JPH0441297A - Ribbon for heat transfer - Google Patents

Abstract

PURPOSE:To obtain a ribbon for heat transfer with excellent printing performance by specifying a rate of change in dimension with respect to a temperature and an original length of a biaxially oriented polyester film at a point where gradient changes from negative to positive in a horizontal temperature dimension varying curve thereof. CONSTITUTION:Biaxially oriented polyester film has a point (minimal point) at which gradient changes from negative to positive in a horizontal temperature dimension varying curve of the film when the curve is measured and a rate of change in dimension is -5-+5% with respect to an original length of the film at the minimal point with the temperature at the minimal point exceeding 200 deg.C. When the temperature at the minimal point is lower than 200 deg.C or the rate of change in dimension at the minimal point is lower than -5% even with the temperature exceeding 200 deg.C, shrinking of the film during the printing increases to cause wrinkles in the film, which disables printing. When the rate of change in dimension at the minimal point is larger than +5%, the elongation of the film increases as caused by heat applied in the coating of an ink layer and a rear treated layer to make the film sag. which causes a coating spot. This eliminates a wrinkling in the ribbon for heat transfer during the printing thereby enabling the obtaining of a clear print.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a thermal transfer ribbon having excellent printing performance and used as a transfer material for a thermal transfer printer.

[Conventional technology]

As a base film for ribbons for thermal transfer printers,
Those that specify surface roughness (JP-A-62-299389, JP-A-62-193889), and those that specify material and Young's modulus in the longitudinal direction (JP-A-62-1117).
No. 19) is known.

[Problem to be solved by the invention]

However, in recent years, as there has been a demand for higher printing speeds, the temperature of the thermal head during printing has increased, and as a result, the amount of heat received by the thermal transfer printer ribbon has increased. As a result, the film used as the base material of the ribbon becomes significantly deformed, causing the print to become unclear or wrinkles to form on the ribbon. In extreme cases, it may become impossible to print at all. Problems arose and this improvement was necessary.

An object of the present invention is to provide a thermal transfer ribbon that improves such problems and has excellent printing properties.

[Means to solve the problem]

The present invention measures the temperature dimensional change curve in the lateral direction of the biaxially oriented polyester film in a thermal transfer ribbon in which a biaxially oriented polyester film is used as a base layer and a thermal transfer ink layer is provided on one side of the base layer. When the curve changes from negative to positive, there is a point where the slope of the curve changes from negative to positive, the temperature at the chain point is 200°C or higher, and the dimensional change rate at the chain point with respect to the original length of the film is 15 to +5%. The gist of the present invention is a ribbon for thermal transfer, which is characterized by certain features.

In the present invention, polyester is a condensation polymer containing ester groups obtained from a dicarboxylic acid component and a diol component by a condensation method. As a dicarboxylic acid component,
Examples include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalene dicarboxylic acid, adipic acid, and sebacic acid. Examples of diol components include ethylene glycol, diethylene glycol, butanediol, hexanediol, neopentyl glycol, p-xylene glycol, 1,4-cyclohexane dimetatool,
Examples include polyalkylene glycols having an average molecular weight of 150 to 20,000.

In addition, the polyester used in the present invention has a particle size of 0.
It is better to contain 0.1 to 1.0% by weight of an inorganic or organic lubricant such as silicon dioxide, calcium carbonate, kaolin, fluororesin particles, and silicone particles having a diameter of 3 to 3 μm.

By adding these inorganic or organic lubricants, a biaxially oriented polyester film having an average surface roughness of 0.03 to 0.3 μm can be obtained. If the average surface roughness of the film is less than 0.03 μm, sufficient slipperiness will not be obtained and it will be difficult to wind up the film. Moreover, if the average surface roughness is larger than 0.3 μm, thermal conduction will deteriorate when printing with a thermal transfer printer, and the printing will become unclear. The particle size of the inorganic or organic lubricant added is 0. If it is 3μm smaller,
If a sufficiently large surface roughness cannot be obtained and the surface roughness is greater than 1.3 μm, the film is likely to break during the stretching process.

Further, the polyester used in the present invention may contain stabilizers, colorants, antioxidants, other additives, etc., as necessary.

In the present invention, the temperature dimensional change curve in the lateral direction of the film (hereinafter also referred to as rTMA curve) refers to the temperature and dimensional change curve (hereinafter also referred to as rTMA curve) of the film, which is obtained by gripping both ends of the film in the lateral direction and applying a certain constant load.
A curve drawn by heating a film at a constant temperature increase rate, with the temperature on the horizontal axis and the dimensional change rate relative to the original length of the film on the vertical axis.

The biaxially oriented polyester film used in the present invention has a point (hereinafter referred to as "minimum point") where the slope of the curve changes from negative to positive when the temperature dimensional change curve in the transverse direction of the film is measured. , the temperature at the minimum point (hereinafter also simply referred to as "temperature at the minimum point") is 200°C or higher, and the dimensional change rate at the minimum point with respect to the original length of the film (hereinafter also simply referred to as "the dimensional change rate at the minimum point") ) is -5 to +5
%. If the temperature of the minimum point is lower than 200°C, or if the dimensional change rate of the minimum point is lower than 5% even if it is above 200°C, the shrinkage of the film during printing will increase and wrinkles will occur in the film, making it impossible to print. It disappears. In addition, if the dimensional change rate of the minimum point is greater than +5%, the film will expand due to the heat applied when applying the ink layer or back treatment layer to the base film, causing the film to sag during coating. Prone to spots.

The thickness of the biaxially oriented polyester film used in the present invention is preferably 2 to 10 μm, and the F-5 value in the longitudinal direction is 1.
1 to 15 kg/mm2 is preferred.

If the thickness exceeds 10 μm, heat transfer takes time and is not suitable for high-speed printing. On the other hand, if the thickness is less than 2 μm, the strength is low and the processability is poor, which is not preferable. F-5
If the value is less than 11 kg/mm 2 , the ribbon stretches when it runs, resulting in unclear print or wrinkles. If the F5 value exceeds 15 kg/mm2, TM
Since the minimum point of the A curve is outside the appropriate range, wrinkles occur during printing.

Next, a method for manufacturing the biaxially oriented polyester film used in the present invention will be described. However, the present invention is not limited to the manufacturing method described below.

First, polyester is melted and molded into a film using a slit die. This film has a surface temperature of 20~
It is wound around a casting drum at 70°C and cooled and solidified to form an unstretched film. The unstretched film is stretched at a high magnification in multiple stages, i.e. 80 to 13
After heating to 0°C and stretching so that the total magnification is 4 to 7 times depending on the difference in circumferential speed between the rolls, it is heated to 90 to 120°C.
Stretch in the transverse direction by 3 to 4 times. Then 210-240
After heat treatment at 5 to 20 seconds at a temperature of 10 to 20 degrees Celsius lower than the heat treatment temperature, the film is shrunk by 3 to 10% in the transverse direction and then reheated to obtain a biaxially oriented polyester film.

In the present invention, the thermal transfer ink layer is not particularly limited, and any known one can be used. That is, it is composed of a binder component, a coloring component, etc. as the main components, and an appropriate amount of a softener, a plasticizer, a dispersant, etc. added as necessary. Specific examples of the above main components include known waxes such as carnauba wax and paraffin wax, and various low-melting point polymer substances as binder components, and carbon black as the main coloring agent, and various other dyes. Alternatively, organic or inorganic pigments may be used. Further, the thermal transfer ink layer may contain a sublimable dye.

The method of providing a thermal transfer ink layer on one side of the base material layer is as follows:
Known methods such as hot melt coating, gravure coating with a solvent added, reverse coating, slit die coating, and other solution coating methods can be used. In order to prevent sticking of the thermal head part, it is preferable to provide an anti-fusion layer of silicone resin, melamine resin, fluororesin, silicone oil, mineral oil, etc. on the side where the thermal transfer ink layer is not provided. Further, it is preferable to provide the anti-fusion layer before or after longitudinal stretching.

By doing so, it is possible to reduce the thermal history during processing into a transfer ribbon, and it becomes easy to maintain the temperature dimensional change characteristics of the biaxially oriented polyester film within the range of the present invention.

The method for measuring and evaluating characteristic values defined in the present invention will be described below.

(1) Temperature dimensional change curve Measured using TMA (thermal mechanical analyzer) manufactured by PERKIN ELMER.

However, the heating rate is 10°C/min, and the load is 200g/min.
It was set as mm2.

(2) F-5 value Set in a tensilon type tensile tester according to ASTM-D-882 so that the sample width is 10 mm % and the sample length is 100 mm, the tensile speed is 200 mm/min, the temperature is 20 ° C.
The corresponding strength of the film at 5% elongation is measured at a humidity of 65% RH.

(3) Printability Solid black was printed using a barcode printer (BC-8) manufactured by Oakes Co., Ltd., and the printability was evaluated based on the following criteria.

○: Clear printing △: Pitch deviation occurs in printing.

×: Ribbon is wrinkled and printing is disordered.

XX: The film was wrinkled during hot melt coating, and the transfer ink could not be applied uniformly.

〔Example〕

Hereinafter, the present invention will be explained in more detail based on Examples. However, the present invention is not limited to the following examples.

Example 1 Silicon dioxide with an intrinsic viscosity of 0.61 measured by melting 0-chlorophenol at 35°C and a particle size of 1.0 μm was
．． Polyethylene terephthalate containing 2% by weight was melted and extruded into a sheet using an extruder and a T-die, and the sheet was cooled and solidified in close contact with a water-cooled drum to obtain an amorphous sheet having a thickness of 30 to 120 μm. Multi-stage longitudinal stretching device, namely, the first stage is 2.2 times at 125 °C, the second stage is 1.1 times at 125 °C, and the third stage is 2.3 times at 115 °C, for a total of 5.6 times. Stepwise longitudinal stretching was performed.

On one side of this longitudinally stretched film, a coating material with the following composition was applied as an adhesion prevention layer using a gravure coater so that the coating thickness after drying was 15 μm, and then heated in a tenter oven at 11-0°C. Lateral stretching was performed 3.8 times. next,
After tension heat treatment at 225℃ with fixed length, 210℃
After shrinking by 6% in the transverse direction, a reheat treatment was performed to obtain a biaxially oriented polyester film with a thickness of 5 μm (excluding the coating film).

(Composition of paint) Acrylic ester 14.0% by weight Amino modified silicone 5.9% by weight Isocyanate
0.1 wt% water 80.0 wt% The obtained biaxially stretched oriented polyester film was measured for the F-5 value in the machine direction and the temperature dimensional change curve in the transverse direction, and the temperature at the minimum point and the temperature at the minimum point were measured. The dimensional change rate was determined. In addition, FIG. 1 is a lateral temperature dimensional change curve of the biaxially stretched oriented polyester film of this example,
Point A is the minimum point.

Next, transfer ink with the following composition was applied to a film thickness of 3°5 μm.
A transfer ribbon was prepared by coating the surface opposite to the anti-fusing layer using a hot melt coater so that the following properties were obtained.

(Composition of transfer ink) Carnauba wax 60.6% by weight Microcrystalline wax 18.2% by weight Vinyl acetate/ethylene copolymer 0.1% by weight Carbon black 21.1% by weight The printing properties of the prepared thermal transfer ribbon were evaluated. evaluated. Evaluation results first
Shown in the table.

Example 2 The intrinsic viscosity measured by melting 0-chlorophenol at 35°C was 0.61. Then, silicon dioxide with a particle size of 1.0 μm was
．． Polyethylene terephthalate containing 2% by weight was melted and extruded into a sheet using an extruder and a T-die, and the sheet was cooled and solidified in close contact with a water-cooled drum to obtain an amorphous sheet with a thickness of 30 to 120 μm. Multi-stage longitudinal stretching device, i.e., the first stage is 125°C, 2.1 times, the second stage is 125°C, 1.1 times
2.6 times in the third stage or 115°C, 3 times for a total of 6.0 times.
After performing stepwise longitudinal stretching, 1108
C. Lateral stretching was performed 3.8 times. Next, a tension heat treatment was performed at 230° C. with a fixed length, and then a reheat treatment was performed at 210° C. after shrinking by 6% in the transverse direction, to obtain a biaxially oriented polyester film with a thickness of about 5 μm. A coating material with the following composition was applied to one side of this film as an adhesion prevention layer, and the coating thickness after drying was 0. It was coated with a gravure coater to a thickness of 2 μm and dried at 80°C.

(Composition of paint) Acrylic ester 14.0% by weight Amino modified silicone 5.9% by weight Isocyanate
0. 1% by weight toluene 80.0% by weight Next, a transfer ink was applied in the same manner as in Example 1 to prepare a thermal transfer ribbon and evaluate it. The evaluation results are shown in Table 1.

Comparative Example 1 After longitudinal stretching at 90°C and 2.75 times, 100'C13,
Example 1 except that it was horizontally stretched at 4 times, longitudinally stretched again at 130°C and 2.0 times, and then subjected to tension heat treatment at 220°C.
A thermal transfer ribbon was prepared and evaluated in the same manner as described above. The evaluation results are shown in Table 1.

Comparative Example 2 After performing longitudinal stretching, transverse stretching, and tension heat treatment in the same manner as in Example 1, a transfer ribbon was produced and evaluated without performing reheat treatment. The evaluation results are shown in Table 1.

Comparative Example 3 After performing longitudinal stretching, transverse stretching and tension heat treatment in the same manner as in Example 1, the ribbon was subjected to reheat treatment after being shrunk by 12% in the transverse direction at 215° C. to produce a ribbon for thermal transfer and evaluated. The evaluation results are shown in Table 1.

〔Effect of the invention〕

The thermal transfer ribbon of the present invention does not cause wrinkles during printing and can provide clear printing.

[Brief explanation of the drawing]

FIG. 1 shows a transverse temperature dimensional change curve of the biaxially stretched oriented polyester film obtained in Example 1. In the figure, point A is the point where the slope of the curve changes from negative to positive (minimum point), point B shows the temperature at the minimum point, and point C shows the dimensional change rate with respect to the original length of the film at the minimum point. .

Claims (2)

[Claims] (1) In a thermal transfer ribbon having a biaxially oriented polyester film as a base layer and a thermal transfer ink layer provided on one side of the base layer, the temperature dimensional change curve in the lateral direction of the biaxially oriented polyester film was measured. Sometimes, there is a point where the slope of the curve changes from negative to positive, the temperature at the point is 200°C or higher, and the dimensional change rate of the film relative to the original length at the point is -5 to +5%. A thermal transfer ribbon characterized by: (2) The thickness of the biaxially oriented polyester film is 2 to 1
0 μm and vertical F-5 value of 11 to 15 kg
2. The thermal transfer ribbon according to claim 1, wherein the thermal transfer ribbon has a diameter of /mm^2.