JPH0441073B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a new thermal transfer recording medium that is capable of expressing gradations on plain paper, cannot be tampered with, and can obtain transferred recorded images with sufficiently high maximum density. [Prior Art] Conventionally, thermal transfer recording media, in which images are transferred and formed on plain paper using thermal printers, thermal facsimile machines, etc., have been made using heat-melting substances containing pigments or sublimation dyes, which are immersed by heating. A method is known in which an image is formed on a transfer recording medium by melting, sublimation, or volatilization. There have also been reports of materials in which a color forming agent and a color developer are added to a heat-melting material to develop and transfer color when heated. However, when using sublimable dyes, the dye density of the transferred image may change from moment to moment not only before recording but also after recording due to the dye's sublimation properties, resulting in poor storage stability. It was hot. In addition, the method of transferring by heating a heat-melting substance containing pigments, etc. has excellent storage stability, but on the other hand, the optical reflection density of the transferred image changes based on the change in the amount of image-forming substance per unit area of transfer. The essential drawback is that it is not possible to perform gradation expression. The heat-sensitive transfer recording medium containing a color former, color developer, etc. described in JP-A-56-120393 has a color former and a color developer contained in the same layer, so there is no difference between before and after recording. However, it has the disadvantage that it easily develops color when exposed to light, acid, alkali, pressure, etc., and has poor storage stability. The present inventors investigated a thermal transfer recording medium capable of expressing gradations by overcoming the above-mentioned drawbacks, and as a result, the patent application
No. 57-175138 and No. 57-218336 report that this can be achieved by separately providing a dye layer and a transfer layer on a support. However, even with these thermal transfer recording media, the maximum density of the transferred recorded image was still not necessarily sufficient. [Object of the Invention] The present invention has been made to solve the above-mentioned drawbacks, and its first purpose is to provide a thermal transfer recording medium that can form a transferred recorded image with a sufficiently high maximum density on plain paper or the like. It is to be. A second object of the present invention is to provide a heat-sensitive transfer recording medium capable of obtaining an even transferred recorded image. A third object of the present invention is to provide a thermal transfer recording medium that can control the density of a transferred recorded image as a function of heating temperature to obtain a transferred recorded image that has rich tone reproduction and cannot be tampered with. It is to be. A fourth object of the present invention is to provide a thermal transfer recording medium that has good storage stability and does not generate unnecessary transferred images due to pressure or the like before heating recording. A fifth object of the present invention is to provide a thermal transfer recording medium with high sensitivity during transfer recording. [Structure of the Invention] The present invention achieves the above object by coating a coloring agent layer containing a coloring agent and a binder on a support, and coating a heat-melting material containing a heat-melting substance on the coloring layer. In a heat-sensitive transfer recording medium coated with a color transfer layer, the solubility of the colorant in the binder and the solubility of the colorant in the heat-fusible substance are as follows, where X = heat-meltability of the colorant. The binder and the heat-fusible substance are selected so that the solubility of the transfer layer in the heat-fusible substance (140°C)/the solubility of the colorant in the binder (140°C) satisfies X≧2. The gist is what has been done. The present invention will be explained in detail below. [Colorant] The colorant used in the colorant layer of the present invention is a substance that can be dissolved or dispersed in the heat-fusible substance of the transfer layer during heating recording and has a color. It may be a substance that absorbs light at visible wavelengths (400 to 800 nm) or a substance that forms a substance that absorbs light in the visible light range. Synthetic pigments called dyes and pigments, natural pigments called animal pigments or vegetable pigments, etc., which are generally called pigments and are suitable for thermal transfer recording media, are used. Specifically, various dyes known in the art (for example, nitroso dyes, nitro dyes, azo dyes, stilbene azo dyes, ketoimine dyes, triphenylmethane dyes, xanthene dyes, acridine dyes, quinoline dyes, methine-polymethine dyes, thiazole dyes) , indamine dye,
Indophenol dyes, azine dyes, oxazine dyes, thiazine dyes, sulfur dyes, aminoketone dyes, oxyketone dyes, anthraquinone dyes, indigoid dyes, phthalocyanine dyes, etc. ); these leuco dyes, especially colorless or light-colored color-forming substances (e.g., triarylmethane compounds, diphenylmethane compounds, xanthene compounds, thiazine compounds, spiro compounds, etc.); and their color-forming properties. Acidic substances that color substances (e.g., phenol derivatives, aromatic carboxylic acids, etc.); Sublimable (including those that vaporize with melting or dissolution) dyes used for mordant dyeing, etc. (e.g., azo dyes, anthraquinone dyes, nitrogypants) enylamine dye, etc.); Although it is not a dye, it has light absorption in the visible light range (400 to 800 nm) and has a melting point of about 45 to 800 nm.
Examples include substances within the range of 120°C (eg, azobenzene derivatives, nitrobenzene derivatives, thiophenol derivatives, aniline derivatives, etc.). Among these, specific examples of those that are easily available on the market are as follows. In other words, the yellow pigment is Kayalon Polyester Light Yellow 5G.
-S (Nippon Kayaku), Oil Yellow S-7 (white clay),
Eisen Spiron GRH Special (Hodogaya), Sumiblast Yellow F5G (Sumitomo), Eisen Spiron Yellow GRH (Hodogaya), Hansa Yellow G (3),
Tartrazine lake and the like are preferably used. Red pigments include Diaceriton Fastred R (Mitsubishi Kasei), Dianics Brilliant Red BS-E (Mitsubishi Kasei), and Sumiplast FB.
(Sumitomo), Sumiplastrets HFG (Sumitomo), Kayalon Polyester Pink RCL-E (Nippon Kayaku),
Eisenspiron Red GEH Special (Hodogaya), Brilliant Carmine FB-Pure, Brilliant Carmine 6B (Sanyo Shiki), Alizarin Lake, 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, Cerulean Blue,
Sumika print cyanine blue GN-O (Sumitomo),
Phthalocyanine blue and the like are preferably used.
As the black pigment, carbon black, oil black, etc. are used. Particularly preferred are Sumiplast Yellow F5G, Sumiplast Stretch FB, and Sumiplast Blue 3R. [Binder] The binder used in the colorant layer of the present invention is selected from hydrophilic binders, hydrophobic binders, etc. according to the type of colorant used in the present invention. It is preferable that the material is a thermally non-melting material (does not melt even when heated for 0.5 seconds at 45 to 150° C.) and is preferably a high molecular compound or a natural substance. Specific examples of the heat-insoluble binder used in the present invention include polyvinyl chloride, polyvinyl acetate, polyvinyl fluoride, polyvinyl butyral, polyvinylidene chloride, polyvinyl alcohol, vinyl chloride/vinyl acetate copolymer, Vinyl resins such as vinyl chloride/vinylidene chloride copolymers; acrylic resins such as polyacrylic esters and polymethacrylic esters; resins such as ethyl cellulose and cellulose butyrate acetate; other polystyrene, polyethylene, and polyethylene/vinyl acetate copolymers. Examples include polymer compounds such as polymers, polyamides, and ABS resins, gelatin, and gum arabic. Among these, polyvinyl butyral, polyvinyl chloride, polyvinyl chloride/vinyl acetate copolymer, polyvinyl alcohol, and the like can be particularly preferably used. [Thermofusible substance] The thermofusible substance used in the thermofusible transfer layer of the present invention has a solubility of the binder in the substance that is at least twice as high as the solubility of the colorant in the binder of the colorant layer. It is selected from the following substances. That is, assuming the solubility ratio to be X, when It is selected so that ≧2. Here, the solubility of the colorant is measured as follows. While shaking or stirring 100 g of a heat-fusible substance or binder at 140° C., a predetermined amount of a coloring agent is sequentially added thereto. Solubility is the weight (measured in grams) of colorant added up to the point where the colorant can no longer be completely dissolved. The heat-melting substance used in the heat-melting transfer layer of the present invention may be selected from among low-melting substances capable of dissolving or dispersing the colorant when melted, so as to satisfy the above-mentioned solubility ratio. . [Examples of heat-melting substances] Specific examples include vegetable waxes such as carnapa wax, wood wax, auricilla wax, and espal wax, animal waxes such as beeswax, insect wax, serrata wax, spermaceti wax, paraffin wax, and microcrystalline wax. In addition to waxes such as petroleum waxes such as wax, ester wax, and oxidized wax, and mineral waxes such as montan wax, ozokerite, and ceresin; higher fatty acids such as palmitic acid, stearic acid, margaric acid, and behenic acid; palmityl alcohol, Higher alcohols such as stearyl alcohol, behenyl alcohol, marganyl alcohol, myricyl alcohol, eicosanol; higher fatty acid esters such as cetyl palmitate, myricyl palmitate, cecyl stearate, myricyl stearate; acetamide, propionic acid amide, palmitic acid amide, Amides such as stearic acid amide and amide wax; rosin derivatives such as ester gum, rosin maleic acid resin, rosin phenolic resin, and hydrogenated rosin; phenolic resin, terbene resin, cyclopentadiene resin,
Polymer compounds with a softening point of 50 to 120°C such as aromatic resins; higher amines such as stearoamine, behenylamine, and palmitin amyl; polyethylene oxides such as polyethylene glycol 4000 and polyethylene glycol 6000; It may be used or used in combination. Among these, higher amides such as palmitic acid amide, stearic acid amide, oleic acid amide wax, and higher fatty acids such as polyethylene glycol, stearic acid, and palmitic acid are particularly preferred. [Additives] Various additives may be added to the colorant layer. For example, 0.01% of carbon black, a thermofusible substance that can also be used in the thermofusible transfer layer.
Fine powder with a particle size of ~200μm, oils such as olive oil and silicone oil, etc. can be added. However, when a heat-fusible substance is used, it is necessary that the colorant solubility of the components other than the dye in the colorant layer is lower than that of the heat-fusible substance in the transfer layer. This colorant solubility ratio X is also desirably selected so that X≧2, particularly X≧5. Among the above-mentioned heat-fusible substances, those which can be preferably used as heat-fusible substances that can be added to the colorant layer include waxes such as vegetable waxes, animal waxes, petroleum waxes, and mineral waxes, and rosin derivatives. [Additives] The transfer layer of the present invention may contain various additives. For example, adding a polymeric substance as a thickener, or if the colorant contained in the colorant layer is a color former, adding a substance (color developer) that reacts with the color former to form a pigment as an additive. On the other hand, when the colorant in the colorant layer is a color developer, a color former that reacts with the color developer to form a dye may be added as an additive. Any layer constituting the thermal transfer recording medium of the present invention may contain appropriate additives, such as antioxidants, ultraviolet absorbers, color tone adjusting agents, etc., in one or more layers. may be included. The thermal transfer recording medium of the present invention may have a known subbing layer, overcoat layer, etc. Also,
An intermediate layer may be applied as necessary. [Support] The support for the thermal transfer recording medium of the present invention includes:
A support that has heat-resistant strength and high smoothness is desirable. Heat resistance strength requires strength that allows the support to maintain its toughness without becoming soft or plasticized due to the heating temperature of a heat source such as a thermal head, and smoothness requires that the transfer layer on the support has a good transfer rate. Sufficient smoothness is desired to show this. Smoothness is determined by a smoothness test using a Beck tester (JIS P8119) for 100 seconds.
The above is preferable, and when it is 300 sec or more, an image with a better transfer rate and reproducibility can be obtained. Materials include, for example, papers such as plain paper, synthetic paper, laminated paper, and coated paper, resin films such as polyethylene, polystyrene, polypropylene, and polyimide, paper-resin film composites, and metal sheets such as aluminum foil. Both are preferably used. The thickness of the support is preferably about 60 μm or less, particularly 3 to 40 μm, in order to obtain good thermal conductivity. [Colorant layer composition example] The composition of the colorant layer in the present invention is not limited, and generally the total composition amount is 100% (weight%, the same applies hereinafter).
1 to 90% colorant, 10 to 90% heat-insoluble binder
70%, the proportion of additives is 0-70%. It should be noted that if the content of the heat-insoluble binder exceeds 70%, the transfer efficiency will decrease, which is not preferable. The thickness of the colorant layer is not limited, and is generally about 0.5 to 20 μm, preferably about 0.5 to 10 μm, particularly preferably about 0.5 to 5 μm. [Example of Transfer Layer Composition] The composition of the transfer layer in the present invention is not limited, and generally has a ratio of 50 to 100% of the heat-fusible substance and 0 to 50% of the additive based on 100% of the total composition. The thickness of such a transfer layer is not limited, but generally
It is 15 μm or less, preferably 0.5 to 5 μm. [Example of Preparation of Recording Medium] The thermal transfer recording medium of the present invention may be prepared as follows. That is, the thermal transfer recording medium of the present invention can be formed by coating at least one colorant layer and one transfer layer on a support. To apply the colorant layer, for example, the colorant is added to a solution containing the binder, in which the colorant is dissolved or dispersed, or a binder heated and melted without using a solvent. This can be carried out by preparing a solution or dispersion and applying this solution onto a support using a commonly known coating device such as a wire bar, brush, or coater. At this time, a subbing layer may be coated on the support to improve adhesion with the colorant layer. Next, in order to apply a heat-fusible transfer layer on this colorant layer, a molten heat-fusible substance is applied directly, or a liquid obtained by dissolving or dispersing the heat-fusible substance in an appropriate solvent is used. This can be done by coating using a generally known coating device such as a wire bar. [Recording method] One method for recording using the thermal transfer recording medium of the present invention is to apply the colorant layer, etc. on the support using a device that can generate heat, such as a thermal head, a thermal pen, or an iron. Heating is performed from the non-supporting side, that is, from the support side. In addition to the above, a laser, a xenon lamp, etc. may be used as the heat source. Note that heating may be performed from the support side of the recording sheet such as plain paper. During this recording, the recording medium of the present invention and a recording sheet such as plain paper are overlapped. In the present invention, the colorant moves from the colorant layer to the heat-melting transfer layer through phenomena such as diffusion and elution in response to the heating temperature and heating time using a thermal pen, etc. The included hot melt material melts and dissolves or disperses the received colorant. Since the solubility of the colorant at this time is regulated as in the present invention, a recorded image with high density can be obtained. The transfer layer is transferred to a recording sheet such as plain paper, and returns to its original solid or semi-solid state when it returns to at least room temperature. The heating temperature at which thermal energy is applied to the thermal transfer recording medium of the present invention in accordance with the image information to be recorded is determined by its relationship with the heating time and the temperature of the heat-melting material used in the heat-melting transfer layer. The temperature is determined by taking into account the melting point, the type of colorant, etc., but it is preferably at room temperature or higher, and in practical terms, it is preferably higher than 45°C. [Effects of the Invention] Since the present invention has the above configuration and operation, the first, second and third objects of the present invention described above can be achieved, and a high density recorded image can be obtained on plain paper. In addition, a multi-gradation image can be obtained, and since it is highly sensitive, it is possible to save the amount of thermal energy required by a thermal pen or the like, or it is possible to record by heating in a short time, and it has good shelf life. [Example] Examples of the present invention are listed below, but the present invention is not limited to these Examples. Example 1 Add CI to a solution of 4 g of polyvinyl butyral (softening point 120°C) dissolved in 40 ml of methyl ethyl ketone.
Coating liquid 1 was obtained by adding 0.3 g of Solvent Blue 11. On the other hand, 8 g of Aramide O (manufactured by Lion Corporation) was added to a 5% S-40 (surfactant, manufactured by NOF Corporation) aqueous solution.
Add to 100ml and disperse with a ball mill to make coating solution 2.
I got it. Coating liquid 1 was applied to a polyethylene terephthalate film having a thickness of 10 μm using a wire bar to provide a coloring agent layer having a thickness of 2.9 μm after drying. Next, coating liquid 2 was applied onto the colorant layer using a wire bar while keeping the temperature at 50°C, and the film thickness after drying was
A transfer layer of 2.3 μm was provided to obtain thermal transfer recording medium No. 1 of the present invention. Furthermore, various heat-melting substances were substituted for Aramide O in the above heat-sensitive transfer recording medium as shown in Table 1 below to obtain heat-sensitive transfer recording media Nos. 2 to 4 in Table 1. On the other hand, as a comparative example, the above thermal transfer recording medium No. 1
Thermal transfer recording medium No. 5 was obtained by applying a colorant layer and a transfer layer in the same manner as described above, except that paraffin wax was used in place of Aramide O. The coated surfaces of these thermal transfer recording media were brought into close contact with each other on separate plain paper surfaces, and heated at 60°C.
When heated with an iron for 0.5 seconds at each temperature of 80°C, 100°C, and 120°C, a uniform blue transferred recorded image could be obtained on plain paper. The optical reflection density of these transferred recorded images was measured using a reflection densitometer (manufactured by Konishiroku Photo Industry Co., Ltd.). As is clear from Table 1, when the thermal transfer recording medium of the present invention (Nos. 1 to 4) is used, the temperature is lower than when the thermal transfer recording medium (No. 5) shown as a comparative example is used. It was possible to obtain a transferred recorded image with high optical reflection density. Furthermore, the maximum value of optical reflection density was also higher in the case of the present invention.

[Table] Example 2 2 g of polyvinyl butyral (softening point 120°C) and 2 g of paraffin wax were mixed with 40 ml of methyl ethyl ketone.
Coating solution 3 was obtained by adding 0.3 g of CI Solvent Blue 11 to the solution dissolved in 1 ml of the solution. On the other hand, 8 g of Aramide O was added to 100 ml of a 5% aqueous solution of S-40 and dispersed in a ball mill to obtain coating liquid 4. Coating liquid 3 was applied to a polyethylene terephthalate film having a thickness of 10 μm using a wire bar to provide a coloring agent layer having a thickness of 3.0 μm after drying. Next, coating liquid 4 was applied onto the colorant layer with a wire bar while keeping the temperature at 50°C, and the thickness after drying was determined.
A transfer layer of 2.1 μm was provided to obtain thermal transfer recording medium No. 6 of the present invention. Furthermore, various heat-melting substances were substituted for the paraffin wax and -Mide O in the heat-sensitive transfer recording medium as shown in Table 2 below, and Nos. 7 to 7 of Table 2 were used.
A thermal transfer recording medium No. 10 was obtained. On the other hand, as a comparative example, the above thermal transfer recording medium No. 6
A coloring agent layer and a transfer layer were applied in the same manner as described above, except that paraffin wax was used instead of Aramide O, to obtain thermal transfer recording medium No. 11. Further, using the same method, thermal transfer recording medium No. 12 was obtained using carnauba wax for the colorant layer and paraffin wax for the transfer layer. The coated surfaces of these thermal transfer recording media were brought into close contact with each other on separate plain paper surfaces and heated at 60°C and 80°C.
When heated with an iron for 0.5 seconds at temperatures of 100°C, 100°C, and 120°C, it was possible to obtain an even blue transfer recorded image on plain paper. The optical reflection density of these transferred recorded images was measured using a reflection densitometer. As is clear from Table 2, when the thermal transfer recording media No. 6 to No. 10 of the present invention were used, the temperature was lower than when the comparative thermal transfer recording media No. 11 and No. 12 were used. A transferred recorded image with high optical reflection density could be obtained. Furthermore, the maximum value of optical reflection density was also higher in the case of the present invention.

【table】

【table】

Claims (1)

[Claims] 1. A coloring layer containing a colorant and a binder is coated on a support, and a heat-melting transfer layer containing a heat-melting substance is coated on the coloring layer. In the heat-sensitive transfer recording medium, the solubility of the colorant in the binder and the solubility of the colorant in the heat-fusible substance are as follows: The binder and the heat-fusible substance are selected such that the solubility in the binder (140°C)/the solubility of the colorant in the binder (140°C) satisfies X≧2. A thermal transfer recording medium.