JPH07118434A - Polyester film for handy printer use - Google Patents

Abstract

PURPOSE:To obtain a polyester film for a handy printer use excellent in opacifying properties, drawing properties, film forming properties, etc., by mixing polyester with inorganic particles and/or an incompatible thermoplastic resin, extruding the mixture and orienting the extruded material uniaxially or biaxially. CONSTITUTION:The objective film is obtained by mixing (A) polyester with (B) inorganic particles (e.g. titanium dioxide, calcium carbonate) and/or (C) a thermoplastic resin incompatible with the polyester (preferably, polystyrene resin or polyolefin resin, e.g. polymethylpentene), extruding the mixture and orienting the extruded material monoaxially or biaxially. The obtained film is >=10mum and <=40mum in thickness and has light transmittance <=30% and whiteness degree of >=75. Further, the objective film containing many fine hollow parts inside and having an apparent specific gravity of >=1.0 and <=1.3 is obtained by mixing a component A with a component C, melting and extruding the mixture and orienting the extruded material uniaxially or biaxially.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for a handy printer, which is excellent in productivity and film-forming property even though it is thin and has good hiding property and drawing property.

[0002]

2. Description of the Related Art For meter reading of electricity and gas, staff members check the meters installed in each home, fill in the results, and put the memos in the posts and entrances of the homes. In recent years, a handy printer has been used for this work, which outputs the result immediately when the result is entered. There are also JR, private railway in-car payments and general office applications such as those sold under the name "Tepla" (King Office┷). These incorporate a thermal recording type printing device. Therefore, the paper for printing is put in it. Although this paper is wound in a roll shape, if the paper is thick, the winding diameter becomes large, and therefore the replacement work of the rolls becomes large for a large amount of printing. Therefore, if the paper is made thinner, the concealing properties of conventional papers are insufficient, and there are drawbacks such that the back can be seen through and letters are difficult to see, and a solution has been desired.

[0003]

SUMMARY OF THE INVENTION The present invention is intended to provide a handy printer base material which is excellent in concealing property, film strength, film-forming property and productivity, etc. is there.

[0004]

That is, according to the present invention, polyester is mixed with inorganic particles and / or thermoplastic resin incompatible with the polyester, and the mixture is extruded and oriented at least uniaxially and has a thickness of 10 μm or more and 40 μm or more. Below, the light transmittance is 3
The present invention relates to a polyester film for a handy printer, which has a whiteness of 0% or less and a whiteness of 75 or more. The polyester in the present invention means an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid or naphthalenedicarboxylic acid or an ester thereof and ethylene glycol, diethylene glycol, 1,4-butanediol,
It is a polyester produced by polycondensation with glycol such as neopentyl glycol. These polyesters may be obtained by directly reacting an aromatic dicarboxylic acid with a glycol, and then transesterifying an alkyl ester of an aromatic dicarboxylic acid with a glycol, followed by polycondensation, or a diglycol ester of an aromatic dicarboxylic acid. Is produced by a method such as polycondensation.
Typical examples of such polyesters include polyethylene terephthalate, polyethylene butylene terephthalate or polyethylene-2,6-naphthalate. This polyester may be a homopolymer or a copolymer of a third component. In any case, in the present invention, ethylene terephthalate units, butylene terephthalate units or ethylene-
A polyester having a 2,6-naphthalate unit content of 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more is preferable.

In the present invention, a particularly important point is that the thickness can be reduced to 40 μm or less even though a large amount of inorganic particles are present in the polyester. Usually, as a means for imparting concealing property to a plastic film, that is, a means for lowering the light transmittance, a method of expressing a large number of internal cavities, applying a pigment or a dye to the surface layer of the film, or containing a large number of inorganic particles inside is used. There is. However, if the content of cavities or inorganic particles is further increased in order to further improve the hiding property, there arises a problem that the strength of the film decreases and the film-forming property becomes unstable. Further, when the coating amount of the pigment is increased, there is a problem that the pigment comes off. Therefore, as a method for improving the hiding property so as not to cause these problems, it is possible to secure the stretchability even if a large number of inorganic particles are contained inside the film.

In the case of a usual void-containing polyester film, the added inorganic particles such as titanium dioxide, calcium carbonate, silicon dioxide and barium sulfate are all present in the matrix polyester. Therefore, when the addition amount of the inorganic particles is increased, the interface generated between the polyester and the inorganic particles is increased, and the tensile strength and film formability of the film are likely to decrease. This is 40μ thick
This is a particularly serious problem with a film having a thickness of m or less.

Therefore, as one of means for solving these problems, a method of treating the surface of inorganic particles with an inorganic substance containing aluminum, silicon, zinc, etc. to improve affinity with polyester or a method of adding a large amount to the surface layer of a laminated film Have been disclosed so far. However, in these methods, it is not possible to maintain the film strength, the surface strength and the film-forming property by containing a large amount of inorganic particles so as to achieve a light transmittance of 30% or less at a thickness of 40 μm or less, preferably 30 μm or less. It is possible. This is because the inorganic particles have a high surface energy and thus have a higher affinity for the polyester having a higher surface energy than the cavity developing agent.

[0008] Therefore, as a means to reach the present invention, it is possible to increase the addition amount of the inorganic particles in order to improve the hiding property and to mix the stretching aid. As a result, even if the content of the inorganic particles is increased, problems such as film strength and film forming property are eliminated. Polyethylene glycol such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and / or the like as a drawing aid.
Alternatively, derivatives and / or copolymers thereof may be used. Examples of the derivative include those obtained by blocking the terminal group with another bond, those obtained by polyesterification by reaction with a dicarboxylic acid, and the like. Among these, polyethylene glycol, polyethylene glycol copolymers and polyesters or copolymerized polyesters obtained by dioling these are particularly preferable. The polyethylene glycol and / or its derivative has a molecular weight of 200 to 200,000, preferably 1,000 to 50,000. The addition amount is 0.05 to 5% by weight, preferably 0.1 to 1% by weight, based on the entire film. If it is less than 0.05% by weight, stretching becomes difficult, and if it exceeds 5% by weight, the film becomes stiff and the processability such as printing is deteriorated.

Therefore, as another means, the amount of inorganic particles added is increased to improve the hiding property, and the polyester is added to the inside of the polyester in order to contain a large number of cavities by a method described later. An incompatible thermoplastic resin (cavity-developing agent) is mixed. At that time, not all the inorganic particles are uniformly dispersed in the polyester, but the increased inorganic particles are made to exist around the cavities and the cavity developing agent, preferably in the cavity developing agent. As a result, even if the content of the inorganic particles is increased, the interface with the polyester is not increased, so that problems such as film strength and film formability are eliminated. In order to achieve this, the surface of inorganic particles such as titanium dioxide, calcium carbonate, and barium sulfate, which are commonly used, is subjected to water rehydration treatment to lower the surface energy, thereby increasing the affinity between the inorganic particles and the cavity developing agent. Improves that of polyester. Examples of the treating agent include silicon-based resins, siloxane-based resins, fluorine-based resins, silane coupling agents and titanate coupling agents, and more preferably those surface-treated with aromatic or aliphatic polymer compounds. Specifically, those that organically bond the inorganic particles and the cavity developing agent, such as polyvinyl pyridine, are preferable. However, it is not limited to this. Further, it becomes effective by using the inorganic particles treated in this way as a masterbatch pellet pre-kneaded with a void-forming agent. In the case where the pre-kneading is not carried out, the inorganic particles are all present in the polyester even if the surface treatment is carried out, so that the object of the present invention cannot be achieved. As another method, a laminated film may be used, and the amount of inorganic particles in the surface layer of the film may be larger than that in the central layer. In this case, the whiteness of the film is improved and the matte feeling is imparted, and a high-grade image is provided, especially because the content of the inorganic particles is increased in the surface layer.

The inorganic particles used in the present invention are not particularly limited. Examples include titanium dioxide, calcium carbonate, barium sulfate, silicon dioxide, aluminum oxide, talc, kaolin and the like. Further, these inorganic particles may be surface-treated as necessary. Examples of the treating agent include, but are not limited to, aluminum oxide, silicon dioxide, zinc oxide, silicon-based resin, siloxane-based resin, fluorine-based resin, silane coupling agent or titanate coupling agent, polyol or polyvinyl pyridine. Not something. In the present invention, it preferably contains a large number of cavities inside.
The method of containing the cavities is not particularly limited, but preferably an unstretched sheet obtained by mixing, melting, and extruding an incompatible thermoplastic resin (cavity-developing agent) in the polyester is at least obtained. By orienting it uniaxially,
This is a method in which the interface between the polyester and the void-developing agent is peeled off to obtain a large number of voids inside. The cavity-developing agent must be incompatible with the polyester described above.
Specific examples include polystyrene resins, polyolefin resins, polyacrylic resins, polycarbonate resins, polysulfone resins, cellulose resins, polyamide resins, and the like. In particular, polystyrene resins, polyolefin resins such as polymethylpentene and polypropylene are preferable.

The polymer mixture obtained by mixing the polyester of the present invention and an incompatible thermoplastic resin to the polyester is prepared by, for example, mixing chips of each resin, melt-kneading in an extruder, and then extruding and solidifying. Method, or a method in which both resins are kneaded in advance by a kneader to be melt-extruded and solidified by an extruder, or an incompatible thermoplastic resin is added to the polyester in the polyester polymerization step and dispersed by stirring. It can also be obtained by a method of melt-extruding and solidifying the obtained chips. The polymer obtained by solidifying (unstretched sheet) is usually in a non-oriented state or a weakly oriented state. Further, the thermoplastic resin incompatible with the polyester is present in the polyester in a form dispersed in various shapes such as a spherical shape, an elliptic spherical shape, or a thread shape.

The polymer mixture obtained by mixing the polyester of the present invention and the incompatible thermoplastic resin with the polyester is prepared by, for example, mixing chips of each resin, melt-kneading in an extruder, and then extruding and solidifying. Method, or a method in which both resins are kneaded in advance by a kneader and further melt-extruded by an extruder to solidify, or an incompatible thermoplastic resin is added to the polyester in the polyester polymerization step and dispersed by stirring. It can also be obtained by a method of melt-extruding and solidifying the obtained chips. It is possible to add a colorant, a light-proofing agent, a fluorescent agent, an antistatic agent, etc. to the polymer mixture depending on the application. The obtained polymer mixture is further stretched between rolls having different speeds (roll stretching), stretched by gripping and expanding by a clip (tenter stretch), and stretched by expanding by air pressure (inflation stretch). At least one axis is subjected to orientation treatment by, for example, By the orientation treatment, peeling occurs at the interface between the polyester and the void-developing agent, and voids are developed.

Therefore, the amount of the thermoplastic resin which is incompatible with the polyester and mixed with the polyester varies depending on the amount of the target voids, but is preferably 3 to 40% by weight, preferably 3 to 40% by weight, based on the whole polymer mixture. Is 8% by weight
It is 20% by weight. . If it is less than 3% by weight, there is a limit to increase the amount of cavities generated, and the desired flexibility, lightness, and drawability cannot be obtained. On the other hand, when it is 40% by weight or more, the heat resistance and strength of the polyester film are significantly impaired. The conditions for orienting the polymer mixture are closely related to the formation of cavities. Therefore, the conditions for achieving this object are, for example, the most commonly used sequential 2
Taking the axial stretching step as an example, a sequential biaxial stretching method in which a continuous sheet of the polymer mixture is roll-stretched in the longitudinal direction and then tenter-stretched in the width direction is as follows. In the roll drawing, the temperature is set to be not more than the biaxial drawing temperature of polyester + 30 ° C. and the magnification is 1.2 in order to generate many cavities.
It is preferably ˜5 times. In the tenter stretching, the temperature is preferably 100 to 140 ° C. and the magnification is preferably 1.2 to 5 in order to stably form a film without breaking. It is desirable to carry out the heat treatment condition after stretching by the method described below. After the stretching, the heat treatment is performed at 200 ° C or higher, preferably 220 ° C.
As described above, more preferably at 230 ° C. or higher. Further, at this time, heat fixation must be performed while relaxing by 3 to 8%. If it is less than 200 ° C or less than 3%, the heat shrinkage ratio at 150 ° C is less than 2%, preferably 1.
A void containing film of less than 7%, more preferably less than 1.5% is not obtained.

The average porosity of the whole is preferably 40% by volume or less, preferably 30% by volume or less, and the average porosity is 4 or less.
A void-containing film of 0% by volume or more is difficult to manufacture because it frequently breaks during the stretching process, and the resulting film is not preferable because the surface strength and tensile strength are insufficient. The film of the present invention preferably has an apparent specific gravity of 1.
It is 0 to 1.3, more preferably 1.06 to 1.25. If it is less than 1.0, winding misalignment tends to occur when the paper is rolled and set in the printer. Also, 1.3
With the above, the hand-cutability from the cut becomes poor.

The light transmittance of the film of the present invention is preferably 30% or less, more preferably 25% or less, more preferably 20% or less, and particularly preferably 17% or less. This is because the back side can be seen through when it exceeds 30%. This is especially true for thin ones of 40 μm or less, preferably 30 μm or less, but thicker ones may be used. The film of the present invention must have a whiteness of 75 or more, preferably 80 or more. When it is less than 75, the printed characters are unclear.

In the present invention, a so-called composite film in which a surface layer and a central layer are laminated may be used. The method is not particularly limited. However, considering productivity, the raw materials for the surface layer and the central layer are extruded from separate extruders and
At least 1 after leading to two dies and obtaining unstretched sheet
Most preferred is the so-called co-extrusion method of laminating in the axial direction. In this case, the thermoplastic resin provided in the B layer is not particularly limited, and specifically includes polystyrene resin, polyolefin resin, polyacrylic resin, polycarbonate resin, polysulfone resin, cellulose resin, polyamide resin, etc. Can be given. However, polyester resins are preferred in the present invention. Also,
Inorganic particles may be contained if necessary. Further, the polyalkylene glycol and / or its derivative can be added to only the A layer or the B layer or both the A layer and the B layer. In this case, addition to the layer A makes it possible to improve the surface adhesiveness, water wettability, and the like.

Further, by providing a coating layer on the surface of the film, the wettability and the adhesiveness of the ink and the coating agent are improved. The compound constituting the coating layer,
Polyester resins are preferred, but in addition to these, compounds disclosed as means for improving the adhesiveness of ordinary polyester films such as polyurethane resins, polyester urethane resins and acrylic resins can be applied. As a method for providing the coating layer, a commonly used method such as a gravure coating method, a kiss coating method, a dip method, a spray coating method, a curtain coating method, an air knife coating method, a blade coating method, and a reverse roll coating method can be applied. As the step of applying, a method of previously applying to the surface of the mixed polymer before the orientation treatment, a method of applying to the surface of the uniaxially oriented cavity-containing film and further orienting it in the orthogonal direction, Any method such as coating on the finished film surface is possible. The film thus obtained has excellent concealing properties even if it is thin, so that characters can be seen clearly,
It is a good base material for handy printer paper with excellent film strength and film forming properties.

Examples Next, examples of the present invention will be shown. 1) Intrinsic viscosity of polyester Polyester was dissolved in a mixed solvent of phenol (6 parts by weight) and tetrachloroethane (4 parts by weight) and measured at 30 ° C.

2) Melt Flow Index of Polystyrene Resin Measured at 200 ° C. under a load of 5 kg in accordance with JIS-K7210.

3) Apparent specific gravity The film was cut into a square of 5.00 cm × 5.00 cm and the thickness was measured at 50 points to obtain an average thickness of t μm.
The weight was calculated up to 0.1 mg to be wg, and the weight was calculated by the following formula.

[0021]

[Equation 1]

4) Average Porosity of Film Calculated by the following formula.

[0023]

[Equation 2] However,

[0024]

[Equation 3]

[0025]

[Equation 4] In the above equation, xi represents the weight fraction of the i component, and di represents the true specific gravity of the i component. The values of true specific gravity used in the calculations in the examples are polyethylene terephthalate 1.40, general-purpose polystyrene 1.05, and anatase-type titanium dioxide 4.2.
Was used.

5) Light transmittance According to JIS-K6714, Poic integrating sphere type H.264. T.
The light transmittance of the film was measured using an R meter (manufactured by Nippon Seimitsu Optical Co., Ltd.). The smaller this value, the higher the concealing property.

6) Tensile Strength of Film The tensile strength of the film was measured according to JIS-C2318.

7) Whiteness The whiteness was measured according to JIS-L1015-1981-B method using Z-1001DP manufactured by Nippon Denshoku Industries Co., Ltd.

8) Heat Shrinkage A film having a width of 10 mm and a length of 250 mm is 200 m
Mark at m intervals and fix under a constant tension of 5 g, and mark intervals A
Measure Subsequently, the space B between the marks after being placed in an oven in an atmosphere of 150 ° C. for 30 minutes under no tension was determined, and the heat shrinkage rate was calculated by the following formula.

[0030]

[Equation 5]

Example 1 A polyester resin obtained by copolymerizing 75% by weight of polyethylene terephthalate resin having an intrinsic viscosity of 0.62 as a raw material with dimethyl terephthalate as a dicarboxylic acid component and butanediol and polytetramethylene glycol as a glycol component in a molar ratio of 85:15. 5% by weight of elastomer, 15% by weight of general-purpose polystyrene with a melt flow index of 2.0 g / 10 minutes, 5% by weight of anatase type titanium dioxide having an average particle size of 0.3 μm as the raw material of the A layer, and polyethylene as the raw material of the B layer. 60% by weight of terephthalate resin,
40 wt% of anatase type titanium dioxide was melt extruded from a T-die at 290 ° C. by separate twin screw extruders, electrostatically adhered and solidified on a cooling rotary roll, and each layer had B / A / B = 15. An unstretched sheet of a / 220/15 μm polymer mixture was obtained. Subsequently, the unstretched sheet was longitudinally stretched 3.5 times at 83 ° C. by a roll stretching machine, and then horizontally stretched 3.5 times at 130 ° C. by a tenter and then 23 times.
Heat treatment was carried out at 5 ° C. with 4% relaxation to obtain a polyester film containing a large number of cavities inside. Thickness is B / A
/B=1.5/22/1.5 μm. The void content of the entire obtained film was 20% by volume.

The apparent specific gravity is 1.18 and the light transmittance is 15.
%, Thickness 25 μm, gloss 28% whiteness 83, film longitudinal and transverse tensile strength 13/13 k, respectively
g / mm ² Thermal contraction rate is 1.1 / 0.7% in both length and width
Met. As a basic dye on one side of this film 3-
Diethylamino-6-methyl-7-phenylaminofluorane, 4,4'-isopropylidenediphenol as a colorant, amorphous silica on fine particles together with oxidized precipitate,
The coating liquid dispersed in water was applied and dried so that the dry weight was 7.0 g / m ² , to prepare a coated film. The coated film was wound up, passed through a heat-sensitive handy printer, and recorded. The letters also looked clear.

Comparative Example 1 A handy printer paper was obtained in the same manner as in Example 1 except that the amount of titanium dioxide in the layer B was changed to 5% by weight. Apparent specific gravity is 1.11 and light transmittance is 32.
%, Thickness 25 μm, gloss is 75% whiteness 73, tensile strength in the longitudinal and transverse directions of the film is 16 kg / m, respectively.
It was m ² . The letters were unclear and not at a practical level.

Example 2 First, general-purpose polystyrene having a melt flow index of 2.0 g / 10 min and rutile titanium dioxide (TR made by Fuji Titanium, which had been subjected to silane coupling treatment with an average particle size of 0.3 μm).
-700S) was preliminarily kneaded at a weight ratio of 1: 1 with a twin-screw extruder at 240 ° C to prepare masterbatch pellets I. Next, a master batch pellet II was prepared in the same manner with a polyethylene terephthalate resin having an intrinsic viscosity of 0.62 and an anatase type titanium dioxide treated with alumina at a weight ratio of 95: 5. A mixture of this masterbatch pellet I and polyethylene terephthalate in a weight ratio of 26:74 was used as a raw material for layer A, and a masterbatch pellet was prepared.
II was used as the raw material for the B layer. At this time, the temperature of the extruder for the layer A was set to 250 ° C. at the position closest to the raw material feeding part, and gradually raised to 295 ° C. at the melting part. The kneading was carried out for about 10 minutes in the melting part, and the tip of the screw was kept at 290 ° C. After that, the melt line temperature was gradually lowered to finally reach 280 ° C. in the T-die.

The temperature of the layer B was set such that the temperature of the extruder was 250 ° C. at the position closest to the raw material feeding part, and was gradually raised to a maximum of 285 ° C. in the melting part. The kneading was carried out for about 1 minute in the melting section, and the temperature at the tip of the screw was adjusted to 280 ° C. After that, the raw material was supplied to the melt line at the same temperature as it was, joined to both sides of the A layer immediately before the T-die, and supplied to the T-die as it was. After that, it electrostatically adheres to the cooling rotary roll and solidifies, and each layer is B / A / B = 30 /
An unstretched sheet of 190/30 μm polymer mixture was obtained. At this time, the T-die slit spacing was 0.9 mm, and the average flow velocity of the melt of the polymer mixture in that portion was 8.8 m /
It was seconds. Subsequently, the unstretched sheet was longitudinally stretched 3.5 times at 83 ° C. by a roll stretching machine, and then continuously stretched by a tenter.
The film was transversely stretched 3.5 times at 45 ° C. and then heat-treated at 235 ° C. while being relaxed by 4% to obtain a polyester film containing a large number of cavities inside. The thickness is B / A / B = 3/19 /
It was 3 μm. The porosity of the surface layer of the layer A of the obtained film was 2% by volume, and the whole was 21% by volume. The portion with few cavities was present from the surface layer to a depth of about 3 μm. The surface strength of the void-containing film obtained in this example was class 1.

When the cross section of the unstretched sheet of the polymer mixture of this example was observed with a scanning electron microscope, the average particle diameter of polystyrene dispersed in the central portion was 5.0 μm, whereas the dispersion in the vicinity of the surface layer was small. The average particle size was 0.7 μm. Further, the polystyrene existing at the interface between the A layer and the B layer was in the form of threads. The apparent specific gravity is 1.15, the porosity of the surface layer of the layer A is 2% by volume, and the average porosity of the whole is 21% by volume.
The light transmittance is 15%, the thickness is 25 μm, the whiteness is 81, the gloss is 45, the tensile strength in the longitudinal and transverse directions of the film is 13/13 kg / mm ² , and the thermal shrinkage is 1.2 / 0.6.
%Met. The obtained film contained a large amount of titanium dioxide not only in polyethylene terephthalate, which is a cavity developing agent, but also around polystyrene and in polystyrene. Post-treatment was carried out in the same manner as in Example 1, and the same result was obtained when used.

[0037]

INDUSTRIAL APPLICABILITY The void-containing polyester film of the present invention has the same lightness, flexibility, matteness and drawability as the void-containing polyester film obtained by using conventional polystyrene or polyolefin as a void-developing agent. In addition to having the above properties, it has an effect that it has high concealing property and good hand-cutting property even if it is thin as compared with the conventional film. Therefore, the void-containing polyester film of the present invention can be used as a handy printer paper.

Claims (2)

[Claims] 1. Inorganic particles are mixed with polyester and / or thermoplastic resin incompatible with the polyester is mixed and extruded,
Oriented at least uniaxially and has a thickness of 10 μm or more and 40 μm
Hereinafter, a polyester film for a handy printer, which has a light transmittance of 30% or less and a whiteness of 75 or more. 2. An incompatible thermoplastic resin is mixed with polyester, melted, extruded, and oriented at least uniaxially to thereby contain a large number of fine voids therein and have an apparent specific gravity of 1.
It is 0 or more and 1.3 or less, The polyester film of Claim 1 characterized by the above-mentioned.