JPH0336039B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for manufacturing a thermal transfer recording medium. More specifically, the present invention relates to a method for manufacturing a thermal transfer recording medium, which can reduce manufacturing costs and provide a thermal transfer recording medium having a coloring material layer that does not easily peel off.

[Prior Art] A thermal transfer recording medium has been conventionally used as a recording medium for transferring and forming an image on a recording sheet such as plain paper by a thermal printer, a thermal facsimile, or the like. This thermal transfer recording medium has at least one coloring material layer on a support, and the coloring material layer is, for example, a layer containing a dye such as a pigment and a heat-melting substance. There is. Further, as the support, films having excellent dimensional stability are used in order to obtain good reproducibility of the dye transfer image obtained from the color material layer coated thereon. When the support is, for example, a polyethylene terephthalate film, a biaxially stretched film is used to obtain its dimensional stability.

A thermal transfer recording medium is manufactured by coating a coloring material layer on such a support having excellent dimensional stability by a hot melt method or a solvent method. On such a formed film support,
The coloring material layer is applied in a coating process that is completely different from the process for forming the film support, leading to an increase in manufacturing costs.

On the other hand, thermal transfer recording media require adhesion between the support and the coloring material layer coated thereon in order to prevent film peeling during handling. According to the manufacturing method, there was also the problem of delamination.

[Object of the Invention] An object of the present invention is to provide a method for manufacturing a thermal transfer recording medium that can significantly reduce manufacturing costs.

Another object of the present invention is to provide a method for producing a thermal transfer recording medium that improves the adhesion of a coloring material layer to a film support and prevents film peeling during handling and scumming during transfer recording. It is to be.

Other objects of the invention will become apparent from the following description of the specification.

[Summary of the Invention] As a result of intensive research, the present inventors have achieved the above object by coating a coloring material layer on a stretched polymer film before the molecular orientation of the film is completed during film production. The inventors have discovered that this can be achieved, leading to the present invention.

[Structure of the invention] The present invention will be explained in more detail below.

The polymerized films of this invention are formed from any hydrophobic synthetic polymeric material and are dimensionally stable films after orientation and heat setting. Suitable polymeric materials include polyesters such as polyethylene terephthalate, copolyesters and polycarbonates. A preferred polymeric material is polyethylene terphthalate.

The polymeric film must be dimensionally stable under the conditions of thermal transfer so that the dye transfer image obtained from the dye layer provided on the film support according to the present invention is not distorted. Although some uniaxially oriented polymer films are sufficiently dimensionally stable, polymer films are commonly oriented biaxially to achieve the desired dimensional stability. When a polyethylene terephthalate film is used, dimensional stability is generally achieved by biaxial orientation.

Generally, biaxially oriented polymer films are oriented by first stretching in the longitudinal direction and then in the transverse direction. The biaxially oriented film is then heat set by heating while restricting the film against longitudinal and lateral shrinkage. Additional longitudinal stretching can also be used to improve longitudinal tensile strength, either before or after heat setting. A method to improve longitudinal tensile strength is to first stretch in the transverse direction and then in the longitudinal direction.

Yet another method of biaxial orientation of the film is simultaneous longitudinal and transverse stretching.

All of the above methods of biaxially orienting polymeric films are known, and any of these methods may be used in practicing the present invention. Molecular orientation is carried out by stretching at a temperature below the softening point of the film but above its secondary transition temperature.

A typical method used in the present invention to biaxially orient a polyethylene terphthalate film cast on a drum and rapidly cooled to below 80°C is as follows. That is, the film was stretched longitudinally between two sets of high and low speed nip rolls or capstan rolls giving a stretching ratio of 2.5:1 to 4.0:1 at temperatures ranging from 80 to 100°C; Stretching in the transverse direction at a temperature higher than that used for the longitudinal stretching. The transverse stretching is carried out in a tenter with a stretching ratio of 2.5:1 to 4.0:1. The film is then heat set by heating at a temperature in the range of 150 DEG to 250 DEG C. for 0.5 to 5 minutes with limited shrinkage in both directions, preferably while holding the film in a tenter apparatus. The heat set film can then be longitudinally stretched, if desired, at temperatures in the range of 100 DEG to 200 DEG C. using stretch ratios of 1.5:1 to 8.0:1.

According to the present invention, the colorant layer composition is applied before molecular orientation is completed, ie, before the unidirectional or bidirectional stretching operation used to orient the film. Before orientation takes place, for example in the case of biaxially oriented polyethylene terephthalate films, [1] after the polymer film has been cast on a quench drum and before a first stretching in the longitudinal or transverse direction (usually the former); [2] Apply the coloring material layer composition to the film, or
It can be applied before preheating after the next stretching, [3] it can be applied during preheating, [4] or it can be applied to the second layer of biaxially oriented film.
Apply after the next stretching. Among these, the most preferable application time is [3], followed by the above-mentioned [2],
[1] and [4] are preferred in this order. In addition, when coating a coloring material layer by a solvent method, it is preferable to carry out said [2].

Suitable techniques for applying colorant layers to polymeric films are known in the art, and these techniques can also be used in the present invention. For example, the coloring material layer is formed by hot-melt coating with a composition containing at least a colorant, a binder, and a softener, or by solvent coating with a coating solution obtained by dissolving or dispersing the composition in an appropriate solvent. This is a layer with a thickness of 15μ or less. As a method for applying the coloring material layer of the present invention, any known technique such as a reverse roll coater method, an extrusion coater method, a gravure coater method, etc. can be adopted.

When the colorant layer of the present invention is stretched after its application, the final thickness after stretching is
It is preferable to apply the coating so that the thickness is 15μ or less. In addition, in order to prevent the clips that sandwich the polymer film from being contaminated by the coloring agent of the coloring material layer during the lateral stretching process, etc., 2.0 to 3.5 cm of each side edge of the polymer film is coated. It is preferable not to apply a coloring material layer.

As the binder, materials that can be easily melted by heat are preferably used, such as waxes such as carnauba wax, auricule wax, and microcrystalline wax, or resins such as low molecular weight polyethylene and vinyl polystearate. Ru. Furthermore, polymeric compounds such as polyvinyl acetate, polystyrene, styrene-butadiene copolymers, cellulose esters, cellulose ethers, and acrylic resins are also suitably used as binders together with the above-mentioned heat-meltable substances. As softeners, vegetable oils such as castor oil, linseed oil, and olive oil, animal oils such as whale oil, and mineral oils are preferably used. As the coloring agent, various dyes or pigments that have been widely used in the art can be used without any particular restrictions. For example, a substance that can be dissolved or dispersed in the binder in the colorant layer when melted, has a color, and is solid at room temperature may be used as a colorant, and various dyes or pigments known in the art may be used as the colorant. Can be used. Specifically, the following can be mentioned. In other words, the yellow pigment is Kayalon Polyester Light Yellow 5G.
-S (Nippon Kayaku), Oil Yellow S-7 (white clay),
Eisenspiron GRH Special (Hodogaya), Sumiplast Yellow FG (Sumitomo), Eisenspiron Yellow GRH (Hodogaya), etc. are preferably used. As red pigments, Diaceriton Fastred R (Mitsubishi Kasei), Dianics Brilliant Red BS-E (Mitsubishi Kasei), Sumiplast Stretch FB (Sumitomo), Sumiplast Stret HFG (Sumitomo),
Kayalon Polyester Pink RCL-E (Nippon Kayaku), Eisen Spiron Red GEH Special (Hodogaya), etc. are preferably used. Blue pigments include Diaceritone Fast Brilliant Blue R (Mitsubishi Kasei) and Dianics Blue EB-E.
(Mitsubishi Kasei), Kayalon Polyester Blue B-
SF Conch (Nippon Kayaku), Sumiplast Blue 3R
(Sumitomo), Sumiplast Blue G (Sumitomo), etc. are preferably used. In addition, as the yellow pigment, Hansa Yellow G (3), Tartrazine Lake, etc. are used, and as the red pigment, brilliant carmine
FB-Piure (Sanyo Dyes), Brilliant Carmine 6B (Sanyo Dyes), Alizarin Lake, etc. are used, and as blue pigments, Cerulean Blue, Sumikaprint Cyanine Blue GN-O (Sumitomo), Phthalocyanine Blue, etc. are used, and black As the pigment, carbon black, oil black, etc. are used. In addition, metal particles or metal oxides may also be used.

These binders, softeners, and colorants are used in amounts of 10 to 85 parts, 0.5 to 5 parts, and 2 to 85 parts, respectively, per 100 parts (parts by weight, same hereinafter) of the total amount of the heat-melting color material layer.
It is preferable to set the blending ratio to 25 parts, and in that case, the melt transferability of the formed heat-melting coloring material layer is extremely good.

In the present invention, a subbing layer may be provided during the stretching process of the polymer film so as not to react with the solid colorant in the colorant layer of the polymer film.

Examples of the undercoat layer include silicone resin, melamine resin, polyvinacetal resin, polyethylene, polyvinyl chloride, polyvinylidene chloride, fluorine resin, etc., and the undercoat layer is applied before the coloring material layer is applied. This can be carried out in the same manner as the colorant layer coating technique.

[Effects of the Invention] According to the present invention, the coloring material layer is coated on the stretched polymer film before the molecular orientation of the film is completed before the film is formed. When coating the color material layer in steps 1], [2], and [3], it is not possible to obtain the desired thin color material layer even if the coating is applied in a thick range where the film thickness is relatively easy to control. You can also get the effect that you can do it.

[Example] Examples are given below, but the embodiments of the present invention are not limited thereto.

EXAMPLE 1 Polyethylene terephthalate was melt extruded through a slot die onto a rotating drum where it was rapidly cooled to an amorphous state. The amorphous film was stretched in the longitudinal direction between slow and high speed rollers at a temperature of about 90°C with a draw ratio of about 3:1. Next, the film was coated with a heat-melting colorant layer composition having the composition ratio shown below at about 50° C. using a reverse roll coater.

[Thermofusible coloring material layer composition]

Carnauba wax 8 parts by weight Wax (Nisseki Micro Wax 155) 8 parts by weight Olive oil 1 part by weight Carbon black 3 parts by weight Toluene 80 parts by weight The dry film thickness of the coloring material layer was 15μ.

Thereafter, the film coated with the colorant layer was passed through a tenter oven, where it was stretched in the transverse direction at a stretching ratio of about 3:1 while being heated to 100°C. The film was heat set in a tenter oven at a temperature of approximately 200°C with limited longitudinal and lateral shrinkage.

In this way, a heat-sensitive transfer recording medium was obtained in which a 5μ thick coloring material layer was coated on a 6μ thick polyethylene terephthalate film support.

Example 2 Polyethylene terephthalate was melt extruded through a slot die onto a rotating drum where it was rapidly cooled to an amorphous state. The amorphous film was stretched in the longitudinal direction between slow and high speed rollers at a temperature of about 90°C with a draw ratio of about 4:1. Next, this amorphous film is advanced to a preheating process immediately before entering the transverse stretching process, and at this stage, a meltable colorant layer composition having the following composition is applied at 110°C using a reverse roll coater.
It was applied to a thickness of 16μ. The coated film was then stretched in the transverse direction in a tenter at a stretch ratio of about 4:1 and heat set at a temperature of about 200° C. while limiting shrinkage in the longitudinal and transverse directions. After cooling,
The film sample was wound up with a roller.

In this way, a heat-sensitive transfer recording medium was obtained in which a 4μ thick heat-fusible coloring material layer was coated on a 5.5μ thick film support.

[Thermofusible coloring material layer composition]

Paraffin (Paraffin Solid 32030, manufactured by Kanto Kagaku Co., Ltd., melting point 62-64℃) 40 parts by weight Carnauba wax (melting point 82-86℃) 30 parts by weight Wax (Sanwax 171P, manufactured by Sanyo Chemical Co., Ltd.,
Softening point: 105°C) 15 parts by weight Carbon black 15 parts by weight When a thermal transfer recording test was conducted on each sample obtained in Examples 1 and 2 using a thermal head (driver equipped type), it was found that the composition of each of the above coloring material layers was A dye image was obtained on the recording sheet (plain white paper with a Beck smoothness of 500 seconds) having the same transfer density as when the dye was applied onto each of the heat-set polymer films.

Claims (1)

[Claims] 1. A method for producing a thermal transfer recording medium, which comprises coating a coloring material layer on a stretched polymer film before the molecular orientation of the film is completed during film formation.