JP2003118246A - White laminated polyester film for thermal transfer recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a white laminated polyester film for thermal transfer recording, which is excellent in whiteness, printability and antistatic properties and, also in light resistance and the adhesion durability of an image. SOLUTION: This white laminated polyester film for thermal recording is formed by laminating an inorganic particle-containing polyester layer (A) on at least one side of a fine bubble-containing polyester layer (B) and has a specific weight of 0.6 to 1.1. On at least one side of the film, a coating layer, a surface specific resistance measured from the coating surface side of which is 10<11> Ω/(square) or less and the pH of which is 4 to 10, is provided.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a white laminated polyester film. More specifically, the present invention is excellent in whiteness, antistatic property, printing property,
The present invention relates to a white laminated polyester film for heat-sensitive transfer recording, which is suitable as a receiving sheet base material for heat-sensitive transfer recording, which exhibits high-sensitivity characteristics and is excellent in processability such as crease resistance.

[0002]

2. Description of the Related Art As one of recording methods in a hard copy technique, a heat-sensitive transfer recording method has attracted attention because it has characteristics such as non-impact, easy operation and maintenance, low cost and miniaturization. In this thermal transfer recording method, a transfer sheet (ink ribbon) having an ink layer that is a color material-containing layer and a receiving sheet are superposed, and melted or sublimated according to the heating of the thermal head from the ink ribbon side to transfer. In this method, the coloring material-containing component or the coloring material is transferred in the form of fine dots on the receiving sheet to print. Conventionally, as a receiving sheet base material used in such a thermal transfer recording method, a white polyester film containing inorganic fine particles such as titanium oxide, calcium carbonate or barium sulfate in polyester or a resin incompatible with polyester is used. Has been applied. In general, a receiving layer for enhancing the printing function is provided on these white polyester films to form a receiving sheet for thermal transfer recording. Furthermore, there is a demand for a white polyester film having high whiteness, which improves the accuracy of printing and recording, enhances the sharpness of a printed image, and gives a more luxurious appearance. In order to meet such a demand, a white polyester film in which a plurality of types of the above-mentioned inorganic fine particles are added together, a white polyester film in which inorganic fine particles and an incompatible resin are added together are known. As such a white polyester film, for example, JP-A-4-153232 and JP-A-6-322153 are disclosed.

[0003]

However, in recent years, as practical characteristics, higher sensitivity and antistatic property (receptive sheets are less likely to stick to each other due to static electricity, and dust and dust are less likely to adhere to the surface of the receptive sheet), There is a strong demand for excellent processability and printing characteristics such as crease crease properties. Thus, the characteristics required for the film are complicated and diversified, and the required level is high.

As a method of solving these problems, for example, a means of incorporating an antistatic agent as a method of imparting antistatic properties is considered. However, simply implementing the method of containing an antistatic agent has a limit in antistatic property itself, and it is impossible to satisfy all other requirements such as printing characteristics, high sensitivity, and processability. there were.

An object of the present invention is to provide an excellent white laminated polyester film for heat-sensitive transfer recording, which satisfies the above-mentioned various high-level requirements.

[0006]

To achieve this object, the white laminated polyester film for thermal transfer recording of the present invention contains inorganic particles on at least one side of a polyester layer (B) containing fine bubbles. A laminated polyester film having a specific gravity of 0.6 to 1.1 provided with a polyester layer (A), wherein a coating layer is provided on at least one surface, and the surface resistivity measured from the coating surface side is 10
^A white laminated polyester film for thermal transfer recording, which has a resistance of ¹¹ Ω / □ or less and a PH of 4 to 10.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The white laminated polyester film for heat-sensitive transfer recording of the present invention is basically composed mainly of polyester.

The polyester in the present invention is a general term for polymers having an ester bond as the main bonding chain of the main chain, but from the viewpoint of heat resistance, film-forming property, etc., ethylene terephthalate and / or ethylene naphthalate units are mainly used. The constituent component is preferable, and the melting point of polyester is 21.
The temperature is preferably 0 ° C to 280 ° C, more preferably 220 to 270 ° C.

As the polyester used in the present invention, polyethylene terephthalate and polyethylene naphthalate are particularly preferably used because of their excellent strength, heat resistance, water resistance and chemical resistance.

The polyester of the present invention may contain other copolymerization components as long as the characteristics are not impaired. Examples of the dicarboxylic acid component include diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium sulfoisophthalic acid, phthalic acid, aromatic dicarboxylic acids such as isophthalic acid, oxalic acid,
Aliphatic dicarboxylic acids such as succinic acid, eicoic acid, adipic acid, sebacic acid, dimer acid, dodecanedioic acid, maleic acid, fumaric acid, alicyclic dicarboxylic acids such as cyclohexyne dicarboxylic acid, p-oxybenzoic acid, etc. Examples thereof include polyfunctional acids such as oxycarboxylic acid, trimellitic acid, and pyromellitic acid. On the other hand, as the glycol component, for example, aliphatic glycols such as propanediol, butanediol, pentanedyl, hexanediol, neopentyl glycol, and triethylene glycol,
Examples thereof include alicyclic glycols such as cyclohexane dimethanol, aromatic glycols such as bisphenol A and bisphenol S, diethylene glycol and polyalkylene glycol. Further, a polyether such as polyethylene glycol or polytetramethylene glycol may be copolymerized. Particularly, it is preferable to use an appropriate amount of a polyester obtained by copolymerizing diethylene glycol, polyethylene glycol, and polytetramethylene glycol as a glycol component, because a fine dispersion effect is exhibited when the polyester contains an incompatible thermoplastic resin. it can.

In the present invention, a polyester obtained by copolymerizing a polyalkylene glycol with the polyester layer (A) is used in order to improve antistatic property and image durability, and further improve processability, for example, crease resistance. Polyethylene glycol or polytetramethylene glycol is particularly preferable as the polyalkylene glycol to be copolymerized. The amount of the copolymerized polyester added is preferably as follows in terms of polyalkylene glycol. That is, polyester (A)
The polyalkylene glycol is preferably added in an amount of 0.1 to 1.5% by weight, more preferably 0.3 to 1.0% by weight, based on the total weight of the polymer constituting
Is. These are because the following effects are exhibited by including the polyester copolymerized with polyalkylene glycol in the polyester (A) layer. That is, the compatibility with the antistatic layer is increased and the coating property is dramatically improved, and as a result, the antistatic effect is improved. Further, the adhesiveness is improved, and the component on the acidic side, which is considered to be an inhibitory factor for the printing characteristics, is positively coordinated to the polyester (A) layer, whereby the effect of improving the printing characteristics is also exhibited.
Especially when providing a coating layer on an in-line coat described later,
Since the antistatic layer is uniformly provided on the film surface by transverse stretching, its effect is enhanced. This is because flexibility is imparted, the followability during processing is improved, and further the adhesiveness with the polyester (B) layer is improved, and the like.

The dicarboxylic acid component and the glycol component may be used in combination of two or more kinds, and may be used by blending two or more kinds of polyester. Further, two or more layers may be coextruded and used as a laminated film. Further, in this polyester, if necessary, appropriate additives such as heat resistance stabilizers, oxidation resistance stabilizers, organic slippery agents, organic fine particles, and fillers are added as long as the effects of the present invention are not impaired. Agents, nucleating agents, dyes, dispersants, coupling agents and the like may be added.

The white laminated polyester film of the present invention has a polyester layer (A) containing inorganic particles on at least one side of the polyester layer (B) containing fine bubbles.
It is a laminated structure of two or more layers having. The polyester layer (B) is required to be a layer containing fine air bubbles. By containing fine air bubbles inside, the polyester layer (B) has a heat insulating effect against heating of the thermal head during thermal transfer recording. As a result, heat can be efficiently transferred to the printed portion. Further, the cushioning property enhances the adhesion between the thermal head and the printing surface, so that the heat transfer to the printing portion becomes more uniform, more efficient, and more sensitive.

As a method of containing fine bubbles in a polyester film, (1) a polyester is mixed with a foaming agent and foamed by heating during extrusion or film formation or foamed by chemical decomposition to form bubbles. Method, (2)
A method of adding a gas or a vaporizable substance during extrusion of polyester, (3) adding a thermoplastic resin (incompatible resin) incompatible with the polyester to the polyester, and uniaxially or biaxially stretching it Generally, a method of generating various bubbles, (4) a method of adding a large amount of bubble-forming inorganic fine particles instead of the incompatible resin, and the like are used. Any method may be used as long as it is within the scope of the present invention, but film-forming property, easiness of adjusting the amount of bubbles contained in the film, and formation of finer and more uniform-sized bubbles. The use of the incompatible resin (3) is particularly preferable from the viewpoints of easiness and lightness.

The fine air bubbles in the present invention can contribute to imparting heat insulating property and cushioning property to the film itself for improving sensitivity, and are produced by using the incompatible resin contained in the polyester as a core. Most preferably, Furthermore, when the cross-section (thickness direction) of the polyester layer (B) is observed by a scanning electron microscope (SEM) or a transmission electron microscope (TEM), the cross-sectional area of the bubble portion (however, the non-nucleus that becomes the nucleus of bubble generation is preferably has an average value of the compatible resin portion is excluded) is 1 to 25 m ^2, more preferably 1.5~20μm ^2,
Further, it is preferably ² to 15 μm ² .

The incompatible resin referred to in the present invention is a thermoplastic resin other than polyester, and is a thermoplastic resin which is incompatible with the polyester, and is dispersed in the polyester in the form of particles, A resin having a large effect of forming bubbles in the film by stretching is preferable. More specifically, the incompatible resin is a system obtained by melting the polyester and the incompatible resin by a known method, preferably,
When measured by a differential scanning calorimeter (DSC), dynamic viscoelasticity measurement, etc., in addition to the glass transition temperature corresponding to polyester (hereinafter abbreviated as Tg), T corresponding to the incompatible resin
g is the resin observed.

The melting point of such an incompatible resin is lower than that of polyester and higher than the temperature (heat treatment temperature) at which the film is heat-fixed and oriented during film formation. preferable. From this point, among the incompatible resins, polyethylene, polypropylene, polybutene, polyolefin resins such as polymethylpentene,
Polystyrene resin, polyacrylate resin, polycarbonate resin, polyacrylonitrile resin, polyphenylene sulfide resin, fluororesin, etc. are preferably used. These incompatible resins may be homopolymers or copolymers, and two or more incompatible resins may be used in combination. Of these, polyolefin resins such as polypropylene and polymethylpentene having a small critical surface tension are preferable, and polymethylpentene is most preferable. Since polymethylpentene has a relatively large difference in surface tension with polyester and has a high melting point, it is characterized by a large effect of forming bubbles per addition amount, and is particularly preferable as an incompatible resin.

The content of the incompatible resin in the polyester layer (B) is preferably 1 to 35% by weight, more preferably 2
It is preferably -30% by weight, more preferably 3-25% by weight. If the added amount is less than the above range, it may be difficult to improve the whiteness and hiding properties of the film, while if the added amount is more than the above range, film breakage or the like tends to occur during stretching. Therefore, productivity may decrease.

Further, in the polyester layer (B) of the present invention, since the dispersed diameter of the incompatible resin is small, the bubbles generated by the stretching can be made finer, and as a result, the whiteness and film-forming property of the film are improved. Since it can be improved, it is more preferable to add a dispersant in addition to the polyester and the incompatible resin. As the dispersant having the above-mentioned effects, an olefin polymer or copolymer having a polar group such as a carboxyl group or an epoxy group or a functional group reactive with polyester, diethylene glycol, polyalkylene glycol, a surfactant A heat-adhesive resin or the like can be used. Of course, these may be used alone or in combination of two or more kinds. As a method of adding the dispersant, a blended mixture with a polyester, or copolymerization such as random copolymerization or block copolymerization can be adopted. Further, it may be a partial copolymerization which is an intermediate state between the two.

The addition amount of the dispersant in the present invention is 0.0
5 to 10% by weight is preferable, and 0.1 to 7 is more preferable.
%, Even more preferably 0.2-5% by weight. If the addition amount is less than 0.05% by weight, the effect of making bubbles fine may be reduced. On the other hand, if the addition amount is more than 10% by weight, the effect of adding the incompatible resin becomes small, and problems such as a decrease in whiteness and an increase in cost are likely to occur.

Particularly in the present invention, from the viewpoint of the thermal stability of the dispersant, it is preferable to add the dispersant in the form of copolymerized polyester, and above all, it is preferable to add the polyester copolymerized with polyalkylene glycol, As the polyalkylene glycol to be copolymerized, polyethylene glycol or polytetramethylene glycol is particularly preferable. The amount of copolymerized polyester added is
It is preferable to add as follows in terms of polyalkylene glycol. That is, it is preferable to add the polyalkylene glycol in an amount of 0.2 to 5% by weight based on the total weight of the polymer constituting the polyester (B).
It is more preferably 0.3 to 2% by weight.

In the present invention, the polyester layer (B) is further stabilized by containing an antioxidant in an amount of preferably 0.05 to 1.0% by weight, more preferably 0.1 to 0.5% by weight. It is possible to carry out the polymer extrusion and film formation. As the antioxidant, a hindered phenol-based antioxidant is particularly preferable from the viewpoint of dispersibility.

In the present invention, the inorganic particles used in the polyester layer (A) containing the inorganic particles may or may not have the ability to form bubbles, for example, wet and dry silica, colloidal silica. , Aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, magnesium carbonate, zinc carbonate, titanium oxide, zinc oxide (zinc white), antimony oxide, cerium oxide, zirconium oxide, tin oxide, lanthanum oxide, magnesium oxide Use barium carbonate, zinc carbonate, basic lead carbonate (lead white), barium sulfate, calcium sulfate, lead sulfate, zinc sulfide, mica, titanium mica, talc, clay, kaolin, lithium fluoride and calcium fluoride. You can

The average particle diameter of the inorganic fine particles in the present invention in polyester is preferably 0.05 to 10 μm, more preferably 0.1 to 3 μm. If the average particle size of the inorganic fine particles is outside the above range, the inorganic fine particles may have poor uniform dispersibility due to aggregation or the like, or the particles themselves may reduce the gloss or smoothness of the film surface, which is not preferable.

The amount of the inorganic fine particles added to the polyester layer (A) is preferably 1 to 35% by weight, more preferably 2 to 30% by weight, and further preferably 3 to 25% by weight. preferable. When the added amount is less than the above range, it is difficult to improve properties such as handleability, processability, whiteness of the film, and hiding property (optical density). Conversely, when the added amount is more than the above range, Not only tends to reduce the gloss or smoothness of the film surface, but also causes problems such as film breakage during stretching and powder generation during post-processing. As the inorganic particles used from these points, titanium oxide, wet and dry silica, colloidal silica, calcium carbonate, aluminum silicate are particularly suitable, but among them titanium oxide, particularly anatase type titanium oxide from the viewpoint of improving whiteness. Is preferred.

Furthermore, in the present invention, the inorganic particles contained in the polyester layer (A) are titanium oxide, and the titanium oxide is contained in the polyester layer (B) as well, so that the expression (1) is satisfied. Of the film, the rigidity of the film itself, and the processability, for example, crease resistance. 5 ≦ Ta / Tb ≦ 90 (1) Here, Ta represents the titanium oxide concentration (% by weight) in the polyester layer (A), and Tb represents the titanium oxide concentration (% by weight) in the polyester layer (B).

In the white laminated polyester film of the present invention, the surface resistivity measured from the polyester layer (A) side is required to be 10 ¹¹ Ω / □ or less, and the surface resistivity is more preferably 10 or less. ¹⁰ Ω / □ or less. The smaller the surface resistivity is, the better the antistatic property and the sheet feeding property are. When the surface resistivity is more than 10 ¹¹ Ω / □, the antistatic property is insufficient, and therefore the receiving layer is provided on the film surface. In the case of using the receiving sheet as a sheet, problems such as sticking of the receiving sheets to each other due to static electricity or paper clogging during printing, or adhesion of dust or dust to the surface of the receiving sheet are likely to occur. Regarding the lower limit, it is most preferable that there is no electrical resistance, but in reality it is 10 ^-2.
Ω / □ or more.

Further, in the present invention, the surface PH of the coating layer needs to be 4 to 10. This is because if the surface PH is less than 4 or more than 10 when the receiving layer is arranged on the surface of the coating layer, the characteristics when printed are deteriorated. Especially when the surface PH is on the acidic side of less than 4, depending on the dye,
This is because a phenomenon such as discoloration occurs, which poses a practical problem and the printing characteristics are significantly reduced. In the present invention, PH is preferably 4.5 to 9 from these points, more preferably 5
~ 8.

As a method for satisfying the above-mentioned antistatic property and surface PH, a method of incorporating an antistatic agent in the polyester layer (A) or the polyester layer (A)
Although a method of providing a coating layer on the top surface can be used, the latter method is more preferably adopted because of its high effect of imparting antistatic property and wide range of selection of antistatic agent.

When a coating layer is provided on the polyester layer (A), either a layer containing an antistatic agent alone or a layer containing a binder resin can be used. Particularly, the latter layer containing a binder resin is used. This is more preferable in that the effect of improving the adhesiveness with the receiving layer can be expected when a receiving sheet for thermal transfer recording is provided with a receiving layer on the film.

As the above antistatic agent, for example, ionic polymer compounds, surfactants, conductive inorganic fine particles, inorganic electrolytes, organic complex salts and the like can be preferably used. Among these, ionic polymer compounds are preferably used in terms of coating properties and miscibility with binder resins and other compositions. Here, the ionic polymer compound is
It is a generic term for polymer compounds having an ionic group as a main chain, a side chain, or a pendant of the main chain.

As the ionic group, anionic groups such as sulfonates, carboxylates, phosphates, alkyl sulfonates, alkyl phosphates, etc., alkyl trimethyl ammonium salts, lauryl trimethyl ammonium chloride, alkyl pyrrolidinium A cationic group which is a compound whose main component is a quaternary ammonium salt such as a salt,
Non-ionic groups, long-chain aliphatic groups, quaternary ammonium-type nitrogen and carboxyl groups, which are compounds containing polyethers, polyhydric alcohols, polyoxyethylene alkylamines, polyoxyethylene fatty acid esters, etc. as main components Alternatively, a zwitterionic group such as a compound having a sulfone group can be used.

Specific examples thereof include polymer compounds having an ionic group in the main chain, such as a pyrrolidinium ring,
A polymer compound having a piperidinium ring or the like in the main chain, or a polymer compound containing a compound having an unsaturated bond in these as a copolymerization component can be used.

As the polymer compound having an ionic group in the side chain, for example, a homopolymer of acrylic acid, methacrylic acid, styrene or the like and / or saturated hydrocarbon such as polyethylene or polypropylene as another component, Unsaturated hydrocarbons such as polyacetylene, copolymers such as alkylene oxides are the main chains, and ionic groups such as phosphates, sulfonates, vinyl sulfonates, carboxylates, quaternary ammonium salts are side chains. A polymer compound having the same can be used.

In the present invention, among the ionic polymer compounds, a polymer compound in which the ionic group is an anionic group is particularly preferable from the viewpoint of miscibility and coatability. The above ionic polymer compounds may be used alone or
You may use it in combination of 2 or more types.

In the present invention, a sulfonic acid group and /
Or, a copolymer having a salt thereof can be preferably used because, for example, it has excellent heat resistance during recycling.
Among them, styrene sulfonic acid metal salt is preferably used, and the content of styrene sulfonic acid metal salt is preferably 10 to 40% by weight.

The copolymer having a sulfonic acid group and / or its salt that can be used in the present invention is polyvinyl sulfonic acid and / or its salt, polystyrene sulfonic acid and / or its salt, and the like.
The copolymer may be copolymerized with other copolymer components to such an extent that the characteristics are not deteriorated. Other copolymerizable components include, for example, alkyl acrylate and alkyl methacrylate (as the alkyl group, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group,
Isobutyl group, t-butyl group, 2-ethylhexyl group,
Lauryl group, stearyl group, cyclohexyl group, phenyl group, benzyl group, phenylethyl group, etc.) can be used. Further, the following monomers may be copolymerized for the purpose of imparting a crosslinkable functional group to the copolymer. As the crosslinkable functional group, a carboxyl group, a hydroxyl group, a methylol group, a sulfonic acid group, an amide group or a methylolated amide group, an amino group (including a substituted amino group), or an alkylolated amino group, a hydroxyl group, An epoxy group, an acid anhydride, etc. can be illustrated. Examples of the monomer having a crosslinkable functional group include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid,
2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, vinylsulfonic acid, styrenesulfonic acid, acrylamide, methacrylamide, N-methylmethacrylamide, N-methylolacrylamide, N- Methylol methacrylamide, dimethylaminoethyl methacrylate, and those obtained by methylating the above amino group, glycidyl acrylate, glycidyl methacrylate and the like can be used, but not limited thereto.

Further, in the present invention, a copolymer having a lithium sulfonic acid salt is preferable in terms of achieving both antistatic property and surface PH.

The binder resin may be, for example, a polyester resin, a polyacrylate resin, a polyurethane resin, a polyvinyl alcohol resin, in order to impart miscibility with the antistatic agent, coatability, and adhesion to the receiving layer. Resins such as polyvinyl butyral resins are preferred. Among these resins, especially polyester resin,
Polyacrylate resin and polyurethane resin are more preferably used. Of course, these resins may be used alone or in combination of two or more kinds or as a copolymer. Particularly, in the present invention, an acrylic resin or a polyester resin having a glass transition temperature of 10 to 80 ° C. is preferable from the viewpoints of blocking resistance, adhesiveness, and compatibility with an antistatic agent.

In the present invention, the binder resin may be used in combination with an antistatic agent, or may be used as a mixture of both, and the latter may be used in combination with the receptive layer. From the range and wide range of application,
It is more preferable. The ratio (weight ratio) of the antistatic agent to the binder resin is not particularly limited as long as it is within the range of the present invention, but is preferably 5/95 to 95/5, more preferably 10/90 to 90. It is / 10. Further, in particular, when the ionic polymer compound is mixed with the binder resin to be used, it can be mixed and used at an arbitrary ratio, but in order to more significantly express the effect of the present invention, the solid content weight is The ratio of ionic polymer compound / binder resin is preferably 40/60 to 10/90, more preferably 35/65 to 15/85. The mixing ratio is changed depending on the ionic polymer compound used, but if it is more than the above range, the adhesiveness is lowered, and if it is too little, the antistatic property is difficult to be obtained.

Further, in the laminated film according to the present invention, a crosslinking agent may be added to the ionic polymer compound and the binder resin, and they can be used by mixing them at an arbitrary ratio. In order to express more significantly, it is advisable to mix in the following ratios.

The melamine-based cross-linking agent is used in an amount of 0.2 to 0.2 relative to the resin.
Addition of 20 parts by weight is preferable from the viewpoint of improving the adhesiveness, more preferably 0.5 to 15 parts by weight, and most preferably 1 to 1
0 parts by weight is added. The amount of melamine-based crosslinking agent added is 2
If it exceeds 0 parts by weight, the adhesiveness and antistatic property tend to be lowered.

The oxazoline-based cross-linking agent is added to the resin in an amount of 0.
Addition of 2 to 20 parts by weight is preferable from the viewpoint of improving adhesiveness, more preferably 0.5 to 15 parts by weight, most preferably 1
-10 parts by weight is added. When the addition amount of the oxazoline-based crosslinking agent exceeds 20 parts by weight, the adhesiveness and antistatic property tend to be lowered.

Other additives such as a crosslinking agent, a surfactant, an antifoaming agent, a leveling agent, a heat resistance stabilizer, and an oxidation resistance stabilizer may be added to the antistatic layer as long as they do not impair the object of the present invention. Agents, organic lubricants, organic or inorganic fine particles, fillers, nucleating agents, dyes, dispersants and the like may be contained.

In the present invention, the method for forming the antistatic layer is preferably a method in which an antistatic layer-forming coating liquid is applied on the polyester layer (A) side of the white laminated polyester film and dried. Examples of the coating method of the antistatic layer-forming coating liquid include reverse (roll) coat, gravure coat, knife coat, air knife coat, roll coat, blade coat, bead coat, rotary screen coat, slot orifice coat, rod coat, Bar coat, die coat, spray coat, curtain coat, die slot coat, champlex coat, brush coat, two coat, metering blade type size press coat, bill blade coat, short dwell coat, gate roll coat, gravure reverse coat, ext. Methods such as rouge coating and extrusion coating can be used.

The coating process of the antistatic layer-forming coating liquid includes a method of coating in the film forming process of the white laminated polyester film (in-line coating), a method of coating and drying on the film after film formation (off-line coating). ), The in-line coating is a more excellent method in terms of uniform coating, thin film coating, and economical efficiency. In addition, the film before coating can be subjected to pretreatment such as corona discharge treatment and plasma treatment in advance for the purpose of improving coatability.

The liquid medium of the coating liquid for forming the antistatic layer is
Either an aqueous medium, a solvent type, or a mixed medium of both types may be used, but when the antistatic layer is provided by the in-line coating method, an aqueous type or a mixture of both types mainly composed of water is used in terms of handleability and safety such as explosion proof. The liquid medium of the system is preferably used.

The thickness of the antistatic layer is 0.005 to 10 μm.
m is preferable, and more preferably 0.01 to 5 μm. When the thickness of the antistatic layer is less than 0.005 μm,
Antistatic property tends to be insufficient. On the other hand, when the thickness of the antistatic layer is thicker than 10 μm, the coating property of the coating liquid for forming the antistatic layer may be lowered at the time of coating, or the cost may be increased and the economical efficiency may be lowered, which is not preferable.

In the present invention, the white laminated polyester film for thermal transfer recording may contain a fluorescent whitening agent in the polyester layer (A) and / or the polyester layer (B) in order to give higher whiteness. .

In the present invention, the fluorescent whitening agent has a function of absorbing ultraviolet rays in sunlight or artificial light and converting the ultraviolet rays into purple to blue visible rays to radiate them. It is a compound that promotes whiteness without reducing the lightness of the substance. As the fluorescent whitening agent, trade names “Ubitech” (Ciba Geigy), “OB-1” (Eastman), “TBO” (Sumitomo Seika Co., Ltd.), “K-Call” (Nippon Soda Co., Ltd.) , "Kayalite" (Nippon Kayaku Co., Ltd.), "Leukopoor" EGM (Client Japan Co., Ltd.) and the like can be used. Optical brightener
It is not particularly limited, and may be 1 or 2 in some cases.
Although it may be a combination of two or more species, in the present invention, the selection of a fluorescent whitening agent that is particularly excellent in heat resistance, has good compatibility with the above-mentioned polyester and can be uniformly dispersed, and has little coloring and does not adversely affect the resin. Is desirable.

The content of the optical brightening agent in the polyester layer (A) or the polyester layer (B) is 0.01.
Is preferably 1.5% by weight, and more preferably 0.03%.
It is more preferably 1% by weight, and further preferably 0.05 to 0.5% by weight. If the content of the optical brightener is less than the above range, it may be difficult to obtain a sufficient whitening effect. If the content exceeds the above range, the uniform whiteness may decrease due to the decrease in uniform dispersibility or the optical brightener itself. There may be a problem that the light resistance is likely to decrease.

The white laminated polyester film of the present invention must have a laminated constitution of two or more layers in which the polyester layer (A) is provided on at least one side of the polyester layer (B). For example, when the effect of the present invention is to be obtained with a single-layer monolayer film, film breakage is likely to occur and film formation is unstable, resulting in higher costs. In addition, when an incompatible resin is added to a single-layer single film to contain fine bubbles, dispersed particulate incompatible resin is dropped depending on the type,
The parts (drums, rolls, coaters, etc.) that come into contact with the film forming device may be contaminated during long-time film forming. This contamination may adversely affect film properties,
Regular cleaning as a countermeasure tends to cause problems such as a decrease in productivity and an increase in cost.
Therefore, a laminated structure having two or more layers is formed, and the polyester layer (A) is made to exhibit whiteness and smoothness or luster, and the polyester layer (B) is a layer excellent in various properties such as cushioning property and heat insulating property. Then, it becomes possible to satisfy all the required characteristics as the entire film.

Here, when the white laminated polyester film of the present invention has a two-layer laminated constitution having a polyester layer (A) on one side of the polyester layer (B), this is used as a receiving sheet substrate for thermal transfer recording. When used, it is preferable to provide a receiving layer on the polyester layer (A).

Therefore, the white laminated polyester film of the present invention, in which the polyester layers (A) are laminated on both sides of the polyester layer (B) to form a three-layer laminated structure, the film-forming property is further improved and the handleability is improved. It is more desirable from the standpoint that the practicality of the above can be improved, or the stability over time can be improved.

In the present invention, the type of polyester used in each of the polyester layer (A) and the polyester layer (B) may be the same or different. Particularly, when different polyesters are combined, for example, when the polyester used in the polyester layer (A) is polyethylene naphthalate and the polyester used in the polyester layer (B) is polyethylene terephthalate, the effect of improving rigidity can be obtained. preferable.
Further, when the polyester used in the polyester layer (A) is a copolyester and the polyester used in the polyester layer (B) is a homopolyester, the effect of improving the adhesion with the receiving layer or the antistatic layer can be obtained. More preferable.

In the present invention, as the method for laminating the polyester layer (A) and the polyester layer (B), a method of forming a composite by co-extrusion during melt film formation, or a method of forming films separately and then laminating Although any of the above methods may be used, the former method is more preferable in terms of cost and the like.

When the white laminated polyester film of the present invention is used as a receiving sheet substrate for heat-sensitive transfer recording, it may be used alone or may be used by laminating it with another material. Examples of the material include plain paper, high-quality paper, medium-quality paper, coated paper, art paper, cast coated paper, resin-impregnated paper, emulsion-impregnated paper, latex-impregnated paper, synthetic resin internal-addition paper, glassine paper, laminated paper, etc. Paper, synthetic paper,
A non-woven fabric, a film of another kind, or the like can be used. However, when the white laminated polyester film of the present invention is laminated with another material, it is preferably laminated on the surface opposite to the surface on which the receiving layer is provided.

As described above, the white laminated polyester film of the present invention is a laminated constitution of two or more layers in which the polyester layer (A) is provided on at least one side of the polyester layer (B), and each layer is the above-mentioned means. However, the preferable level of whitening (whiteness) is determined substantially after the laminated film is formed.

That is, as the whiteness of the white laminated polyester film for thermal transfer recording of the present invention, the whiteness measured from the polyester layer (A) side is preferably 70% or more, more preferably 80% or more, Furthermore 9
Most preferably, it is 0% or more. If the whiteness is less than 70%,
Since the whiteness is insufficient, the printed image tends to give a dark impression, which is not preferable.

On the other hand, the color tone b value measured from the polyester layer (A) side is preferably 2 or less, more preferably 1 or less, and most preferably 0 or less. When the color tone b value is larger than 2, the printed image tends to have an old impression because the film itself has a yellowish color even if the light resistance is satisfied, which is not preferable.

In the present invention, the specific gravity of the film is 0.
It is indispensable to be 6 to 1.1, and more preferably 0.7 to 1.0. If the specific gravity is less than 0.6,
This may cause deterioration of processability, film strength, and film formability. On the other hand, if the specific gravity exceeds 1.1, the cushioning property and the heat insulating property are deteriorated to deteriorate the printability, or the whiteness of the film is insufficient and the printed image tends to give a dark impression, which is not preferable.

In the present invention, the elongation Sm in the longitudinal direction of the film and the elongation St in the width direction are expressed by the formula (2) (from the viewpoint of improving workability, for example, improving crease resistance and sensitivity. 3) is preferably satisfied, more preferably 100 <Sm <200, and particularly preferably 11
0 <Sm <200. This is because the film followability in the longitudinal direction is improved, and at the same time, the elongation in the film width direction is lower than the elongation in the longitudinal direction, so that it is balanced when tension is applied in the longitudinal direction of the film, and the stress is easily uniformized. It is thought to be because. Further, since the balance is made uniform, it is possible to reduce a large load locally applied to the coating layer applied on the surface, and it is possible to prevent cracks and the like, which contributes to the development of a stable antistatic function. 5 <Sm-St <80 (2) 90 <Sm <200 (3) The thickness of the white laminated polyester film of the present invention is 10
To 300 μm is preferable, and more preferably 20 to 50 μm.
m is preferable from the viewpoint of improving the crease resistance. In addition, when the white laminated polyester film of the present invention is laminated with another material, the upper limit of its thickness is preferably 200 μm or less, more preferably 150 μm or less from the viewpoint of handleability.

The ratio of the polyester layer (B) to the total thickness (thickness of the polyester layer (B) / total thickness)
Is preferably 0.55 to 0.99, more preferably 0.6 to 0.97, and even more preferably 0.
65 to 0.95.

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

In a composite film forming apparatus having an extruder (A) and an extruder (B), in order to form the polyester layer (B), vacuum-dried polyester chips and, if necessary, vacuum-dried incompatible resin 1 chip of incompatible resin
~ 35% by weight and mix it with 260 ~ 30
It is supplied to the extruder (B) heated to 0 ° C., melted and introduced into the T-die composite die. A dispersant may be added to this raw material in an amount of 0.05 to 10% by weight, if necessary. Also,
The addition of the incompatible resin may be carried out by vacuum drying a master chip in advance. On the other hand, since the polyester layer (A) is laminated, the polyester chips and the master chip of the inorganic fine particles have 1 to 3 inorganic fine particles.
Mix so as to be 5% by weight and sufficiently vacuum dry. If necessary, an optical brightener may be added to this raw material in an amount of 0.01 to 1.5.
You may add it by weight%. Next, this dry raw material is mixed with 2
It is supplied to the extruder (A) heated to 60 to 300 ° C., similarly melted and introduced into the T-die composite die, and the extruder (A)
The polymer (1) is laminated so as to be on the surface layer (one surface) or both surface layers (both surfaces) of the polymer of the extruder (B), and coextruded into a sheet to obtain a melt-laminated sheet.

The melt-laminated sheet was subjected to a surface temperature of 10-6.
On a drum cooled to 0 ° C., static electricity is adhered and cooled to be solidified to produce an unstretched laminated film. The unstretched laminated film is guided to a roll group heated to 70 to 120 ° C., and 2 to 5 in the longitudinal direction (longitudinal direction, that is, film advancing direction).
Double stretching and cooling with a roll group of 20 to 30 ° C.

Subsequently, the polyester layer (A) side of the film stretched in the longitudinal direction is subjected to corona discharge treatment, and then the antistatic layer forming coating liquid is applied to the treated surface. While holding both ends of the film coated with this antistatic layer-forming coating liquid with clips, the film is guided to a tenter, and is 2 to 5 times in a direction (transverse direction) perpendicular to the longitudinal direction in an atmosphere heated to 90 to 150 ° C. Stretch.

The stretching ratio is 2 to 5 times in each of the length and width, and the area ratio (longitudinal stretching ratio × horizontal stretching ratio) is 6 to 5.
It is preferably 20 times. If the area ratio is less than 6 times, the whiteness and the film strength of the obtained film are insufficient, and conversely, if the area ratio exceeds 20 times, tearing tends to occur during stretching.

In order to complete the crystal orientation of the biaxially stretched laminated film thus obtained and to impart planarity and dimensional stability, it is continuously heated at 150 to 240 ° C. in a tenter.
The white laminated polyester film of the present invention can be obtained by carrying out heat treatment for 1 to 30 seconds, uniformly cooling gradually, cooling to room temperature and winding. In the heat treatment step, a relaxation treatment of 3 to 12% may be performed in the lateral direction or the longitudinal direction, if necessary. The biaxial stretching may be either sequential stretching or simultaneous biaxial stretching, and the biaxial stretching may be followed by re-stretching in either the longitudinal or transverse direction.

The white laminated polyester film of the present invention thus obtained is excellent in whiteness, antistatic property, printing property, high sensitivity property and processability such as crease resistance. Is very good at. The receiving sheet for heat-sensitive transfer recording using the white laminated polyester film of the present invention as a base material has no paper feeding trouble at the time of print recording, and the printed image is clear and does not discolor. Furthermore, dust and dirt are less likely to adhere, and the sharpness of the printed image can be maintained for a long time. Furthermore, the printing characteristics can be excellent. Therefore, the white laminated polyester film of the present invention is a film having optimum properties as a receiving sheet base material for thermal transfer recording.

[Characteristic Measuring Method and Evaluation Method] The characteristic value of the present invention is obtained by the following evaluation method and evaluation criteria.

(1) Fine air bubbles inside the film and the thickness of the polyester layer The cross section of the film is observed with a scanning electron microscope S-2100A (manufactured by Hitachi, Ltd.) at a magnification of 500 to 5,000 times. The presence or absence of the inclusion of fine bubbles was examined from the cross-sectional photograph taken in the above step. The presence / absence of bubbles is determined by calculating the average value when the average cross-sectional area of the bubble portion of the cross-sectional photograph is converted into a true circle, and if it is 1 μm ² or more, “there is a bubble”, 1
If it was less than μm ² , it was defined as “no bubbles”. However, when two or more adjacent bubbles are connected,
Calculated as one bubble. Further, the length of each polyester layer in the thickness direction was measured from the cross-sectional photograph, and the thickness of each layer was obtained by back-calculating from the magnification. In addition, the cross-sectional area of the bubble portion,
In obtaining the thickness of each polyester layer, a total of 5 cross-sectional photographs arbitrarily selected from mutually different measurement fields of view were used and calculated as an average value thereof.

(2) Whiteness With respect to the white laminated polyester film, a spectroscopic color difference meter SE-2000 type (manufactured by Nippon Denshoku Industries Co., Ltd.) was used from the side of the white polyester layer (A), according to JIS Z-8722. X-value, Y-value, Z which are tristimulus values of color under optical conditions
The value was measured and the whiteness was calculated by the following formula. Whiteness (%) = 4 × 0.847 × Z value−3 × Y value

(3) Color tone b value JIS Z-8730 measured according to the above-mentioned device and optical conditions.
It was calculated according to.

(4) A sample sample obtained by cutting a specific gravity film into a size of 50 mm × 60 mm was used as a high precision electronic hydrometer SD-120L.
(Made by Mirage Trading Co., Ltd.), JIS K-71
The measurement was performed according to Method A of 12 (substitution method in water). The measurement was carried out under the conditions of a temperature of 23 ° C. and a relative humidity of 65%.

(5) The surface specific resistance temperature was 23 ° C. and the relative humidity was 65%, and the sample was allowed to stand for 24 hours to adjust the humidity.
0 (manufactured by Advantest Co., Ltd.) is used to apply an applied voltage of 100
Measured at V. The smaller this value, the better the antistatic property.

(6) Surface PH film sample under normal conditions (23 ° C., relative humidity 65%)
After being left for 24 hours at the factory, a pH meter "COMPACT PH METER tw" manufactured by HORIBA, Ltd.
in PH ”(type B212) was used to measure the surface PH of the sample surface. Ion-exchanged water was dropped on the sensor, and a sample cut into a predetermined size so as to cover the two electrodes of the sensor part was set and measured. In addition, the measured value was performed 5 times in the automatic measurement mode, and the average value was used as the surface PH value.

(7) Sensitivity A urethane-modified polyethylene aqueous dispersion (urethane modification ratio = 20% by weight, which was emulsified by heating in an aqueous ammonia solution to form an aqueous dispersion) was diluted with water to obtain a solid content concentration. The content of 3% was used as the receiving layer forming coating liquid.

On the white laminated polyester film of the present invention, the above-mentioned coating solution for forming a receiving layer was applied by a gravure coater and then dried at 120 ° C. for 1 minute to give a receiving layer having a thickness of 0.
A receiving sheet for thermal transfer recording having a size of 1 μm was obtained.

Next, as a color printer, "Professi
onal Color Point 2 "(manufactured by Seiko Denshi Kogyo Co., Ltd.) and a dedicated CH705 (Yellow, Magenta, Cyan manufactured by Seiko Eye Supply Co., Ltd.) as an ink ribbon to form a receptive layer of the receptive sheet. 8 on the surface
A gradation test pattern was printed. Next, the printed test pattern was judged by the following method.

(Dot shape) The portions of each of the three colors of yellow, magenta, and cyan on the printed surface were observed 100 times to 300 times magnified with a reflection type optical microscope, and the shape of the printed dots was divided into the following four stages. An evaluation was performed. ⊚ or ○ was judged to be good. ⊚: All three colors have a clean circular shape and are extremely good. ◯: Good although there was a slight “chip”. Δ: “Chipped” and “crushed” are seen. Or the dots are small. X: "Chipped" and "crushed" are remarkable. Or the dots are extremely small.

(Image Quality) The printed surface was visually observed, and the brightness and impression of the printed image were evaluated according to the following four grades. ⊚ or ○ was judged to be good. ⊚: The entire image is very clear and extremely good. ◯: A clear image, which is good. Δ: The image itself is thin, or the non-printed surface is slightly discolored, so that the image has a dark impression and is inferior in image clarity. X: The image itself is very thin, or the non-printed surface is discolored, so the overall image has a very dark impression and is completely defective.

(8) Paper Feedability According to the method of the above (7), a receiving sheet produced by using the white laminated polyester film of the present invention is cut out into A4 size, and then 50 sheets are stacked and stacked in the same manner as above. Continuous printing was performed. At this time, the following three-stage evaluation of the paper feeding property was performed according to the number of paper feeding errors such as paper jam. Good was judged to be good. ◎: 0 times ○: 1-2 times ×: 3 times or more.

(9) Printing Characteristics The following leuco dye type thermal recording ink was applied onto the film of the present invention by using a gravure roll so that the ink layer thickness after drying would be 5 μm.

A thermal head was used for the film provided with this ink layer, the applied voltage and the pulse width were adjusted so that the applied energy was 30 mJ / m ^2, and a printing test was conducted.

At this time, the state of the ink layer was observed, and the change in the color of the background portion, which is originally transparent, was used as an index of printing characteristics. At this time, those with no discoloration in the background portion were marked with "⊚", those with a slight color change but with no practical problems were marked with "○", and those with a slight discoloration were marked with "X", which were used as indicators of printing characteristics.

"Leuco dye type thermal recording ink" -Microcapsules containing leuco dye 8-diethylamino-11- (2-methoxycarbonylphenyl) -benzo-α-xanthene was used as a leuco dye of oxidation coloring type, and polyvinyl alcohol was used. (Nippon Synthetic Chemical Industry Co., Ltd. "Gothenol" GM-14L) and a 1: 3 adduct of trimethylolpropane and xylylene diisocyanate ("Takenate" D-110 manufactured by Takeda Pharmaceutical Co., Ltd.)
N) as microcapsule wall material, average particle size 1.2
A μm microcapsule solution was prepared. Microcapsules containing an oxidizing agent and a photo-reducing agent, chloranil as the oxidizing agent, and 2-methyl-1,4-as the reducing agent.
Using naphthokin, in the same manner as above, average particle size 1 μm
A microcapsule liquid of・ Microcapsule liquid containing the above leuco dye,
A microcapsule liquid containing an oxidizing agent and a photoreducing agent, and a polyvinyl alcohol (“Gosenol” GM-14L manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) liquid were used at a solid content weight ratio after drying of 30:45:15. Was adjusted so that a leuco dye type thermal recording ink was obtained.

(10) Folding wrinkle resistance film A slit-like tape having a width of 10 mm was prepared (folding wrinkle resistance test sample a). Further, a layer of a low Tg polyester resin (Tg = 4 ° C., softening point = 114 ° C.) was applied to this film so as to have a thickness of about 1 μm, and then a fine paper of 150 μm in thickness was applied at a temperature of 110 ° C. by a laminator. The pieces were evenly attached and similarly slit into a width of 10 mm was prepared (crease resistance wrinkle resistance test sample b). These samples were run on a stainless steel guide pin (outer diameter: 10 mm) using a tape running tester: running conditions: speed 1 m / min, wrap angle 90 degrees, delivery side tension 60 g.
After wrapping with, the film was unwound and the surface condition was observed with a stereoscopic microscope 25 times, and the following evaluations were performed. ○ The above was judged to be good. ⊚: All samples have no wrinkles on the surface. ⊚: 1-2 samples have several wrinkles on the surface, but no wrinkles on others. A: There are 3 to 4 samples in which several wrinkles can be confirmed on the surface, but the others have no wrinkles. Δ: Partially wrinkled X: There are innumerable wrinkles.

(11) Elongation Using a tensilon (tensile tester), the elongation at break was measured and measured at a tensile speed of 300 mm / min, a width of 10 mm and a sample length of 100 mm to obtain the elongation.

[0090]

The present invention will be described with reference to the following examples.
The present invention is not limited to these.

(Example 1) Extruder (A) and extruder (B)
In a composite film forming apparatus having a polyester layer (A)
To form polyethylene terephthalate (hereinafter,
(Abbreviated as PET) 7% by weight of anatase type titanium oxide fine particles having an average particle diameter of 0.2 μm and 0.15% by weight of a fluorescent whitening agent “OB-1” (manufactured by Eastman) were added to a chip. The raw material was vacuum dried at 180 ° C. for 3 hours, then supplied to the extruder (A) side, melted at 280 ° C. by a conventional method, and introduced into the T-die composite die.

On the other hand, in order to form the polyester layer (B), 10 wt% of polymethylpentene having a melting point of 235 ° C. (hereinafter abbreviated as PMP) was added to the PET chip, and polyethylene glycol having a molecular weight of 4,000 was used as a dispersant. (Hereinafter, abbreviated as “PEG”) 5% by weight of copolymerized PET was added so that the amount of PEG was 1% by weight based on the entire resin constituting the polyester (B) layer.
After vacuum drying at 0 ° C. for 3 hours, it was supplied to the extruder (B) side, melted at 280 ° C. by a conventional method, and similarly introduced into the T-die composite die. Then, the polyester layer (A) was joined so as to be laminated on both surface layers of the polyester layer (B) in the die, and then coextruded into a sheet to obtain a melt-laminated sheet. Then, the molten laminated sheet is subjected to a surface temperature of 25
An unstretched laminated film was obtained by closely cooling and solidifying by a static charge method on a cooling drum kept at ℃. Subsequently, the unstretched laminated film was preheated by a group of rolls heated to 85 ° C. according to a conventional method, and then stretched 1.1 times in the longitudinal direction (longitudinal direction) using a heating roll at 95 ° C., and 2 times main stretching,
It cooled with the roll group of 25 degreeC, and the uniaxially stretched film was obtained.
Further, subsequently, the uniaxially stretched film was subjected to corona discharge treatment in air, and the treated surface was coated with the following antistatic layer-forming coating liquid by a bar coating method using a metering bar.
While holding both ends of the uniaxially stretched film coated with this antistatic layer-forming coating liquid with clips, the uniaxially stretched film is introduced into a preheating zone in a tenter, preheated and dried at 110 ° C., and then continuously 1
Direction perpendicular to the longitudinal direction (horizontal direction) in a heating zone of 25 ° C
Was stretched 3.5 times. Further subsequently, a heat treatment at 210 ° C. was performed in a heat treatment zone in the tenter, and further, a relaxation treatment was performed in the transverse direction at 5% at the temperature, a heat treatment was performed at 150 ° C., and then the film was uniformly annealed and wound. A white laminated polyester film having a 0.1 μm-thick antistatic layer provided on a 50 μm-thick polyester film having a polyester layer (A) of 3.5 μm on one side and a polyester layer (B) of 43 μm on one side was obtained. Further, by observing the cross section of the white laminated polyester film with an SEM, it was confirmed that the polyester layer (B) contained fine bubbles. The fine bubbles are formed around the PMP dispersed in the form of particles as the core, and the major axis is an elliptical shape with the stretching direction and the minor axis being the film thickness direction, and the average value of the cross-sectional area is It was 4.5 μm ² .

The properties of the thus obtained white laminated polyester film are as shown in Table 1, which shows whiteness, antistatic property, printing property, high sensitivity property, and good workability of crease resistance. It can be seen that it is excellent and is excellent as a receiving sheet base material for thermal transfer recording.

[Antistatic Layer Forming Coating Liquid] (A) Antistatic Agent: Polystyrenesulfonic Acid Sodium Salt Water Dispersion (Molecular Weight = 20,000) (B) Binder Resin: Acrylic Emulsion (Acrylic Component: Methyl Methacrylate / Ethyl Acrylate /
Acrylic acid / N-methylol acrylamide = 60/3
8/1/1 (wt%) copolymer, glass transition temperature 60
C.) The above (A) / (B) was mixed at a solid content weight ratio of 30/70 and diluted with water to a solid content concentration of 4% by weight.

(Example 2) A white laminated polyester film was obtained in the same manner as in Example 1 except that the coating liquid for forming an antistatic layer was changed to the following.

The characteristics of the obtained white laminated polyester film are as shown in Table 1, and the whiteness, antistatic property, and
It can be seen that it is excellent as a receiving sheet base material for heat-sensitive transfer recording because it exhibits printing characteristics and high sensitivity characteristics and has a good level of workability of crease resistance.

[Antistatic Layer Forming Coating Liquid] (A) Antistatic Agent: Lithium Polystyrenesulfonate Salt Water Dispersion (Molecular Weight = 20,000) (B) Binder Resin: Acrylic Emulsion (Acrylic Component: Methyl Methacrylate / Ethyl Acrylate /
Acrylic acid / N-methylol acrylamide = 60/3
8/1/1 (wt%) copolymer, glass transition temperature 60
C.) (C) Melamine-based cross-linking agent The above (A) / (B) / (C) in a solid content weight ratio of 30/7
The mixture was mixed with 0/5 and diluted with water to a solid content concentration of 4% by weight.

(Example 3) As raw materials to be supplied to the extruder (B) of Example 1, PET chips were used in an amount of 10% by weight, and anatase-type titanium oxide fine particles having an average particle diameter of 0.2 µm were added in an amount of 0.25% by weight. , A molecular weight of 4, as a dispersant,
The copolymerized PET containing 5% by weight of polyethylene glycol (hereinafter abbreviated as PEG) of 000 was added so that PEG was 1% by weight with respect to the entire resin constituting the polyester (B) layer. A white laminated polyester film was obtained in the same manner as in Example 1 except that the coating liquid for forming an antistatic layer was changed to the following.

The characteristics of the obtained white laminated polyester film are as shown in Table 1, and the whiteness, antistatic property, and
It can be seen that it is excellent as a receiving sheet base material for heat-sensitive transfer recording because it exhibits printing characteristics and high sensitivity characteristics and has a good level of workability of crease resistance.

[Antistatic Layer Forming Coating Liquid] (A) Antistatic Agent: Lithium Polystyrenesulfonate Water Salt Dispersion (Molecular Weight = about 70,000) (B) Binder Resin: Acrylic Emulsion (Acrylic Component: Methyl Methacrylate / Ethyl Acrylate /
Acrylic acid / N-methylol acrylamide = 60/3
8/1/1 (wt%) copolymer, glass transition temperature 60
C.) The above (A) / (B) was mixed at a solid content weight ratio of 30/70 and diluted with water to a solid content concentration of 4% by weight.

Example 4 As a raw material to be fed to the extruder (A) of Example 1, PET chips were used and the average particle size was 0.2.
7 μ% of anatase-type titanium oxide fine particles of μm and 0.15 wt% of a fluorescent whitening agent “OB-1” (manufactured by Eastman) were added, and PEG having a molecular weight of 4,000 was further added.
Example 1 except that the copolymerized PET containing 5% by weight of PEG was added so that PEG was added in an amount of 0.6% by weight with respect to the entire resin constituting the polyester (A) layer.
A white laminated polyester film was obtained in the same manner as in.

The characteristics of the obtained white laminated polyester film are shown in Table 1, and the whiteness, antistatic property, and
It can be seen that it is excellent as a receiving sheet base material for heat-sensitive transfer recording because it exhibits printing characteristics and high sensitivity characteristics and has a good level of workability of crease resistance.

(Example 5) A white laminated polyester was obtained in the same manner as in Example 1 except that the film production conditions and the antistatic layer were as follows.

That is, the unstretched laminated film was preheated by a group of rolls heated to 85 ° C., and then finely stretched 1.1 times in the longitudinal direction (longitudinal direction) using a heating roll at 95 ° C.
The main stretching was performed 2.6 times, and the film was cooled with a roll group at 25 ° C. to obtain a uniaxially stretched film. Further, subsequently, the uniaxially stretched film was subjected to corona discharge treatment in air, and the treated surface was coated with the following antistatic layer-forming coating liquid by a bar coating method using a metering bar. While holding both ends of the uniaxially stretched film coated with this antistatic layer-forming coating liquid with clips, the uniaxially stretched film is guided to a preheating zone in a tenter, preheated and dried at 120 ° C, and then continuously in a longitudinal direction in a heating zone of 125 ° C. The film was stretched in the vertical direction (transverse direction) by 3.45 times, subsequently subjected to a heat treatment at 200 ° C. in a heat treatment zone in a tenter, and further subjected to a relaxation treatment in the transverse direction by 5% at the temperature,
A polyester film having a thickness of 50 μm, which is obtained by continuously performing heat treatment at 150 ° C. and 120 ° C., then uniformly cooling and winding the film so that the polyester layer (A) is 3.5 μm on one side and the polyester layer (B) is 43 μm. A white laminated polyester film having an antistatic layer with a thickness of 0.1 μm provided thereon was obtained.

The characteristics of the obtained white laminated polyester film are as shown in Table 1, and the whiteness, antistatic property, and
It can be seen that it is excellent as a receiving sheet base material for heat-sensitive transfer recording because it exhibits printing characteristics, high sensitivity characteristics, and has an excellent workability of crease resistance.

[Antistatic Layer-Forming Coating Liquid] (A) Antistatic Agent: Lithium Polystyrenesulfonate Salt Water Dispersion (Molecular Weight = about 70,000) (B) Binder Resin: Acrylic Emulsion (Acrylic Component: Methyl Methacrylate / Ethyl Acrylate /
Acrylic acid / N-methylol acrylamide = 60/3
8/1/1 (wt%) copolymer, glass transition temperature 60
C.) The above (A) / (B) was mixed at a solid content weight ratio of 30/70 and diluted with water to a solid content concentration of 4% by weight.

(Example 6) A white laminated polyester film was obtained in the same manner as in Example 5 except that the polyester layer (A) had a thickness of 3.5 µm on one side and the polyester layer (B) had a thickness of 40 µm. .

The characteristics of the obtained white laminated polyester film are as shown in Table 1. Whiteness, antistatic property,
It can be seen that it is excellent as a receiving sheet base material for heat-sensitive transfer recording because it exhibits printing characteristics, high sensitivity characteristics, and has an excellent workability of crease resistance.

Example 7 The same as Example 1 except that 0.3% by weight of hindered phenol IRGANOX 1010 was added as an antioxidant to the raw material supplied to the extruder (B) of Example 1. A white laminated polyester film was obtained.

The characteristics of the obtained white laminated polyester film are shown in Table 1, and the whiteness, antistatic property, and
It can be seen that the printing property and the high sensitivity property are exhibited, and the workability of the crease resistance is excellent, and that it is good as a receiving sheet base material for thermal transfer recording. Further, this film was capable of extremely stable film formation without sudden breakage as compared with continuous film formation.

(Example 8) Extruder (A) and extruder (B)
In a composite film forming apparatus having a polyester layer (A)
To form a PET chip with an average particle size of 0.2μ
7% by weight of anatase-type titanium oxide fine particles of m and 0.15% by weight of a fluorescent whitening agent "OB-1" (manufactured by Eastman) were added, and PEG having a molecular weight of 4,000 was added by 5% by weight. The copolymer PET contained was added so that PEG was added in an amount of 0.3% by weight based on the entire resin constituting the polyester (A) layer, and the mixture was vacuum-dried at 180 ° C. for 3 hours and then placed on the extruder (A) side. It was supplied, melted at 280 ° C. by a conventional method, and introduced into a T-die composite die.

On the other hand, as a raw material to be supplied to the extruder (B), PET chips were mixed with PMP in an amount of 10% by weight, and anatase type titanium oxide fine particles having an average particle diameter of 0.2 μm were added in an amount of 0.15.
PEG is polyester (B), which is a copolymerized PET containing 5% by weight of polyethylene glycol having a molecular weight of 4,000 (hereinafter abbreviated as PEG) as a dispersant.
It is assumed that the resin is added in an amount of 1% by weight with respect to the total resin constituting the layer, which is vacuum-dried at 180 ° C. for 3 hours, and then supplied to the extruder (B) side and then 280 It was melted at ℃ and similarly introduced into the T-die composite die.
Next, after allowing the polyester layer (A) to be laminated on both surface layers of the polyester layer (B) in the die,
The sheet was coextruded into a melt-laminated sheet. And
The molten laminated sheet was contact-cooled and solidified by an electrostatic charge method on a cooling drum whose surface temperature was kept at 25 ° C. to obtain an unstretched laminated film. Subsequently, the unstretched laminated film was preheated by a group of rolls heated to 85 ° C. according to a conventional method, and then stretched 1.1 times in the longitudinal direction (longitudinal direction) using a heating roll at 95 ° C., and then 3. Twofold main stretching was carried out, followed by cooling with a roll group at 25 ° C. to obtain a uniaxially stretched film. Further, subsequently, the uniaxially stretched film was subjected to a corona discharge treatment in air, and the treated surface was coated with an antistatic layer-forming coating solution similar to that used in Example 3 by a bar coating method using a metering bar. did. While holding both ends of the uniaxially stretched film coated with this antistatic layer-forming coating liquid with clips, it is introduced into a preheating zone in a tenter and preheated and dried at 110 ° C, and then continuously in a longitudinal direction in a heating zone of 125 ° C. It was stretched 3.5 times in the vertical direction (transverse direction). Further subsequently, a heat treatment at 210 ° C. was performed in a heat treatment zone in the tenter, and further, a relaxation treatment was performed in the transverse direction at 5% at that temperature, a heat treatment was performed at 150 ° C., and then the film was uniformly cooled and then wound up. A white laminated polyester film having a 0.1 μm-thick antistatic layer provided on a 50 μm-thick polyester film having a polyester layer (A) of 3.5 μm on one side and a polyester layer (B) of 43 μm on one side was obtained.

The properties of the white laminated polyester film thus obtained are as shown in Table 1, which shows whiteness, antistatic properties, printing properties, high sensitivity properties, and is extremely processable with crease resistance. It can be seen that it is an excellent level and is excellent as a receiving sheet base material for thermal transfer recording.

Example 9 As a raw material supplied to the extruder (B) of Example 1, 5% by weight of PMP was added to PET chips.
0.25% by weight of anatase type titanium oxide fine particles having an average particle diameter of 0.2 μm, and a molecular weight of 4,000 as a dispersant.
0% polyethylene glycol (hereinafter abbreviated as PEG) containing 5% by weight of copolymerized PET is 1.0% by weight with respect to the entire resin constituting the polyester (B) layer.
A white laminated polyester film was obtained in the same manner as in Example 1 except that the antistatic layer forming coating liquid was changed to the following.

The characteristics of the obtained white laminated polyester film are as shown in Table 1. The whiteness, antistatic property, and
It can be seen that the printing characteristics and high sensitivity characteristics are exhibited, and the workability of crease resistance is at a practical level, and it is excellent as a receiving sheet base material for thermal transfer recording.

(Comparative Example 1) As a raw material supplied to the extruder (B), 5 wt% of PMP was added to PET chips, and 4 wt% of polyethylene glycol having a molecular weight of 4,000 (hereinafter abbreviated as PEG) was used as a dispersant. % Of the copolymerized PET contained in the polyester (B) layer is 0.4% by weight based on the total weight of the resin constituting the polyester (B) layer. On a polyester film having a thickness of 85 μm, in which the polyester layer (A) was 5.5 μm on one side and the polyester layer (B) was 74 μm in the same manner as in Example 1 except that the roll temperature was increased by 3.7 ° C. A white laminated polyester film provided with an antistatic layer having a thickness of 0.1 μm was obtained.

The white laminated polyester film contained fine air bubbles inside, but its properties were inferior overall as shown in Table 1.

[Antistatic Layer-Forming Coating Liquid] (A) Antistatic Agent: Polystyrenesulfonate Ammonium Salt Aqueous Dispersion (Molecular Weight = about 10,000) (B) Binder Resin: Acrylic Emulsion (Acrylic Component: Methyl Methacrylate / Ethyl Acrylate /
Acrylic acid / N-methylol acrylamide = 60/3
8/1/1 (wt%) copolymer, glass transition temperature 60
C.) The above (A) / (B) was mixed at a solid content weight ratio of 30/70 and diluted with water to a solid content concentration of 4% by weight.

Comparative Example 2 As a raw material to be fed to the extruder (B), PET chips were made to contain 2.5% by weight of PMP and polyethylene glycol having a molecular weight of 4,000 (hereinafter abbreviated as PEG) was used as a dispersant. Copolymer PET containing 5% by weight was added so that PEG was 0.3% by weight based on the entire resin constituting the polyester (B) layer, except that no antistatic layer was formed. In the same manner as in Example 1, the polyester layer (A) is 5 μm on one side,
A polyester layer (B) having a thickness of 60 μm and a thickness of 70
A μm polyester film was obtained.

The characteristics of this white laminated polyester film were inferior as shown in Table 1.

[0121]

[Table 1]

[0122]

The white laminated polyester film for heat-sensitive transfer recording of the present invention has a specific gravity of 0 in which the polyester layer (A) containing inorganic particles is provided on at least one side of the polyester layer (B) containing fine bubbles. The laminated polyester film of 6 to 1.1 has a coating layer provided on at least one surface, the surface resistivity measured from the coating surface side is 10 ¹¹ Ω / □ or less, and the PH is 4 to 10 Is. The white laminated polyester film for heat-sensitive transfer recording of the present invention is excellent in whiteness, antistatic property and printing property, and also exhibits high sensitivity property and is excellent in processability such as crease resistance. Therefore, the white laminated polyester film can be used very suitably as a receiving sheet for thermal transfer recording using the substrate as a base material.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B41M 5/38 B41M 5/26 101H F term (reference) 2H111 AA26 AA27 CA03 CA13 CA25 CA33 4F100 AA01B AA01D AA20B AA20D AK41A AK41B AK41D AK42 AL01B AL01D BA03 BA05 BA06 BA07 BA10A BA10C BA10E CA06 DE01B DE01D DJ01A EH20 EH202 EJ38 EJ382 EJ42 EJ422 GB90 JL01 JM02C JM02E YY00B YY00D

Claims (8)

[Claims] 1. A laminated polyester film having a specific gravity of 0.6 to 1.1, wherein a polyester layer (B) containing fine bubbles is provided with a polyester layer (A) containing inorganic particles on at least one side thereof. A white laminate for thermal transfer recording, characterized in that a coating layer is provided on at least one surface, the surface resistivity measured from the coating surface side is 10 ¹¹ Ω / □ or less, and the PH is 4 to 10. Polyester film. 2. The white laminated polyester film for heat-sensitive transfer recording according to claim 1, wherein the resin constituting the coating layer contains 10 to 40% by weight of a metal salt of styrene sulfonic acid. 3. An inorganic particle contained in the polyester layer (A) is titanium oxide, and titanium oxide is further contained in the polyester layer (B), which satisfies the formula (1). A white laminated polyester film for heat-sensitive transfer recording according to Crab. 5 ≦ Ta / Tb ≦ 90 (1) Ta: Titanium oxide concentration (% by weight) in polyester layer (A) Tb: Titanium oxide concentration (% by weight) in polyester layer (B) 4. The feeling according to claim 1, wherein the polyester layer (A) contains a polyester obtained by copolymerizing polyalkylene glycol in an amount of 0.1 to 1.5% by weight in terms of polyalkylene glycol. White laminated polyester film for thermal transfer recording. 5. The white laminated polyester film for thermal transfer recording according to claim 1, wherein the elongation Sm in the longitudinal direction of the film and the elongation St in the width direction thereof satisfy the formulas (2) and (3). 5 <Sm-St <80 (2) 90 <Sm <200 (3) 6. The white laminated polyester film for thermal transfer recording according to claim 1, which has a film thickness of 20 to 50 μm. 7. The white laminated polyester film for thermal transfer recording according to claim 1, wherein the polyester layer (B) contains an antioxidant in an amount of 0.05 to 1.0% by weight. 8. The white laminated polyester film for thermal transfer recording according to claim 1, wherein the polyester layer (A) is provided on both surfaces of the polyester layer (B).