine particles in each layer has a relationship of polyester layer (A)> polyester layer (B), which means that the film of the present invention has a problem of whiteness, color tone, scratch resistance and the like. Desirable.

In the present invention, the cross-linked resin is a resin obtained by subjecting a resin or a resin to which an additive such as a reaction initiator or a reaction accelerator has been added to undergo a cross-linking reaction by heat, light, an 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 that of 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 addition of the same amount 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, heat resistance and dispersibility of the crosslinked resin, 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 was heated at a temperature at a weight loss of 10% by weight in a heating weight loss curve (under a nitrogen atmosphere,
The measurement is performed using a thermogravimetric analyzer TG-30M manufactured by Shimadzu Corporation. The heating rate is 20 ° C./min. ) Is preferably 300 ° C. or higher, more preferably 350 ° C. or higher, since heat resistance and abrasion resistance are particularly improved.

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 is appropriately selected depending on the type of the cross-linking agent.
The content is preferably 0.01 to 50 parts by weight, more preferably 0.2 to 30 parts by weight. 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 polyester layer (A) is not particularly limited.
0.01-20% by weight is preferred, and 0.1-15% by weight
Are more preferable. 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 polyester layer (A) is preferably from 0.05 to 5 μm, more preferably from 0.1 to 3 μm. 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, the crosslinked resin may be one which has been subjected to a surface treatment or the like for improving dispersibility, abrasion resistance and the like.

In the present invention, the polyester layer (A) and / or the polyester layer (A) may be used in order to give the white polyester film of the present invention a fine image having a sharper whiteness or bluish color.
Alternatively, it is desirable to add a fluorescent whitening agent to (B).

In the present invention, a fluorescent whitening agent is a polymer that absorbs ultraviolet light in sunlight or artificial light, converts the ultraviolet light into visible light of violet to blue, and radiates it. 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 described above, 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, the uniform dispersibility and the whiteness tend to decrease.

When the white polyester film of the present invention is used for, for example, an image receiving base material, it imparts flexibility and cushioning properties to improve printability and transferability, and to reduce the weight of the image receiving base material. For the polyester layer (A),
It is preferable to include a thermoplastic resin different from the polyester and incompatible with the polyester.

In the present invention, the above-mentioned incompatible thermoplastic resin is a thermoplastic resin other than polyester, which is not compatible with polyester. Such a resin has a glass transition temperature (hereinafter abbreviated as “Tg”) corresponding to the polyester in a system in which the polyester and the thermoplastic resin are melted in a measurement using a method such as a differential scanning calorimeter (DSC). ) Is a resin in which Tg corresponding to the thermoplastic resin is observed in addition to the above. As the incompatible thermoplastic resin, for example, a polyolefin resin, a polystyrene-based resin, a fluorine-based resin, or the like can be used.The resin is dispersed in a particle form in the polyester, and voids are formed in the polyester film by stretching. The effect of forming is large.

The melting point of such a thermoplastic resin is preferably lower than the melting point of the polyester and higher than the temperature used to orient the film support. From these points, a polyolefin resin is preferable among the thermoplastic resins. The polyolefin resin may be any resin as long as it can be added to polyester to form a film, for example, low-density polyethylene, high-density polyethylene, polypropylene, polybutene, polymethylpentene, etc. be able to.
Also, it is not necessarily limited to homopolymer,
These copolymers may be used. Among them, a polyolefin resin having a small critical surface tension is preferable, and polypropylene and polymethylpentene are preferable. In particular, polymethylpentene is particularly preferable because it has a large difference in surface tension from polyester and a high melting point, so that it is easy to form fine bubbles during stretching.

The content of the thermoplastic resin is preferably 1 to 30% by weight in the layer, more preferably 5 to 20% by weight. When the addition amount is less than the above range, the amount of generation of fine bubbles is small, and it is difficult to reduce the apparent density of the white polyester film. If the amount exceeds the above range, the stretchability of the film may be deteriorated, and the film-forming property may be deteriorated.

In the present invention, in order to finely disperse the thermoplastic resin and promote the generation of uniform fine bubbles, it is preferable to include a dispersant together with the thermoplastic resin.

Compounds having such effects include, for example, polyalkylene glycols or copolymers thereof,
Ethylene oxide / propylene oxide copolymer,
Dodecylbenzenesulfonic acid sodium salt, glycerin monostearate, tetrabutylphosphonium paraaminobenzenesulfonate and the like can be used. Among them, the present invention preferably contains a polyalkylene glycol or a copolymer thereof.For example, polyethylene glycol, polypropylene glycol, a copolymer of polyethylene glycol and propylene glycol, and methoxypolyethylene glycol can be used. It is not limited to these.

The amount of the dispersant added is preferably 0.1 to 5% by weight, more preferably 0.5 to 3% by weight. When the addition amount is less than 0.1% by weight, the effect of finely dispersing the thermoplastic resin is small. If the amount exceeds 5% by weight, the thermal stability becomes poor and the base layer becomes yellowish, which is not preferable.

In the present invention, polyethylene glycol is particularly preferred as the polyalkylene glycol, and has a molecular weight of 500 to 30,000, preferably 1,000 to 10,000.
A range of 000 may be sufficient in terms of color tone and the like. In addition, polyethylene glycol has a greater effect of promoting the generation of fine bubbles than other polyalkylene glycols.

In the present invention, when the polyester layer (A) contains a thermoplastic resin different from and incompatible with polyester, the apparent density due to the fine bubbles formed in the polyester layer (A) is 0. 0.5 g / cm ³ or more;
It is preferably less than 3 g / cm ³ , more preferably 0.6 g / c 3 from the viewpoint of film forming property and balance of each property.
m ³ or more and less than 1.2 g / cm ³ . When the apparent density is 1.3 g / cm ³ or more, the film may not be able to impart cushioning properties, flexibility, and concealing properties,
May not be preferred. The cushioning property is a desirable property when used as receiving paper for a video printer, for example, because the thermal recording head has good touch properties and can clearly transfer an image. Of course, the feel when touching the hand is also an important factor. For this reason, it is desired that the cushion rate be 10% or more.

On the other hand, if the apparent density is less than 0.5 g / cm ³ , the amount of the fine bubbles inside is too large, and the strength of the film is weakened, which may be unfavorable.

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. Further, the thickness of the polyester layer (B) to be laminated is preferably from 1 to 50 μm, and more preferably from 5 to 30 μm from the viewpoint of whiteness and concealability.

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.

The whiteness of the white polyester film of the present invention 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%
When the whiteness exceeds, it is necessary to add a large amount of particles and to form a large amount of voids, which may be unfavorable because the surface smoothness is impaired or the film strength is reduced.

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

The white polyester film of the present invention preferably has a color tone b value of 2 to -5, preferably 0 to -3, as determined by a color difference meter, 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 is obtained by laminating a polyester layer (B) on at least one surface of the above-mentioned polyester layer (A).
A three-layer structure in which the polyester layer (B) is laminated on both sides of the polyester layer (A) is desirable from the viewpoint of properties such as whiteness, concealing property, scratch resistance and practicality.

The white polyester film of the present invention may be used alone or, if desired, may be used by appropriately bonding it to paper or the like.

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

In a composite film forming apparatus having a main extruder (A) and a sub-extruder (B), a polyester resin chip,
The master chip of the white inorganic fine particles and the crosslinked resin are mixed, sufficiently vacuum-dried, and then supplied to the main extruder (A) 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. In particular, a finely pulverized product coated on the film surface is preferable because of excellent dispersibility.

To laminate the surface layer, a mixture of separately dried polyester resin chips and inorganic fine particles master chips is supplied to the sub-extruder (B), and the mixture of the extruder (B) is fed into the T-die composite die. The polymer is laminated and formed into a sheet shape so that the polymer comes to the surface layer of the polymer of the extruder (A).

The melted sheet is subjected to a surface temperature of 10
It is tightly cooled and solidified by static electricity on a drum cooled to 60 ° C. to produce an unstretched composite film. The unstretched composite film is guided to a roll group heated to 80 to 120 ° C, stretched 2 to 5 times in the longitudinal direction, and cooled by a roll group 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 stretched 90 to 14 times.
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 flatness and dimensional stability to the biaxially stretched film thus obtained, the biaxially stretched film is placed in a tenter for 150 minutes.
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.

[0053]

[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 Co., Ltd.)
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) Apparent density The value at 22 ° C. was determined by a density gradient tube prepared using carbon tetrachloride-n-heptane.

(7) Cushion rate (%) Dial gauge No. manufactured by Mitoyo Seisakusho Co., Ltd. 2109-1
0, and load 50g and 50
It was determined from the thickness d ₅₀ , d _{500 of} each film when 0 g was applied by the following equation.

[0061] cushion factor _{(%) = (d 50 -d} 500)
/ D ₅₀ × 100 (8) Content of cross-linked 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.

(9) Scratch resistance A film obtained by slitting a 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 25 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 where powder is not attached at all 5 points where powder is slightly attached 3 points where powder is attached in large quantities 1 point 4 points between each point, 2 points, and points higher than 4 points Was determined to have good scratch resistance.

[0064]

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.

Examples 1 and 2 On a polyethylene terephthalate chip, 16% by weight of anatase type titanium oxide having an average particle diameter of 0.33 μm as white inorganic fine particles and styrene having an average particle diameter of 0.21 μm as a crosslinked resin were added. The raw materials to which 2.5% by weight of the divinylbenzene cross-linked copolymer had been added were mixed and dried under vacuum at 180 ° C. for 3 hours.
It was melted at 85 ° C. and introduced into a T-die composite die.

Then, 14% by weight of anatase type titanium oxide having an average particle size of 0.23 μm and a fluorescent whitening agent “OB-1” were added to the polyethylene terephthalate chip.
The raw material to which 0.05% by weight (manufactured by Eastman Co.) was added was vacuum-dried at 180 ° C., then supplied to an extruder B, melted at 285 ° C. by a conventional method, and surface layered in a T-die composite die (Example). 1) and both surface layers (Example 2), and the melt sheet was tightly cooled and solidified by an electrostatic charge method on a cooling drum maintained at a surface temperature of 25 ° C. Subsequently, the unstretched film was stretched 3.2 times in the longitudinal direction using a roll group heated to 98 ° C. in a longitudinal direction, and cooled by a roll group at 25 ° C.

Further, the stretched film was guided to a tenter and
2. in a direction perpendicular to the longitudinal direction in an atmosphere heated to 25 ° C.
It was stretched 4 times. Thereafter, the film was heat-set at 220 ° C. in a tenter, uniformly cooled, and wound up to obtain a white polyester film having a base layer portion of 55 μm and a surface layer portion of 10 μm each.

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

Example 3 Based on Example 2, except that 18% by weight of barium sulfate having an average particle diameter of 0.6 μm was added as the raw white inorganic fine particles to be supplied to the extruder A of Example 2, A film was obtained in the same manner as in Example 2. As shown in Table 1, the properties of the white polyester film were excellent in each property.

Example 4 Based on Example 2, as a crosslinked resin as a raw material to be supplied to the extruder A of Example 2, a coating material having the following composition was obtained before the completion of orientation in a polyethylene terephthalate film forming process. Using a 50 μm-thick polyester film “Lumirror” (manufactured by Toray Industries, Inc.) having a final coating thickness of 0.4 μm and applied to both sides, the film is subjected to a cutting machine to finely pulverize fragments into 10 mm square or less. Then, a film was obtained in the same manner as in Example 2, except that 45% by weight of the pelletized product was added to make the actual content of the crosslinked resin 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. Then, while drying the paint, the horizontal method 12
Stretched 3.4 times at 5 ° C, and then 3% under 220 ° C atmosphere
Heat treatment was applied while relaxing.

[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) 5 Based on Example 4, a film was prepared in the same manner as in Example 4 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 4. 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 6 and Example 7 Based on Example 4, the raw material to be supplied to the extruder A of Example 4 was obtained by removing the crosslinked resin. 5% by weight of calcium carbonate fine particles having an average particle size of 1.0 μm as white inorganic fine particles, and a polyethylene terephthalate chip 10
Poly-4 as an incompatible thermoplastic resin with respect to 0 parts by weight
-Methylpentene-1 (TPX manufactured by Mitsui Petrochemical Co., Ltd.)
D820) was used in the same manner as in Example 4 except that 5 parts by weight (Example 6) and 10 parts by weight (Example 7) and 1 part by weight of polyethylene glycol having a molecular weight of 4000 as a dispersant were used. A film was obtained by the procedure. As shown in Table 1, the properties of the white polyester film were excellent in each property. The apparent density of Example 6 was 0.98 g / cm ³ and the cushion rate was 12.6%. The apparent density of Example 7 was 0.71 g / cm ³ and the cushion rate was 24.5%. Also in the examples, a light-weight and highly cushioning material can be obtained, and such a white polyester film can be suitably used particularly in image formation using a thermal head.

Comparative Example 1 Based on Example 2, the raw material supplied to the extruder A of Example 2 was a system excluding the crosslinked resin, and the white inorganic fine particles of the raw material supplied to the extruder B of Example 2 A film was obtained in the same manner as in Example 2, except that 16% by weight of calcium carbonate having an average particle diameter of 1.2 μm was added. The properties of the white polyester film are as shown in Table 1,
The gloss was low and the scratch resistance was poor.

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

[0075]

[Table 1]

[0076]

The white polyester film of the present invention is
A cross-linked resin was dispersed and mixed in one layer of a composite layer composed of a layer containing a polyester resin and white inorganic fine particles, so that light scattering effectively acted to obtain a high white color. When used for photographic paper or thermal transfer receiving paper based on the image quality, 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 clear white property can be exhibited. In addition, a particularly clear image can be provided.

The white polyester film of the present invention has the above-mentioned excellent properties, and thus 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, bar code printer receiving paper, ink jet 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 a surface, especially for a color printing substrate.

Claims (15)

[Claims] 1. A polyester layer comprising a polyester resin, white inorganic fine particles and a crosslinked resin as main components, and a polyester layer comprising a polyester resin and white inorganic fine particles as main components on at least one surface of a surface layer thereof. A white polyester film obtained by laminating (B). 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 in combination with a crosslinking agent. 5. The laminated thickness of the polyester layer (B) is 1 to 5.
The white polyester film according to claim 1, wherein the white polyester film is in a range of 50 μm. 6. The white polyester film according to claim 1, wherein the content of the white inorganic fine particles has a relationship of polyester layer (A)> polyester layer (B). 7. Polyester layer (A) and / or (B)
Contains a fluorescent whitening agent, the white polyester film according to any one of claims 1 to 6. 8. The white color according to claim 1, wherein the polyester layer (A) contains a thermoplastic resin different from polyester and incompatible with the polyester. Polyester film. 9. The content of the thermoplastic resin is from 1 to 30% by weight.
, And at least one dispersant is 0.1
The white polyester film according to claim 8, wherein the white polyester film is contained in an amount of from 5 to 5% by weight and the film is biaxially stretched. 10. The white polyester film according to claim 8, wherein the thermoplastic resin is a polyolefin resin. 11. An optical density obtained from the polyester layer (B) side of 0.5 or more and 2 or less, and a whiteness of 70% or more and 1 or more.
2. The method according to claim 1, wherein the amount is 20% or less.
0. The white polyester film according to any one of 0. 12. The white polyester according to claim 1, wherein the color tone b value obtained from the polyester layer (B) side by a color difference meter is in the range of 2 to -5. the film. 13. The white polyester film according to claim 1, wherein the glossiness measured from the polyester layer (B) side is 40% or more. 14. A three-layer laminated structure, wherein the base layer is a polyester layer (A) and both surface layers are polyester layers (B).
The white polyester film according to any one of claims 1 to 13, wherein 15. 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.