JP2000135766A - White laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white laminated polyester film excellent in printing properties and folding wrinkle resistance. SOLUTION: In a white laminated polyester film constituted by laminating a white polyester layer (A) to at least the single surface of a white polyester layer (B), the white polyester layers (A), (B) are fine void containing layers containing a thermoplastic resin incompatible with polyester and the void content and the number of voids of the layers (A), (B) satisfy formulae: VB=5-50(%), 0.1<=VA/VB<=0.9, nB=8×103-3×105/mm2 and 0.1<=nA/nB<=0.9 [wherein VA and VB are void contents of the white polyester layers (A), (B) and nA and nB are the numbers of voids of the white polyester layers (A), (B)].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a white laminated polyester film. More specifically, the present invention relates to a white laminated polyester film which is excellent in folding wrinkle resistance and is suitable as a receiving sheet substrate for various printing records, particularly, thermal transfer recording.

[0002]

2. Description of the Related Art As one of recording methods in the hard copy technology, attention has been paid to thermal transfer recording which is non-impact, easy to operate and maintain, can be reduced in cost and can be reduced in size.

As such a receiving sheet substrate for thermal transfer recording, a white polyester containing a resin incompatible with the polyester in the polyester and containing fine voids (voids) formed by stretching has conventionally been used. Film has been applied.

[0004] The white polyester film is applied because it contains voids so that heat is efficiently transmitted to a printed portion by a heat insulating effect against heating of a thermal head during printing by a thermal transfer recording method, or For example, the adhesiveness between the thermal head and the printing surface is high due to the development of the cushioning property.

Further, in recent years, in order to obtain higher gradation and higher definition images, improvements such as miniaturization of thermal heads and fine control of applied energy for heating have been advanced.

Various proposals have been made for a white polyester film as a base material in order to improve such an apparatus. For example, a layered structure in which the surface layer is a layer mainly composed of polyester or a layer containing inorganic fine particles is used. Specific examples of such a white polyester film include JP-B-7-37098 and JP-A-5-37098.
JP-A-329969, JP-A-6-238787 and the like are disclosed.

[0007]

However, when the above-described white laminated polyester film is used in the improved apparatus, the following problems still remain.

That is, since the surface layer is mainly composed of polyester or a layer containing inorganic fine particles, the surface is highly smooth and the adhesion to the miniaturized thermal head is improved. In high-definition printing and the like, there is a problem in that the applied energy in a minute area becomes insufficient and the printability deteriorates. Further, there is a problem such as "bent wrinkles" that the surface is easily wrinkled due to bending during handling.

The present invention solves the above-mentioned problems, and is particularly excellent in printability by a thermal transfer recording system due to the heat insulating effect in a minute area and the improvement in adhesion to a thermal head, and also excellent in folding wrinkle resistance. It is an object to provide a white laminated polyester film.

[0010]

The white laminated polyester film of the present invention which achieves the above object is a white laminated polyester film obtained by laminating a white polyester layer (A) on at least one side of a white polyester layer (B). The white polyester layers (A) and (B) are fine bubble (void) -containing layers containing a thermoplastic resin incompatible with polyester, and the white polyester layers (A) and (B) A white laminated polyester film having a void content and a void number satisfying the following formulas (1) to (4).

(1) V _B = 5 to 50 (%) (2) 0.1 ≦ V _A / V _B ≦ 0.9 (3) n _B = 8 × 10 ^{3 to} 3 × 10 ⁵ pieces / mm ² (4) 0.1 ≦ n _A / n _B ≦ 0.9 (where V _A and V _B respectively represent the void content of the white polyester layers (A) and (B), and n _A and n _B are ,
Each represents the number of voids in the white polyester layers (A) and (B). )

[0012]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a polyester is a polymer obtained by condensation polymerization of a diol and a dicarboxylic acid, and dicarboxylic acids are terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid. Acids, adipic acid, sebacic acid and the like, and diols are ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexanedimethanol and the like. Specific examples include polyethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexylene dimethylene terephthalate, and polyethylene-terephthalate.
2,6-naphthalenedicarboxylate (polyethylene naphthalate) and the like can be used.

Of course, these polyesters may be either homopolyesters or copolyesters. Examples of the copolymerization component include diol components such as diethylene glycol, neopentyl glycol and polyalkylene glycol, adipic acid and sebacic acid. Phthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid,
A dicarboxylic acid component such as 5-sodium sulfoisophthalic acid can be used.

[0014] The polyester may contain, if necessary, appropriate additives in an amount which does not impair the effects of the present invention.
For example, heat stabilizers, oxidation stabilizers, ultraviolet absorbers, weather stabilizers, organic lubricants, organic fine particles, fillers, antistatic agents, nucleating agents, dyes, dispersants, coupling agents, etc. are compounded. You may.

As the polyester used in the present invention, polyethylene terephthalate and polyethylene naphthalate are preferred because they are excellent in water resistance, durability, chemical resistance and the like.

The white laminated polyester film of the present invention is a white laminated polyester film obtained by laminating a white polyester layer (A) on at least one surface of a white polyester layer (B), wherein the white polyester layer (A)
(B) is a layer containing fine bubbles (voids) containing a thermoplastic resin incompatible with the polyester, and the void content and the number of voids of the layers (A) and (B) are represented by the following formula (1). ) To (4) must be satisfied.

[0017] _{(1) V B = 5~50 (} %) (2) 0.1 ≦ V A / V B ≦ 0.9 (3) n B = 8 × 10 3 ~3 × 10 5 cells / mm ² (4) 0.1 ≦ n _A / n _B ≦ 0.9 Here, V _A and V _B are the void contents of the white polyester layers (A) and (B), respectively, and n _A and n _B are: Each represents the number of voids in the white polyester layers (A) and (B).

In the present invention, the void content of the white polyester layer (B) is 5 to 50%, preferably 10 to 45%, and more preferably 15 to 40%. When the void content is less than 5%, the whiteness and the concealing property (optical density) are significantly inferior, and the cushioning property of the whole white laminated polyester film is extremely reduced, so that the adhesion to the thermal head is reduced or the thermal head is reduced. Insufficiency of the heat insulating effect against the heating of the ink tends to lower the printability, which is not preferable. On the other hand, if the void content is greater than 50%, the strength of the entire film is reduced, the film is easily broken during film formation, the surface is easily deformed upon contact with the thermal head, and the dots are crushed. Problem may occur.

In the present invention, the number of voids in the white polyester layer (B) is from 8 × 10 ^{3 to} 3 × 10 ⁵ / m.
m ² , preferably 1 × 10 ⁴ to 2 × 10 ⁵ / mm ² , more preferably 2 × 10 ⁴ to 1 × 10 ⁵ / mm ² .

When the number of voids is less than 8 × 10 ³ / mm ^{2, the} individual voids are very large even if the above void content is satisfied, and the whiteness and optical density are insufficient and white Since the whiteness of the film is inferior, the sharpness of the printed image tends to decrease. In addition, due to the non-uniform cushioning and heat insulating effect of the film surface, high-speed printing and high-definition printing may cause a missing portion around the dot, and sometimes the printed image may have "missing" or "unevenness". Also, the printability may be poor. On the other hand, the number of voids is 3 ×
When the number is more than 10 ⁵ / mm ² , the strength of the whole film is reduced and the film tends to be broken during the film formation, or the surface is deformed at the time of contact with the thermal head, and the dots are likely to be crushed. .

Further, in the present invention, the ratio of the void content of the white polyester layer (A) to the white polyester layer (B) (V _A / V _B ) and the ratio of the number of voids (n _A / n _B ) are 0. 0.1 to 0.9, preferably 0.15 to 0.8, more preferably 0.2 to 0.75. If the ratio is less than 0.1, the heat insulating effect of heating the thermal head is small, the printability is reduced, and the wrinkle resistance tends to be poor. If the ratio is greater than 0.9, the strength of the entire film is reduced, and the film tends to be broken during film formation, or the surface is deformed upon contact with the thermal head, and the dots are crushed and the printability is reduced. Problems are likely to occur. In addition, the effect of the laminated structure is small, and as a result, the manufacturing cost tends to be increased due to the laminated structure.

In the present invention, the white polyester layers (A) and (B) contain a thermoplastic resin which is incompatible with the polyester in a layer made of polyester, and is further finely formed in the layer by stretching during film formation. It is a layer that generates white bubbles (voids) and scatters light by these voids to make it white and opaque and also to impart cushioning properties.

Therefore, the voids in the present invention are basically formed by using the thermoplastic resin contained in the polyester as a core, and contribute to white opacity and to impart cushioning properties. Specifically, the average value of the cross-sectional area of the voids is preferably in the range of 0.5 to 25 μm ² , more preferably 1 to 20 μm ² .

The term "thermoplastic resin incompatible with polyester" as used in the present invention refers to a thermoplastic resin other than polyester, and is measured by a method such as a differential scanning calorimeter (DSC). In a system in which a thermoplastic resin is melted, Tg corresponding to the thermoplastic resin is observed in addition to the glass transition temperature (hereinafter abbreviated as Tg) corresponding to the polyester.

A thermoplastic resin that is incompatible with the polyester has a great effect of dispersing in a particle form in the polyester and forming voids in the polyester film by stretching.

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 this point, among the thermoplastic resins, olefins such as polyethylene, polypropylene, polybutene, and polymethylpentene, polystyrene, polyphenylene sulfide, and acryl are preferable. These thermoplastic resins may be a homopolymer or a copolymer. Among these, olefins having a small critical surface tension are preferable, and polypropylene and polymethylpentene are more 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 fine bubbles are easily formed during stretching.

Further, the thermoplastic resin has an olefin polymer or copolymer having a polar group such as a carboxyl group or an epoxy group or a functional group reactive with the polyester;
When a polyalkylene glycol or the like is used in combination, the dispersion diameter of the thermoplastic resin is reduced, and thus the voids generated by stretching can be further refined to improve the film-forming stability, and the whiteness and the optical density are further improved. Is preferred.

In the present invention, the contents W _{A and} W _B of the thermoplastic resin incompatible with the polyester in the white polyester layers (A) and (B) are not particularly limited. )), 1 to 35
%, More preferably from 2 to 30% by weight, and most preferably from 3 to 25% by weight.

Further, the content W _A white polyester layer (A) is 0.03 to 0.8 is preferable as the ratio (W _A / W _B) to the content W _B of the white polyester layer (B), 0 0.05 to 0.75 is more preferable. When the content of the white polyester layers (A) and (B) is less than the above range, the cushioning property and the heat insulating effect are small, and it tends to be difficult to improve the properties of the film such as whiteness and optical density. On the other hand, when the amount is larger than the above range, the smoothness (glossiness) of the film surface is reduced, which makes the film unsuitable as a receiving sheet substrate for thermal transfer or the like, and may cause inconvenience such as film tearing at the time of stretching. .

Further, the white laminated polyester film of the present invention needs to have a structure in which the white polyester layer (B) is laminated on at least one surface of the white polyester layer (A). That is, fine voids are contained in each of the white polyester layers (A) and (B), and the void content and the number of voids satisfy the above formulas (1) to (4). ) Is excellent in smoothness (gloss), the white polyester layer (B) is a layer having more excellent cushioning properties, and the whole white laminated polyester film is excellent in the heat insulating effect against heating of the thermal head,
It is possible to satisfy all the necessary characteristics such as printability and fold wrinkle resistance.

The white laminated polyester film of the present invention is a white laminated polyester film obtained by laminating a white polyester layer (A) on at least one surface of a white polyester layer (B). The one in which the white polyester layer (A) is laminated to form a three-layer laminated structure is more desirable from the viewpoint of film forming stability and practical handling.

In the present invention, the thickness t _A of the white polyester layer (A) is from 0.01 to 0.01 as a ratio (t _A / t) to the total thickness t of the white laminated polyester film.
0.7, more preferably 0.02.
-0.6, more preferably 0.03-0.5.
If less than 0.01, whiteness, smoothness (gloss)
, And the film tends to be broken during film formation due to a decrease in film strength. On the other hand, when it is larger than 0.7, the cushioning property and the heat insulating effect are lowered, and the printability is sometimes deteriorated.

In the present invention, the white polyester layer (A) is laminated on both sides of the white polyester layer (B).
In the case of a layered configuration, the sum of the layer thicknesses on both sides is t
It is preferable that the ratio is _A, and the ratio to the total thickness t is within the above range.

Further, in the present invention, the total thickness of the white laminated polyester film is not particularly limited, but is usually in the range of about 10 to 500 μm, preferably about 20 to 300 μm in terms of practical use as a base material of the receiving sheet. Is preferred because of its excellent handleability.

In the present invention, it is preferable to add inorganic fine particles to at least one of the white polyester layers (A) and (B) in order to improve the whiteness, optical density and the like of the white laminated polyester film. As inorganic fine particles, titanium oxide, zinc oxide, zinc carbonate, calcium carbonate, magnesium carbonate, magnesium oxide, silica, talc, kaolin, lithium fluoride, calcium fluoride, barium sulfate, zinc sulfide, alumina, calcium phosphate, mica, etc. Can be used. They are,
A single type or a combination of two or more types may be used. In the present invention, among these particles, in particular, from the viewpoint of overall effect such as whiteness and optical density, titanium oxide, calcium carbonate,
The use of barium sulfate is more preferred, and titanium oxide is particularly preferred. Further, the inorganic fine particles may be in a form such as porous or hollow porous, and furthermore, within a range where the effect of the present invention is not impaired, in order to improve dispersibility in resin, further surface treatment. May be applied.

The average particle diameter of the inorganic fine particles used in the present invention is preferably 0.05 to 3 μm, and 0.07 to 3 μm.
Those having a range of from 1 to 1 μm are more preferable. If the average particle diameter is outside the above range, uniform dispersion becomes difficult, or the smoothness of the film surface is deteriorated, and further, whiteness and glossiness may be reduced due to these factors. Absent.

The amount of the inorganic fine particles is not particularly limited, but is preferably 1 to 30% by weight, more preferably 3 to 25% by weight, and most preferably 5 to 20% by weight. . If the amount is less than the above range, it is difficult to improve the properties of the film, such as whiteness, optical density, and the like. It is not preferable because inconveniences such as generation may occur.

Here, even when the above-mentioned inorganic fine particles are added, voids can be formed in the same manner as in the case of the incompatible thermoplastic resin. However, such voids are usually smaller than those made of the thermoplastic resin and contribute to white opacity, but do not significantly contribute to cushioning. In addition, when inorganic fine particles having a large average particle diameter, specifically, those having an average particle diameter of 0.5 to 3 μm are used, it may also contribute to cushioning. Therefore, the range the average value of the aforementioned cross-sectional area of the void created by the inorganic fine particles in the present invention, i.e. counted as voids being in 0.5 to 25 ^2, smaller than 0.5 [mu] m ² as a void It is uncountable.

In the present invention, the white laminated polyester film is provided with clearer and bluish whiteness (specifically, higher whiteness and smaller color tone b value) to give a high quality image. Therefore, it is desirable that at least one of the white polyester layers (A) and (B) contains a fluorescent whitening agent.

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. It is a compound that promotes whiteness and blueness index (color tone b value) without lowering the lightness of the substance. As optical brighteners, trade names "Ubitek" (Ciba Geigy),
"OB-1" (Eastman), "TBO" (Sumitomo Seika Co., Ltd.), "Kay Coal" (Nippon Soda Co., Ltd.), "Kayalite" (Nippon Kayaku Co., Ltd.), "Leukopua" EG
M (Client Japan Co., Ltd.) or the like can be used. The optical brightener is not particularly limited, and may be used alone or in combination of two or more.
In the present invention, it is desirable to select a resin which has particularly excellent heat resistance, has good compatibility with the above-mentioned polyester, can be uniformly dispersed, has little coloring, and does not adversely affect the resin.

The content of the fluorescent whitening agent in the white polyester layer (A) is preferably 0.005 to 1% by weight,
Those in the range of 0.01 to 0.5% by weight are more preferred. If the content is less than the above range, it is difficult to obtain a sufficient whitening effect, and if the content exceeds the above range, a decrease in uniform dispersibility,
It is not preferable because a reduction in the whitening effect called “density quenching” or a reduction in whiteness due to coloring is easily caused.

In the present invention, in order to improve whiteness, color tone b value, optical density, etc., at least one of the white polyester layers (A) and (B) has inorganic fine particles and / or fluorescent whitening. It is preferable that the agent contains an inorganic fine particle and a fluorescent whitening agent in at least one layer in order to further increase the whiteness and the color tone b value. Further, when inorganic fine particles and a fluorescent whitening agent are added to each of the white polyester layers (A) and (B), the content of the fluorescent whitening agent is set to be higher than that of the white polyester layer (B). A) is more preferable in terms of effect.

In the present invention, each of the white polyester layer (A) and the white polyester layer (B) may be the same polyester composition or different polyester compositions. In particular, when a different polyester composition, for example, the white polyester layer (B) is made of a homopolyester and the white polyester layer (A) is made of a copolyester, it is more preferable because characteristics such as easy adhesion can be obtained. Further, it is more preferable that the polyester used for the white polyester layer (A) is polyethylene naphthalate and the polyester used for the white polyester layer (B) is polyethylene terephthalate, because the effects of improving weather resistance and rigidity can be obtained.

In the present invention, as a method of laminating the white polyester layer (A) and the white polyester layer (B), a method of compounding by coextrusion during melt film formation,
Alternatively, a method of laminating each film separately and then laminating may be used, but the former method is more preferable in terms of cost and the like.

The white laminated polyester film of the present invention has a whiteness of 7 determined from the white polyester layer (A) side.
Those having a content of 0% or more, more preferably 75% or more, and even 85% or more are preferable because they exhibit very beautiful whiteness without dullness. Further, those having a color tone b value determined from the white polyester layer (A) side of 0 or less, more preferably -0.5 or less, and most preferably -1 or less have a bluish color,
It is preferable because it shows high-quality and excellent whiteness.

The optical density of the white laminated polyester film of the present invention is 0.5
It is preferably from 2.0 to 2.0, and more preferably from 0.7 to 1.8. When the optical density is less than 0.5,
Since the film has a small concealing property, the back side is seen through, which is not preferable when used as a receiving sheet substrate.

In order for the optical density to exceed 2.0, a large amount of thermoplastic resin and inorganic fine particles which are incompatible with polyester must be contained, and as a result, the strength of the film may be weakened. There is not preferred.

Further, in the white laminated polyester film of the present invention, the glossiness of the surface determined from the white polyester layer (A) side is preferably 15% or more, more preferably 20% or more, which is excellent in smoothness, and the receiving sheet. When used as a base material, not only can a high-definition image be formed, but also a higher-grade image can be given.

Next, some examples of the method for producing the white laminated polyester film of the present invention will be described.
It is not limited only to such an example.

Regarding the method for producing a white laminated polyester film, in a composite film forming apparatus having an extruder (A) and an extruder (B), a polyester chip and a master chip of a thermoplastic resin incompatible with polyester are used. ,
After the content W _B of the incompatible thermoplastic resin is mixed so as to be 1 to 35 wt%, it was thoroughly dried under vacuum, 270-3
Feed to extruder (B) heated to 00 ° C. Further, since the white polyester layer (A) is laminated, a polyester chip and a master chip of a thermoplastic resin incompatible with the polyester are used, and a content W of the incompatible thermoplastic resin is used.
Supply _{what A} is the mixing ratio (W _A / W _B) as 0.03 to 0.8 and so as to the content W _B of the white polyester layer (B), and thoroughly dried under vacuum to the extruder (A) Then, the polymer of the extruder (A) was laminated in the T-die composite die so as to come to the surface layer (one surface) or both surface layers (both surfaces) of the polymer of the extruder (B), formed into a sheet shape, and melted. Obtain a laminated sheet.

The melted laminated sheet was subjected to a surface temperature of 1
On a drum cooled to 0 to 60 ° C., the film is tightly cooled and solidified by static electricity to produce an unstretched laminated film. The unstretched laminated film is guided to a group of rolls heated to 80 to 120 ° C., and has a length of 2 to 2
The film is stretched 5 times and cooled with a group of rolls at 20 to 30 ° C.

Subsequently, the laminated film stretched in the longitudinal direction was guided to a tenter while holding both ends of the laminated film with clips, and 90 to 1
The film is horizontally stretched in a direction perpendicular to the longitudinal direction in an atmosphere heated to 40 ° C.

The stretching ratio is 2 to 5 times in each of the vertical and horizontal 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 and optical density of the obtained film become 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, 150
After heat-setting at ２３０230 ° C., the mixture is gradually cooled, cooled to room temperature, and wound up to obtain the white laminated polyester film of the present invention. At this time, the thickness t _{A of} the white polyester layer (A) is 0.01 to 0.01 as a ratio (t _A / t) to the total thickness t of the white laminated polyester film.
It is preferably 0.7.

The white laminated polyester film thus obtained has excellent cushioning properties when used as a receiving sheet substrate.
It is suitable as a substrate for various printing records such as offset printing, and is particularly suitable for use as a receiving sheet substrate for thermal transfer recording due to its excellent heat insulating effect against heating of a thermal head and excellent folding wrinkle resistance.

[0056]

[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) Void Content and Number of Voids Transmission Electron Microscope HU-12 (Hitachi, Ltd.)
The cross section of each of the white polyester layers (A) and (B) was obtained by observing the cross section at a magnification of 500 to 50,000 times. That is, a void portion of a cross-sectional photograph in which a total of 100 or more voids are photographed is marked, and the void portion is marked with a high-definition image analysis processing device PIAS-IV.
Image processing is performed using (manufactured by Pierce Co., Ltd.), and the total void area and the total number of voids in the measurement visual field of the white polyester layers (A) and (B) are calculated. I asked.

[0058] However, the calculation of the void content and the number of voids were performed at a different arbitrary position for a total of five measurements, and the average value was calculated. Further, when two or more adjacent voids are connected to each other with respect to the voids in the measurement visual field, the calculation is performed as one void.

(2) Average Particle Size of Inorganic Fine Particles Transmission Electron Microscope HU-12 (Hitachi, Ltd.)
The cross section of the white polyester layer (A) or the white polyester layer (B) was obtained from a cross-sectional photograph obtained by observing the cross section at 3,000 to 200,000 times. That is, the particle portion of the cross-sectional photograph is marked, and the particle portion is marked with a high-definition image analysis processor PIAS-IV (Pierce Co., Ltd.)
Was used to perform image processing, and the average diameter when a total of 100 particles in the measurement visual field were converted into a perfect circle was calculated, which was defined as the average particle diameter of the inorganic fine particles.

(3) Whiteness According to JIS L-1015, U white manufactured by Shimadzu Corporation
It measured using V-260. Wavelength 450nm and 5
Assuming that the reflectance at 50 nm is B% and G%, respectively.
Whiteness is represented by the following equation.

Whiteness (%) = 4B-3G (4) Concealment It was determined by optical density (OD) and measured by a transmission method using an optical densitometer TR927 (manufactured by Macbeth). The greater the measured value, the higher the concealment property.

(5) Gloss Digital gonio-gloss meter UGV-5B (Suga Test Instruments Co., Ltd.)
Was measured according to JISZ-8741. The measurement conditions were an incident angle of 60 ° and a light receiving angle of 60 °.

(6) Folding wrinkle resistance The white laminated polyester film of the present invention is
A stainless steel guide pin (outer diameter: 4.5 mm, 8 m
In m), running conditions were as follows: after winding at a speed of 1 m / min and an output side tension of 50 g, the film was rewound and the surface state was visually observed to evaluate the following three grades.以上 The above was judged to be good.

○: No wrinkles on the surface.

Δ: wrinkles are partially present.

×: There are countless wrinkles.

(7) Printability Judgment was made from the shape of the print dots. First, the following receiving layer forming coating solution was coated on the white polyester layer (A) side of the white laminated polyester film of the present invention to a thickness of 0.1 μm after drying.
Apply with a gravure coater so that
After drying for a minute, a receiving sheet for thermal transfer recording was obtained.

"Receptive layer forming coating liquid" (A) Modified polyolefin: urethane modified polyethylene aqueous dispersion (urethane modified ratio = 20% by weight, emulsified by heating in aqueous ammonia solution to form an aqueous dispersion) B) Polyester: polyethylene glycol (hereinafter, referred to as “polyethylene glycol”)
Aqueous dispersion of copolyester (abbreviated as PEG) (terephthalic acid / isophthalic acid / 5-sodium sulfo-isophthalic acid / ethylene glycol / neopentyl glycol / PEG = 50/49/1/55 / 42.3 / 2.7)
(Molecular ratio), PEG molecular weight =
4000, PEG content = 30 parts by weight, Tg = 16
° C) (A) / (B) were mixed at a solid content weight ratio of 50/50, and diluted with water to a solid content concentration of 3%.

Next, as a color printer, "Professi
onal Color Point 2 "(manufactured by Seiko Electronic Industry Co., Ltd.),
Using a dedicated CH705 (yellow, magenta, cyan, manufactured by Seiko I Supply Co., Ltd.) as a thermal transfer ink ribbon, a test pattern of four gradations was printed on the above-mentioned receiving sheet. Then, the respective portions of the three colors of yellow, magenta, and cyan on the printed surface were observed at a magnification of 100 to 300 times using a reflection type optical microscope, and the following four-stage evaluation was performed on the dot shape.以上 The above was judged to be good.

A: For all three colors, the dot shape is circular and extremely good.

：: Good, although slight “missing” was observed in the dots.

Δ: Abnormalities such as “missing” and “crushing” are observed in the dots.

X: Many abnormalities such as "missing" and "crushing" are observed in the dots.

[0074]

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 (hereinafter abbreviated as PET) chip was provided with 5% by weight (W _A = 5% by weight) of polymethylpentene (hereinafter abbreviated as PMP) and a compatibilizer having a molecular weight of 4000. A raw material to which 1% by weight of polyethylene glycol (hereinafter abbreviated as PEG) is added is 18
After vacuum drying at 0 ° C. for 3 hours, it is supplied to an extruder (A),
It was melted at 285 ° C. by a conventional method and introduced into a T-die composite die.

[0076] On the other hand, the PET chip of PMP 15 wt% (W _B = 15 wt%), further 180 ° C. The material obtained by adding 1 wt% of PEG having a molecular weight of 4000 as a compatibilizer
After drying in vacuum for 3 hours, the mixture is supplied to the extruder (B), melted at 285 ° C. by a conventional method, and the white polyester layer (A) is laminated on both surface layers of the white polyester layer (B) in the T-die composite die. To obtain a laminated melt sheet. The laminated melt sheet was tightly cooled and solidified by an electrostatic method on a cooling drum maintained at a surface temperature of 25 ° C. to obtain an unstretched laminated film.
Subsequently, the unstretched laminated film was stretched 3.2 times in the longitudinal direction using a group of rolls heated to 98 ° C., and cooled by a group of rolls at 25 ° C. in a conventional manner. The stretched laminated film was guided to a tenter and stretched 3.4 times in a direction perpendicular to the longitudinal direction in an atmosphere heated to 125 ° C.

Thereafter, the film was heat-set at 220 ° C. in a tenter, uniformly cooled, and then wound up to form a white polyester layer (A).
The thickness t _A of 5 [mu] m, the thickness t _B of the white polyester layer (B) has a 90μm configuration, the total thickness t to obtain a white laminated polyester film of 100 [mu] m. Table 1 summarizes the raw material composition, lamination thickness, configuration, and the like of the white laminated polyester film.

The properties of the white laminated polyester film thus obtained are as shown in Table 2. That is, the cushioning property was developed and the flexibility was excellent, and the printing property was excellent and the folding wrinkle resistance was excellent.

[0079] Based on the examples 2, 3, 4, and 5 in Example 1, an extruder (A), modified as indicated amount W _A of PMP of the feed supply (B), the a W _B in Table 1 A white laminated polyester film was obtained in the same manner as in Example 1 except that the above procedure was performed.

The properties of this white laminated polyester film were excellent in each property as shown in Table 2, and in particular, Example 4 was extremely excellent in printability.

Examples 6 and 7 Based on Example 1, as shown in Table 1, the thickness t _A of the white polyester layer was 2 μm (Example 6) and 20 μm, respectively.
(Example 7) A white laminated polyester film was obtained in the same manner as in Example 1 except that the layers were laminated so that the total thickness t became 100 µm.

As shown in Table 2, the properties of this white laminated polyester film were excellent in each property.

Example 8 As shown in Table 1, the raw material supplied to the extruder (A) of Example 1 was further added with 7% by weight of anatase type titanium oxide fine particles having an average particle diameter of 0.3 μm, and a fluorescent brightener. "OB-1"
A white laminated polyester film was obtained in the same manner as in Example 1 except that 0.12% by weight (manufactured by Eastman) was added.

As shown in Table 2, the properties of this white laminated polyester film were excellent in each property, and in particular, the film was high in whiteness and concealing property, and was full of high-grade feeling.

Comparative Example 1 As shown in Table 1, the extruders (A) and (B) of Example 1
Of the feed supplied, the amount of PMP W _A, respectively W _B 20 wt%, except that the 5 wt%, to obtain a white laminated polyester film in Example 1 and the same approach.

The properties of this white laminated polyester film were as shown in Table 2, and were particularly poor in printability.

[0087] As shown in Comparative Example 2 in Table 1, among the raw material supplied to the extruder (A) of Example 1, except that a 13 wt% the amount W _A of the PMP, Example 1 and the same approach Thus, a white laminated polyester film was obtained.

As shown in Table 2, the properties of this white laminated polyester film were poor in printability.

[0089] As shown in Comparative Example 3 in Table 1, among the raw material supplied to the extruder (B) of Example 1, except that a 0.5 wt% addition amount W _B of the PMP Example 1 A white laminated polyester film was obtained in the same manner.

As shown in Table 2, the characteristics of this white laminated polyester film were inferior to each characteristic.

Comparative Example 4 As a raw material supplied to the extruder (A) of Example 1, as shown in Table 1, only 14% by weight of anatase-type titanium oxide fine particles having an average particle diameter of 0.3 μm were added to a PET chip. A white laminated polyester film was obtained in the same manner as in Example 1 except that the above-mentioned product was used.

This white laminated polyester film was as shown in Table 2 and was particularly poor in fold wrinkle resistance.

[0093] As shown in Comparative Example 5 in Table 1, among the raw material supplied to the extruder (B) of Example 1, the same manner as in Example 1 except that the addition amount W _B of PMP and 40% by weight However, film tearing occurred frequently and a white laminated polyester film could not be obtained.

[0094]

[Table 1]

[Table 2]

[0095]

According to the white laminated polyester film of the present invention, not only excellent printability but also excellent folding wrinkle resistance, which is a practical characteristic of the receiving sheet, is provided.

The white laminated polyester film of the present invention has the above excellent properties,
It can be suitably used as a receiving sheet substrate used for various printing records such as ink jet and offset printing.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) B41M 5/38 B41M 5/26 101H F-term (Reference) 2H111 CA12 CA25 CA31 CA38 4F100 AA00A AA00B AA00C AK01A AK01B AK01C AK03A AK03AK08 AK41A AK41B AK41C AK42 AL05A AL05B AL05C BA02 BA03 BA06 BA16 BA26 CA13 CA30A CA30B CA30C DE01A DE01B DE01C DJ01A DJ01B DJ01C GB90 JA20A JA20C JB16A JB16B JB16C JK04 JL00 JL10Y00B10

Claims (5)

[Claims] 1. A white laminated polyester film having a white polyester layer (A) laminated on at least one surface of a white polyester layer (B), wherein the white polyester layers (A) and (B) are polyester A layer containing fine bubbles (voids) containing an incompatible thermoplastic resin, and the void content and the number of voids of the layers (A) and (B) satisfy the following formulas (1) to (4). A white laminated polyester film characterized by the following: _{(1) V B = 5~50 (} %) (2) 0.1 ≦ V A / V B ≦ 0.9 (3) n B = 8 × 10 3 ~3 × 10 5 cells / mm ² (4) 0.1 ≦ n _A / n _B ≦ 0.9 (where _VA and V _B represent the void content of the white polyester layers (A) and (B), respectively, and n _A and n _B are:
Each represents the number of voids in the white polyester layers (A) and (B). ) 2. The thickness t _{A of the} white polyester layer (A) is:
White laminated polyester film according to claim 1, characterized in that a 0.01 to 0.7 as a ratio (t _A / t) for all the thickness t of the white laminated polyester film. 3. The white laminated polyester film according to claim 1, wherein the thermoplastic resin incompatible with the polyester is a polyolefin. 4. The method according to claim 1, wherein at least one of the white polyester layers (A) and (B) contains inorganic fine particles and / or a fluorescent whitening agent.
A white laminated polyester film according to any one of the above. 5. A three-layer laminated structure wherein the core layer is a white polyester layer (B) and both surface layers are polyester layers (A). 2. The white laminated polyester film according to item 1.