JPS6270086A - Color ink sheet for thermal transfer - Google Patents

Abstract

PURPOSE:To obtain an ink sheet having substantially the same applied energy and reflection color density characteristics for each color and thereby enable clear high-quality images to be recorded with excellent color balance and color reproduction properties, by setting the contents of sublimable dyes in an ink layer to be different to each other. CONSTITUTION:The heat generated by a thermal head 1 is transferred to an ink layer 4 through the base 3 of an ink sheet 2, whereby a sublimable dye 5 in the ink layer is sublimed or evaporated, and is transferred to a recording paper 6. Where the reflection color density per unit area or unit weight is substantially the same for each of the sublimable dyes 5 for colors such as yellow, magenta and cyan, the content of the sublimable dye 5 in the ink layer 4 is set to be lower as the sublimation rate of the dye is higher. Where the sublimable dyes 5 have guide different reflection color densities, the content of the sublimable due 5 in the ink layer 4 is set to be lower as the dye has a greater value of the product of the reflection color density and the sublimation rate or the amount of the dye 5 sublimed when being supplied with a specified quantity of thermal energy per unit area.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a color ink sheet for thermal transfer used for color recording by thermal transfer, and an ink sheet that is passed through a full-color printer using an electronic device such as a thermal head for the mark. This article concerns the composition of the ink.

[Background of the invention]

2. Description of the Related Art A thermal transfer recording method has been known as a method for recording color image information of televisions, video recorders, electronic cameras, etc. in full color via electrical signals. The heat-sensitive transfer color ink sheet (hereinafter abbreviated as ink sheet) used in this recording method is a coloring agent of at least three colors such as yellow, magenta, and cyan that has thermal transfer properties on a substrate such as paper or plastic sheet. A solid ink layer containing the solid ink is provided on the surface. This ink is melted by heat from a thermal head etc. controlled by image signals.
Rurui is a full-color image that is transferred onto recording paper by sublimating or evaporating the sublimable dye in the ink, and this transfer is performed one to three times on the same recording paper for the three colors yellow, magenta, and cyan. can be recorded. In particular, a transfer method in which the ink layer contains a sublimable dye and the sublimable dye is sublimated or evaporated by heat is excellent in terms of midtone reproducibility, color tone, and resolution. In addition to the sublimable dye, this ink layer contains at least a resin as a binder in order to improve the coating properties, film forming properties, adhesion properties, etc. of the ink to the substrate. However, depending on the quantitative ratio of sublimable dye and binder in the ink layer, and when the ink layer contains other additives such as highly thermally conductive fine particles or surface active agents, the amount of sublimable dye relative to the entire ink layer is Regarding the content rate, it is sufficient that the content rate of the sublimable dye is at least the minimum required content rate to transfer the required maximum color density for each color.
No other clear considerations were made. As a result, when various energies are applied to the ink sheet of each color, the relationship between the applied energy and the reflected color density of the sublimable dye transferred to the recording paper (hereinafter abbreviated as γ characteristic) differs depending on each color. In order to record images with excellent color balance and color reproducibility, a control circuit for color correction was required within the printer. Therefore, it has the drawback that the printer circuit becomes complicated and expensive, and at the same time,
The maximum reflected color density of i* has been restricted to the color with the lowest reflected color density. Further, when ink sheets with different γ characteristics are used, color balance and color reproducibility are often deteriorated. In addition, as a description of the technology related to this Dan's ink sheet, for example, JP-A-58-2
20788, JP-A-59-93391, JP-A-59-152895, and the like.

[Purpose of the invention]

An object of the present invention is to provide a color ink sheet for thermal transfer that records clear, high-quality images with excellent color balance and color reproducibility without requiring a complicated color correction control circuit.

[Summary of the invention]

When thermal energy is applied to an ink sheet containing a sublimable dye in the ink layer using a thermal head, etc., the reflected color density of the dye transferred onto the recording paper will change regardless of the applied energy, the material and thickness of the base of the ink sheet, etc. The sublimation rate of the sublimable dye mainly used.

Unit area and unit type of sublimable dye! Reflection color density around,
Content of sublimable dye contained in the ink layer and ink l-
It was discovered that the depth of the

Furthermore, regarding the thickness of the ink layer, if the ink layer contains a sufficient amount of sublimable dye to transfer the maximum reflective color density required for recording (usually between 1.0 and 2.0). discovered that the effect of ink layer thickness on reflected color density is negligible compared to the other three effects mentioned above.

The present invention is based on the unit area and unit type of sublimable dyes of each color such as yellow, magenta, cyan, etc. If the reflected color densities around the center are almost equal, the sublimability (sublimation rate) of each sublimable dye
If the above-mentioned reflected color density differs significantly depending on each sublimable dye, the larger the difference is, the sublimation rate or unit surface area that represents the above-mentioned reflected color density and sublimability is applied with specific thermal energy. An ink sheet used as a heat-sensitive transfer sheet for color recording, characterized in that the content of sublimable dye contained in the ink layer of each color is reduced as the product of the sublimation amount of the sublimable dye is larger when the product is sublimated. It is.

[Embodiments of the invention]

The implementation of the present invention will be explained below.

FIG. 1 shows an example of the structure of the ink sheet of the present invention. The heat from the thermal head 1 escapes through the base 3 of the ink sheet 2 and is conducted to the ink layer 4, and the sublimable dye 5 in the ink layer is sublimated or evaporated by the heat and transferred to the recording paper 6. In Figure 1, only one color transfer is explained, but using an ink sheet coated with each color such as ink color, magenta, cyan, etc. side by side, the ink sheet of each color is applied in the order in which it is coated. By applying a predetermined amount of thermal energy and transferring each color onto the recording paper in an overlapping manner, it is possible to record a color with a desired hue and density.

The base material is paper, polyester, or polyimide.

Materials that have been widely used in conventional thermal transfer ink sheets, such as cellulose polymer sheets, are used, and the adhesive for the ink layer is polyester, polyamide, or polycarbonate.

Polymer materials that have conventionally been widely used as binders, such as acrylic and cellulose polymers, can be used, and as the sublimable dye, various disperse dyes and basic dyes that can be sublimated can be used.

It is not particularly limited.

Also, regarding the structure of the ink sheet, in Figure 1 it consists of a base and an ink layer, and the only substances included in the ink layer are the sublimable dye and the binder.
However, the arrangement is not restricted by that description.The arrangement is such that a heat-resistant resin layer is provided on the surface of the ink sheet on the side of the thermal head to prevent stacking, and the ink sheet is There is no problem even if fine particles with high thermal conductivity are added to the jfi.

The recording paper 6 may also be subjected to various surface treatments such as resin coating, which is preferable in terms of image quality and image preservation, but is not particularly limited.

Next, specific examples will be described.

A polyamide resin as a binder and a sublimable dye having the chemical structural formula shown in Table 1 were weighed so that each color had the composition ratio shown in Table 1, and each was mixed with inglobil alcohol and toluene 3. The dispersion/dissolution in a mixed solvent of 1:1 was applied to a 6 μm polyester film using a wire bar, and dried to obtain an ink/sheet.

In addition.

The thickness of the ink layer at this time was approximately 1 μm.

As a comparative example, the same binder and sublimable dye as in the example were weighed at a weight ratio of 3:5, and an ink sheet was obtained in the same manner as in the example.

Using this two-doku ink sheet, yellow, magenta,
Each color of cyan was recorded on synthetic paper coated with polyester resin using a thermal head under certain recording conditions. Figure 2 shows the relationship between the head heating time (1 positive current pulse) and the reflection density on the recording paper of each color when the ink sheet of the example was applied, and Figure 3 shows the ink sheet of the comparative example. A similar relationship was shown when using ita. The unit area of each of the yellow, magenta, and cyan sublimable dyes used here,
unit! [Since the reflected color densities are almost the same, it can be confirmed from the results shown in FIG. 3 that the sublimability of the sublimable dyes used is in the order of cyan, magenta, and yellow. - In the ink sheet of Manfuku, the content of cyan dye is adjusted to be low and the content of yellow dye is adjusted to high, so the reflection after transfer of yellow, magenta, and cyan as shown in The color density is almost the same at any pulse width.

Using a row of ink sheets, yellow and magenta,
Magenta, cyan, and cyanide yellow.

For each combination of yellow, magenta, and cyan, the thermal head was energized with the same pulse width and transferred overlappingly, resulting in red and blue, respectively.

Clear colors of green and black were recorded. When each color was recorded in the same way using the ratio/pattern example ink 7-t, the result was 5.
The red color had a strong magenta color, and the blue, clean, and black colors had a strong cyan color, and colors with an imbalanced color were recorded.

- Also, when an image was recorded on the ink sheet of the example using electrical signals from an electronic camera, an image with almost the same color as the subject was obtained on the recording paper, that is, an image with poor color reproducibility was obtained. However, when Comparative Ink 7-T was used, an image with an overall tinge of magenta, especially cyan, was obtained, unlike the color of the subject.

Furthermore, even if a sublimable dye that differs from the chemical structural formula shown in Table 1 is used, the sublimation property or sublimation property of the sublimable dye, the unit area of the sublimable dye, and the degree of reflective coloration per unit weight and weight will vary. A sublimable image contained in the ink layer could be recorded.

Table 1 [Effects of the Invention] According to the present invention, an ink sheet with approximately equal applied energy and reflected color density characteristics for each color can be obtained, so color balance can be improved without using a complicated color correction control circuit. It has excellent color reproducibility and is effective in recording clear, high-quality images.

[Brief explanation of drawings]

FIG. 1 is a Wr side view showing the structure of an ink sheet when recording an image using a thermal head according to an embodiment of the present invention;
FIG. 2 is a diagram showing the relationship between the pulse width of the current applied to the thermal head and the reflection density of the color recorded on the recording paper when recording using the ink sheet of the embodiment of the present invention, and FIG. is a diagram showing a similar relationship when an ink sheet of a comparative example is used. 1... Thermal head, 2... Ink 7-t, 3...
...Base, 4...Ink If! , 5... Sublimation dye, 6... Recording paper. Kaya 1 map

Claims (1)

[Claims] 1. A color ink sheet for thermal transfer in which ink layers of multiple colors containing sublimable dyes are provided on a substrate, characterized in that the content of the sublimable dyes contained in the ink layers is varied. A color ink sheet for thermal transfer.