JP2000062121A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film having excellent heat sealability, cushionability and whiteness degree. SOLUTION: The laminated polyester film is obtained by laminating a heat sealing layer on one surface of a layer containing a polyester and a thermoplastic resin non-compatible with the resin as main components and containing fine bubbles therein, and a polyester resin layer containing substantially no fine bubble therein on the other surface in such a manner that an apparent density of the entirety is 0.5-1.3 g/cm3.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a laminated polyester film. More specifically, the present invention relates to a laminated polyester film having a laminated structure and excellent in heat sealing property, cushioning property, whiteness and the like.

[0002]

2. Description of the Related Art Various laminated polyester films having a multilayer structure in which the film itself has a fine air bubble layer introduced between the layers have been proposed, and due to the excellent properties of the film, a label has been produced. It is widely used for various purposes such as posters, heat-sensitive recording paper, and sublimation heat-sensitive recording paper. Further, as a feature of the film, by having a fine bubble layer inside, the hardness of the film is reduced, soft feeling and flexibility similar to paper can be obtained, and further, low specific gravity can be achieved. Are known. Examples of such a laminated polyester film include, for example, JP-A-5-13884.
4, JP-A-5-138781, JP-A-5-138781.
Those disclosed in Japanese Patent Publication No. 194773 and the like are known. In these conventional laminated polyester films, for example, when the film is used by being laminated with other materials, a processing method such as pressure-bonding or heat-laminating is generally applied by coating an adhesive on the film surface. ,
There is also a potential environmental problem associated with the discharge of the organic solvent during processing, and a problem that paper powder is generated during processing due to an increase in the number of processing steps, which tends to cause process contamination and product defects.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and provides a laminated polyester film which retains a high degree of heat sealability and has excellent cushioning properties, whiteness and the like. With the goal.

[0004]

A laminated polyester film of the present invention which achieves this object is a layer containing fine bubbles inside, which is mainly composed of a polyester resin and a thermoplastic resin incompatible with the resin. The heat-sealing layer (B layer) is laminated on one surface of the (A layer), and the polyester resin layer (C layer) which does not substantially contain fine bubbles inside is laminated on the other surface, and the overall apparent density is Is 0.5 g / cm ³ or more 1.
It is a laminated polyester film characterized by being less than 3 g / cm ³ .

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester resin in the present invention is a polymer obtained by polycondensation from a diol component and a dicarboxylic acid component, and specifically, for example, polyethylene terephthalate, polyethylene naphthalate, polyethylene-p-oxy. Benzoate, poly-
1,4-cyclohexylene dimethylene terephthalate,
Polyethylene-2,6-naphthalenedicarboxylate or the like can be used. In the case of the present invention, polyethylene terephthalate and polyethylene naphthalate are particularly preferable, and polyethylene terephthalate is more preferable because it is excellent in water resistance, durability, chemical resistance, mechanical properties and the like.

Of course, these polyester resins are
It may be a homopolyester or a copolyester.

In addition, if necessary, in the polyester resin, appropriate additives such as a heat stabilizer, an oxidation stabilizer, an ultraviolet absorber, and a charge may be added within a range that does not impair the effects of the present invention. Inhibitors, dyes, dispersants, coupling agents and the like may be added.

In the present invention, the main component in the layer A means that the component is 50% by weight or more in the layer, preferably 60% by weight or more, more preferably 70% by weight or more.
It means that it is more than weight%.

In the present invention, the thermoplastic resin which is incompatible with the polyester resin is a thermoplastic resin other than polyester and is not compatible with polyester. Such a resin is used in a differential scanning calorimeter (DS).
It is a resin in which Tg corresponding to the thermoplastic resin is observed in addition to Tg corresponding to polyester in the measurement of the A layer by the method such as C). As the incompatible thermoplastic resin, for example, a polyolefin resin, a polystyrene resin, a fluorine resin, or the like can be used. The resin is
In polyester, it is dispersed in the form of particles, and it has a great effect of forming bubbles inside the polyester film by stretching.

The melting point of such a thermoplastic resin is preferably lower than that of polyester and higher than the temperature used for orienting the film support. From this viewpoint, the polyolefin resin is preferable among the thermoplastic resins. The polyolefin resin may be any as long as it can be added to polyester to form a film, and for example, low density polyethylene, high density polyethylene, polypropylene, polybutene, polymethylpentene, etc. are used. be able to.
Further, it is not necessarily limited to the homopolymer,
It may be a copolymer of these. Moreover, you may use together 2 or more types. 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 with polyester and has a high melting point, and it is easy to form fine bubbles during stretching.

The content of the thermoplastic resin in the layer A is preferably 1 to 30% by weight, more preferably 5 to 20% by weight. If the amount added is less than 1% by weight, the amount of fine bubbles generated is small, and it becomes difficult to reduce the apparent density of the laminated polyester film. 30% by weight
If it exceeds, the stretchability of the film may be deteriorated and the film forming property may be deteriorated.

In the present invention, it is preferable to add a dispersant together with the thermoplastic resin in order to make the dispersed state of the thermoplastic resin fine and promote the generation of uniform fine bubbles.

Examples of compounds having such an effect include polyalkylene glycol or copolymers thereof,
Ethylene oxide / propylene oxide copolymer,
Dodecylbenzenesulfonic acid sodium salt, glycerin monostearate, tetrabutylphosphonium paraaminobenzenesulfonate, etc. can be used. Among these, in the present invention, it is preferable to contain polyalkylene glycol or a copolymer thereof, and examples thereof include polyethylene glycol, polypropylene glycol, a copolymer of polyethylene glycol and propylene glycol, methoxy polyethylene glycol and the like.

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

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

In the present invention, the layer B constituting the present invention preferably has a melting point of 100 to 240 ° C. from the viewpoint of heat sealability, and when it is 120 to 220 ° C., it has not only self-heat adhesiveness but also other types. It is preferable because the heat adhesion to the material is good. Various resin compositions having heat sealability can be used for the B layer, but in the present invention, a resin composition composed of a polyester is used in view of the interlayer adhesion with the A layer, the sealing strength, and the like. Is particularly preferable. The B layer is laminated on one surface of the A layer described above.

The polyester resin used in the B layer is
As an acid component, an aromatic dicarboxylic acid component such as terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ether dicarboxylic acid, benzophenone dicarboxylic acid, and an aliphatic dicarboxylic acid such as sebacic acid or dimer acid A dicarboxylic acid component and its ester-forming derivative can be used, and as the glycol component,
One or more glycol components selected from aliphatic, alicyclic and aromatic diols having 10 or less carbon atoms can be used, and preferably 1,4-butanediol and ethylene glycol can be mentioned. For example, isophthalic acid-copolymerized polybutylene terephthalate and dimer acid-copolymerized polybutylene terephthalate can be preferably used. You may use together 2 or more types of the said component.

Particularly, in order to improve aging and heat sealability, the polyester resin contains 5 to 30 mol% of a long-chain aliphatic dicarboxylic acid unit having an alkylene group having 8 or more carbon atoms based on all acid components. It is preferable that the content of the 1,4-butanediol unit is 80 mol% or more based on all diol components. Examples of the long-chain aliphatic dicarboxylic acid having an alkylene group having 8 or more carbon atoms include sebacic acid, dodecanedioic acid, hexadecadioic acid, octadecadioic acid, nonadecadionic acid, eicosandioic acid, and heneicosandioic acid. , Docosandionate, tricosandionate, tetracosandionate, pentacosandionate, hexacosandionate, heptacosandionate, octacosandionate, nonacosandionate, triacontandionate and their ester-forming derivatives , Carbon number 8
The dimer acid obtained by dimerizing 25 to 25 unsaturated fatty acids, its hydrogenated product, and its ester-forming derivative can be used. Also, two or more of these may be used in combination. Particularly, those containing a dimer acid component are preferable because they are excellent in transparency and heat sealability.

The apparent density of the laminated polyester film of the present invention must be 0.5 g / cm ³ or more and less than 1.3 g / cm ³ . 0.6g is preferable due to film-forming properties.
/ Cm ³ or more and less than 1.2 g / cm ³ , and more preferably 0.7 g / cm ³ from the viewpoint of balance of each characteristic.
It is above 1.1 g / cm ³ .

When the apparent density is 1.3 g / cm ³ or more, the film may not be provided with cushioning property, flexibility and hiding property, which is not preferable.
The cushioning property is a desirable property, for example, when it is used as a receiving paper for a video printer by being attached to a paper, since the thermal recording head has a good touch and a clear image can be transferred. Of course, the feel when touching the hand is also an important factor. Therefore, it is desirable that the cushion rate is 10% or more. If the apparent density is less than 0.5 g / cm ³ , the amount of fine air bubbles inside is too large, and the strength of the film is weakened and the film becomes brittle, which is not preferable.

The laminated polyester film of the present invention has a heat seal strength between layers B of 300 g / 10 mm.
It is desirable that the width is equal to or larger than the width. Preferably 500 g / 1
The width is 0 mm or more, and more preferably 800 g / 10 mm or more in terms of durability of seal strength. When the heat seal strength is less than 300 g / 10 mm width,
After the heat-sealing process, when a force such as bending is repeatedly applied, it is easily peeled off, which is likely to cause a problem in practical use. Furthermore, it tends to be inferior in durability against heat, water and the like.

In the present invention, the thickness of the laminated polyester film is not particularly limited, but usually 10 to 5
It is preferable that it is in the range of about 00 μm, preferably about 20 to 300 μm, because it is excellent in handleability in terms of practical use as a substrate film, and whiteness and hiding properties. The thickness of the layer B to be laminated is preferably 1/500 to 1/3 of the total thickness, and more preferably 1/300 to 1/5 in terms of heat sealing strength. The thickness of the layer C to be laminated is preferably 1 to 50 μm, and 5 to 30 μm.
Those in the range of μm are more preferable in terms of whiteness, hiding power, mechanical properties and the like. In addition, in the B layer, if necessary, appropriate additives such as a heat resistance stabilizer, an oxidation resistance stabilizer, an ultraviolet absorber, an antistatic agent, and the like within a range that does not impair the effects of the present invention, Dyes, dispersants, plasticizers and the like may be added.

In the present invention, the C layer constituting the present invention may contain fine bubbles formed by containing inorganic fine particles. At this time, as the polyester resin, the above-mentioned ones can be directly applied,
The polyester resins of the A layer and the C layer may be the same or different. The C layer is laminated on the opposite side of the surface of the A layer on which the B layer is provided.

In the present invention, in order to further improve the whiteness, hiding power and the like of the laminated polyester film of the present invention, any one of A layer, B layer and C layer, and in some cases, a plurality of layers are made of inorganic material. It is desirable to include fine particles.

In the present invention, examples of the inorganic fine particles include 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. The inorganic fine particles may be of one type or a mixture of two or more types. In the present invention, it is more preferable to use inorganic fine particles such as calcium carbonate, titanium oxide and barium sulfate in view of whiteness and reflectance thereof. Further, the inorganic fine particles may be in a form such as porous or hollow porous, and may be further subjected to a surface treatment in order to improve dispersibility in the resin.

The average particle size of the inorganic fine particles is 0.05 to 5
μm is preferable, and one in the range of 0.1 to 3 μm is more preferable. 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 deteriorated, which is not preferable. The amount of the inorganic fine particles added is preferably 1 to 35% by weight, more preferably 5 to 20% by weight. If the addition amount is less than 1% by weight, it may be difficult to improve properties such as whiteness and hiding property of the film. On the contrary, if the addition amount is more than 35% by weight, the film may be broken at the time of stretching or post-processing such as printing. This is because inconveniences such as generation of powder may occur.

In the present invention, in addition to the fine particles added to each layer, fine particles precipitated by the reaction of the catalyst residue and the phosphorus compound in the polyester polycondensation reaction system may be used in combination. As the deposited 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 polyester is preferably 0.05 to 1 part by weight based on 100 parts by weight of the polyester.

In the present invention, in order to give the laminated polyester film of the present invention a high-quality image tone with more vivid whiteness and blue tint, any one of A layer, B layer and C layer may be provided. In some cases, it is desirable that a plurality of layers contain a fluorescent whitening agent.

In the present invention, the fluorescent whitening agent has a function of absorbing ultraviolet rays in sunlight or artificial light, converting the ultraviolet rays into violet to blue visible rays, and radiating the ultraviolet rays. It refers to a compound that can increase whiteness without reducing the brightness of a substance. Examples of such fluorescent whitening agents include trade names “Ubitech” (Ciba Geigy), “OB-1” (Eastman), and “TBO”.
(Sumitomo Seika Co., Ltd.), “K-Call” (Nippon Soda Co., Ltd.), “Kayalite” (Nippon Kayaku Co., Ltd.), “Leukopoor” EGM (Client Japan Co., Ltd.) and the like can be used. The optical brightener is not particularly limited, and may be used alone or in combination of two or more kinds depending on the case. In the present invention, particularly excellent heat resistance,
It is desirable to select a resin that has good compatibility with the above polyester, can be uniformly dispersed, has little coloring, and does not adversely affect the resin.

The fluorescent whitening agent is preferably used in combination with inorganic fine particles in its function. The content of the optical brightener in the layer is preferably 0.005 to 1% by weight,
More preferably, it is in the range of 0.5 wt%. If the content is less than 0.005% by weight, it is difficult to obtain a sufficient whitening effect, and if the content exceeds 1% by weight, uniform dispersibility and whiteness are likely to decrease.

The optical density of the laminated polyester film of the present invention is preferably 0.5 to 2. More preferably, it is 0.6 to 1.5. The optical density is 0.
If it is less than 5, the back side can be seen through because the hiding property of the film is small, which is generally not preferable. Also, the optical density is 2
In order to exceed, it is necessary to include a large amount of particles,
Therefore, the strength of the film may be weak, which is not preferable.

In the laminated polyester film of the present invention, it is preferable that the color tone b value determined by a color difference meter is in the range of 2 to -5, preferably 0 to -4 because the whiteness becomes clearer. When the color tone b value is larger than 2 or smaller than -5, the apparent whiteness is insufficient, and the sharpness of the color tone tends to decrease when color printing is performed.

The whiteness of the laminated polyester film of the present invention is preferably 70 to 120%. More preferably, it is 80 to 110%. When the whiteness is less than 70%, the whiteness is insufficient, and when the whiteness exceeds 120%, it is necessary to add a large amount of particles or to form a large amount of voids, and the surface smoothness is impaired or the film is not formed. A decrease in strength may occur.

In the laminated polyester film of the present invention, the surface of the C layer may be subjected to various surface treatments such as corona discharge treatment, plasma treatment and coating, if necessary, and further other materials such as paper. It is also preferable to use by laminating with.

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

In a composite film forming apparatus having a main extruder A and auxiliary extruders B and C, polyester resin chips and a master chip to which a dispersant was added during the polymerization reaction of polyester or after completion of the polymerization were mixed and sufficiently vacuumed. After drying, mix incompatible thermoplastic resin chips and
It is supplied to the main extruder A heated to 300 ° C.

On the other hand, in order to stack the C layer, the polyester resin chips are sufficiently vacuum dried, and then 270 to 30
It is supplied to the sub-extruder C heated to 0 ° C., and the respective melts are merged in the polymer channel between the extruder and the die or in the T-die multi-layer die, and the polymer of the extruder C is fed into the extruder A. Laminate so that it comes to the surface layer of the polymer. On the other hand, as a method of laminating the B layer, (1) if necessary, chips of a resin composition having a heat-sealing property that is dried are supplied to a sub-extruder B heated to a melting point or higher to extrude the melt. In the polymer flow path between the device and the die or in the T-die multi-layer die, the polymer of the extruder B is the surface layer of the polymer of the extruder A and the opposite side of the surface of the polymer of the extruder C laminated. Stack so that it comes to the surface.

(2) After the laminated sheets of the polymer of the extruder A and the extruder C are stretched in the longitudinal direction, an extruder having heat sealability is formed on the surface of the uniaxially stretched film opposite to the polymer of the extruder C. The polymer of B is extruded from a slit-shaped die and laminated.

(3) After the laminated sheets of the polymer of the extruder A and the extruder C are stretched in the longitudinal direction and the width direction, the heat-sealing property is applied to the surface of the biaxially stretched film opposite to the polymer of the extruder C. The polymer of the extruder B having the above is extruded from a slit-shaped die and laminated.

Methods such as the above can be preferably used.

Extruders A, C or extruders A, B,
The molten sheet of C is electrostatically adhered to a drum cooled to a surface temperature of 10 to 60 ° C. to be cooled and solidified to produce an unstretched composite film. 60-120 the unstretched composite film
It is led to a roll group heated to 0 ° C., stretched 2 to 5 times in the longitudinal direction, and cooled by a roll group at 20 to 30 ° C. After that, the polymer of the extruder B having heat sealability may be extruded from the slit-shaped die and laminated on the surface of the uniaxially stretched film opposite to the polymer of the extruder C.

Subsequently, the both ends of the film stretched in the longitudinal direction are guided to a tenter while holding both ends with clips, and 70 to 1
In the atmosphere heated to 40 ° C., transverse stretching is performed in the direction perpendicular to the longitudinal direction. After this, the extruder C for the biaxially stretched film
In some cases, the polymer of the extruder B having a heat-sealing property is extruded from the slit-shaped die and laminated on the opposite surface of the polymer.

The stretching ratio is 2 to 5 times for each of the length and width, and the area ratio (longitudinal stretching ratio × horizontal stretching ratio) is preferably 6 to 20 times. If the area ratio is less than 6 times, the whiteness and strength of the obtained film will be insufficient, and conversely, if it exceeds 20 times, tearing will tend to occur 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 ˜230 ° C., uniform slow cooling, cooling to room temperature and winding. In addition, after this heat setting, the polymer of the extruder B having heat sealing property may be extruded from the slit-shaped die and laminated on the surface of the biaxially stretched film opposite to the polymer of the extruder C.

[0045]

[Characteristic measuring method and evaluation method] The characteristic values of the present invention are
According to the following evaluation method and evaluation criteria.

(1) Average Particle Size of Particles The particles were dispersed in ethanol and measured using a centrifugal sedimentation type particle size distribution measuring device (CAPA4500 manufactured by Horiba Ltd.) to calculate the volume average diameter and to calculate the average particle diameter. And

(2) The surface color of the C layer surface of the color tone film is measured using a color difference meter ND-6B manufactured by Nippon Denshoku Industries Co., Ltd., and the obtained b value is used for judgment.

(3) Whiteness U manufactured by Shimadzu Corporation according to JIS-L-1015
When V-2600 is used and the reflectance on the C layer surface at wavelengths of 450 nm and 550 nm is B% and G%, respectively, whiteness (%) = 4B-3G.

(4) Hiding power An optical densitometer (TR manufactured by Macbeth Co., Ltd. was evaluated as an optical density.
C layer surface was measured using 927). The larger the measured value, the higher the hiding property.

(5) Apparent Density A value at 22 ° C. was obtained by using a density gradient tube prepared by using carbon tetrachloride and n-heptane.

(6) Cushion rate (%) Dial gauge No. manufactured by Mitoyo Seisakusho Co., Ltd. 2109-1
0, using a load of 50 g and 50 on the dial gauge retainer.
It was calculated by the following formula from the thicknesses d ₅₀ and d ₅₀₀ of the respective films when multiplied by 0 g.

[0052] cushion factor _{(%) = (d 50 -d} 500)
/ D ₅₀ × 100 (7) Heat-seal strength between films at 180 ° C., 3 Kg / mm ² , heating time 5
The sealing force when sealing in seconds was measured. The sealing force was measured with a sample width of 10 mm and a pulling speed of 200 m.
m / min.

(8) Stretchability Judgment was made as follows from the film forming state.

◯: A film which is free from longitudinal stretching breaks and transverse stretching tears and which can be obtained as a homogeneous film without stretching unevenness.

Δ: A film that causes transverse stretching breakage, but can be easily repaired, and a uniform film having no stretching unevenness can be sampled.

X: Breakage in transverse stretching or breakage in longitudinal stretching frequently occurs, and uneven stretching occurs even when stretching is possible.

[0057]

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

Example 1 To form a layer A, polyethylene terephthalate chips having an intrinsic viscosity of 0.65 were used, and poly-4-methylpentene-1 (Mitsui Petrochemical Industry ( Co., Ltd. TPX-D820) chips 6% by weight and polyethylene glycol having a molecular weight of 4000 as a dispersant 1% by weight are mixed and vacuum dried at 180 ° C.,
It was supplied to the extruder A, melted at 285 ° C. by a conventional method, and introduced into a T-die multi-layer die.

On the other hand, in order to form the C layer, the polyethylene terephthalate chips described above were coated with an average particle diameter of 0.2 μm.
7% by weight of anatase-type titanium oxide fine particles of m, and 0.15% by weight of a fluorescent whitening agent "OB-1" (manufactured by Eastman)
After vacuum drying the added raw material at 180 ° C., extruder C
And melted at 285 ° C. by a conventional method and introduced into the T-die multi-layer die and laminated on one surface of the A layer.

The melt sheet thus obtained was contact-cooled and solidified by an electrostatic charge method on a cooling drum whose surface temperature was kept at 25 ° C. Subsequently, the unstretched film was subjected to 3.2 in a longitudinal direction by using a group of rolls heated to 98 ° C. according to a conventional method.
The film was double-stretched and cooled with a roll group at 25 ° C. Further, the stretched film was introduced into a tenter and stretched 3.4 times in a direction perpendicular to the longitudinal direction in an atmosphere heated at 110 ° C. After that, heat setting was carried out at 210 ° C. in a tenter, followed by uniform slow cooling.

Next, in order to form the layer B, a polybutylene terephthalate / isophthalic acid copolymer resin (isophthalic acid 35 mol%, melting point 160 ° C., intrinsic viscosity 0.7)
8) was used as a heat-sealing composition, and the average particle size was 2.
After vacuum-drying a raw material added with 0.04% by weight of silicon dioxide fine particles of 5 μm, it is supplied to an extruder B, melted at 190 ° C. by a conventional method and extruded from a T-die die, and the other surface of the layer A of the above film. Layered on, slowly cooled and rolled up, C
A laminated polyester film having a structure of layers / A layer / B layer of 7 μm / 50 μm / 10 μm was obtained.

The characteristics of the film thus obtained are shown in Table 1.
The heat resistance was excellent, and the heat sealing property, whiteness, hiding property and cushioning property were all excellent.

Example 2 Based on Example 1, in the raw material of the layer B of Example 1, polybutylene terephthalate.
A film was obtained in the same manner as in Example 1 except that a hydrogenated dimer acid copolymer resin (hydrogenated dimer acid 17 mol%, melting point 190 ° C., intrinsic viscosity 0.8) was used and extruded at 230 ° C.
The properties of the laminated polyester film were excellent as shown in Table 1.

Examples 3, 4 and Comparative Examples 1, 2 Based on Example 1, the amount of poly-4-methylpentene-1 added in the raw material of the layer A of Example 1 was 2.5% by weight.
(Example 3), 11% by weight (Example 4), 0.7% by weight (Comparative Example 1), 35% by weight (Comparative Example 2) were used in the same manner as in Example 1. I got a film. The properties of the laminated polyester film are as shown in Table 1,
Those within the scope of the present invention were excellent in each characteristic. In Comparative Example 2, since the film was fragile and broke, it was not possible to collect samples for evaluation other than the apparent density.

Example 5 Based on Example 1, the raw material for the layer A of Example 1 was supplied to the extruder A, melted at 285 ° C. by a conventional method, and introduced into the center of the T-die three-layer die. On the other hand, in order to form the B layer, a polyethylene terephthalate / isophthalic acid copolymer resin (17.5 mol% isophthalic acid, as a heat seal composition,
(Melting point: 217 ° C.) 0.04% by weight of silicon dioxide fine particles having an average particle diameter of 2.5 μm was vacuum-dried, and then the raw material was supplied to an extruder B and melted at 280 ° C. by a conventional method to form a T-die three-layer die. It was introduced inside and laminated on one surface of the layer A.
Then, in order to form the C layer, the raw material of the C layer of Example 1 is supplied to the extruder C and melted at 285 ° C. by a conventional method to obtain T.
It was introduced into a die three-layer die and laminated on the other surface of the layer A.
Hereinafter, a film was obtained in the same manner as in Example 1. The properties of the laminated polyester film were excellent as shown in Table 1.

Comparative Example 3 Based on Example 5, the same method as in Example 5 was used except that the raw materials for the C layer of Example 1 were used for both surface layers of the A layer of Example 1 in the T die three-layer die. I got a film with. As shown in Table 1, the laminated polyester film did not have heat sealability and was poor in processability.

[0067]

[Table 1]

[0068]

The laminated polyester film of the present invention is
Since it has a fine bubble layer inside, a high degree of hiding can be obtained and a clean whiteness can be exhibited. Moreover, since it is lightweight and has a high cushioning property, in the image formation using a thermal head, etc., in addition to the above characteristics,
It is possible to provide a particularly clear image.

Since the laminated polyester film of the present invention has a heat-sealing layer laminated on one side, it is possible to easily obtain a film having excellent adhesion strength with other materials, and to provide a film having excellent processing characteristics. can do.

Since the laminated polyester film of the present invention has the above-mentioned excellent properties, it can be used for cards, seals,
Courier slip, video printer image receiver, barcode printer image receiver, poster, map, dust-free paper, display board,
It can be suitably used for a wide range of applications such as photographic paper and copy paper, but is most preferably used as a base material for printing or printing by laminating with other materials.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29K 105: 16 B29L 7:00 9:00 F term (reference) 4F100 AA00H AA20C AA20H AA21A AA21H AH02A AH02B AH02H AK01B AK03B AK08B AK41A AK41K AK42A AK42B AK42C AK42J AL01C AL05B AR00C BA03 BA15 CA13A CA13B CA30B DE01H DJ01B EJ38 GB90 JA13B JB16B JK06 JK11 QQ AQ QA QAQ AQAQAQAQAQAQAQAQAQAQAQAQAQAQA

Claims (8)

[Claims] 1. A heat-sealing layer (B layer) is provided on one surface of a layer (A layer) containing a polyester resin and a thermoplastic resin incompatible with the resin as a main component and containing fine bubbles therein. ,
A polyester resin layer (C layer) that does not substantially contain fine bubbles inside is laminated on the other surface, and the overall apparent density is 0.5 g / cm ³ or more and less than 1.3 g / cm ^3. A laminated polyester film characterized by: 2. The heat seal strength is 300 g / 10 mm.
The laminated polyester film according to claim 1, which has a width or more. 3. The B layer comprises 5 long chain aliphatic dicarboxylic acid units having an alkylene group having 8 or more carbon atoms, based on all acid components.
3. The laminated polyester film according to claim 1 or 2, wherein the laminated polyester film contains 30 mol% of 1,4-butanediol unit in an amount of 80 mol% or more of all diol components. 4. The laminated thickness of the B layer is 1/500 to the total thickness.
It exists in the range of 1/3, The laminated polyester film in any one of Claims 1-3 characterized by the above-mentioned. 5. The inorganic fine particles and / or the fluorescent whitening agent are contained in at least one layer of the A layer, the B layer and the C layer, and the whitening agent is contained in the layer. Laminated polyester film. 6. The optical density obtained from the C layer side is 0.5 to 2,
Whiteness is 70-120%, The laminated polyester film in any one of Claims 1-5 characterized by the above-mentioned. 7. The content of the thermoplastic resin incompatible with the polyester resin in the layer A is in the range of 1 to 30% by weight,
The laminated polyester film according to claim 1, further comprising 0.1 to 5% by weight of at least one kind of dispersant, and the film being biaxially stretched. 8. The laminated polyester film according to claim 7, wherein the thermoplastic resin incompatible with the polyester resin in the layer A is a polyolefin resin.