JPH041712B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a thermal transfer recording medium.
The present invention relates to a thermal transfer recording medium capable of obtaining a dye transfer image with no gloss.

[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 includes, for example, a layer containing a coloring agent made of a dye such as a pigment and a heat-fusible substance. etc. are known. In addition, films with excellent surface smoothness and dimensional stability are used as the support in order to obtain good reproducibility of the dye transfer image obtained from the color material layer coated on the support. There is.

Dye transfer images (printed images) obtained from such conventional thermal transfer recording media have extremely smooth and glossy surfaces, which causes significant eye strain when the records need to be read for a long time. Additionally, there is a drawback that the dye transfer image cannot be seen depending on the condition of the light source. In this regard, JP-A-56-164891 proposes mixing a matting agent into the coloring material layer. However, according to this technology, compared to a thermal transfer recording medium that has a coloring material layer that does not contain a matting agent, the thickness of the coloring material layer must be increased in order to obtain a dye transfer image of the same density. Therefore, there is a drawback that the transfer sensitivity is lowered.

[Object of the Invention] An object of the present invention is to provide a thermal transfer recording medium capable of obtaining a matte dye transfer image without causing a decrease in sensitivity during thermal transfer.

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 inventor has discovered that a heat-sensitive transfer recording medium having a heat-sensitive transferable color material layer containing a colorant on a support has two particle size distribution curves for the colorant. or more mountains, and the two or more mountains are
0.01~5mμ range, 5~30mμ range, 40
~90 mμ, and the 2
The interval in average grain size between the mode of the largest peak and the mode of the next largest peak among the three or more peaks is 7~
It has been discovered that the above object can be achieved by having a diameter of 30 mμ, leading to the present invention.

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

The thermal transfer recording medium of the present invention has at least one coloring material layer on a support, and the particle size distribution curve of the coloring material contained in the coloring material layer has at least two peaks.

The colorant used in the present invention preferably has an average particle diameter ratio within the following range. In other words, the average particle size of the large particle size group (b)/the average particle size of the small particle size group (a) = 1.
2 or more, more preferably b/a=1.6 or more.

Further, the particle size distribution curve of the coloring agent such as carbon black used in the coloring material layer of the present invention only needs to have at least two peaks.
range of 0.01 to 5 mμ, range of 5 to 30 mμ,
It exists in any range of 40 to 90 mμ, and may be used in combination. Note that methods for obtaining colorants such as carbon black that have two or more peaks (for example, three peaks) are not limited to the above-mentioned mixed use, but also include changing the temperature of the processing furnace or the amount of oxygen gas. It is also possible to produce a coloring agent such as carbon black having a bimodal distribution or trimodal distribution by changing it during the manufacturing process, and use this.

In the present invention, the interval in average particle size between the mode of the largest peak of two or more peaks in the particle size distribution curve and the mode of the next largest peak is 7 to 30
It is in the range of mμ.

As the coloring agent of the present invention, 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 moltenly dissolved or dispersed in the binder in the colorant layer, has a color, and is solid or semi-solid at room temperature may be used as a colorant, such as various pigments known in the art. can be used. Specifically, the following can be mentioned. That is, the yellow pigments include Kayalon Polyester Light Yellow 5G-S (Nippon Kayaku), Oil Yellow S-7 (white clay), Eizenspiron GRH Special (Hodogaya), Sumiplast Yellow FG (Sumitomo), and Eizenspiron. Ron Yellow
GRH (Hodogaya), etc. are preferably used. As a red pigment, Diaceriton Fastred R
(Mitsubishi Kasei), Dianics Brilliant Reed
BS-E (Mitsubishi Kasei), Sumiplast Stretch FB (Sumitomo), Sumiplast 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), Dianics Blue EB-E (Mitsubishi Kasei), Kayalon Polyester Blue B-SF Conc (Nippon Kayaku), and Sumiplast Blue 3R (Sumitomo). , Sumiplast Blue G (Sumitomo), etc. are preferably used. In addition, as a yellow pigment, Hansa Yellow 3G,
Tartrazine Lake, etc. are used, and red pigments include Brilliant Carmine FB-Pure (Sanyo Pigment), Brilliant Carmine 6B (Sanyo Pigment),
Alizarin lake, etc. are used, as the blue pigment, cerulean blue, Sumikaprint Cyanine Blue GN-O (Sumitomo), phthalocyanine blue, etc. are used, and as the black pigment, carbon black, oil black, etc. are used. In addition,
Metal particles or metal oxides may also be used. Among these, a combination of colorants having the same color tone is preferred because it does not cause color turbidity. In the present invention, the expression "similar in tone" refers to the same color having the same tone within the hue as visually recognized. For example, in terms of absorption wavelength, the difference in the main absorption wavelength is
Those within the range of 10 nm, preferably 5 nm are considered to be of the same type.

The coloring material layer of the present invention contains one or more heat-melting substances. As this heat-fusible substance, conventionally known heat-fusible substances can be used without any particular limitations.

The thermofusible substance preferably used in the present invention is
Softening point (measured by ring and ball method) or melting point (Yanagimoto
Measured value by MPJ-2 type) is 120℃ or less,
Particularly preferred are those having a melting point of 50 to 120°C.

Specific examples of thermofusible substances preferably used in the present invention include paraffin waxes such as paraffin wax and micro wax, natural waxes such as beeswax, carnauba wax, and wood wax, and esters such as Hoechst wax. waxes, higher fatty acids such as stearic acid, palmitic acid, behenic acid, myristic acid, 1,20-eicosandioic acid, higher alcohols such as stearic alcohol and palmityl alcohol, stearamide,
Higher amides such as oleamide and palmityroamide, butyl stearate, ethyl palmitate,
Examples include esters such as myristyl stearate.

The composition ratio of the coloring material layer of the present invention is 50 to 50% of the heat-melting substance.
90% (weight%, the same applies hereinafter), small particles of colorant
2.5 to 15%, large colorant particles 2.5 to 15%, resins 5 to 30%, and the composition ratio of the colorant small particles to large particles is 1:10 to 10:1. , preferably in the range of 2:8 to 8:2.

The color material layer of the present invention may contain various additives in addition to the above components. For example, examples of the thermally conductive substance include metals with good thermal conductivity such as aluminum, copper, and zinc. Such a thermally conductive substance promotes the heat conduction effect of melting, softening, or sublimating the coloring material layer by heat. Furthermore, vegetable oils such as castor oil, linseed oil, and olive oil, animal oils such as whale oil, and mineral oils may be suitably used as softeners.

Coating methods suitable for coating a coloring material layer on a support by solvent coating, hot melt coating, etc. are known in the art, and these techniques can also be used in the present invention. For example, the coating solution of the present invention can be solvent coated using any known technique such as a reverse roll coater method, an extrusion coater method, a gravure coater method, or a wire bar coating method, and then the solvent can be removed to form a coating of 15μ or less. A color material layer can be applied.

Further, the thermal transfer recording medium of the present invention has at least one coloring material layer of the present invention, and in addition,
It may have other constituent layers such as a subbing layer, an intermediate layer, or an overcoat layer. That is, for example, examples of the undercoat layer include silicone resin, melamine resin, polyvinia sector resin, polyethylene, polyvinyl chloride, polyvinylidene chloride, fluororesin, etc., and the coating of the undercoat layer is colored. This can be done prior to applying the material layer.

Note that the support used as a base material for the thermal transfer recording medium of the present invention is preferably a support that has heat-resistant strength, high dimensional stability, and high surface smoothness.
Heat resistance strength requires strength and dimensional stability to maintain the toughness of the support without becoming softened or plasticized by the heating temperature of a heat source such as a thermal head, and surface smoothness requires heat melting on the support. It is desired that the layer containing a sexual substance has sufficient smoothness to exhibit a good transfer rate. The smoothness is preferably 100 seconds or more in a smoothness test (JIS P 8119) using a Beck tester, and when it is 300 seconds or more, images with better transfer rate and reproducibility can be obtained. Materials include, for example, papers such as plain paper, condenser paper, laminated paper, and coated paper; resin films such as polyester, polycarbonate, polyethylene, polyethylene terephthalate, polystyrene, polypropylene, and polyimide; and paper-resin film composites. Metal sheets such as aluminum foil are preferably used. The thickness of the support is generally about 60 microns or less, preferably 2 to 20 microns, in order to obtain good thermal conductivity. Furthermore, in the thermal transfer recording medium of the present invention, the structure of the back side of the support may be arbitrary.

[Effects of the Invention] According to the present invention, since the particle size distribution curve of the colorant has at least two peaks, the above-mentioned object of the present invention can be achieved, and the eyes will not get tired even when reading for a long time. In addition, high sensitivity allows high-speed recording (printing).

[Example] Examples are given below, but the embodiments of the present invention are not limited thereto. Note that "part" used below refers to "important part".

Example 1 50 parts of carnauba wax, low molecular weight polyethylene
Add 20 parts of olive oil and 10 parts of olive oil to a xylene dispersion containing 10 parts of carbon black small particles with an average particle size of 30 mμ and 10 parts of carbon black large particles with an average particle size of 56 mμ, and stir at 60 ° C. A coating liquid for a coloring material layer was obtained. This coating solution was dried on a polyethylene terephthalate film support with a thickness of 5.2 μm using a wire bar to obtain a thermal transfer recording medium sample of the present invention having a coloring material layer with a thickness of 3.1 μm. An attempt was made to record this sample on plain paper using a high-sensitivity thermal printer (a prototype equipped with a thin-film line thermal head with a heating element density of 8 dots/mm). As a result, a clear dye transfer image with low gloss and easy to read was obtained. This dye transfer image
The glossiness was measured at an angle of 75° C. using the method described in JIS Z 8741 and found to be 7.4%.

Example 2 In Example 1, the colorant was mixed with 5 parts of carbon black small particles having an average particle size of 5 mμ and 5 parts of carbon black small particles having an average particle size of 30 mμ.
A thermal transfer recording medium sample of the present invention having a coloring material layer of the same thickness was obtained in the same manner except that the mixture was replaced with a mixture of 15 parts of large carbon black particles. When printing was attempted on this sample in the same manner as in Example 1, a clear dye transfer image with little gloss and easy to read was obtained. The glossiness of this dye transfer image was measured using the same method as in Example 1 and was found to be 8.6%.

Example 3 In Example 1, the colorant was replaced with carbon black, each consisting of a small particle group with an average particle diameter of 5 mμ, a medium particle group with an average particle diameter of 30 mμ, and a large particle group with an average particle diameter of 56 mμ.
A sample of the thermal transfer recording medium of the present invention having a coloring material layer of the same thickness was obtained in the same manner except that the mixture was replaced with a mixture of 1 and 2. When printing was attempted on this sample in the same manner as in Example 1, a clear dye transfer image with little gloss and easy to read was obtained. The glossiness of this dye transfer image was measured using the same method as in Example 1 and was found to be 6.5%.

Comparative Example 1 A comparative thermal transfer recording medium having a coloring layer of the same thickness as in Example 1 except that the colorant was replaced with a xylene dispersion in which 20 parts of carbon black with an average particle size of 30 mμ was dispersed. A sample was obtained. When printing was attempted on this sample in the same manner as in Example 1, only a glossy dye transfer image was obtained. The glossiness of this dye transfer image was measured using the same method as in Example 1 and was found to be 28%.

Comparative Example 2 In Example 1, the colorant was mixed with an average particle size of 25 mμ.
5 parts of carbon black small particles and an average particle size of 30m
A comparative thermal transfer recording medium having a coloring material layer of the same thickness was obtained in the same manner except that the mixture was replaced with a mixture of 15 parts of carbon black large particles of μ.

When this sample was printed in the same manner as in Example 1, a dye transfer image was obtained that was glossy and difficult to read. The glossiness of this dye transfer image was measured in the same manner as in Example 1 and was found to be 25%.

Comparative Example 3 In Example 1, the colorant had an average particle size of 5 mμ.
5 parts of carbon black small particles and an average particle size of 40m
A comparative thermal transfer recording medium having a coloring material layer of the same thickness was obtained in the same manner except that the mixture was replaced with a mixture of 15 parts of carbon black large particles of μ.

When this sample was printed in the same manner as in Example 1, a dye transfer image was obtained that was glossy and difficult to read. The glossiness of this dye transfer image was measured in the same manner as in Example 1 and was found to be 24%.

Claims (1)

[Claims] 1. In a heat-sensitive transfer recording medium having a heat-sensitive transferable color material layer containing a colorant on a support, the particle size distribution curve of the colorant has two or more peaks, and the two or more peaks are 0.01 ~5mμ range, 5~30mμ
exists in the range of 40 to 90 mμ, and the interval in average particle size between the mode of the largest peak and the mode of the next largest peak among the two or more peaks is 7 to 30 mμ. A thermal transfer recording medium characterized by: