JPH10316782A - Fine-void-containing polyester resin film or sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fine-void-containing polyester resin film which resists thermal curling or wrinkling even when used as e.g. a sublimation transfer recording material, a thermal transfer recording material or a thermal recording material. SOLUTION: There is provided a fine-void-containing polyester resin film or sheet comprising a polyester resin A and a thermoplastic resin incompatible with resin A, wherein the ratio of the average length of voids to their average thickness in an arbitrary unidirectional cross section vertical to the surface of the film or sheet is 7.0 or above, the number of the voids in the cross section is 30 voids/2,500 μm or above, and the entire apparent specific gravity is 0.6-1.3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester resin film or sheet containing a large amount of fine voids inside a film or sheet, and a method for producing the same. Is hard to cause curl or wrinkle due to heat, and can be widely used as a base material of a sublimation transfer recording material, a thermal transfer recording material, a heat-sensitive recording material, a printing sheet, or the like.

[0002]

2. Description of the Related Art A void-containing film, which is a paper substitute made of a synthetic resin as a main material, is more water-resistant, absorbs moisture, has dimensional stability, surface stability, and glossiness of printed matter than paper made of a natural pulp. Since it is excellent in properties, sharpness, mechanical strength, etc., in recent years, various applications have been developed utilizing its characteristics.

[0003] The main raw materials of the void-containing film include polyolefin resins such as polyethylene and polypropylene;
Or, there are polyester resins, among which polyester resins represented by polyethylene terephthalate have important characteristics required as a void-containing film, such as high heat resistance and strong stiffness. Have been.

A method for obtaining a film having a function similar to that of natural paper using a polyester resin as a main raw material is described in (1).
A method of containing a large amount of fine cavities inside the film,
(2) A method of roughening an ordinary flat polyester film by sandblasting, chemical etching, matting (a method of laminating a matting agent with a binder), or the like.

[0005] Among them, the method (1) is superior to the method (2) in that it is excellent in reducing the weight of the film itself and can impart appropriate flexibility, thereby providing clear printing and transfer. And is currently the most effective. Specifically, it is a method in which a resin incompatible with a polyester resin and a raw material resin are melt-kneaded with an extruder to form a film in which the incompatible resin is dispersed in polyester and then stretched. .

As a resin incompatible with a polyester resin capable of causing cavities in a film (hereinafter, sometimes referred to as a cavitation agent), a polyolefin resin (for example, Japanese Patent Application Laid-Open No. -134755), a polystyrene-based resin (for example, Japanese Patent Publication No. 49-20)
No. 16, JP-B-54-29550 and the like, and polyarylate resins (for example, JP-B-58-28097) have been reported.
From the viewpoint of economy and the like, it is recommended to use a polypropylene resin or a polystyrene resin. However, in the case of a film using such a conventional cavity developing agent, the obtained cavity is thick or / and large. Therefore, when the film is used as a substrate such as a thermosensitive recording material, curling or wrinkling due to heat may occur. There's a problem. For example, JP-A-63-
The film described in Japanese Patent No. 168441 has a considerably large cavity size of 50 to 100 μm at maximum, and when such a film is used as a heat-sensitive recording material, a large number of curls and wrinkles due to heat are generated. Therefore, in order to optimize the size and thickness of the cavities, for example, JP-A-63-193998 and JP-A-3-76727 disclose a surfactant or a polyalkylene glycol or the like in the film to reduce the cavities. A method of adding is disclosed. However, when such a low molecular weight component is mixed, the heat resistance of the film is reduced, and thus, under conditions where high temperature heat is applied to the support at the time of recording, such as thermal transfer, thermal transfer, and sublimation transfer,
There is a problem that curls and wrinkles are generated in that portion.
Such a problem could not be solved by a general method used for improving heat resistance (for example, a method of heat setting after completion of stretching).

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to provide a heat transfer recording material, such as a sublimation transfer recording material, a heat transfer recording material, or a heat-sensitive recording material. An object of the present invention is to provide a polyester resin film containing fine cavities which does not cause curl or wrinkles due to the above.

[0008]

The polyester resin film or sheet containing fine voids of the present invention, which has solved the above-mentioned problems, comprises a polyester resin (A) and a polyester resin (A). In a polyester resin film or sheet containing fine cavities containing a compatible thermoplastic resin (B), the ratio of the average length of cavities to the average thickness of cavities in any one-way cross section perpendicular to the film or sheet surface is The point is that the number of cavities in the cross section is 7.0 or more, the number of cavities in the cross section is 30 / 2,500 μm ² or more, and the entire apparent specific gravity is 0.6 to 1.3.

The thermoplastic resin (B) is preferably a thermoplastic resin (B ₁ ) that is incompatible with the polyester resin (A), the polyester resin (A) and the thermoplastic resin (B). B ₁ ), which contains a thermoplastic resin (B ₂ ) that is incompatible with both and has a higher surface tension than the thermoplastic resin (B ₁ ), and the thermoplastic resin (B ₂ ) those containing 0.01 to 20 parts by weight relative to the thermoplastic resin (B ₁₎ 100 parts by weight.

It is preferable that the above-mentioned film or sheet of the present invention is subjected to transverse stretching in two or more different temperature ranges and the final transverse stretching is performed at a temperature of 180 ° C. or more.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the polyester resin film or sheet containing fine voids of the present invention (hereinafter referred to as a film again) has characteristics inherent to the polyester resin film containing voids, that is, writing. Nature, printing
It is intended to prevent the occurrence of curl and wrinkles due to heat by optimizing the size of the cavity without impairing transferability etc., and such characteristics clearly appear in relation to conventional materials, As defined above, (1) the ratio of the average length of the cavity to the average thickness of the cavity in any one-way cross section perpendicular to the film or sheet surface (hereinafter sometimes simply referred to as the size of the cavity) Is 7.0
(2) The number of cavities in the cross section (hereinafter sometimes simply referred to as the number of cavities) is 30/2500 μm
and m ² or more, (3) are those apparent specific gravity of 0.6 to 1.3, which satisfies all of such requirements, those bought found in conventional void-containing polyester resin film It is.

As described above, the film of the present invention is a polyester resin film containing fine voids containing a polyester resin (A) and a thermoplastic resin (B) incompatible with the polyester resin (A). It is. Hereinafter, these components will be sequentially described.

First, the polyester constituting the polyester resin (A) serving as the base resin in the present invention includes aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid and naphthalenedicarboxylic acid or esters thereof, ethylene glycol and diethylene glycol. , 1,
4-butanediol, a polyester obtained by polycondensation with a glycol such as neopentyl glycol,
These polyesters are prepared by a method of directly reacting an aromatic dicarboxylic acid and a glycol, a polycondensation after an ester exchange reaction between an alkyl ester of an aromatic dicarboxylic acid and a glycol, or a diglycol of an aromatic dicarboxylic acid. It can also be produced by a method of polycondensing an ester. Representative examples of such polyesters include polyethylene terephthalate, polyethylene butylene terephthalate, and polyethylene-2,6-
Naphthalate is exemplified. These polyesters may be homopolymers or copolymers obtained by copolymerizing the third component. Of course, in the present invention, the ethylene terephthalate unit and the butylene terephthalate unit are used. Or ethylene-
The ratio of 2,6-naphthalate units occupies 70 mol% or more, more preferably 80 mol% or more, and further preferably 9 mol% or more.
0 mol% or more of polyester is preferred.

The thermoplastic resin incompatible with the polyester (B) used in the present invention is essentially incompatible with the base polyester and dispersed in the polyester resin. Any resin may be used as long as it is uniformly mixed in the state and causes peeling at the interface with the base resin at the time of stretching to serve as a cavity forming source. Examples of preferred resins include polystyrene resins and polyolefins. Resin, polyacrylic resin, polycarbonate resin,
Polysulfone resins, cellulose resins and the like can be mentioned. These can be used alone, or two or more of them can be used in combination, if necessary, or they can be copolymerized to impart an appropriate affinity to the polyester. Among these, polystyrene-based resins and polyolefin-based resins such as polymethylpentene and polypropylene are recommended as preferred.

The preferred amount of the thermoplastic resin (B) varies depending on the amount of voids required in the finally obtained film, the stretching conditions, and the like, but is usually a ratio of the total amount of the resin composition. 3% by weight to 40% by weight
Less, more preferably in the range of 5 to 30% by weight. If the amount is less than 3% by weight, the amount of cavities generated in the stretching step is insufficient, and it is difficult to obtain satisfactory lightness, flexibility, drawing properties, writability, and the like. In addition, heat resistance, strength, or stiffness may be impaired.

[0016] Preferably, the thermoplastic resin (B) is
(I) a thermoplastic resin (B ₁ ) that is incompatible with the polyester resin (A); and (ii) a thermoplastic resin (B ₁ ) that is incompatible with both the polyester resin (A) and the thermoplastic resin (B ₁ ). a compatible, and a large thermoplastic resin surface tension (surface energy) than the thermoplastic resin (B _1), the thermoplastic resin (B ₁₎ with respect to 100 parts by weight of 0.01 to 20 Thermoplastic resin contained by weight (B ₂ )
Is included.

That is, the thermoplastic resin (B ₂ ) has a cavity-producing effect similarly to the above (B ₁ ) in that it is a thermoplastic resin incompatible with the polyester resin (A). However, while (B ₁ ) mainly exhibits a cavity-forming effect, (B ₂ ) also has the property of being a thermoplastic resin incompatible with (B ₁ ), and (B ₁ ) By mixing (B ₂ ) having a higher surface tension than B ₁ ) with (B ₁ ) at a specific ratio, a thermoplastic resin incompatible with polyester is finely dispersed in the raw material resin. This has the effect of effectively exerting the "action" and, consequently, uniformly forming fine cavities. Therefore, in the following description, in order to distinguish from the working face thereof and (B ₁₎ to (B _2), referred to as a cavity expressing agent (B _1), will be referred to as dispersible resin (B _2).

[0018] Conventional polyester resin containing fine voids
In the case of film, we also want to finely disperse the cavity
Large amounts of two or more different cavity enhancers added for the purpose
Was. However, by such a conventional method,
The cavities that are created are cavities that are short in length for their thickness.
There were many things that were inappropriate, such as getting lost. Elucidate the cause
As a result of extensive studies by the present inventors, a cavity developing agent,
Thermoplastic resin added to finely disperse cavitation agent
The surface tension between them and their mixing ratios are large
It was found to have an effect. That is, "Cavity developing agent is 2
If more than one species is mixed, the resin with low surface tension
The resin is covered by high surface tension resin,
Most of the ters form an interface with a cavity generator with high surface tension
Will be done. Therefore, polyester
The adhesiveness of the developing cavitation agent increases and the cavitation ability is remarkable
It is unsuitable for its thickness and its length is short for its thickness
A sharp cavity appears. " So
Here, in the present invention, "raw resin"
Effect of micro-dispersion of cavity-generating agent into the inside "
The dispersible resin (B_Two ) Characteristics
As described above, "Cavity developing agent (B₁ ) Than surface tension
Large thermoplastic resin "and its content
"Cavity developing agent (B₁ ) 0.01 to 100 parts by weight
20 parts by weight ".
If the amount is less than 0.01 part by weight, the fine particles
Diffusing effect cannot be exhibited effectively, while 20
If the amount exceeds the amount, the dispersible resin (B_Two ) Is a cavity developing agent (B
₁ ) To cover most of the
Is an inappropriate size, such as the formation of a short cavity
Will be formed. Cavity developing agent (B₁ )
Dispersible resin (B _Two ) Is defined in the present invention.
Within this range, the dispersing resin having a high surface tension (B_Two )
Is a cavity developing agent having a lower surface tension (B₁ )
Even if it is partially covered or thinly and uniformly covered (covered
The shape of the resin is not limited to these,
Other than this, depending on the type, for example, mesh-like
If there are parts and parts that are not covered periodically
Or various cases such as combinations of these cases.
), The adhesion to polyester
There is no substantial effect. Therefore, dispersible resin
(B_Two ) Can be effectively used
The cavity developing agent (B₁ ) In polyester resin
It can be finely dispersed in
Many cavities can be obtained. Preferably, the
The lower limit is 0.02 parts by weight, more preferably 0.1 part by weight.
On the other hand, the upper limit is preferably 15 parts by weight, more preferably
Preferably it is 10 parts by weight.

As described above, the properties and the content of the dispersible resin used in the present invention are defined as described above, so that the dispersant can exhibit its function as a dispersant.

The above-mentioned cavity developing agent (B ₁ ) and dispersible resin (B
Examples of the combination of ₂ ) include, for example, the following.

When a polyolefin resin such as a polymethylpentene resin, a polypropylene resin, a cyclic olefin polymer, or a silicone resin is used as the cavity developing agent (B ₁ ), the dispersing resin (B ₂ ) For example, a polystyrene resin, a polycarbonate resin, a polyacryl resin, a polyphenylene ether resin, a polyolefin resin modified with maleimide or carboxylic acid, a polystyrene resin, or the like is used. Alternatively, the cavity developing agent (B
_{When a} polystyrene resin is used as ₁ ), a polycarbonate resin, a polyacryl resin, a polyphenylene ether resin, or a polyolefin resin modified with maleimide, carboxylic acid, or the like is used as the dispersible resin (B ₂ ). These dispersible resins (B ₂ ) can be used alone or as a mixture of two or more if necessary.

The preferable amount of the incompatible resin (B ₁ ) and the dispersible resin (B ₂ ) in the polyester resin depends on the amount of voids required in the finally obtained film and the stretching conditions. Although it also varies, it is usually selected from the range of 3 to 30% by weight, more preferably 5 to 25% by weight in the total amount of the resin composition. 3% by weight
If it is less than 30%, the amount of cavities generated in the stretching step will be insufficient, and it will be difficult to obtain satisfactory lightness, flexibility, drawing properties, writability, and the like. In addition to a significant decrease, heat resistance, strength or stiffness may be impaired.

The film of the present invention contains the above-mentioned constituents as essential components. The film contains inorganic or organic fine particles for the purpose of imparting hiding properties (non-permeability or whiteness) to the film. Is also effective. Such fine particles include silica, kaolin, talc, calcium carbonate, zeolite, alumina, barium sulfate,
Examples thereof include inorganic fine powders such as carbon black, zinc oxide, and titanium oxide; and organic fine powders such as a crosslinked polymer and an organic white pigment. If necessary, an appropriate amount of other components such as an antistatic agent, an ultraviolet absorber, a plasticizer, and a coloring agent can be contained.

The polyester resin film containing fine voids according to the present invention may have a single layer structure or a multilayer structure of two or more layers in which a surface layer and a center layer are laminated. The production method of such a multilayer film is not particularly limited, but in consideration of productivity, the raw materials of the surface layer and the central layer are extruded from separate extruders, and guided to one die to obtain an unstretched sheet. The most preferable method is a lamination method by a so-called coextrusion method in which the film is uniaxially stretched.
In both single-layer and multi-layer films,
For the apparent density, cavity size and number of cavities,
It must satisfy the above requirements.

Here, the apparent specific gravity must be in the range of 0.6 to 1.3. If the apparent specific gravity is less than 0.6, the void content is too high, and the film becomes insufficient in strength or cracks or wrinkles are liable to be generated on the film surface, so that the commercial value is significantly reduced. If the specific gravity is more than 3, the void content is insufficient, and the properties provided by the void formation, such as cushioning and flexibility, cannot be effectively exhibited.

In the film of the present invention, the average thickness of the cavity when an arbitrary one-way cross section is cut out from the film surface is defined as T1, the average length of the cavity is defined as L1, and the cross-section in a direction perpendicular to the perpendicular direction. When the average thickness of the cavity at the time of cutting out the cavity is T2 and the average length of the cavity is L2, L1 / T1 and L2
The average of 2 / T2 is 7.0 or more, preferably 10.
0 or more, more preferably 13.0 or more. By generating a large number of cavities thinner than the length in this way, it is possible to solve all the problems of thermal transferability and wrinkles. If the above ratio is less than 7.0, wrinkles due to heat occur.

Further, the number of cavities in the section is 30 /
2500 μm^Two Or more, preferably 35/250
0 μm^Two Or more, more preferably 40 pieces / 2,500
μm ^Two That is all. When the number is less than 30, the above ratio is
Even if it is 7.0 or more, each cavity is quite large
This causes wrinkles.

The properties required for the polyester resin film containing fine cavities according to the present invention are as described above.
A film that satisfies such required characteristics has very excellent characteristics such as curling and wrinkling caused by heat because the size of the cavity is optimized.

Although the method for producing the film of the present invention having the above-mentioned various properties is not particularly limited, in order to produce the film efficiently, a polymer mixture of the above polyester-based resin, cavity-forming agent and dispersible resin is used. After being formed into a film or a sheet, it is preferable to perform transverse stretching in two or more different temperature ranges and to perform final transverse stretching at a temperature of 180 ° C. or more. The reason for setting such manufacturing conditions will be described in detail later, and the steps of manufacturing the film of the present invention will be sequentially described.

First, the above-mentioned components used in the present invention are mixed and melt-extruded to obtain an unstretched sheet. Examples of this method include a method in which a mixture of chips of each resin is melt-kneaded in an extruder and then extruded and then solidified, a method in which those resins previously kneaded in a kneader are further melt-extruded and solidified in an extruder, In the polyester polymerization process,
A method of adding a thermoplastic resin which is incompatible with the polyester-based resin, stirring and dispersing the resulting mixture, and extruding and solidifying the obtained chips is used. The unstretched sheet obtained in this manner is usually in a non-oriented or weakly oriented state, and the thermoplastic resin incompatible with the polyester-based resin may have various shapes such as spherical or elliptical spherical, or thread-like. It will be dispersed in the polyester resin in shape.

The method of stretching the unstretched film thus obtained is not particularly limited, but at least one method is used.
It is necessary to stretch in the axis, and peeling occurs at the interface between the thermoplastic resin and the polyester which are incompatible with the dispersed polyester, and a large number of cavities are generated. The methods include a roll stretching method (a method of stretching between two or more rolls having different peripheral speeds in the running direction of the film), a long gap stretching method, and a tenter stretching method (a stretching method of holding and expanding a clip. ), A tubular stretching method, an inflation stretching method (a stretching method of expanding by air pressure) and the like can be used, and the film is stretched in a predetermined direction (main stretching direction) by these known stretching methods.
In either method, stretching is performed by sequential biaxial stretching, simultaneous biaxial stretching, uniaxial stretching, or a combination thereof. When biaxial stretching is used, stretching in the vertical and horizontal directions may be performed simultaneously, but in order to obtain a better stretching effect, a sequential biaxial stretching method in which one of them is stretched first is recommended. . In this case, the stretching order in the vertical and horizontal directions may be performed in any order. However, in consideration of mechanical properties, the film is first stretched in the longitudinal direction corresponding to the film flow direction, and then sequentially stretched in the transverse direction. It is preferable to use an axial stretching method. In the following description, the sequential biaxial stretching method will be specifically described as an example, but the present invention is not limited to this method.

In producing the film of the present invention, it is preferable that the transverse stretching is performed in two or more different temperature ranges and the final transverse stretching temperature is in the range of 180 ° C. or more. In this way, the transverse stretching conditions are particularly specified because the conventional stretching temperature is as low as 80 to 140 ° C., so that the deformation of the cavity is not sufficiently obtained, and the cavity is sufficiently thin to satisfy the above-described requirements of the present invention. Is difficult to obtain.

Here, in the conventional method of successively biaxial stretching, the unstretched sheet is first roll-stretched in the longitudinal direction, and then tenter-stretched in the width direction.
This is a method of performing heat treatment at 0 ° C. or higher (Japanese Patent Laid-Open No. 63-168).
441, JP-A-63-193938, JP-A-2-80247, JP-A-2-284929, JP-A-3-114817, JP-A-4-202
540, etc.). Here, in roll stretching (longitudinal stretching), the stretching temperature is set to 80 to 1 in order to generate many cavities.
00 ° C., stretching ratio 2.0-5.0, then tenter stretching (lateral stretching) 80-140 ° C., stretching ratio 2.8.
It is preferable to set it to 5.0. However, in such a conventional manufacturing method, as described above, since the temperature at the time of the transverse stretching is low, it is difficult to obtain the deformation of the cavity.For example, polyolefin resins such as polymethylpentene and polypropylene and polystyrene resins have glass transition temperatures. Since the temperature is 100 ° C. or lower, the cavities may be deformed and collapsed during tenter stretching. This means that even if the stretching temperature is increased to 140 ° C., sufficient deformation cannot be obtained, and it is difficult to form a cavity sufficiently thin enough to satisfy the requirements of the present invention.

The above-described transverse stretching step is very useful as a method capable of overcoming such a problem. Specifically, first, the first horizontal stretching is performed for 100 to 150 times.
After stretching at 2.0 to 3.0 times at 200C, the second horizontal stretching is further stretched at 180 to 230C to 1.2 to 2.0 times.
Here, the first horizontal stretching magnification needs to be lower than the longitudinal stretching magnification. The first stretching is for obtaining a biaxially stretched film in which cavities are sufficiently generated, and the second stretching is for obtaining a thin, well-balanced cavity in the vertical and horizontal directions. There is almost no effect of increasing the number of cavities by stretching. The sum of the first and second horizontal stretching ratios may exceed the vertical stretching ratio. After the stretching, it is preferable to further perform a heat treatment, and the heat treatment temperature is preferably 200 ° C. or more, more preferably 220 ° C. or more, and still more preferably 230 ° C.
That is all. When the heat treatment temperature is less than 200 ° C., when used for a thermal transfer recording material or the like, preferable heat treatment conditions required for the film (the heat shrinkage at 150 ° C. is preferably less than 2%, more preferably less than 1.7%, Even more preferably less than 1.5%). The heat treatment may be performed after performing a relaxation treatment of 2 to 5%.

The polyester resin film containing fine cavities according to the present invention thus obtained may be provided with a coating layer on one or both sides thereof for improving the wettability with ink or the like, if necessary. Is also effective. As a main component of the coating layer, a polyester resin having a good affinity for the film is preferable, but in addition, a polyurethane resin, a polyester / urethane resin, an acrylic resin, and the like, with respect to a normal polyester resin film. A resin used for improving the adhesiveness or the like is appropriately selected and used. As the method for forming the coating layer, all known methods such as a gravure coating method, a kiss coating method, a dip coating method, a spray coating method, a curtain coating method, an air knife coating method, a blade coating method, and a reverse roll coating method are applicable. It is. As for the timing of application, before the stretching of the film (that is, a method of applying the polymer mixture to the surface of the polymer mixture before the stretching treatment), after the stretching (that is, after applying the film to the surface of the cavity-containing film stretched in the uniaxial direction, The stretching may be performed at any point after the stretching in the perpendicular direction) or after the relaxation treatment (that is, the method of coating the surface of the void-containing film after the stretching treatment).

The polyester resin film containing fine cavities obtained in this way has a more optimized size of cavities than the conventional polyester resin film containing cavities, and prevents curling and wrinkling due to heat. Demonstrate excellent performance that can be. Therefore, this film can be used for labels, stickers, posters, cards, recording paper, packaging materials, video printer receiving paper, barcode labels, barcode printer receiving paper, thermal transfer receiving paper, thermal recording paper, sublimation transfer receiving paper, inkjet receiving paper. paper,
Offset printing paper, form printing paper, map, dust-free paper, sign board, white board, electronic white board, photographic paper, decorative paper, wallpaper,
Construction materials, bills, release papers, origami, calendars, magnetic cards, tracing papers, slips, delivery slips, pressure-sensitive recording papers, copy papers, clinical test papers, parabolic antenna reflectors, display reflectors, etc. It can be effectively used for applications.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples do not limit the present invention, and all modifications that can be made without departing from the spirit of the present invention will be described. Within the technical scope of

[0038]

EXAMPLES The measuring and evaluating methods employed in the following examples are as follows. In the following description, “parts” represents “parts by weight”, and “%” represents “% by weight”.

(1) Intrinsic viscosity of polyester Polyester was dissolved in a mixed solvent of phenol (6 parts) and tetrachloroethane (4 parts) and measured at 30 ° C.

(2) The thickness of a film accurately cut into a square having an apparent specific gravity of 5.00 cm × 5.00 cm was measured at 50 points, and the average thickness was t.
(Μm). In addition, the weight of the film is 0.1 m.
The measurement was made up to the unit of g to obtain W (g), and the apparent specific gravity was calculated by the following equation. Apparent specific gravity = w / (5 × 5 × t × 10000)

(3) Sections perpendicular to the L1 and T1 film surfaces (in the vertical and horizontal directions) were examined with a scanning electron microscope (S-510, manufactured by Hitachi, Ltd.).
After the photograph was taken at a magnification of 0 times, the figure in which the cavities were traced and painted on a tracing film was subjected to image processing by an image analyzer. FIG. 1 is a cross-sectional view showing the shape of the cavity obtained in this manner.
Represents the cavity, L represents the length of the cavity, and T represents the thickness of the cavity. L1 and T1 are calculated by averaging L and T in the total number of cavities (50 cavities counted from cavities having a large area). The image analyzer used was an image scanner (GT-800) manufactured by Seiko Epson Corporation.
0), and the obtained image is converted to software (AdobePhoto) of a personal computer (Macintosh).
shop TM 2.5J), then the software (U
ltimage ™ / 242.1.1).

(4) n1 The thickness 50 near the center of the photograph taken by the method of (3).
The number of cavities contained in μm × length 50 μm was counted.

(5) Initial elastic modulus Measured according to ASTM D-882-81 (Method A).
The measurement conditions were as follows: distance between chucks: 40 mm, width: 1
Stress at a measurement length of 0 mm and a pulling speed of 200 mm / min was measured, and a value immediately after the start of pulling (substantially directly proportional) was calculated.

(6) Heat Shrinkage Rate A film is cut so that the direction in which the film shrinks is the long side and the width is 10 mm and the length is 250 mm to make a sample, and a mark is made in the long side direction with a gap of 200 mm. The interval A after fixing the sample under a constant tension (5 g) is measured.
Next, the interval B after being placed in an oven at 150 ° C. for 30 minutes under no tension was measured, and the heat shrinkage was calculated according to the following equation. Heat shrinkage (%) = [(AB) / A] × 100

(7) Light transmittance Boic integrating sphere formula T. The light transmittance of the film was measured using an R meter (manufactured by Nippon Seimitsu Kogaku) according to the JIS-K6714 method. The smaller the measured value, the higher the shading.

(8) Presence or absence of curl and wrinkles due to heat from a printer After an anchor layer having the following composition is provided on the film surface, a receiving layer having the following composition is provided thereon, and a color hard copy [Seiko Denshi Co., Ltd. Industrial Co., Ltd., D-SC
ANCH-5504) actually output the image from the video. The case where no curl or wrinkle was generated in the output printed matter was evaluated as ○, the case where it was slightly generated was evaluated as Δ, and the case where it was completely generated was evaluated as x.

Anchor layer Urethane dry laminating agent [A-130 manufactured by Takeda Pharmaceutical Co., Ltd.] 100 parts Curing agent [A-3 manufactured by Takeda Pharmaceutical Co., Ltd.] 30 parts Receiving layer vinyl chloride / vinyl acetate copolymer [ ＄ # 1000D manufactured by Denki Kagaku Kogyo Co., Ltd.] 100 parts Amino-modified silicone [X-22-343 manufactured by Shin-Etsu Chemical Co., Ltd.] 3 parts Epoxy-modified silicone [KF-393 manufactured by Shin-Etsu Chemical Co., Ltd.] 3 parts Methyl ethyl ketone / Toluene (weight ratio: 1/1) 500 parts

Example 1 A raw material having the following composition was charged into a twin-screw extruder, melt-extruded from a T-die at 290 ° C., and then electrostatically adhered and solidified on a cooling rotary roll to obtain about 11%.
An unstretched sheet made of a polymer mixture of 00 μm was obtained.
Next, the unstretched sheet was stretched 3.1 times at 80 ° C. in a roll stretching machine, and then transversely stretched 2.6 times at 125 ° C. with a tenter.
The film was transversely stretched 1.4 times at a temperature of ° C. Thereafter, a 4% relaxation heat treatment at 235 ° C. was performed to obtain a polyester resin film of the present invention containing a large number of voids inside the film (thickness: about 100 μm).

Polyethylene terephthalate resin (intrinsic viscosity: 0.62) 70% Polystyrene resin for general use (PS) [T575-57U manufactured by Mitsui Toatsu Chemicals, Inc.] 25% Maleimide-modified polystyrene resin (M-PS) [Mitsuhito Pressure Chemical Co., Ltd. NH1200] 1% Anatase type titanium dioxide (average particle size 0.35 μm) [Fuji Titanium Co., Ltd. TA-300] 3%

With respect to the film thus obtained,
Table 1 shows the results of measuring the above evaluation items. In addition, about the result obtained in the following Example and the comparative example, Table 1
Also described in 3.

Example 2 In Example 1, a crystalline polypropylene resin [PP, FO-50F manufactured by Mitsui Toatsu Chemicals, Inc.] was used instead of PS.
Was used in the same manner as in Example 1, except that 20% was used and 2% of PS was used instead of M-PS.

Example 3 In Example 1, PP was replaced by 10% and M-
A film of the present invention was obtained in the same manner as in Example 1 except that 1% of PS was used instead of PS.

Example 4 In Example 1, a cyclic olefin resin [COC, Apel APL60 manufactured by Mitsui Petrochemical Co., Ltd.] was used instead of PS.
11] and using 1% of PS instead of M-PS, to obtain a film of the present invention in the same manner as in Example 1.

Example 5 In Example 1, 15% of a polymethylpentene resin [PMP, RT-18 manufactured by Mitsui Petrochemical Co., Ltd.] was used instead of PS, and 1% of PS was used instead of M-PS. A film of the present invention was obtained in the same manner as in Example 1 except for the above.

Example 6 In this example, a laminated film having a three-layer structure was manufactured.

That is, using the raw material of Example 3 as the A layer,
The following materials are used as the B layer, and each material is separated into 2
Except that an unstretched sheet was obtained by putting into a screw extruder, kneading, bonding in a T-die into B / A / B, extruding, and electrostatically adhering to a cooling roll. In the same manner as in Example 1, a film of this example was obtained. The thickness of the film thus obtained (μ
m) was B / A / B = 5/90/5. Polyethylene terephthalate resin (intrinsic viscosity 0.62) 98% Spherical zeolite particles [JC-20 manufactured by Mizusawa Chemical Co., Ltd.] 2%

Example 7 The film of this example was prepared in the same manner as in Example 6, except that the raw material of Example 5 was used as the raw material of the A layer and the following raw material was used as the raw material of the B layer. Obtained. Polyethylene terephthalate resin (intrinsic viscosity 0.62) 90% Calcium carbonate (average particle size 0.6 μm) 10%

Comparative Example 1 A film of a comparative example was obtained in the same manner as in Example 2 except that the horizontal stretching step was performed only at 125 ° C.

Comparative Example 2 In Example 2, polyethylene glycol [PEG, molecular weight 4,000, Daiichi Kogyo Seiyaku Co., Ltd. was used instead of PS.
The film of Comparative Example was obtained in the same manner as in Example 2 except that 0.5% was used.

Comparative Example 3 A film of Comparative Example was obtained in the same manner as in Example 2 except that the content of PS was changed to 0.

Comparative Example 4 A film of a comparative example was obtained in the same manner as in Example 2 except that the content of PS was changed to 10%.

Comparative Example 5 A film of a comparative example was obtained in the same manner as in Example 2, except that the content of PP was 30% and the content of PS was 0.

Comparative Example 6 A film of a comparative example was obtained in the same manner as in Example 2 except that PP and PS were changed to 0.

[0064]

[Table 1]

[0065]

[Table 2]

[0066]

[Table 3]

From Tables 1 to 3, it can be considered as follows. In the monolayer films of the present invention of Examples 1 to 5, the size, the number of cavities, and the apparent specific gravity of the cavities are within the range of the present invention. As a result, light weight, flexibility, shading, heat shrinkage, and the like are obtained. And no curl or wrinkles due to heat were observed. Further, even when a laminated film was formed as in Examples 6 and 7, the same effect was confirmed, so that the film of the present invention is effective in both single-layer and laminated forms. I understood that.

On the other hand, the films of Comparative Examples 1 to 3 had the number of cavities, the film of Comparative Example 4 had the size of the cavities, and the film of Comparative Example 5 had the apparent specific gravity and the number of the cavities, respectively. Since it was outside, curls and wrinkles occurred. Further, the film of Comparative Example 6 did not have the voids defined in the present invention, so that unevenness occurred during printing with a printer, and the appearance of the printed matter was poor.

[0069]

Since the film of the present invention is constituted as described above, the same effect as that of a conventional film using a polystyrene-based resin or a polyolefin-based resin as a cavity developing agent (namely, lightness, flexibility, etc.) is obtained. Properties, shading properties, matting properties, drawing properties, etc.), and are less susceptible to curling or wrinkling due to heat than these conventional films. Therefore, the film of the present invention is not only a sublimation transfer recording material, a thermal transfer recording material, a heat-sensitive recording material, a printing sheet, but also a label, a poster, a recording paper, a packaging material, a slip, a courier delivery slip, a copy sheet, It can be used in a wide range of fields such as pressure-sensitive paper.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the shape of a cavity in an embodiment.

[Explanation of symbols]

 1 Cavity developing agent 2 Cavity

 ──────────────────────────────────────────────────の Continued on front page (72) Inventor Toshitake Suzuki 2-1-1 Katata, Otsu City, Shiga Prefecture Toyobo Co., Ltd. Research Laboratory

Claims (3)

[Claims] 1. A microvoided polyester resin film or sheet containing a polyester resin (A) and a thermoplastic resin (B) incompatible with the polyester resin (A), wherein the film or sheet surface is The ratio of the average length of the cavities to the average thickness of the cavities in any one direction cross section perpendicular to the cross section is 7.0 or more, the number of cavities in the cross section is 30 or more / 2500 μm ² or more, and the total apparent specific gravity is 0. A polyester resin film or sheet containing fine cavities, which is 6 to 1.3. 2. The thermoplastic resin (B) comprises: a thermoplastic resin (B ₁ ) incompatible with the polyester resin (A); and the polyester resin (A) and the thermoplastic resin (B). ₁ ) contains a thermoplastic resin (B ₂ ) which is incompatible with both and has a surface tension larger than that of the thermoplastic resin (B ₁ ), and the thermoplastic resin (B ₂ ) Thermoplastic resin (B
₁ ) The polyester resin film or sheet containing fine voids according to claim 1, which is contained in an amount of 0.01 to 20 parts by weight based on 100 parts by weight. 3. The film or sheet according to claim 1, wherein the film or sheet is transversely stretched in two or more different temperature ranges, and the final transverse stretching is performed at a temperature of 180 ° C. or more.