JPS63281890A - Thermal transfer recording medium - Google Patents

Abstract

PURPOSE:To prevent the discoloration of a printing image, by providing a heat-meltable ink layer containing a fluorescent substance and a heat-meltable ink layer containing a colorant and concealing extender pigment on a heat resistant support in succession or successively providing a heat-meltable ink layer containing the colorant and a heat-meltable ink layer containing the concealing extender pigment thereon. CONSTITUTION:A thermal transfer recording medium is formed by successively providing a heat-meltable ink layer containing a fluorescent substance 2 and a heat-meltable ink layer 6 containing a colorant 4 and concealing extender pigment 5 on a heat resistant support 1 or successively providing a heat-meltable ink layer 7 containing the colorant 4 and a heat-meltable ink layer 8 containing the concealing extender pigment 5 thereon. A wax and resin binder 9 fixes the fluorescent substance 2, colorant 4 and concealing extender pigment 5. In this thermal transfer recording medium, by making the ink layer 3 containing the colorant 4 in the recording layer optically opaque by the concealing extender pigment 5, the discoloration of a printing image is prevented while sufficient fluorescent intensity is kept without lowering a thermal transfer characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal transfer recording medium, and more particularly, to a thermal transfer recording medium for recording fluorescent prints on a transfer target by utilizing the heat-melting property of an ink layer having fluorescence. Regarding.

Long rice! As a thermal transfer recording medium, a coloring agent consisting of a dye and/or a pigment is placed on a heat-resistant support such as a polyester film,
It is known to provide a heat-melting ink layer containing a wax as a fixing agent and a resin binder. The print recording method using such a recording medium is to place a transfer object such as recording paper or an envelope on the heat-melting ink layer surface of the recording medium, and apply a thermal head from the support side of the recording medium to remove the ink layer in that area. This is done by melt-transferring onto the object to be transferred.

However, if the recorded matter thus obtained is used for special purposes, such as checks, postage stamps, etc., there is a risk that the printed image will be forged. Therefore, for example, a thermal transfer recording medium containing a fluorescent substance in the ink layer was developed in Japanese Patent Application Laid-Open No. 59-545.
Proposed in No. 98. In other words, when printing with a fluorescent material included in the ink layer as in this recording medium, the printed image is a normal colored image under normal conditions (no light of a specific excitation wavelength), but when irradiated with light of a specific excitation wavelength, the printed image is a normal colored image. Since it emits fluorescence when it is pressed, it is possible to prevent counterfeiting.

However, since fluorescent substances such as general fluorescent dyes and fluorescent pigments have low coloring power, it is necessary to use them in large quantities. However, since fluorescent substances are not sensitive to heat, using such a large amount of fluorescent substances deteriorates the thermal transfer properties of the ink layer, causing blurring, unevenness, etc. of printed images.

Therefore, based on the idea that the more fluorescent substances are present near the surface of a printed image, the more the fluorescence intensity increases, the inventors of the present invention previously colored the ink layer with a fluorescent substance-containing layer in Japanese Patent Application Laid-Open No. 61-57390. A thermal transfer recording medium was proposed in which the fluorescent substance-containing layer and the colorant-containing layer were provided on a support in this order.

However, not only recording media that contain fluorescent substances, but also recording media that do not contain fluorescent substances, when printing on colored sheets such as envelopes and securities as transfer objects, the ink print formed on the colored sheet In some cases, the image was discolored by the underlying colored sheet and did not appear to match the original color tone of the ink.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal transfer recording medium that can not only prevent forgery of printed images by providing sufficient fluorescence intensity, but also prevent discoloration of printed images even when a colored sheet is used as a transfer target. .

As shown in FIGS. 1 and 2, the thermal transfer recording medium of the present invention basically comprises a heat-resistant support 1, a heat-melting ink layer 3 containing a fluorescent substance 2, and a layer ( a) A heat-melting ink layer 6 containing a colorant 4 and a shadowing extender pigment 5 is provided, or (b) a heat-melting ink layer 7 containing a colorant 4 and a shadowing extender pigment 5 are provided. Thermal melt ink layer 8
It is characterized by sequentially providing the following.

Note that 9 is a wax or resin binder for fixing the fluorescent substance 2, the coloring agent 4, and the extender pigment 5.

Furthermore, in the present invention, wax is added between the support 1 and the fluorescent substance-containing layer 2 as shown in FIGS. And/or a base ink layer 1O containing a binder as a main component can be provided.

As described above, the thermal transfer recording medium of the present invention optically makes the colorant-containing ink layer of the recording medium proposed by the present inventors optically opaque with a shadowing extender pigment, thereby eliminating the need to reduce the thermal transfer characteristics. This prevents discoloration of printed images while maintaining sufficient fluorescence intensity.

To make the thermal transfer recording medium of the present invention, for example, in the case of the recording medium shown in FIG. 1, a fluorescent ink composition or solution containing a fluorescent substance, waxes, and a resin binder as main components is hot-melted on a heat-resistant support. A fluorescent material-containing ink layer is formed by coating or drying, and then a colored ink composition or solution containing a colorant, an extender pigment, waxes, and a resin binder as main components is hot-melt coated or coated and dried. to form an ink layer containing a colorant/extender pigment;
In the case of the recording medium shown in the figure, an ink layer containing a fluorescent substance is formed on a heat-resistant support in the same way as in the case of Fig. 1, and then colored with a colorant, waxes, and a resin binder as the main components. The ink composition or solution is hot-melt coated or applied and dried to form a colorant-containing ink layer, and then a white ink composition or solution containing an extender pigment, waxes, and a resin binder as main components is hot-melt coated or dried to form a colorant-containing ink layer. An extender pigment-containing ink layer may be formed by melt coating or coating and drying.Furthermore, in the case of the recording medium shown in FIG. 3, waxes and/or
Alternatively, after forming a base ink layer by hot-melt coating or coating and drying a colorless ink composition or solution containing a resin binder as a main component, a colorant/extender pigment is added thereon as in the case of Fig. 1. In the case of the recording medium shown in FIG. 4, a base ink layer is formed as in the case of FIG. 3, and then a fluorescent material-containing ink layer is formed thereon as in the case of FIG. , a colorant-containing ink layer and an extender-containing ink layer may be sequentially formed. Note that when forming the first ink layer in any recording medium, the hot melt coating method is usually used, and the second, When forming the third or fourth ink layer, a solution coating method is usually employed. In addition, in any layer forming method, ink application and, if necessary, drying must be performed as quickly as possible so that the components of the previously formed ink layer and the components of the ink layer formed thereon do not mix with each other due to diffusion. In addition, regarding the layer formation method, the relationship of specific gravity between fluorescent substance, colorant, and extender pigment is as follows: a) fluorescent substance>colorant=extender pigment, and b) in the case of fluorescent substance>colorant>extender pigment, these specific gravity relationships are as follows. The difference is utilized to form a fluorescent substance-containing ink layer rich in fluorescent substances, a colorant/extender pigment-containing ink layer rich in colorants and extender pigments, a colorant-containing ink layer rich in colorants, or an extender pigment-containing ink layer. be able to.

The thickness of each ink layer above is 1 to 1, excluding the base ink layer.
The thickness of the base ink layer is preferably about 4 μm, and the thickness of the base ink layer is preferably about 0.5 to 3 μm, but the thickness of the entire ink layer including the base ink layer is preferably about 2 to 15 μm. An additive such as a softener can be added as an optional component to each of the above ink layers.

In the thermal transfer recording medium as described above, the amount of fluorescent substance, colorant, and extender pigment used is 5 to 40%, 1 to 30%, and 1 to 30%, respectively, based on the weight of the total ink layer excluding the base ink layer.
The range of 10 to 25%, 3 to 15%, 1 to 15% is normal.
A range of 20% is preferred.

On the other hand, the amounts of waxes and resin binders used except for the base ink layer are generally 40 to 90% and 2 to 20%, respectively, based on the weight of the total ink layer excluding the base ink layer.
The amount of additive used is usually 2% or less based on the weight of the total ink layer including the base ink layer, preferably in the range of 5 to 85%, 3 to 15%.

Next, each component used in the present invention will be explained.

There are two types of fluorescent substances: inorganic and organic. Organic substances are further divided into (A) fluorescent pigment types, (B) fluorescent dye types, and (C) resin solid solution types of fluorescent dyes. Ru. As the inorganic fluorescent substance, ZnS”Cu mixture,
Zn5=CdS-Cu mixture, Cd5-Cu mixture, Z
Examples include n0-Zn mixture.

In addition, organic fluorescent substances of type (A) include Lumogen L Yellow, Lumogen L Brilliant Yellow,
Lumogen L Red Orange etc. are CB) (7) Thaibuti Hachioar 7 Bin (CI49005); Basic Yellow HG (CI46040); Fluorescein (CI45350); o-Damine B (CI451)
70); O-damine 6G (CI45160);z
Osin (C115380); General white fluorescent brightening agent, such as CI Fluorescent Brightening Agent 85, CI Fluorescent Brightening Agent 166, CI Fluorescent Brightening Agent 174; The above fluorescent dyes are made oil-soluble (and water-insoluble at the same time) with an organic acid. For example, Oil Pink #312 made with Rhodamine B and oil-solubilized, Varifast Red 1308 made with Rhodamine 6G made into oil-solubilized (
The above fluorescent dyes are made into lakes with metal salts and other precipitants, such as First Rose and First Rose Conc (made by Dainichiseika Kagaku Co., Ltd.) made of Rhodamine 6G. But again (
The fluorescent dye resin solid solution type (C) includes polymethacrylic acid ester solid solution, vinyl chloride-vinyl acetate copolymer solid solution, alkyd resin solid solution, aromatic sulfonamide resin solid solution, urea resin solid solution, and melamine. Examples include resin solid solutions, benzoguanamine resin solid solutions, and co-condensed solid solutions of the above resin raw materials. Among them, (C) fluorescent dyes are preferred from the viewpoint of color clarity, weather resistance, and fluorescence intensity when dispersed in a dispersion medium. The resin solid solution type is optimal.

Next, a method for producing a resin solid solution of fluorescent dye, which is most suitable as the fluorescent substance of the present invention, will be explained. This resin solid solution can be produced by a lump resin crushing method, an emulsion polymerization method, a resin precipitation method, or the like. Here, the lump resin crushing method (British Patent No. 845462) involves melting and mixing the resin and fluorescent dye, and then cooling and solidifying the resin and the fluorescent dye.
This is a method of crushing the resulting lump, and is called the emulsion polymerization method (
British Patent No. 822709) in a hot aqueous solution of fluorescent dye.
This is a method in which a resin powder produced by emulsion polymerization is added to absorb the dye into the resin powder, and then this is filtered and dried.
In addition, in the resin precipitation method, an aqueous solution of a water-soluble metal salt such as Af12(So, )3.8H20 is added to an aqueous solution in which a water-soluble salt of the resin and a fluorescent dye are dissolved, and the solution is reacted. If necessary, the solution is acidified to dissolve the The resin is coated with the fluorescent dye attached,
This method involves precipitating it as a metal salt and then filtering and drying it. The appropriate proportion of the fluorescent dye in the resin solid solution obtained as described above is about 0.1 to 5.0% by weight. Next, examples of manufacturing resin solid solutions of fluorescent dyes by the above-mentioned methods will be shown.

Example using bulk resin crushing method: (1) Benzyl sulfonamide formaldehyde resin 360 parts (2) B-state unmodified melamine formaldehyde resin 78.4 parts (3) Rhodamine B extra 4.02 parts (4) Rhodamine 6GDN extra 4 .02 parts (1) is melted at 125°C, and (2) is added and dissolved. When the resin becomes transparent at 135°C, the temperature is raised to 170-180°C. (3) and (4) are added and dissolved, cooled and solidified, and then crushed to obtain a resin solid solution that emits blue-red fluorescence.

Example using emulsion polymerization method: (1)'3,6-pisdiethylamino-9-(2'-carboxyphenyl)xanthenyl chloride 1 part (2) Diacetone alcohol 3 parts (3) Water
300 parts (4) formic acid
0.1 part (5) 100 parts (1) of polyvinyl chloride powder obtained by emulsion polymerization (2
), (3) and (4) and heat to 80-100°C. Add (5) and keep at 80-100°C while stirring to exhaust the dye. When washed with water and dried at 80 to 120°C, a magenta resin solid solution that emits red fluorescence is obtained.

Example using resin precipitation method: (1) Benzoic acid modified pentaerythritol-phthalic anhydride alkyd (acid value 91) 27.5% 100 parts (2
) Ammonium hydroxide (28%NHa) 25 parts (3
) Water 500 parts (4)
Rhodamine B base 1.8 parts (5) Rhodamine G 1 part (1) is dissolved in a mixture of (2) and (3) to make an ammonium salt (4
) and (5) are dissolved in this ammonium salt solution, this solution is diluted with 2100 parts of water, and 200 parts of lθ% aqueous solution of aluminum sulfate octadecahydrate is added dropwise to react with stirring.

If the reaction mixture precipitated here is alkaline, it must be made slightly acidic by adding dilute acid, for example 10% acetic acid, then the reaction mixture is heated at 50° C. with stirring for 1 hour, filtered and dried under vacuum. Then, it is crushed to obtain a resin (aluminum salt) solid solution that emits blue-red fluorescence.

The dyes or pigments used as colorants may be those commonly used in this field, i.e. the dyes include oil-soluble dyes such as Sumikalon Violet R8, Dianix Fast Violet 3R-FS, Kayalon Polyol Brilliant Blue N. -BGM (the above are anthraquinone dyes), Kayalon Polyol Brilliant Blue BM, Kayalon Polyol Dark Blue 28M, Sumikalon Diazo Black 5G, Mictacel Black 50H (
The above are azo dyes), Direct Dark Green B, Direct Brown M, Direct Fast Black D
(The above are direct dyes), Kayanol Schilling Cyanine 5R
(acidic dye), Sumicalyl Blue 6G, Eisenmalachite Green, Rhodamine B, Rhodamine 6G, Victoria Blue (the above are basic dyes), and the like. On the other hand, pigments include Victoria Blue Lake, metal-free phthalocyanine, phthalocyanine, Fast Sky Blue,
Permanent Red 4R, Brilliant First Scarlet, Brilliant Carmine BS, Permanent Red FB, Resole Red, Permanent Red F5
R, Brilliant Carmine 6B, Pigment Scarlet 3B, Rhodamine Lake B, Rhodamine Lake T, Alizarin Lake, Fast Red, Brightlet G
Toner, Lionor Red CP-A, Chrome Yellow (
yellow lead), zinc yellow zinc chromate (zinc yellow),
Lemon Yellow (barium chromate), Cadmium Yellow, Naphthol Yellow B, Hansa Yellow 5G, Hansa Yellow 3G, Hansa Yellow G, Hansa Yellow A, Hansa Yellow RN, Hansa Yellow R, Benzidine Yellow, Benzidine Yellow G, Benzidine Yellow GR, Permanent yellow NCG, quinoline yellow lake, first yellow, etc. can be mentioned. In the present invention, pigments are preferred from the viewpoint of light resistance, color migration properties, dissolution resistance, and the like.

The shadowing extender pigment is an inorganic or organic substance that has a different refractive index from other components contained in the extender-containing ink layer, such as colorants, waxes, binders, and additives (the refractive index is usually 1. 8 or more, preferably 2.3 or more).

Specific examples include titanium oxide, zinc oxide, calcium oxide, silica, magnesium oxide, boron nitride, and polytetrafluoroethylene.

Waxes used in each ink layer include carnauba wax, ochuri wax, microcrystalline wax, paraffin wax, ceresin wax, montan wax, candelilla wax, oxidized wax, rice wax, hydrogenated castor oil sand, shellac wax, Examples include easily heat-meltable waxes or resins such as wax wax, palm wax, beeswax, low molecular weight polyethylene, and polyvinyl stearate. Note that depending on the print recording conditions, the fluorescent ink may not be completely transferred, resulting in uneven fluorescence on the printed matter. In this case, you should use carnauba wax, hydrogenated castor oil hardened product, candelilla wax, etc., which have particularly excellent transferability, as the wax used for each ink, or delay the peeling of the head after printing a little later than usual. Good results are obtained.

As a binder, polyvinyl chloride, polyvinyl acetate, polyvinyl fluoride, polyvinyl butyral, polyvinylidene chloride, polyvinyl alcohol, vinyl chloride-vinylidene acetate copolymer, vinyl chloride-vinylidene chloride copolymer, polystyrene, polyethylene, Ethylene-vinyl acetate copolymer, polyamide, styrene-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer, acrylic resin, cellulose esters, cellulose ethers, petroleum resin, polycaprolactone, etc. can be easily heat softened or Examples include resins that can be melted.

In addition, as the softener which is an added component, there is used a substance that is oily at room temperature, such as liquid paraffin, mineral oil, whale oil, rapeseed oil, etc., which can prevent blocking.

As the heat-resistant support, polyester film, polypropylene film, polyimide film, polycarbonate film, glassine paper, condenser paper, and those obtained by further heat-resistant treatment are used.

The present invention will be explained below by way of examples. Note that both parts and percentages are based on weight.

Example 1 A 3.0 μm thick fluorescent material-containing ink layer was formed by hot-melt coating a fluorescent ink composition consisting of a melted dispersion having the following composition on the untreated surface of a 6 μm thick polyester film that had been heat-resistant treated on one side. .

Fluorescent ink composition (red-orange fluorescent): * Red-orange fluorescent substance (FZ3042 manufactured by Shinroihi) 22.5 parts Carbana wax & 1 15.0 parts Paraffin (+ap 68°C) 55.5 parts Ethylene-vinyl acetate together Polymer 5.0 parts Liquid paraffin
2.0 parts* benzylsulfonamide/formaldehyde resin solid solution of rhodamine B extra to rhodamine 6GDN mixed system (1:1 weight ratio). The amount of fluorescent dye is 1.8% of the total.

Next, a colored ink solution consisting of a ball mill dispersion having the following composition was applied onto this fluorescent material-containing ink layer and dried.
A μm thick ink layer containing a colored substance and an extender pigment was formed.

Colored ink solution (red): Lionol Red CP-A 10.0 parts (manufactured by Toyo Ink Co., Ltd.) Seiryoku Fast Yellow 2200M 5.0 parts (manufactured by Dainichiseika Chemical Co., Ltd.) Titanium oxide 10.0 parts Carnauba wax 13.0 paraffin (mp
68℃) 55.0 parts Ethylene-vinyl acetate copolymer 5.0 parts Liquid paraffin
2.0 parts isooctane
A commercially available transfer paper for PPC (plain paper copying machine) (
The heating energy applied to the thermal head was 0.45 m j /dot (8 dots/m!) by stacking the white and brown envelopes respectively.
+ head) and head pressure is approximately 500 g
When printing was performed with a thermal head from the recording medium side under the condition of /cd, red printed images of the same tone were formed on both wave transfer members.

It was also confirmed that when this printed image was irradiated with ultraviolet light using a black light, it emitted reddish-orange fluorescence.

Example 2 After forming a 2.5 μm thick fluorescent material-containing ink layer on the untreated surface of a heat-resistant treated polyester film in the same manner as in Example 1, a colored ink solution made of a ball mill dispersion having the following composition was applied thereon. It was dried to form a 2.5 μm thick colorant-containing ink layer.

Colored ink solution (red): Lionol Red CP-A 10.0 parts (manufactured by Toyo Ink Co., Ltd.) Seiryoku Fast Yellow 2200M 5.0 parts (manufactured by Dainichiseika Co., Ltd.) Carnauba wax 15.0 parts Paraffin (up 68°C) ) 63.0 parts ethylene-vinyl acetate copolymer 5.0 parts liquid paraffin
2.0 parts isooctane
700 parts Next, a white ink solution consisting of a ball mill dispersion having the following composition was applied onto this colorant-containing ink layer and dried to form an extender pigment-containing ink layer having a thickness of 1.5 μm.

White ink solution: Titanium oxide 15.0 parts Carnauba wax 15.0 parts Paraffin (mp
68℃) 63.0 parts ethylene-vinyl acetate copolymer 5.0 parts liquid paraffin
2.0 parts isooctane
700 copies of the thus obtained thermal transfer recording medium were used to print on transfer paper and brown envelopes in the same manner as in Example 1, and the color tone and fluorescence of the printed images were examined, and exactly the same results as in Example 1 were obtained. Ta.

Example 3 A colorless ink composition consisting of a melt dispersion having the following composition was hot-melt coated on the untreated surface of the same heat-resistant treated polyester film as in Example 1 to form a base ink layer with a thickness of 3.0 μm.

Candelilla wax 25.0 parts Paraffin (mp 68°C) 70.0 parts Liquid paraffin 5.0 parts Next, on this base ink layer, a fluorescent ink solution consisting of a whole mill dispersion having the following composition was applied and dried to a thickness of 1.5 μm. A thick phosphor-containing ink layer was formed.

Fluorescent ink solution (red-orange fluorescence): Red-orange fluorescent substance (F Z3042 manufactured by Shinroihi) 30.0 parts Carnauba wax Ni11 13.0 parts Paraffin (++p 68°C) SO, O parts Ethylene-vinyl acetate copolymer 5. 0 parts liquid paraffin
2.0 parts isooctane
Further, on this fluorescent substance-containing ink layer, an ink layer containing a 2.5 μm thick coloring substance/extender pigment was formed in the same manner as in Example 1.

Using the thus obtained thermal transfer recording medium, printing was carried out on transfer paper and brown envelopes in the same manner as in Example 1, and the color tone and fluorescence of the printed images were examined, and exactly the same results as in Example 1 were obtained.

Example 4 A 3.0 μm thick base ink layer and a 1.5 μm thick base ink layer were applied to the untreated side of a heat-resistant treated polyester film in the same manner as in Example 3.
After forming a fluorescent substance-containing ink layer with a thickness of m, a 2.5 μm thick colorant-containing ink layer and a 1.5 μm thick extender pigment-containing ink layer were formed on this fluorescent substance-containing ink layer by the same method as in Example 2. Formed.

Using the thus obtained thermal transfer recording medium, printing was carried out on transfer paper and brown envelopes in the same manner as in Example 1, and the color tone and fluorescence of the printed images were examined, and exactly the same results as in Example 1 were obtained.

Effects Since the thermal transfer recording medium of the present invention has the above-described structure, sufficient fluorescence intensity can be obtained without deteriorating the thermal transferability, and therefore, it is possible to not only prevent forgery of printed images but also to use as transfer objects such as securities and envelopes. Even when a colored sheet such as the above is used, discoloration of the printed image can be prevented and a printed image with the same color tone as the original ink can be obtained.

[Brief explanation of the drawing]

1 to 4 are diagrams showing the structure of an example of the thermal transfer recording medium of the present invention. 1... Heat-resistant support 3... Heat-melting ink layer 6 containing fluorescent substance 2...
・Thermofusible ink layer 7 containing colorant 4 and shadowing extender pigment 5...Thermofusible ink layer 8 containing colorant 4...
Heat-melting ink layer 9 containing a shadowing extender pigment 5...base ink layer containing waxes and resin binder bones

Claims (1)

[Claims] 1. A heat-melt ink layer containing a fluorescent substance is provided on a heat-resistant support, and (a) a heat-melt ink layer containing a coloring agent and a shadowing extender pigment is provided thereon, or (b) A thermal transfer recording medium comprising a heat-melting ink layer containing a colorant and a heat-melting ink layer containing a shadowing extender pigment, which are sequentially provided.