JPH0371039B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a film for thermal transfer recording, and more specifically, a thermal transfer recording film that can be printed by melting colorant ink by heating with a thermal head and transferring it to recording paper. This paper relates to commercial films, and in particular to improved technology that enables high-speed printing. [Prior Art] Various recording methods are already known, but thermal transfer using a thermal recording device such as a thermal printer has the advantage of excellent operability and maintainability. In this method, the recording paper and the heat-sensitive ink layer (heat-sensitive transfer colored layer) of the film ribbon for heat-sensitive transfer recording are brought into contact with each other, and the film is selectively heated by a pulse signal from a heating head on the opposite side of the ink layer. When this happens, the ink (colorant) is heated through the film, melts it, and transfers it to the recording paper. Until now, paper such as condenser paper has been used as this thermal transfer recording film. However, when trying to shorten the input time to the heating head in order to speed up recording, it becomes necessary to speed up heat transfer, which requires either making the thermal transfer recording film thinner or increasing the input power. In either case, the following problems arise. For example, thin paper such as capacitor paper has low mechanical strength and is particularly susceptible to tearing, so it cannot be made thinner. A possible solution to this problem would be to use a strong plastic film as the base material, but the following problems also arise in this case. In other words, during printing, high heat of around 250 to 300°C or more is applied to the thermal transfer recording film from the heating head, causing a phenomenon in which the base plastic partially fuses to the head, and the feeding of the thermal transfer recording film becomes difficult. be hindered. This phenomenon is called stagnation, and not only causes the recording to lose its sharpness, but also causes operational problems such as poor running of the thermal transfer film. As a measure to enable the use of plastic film as a base material for dry heat transfer recording films, it has been proposed to provide a heat-resistant protective layer such as a thermosetting resin. However, even if these methods are used, if the heat-resistant protective layer is made thick enough to be effective in preventing the sticking phenomenon in order to speed up recording, the resolution of printing deteriorates, so it is not a sufficient solution. In addition, when trying to improve heat transfer by making the base material thinner to speed up recording, the stiffness of the thermal transfer film becomes weaker (lower).
This can cause wrinkles and bends in the thermal film, leading to poor tape feeding and operational problems. As described above, when trying to increase the output speed of a computer, it has been pointed out that the lack of suitable thermal transfer recording materials is an unresolved problem. [Object of the Invention] The object of the present invention is to improve the sticking phenomenon during thermal transfer, and to improve the speed of recording, printing, and printing.
The present invention aims to provide a thermal transfer recording film that can meet issues such as image clarity. [Structure of the Invention] The present invention relates to a heat-sensitive transfer recording film having a heat-sensitive transferable colored layer that melts by heating on one surface of a base film, wherein the base film has a Young's modulus in the longitudinal direction and a Young's modulus in the axial direction. The sum of 1200Kg/
mm ² or more, a thickness of 0.5 μm to 8 μm, and a density of 1.345 g/cm ³ to 1.365/cm ³ . This is a film for thermal transfer recording. In this embodiment, a heat-resistant protective film is formed on the other surface of the base film. The present invention will be explained in detail below. The base film in the present invention must have a sum of Young's modulus in the longitudinal direction and Young's modulus in the axial direction of 1200 Kg/mm ² or more. The reason why a high Young's modulus is required is that as the base film becomes thinner to increase the speed of thermal transfer, its stiffness decreases. This is to avoid operational troubles such as bending or wrinkles during operation. The sum of Young's moduli in the length direction and width direction of the base film must be 1200 Kg/mm ² or more, but preferably
It is 1250 Kg/mm ² or more, more preferably 1300 Kg/mm ² or more. The sum of Young's modulus in the length direction and width direction is 2200Kg/
If it exceeds mm ² , it is not preferable because the stretchability during film formation becomes poor and the film becomes easy to tear. Preferably, the sum of Young's moduli in the length direction and the width direction is 2000 Kg/mm ² or less, more preferably 1800 Kg/mm ² or less, particularly preferably 1600 Kg/mm 2 or less.
^mm2 or less. Note that the Young's modulus in the width direction is required to be at least 450 Kg/mm ² , preferably 500 Kg/mm ² or more. An oriented film that is too uniaxially biased is not preferred. The thickness of the base film in the present invention is 0.5 μm to 0.8 μm. When the thickness of the base film is thinner than 0.5μm, the Young's modulus in the length direction and width direction is
Even if it is 1200 Kg/mm ² or more, this strength (stiffness) is reduced, which is not preferable because it causes operational troubles such as bending and wrinkles when running as a thermal transfer recording film.
The thickness of the base film is preferably 0.8 μm or more, more preferably 1.0 μm or more. When the thickness of the base film exceeds 8 μm, heat transfer is inhibited,
For this reason, a long heating time is required, which reduces the speed of thermal transfer recording, which is not preferable. Furthermore, in order to speed up the heat transfer, it is necessary to make the input power to the heating head very large, which is undesirable because it tends to cause the so-called stuck phenomenon. In addition, as the base film becomes thicker, it becomes difficult for the heated area by the heating pad to match the area of the colored layer that is heated and melted by heat transfer, resulting in so-called smearing, which causes the recording to lose its sharpness and reduce resolution. Undesirable. For these reasons, the thickness of the base film only needs to be 8 μm or less, and preferably
The thickness is 6 μm or less, more preferably 4 μm or less, particularly preferably 3 μm or less. The density of the biaxially oriented polyethylene-2,6-naphthalene carboxylate film used as the base film in the present invention is 1.345 g/cm ³ to
It is 1.365g/ ^cm3 . If the density is lower than 1.345 g/cm ³ , the heat shrinkage rate of the base film is too high, and the film shrinks when it comes into contact with a heating head, resulting in an undesirable phenomenon similar to sticking. From this point, the density is 1.348g/cm ³
It is preferably at least 1.351 g/cm ³ , particularly preferably at least 1.351 g/cm 3 . When the density of the base film exceeds 1.365 g/cm ³ , the peel strength between the heat-sensitive transferable colored layer (ink layer) and the base film during heat-sensitive transfer becomes too large.
Peeling spots occur during thermal transfer, reducing image quality. From this point of view, the density is preferably 1.362 g/cm ³ or less,
Particularly preferred is 1.359 g/cm ³ or less. The dicarboxylic acid component of the polyethylene-2,6-naphthalene dicarboxylate used in the present invention is mainly naphthalene-2,6-dicarboxylic acid. Of the dicarboxylic acid components, naphthalene-2,6-dicarboxylic acid preferably accounts for 85 mol% or more. Further, the diol component of this polymer is mainly composed of ethylene glycol. Among the diol components, one in which ethylene glycol accounts for 85% is preferred. Any method can be used to produce this polymer. For example, a dicarboxylic acid and a diol may be directly polymerized, a diester of a dicarboxylic acid and a diol may be transesterified and then polymerized, or a di(hydroxyalkyl) ester of a dicarboxylic acid may be subjected to a deglycol reaction. Polymerization may be carried out by
Before the completion of the polymerization of this polyethylene-2,6-naphthalene dicarboxylate, one or more suitable third components may be added to form a copolymerized or mixed polyester. is a mixture having a divalent ester-forming functional group, such as oxalic acid, succinic acid, adipic acid,
Aliphatic dicarboxylic acids such as sebacic acid and dimer acid, aliphatic dicarboxylic acids such as cyclopropanedicarboxylic acid, cyclobutanedicarboxylic acid, hexahydroterephthalic acid, phthalic acid, isophthalic acid,
Aromatic dicarboxylic acids such as naphthalene-2,7-dicarboxylic acid and diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, sodium 3,5-dicarboxybenzenesulfonate, etc. carboxylic acid, glycolic acid, P-
Oxycarboxylic acids such as oxybenzoic acid and P-oxyethoxybenzoic acid, trimethylene glycol, diethylene glycol, tetramethylene glycol, hexamethylene glycol, 2,2-dimethylpropane-1,3-diol, P-xylylene glycol, 1 , 4-cyclohexanedimethanol, bisphenol A, bisphenolic sulfone, 1,4-bis(β-hydroxyethyne)benzene, 2,2-bis(P-β-hydroxyethoxyphenyl)propane, polyalkylene glycol , oxy compounds such as P-phenylenebis(dimethylsiloxane), or functional derivatives thereof, high polymerization degree compounds derived from the above carboxylic acids, oxycarboxylic acids, oxy compounds, or functional derivatives thereof, etc. Compounds having 2 ester-forming functional groups, such as benzoic acid, benzoylbenzoic acid, benzyloxybenzoic acid, methoxypolyalkylene glycol, and the like. Compounds having three or more ester-forming functional groups, such as glycerin, pentaerythritol, trimethylolpropane, etc., can also be used as long as the polymer is substantially linear. The polyester may also contain a matting agent such as titanium dioxide, a stabilizer such as phosphoric acid, phosphorous acid and their esters, and inert solid fine particles such as fine silica and china clay. In the present invention, the inert solid particles are preferably silicon dioxide (including hydrates, diatomaceous earth, silica sand, quartz, etc.); alumina;
Silicates containing 30% by weight or more of SiO ₂ (e.g. amorphous or crystalline clay minerals, aluminosilicate (including calcined products and hydrates), hot asbestos, zircon, fly ash, etc.); Mg, Zn, Zr and Ti
oxides; sulfates of Ca and Ba; Li, Na and
Ca phosphate (including monohydrogen and dihydrogen salts);
Benzoates of Li, Na and K; Ca, Ba, Zn,
and Mn terephthalate; Mg, Ca, Ba,
Titanates of Zn, Cd, Pb, Sr, Mn, Fe, Co and Ni; Chromates of Ba and Pb; Carbon (e.g. carbon black, graphite, etc.); Glass (e.g. glass powder, glass beads, etc.); Carbonates of Ca and Mg; fluorite; and ZnS are exemplified. More preferably, anhydrous silicic acid, hydrated silicic acid, aluminum oxide, aluminum silicate (including fired products and hydrates), monolithium phosphate, trilithium phosphate
Lithium, sodium phosphate, calcium phosphate, barium sulfate, titanium oxide, lithium benzoate, double salts of these compounds (including hydrates), glass powder,
Viscosity (including kaolin, bentonite, white clay, etc.),
Examples include talc, diatomaceous earth, and calcium carbonate. Particularly preferred are silicon dioxide, titanium oxide, and calcium carbonate. By selectively including these inert solid fine particles, it is possible to obtain a biaxially oriented film that is even smoother and has better running properties. The method for producing the biaxially oriented film in the present invention includes a method in which the film is stretched simultaneously in the longitudinal and lateral directions using common rolls or stenters, a method in which it is simultaneously stretched in the longitudinal and lateral directions, and a method in which it is simultaneously stretched in the longitudinal and lateral directions, and at least two or more stages in the longitudinal direction in addition to the transverse direction. A stretching method can be adopted. The manufacturing method is illustrated below, but is not limited thereto. After melt extrusion and quenching at 280 to 320°C, a substantially non-oriented unstretched sheet is stretched at a temperature of 110 to 180°C.
Preferably at 115 to 150°C and a stretching ratio of 3 to 7.5 times,
It is stretched in both the longitudinal and transverse directions (the longitudinal magnification may be smaller, larger, or equal to the transverse magnification, or it may be stretched in two or more stages) and heat-set at 170 to 260°C. As the heat-sensitive transferable colored layer in the present invention, a conventionally known heat-sensitive transferable colored layer can be used as it is, and there is no particular limitation. Such a heat-sensitive transferable colored layer is a composition comprising a colorant and a binder. Dyes and colorants are used as coloring agents.
Pigments are used. Examples include inorganic pigments such as carbon black, organic pigments, azo dyes, and anthraquinone dyes. Examples of the binder include waxes such as carnauba wax, wood wax, beeswax, and ester wax, and compositions in which a recording promoter such as dinitrotoluene is added to a polymer typified by ethyl cellulose. Various compositions that soften upon heating and are transferable can be used. In addition, it may contain softeners such as plasticizers and oils, and other additives for improving weather resistance. The thickness of these heat-sensitive transferable colored layers is 0.5 μm to 20 μm, preferably 0.8 μm.
The thickness is 10 μm to 10 μm, more preferably 1 μm to 5 μm. These colored layers are formed by hot-melt coating on a base film, or by dispersing or dissolving the composition in a solvent and applying this coating solution. In the present invention, the effects of the present invention can be sufficiently exhibited even when no heat-resistant protective film is provided on other surfaces of the base film. However, a body heat protective film may also be provided on one side of the base film. Examples of the heat-resistant protective film include silicone resin, epoxy resin, melamine resin, phenolic resin, fluororesin, polyimide resin, nitrocellulose, acrylic resin, polyester resin, cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate. , vinylidene fluoride resin, chlorinated rubber, cyclized rubber, polyvinyl alcohol, boron titanide, silica, talc,
Guanamine resin, paraffin wax, amides or salts of higher fatty acids, etc. may be used, and combinations thereof may also be used. There is also a method of providing a metal layer by vapor deposition of aluminum, but the method is not particularly limited. The thickness of such a heat-resistant protective film is preferably in the range of 0.005 to 10 μm, more preferably in the range of 0.01 to 5 μm, and particularly preferably in the range of 0.05 to 3 μm. If the thickness becomes thin, the stick prevention effect will be insufficient, and if it becomes thick, it will be difficult to increase the printing speed. By providing a heat-resistant protective film as described above,
It becomes possible to further increase the printing speed. [Effects of the Invention] The film for thermal transfer recording of the present invention is suitable for use in thermal printers, and even when the speed of a thermal printer is increased, the printing property is good and the colored layer for thermal transfer recording does not peel or fall off. It is also suitable for high-speed printers because it has the characteristic that it does not occur easily. Furthermore, the thermal transfer recording film of the present invention is less prone to stickiness and has good slipperiness during running, so it is suitable for use in multiple transfer type thermal printers, and is also suitable for use in thermal transfer type color printers. is also suitable. [Examples] The present invention will be further explained based on Examples below. Note that various physical property values and characteristics in the present invention were measured and defined as follows. (1) Young's Modulus Measurement The film was cut into samples with a width of 10 mm and a length of 15 cm, and was stretched using an Instron type universal tensile tester at a chuck distance of 100 mm at a tensile speed of 10 mm/min and a chatch speed of 500 mm/min. Obtained load -
Young's modulus was calculated from the tangent to the rising part of the elongation curve. (2) Film density In a mixed solvent of n-heptane and carbon tetrachloride,
This is a value measured using the float-sink method at 25°C. Furthermore, the properties as a thermal transfer recording film were evaluated as follows. The test pieces were prepared by tape-slitting each film to 8 mm width to form a thermal transfer ribbon, which was then applied to a thermal printer for practical evaluation. The occurrence of stuck phenomenon, thermal printer slippage, adhesion, and image quality were measured. (3) Stick phenomenon The presence or absence of fusion between the thermal transfer ribbon and the heating head was examined. ×…There is a tendency to fuse and there is a problem with ribbon conveyance.△…There is a tendency to fuse, but there is no problem with ribbon conveyance and it is practical.○…There is a slight tendency to fuse, but it is good.◎…No problem at all. Very good (4) Sliding properties in the printer We checked the feeding conditions of the ribbon on the ribbon feeding roller of a thermal printer to see if it slipped or wrinkled. ×... Ribbon may slip, resulting in poor conveyance. △... Ribbon may wrinkle and slip slightly, but it does not cause poor conveyance and is usable. ○... Ribbon may wrinkle slightly, but does not slip. , Good condition with no transport defects ◎...The feeding condition is good and there are no problems at all (5) Adhesion Coating film when the ribbon is rubbed by hand (Cracks and peeling of the heat-sensitive transfer colored layer were observed. ×...The coating film is Cracks and peels off △...The paint film cracks, but the peeling is on the surface, so not all of it comes off. ○...The paint film cracks on its own, but it doesn't peel off. ◎...There is no cracking or peeling of the paint film (6) Image quality For thermal printers We looked at the shading and bleeding of the printed image. ×...The image has uneven shading and the bleeding is strong enough to be unusable. △...There is a slight difference in shading and there is some bleeding, but it is usable for practical use. ○...There is slight bleeding. ◎...Very good with no shading or bleeding Example 1 After drying polyethylene-2,6-naphthalene carboxylate pellets with an intrinsic viscosity of 0.65 obtained by a conventional method, the extruder was used. The unstretched film was then melted at 290 to 310°C and extruded onto a rotating drum to obtain an unstretched film.The unstretched film was stretched 3.8 times in the longitudinal direction at 120°C by a roll stretching method, and further stretched to 140°C. After stretching 3.8 times in the width direction at ℃ by the stenter method, heat treatment was performed at 220℃ for 5 seconds to obtain a biaxially oriented film with a thickness of 2.5 μm.This biaxially oriented film was used as a base film. On the top, 30 parts of carnauba wax, 35 parts of paraffin wax
Department, Oil Black HBB (Orient Chemical Industry Co., Ltd.)
oil-soluble dye) 5 parts, carbon black 25 parts,
5 parts of lanolin was mixed and hot melted to form a hot melt coating to a thickness of 4 μm to obtain a thermal transfer recording film. This thermal transfer recording film was slit into a width of 8 mm and was evaluated using a thermal printer as a thermal transfer ribbon. The results are shown in Table 1. There was no sticking phenomenon, the image quality was clear and good, the slipperiness when running on the thermal printer was good, and the adhesion was also good. Examples 2 to 4 and Comparative Example 1 In Example 1, the stretching ratios in the length direction and width direction were adjusted to obtain biaxially oriented films with different Young's moduli. Using this as a base film, a thermal transfer recording film was obtained in the same manner as in Example 1, and the evaluation results are shown in Table 1. When the Young's modulus was lowered, the sticking phenomenon was more likely to occur, and the slipperiness in the printer also deteriorated. In Example 4, the base film had poor stretchability and was frequently broken during film formation, resulting in low productivity. Examples 5 and 6 and Comparative Example 2 In Example 1, the thickness of the unstretched film and the stretching ratio were adjusted to obtain biaxially oriented films with different thicknesses. Using this as a base film, a thermal transfer recording film was obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 1. When the base film became thinner, even when the Young's modulus was high, wrinkles tended to occur when running on a thermal printer, and the slipperiness tended to deteriorate. Furthermore, as the thickness of the base film increased, the image began to bleed, and there were more uneven shadings, resulting in a decrease in image quality.

[Table] Examples 7 to 9 and Comparative Example 3 In Example 1, the heat treatment temperature and stretching ratio were adjusted to obtain biaxially oriented films with different densities. Using this as a base film, a thermal transfer recording film was obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 2. The lower the density of the base film, the more likely it is to be fused to the heating head. As the density of the base film increased, cracking and peeling of the heat-sensitive transfer colored layer became more likely to occur.

【table】

Claims (1)

[Scope of Claims] 1. In a heat-sensitive transfer recording film having a heat-sensitive transferable colored layer that melts by heating on the surface of the base film, the Young's modulus in the longitudinal direction and the Young's modulus in the width direction of the base film is The sum is 1200Kg/mm2 or ^more , the thickness is 0.5μm to 8μm, and the density is
A film for thermal transfer recording characterized by using a biaxially oriented polyethylene-2,6-naphthalene dicarboxylate film having a weight of 1.345 g/cm ³ to 1.365 g/cm ³ . 2. The dry heat transfer recording film according to claim 1, wherein a heat-resistant protective film is provided on the surface of the base film on which no colored layer is provided.