JP2000272249A - Sublimation type thermal transfer ink easy adhesion polyester film - Google Patents

Abstract

An object of the present invention is to provide a sublimation-type heat-sensitive transfer easy-to-ink polyester film having good adhesion to an ink layer and capable of obtaining excellent images. . SOLUTION: The present invention applies a water-dispersible or aqueous coating solution containing an acrylic resin containing a hydroxyl group to at least one surface of a polyester film before completion of crystal orientation, and then performs drying, stretching, and further heat treatment. Sublimation type thermal transfer ink easily adhesive polyester film having a coated layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a base film suitable for a sublimation type thermal transfer recording medium. More specifically, by having a specific coating layer, the adhesiveness to the sublimation type ink layer is excellent, and further, the adhesiveness and the dimensions of the film do not change even when heated during printing, and no wrinkles are generated. The present invention relates to a sublimation-type thermal transfer recording medium which does not transfer an ink layer to a coating layer, has little dyeability to a coating layer by a sublimation dye, and can form a transfer image excellent in gradation.

[0002]

2. Description of the Related Art Polyester film has its mechanical properties,
It has excellent properties such as dimensional stability and heat resistance, and has been used in many fields to date. One of the uses is as a base film of a thermal transfer recording material.

[0003] Among thermal transfer recording materials, the sublimation transfer recording system has greatly expanded as a recording system capable of easily outputting a high-quality full-color image. In the sublimation type thermal transfer, a heat sublimable dye is contained in a binder, and only the dye sublimates due to heat and is absorbed by an image receiving layer of a transfer receiving paper to form a gradation image. In order to sublimate only the dye, high adhesion between the binder and the base film is required, and it is essential that the adhesion does not decrease due to environmental changes or aging. If the adhesion is insufficient, the binder layer migrates to the transfer receiving paper, significantly impairing the gradation, and a phenomenon called overtransfer occurs.

In general, polyester films have a high degree of crystal orientation, and therefore have poor adhesiveness and do not adhere at all even when an ink layer is directly applied. For this reason, physical and chemical treatments are applied to the film surface in order to increase the adhesiveness with the ink layer, but sufficient adhesiveness cannot be obtained. Further, the improvement of the adhesion by the primer treatment performed in the manufacturing process is very advantageous in terms of performance and processing, and is widely performed. A primer treatment using an aqueous coating agent such as polyester, acrylic, or urethane is known. Furthermore, since the base film is pursued to be as thin as possible, high strength is required, and dimensional change due to shrinkage due to heating during printing is also required to be small.

[0005]

However, the prior art has the following problems. General polyester, acrylic, urethane coating film of water-based coating even if the desired adhesion is obtained moisture resistance, water resistance, solvent resistance,
The blocking resistance and the like may be inferior. Furthermore, there is also a problem of the dyeability of the sublimable dye on the easily accessible layer. In recent years, high-speed printing has been promoted, and a higher temperature is instantaneously applied. Therefore, the heat resistance of the easy-contact layer and the adhesion to the ink layer when heated are required. If the adhesion is poor, the original color density and gradation are insufficient.

The present invention solves these problems, and has excellent adhesion to a sublimable ink layer, does not have a dyeability of a sublimable dye on an easily accessible layer, and provides a transferred image excellent in gradation. An object of the present invention is to provide an easily adhesive polyester film for sublimation type thermal transfer ink.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in view of the above problems, and as a result, have found that the above problems can be solved by using a polyester film having specific physical properties as a base material. It was completed.

According to the present invention, a water-dispersible or aqueous coating solution containing an acrylic resin having a hydroxyl group is applied to at least one surface of the polyester film before the crystal orientation is completed,
The invention is based on a sublimation type thermal transfer ink easy-adhesion polyester film having a dried, stretched and further heat-treated coating layer.

Hereinafter, the present invention will be described in detail. The polyester constituting the polyester film used in the present invention is a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof.

Specific examples of the polyester include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylene dimethylene terephthalate), polyethylene 2,6-naphthalenedicarboxylate, and the like. Or a mixture of these with a small proportion of another resin. Among them, polyethylene terephthalate is preferable, and polyethylene-2,6-naphthalenedicarboxylate is more preferable if a thinner film and higher heat resistance are required.

The polyester used in the present invention contains an inorganic or organic lubricant such as silicon dioxide, calcium carbonate, kaolin, or silicone particles having a particle size of 0.1 to 5 μm.
It is better to contain from 03 to 3.0% by weight, preferably from 0.1 to 1.0% by weight. By adding these lubricants, a polyester film having a center line roughness of 0.01 to 1 μm on the surface can be obtained. If the center line roughness of the film surface is less than 0.01 μm, sufficient slip properties cannot be obtained, and the film will be wrinkled and sticking of the thermal head will occur. When the center line roughness of the surface is larger than 1 μm, the thermal conductivity during printing becomes poor, and a sufficient image cannot be obtained.

The polyester may contain a stabilizer, a colorant, an antioxidant, and other additives as needed, so long as the original performance is not impaired.

The polyester film is prepared by melt-extruding the polyester into a film, winding the film around a casting drum, and cooling and solidifying the film to obtain an unstretched film. The unstretched film is heated to Tg to (Tg + 60) ° C. and stretched once or twice or more in the longitudinal direction.
Make it 7 times to 7 times. Then Tg ~ (Tg + 6
0) Stretch at 3 ° C. so that the width direction becomes 3 to 5 times,
Heat treatment at 100 to 250 ° C. for 0.1 to 10 seconds, and 0 to 20 ° C. in the width direction at a temperature 10 to 20 ° C. lower than the heat treatment temperature.
The re-heat treatment is performed while increasing the percentage shrinkage or elongation by 0 to 10%. It is necessary to form a film as described above.

The polyester film has a thickness of 0.5 to 1
It is preferably 0 μm, more preferably 1 to 5 μm.
In recent years, there has been a demand for thinner films due to downsizing of printing equipment and speeding up of printing. For example, the limit of the thin film of the polyethylene terephthalate film is 1.5 μm, and the limit of the thin film is 0.5 μm by using a polyethylene-2,6-naphthalate film having higher strength. When the thickness of the film is more than 10 μm, the thermal conductivity at the time of printing deteriorates, and high-speed printing cannot be performed.

The polyester film preferably has a thickness variation in the longitudinal direction and the width direction of 0 to 10%. 1 uneven thickness
If it exceeds 0%, the back coat and the sublimation ink layer cannot be uniformly applied, and the running property during printing and the resolution of printing deteriorate.

The refractive index of the polyester film is preferably in the range of 1.600 to 1.800 in the longitudinal and width directions. When the refractive index is less than 1.600, the mechanical strength is reduced, and the elongation at the time of printing is increased. When the refractive index is more than 1.800, the film is easily broken because the degree of orientation is increased.

The polyester film requires a coating layer containing an acrylic resin containing an amide group on at least one side. This coating layer is necessary in order to improve the adhesiveness between the ink layer composed of the sublimable dye and the resin binder and the polyester film.

The thickness of the coating layer used in the present invention is 0.0
The range is preferably from 01 to 1 μm, more preferably from 0.0 to 1 μm.
1 to 0.5 μm. 0.001μm thickness of coating layer
If it is thinner, the adhesion between the ink layer and the polyester film will be insufficient. When the thickness of the coating layer is more than 1 μm, blocking occurs when the film after application of the easy-adhesion layer is rolled, or dyeing of the sublimable dye onto the easy-adhesion layer occurs, resulting in a sufficient color density and color depth. Tonality cannot be obtained.

The wetting index of the surface of the coating layer is 35 to 75 dyne
/ cm is preferable, and more preferably 40 to 70 dyne /
cm. If the wettability index of the surface of the coating layer is less than 35 dyne / cm, repelling occurs when a coating solution comprising a sublimable dye and a resin binder is applied, and a uniform layer is not obtained.
When the wetting index of the surface of the coating layer is more than 75 dyne / cm, hydrophilicity increases, and adhesion to the ink layer deteriorates.

The ring and ball softening point of the coating layer is 50 to 250 ° C.
Is more preferable, and more preferably 100 to 250 ° C. If the ring and ball softening point of the coating layer is less than 50 ° C., the ink layer is peeled off by heating during printing, and printing becomes impossible. When the ring and ball softening point of the coating layer is higher than 250 ° C., the coating film does not have firm toughness, the adhesion between the polyester film and the coating layer is insufficient, and the adhesiveness with the ink layer cannot be obtained, and it is difficult to prepare an ink ribbon. Becomes

The hydroxyl groups of the hydroxyl group-containing acrylic resin constituting the coating layer can be introduced by copolymerizing with the following acrylic monomers. 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2
-Hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, N-methylol acrylamide, N-methylol methacrylamide and the like.
It is sufficient that the acrylic resin contains at least one kind of the above-mentioned monomer containing a hydroxyl group. If no hydroxyl group is present in the acrylic resin, adhesion to the ink layer cannot be obtained.
More preferably, 2-hydroxyethyl acrylate, 2
-Hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate.

Examples of the components of the acrylic resin having a hydroxyl group include acrylic monomers as exemplified below. As this acrylic monomer, alkyl acrylate,
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, cyclohexyl group, etc.); acrylamide, methacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N, N-dialkylacrylamide, N, N-dialkylmethacrylate (As the alkyl group, a methyl group, an ethyl group, a n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, a cyclohexyl group, etc.),
N-alkoxyacrylamide, N-alkoxymethacrylamide, N, N-dialkoxyacrylamide, N,
Amide-containing monomers such as N-dialkoxy methacrylamide (alkoxy groups include methoxy, ethoxy, butoxy, isobutoxy, etc.), acryloylmorpholine, N-phenylacrylamide, N-phenylmethacrylamide; glycidyl acrylate, glycidyl methacrylate And epoxy group-containing monomers such as allyl glycidyl ether; acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt) A) a monomer containing a carboxy group or a salt thereof; a monomer of an acid anhydride such as maleic anhydride or itaconic anhydride; vinyl isocyanate, allyl isocyanate, styrene, α-methylstyrene, vinylmethyl Ether, vinyl ethyl ether, vinyl trialkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, alkyl itaconic acid monoester, acrylonitrile, methacrylonitrile, vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate, butadiene, etc. Of the monomer. In addition, these monomers are exemplified, but not limited thereto. These monomers can be copolymerized using one kind or two or more kinds.

The coating layer may be a mixture of an acrylic resin containing a hydroxyl group and other general resins such as polyester and urethane, and modified products thereof such as acrylic-modified polyester and acrylic-modified urethane. More preferably, mixing with polyester is good.

A cross-linking agent such as epoxy, oxazoline or melamine may be added to these coating layers in order to further improve heat resistance. More preferred is epoxy.

The coating solution for forming the coating layer may contain some organic solvent as long as it does not affect the hydroxyl group-containing acrylic resin or other additives. This coating liquid can be used by adding a required amount of a surfactant such as an anionic surfactant, a cationic surfactant, or a nonionic surfactant. As such surfactants, those capable of lowering the surface tension of the aqueous coating solution to 40 dyne / cm or less and promoting wetting to the polyester film are preferable. For example, polyoxyethylene-fatty acid esters, sorbitan fatty acid esters, glycerin fatty acid esters, and fatty acids Metal soaps, alkyl sulfates, alkyl sulfonates, alkyl sulfosuccinates, quaternary ammonium chloride salts,
Examples thereof include alkylamine hydrochloride and betaine-type surfactant. Further, other additives such as an antistatic agent, an ultraviolet absorber, a pigment, an organic filler, an inorganic filler, a lubricant, and an antiblocking agent can be used in combination as long as the effects of the present invention are not lost.

This coating solution is preferably applied to one or both sides of the polyester film before the crystal orientation is completed in the polyester film production process. The coating may be performed separately from the polyester film manufacturing process, but in this case, dust, dust, etc. are easily involved, and the portion becomes a defect at the time of printing, and a clean atmosphere is desirable.Moreover, a suitable film is relatively inexpensive. From these points, coating during the manufacturing process is preferred. At that time, the solid concentration of the coating solution is usually 0.1 to 30% by weight, more preferably 1 to 30% by weight.
10% by weight. The coating amount is preferably 0.5 to 50 g per 1 m ^{2 of the} running film.

Known methods can be applied as the coating method. For example, roll coating, gravure coating, roll brushing, spray coating, air knife,
An impregnation method, a curtain coating method, or the like may be applied alone or in combination.

[0028]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Each characteristic value was measured by the following method.

(1) Thickness The weight of the film is measured and calculated from the density of the polyester.

(2) Refractive index Measured using an Abbe refractometer with sodium D line (589 nm) as a light source. The measurement is performed at 25 ° C. and 65% RH using methylene iodide as the mounting solution.

(3) Thickness of coating layer The thickness is calculated from the coating amount per 1 m ^{2 of the} coating solution and the solid concentration.

(4) Wetting index The easily adhered surface was determined according to JIS K 6768 method.
23 ° C. and 50% R.C. H. Was measured under the following conditions. That is, formamide and ethylene glycol monoethyl ether were each mixed at a predetermined ratio, and 1 dyne / cm
It was prepared every other time, and a very small amount of a dye having a high degree of coloring was added to obtain a standard solution. Absorbing cotton (1
5 to 20 mg) is evenly wound around a length of 15 to 20 mm, soaked sufficiently so that the above standard solution does not drip, apply a cotton swab horizontally to the sample, and move in one direction to apply. The applied liquid film should be as wide as possible, its area should be 6 cm ² , and the application should be completed in 0.5 seconds.

(5) Ring and ball softening point The coating solution is dried to produce a dried product, which is then subjected to JIS K-253.
The softening point is measured according to 1-1960. Glycerin is used for the heating bath, and the temperature is raised at a rate of about 5 ° C./min.

(6) Adhesiveness A “backside layer” is formed on the opposite surface of the easy-adhesion layer of the film,
Thereafter, an "ink layer" was formed on the surface of the easily adhesive layer to prepare a sublimation-type thermal transfer material. Using the sublimation-type thermal transfer material, a 15 cm wide and 25 cm long solid print is made on the center of an A4 size image receiving paper using a sublimation type thermal transfer recording digital color printer (“UP-D70A” manufactured by Sony Corporation). went. The state of overtransfer of the ink layer was visually observed and evaluated as follows. ；: No over-transfer of the ink layer at all △; over-transfer of the ink layer is less than 1% ×; over-transfer of the ink layer is less than 1 to 10% XX; over-transfer of the ink layer is 10% or more

"Back layer"-Back layer coating solution Esrec KS-5 (polyvinyl acetoacetal, trade name, manufactured by Sekisui Chemical Co., Ltd.) 4.4 parts by weight, Vernock D-750-45 (polyisocyanate Dainippon Ink and Chemicals, Inc.) 22 parts by weight, Phosphanol RD720 (phosphate ester surfactant)
0.3 parts by weight, solvent (methyl ethyl ketone / toluene =
1/1) 73 parts by weight in coating condition dry coating so as to be 1g / m ^2, 80 ℃, dried at 1 minute.

"Ink layer"-Ink layer coating solution DH / C2 (sublimable dye Nippon Kayaku Co., Ltd. product name)
4 parts by weight, Esrec KS-5 (polyvinyl acetoacetal, trade name, manufactured by Sekisui Chemical Co., Ltd.) 4 parts by weight, 92 parts by weight of a solvent (methyl ethyl ketone / toluene = 1/1) ・ Coating conditions 1 g / m ² in a dry state It is applied so as to be dried at 80 ° C. for 1 minute.

(7) Glass transition point Tg Measured using a DSC (differential scanning calorimeter) manufactured by PerkinElmer. The measuring method is as follows. Sample 10m
g was set in a DSC apparatus, melted at a temperature of 300 ° C. for 5 minutes, and then quenched in liquid nitrogen. This quenched sample is
The temperature is raised at a rate of ° C / min, and the glass transition point Tg is detected.

Examples 1-4, Comparative Example 1 o- at 25 ° C.
Polyethylene-2,6-naphthalate (containing a lubricant) having an intrinsic viscosity of 0.61 measured in chlorophenol was extruded from a T-die and quenched while electrostatically applied on a rotary cooling drum maintained at about 40 ° C. Thus, an unstretched film was obtained. Next, the unstretched film was stretched 3.6 times in the longitudinal direction at 125 ° C. to obtain a uniaxially stretched film. One side of the uniaxially stretched film was coated with a coating solution having a solid content of 4% by weight (Table 1) by a kiss coat method at 2.7 g / m ² . Next, the film was stretched 3.8 times in the width direction at 140 ° C., subjected to a tension heat treatment at 240 ° C. with a fixed length, and reheated at 240 ° C. while shrinking by 2% in the width direction. A biaxially oriented polyester film having a thickness of 2.5 μm was obtained. Table 2 shows the physical properties of the film.

Comparative Example 2 A biaxially oriented polyester film was obtained in the same manner as in Example except that the coating of the adhesive layer was not performed. Table 2 shows the physical properties of the film.

[0040]

[Table 1]

Acrylic A: composed of 75 mol% of methyl methacrylate / 15 mol% of ethyl acrylate / 10 mol% of 2-hydroxyethyl methacrylate. Acrylic B: 80 mol% of methyl methacrylate / 20 mol% of ethyl acrylate. Polyester: 35 mol% of terephthalic acid / 12 mol% of isophthalic acid / 5 mol% of 5-sodium sulfoisophthalic acid / 45 mol% of ethylene glycol / 5 mol% of diethylene glycol Crosslinking agent: N, N, N ', N'-tetraglycidyl-m-
Xylylenediamine Wetting agent: polyoxyethylene (n = 7) lauryl ether

[0042]

[Table 2]

[0043]

As described above, the polyester film of the present invention which has excellent adhesion between the ink layer for sublimation type thermal transfer printing and the film can provide excellent images.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) C08J 7/04 CFD C08J 7/04 CFDJ // B29K 35:00 67:00 B29L 7:00 C08L 67:00 (72) Inventor Satoshi Kitazawa 3-37-19 Koyama, Sagamihara-shi, Kanagawa F-term in Sagamihara Research Center, Teijin Limited (Reference) 2H111 AA27 AA48 BA03 BA07 BA53 BA61 BA71 BB02 BB06 DA01 DA04 4F006 AA35 AB24 BA01 CA01 EA05 EA06 4F100 AK25B AK25C AK41A AK42B AK42C BA02 BA03 BA06 BA25B BA25C CC10B CC10C EH462 EJ372 EJ412 EJ862 JA04B JA04C JB05B JB05C JB09B JB09C JB11B JB11C JD14B JD14C JL11 JM01B JM01C YY00B YY00C 4F210 AA21 AA24 AA26 AC05 AD05 AD08 AG01 AG03 AH81 QA03 QC06 QD04 QD08 QD13 QG01 QG18 QW11 QW12

Claims (6)

[Claims] 1. A water-dispersible or aqueous coating solution containing an acrylic resin containing a hydroxyl group is applied to at least one surface of the polyester film before the crystal orientation is completed, and dried,
A sublimation type heat-sensitive transfer easy-to-ink polyester film having a coating layer that has been subjected to stretching and further heat treatment. 2. The polyester film according to claim 1, wherein the thickness of the coating layer is in the range of 0.001 to 1 μm. 3. The coating layer surface has a wetting index of 35 to 75 dy.
The polyester film according to claim 1, which is in a range of ne / cm 2. 4. The ring and ball softening point of the resin of the coating layer is 50 ° C.
The polyester film according to claim 1, wherein the temperature is in the range of ~ 250C. 5. The polyester film according to claim 1, wherein said polyester film is mainly composed of polyethylene terephthalate. 6. The polyester film according to claim 1, wherein said polyester film is mainly composed of polyethylene-2,6-naphthalenedicarboxylate.