JP2002052674A - Fine cell-containing laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fine cell-containing laminated polyester film enabling both of gloss printing and silk grain like printing, having effect for enhancing printing density and suitable for thermal transfer image receiving paper. SOLUTION: The fine cell-containing laminated polyester film has at least one fine cell-containing layer containing a polyolefin incompatible with polyester, and a ratio (X:Y) of the content (X wt.%) of the amorphous polyolefin in the fine cell-containing layer and the content of the crystalline polyolefin therein is 1:5-5:1 and the sum (X+Y) of the polyolefin contents is 5-30 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated polyester film containing fine bubbles, which is used as a base material of a heat-sensitive transfer type image-receiving paper such as a video printer and a digital camera.

[0002]

2. Description of the Related Art Various computers, computers, measuring machines,
As an image receiving paper (printing receptor) for printers such as slips,
A material in which a print receiving layer is provided on a support such as relatively inexpensive paper is generally used.

[0003] However, with the rapid increase in the number of printing applications, applications that require a further sense of image quality are increasing. A receiving paper used for a video printer and a digital camera is a typical example.

An image photographed by a video camera or a digital camera is separated into three primary colors of yellow, magenta and cyan, and an electric signal converted from the three primary colors is sent to a thermal transfer printer. In response to the signal, the heating head sequentially sublimates or melts the color materials on the color sheet having the three primary colors separately to form a transfer image on the image receiving paper.

The present inventors have formulated an amorphous polyolefin as a thermoplastic resin incompatible with polyester for a film used as a substrate of the above-mentioned thermal transfer type image receiving paper.
We have proposed a white opaque polyester-based laminated film (Japanese Patent Application No. 2000-29149) which is finely dispersed and biaxially stretched to generate fine bubbles. Such a film, utilizing the excellent heat resistance of the incompatible resin present in the fine voids, without deformation of the voids during printing,
The effect of maintaining heat insulation and improving the glossiness and print density of the received image is exhibited.

[0006] However, the above-mentioned base film has the following disadvantages. That is, with the progress of thermal transfer printing technology in recent years, the image definition has reached the same level as silver halide photography, and the format of the received image is required to be equivalent to that of silver halide photography. ing. The so-called "silk-tone print" is one of them. After printing three primary colors, the entire area of the image is embossed (dot-like recesses are formed on the image surface by high-energy blanking) to increase the glossiness. There is a need for a function that provides a suppressed, silk-grained print.

When the above-mentioned base film is used for the silk-like print, there is a problem that the deformation (recess) of the film due to the blanking does not occur and embossing cannot be performed.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide both glossy print and silk-like print and an effect of improving print density. An object of the present invention is to provide a microbubble-containing laminated film suitable for a heat-sensitive transfer type image-receiving paper.

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above-mentioned problems, and as a result, in order to obtain a polyester layer containing fine bubbles, an amorphous polyolefin and a crystalline polyolefin incompatible with polyester have been specified. When blended in a proportion of 0.1%, the finally obtained microbubble-containing laminated polyester film has excellent printing properties (application to silk-grained printing and improvement of printing density), for example, for video printers and digital cameras. The present invention was found to be extremely useful as a base film of a heat-sensitive transfer type image-receiving paper to be used, and the present invention was completed.

That is, the gist of the present invention is to provide a laminated polyester film having at least one fine bubble-containing layer containing a polyolefin incompatible with polyester, wherein the content of the amorphous polyolefin in the fine bubble-containing layer is high. (X weight%) and the content (Y weight%) of the crystalline polyolefin (X: Y) are 1: 5 to 5: 1, and the sum of the polyolefin content (X + Y) is 5 to 30 weight%. Wherein the laminated polyester film contains fine bubbles.

[0011]

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

In the present invention, the polyester constituting the base polyester film is typically, for example, polyethylene terephthalate in which at least 80 mol% of the structural unit is ethylene terephthalate, and at least 80 mol% of the structural unit is ethylene. Examples thereof include polyethylene-2,6-naphthalate, which is -2,6-naphthalate, and poly-1,4-cyclohexanedimethylene terephthalate, in which 80 mol% or more of the structural units are 1,4-cyclohexane dimethylene terephthalate. Other examples include polyethylene isophthalate and polybutylene terephthalate.

Examples of the copolymerization components other than the above-mentioned superior components include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol and polytetramethylene glycol, isophthalic acid, 2,7-naphthalenedicarboxylic acid, and the like.
Ester-forming derivatives such as 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid and oxymonocarboxylic acid can be used. Also,
As the polyester, besides a homopolymer or a copolymer, a small proportion of a blend with another resin can be used.

The laminated polyester film containing microbubbles of the present invention can be used as a base material of an image receiving paper for a video printer or the like, particularly, as a base material of a heat transfer type image receiving paper such as a sublimation type or a fusion type. It is necessary to exhibit acceptability and to have appropriate heat deformability so as to enable silk-like printing.

First, in order to develop a high density image receptivity, a heat insulating property is developed by providing a fine bubble containing layer (hereinafter, referred to as an A layer). In order to satisfy this characteristic, it is preferable that the void nuclei in the fine bubbles do not melt and flatten but remain in a spherical or elliptical spherical shape.

In order to obtain such an A layer, a thermoplastic resin incompatible with polyester is blended and extruded, and the obtained sheet is stretched in at least one axis direction.
A method of including fine closed cells in the A layer is preferably used.

The above-mentioned incompatible thermoplastic resin, when melted and kneaded with polyester, is not compatible with the polyester and is dispersed in the polyester in a spherical or elliptical spherical shape (sea-island model). Refers to resin.

Further, in order to enable application to a silk-screen print, the layer A constituting the film of the present invention is as follows:
As a thermoplastic resin incompatible with the polyester, an amorphous polyolefin and a crystalline polyolefin are mixed at a specific ratio (1:
5 to 5: 1).

Next, the amorphous polyolefin used in the layer A of the film of the present invention will be described.

Generally, an amorphous polyolefin is one in which a melting point (melting endothermic peak (Tm)) is hardly observed in measurement of thermal characteristics. In the present invention, it is preferable to use a norbornene-based resin as the amorphous polyolefin incompatible with the polyester, and a polymer or a polymer obtained by addition-copolymerizing at least one norbornene-based monomer with ethylene and / or propylene. It is particularly preferable to use the hydrogenated product which is a saturated polymer.

Examples of the norbornene-based monomer mentioned above include norbornene and its alkyl or alkylidene-substituted products (eg, 5-methyl-2-norbornene, 5,6-dimethyl-2-norbornene, 5-ethyl-2-norbornene, -Butyl-2-norbornene, 5-ethylidene-2-norbornene, etc.), 2,3-dihydrodicyclopentadiene, dimethanooctahydronaphthalene, and alkyl or alkylidene-substituted products thereof (for example, 6-methyl-1,4: 5 , 8-Dimethano-1,
4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethyl-
1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4: 5,8-dimethano-1,4,4a, Five,
6,7,8,8a-octahydronaphthalene) and the like.

The above-mentioned hydrogenated product refers to a product obtained by saturating almost all of the double bonds in a molecule and improving heat resistance and weather resistance.

The glass transition point (Tg) of the amorphous polyolefin used in the present invention is preferably in the range of 25 to 250 ° C, more preferably 100 to 200 ° C. Tg is 2
If the temperature is lower than 5 ° C., the void generation ability tends to decrease, and it tends to be difficult to obtain a sufficient print density. On the other hand, when the Tg exceeds 250 ° C., the dispersion diameter of the void nuclei increases, and the fine bubble-containing film tends to be roughened.

The amorphous polyolefin used in the present invention is
It is preferable to use an addition copolymer of 20 to 80 mol% of ethylene or propylene units, and it is more preferable to use an addition copolymer of 40 to 60 mol% of the above units. When the mole fraction of ethylene or propylene units is less than 20 mol%, the same problem as when Tg exceeds 250 ° C. may occur. On the other hand, when it exceeds 80 mol%, the same problem as when the Tg is less than 25 ° C. may occur.

The melt flow index (MFI) of the amorphous polyolefin used in the present invention is usually from 2 to 30 m.
The range is 1/10 minutes, preferably 5 to 25 ml / 10 minutes. When the MFI is less than 2 ml / 10 minutes, the dispersibility in the polyester deteriorates, and the generated voids increase. As a result, unevenness of the concealing property becomes remarkable and breakage during stretching is induced. May occur. on the other hand,
If the MFI exceeds 30 ml / 10 minutes, the ability to form voids decreases, and at the same time, uniform control of the density becomes difficult, and the productivity may deteriorate.

The weight average molecular weight of the amorphous polyolefin used in the present invention is preferably in the range of 1,000 to 30,000, more preferably in the range of 3,000 to 10,000. When the weight average molecular weight is less than 1,000, there is the same problem as when the MFI exceeds 30 ml / 10 minutes. When the weight average molecular weight exceeds 30,000, there is the same problem as when the MFI is less than 2 ml / 10 minutes.

Next, the crystalline polyolefin used in the layer A of the film of the present invention will be described.

Specific examples of the crystalline polyolefin include:
Polyethylene, polypropylene, polymethylpentene,
Polymethylbutene and the like, among them, among these,
From the viewpoint of cost and productivity, polypropylene and polymethylpentene are preferred, and polypropylene is more preferred. In the following description, a thermoplastic resin incompatible with polyester is represented by polypropylene.

As the above polypropylene, usually 95
Crystalline polypropylene homopolymers having at least mol%, preferably at least 98 mol%, of propylene units are preferred. In the case of amorphous polypropylene, the polypropylene may bleed out on the surface of the unoriented polyester sheet in the film production process, and the surfaces of the cooling drum, the stretching roll, and the like may be contaminated. Further, in the case of polypropylene in which ethylene units other than propylene units are copolymerized, for example, in an amount exceeding 5 mol%, the generation of fine bubbles tends to be insufficient.

The above polypropylene usually has a melt flow index (MFI) of 1.0 to 30 g / 10 min.
Preferably it is selected from the range of 2.0 to 15 g / 10 minutes. If the MFI is less than 1.0 g / 10 minutes, the generated bubbles become too large, and the glass tends to break during stretching,
When the MFI exceeds 30 g / 10 minutes, the uniformity of the film density over time is deteriorated, and the productivity may be deteriorated in the production line.

In the present invention, it is preferable to add a surfactant to the raw material in which the polypropylene is blended, and it is more preferable to use a polypropylene kneaded with the surfactant. Further, a nonionic surfactant is preferable as the surfactant. The term "surfactant" as used herein means a blend of different melt polymers that significantly alters the properties of the interface, i.e., increases the compatibility between the polyester and the thermoplastic resin incompatible with the polyester at the interface between the two. Refers to a compound that has an effect. Specifically, polyalkylene glycol types, polyhydric alcohol types,
Nonionic surfactants such as silicones are preferred,
Among them, silicone surfactants are preferred. More specifically, an organopolysiloxane-polyoxyalkylene copolymer or an alkenylsiloxane having a polyoxyalkylene side chain has a high surface activation effect, and is preferable in the present invention.

The content As (% by weight) of the surfactant in the layer A is determined by the content Y (% by weight) of the crystalline polyolefin.
Is preferably 0.002Y ≦ As ≦ 0.2Y, more preferably 0.005Y ≦ As ≦.
0.1Y. When As is less than 0.002Y, the gloss of the film surface tends to be impaired because the incompatible resin is not sufficiently finely dispersed. On the other hand, when As exceeds 0.2Y 2, the effect of accelerating the fine dispersion of the incompatible resin is no longer improved, and the film quality tends to be adversely affected, such as decreasing the whiteness of the film.

The sum (X + Y) of the contents of the amorphous polyolefin and the crystalline polyolefin incompatible with the polyester described above is determined by the fine-bubble-containing polyester layer (A
It is necessary that the ratio in the total composition of the layer) is 5 to 30% by weight, preferably 7 to 25% by weight, more preferably 10 to 20% by weight. When X + Y is less than 5% by weight, the amount of bubbles formed in the layer A is small,
A sufficiently lightweight and cushioning film cannot be manufactured. On the other hand, when X + Y exceeds 30% by weight, the amount of generated bubbles is excessive, and the roughness of the film surface becomes too large.

In the layer A of the present invention, the ratio (X: Y) of the content (X wt%) of the amorphous polyolefin to the content (Y wt%) of the crystalline polyolefin is 5: 1 to 1: 1. 5
And preferably from 3: 1 to 1: 3,
More preferably, it is 2: 1 to 1: 2. X: Y = 5:
When the ratio of X exceeds 1, embossing becomes difficult at the time of silk-grain printing. On the other hand, when the ratio of Y rises from X: Y = 1: 5, the print density and glossiness decrease.

The microbubble-containing laminated polyester film of the present invention has a thermal deformation at 200 ° C. and 0.125 MPa of preferably 2 to 25%, more preferably 4 to 20%, and still more preferably 6 to 17%. It is. If the thermal deformation ratio is less than 2%, there is a tendency that embossing is not sufficiently applied to the image surface when performing silk-tone printing.
On the other hand, when the thermal deformation ratio exceeds 25%, uniform embossing becomes difficult, and even in printing of three primary colors, problems such as uneven gloss due to surface deformation tend to occur.

The apparent density (ρ) of the microbubble-containing laminated polyester film of the present invention is 0.7 to 1.3 g / cm 3.
And more preferably 0.8 to 1.
2 g / cm 3, more preferably 0.9 to 1.1 g / cm 3
cm3. If ρ is less than 0.7 g / cm 3, rupture frequently occurs during film formation, and the productivity tends to be poor. When ρ exceeds 1.3 g / cm 3, the cushioning property is inferior, and when used as an image receiving paper base material for a video printer or the like, the print density at the time of printing decreases and the cost per unit area may increase. is there.

The laminated polyester film containing fine bubbles of the present invention preferably has a high gloss from the viewpoint of obtaining a fine and beautiful image when used as a base material for an image receiving paper. 8741-1
The 60 ° gloss G60 according to Method 3 of 983 is preferably 60% or more. If G60 is less than 60%, the definition (glossiness) of the received image tends to be impaired. G60 is more preferably 70% or more, and still more preferably 75% or more. When G60 is more than 120%, the film surface becomes excessively flat, causing problems such as blocking during roll processing, easy damage, and transfer of a plurality of image receiving papers in an overlapping manner. There is.

In the present invention, the surface roughness Ra of the film on the side on which the image receiving layer is provided is preferably 0.03 to 0.20 μm. When Ra is smaller than 0.03 μm,
The same problem may occur as when the film surface is too flat and the glossiness exceeds the upper limit. On the other hand, Ra is 0.2
If it exceeds 0 μm, the definition of the received image tends to be impaired. A more preferable range of Ra is 0.04 to 0.5.
15 μm, more preferably 0.04 to 0.10
μm.

The laminated polyester film containing fine bubbles of the present invention is preferably white and has a high degree of concealment from the viewpoint of obtaining a fine image when used as a base material of an image receiving paper. In order to provide such physical properties, a fluorescent whitening agent can be contained. The fluorescent whitening agent that can be used in the present invention has a wavelength of 400 to 700 n.
Any type may be used as long as it has a fluorescence peak at m, but preferred are trade names Iupitex OB (Ciba Specialty), OB-1 (Eastman Kodak) and Mika White (Nippon Kayaku- Commercial products such as Mitsubishi Chemical Corporation. The content of the optical brightener in the film is preferably 0.3% by weight or less. When the content of the fluorescent whitening agent exceeds 0.3% by weight, the cost of raw materials increases, and the effect of improving the whiteness by the whitening agent tends to be saturated. On the other hand, when the content of the optical brightener is 0.0
If the amount is less than 1% by weight, improvement in whiteness may be insufficient. A more preferred content of the fluorescent whitening agent is 0.01 to
0.2% by weight.

In order to further increase the whiteness, it is effective to use white inorganic particles in combination. Examples of the above-mentioned white inorganic particles include known titanium oxide, calcium carbonate, barium sulfate, and the like. Among these, titanium oxide having a small particle size and being granular is preferable in view of image receptivity.

In the present invention, the crystal form of the titanium oxide particles which can be blended in the polyester may be either anatase type or rutile type, but is preferably anatase type titanium oxide particles from the viewpoint of whiteness and weather resistance. . Further, the surface of the titanium oxide particles is aluminum for the purpose of improving dispersibility in polyester and weather resistance,
Those treated with an oxide and / or an organic compound such as silicon or zinc can also be used.

The average particle size of the titanium oxide particles is 0.20 to 0.20.
A range of 0.50 μm is preferred. Average particle size 0.20μ
If it is less than 0.5 m or more than 0.50 μm, the degree of concealment when formed into a film tends to decrease, and the prevention of light transmission tends to be insufficient.

The addition amount of the titanium oxide particles is usually 1
-20% by weight. If the addition amount of the particles is less than 1% by weight, the degree of concealment in a film tends to decrease, and the prevention of light transmission tends to be insufficient. If the amount of the particles exceeds 20% by weight, breakage tends to occur during film formation, or the mechanical strength of the film tends to be poor.

In the above description, the fluorescent whitening agent and the white inorganic particles may be added to either the fine bubble-containing polyester layer (A layer) or any layer other than the A layer, or to both. You may.

The laminated polyester film containing fine bubbles of the present invention has a Hunter whiteness (Wb) defined by JIS P8123-1961 and a film thickness of about 200.
It is preferable that the value measured by superimposing so as to correspond to μm is 85 or more. When the whiteness is less than 85, the image (color tone) lacks in definition when used as an image receiving base material, and tends to impair a sense of quality. Preferred Hunter whiteness is 88 or more, more preferably 90 or more.

The whiteness of the laminated polyester film containing fine bubbles of the present invention is separately described in JIS Z872.
The b value defined by 2 and Z8730 can be used as an index. Specifically, the film is about 200μ thick.
The b value measured by superimposing so as to correspond to m is from +1.0 to
It is preferably in the range of -10. b value is +1.0
When the ratio is more than 3, the film has a strong yellow tint and tends to impair the high-grade appearance of the (receiving image) as an image receiving substrate. On the other hand, when the b value is less than -10, the film tends to be bluish, and the color of the received image tends to be modulated. The more preferred film b value is in the range of -1.0 to -8.0, and still more preferably in the range of -3.0 to -7.0.

A coating layer can be provided on the laminated polyester film containing fine bubbles of the present invention. The application surface is
It does not matter whether one side or both sides of the polyester film is used, but from the viewpoint of preventing blocking (double feeding) of the image receiving paper for a video printer, it is preferable to have a coating layer having antistatic ability on both sides.

The surface specific resistance of the coating surface is 1 × 101
It is preferably 2Ω or less, more preferably 1 × 1
011Ω or less, more preferably 1 × 1010
It is less than Ω.

The composition of the coating layer is not particularly limited as long as it satisfies a desired surface resistivity (1 × 10 12 Ω or less). For example, the following composition can be used.

(A) a polymer having a pyrrolidium ring in the main chain, (b) at least one polymer selected from polyesters, polyacrylates, polyurethanes and chlorine-containing polymers, and (c) melamine and / or epoxy polymers. A coating layer containing a crosslinking agent.

The polymer having a pyrrolidium ring in the main chain, which is one of the above coating agent components, is, for example, a compound represented by the following formula (I)
Alternatively, it is a polymer having the structure of (II) as a main component.

[0052]

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[0053]

Embedded image

In the above formulas (I) and (II), R1, R
2 is each independently an alkyl group, a phenyl group or the like, and these alkyl groups and phenyl groups may be substituted with the following groups.

Examples of the displaceable group include a hydroxyl group, an amide group, a carbo lower alkoxy group, a lower alkoxy group, a thiophenoxy group, a cycloalkyl group and a tri-
(Lower alkyl) ammonium lower alkyl group, etc., wherein the nitro group can be substituted only on the alkyl group and the halogen group can be substituted only on the phenyl group. Also, R ₁ , R ₂
May be chemically bonded, for example, (CH ₂ ) _m
(M = 2 to 5 _{integer), - CH (CH 3)} -CH (CH
₃ )-, -CH = CH-CH = CH-, -CH = CH
-CH = N-, -CH = CH-N = CH-, (CH
₂ ) ₂ O (CH ₂ ) ₂ , (CH ₂ ) ₂ O (CH ₂ ) _{2 and the} like. X ⁻ in the above formula is Cl ⁻ , Br ⁻ , 1
/ 2SO ₄ ^2-, or 1 / 3PO ₄ ^3- and the like inorganic acid residue,
The sulfonic acid residues of CH ₃ SO ₄ ⁻ and C ₂ H ₅ SO ₄ ⁻ are shown.

The amount of the polymer having a pyrrolidium ring in the main chain to be mixed in the coating solution for obtaining the coating layer of the present invention is usually 5 to 50% by weight, preferably 10 to 40% by weight. If the amount is less than 5% by weight, the antistatic property after coating the image receiving layer described later tends to be insufficient. If the amount exceeds 50% by weight, the adhesion to the image receiving layer may be insufficient.

Polyester, polyacrylate, and polyester compounded in a coating solution for obtaining a coating layer of the film of the present invention.
The total compounding amount of at least one polymer selected from polyurethane and chlorine-containing polymer is usually 20 to 90% by weight, preferably 30 to 80% by weight. If the amount is less than 20% by weight, the adhesion to the image receiving layer tends to be insufficient. If the amount exceeds 90% by weight, the blocking resistance may be insufficient.

The total amount of the melamine or epoxy crosslinking agent blended in the coating solution is usually 5 to 50% by weight,
Preferably it is 10 to 45% by weight. When the amount is 5
If the amount is less than 50% by weight, the effect of improving antistatic properties and blocking resistance tends to be insufficient. If the amount is more than 50% by weight, the adhesion to the image receiving layer may be insufficient.

In the present invention, by further blending a lubricant into the coating layer, it is possible to impart a slipperiness and an appropriate releasability. Examples of the lubricant include polyolefin-based wax, mineral oil, animal and vegetable oils, waxes, esters, metal soaps, and the like. If a polyolefin-based wax is used, the adhesiveness is not impaired.

Further, the coating layer of the film of the present invention may contain an antifoaming agent, a coating improver, a thickener, an inorganic particle, an organic polymer particle, an antioxidant, an ultraviolet absorber, a foaming agent, if necessary. It may contain a dye or the like.

When the microbubble-containing laminated polyester film of the present invention is used as a substrate for a video printer, an image receiving layer of a sublimation dye is usually provided on the film.
As the components of the image receiving layer, generally, polyester resins, polyurethane resins, polyamide resins, vinyl chloride resins, and mixtures or copolymers thereof can be used. If necessary, a release improver such as various waxes and silicons, and inorganic particles such as silica and titanium oxide can be added.

The laminated structure of the film of the present invention is basically composed of two types of two layers of B / A or two types of three layers of B / A / B. However, other multilayer structures may be used.

In the method for producing the microbubble-containing laminated film of the present invention, generally, a predetermined blended polymer is melted and extruded, and then stretched in at least one axial direction according to a roll stretching method, a tenter method or the like. In addition, in order to form fine bubbles satisfactorily and appropriately satisfy film strength and dimensional stability, it is preferable to use both the biaxial stretching method and the heat treatment method.

Here, an example in which biaxial stretching is used will be described in detail.

First, the raw materials are compounded for each layer, supplied to the corresponding extruder, and melt-kneaded for each extruder line.
The molten polymer in each layer is guided to a die, usually through a multi-manifold or feedblock, and laminated. next,
The molten sheet extruded from the die is quenched and solidified on the rotating cooling drum to a temperature below the glass transition temperature,
An unoriented sheet in a substantially amorphous state is obtained. In this case, in order to improve the flatness of the sheet and the cooling effect, it is preferable to increase the adhesion between the sheet and the rotary cooling drum,
In the present invention, the electrostatic application contact method is preferably employed.

Next, the obtained sheet is biaxially stretched to form a film. The fine bubbles contained in the polyester film of the present invention are generated by such stretching.
First, usually 70 to 150 ° C, preferably 75 to 130 ° C
Stretching temperature, usually 2.5 to 6.0 times, preferably 3.0 times.
The unstretched sheet is stretched in one direction (longitudinal direction) under the condition of a stretch ratio of up to 5.0 times. For this stretching, a roll and tenter type stretching machine can be used. Then, at a stretching temperature of usually 75 to 150 ° C, preferably 80 to 140 ° C, usually 2.5 to 6.0 times, preferably 3.0.
The film is stretched in a direction (lateral direction) perpendicular to the first stage under the condition of a stretch ratio of up to 5.0 times to obtain a biaxially oriented film. For such stretching, a tenter-type stretching machine can be used.

A method in which the above unidirectional stretching is performed in two or more stages can be adopted, but also in this case, it is preferable that the final stretching ratio falls within the above range. It is also possible to simultaneously biaxially stretch the unstretched sheet so that the area magnification becomes 7 to 30 times.

Next, heat treatment in a tenter is usually performed at 140 ° C.
It is carried out at a temperature of from 240 to 240 ° C., preferably from 200 to 235 ° C., for 1 second to 5 minutes under elongation, limited shrinkage or constant length within 30%.

The method of providing a coating layer on the fine bubble-containing polyester film of the present invention is described in Yuji Harazaki,
A reverse roll coater, a gravure coater, a rod coater, an air doctor coater, and the like described in “Coating method”, published in Maki Shoten, 1979, can be used. Using these coating devices, usually, a method of applying to a film uniaxially stretched in the longitudinal direction, in a dry or undried state, further stretching in a direction perpendicular to the further uniaxial stretching direction, and then performing a heat treatment. It is preferably employed in terms of manufacturing cost.

When the stretching treatment is not performed after the application, the adhesion between the formed coating layer and the polyester film is weak, and there is a case where the adhesiveness suitable for practical use cannot be obtained. In addition, when heat treatment is not performed after coating, drying of the coating layer becomes insufficient and the film tends to be remarkably blocked.

The thickness of the coating layer in the final dry thickness is usually in the range of 0.01 to 0.5 μm, preferably 0.0
It is in the range of 2 to 0.3 μm. Coating layer thickness is 0.01
If it is less than μm, a sufficient antistatic effect or the like may not be provided. On the other hand, when it exceeds 0.5 μm, the films tend to easily block each other.

The thickness of the microbubble-containing laminated polyester film of the present invention is usually in the range of 12 to 250 μm, preferably 20 to 100 μm. The thickness of the fine bubble-containing polyester layer (layer A) is preferably 75% or more of the total thickness, more preferably 85% or more. When the thickness of the A layer is less than 75%, problems such as insufficient heat deformability of the film as a whole, and insufficient lightness and cushioning property may be caused.

The film of the present invention makes use of its features,
Various heat-sensitive transfer receiving papers, such as those for video printers, labels, recording papers, posters, and stickers, as a laminated film containing microbubbles alone or as a bonded body with other materials such as paper, synthetic paper, and plastic films. It is suitably used for printing mounts, planographic printing plates, packaging materials, sticky notes, and the like.

[0074]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the present invention. In addition, various physical properties in the present invention, their measurement methods, and definitions are as follows. In Examples and Comparative Examples, “parts” and “%” mean “parts by weight” and “% by weight”, respectively. (1) Melt flow index MFI (ml /
According to JIS K7210-1995, the amorphous cyclic polyolefin copolymer was measured at 275 ° C. and 21.2 N, and the PP was measured at 230 ° C. and 21.2 N. The higher this value, the more
Indicates that the melt viscosity of the polymer is low. (2) Glass transition point Tg, melting point Tm (° C.) Using a differential scanning calorimeter (DSC7 type manufactured by PerkinElmer), under a nitrogen atmosphere, 5 mg of a sample was heated from room temperature at a heating rate of 10 ° C./min, The point of change in specific heat associated with the second-order transition type was defined as Tg, and Tm if a melting endothermic peak was observed. (3) Average particle size of additive (μm) Centrifugal sedimentation type particle size distribution analyzer SA- manufactured by Shimadzu Corporation
The particle size was measured using a CP3 type by the sedimentation method based on Stokes' resistance law. The average particle size was determined using a value of 50% of the integrated (volume basis) in the equivalent spherical distribution of the particles obtained by the measurement. (4) Thermal Deformation Rate (%) A penetration (needle entry) mode of a thermomechanical tester (TM-7000 type manufactured by Vacuum Riko Co., Ltd.) was used. The original thickness of the film at room temperature is d1, the thickness when 0.125 MPa is added in an atmosphere at 200 ° C. is d2, and the rate of change is (d1−d2) × 100 / d1 (%) as the thermal deformation rate. .

The temperature was raised at a rate of 10 ° C./min, and the reading of d 2 was performed in a stable state with a sufficiently small change. (5) Apparent density (g / cm 3) A 10 cm × 10 cm square sample was cut out from an arbitrary portion of the film, and the thickness was measured at nine locations evenly with a micrometer. From the average value and the weight of the film,
The weight per unit volume was calculated and defined as the apparent density. The number of measurements was five, and the average value was used. (6) Hunter whiteness Nippon Denshoku Industries Co., Ltd. colorimeter NDH-1001DP (C
JIS P8123-1961 using a light source, 2 ° field of view)
According to the method described above, the whiteness (Wb) of five stacked films was measured. The back of the film was pressed with a black plate. (7) b value Nippon Denshoku Industries Co., Ltd. colorimeter NDH-1001DP (C
JIS Z-8722, 8 using a light source, 2 ° field of view)
According to the method of 730, five layers of film b
The value was measured. The back of the film was pressed with a black plate. (8) Gloss (%) Measured by irradiating light in the MD direction on the film surface according to Method 3 (60 ° gloss) of JIS Z-8741-1983. The measurement surface was equivalent to the cast surface (cast roll contact surface side). The number of measurements n was 3, and the average value was calculated. (9) Center line average surface roughness Ra (μm) Measured using a universal surface shape measuring instrument SE-3F manufactured by Kosaka Laboratory. The measurement was carried out seven times under the following conditions, and the average value of five points excluding the upper and lower two points was taken.

・ Diameter of stylus tip: 2 μm ・ Measurement force: 0.03 gf ・ Measuring length: 2.5 mm ・ Cutoff value: 0.8 m
m (10) Surface resistivity (Ω) Yokogawa Hewlett-Packard's concentric electrode “16”
008B (trade name) "(inner electrode 50 mm diameter, outer electrode inner diameter 70 mm, outer diameter 80 mm, guard electrode 80 mm diameter)
The film after application of the image receiving layer is placed in an atmosphere of 20 ° C. and 65% RH, and a high resistance meter “4339B (product) manufactured by the company based on the current flowing from the inner electrode to the outer electrode when a voltage of 100 V is applied. Name) "was used to measure the surface resistance. (11) Density of printed image Toyobo "Byron 600" (polyester): 62 parts by weight UCC "VYHH" (vinyl chloride vinegar): 26 parts by weight Shin-Etsu Chemical "KF-393" (amino-modified silicon): 6 parts by weight Shin-Etsu Chemical "X-22-343" (epoxy-modified silicon): 6 parts by weight For the image-receiving layer, the above coating material was dissolved in a mixed solvent of methanol / methyl ethyl ketone / dimethylformamide and used as a 20% by weight solution. The film was applied to a thickness of 5 μm.

A film was laminated on both sides of a paper having a basis weight of 125 g / m 2, and a test image was printed on a surface of the film coated with an image receiving layer using a Sony Corporation color video printer “DPP-MS700”. Compared.

◎: High density and good 〇: High density next to ◎ and good Δ: Slightly low density but practicable level ×: Low density and lack of sharpness (12) Applicability to Silk-tone Print The silk-tone print was performed in the above section 11 and the image quality was evaluated.

〇: Good silk-tone print Δ: Inferior to Δ but no problem in practical use ×: Hardly embossed, no silk-tone print obtained Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.65 The chip is the main raw material, and the melt flow index is 18 ml / 10 minutes and the glass transition point is 160
7.5% of an amorphous cyclic olefin copolymer (norbornene-ethylene copolymer, norbornene 55 mol%) having a melting point of 5,000 ° C. (no melting point observation) and a weight average molecular weight of 5,000.
(X) a general-purpose polypropylene (MFI 10 ml / 10) previously kneaded with 0.8% of a silicone surfactant (SH193 manufactured by Dow Corning Toray Silicone Co., Ltd.)
Raw material containing 7.5% (Y), 2.5% of titanium oxide particles having an average particle diameter of 0.3 μm, and 0.1% of a fluorescent whitening agent (OB-1 manufactured by Eastman). The mixture A was directly charged into a vented twin-screw extruder (main), and a polyethylene terephthalate chip having an intrinsic viscosity of 0.64 was used as a main raw material.
m of titanium oxide particles: 7% by weight of a raw material mixture B was directly charged into a vented twin-screw extruder (sub).

Both raw materials were melted and kneaded at 270 ° C. in a twin-screw extruder, and the obtained melt was mixed in a multilayer T-die with B / A /
B and extrude into a slit shape to form
It cooled on the cooling drum of 0 degreeC, and obtained the non-stretched sheet.

Next, the unstretched sheet is heated at 80 ° C. in the longitudinal direction.
And then stretched 3.4 times with a coating solution of the coating composition shown below (5% by weight aqueous dispersion) to a coating thickness of 4.5 μm (wet).
Is applied to both sides of the film, stretched 4.0 times in the transverse direction at 125 ° C.
Heat treated at 5 ° C. for 5 seconds. Final film thickness 38μ
m, and a biaxially oriented film having a thickness ratio (B / A / B) of 1.5 / 35 / 1.5 μm was obtained.

Composition of coating solution: polydimethyldiallylammonium chloride (molecular weight = 30000): 20%, methyl methacrylate / ethyl acrylate / methylol acrylamide copolymer (monomer ratio: 47.5 / 4)
7.5 / 5 mol%): 40%, methoxymethyl melamine: 40% Examples 2-5, Comparative Examples 1-4 Except that the raw material formulation A of Example 1 was changed as described in Table 1, the examples were changed. In the same manner as in Example 1, a biaxially oriented film having a film thickness of 38 μm was obtained.

The raw material composition and film properties of the obtained microbubble-containing film are summarized in Tables 1 and 2 below.

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[Table 1]

[0085]

[Table 2]

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According to the present invention, high printing density of an image receiving paper required for high speed and labor saving of a printer and embossing characteristics are combined, and further, image quality excellent in whiteness and glossiness is obtained. An obtainable laminated polyester film containing fine cells can be provided, and its industrial value is very high.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 23/12 C08L 45/00 23/20 67/02 45/00 B41M 5/26 H 67/02 101H F Terms (reference) 2H111 AA01 AA26 AA27 CA13 CA25 CA41 CA43 CA45 4F100 AK04A AK07A AK08A AK41A AL05A AT00B BA02 CA13 CA23 DJ06A EH20 EJ38 GB41 JA11A JA12A JL01 JL05 YY00A 4J002 BB03X BB12X00

Claims (5)

[Claims] 1. A laminated polyester film having at least one microbubble-containing layer containing a polyolefin incompatible with polyester, wherein the content (X% by weight) of the amorphous polyolefin in the microbubble-containing layer is The ratio (X: Y) of the content (Y weight%) of the crystalline polyolefin is 1:
5 to 5: 1 and the sum of the polyolefin contents (X
+ Y) is 5 to 30% by weight. 2. The laminated polyester film containing fine bubbles according to claim 1, wherein the amorphous polyolefin is a norbornene resin. 3. The laminated polyester film containing fine bubbles according to claim 1, wherein the crystalline polyolefin is polypropylene or polymethylpentene. 4. The thermal deformation rate at 200 ° C. and 0.125 MPa is 2 to 25%.
3. The laminated polyester film containing fine bubbles according to any one of 3. 5. A heat-sensitive transfer type image-receiving paper, wherein the laminated polyester film containing fine bubbles according to claim 1 is used as a substrate.