JP3773810B2 - Fluorescence image forming method and printed matter - Google Patents

Description

【０１２８】
【発明の効果】
以上説明したように、本発明に係る蛍光画像形成方法によれば、可視光の照射に対してほぼ無色であり且つ紫外線の照射に対して互いに異なる色調の蛍光を発する有機蛍光剤を用いて、可視光では認識できない任意の色調を有する蛍光画像を形成することができ、しかも、得られる蛍光画像は耐擦過性に優れ、蛍光の色調コントロールも容易である。従って、印画物に高い偽造防止性を付与することができる。
【図面の簡単な説明】
【図１】本発明に係る熱転写シートの一例を示す模式的断面図である。
【図２】本発明に係る熱転写シートの別の一例を示す模式的断面図である。
【図３】本発明において面積階調により混色の蛍光色を生じさせる原理を説明する図である。
【符号の説明】
１…基材フィルム
２…熱溶融性蛍光インク層
３…離型層
４…耐熱層
５…熱溶融ブラックインキ層
６…転写性保護層
７…熱溶融性インキ層[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a thermal transfer method that contributes to prevention of counterfeiting of important documents such as securities, banknotes, and other important documents, cards such as ID cards and credit cards, a thermal transfer sheet used in the method, and The present invention relates to a printed matter created using
[0002]
[Prior art]
Various methods for preventing forgery of securities, banknotes, ID cards, credit cards and the like are known. For example, special color materials such as gold and silver transfer foils, pastel and pearl inks, and fluorescent color inks that cannot be reproduced with the three primary colors, are printed so that it is difficult to copy Thus, characters and images are formed or hologram images that require advanced manufacturing techniques are provided.
[0003]
In addition, it uses a fluorescent agent that emits visible light fluorescence when irradiated with ultraviolet rays, although it has almost no absorption for visible light and is almost colorless or white. There is also a method of forming an image and verifying the authenticity by verifying the presence or absence of a fluorescent image using an ultraviolet lamp or the like.
[0004]
Japanese Patent Application Laid-Open No. 62-111800 discloses a heat-sensitive transfer sheet using such a fluorescent agent. JP-A-8-207452 discloses a special color transfer layer containing a heat-transferable fluorescent dye on a continuous sheet together with three primary colors of red, blue and green, or in addition to this, a heat-transferable dye layer of black. A partitioned thermal transfer sheet is disclosed.
[0005]
Even if a fluorescent agent that emits visible light fluorescence when irradiated with ultraviolet rays while having almost no absorption with respect to visible light as described above and is almost colorless or white, a color material that is completely or substantially the same is used. If used, it is possible in principle to forge. Actually, the color tone of currently known colorless fluorescent agents is roughly divided into three colors, red, blue and green, but the color tone of each color fluorescent agent is similar even if the manufacturer is different. Yes. For example, a colorless fluorescent agent that emits red light generally has an emission wavelength of around 615 nm, and it is difficult to visually distinguish them. Therefore, a counterfeiter may be able to perform counterfeiting by obtaining a similar colorless fluorescent agent rather than the colorless fluorescent agent itself used for “genuine”.
[0006]
Japanese Patent Laid-Open No. 7-125403 discloses that two or more types of ink images are partially overlapped on a transfer medium by hot melt transfer using an ink containing a fluorescent pigment or a fluorescent dye as a dye that emits light by ultraviolet rays. A method of forming a print image that is formed and emits light of three or more colors by ultraviolet rays is described.
[0007]
Japanese Patent Application Laid-Open No. 2000-158823 describes a method of forming a fluorescent full-color image using a hot-melt transfer sheet having a plurality of colors of inorganic colorless fluorescent agent transfer layers.
[0008]
However, in these methods, in order to form a fluorescent full-color image, a plurality of colors of ink are printed on top of each other, so that a layer having a multilayer structure is formed by laminating ink layers on the surface to be printed. There is a problem that the scratch resistance is lowered.
[0009]
In addition, the amount of ultraviolet rays that reach the lower ink layer is less in the layered layers of multiple color ink layers than the upper layer side, resulting in lower light emitting capacity on the lower layer side. There is also a problem that it is difficult to adjust to the above.
[0010]
[Problems to be solved by the invention]
The present invention has been accomplished in view of the above circumstances, can form a fluorescent full-color image excellent in scratch resistance, and can freely adjust the color tone of a mixed color combining two or more fluorescent colors. It is an object of the present invention to provide a fluorescent image forming method and a printed matter having an advanced anti-counterfeit function.
[0011]
[Means for Solving the Problems]
  In order to solve the above problems, the fluorescent image forming method provided by the present invention contains an organic fluorescent agent that is substantially colorless to visible light irradiation and emits fluorescence of different colors to ultraviolet light irradiation.One or two or more thermal transfer sheets in which two or more colors of heat-melting fluorescent ink layers made of heat-melting fluorescent ink are provided on the same or different base film, and one or more according to image information to be printed Heating the heat-meltable fluorescent ink layer of two or more of the above-described thermal transfer sheets to transfer the heat-meltable fluorescent ink to the image forming area on the printing surfaceIt is characterized by forming an image that emits a plurality of fluorescent colors and / or a fluorescent color that is a mixture of them when subjected to ultraviolet irradiation by adhering so that the dots of each color do not overlap by the dot matrix method.
[0012]
When multiple colors of fluorescent ink are printed, there is a problem that the ink layers of the respective colors are stacked and the scratch resistance is lowered. In addition, when multiple colors of fluorescent ink are overprinted, the amount of ultraviolet rays reaching the lower ink layer is smaller than that on the upper layer, and the light emission capability on the lower layer is reduced. As a result, the color tone due to the mixture of fluorescent colors is controlled. There is also the problem that it becomes difficult.
[0013]
  In contrast, in the method according to the present invention, each colorHeat meltingFluorescent ink is attached by the dot matrix method so that the dots of each color do not overlap, so that color mixing is generated by so-called area gradation, and the color tone of the fluorescent color is controlled by changing the area ratio of the dot group of each color. A layer stack is not formed. Accordingly, the abrasion resistance is not lowered due to the lamination of the ink layer, and the fluorescent color tone of the lower layer is not lowered due to the lamination of the ink layer, so that the color tone of the fluorescent color can be easily controlled. Therefore, high anti-counterfeiting properties can be imparted to the printed matter.
[0014]
  Of the above fluorescent image forming methodconcreteIn one aspect, two or more colors of heat-fusible heat-soluble fluorescent inks comprising an organic fluorescent agent containing an organic fluorescent agent that is substantially colorless to visible light irradiation and emits fluorescence of different colors to ultraviolet light irradiation. Two or more fluorescent colors can be printed using a combination of a plurality of thermal transfer sheets each having a fluorescent ink layer provided on a separate substrate film.
[0015]
In this case, one of the plurality of thermal transfer sheets is overlaid so that the heat-melting fluorescent ink layer of the heat-transfer sheet faces the image forming area on the printing surface, and the heat-melting fluorescent ink layer is stacked. Heat according to the image information to be printed and heat-meltable fluorescent ink to the image forming area on the printing surface so that it does not overlap with dots of other colors that have already been formed or will be formed The heat-melting fluorescent ink layer is separated after heat transfer, and then the heat-melting fluorescent ink layer of the other heat transfer sheet is sequentially used in the same manner to heat-transfer the heat-melting fluorescent ink to the same image forming area. Thus, it is possible to form an image that emits a plurality of fluorescent colors and / or a fluorescent color that is a mixture of them when subjected to ultraviolet irradiation.
[0016]
  In addition, another method of forming the fluorescent imageSpecific aspectsIn two or more colors of heat-melting fluorescent inks comprising a heat-melting fluorescent ink containing an organic fluorescent agent that is substantially colorless to visible light irradiation and emits fluorescence of different colors to ultraviolet light irradiation It is also possible to print two or more fluorescent colors using a thermal transfer sheet in which layers are provided in the surface order on the same substrate film.
[0017]
In this case, one of the heat-meltable fluorescent ink layers provided on the thermal transfer sheet is overlapped with the image forming area on the printing surface, and the heat-meltable fluorescent ink layer is printed. Heat according to the information to transfer heat-meltable fluorescent ink to the image forming area on the printing surface using the dot matrix method and so as not to overlap with dots of other colors that have already been formed or will be formed in the future By separating the heat-melting fluorescent ink layer from the heat-melting fluorescent ink layer in the same image forming region using the other heat-melting fluorescent ink layers in the same thermal transfer sheet in the same manner. It is possible to form an image that emits a plurality of fluorescent colors and / or a fluorescent color that is a mixture thereof when subjected to ultraviolet irradiation.
[0018]
The thermal transfer sheet is provided with one or more of a colorant transfer layer, a hot-melt black ink layer, or a transferable protective layer in the surface order together with a hot-melt fluorescent ink layer, and the same thermal transfer sheet is provided. It is preferable to use one or two or more of a fluorescent image and an image that can be recognized by irradiation with visible light, a visible image of black ink, or a transferable protective layer. As the colorant transfer layer, for example, a dye layer capable of sublimation heat transfer or a heat-meltable ink layer capable of melt heat transfer can be provided. Further, the colorant transfer layer may be provided in a surface sequential manner together with other transfer layers by arbitrarily selecting two or more of yellow (Y), magenta (M), cyan (C) or other color tone. .
[0029]
DETAILED DESCRIPTION OF THE INVENTION
The present invention is described in detail below. The present invention provides the following first and second fluorescent image forming methods.
[0030]
(First fluorescent image forming method)
In the first method, an image to be printed with two or more color fluorescent inks containing organic fluorescent agents that are substantially colorless to visible light irradiation and emit fluorescence of different colors to ultraviolet light irradiation. According to the information, the fluorescent color that is a plurality of fluorescent colors and / or their mixed colors when irradiated with ultraviolet rays by adhering to the image forming area of the printing surface by the dot matrix method so that the dots of each color do not overlap. Is formed.
[0031]
When multiple colors of fluorescent ink are printed, there is a problem that the ink layers of the respective colors are stacked and the scratch resistance is lowered. In addition, when multiple colors of fluorescent ink are overprinted, the amount of ultraviolet rays reaching the lower ink layer is smaller than that on the upper layer, and the light emission capability on the lower layer is reduced. As a result, the color tone due to the mixture of fluorescent colors is controlled. There is also the problem that it becomes difficult.
[0032]
On the other hand, in the first method according to the present invention, each color fluorescent ink is attached by the dot matrix method so that the dots of each color do not overlap each other, so-called area gradation is generated, and the dot group of each color Since the color tone of the fluorescent color is controlled by changing the area ratio of the ink layer, the laminated portion of the ink layer is not formed. Accordingly, the abrasion resistance is not lowered due to the lamination of the ink layer, and the fluorescent color tone of the lower layer is not lowered due to the lamination of the ink layer, so that the color tone of the fluorescent color can be easily controlled.
[0033]
This method can be applied to an image forming method in which a colorless fluorescent agent is dissolved and dispersed in some matrix of a colorless fluorescent agent to form an ink, and the colorless fluorescent agent is attached to the surface to be printed together with the ink, for example, a method such as hot melt transfer or ink jet.
[0034]
In the following, the first method will be described using a case of performing hot melt transfer as a representative example.
[0035]
When the first method of the present invention is carried out by a thermal transfer method, the heat melting property contains an organic fluorescent agent that is substantially colorless to visible light irradiation and emits fluorescence of different colors to ultraviolet light irradiation. Two or more fluorescent colors can be printed using a combination of a plurality of thermal transfer sheets in which two or more heat-melting fluorescent ink layers made of fluorescent ink are provided on different base films.
[0036]
In this case, one of the plurality of thermal transfer sheets is overlaid so that the heat-melting fluorescent ink layer of the heat-transfer sheet faces the image forming area on the printing surface, and the heat-melting fluorescent ink layer is stacked. Heat according to the image information to be printed and heat-meltable fluorescent ink to the image forming area on the printing surface so that it does not overlap with dots of other colors that have already been formed or will be formed The heat-melting fluorescent ink layer is separated after heat transfer, and then the heat-melting fluorescent ink layer of the other heat transfer sheet is sequentially used in the same manner to heat-transfer the heat-melting fluorescent ink to the same image forming area. Thus, it is possible to form an image that emits a plurality of fluorescent colors and / or a fluorescent color that is a mixture of them when subjected to ultraviolet irradiation.
[0037]
FIG. 1 is a schematic cross-sectional view of an example (101) of a thermal transfer sheet used in the present invention. A thermal transfer sheet 101 is provided with a heat-meltable fluorescent ink layer 2 on one surface of a base film 1 with a release layer 3 interposed therebetween, and sticking with a heating element such as a thermal head on the other surface side of the base film 1. The structure is provided with a heat-resistant layer for preventing or improving slipperiness. The hot-melt fluorescent ink layer is coated on a base film by dissolving or dispersing any colorless fluorescent agent such as red (R), blue (B) or green (G) in a hot-melt vehicle (matrix). By heating this, the colorless fluorescent agent can be transferred to the printing surface together with the hot-melt vehicle. A heat-melting fluorescent ink layer containing a colorless fluorescent agent that has a configuration as shown in FIG. 1 and contains a color tone different from that of the heat-melting fluorescent ink layer of another thermal transfer sheet is provided. Two or more fluorescent colors can be printed using a plurality of thermal transfer sheets.
[0038]
Further, in the present invention, heat of two or more colors composed of a hot-melt fluorescent ink containing an organic fluorescent agent that is substantially colorless to visible light irradiation and emits fluorescence of different colors to ultraviolet light irradiation. It is also possible to print two or more fluorescent colors using a thermal transfer sheet in which a meltable fluorescent ink layer is provided in the same order on a same substrate film.
[0039]
In this case, one of the heat-meltable fluorescent ink layers provided on the thermal transfer sheet is overlapped with the image forming area on the printing surface, and the heat-meltable fluorescent ink layer is printed. Heat according to the information to transfer heat-meltable fluorescent ink to the image forming area on the printing surface using the dot matrix method and so as not to overlap with dots of other colors that have already been formed or will be formed in the future By separating the heat-melting fluorescent ink layer from the heat-melting fluorescent ink layer in the same image forming region using the other heat-melting fluorescent ink layers in the same thermal transfer sheet in the same manner. It is possible to form an image that emits a plurality of fluorescent colors and / or a fluorescent color that is a mixture thereof when subjected to ultraviolet irradiation.
[0040]
According to the method of printing two or more fluorescent colors using a single thermal transfer sheet, two or more color hot-melt fluorescent ink layers are sequentially provided on a continuous sheet-like thermal transfer sheet and wound into a roll. It can be attached to a thermal transfer printer and printed with a plurality of fluorescent colors from this roll of thermal transfer sheet, which is effective for downsizing the printer and simplifying its structure. Also, by providing a thermal transfer sheet with a plurality of heat-melting fluorescent ink layers, a colorant transfer layer such as a heat-melting black ink layer, a sublimation dye layer, a heat-melting ink layer, or a transferable protective layer. In addition to fluorescent colors, a general colorant and protective layer that can be visually recognized by irradiation with visible light can be transferred to the same printing surface from a single heat transfer sheet, making the printer smaller and simpler. It is more effective. When a colored image that can be recognized by irradiation with visible light is formed on the same printed surface with a fluorescent color image, a fluorescent agent transfer process using a hot-melt fluorescent ink layer, a hot-melt black ink layer, a sublimation dye layer, Either of the color material transfer processes using a colorant transfer layer such as a meltable ink layer may be performed first, but a colored image is printed first so that the fluorescent color image is not concealed by a normal colored image. It is preferable to print a fluorescent color image.
[0041]
FIG. 2 is a schematic cross-sectional view of an example (102) of the thermal transfer sheet used in this case. The thermal transfer sheet 102 has a yellow (Y), a magenta (M), and a cyan (C) heat-meltable ink layer 7 (7Y, 7M, 7C), The molten black ink layer 5, red (R), blue (B) and green (G) heat-meltable fluorescent ink layers 2 (2R, 2B, 2G) and the transferable protective layer 6 are arranged in the order of planes. In other words, the same base film is arranged in parallel along the film feeding direction during thermal transfer.
[0042]
In the thermal transfer sheet 102 of FIG. 2, the thermal meltable ink layer 7, the thermal melt black ink layer 5, and the transferable protective layer 6 are also formed on the base film together with the thermal meltable fluorescent ink layer 2. Is provided. Further, the heat-resistant layer 4 is provided on the back side of the base film of the thermal transfer sheet 102 in the same manner as the thermal transfer sheet 101 of FIG.
[0043]
In the present invention, as the base film constituting the thermal transfer sheet, a film material having heat resistance and film strength that can withstand the thermal transfer process can be appropriately selected and used. It can be used without problems in the invention. Specific examples of preferable substrate films include thin papers such as glassine paper, condenser paper, and paraffin paper; high heat resistance such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polyphenylene sulfide, polyether ketone, and polyether sulfone. Stretched or unstretched films made of various plastic materials such as polyester, polypropylene, polycarbonate, cellulose acetate, polyethylene derivatives, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, polymethylpentene, ionomer; and combinations of the above materials The laminated film can be mentioned.
[0044]
The thickness of the base film can be appropriately selected according to the material so that the physical properties such as the strength and heat resistance of the film are appropriate, and usually a thickness of about 1 to 100 μm is preferably used.
[0045]
In the present invention, the heat-meltable fluorescent ink layer is a layer formed by dissolving or dispersing one or more fluorescent agents in a heat-meltable vehicle, and is substantially colorless to visible light irradiation, It contains at least an organic fluorescent agent (that is, a colorless fluorescent agent) that emits visible color fluorescence and a binder resin for irradiation. In the present invention, “substantially colorless” means that it is difficult to visually recognize that the ground color of the surface to be printed exists in any color tone when printing is performed using the fluorescent agent. The content is defined as meaning that it cannot be distinguished at all.
[0046]
Various colorless fluorescent agents are known. In the present invention, any organic colorless fluorescent agent is not particularly limited, and commercially available ones can also be used effectively. The colorless fluorescent agent includes an organic substance and an inorganic substance. In the present invention, an organic colorless fluorescent agent is used. The organic colorless fluorescent agent is compatible with the binder resin to make the heat-meltable ink transparent, so it is excellent in invisibility under visible light, and when printing is performed using the organic colorless fluorescent agent, It is difficult to find that a fluorescent agent print for preventing counterfeiting is applied in a normal use state of the printed matter.
[0047]
In contrast, inorganic colorless fluorescent agents are solid fine particles and are insoluble in solvents and resins, so when mixed with a binder resin and a solvent to form a coating film, light scattering occurs between the particles and a white color is exhibited. In many cases, it is inferior in colorlessness, transparency and invisibility under visible light. Therefore, if an inorganic colorless fluorescent agent is used, the ground color of the surface to be printed is concealed even under visible light, and the fluorescent agent printing for preventing counterfeiting is applied in the normal use state of the printed matter. It is easy to be found. For this reason, an organic colorless fluorescent agent is used in the present invention.
[0048]
The heat-meltable fluorescent ink layer is formed of a heat-meltable fluorescent ink in which a colorless fluorescent agent is dissolved or dispersed in a heat-transferable vehicle mainly composed of a heat-meltable binder resin. The colorless fluorescent agent in the inside is transferred to the printing surface together with the vehicle.
[0049]
As the hot-melt fluorescent ink, commercially available colorless fluorescent inks using an organic colorless fluorescent agent can be used effectively. For example, R-50 manufactured by Sinloi Co., Ltd. as the red color fluorescent ink, R-70 manufactured by the company as the green color fluorescent ink, and MR-30 manufactured by the company as the blue color fluorescent ink can be exemplified.
[0050]
Moreover, a commercially available organic colorless fluorescent agent can be dispersed or dissolved in a hot-melt binder resin or the like to prepare a hot-melt fluorescent ink. As commercially available colorless fluorescent agents, for example, LC-0001 manufactured by Nippon Kayaku Co., Ltd. as a red coloring fluorescent agent, EG-502 manufactured by Mitsui Chemicals, Inc. as a green coloring fluorescent agent, and Ubitech manufactured by Ciba Geigy Co., Ltd. as a blue coloring fluorescent agent. OB etc. can be illustrated.
[0051]
The heat-meltable binder resin and other compounding components that form the heat-transferable vehicle move to the printing surface together with the organic colorless fluorescent agent, and therefore are as transparent as possible so as not to impair the visibility of the image on the printing surface. It is preferable to use one, and particularly the hot-melt binder resin which is the main component of the vehicle is preferably substantially colorless and transparent under visible light.
[0052]
As the heat-meltable binder resin, one having high transparency and capable of being melted at the heating temperature of the thermal transfer process and fused to the printing surface is used. Specific examples include polyester resins, polystyrene resins, acrylic resins, polyurethane resins, acrylic urethane resins, vinyl chloride resins, vinyl acetate resins, vinyl chloride / vinyl acetate copolymer resins, polyamide resins, and silicone resins. Modified resins and mixtures of these resins can be used.
[0053]
You may mix | blend another component with a hot-melt fluorescent ink layer as needed. For example, by blending inorganic fine particles such as silica in the hot-melt fluorescent ink layer, the foil breakability during transfer can be improved.
[0054]
The blending ratio of the colorless fluorescent agent and the binder resin in the hot-melt fluorescent ink layer may be appropriately determined according to performance requirements. Since the emission intensity of the fluorescent color due to ultraviolet irradiation depends on the amount of the colorless fluorescent agent, the clearer color can be expressed as the blending ratio increases. However, since colorless fluorescent agents are expensive compared to general color materials, it is uneconomical to add more than necessary. Further, when the compatibility of the colorless fluorescent agent with the binder resin is not high, if the blending ratio of the colorless fluorescent agent is increased too much, there are problems such as precipitation of the colorless fluorescent agent in the hot-melt fluorescent ink layer. Taking these into consideration, the blending ratio of the colorless fluorescent agent in the heat-melting fluorescent ink is about 0.01 to 50% by weight, particularly about 0.1 to 20% by weight of the whole heat-melting fluorescent ink. In addition, the blending ratio of the binder resin is preferably about 50 to 99.99% by weight, particularly preferably about 80 to 99.9% by weight of the whole heat-meltable fluorescent ink.
[0055]
The thickness of the heat-meltable fluorescent ink layer is usually 0.2 to 5 μm, preferably 0.4 to 3 μm. When the thickness of the heat-meltable fluorescent ink layer is less than 0.2 μm, the uniformity of the layer thickness is poor and color unevenness is promoted. On the other hand, if the thickness of the heat-melting fluorescent ink layer exceeds 5 μm, the foil breakage at the time of transfer deteriorates, and there is a possibility that the heat-melting fluorescent ink layer is transferred to a region other than the desired region.
[0056]
In order to form a heat-meltable fluorescent ink layer on a base film, a colorless fluorescent agent, a binder resin, and other components as necessary, a single solvent such as toluene, methyl ethyl ketone, ethyl acetate, isopropanol or the like. A coating solution obtained by dissolving or dispersing in a mixed solvent can be formed by coating on a substrate film by a conventionally known method such as gravure coating, gravure reverse coating, roll coating, and drying. .
[0057]
In addition, when forming a heat-meltable fluorescent ink layer, a coating material containing a colorless fluorescent agent, a heat-meltable binder resin, and other components as necessary is not dissolved in a solvent, but heated. It may be formed by melting, coating on a base film by a conventionally known method such as hot melt coating, hot lacquer coating, gravure coating, gravure reverse coating, roll coating, and cooling.
[0058]
In the thermal transfer sheet used in the first method of the present invention, a colorant layer of yellow, magenta, cyan, black or the like can be provided in the surface order in addition to the heat-meltable fluorescent ink layer. As the colorant layer, a dye layer containing a sublimable dye or a hot-melt ink layer can be used.
[0059]
The dye layer is obtained by dissolving or dispersing a sublimable dye in a non-transferable vehicle containing a non-heat-meltable binder resin as a main component, and transferring only the sublimable dye in the dye layer to the printing surface. be able to. Since sublimation dyes are highly transparent, even when a visible image is formed using a sublimation dye after a fluorescent color image is first formed in the same image forming area on the printing surface, the fluorescent color of the visible image is increased. There is an advantage that the image is not hidden.
[0060]
As the sublimation dye, a sublimation dye used in a conventionally known sublimation thermal transfer type thermal transfer sheet can be used. Specifically, examples of yellow dyes include holon brilliant yellow 6GL, PTY-52, and Macrolex Yellow 6G. Examples of red dyes include MS Red G, Macrolex Red Violet R, Ceres Red 7B, Maron red HBSL, SK rubin SEGL, etc. can be exemplified, and examples of blue dyes include Kayaset Blue 714, Waxolin Blue AP-FW, Holon Brilliant Blue S-R, MS Blue 100, Daito Blue No. 1 etc. can be illustrated. In addition, a dye layer of an arbitrary hue such as black can be formed by combining the sublimable dyes of the respective hues.
[0061]
Further, as the non-heat-meltable binder resin of the dye layer and other compounding components, the same as the non-transferable vehicle of the sublimation type fluorescent dye layer described later can be used.
[0062]
The mixing ratio of the sublimable dye in the dye layer is usually about 5 to 90% by weight, preferably about 10 to 70% by weight of the whole dye layer. The thickness of the dye layer is usually 0.2 to 5 μm, preferably 0.4 to 2 μm.
[0063]
In order to form a dye layer on a base film, a sublimable dye, a binder resin, and other components as necessary are dissolved in a single solvent such as toluene, methyl ethyl ketone, ethyl acetate, isopropanol or a mixed solvent thereof. Alternatively, the coating liquid obtained by dispersing can be formed by coating on a substrate film by a conventionally known method such as gravure coating, gravure reverse coating, roll coating, and drying.
[0064]
The heat-meltable ink layer is formed of a heat-meltable colored ink composed of a colorant such as yellow, magenta, cyan, or black and a heat-meltable vehicle. The heat-meltable vehicle contains a heat-meltable binder as a main component and is necessary. Depending on the content, other components are contained. As the colorant, organic or inorganic pigments, dyes and the like can be used.
[0065]
Here, examples of the yellow colorant include PY-138, PY-139, and PY-151 in color index display. Examples of the magenta colorant include PR-177, PR-185, PR-208, and the like. Examples of the cyan colorant include PB-15, PB-15: 1, and PB-15: 6.
[0066]
In particular, when forming a hot-melt black ink layer, carbon black is preferably used as the black colorant. Carbon black has a sufficient color density among organic or inorganic pigments and dyes, and has good characteristics as a recording material such as no discoloration or fading due to light, heat, high temperature, etc. Clear characters and symbols can be printed with density.
[0067]
As the heat-meltable binder, it is preferable to use any one of the binder resins shown in the following 1) to 5) from the viewpoint of adhesion to the image receiving sheet and scratch resistance.
1) Acrylic resin,
2) Acrylic resin + chlorinated rubber,
3) Acrylic resin + vinyl chloride / vinyl acetate copolymer resin,
4) Acrylic resin + cellulose resin,
5) Vinyl chloride / vinyl acetate copolymer resin,
A wax or the like may be used instead of the binder resin, or a wax or the like may be added to the binder resin. Representative examples of the wax include microcrystalline wax, carnauba wax, paraffin wax and the like. In addition, various waxes such as Fischer-Tropsch wax, various low molecular weight polyethylene waxes, wood wax, beeswax, whale wax, ibota wax, wool wax, shellac wax, candelilla wax, petrolatum, partially modified wax, fatty acid ester, fatty acid amide, etc. It can also be used.
[0068]
In order to form a hot melt ink layer on a base film, as in the above hot melt fluorescent ink layer, a coating liquid obtained by dissolving or dispersing a necessary material in a solvent is applied on the base film. It can be formed by heating and drying, or by heating and melting a necessary material, coating the substrate film, and cooling. The thickness of the heat-meltable ink layer is determined from the relationship between the required color density and thermal sensitivity, and is usually preferably in the range of about 0.2 to 10 μm.
[0069]
In addition to the heat-melting fluorescent ink layer, the heat-transfer sheet used in the present invention can be provided with a transferable protective layer in the surface order. The transferable protective layer is transferred to the image forming area after the image formation on the printing surface is completed. The protective layer can be formed of various resins conventionally used as a protective layer for thermal transfer images. For example, polyester resin, polystyrene resin, acrylic resin, polyurethane resin, acrylic urethane resin, and these resins are modified with silicone. Resins, mixtures of these resins, ionizing radiation curable resins, ultraviolet blocking resins, and the like can be used.
[0070]
The protective layer containing the ionizing radiation curable resin is particularly excellent in plasticizer resistance and scratch resistance. As the ionizing radiation curable resin, known ones can be used. For example, a photopolymerization initiator is added to a radical polymerizable polymer or oligomer as necessary, and ionizing radiation such as an electron beam or ultraviolet rays is used. A composition capable of crosslinking polymerization can be used.
[0071]
Although the thickness of a protective layer is based also on the kind of resin for protective layer formation, it is usually preferable to set it as the range of about 0.5-10 micrometers.
[0072]
The protective layer may have a multilayer structure composed of a plurality of layers having different functions. For example, an adhesive layer may be formed on the outermost surface of the protective layer. The adhesive layer is formed of a resin having good adhesiveness when heated, such as an acrylic resin, a vinyl chloride resin, a vinyl acetate resin, a vinyl chloride / vinyl acetate copolymer resin, a polyester resin, or a polyamide resin. be able to. The thickness of the adhesive layer is usually in the range of about 0.1 to 5 μm.
[0073]
In order to form the transferable protective layer, a protective layer coating solution obtained by dissolving or dispersing the protective layer forming resin in a single solvent such as toluene, methyl ethyl ketone, ethyl acetate, isopropanol or a mixed solvent thereof, It can form by apply | coating on a base film or a peeling layer by conventionally well-known methods, such as a gravure coat, a gravure reverse coat, and a roll coat, and making it dry. When ionizing radiation curable resin is used, the coating layer is dried and then irradiated with ionizing radiation such as ultraviolet rays and electron beams to cure the coating layer.
[0074]
In the case where the transferable protective layer has a multilayer structure having an additional layer such as the above-mentioned adhesive layer, the protective layer coating solution containing the protective layer forming resin, the adhesive layer coating containing the thermal adhesive resin If the liquid and the coating liquid for forming the layer added as needed are prepared in advance, they are applied on the base film or the release layer in a predetermined order and dried. Good. An appropriate primer layer may be formed between the layers.
[0075]
The release layer is formed between the base film and these layers so that the heat-melting fluorescent ink layer, the heat-melting black ink layer, or the transferable protective layer can be easily transferred from the heat-transfer sheet to the image-receiving sheet. Provided. The hot-melt fluorescent ink layer, the hot-melt black ink layer, or the transferable protective layer is peeled off at the interface with the release layer and transferred to the image receiving sheet, and the release layer remains on the base film. This release layer is particularly effective when the base film is subjected to an easy adhesion treatment (adhesion improvement treatment) such as a corona discharge treatment.
[0076]
The release layer can be formed using, for example, a urethane resin, a polyvinyl acetal resin, or a mixture thereof. As in the case of the above-described hot-melt fluorescent ink layer and transferable protective layer, the release layer is prepared by dissolving or dispersing the release layer-forming resin in a solvent to form a coating solution. It can be formed by coating. The thickness is usually preferably about 0.1 to 5 μm.
[0077]
On the back side of the base film, that is, the side where the heat-meltable fluorescent ink layer is not provided, it is possible to prevent fusion with a heating element such as a thermal head, to improve paper feedability, In order to prevent blocking between the back side and the front side when the thermal transfer sheet of the invention is rolled up, it is desirable to provide a heat-resistant layer.
[0078]
Such a heat-resistant layer can be formed using, for example, a resin such as curable silicone oil, silicone resin, fluorine resin, acrylic resin, polyvinyl butyral resin, or a cured product thereof. In addition, for the purpose of controlling the slipperiness of the heat-resistant layer, a surfactant or various fillers may be added to the above materials. As in the case of the above-mentioned heat-meltable fluorescent ink layer and transferable protective layer, the heat-resistant layer is prepared by dissolving or dispersing the heat-resistant layer forming material with a solvent to form a coating solution, which is then applied onto the base film by a known method Can be formed.
[0079]
Next, a method for forming a fluorescent color image (forgery prevention mark) using the above-described thermal transfer sheet will be described. When the first method is performed by the thermal melt transfer method, one of a plurality of hot melt fluorescent ink layers provided on one or two or more thermal transfer sheets is faced to the image forming area on the printing surface. The heat-meltable fluorescent ink layer is heated according to the image information to be printed, and the heat-meltable fluorescent ink is applied to the image forming area on the printing surface by the dot matrix method and formed from now on. The heat-melting fluorescent ink layer is separated after the heat transfer so as not to overlap with other color dots, and then the heat-melting fluorescent ink layers of the same or other thermal transfer sheets are used in the same manner in the same manner. By transferring the heat-melting fluorescent ink to the same image forming region, an image emitting a plurality of fluorescent colors and / or a fluorescent color that is a mixture of them is formed when irradiated with ultraviolet rays.
[0080]
The first method is so-called area gradation, and as shown in FIG. 3, fluorescent inks of two or more colors are formed in dots by adjusting the transfer area of each color tone, and the dots of each color do not overlap. As described above, heat is transferred to the printing surface. According to this method, the fluorescent color of each transferred dot is microscopically monochromatic, but by making the transfer area unit of each dot sufficiently small, the area ratio of the dot group of each color to the human eye. Depending on the color, the additively mixed fluorescent color is visually recognized. When this method is applied to thermal melt transfer, a thermal head having a resolution of about 150 DPI or higher, which is mounted on a normal thermal transfer printer, is sufficient to recognize additively mixed fluorescent colors. It is. The area of the dot group can be adjusted by increasing or decreasing one or both of the number of dots and the area of one dot.
[0081]
The color tone of the colorless fluorescent agent is roughly divided into three colors of red, blue, and green, but according to the method of the present invention, not one of them, but two, three, or more Since the color tone is used to form an image that emits a plurality of fluorescent colors that cannot be distinguished by visible light, it is difficult to forge.
[0082]
According to the present invention, higher anti-counterfeiting properties can be imparted. By mixing the respective colors of red, blue and green with their intensities being adjusted appropriately, it is possible to create a fluorescent color having an arbitrary color tone including white light. Ordinary color materials absorb visible light and develop complementary colors. On the other hand, the colorless fluorescent agent absorbs ultraviolet rays and develops visible fluorescence, and the color mixture follows the law of additive color mixture. Therefore, when a colorless fluorescent agent that emits fluorescence having different color tones is used in combination, fluorescent colors having various tones including white can be arbitrarily created. Since the color tone of the fluorescent color obtained by color mixing can be changed steplessly, it is also possible to form a full-color fluorescent color image having gradation. By utilizing this property, in the present invention, an image emitting a plurality of fluorescent colors including mixed fluorescent colors can be formed using a plurality of colorless fluorescent agents, and a high level of forgery prevention can be imparted. In particular, it is preferable to form a full-color fluorescent color image having gradation by combining three primary colors of red, blue, and green, because a very high level of anti-counterfeiting can be imparted.
[0083]
(Second fluorescent image forming method)
In the second method, printing is performed by sublimation thermal transfer using two or more colors of organic fluorescent agents that are substantially colorless to visible light irradiation and emit fluorescence of different colors to ultraviolet light irradiation. In accordance with image information to be generated, an image that emits a plurality of fluorescent colors and / or a fluorescent color that is a mixture thereof when subjected to ultraviolet irradiation by transferring the organic fluorescent agent of each color to the image forming area on the printing surface. Form.
[0084]
When sublimation thermal transfer is performed using a highly sublimable organic colorless fluorescent agent, the same effects as those of the first method described above can be obtained even if overprinting is performed instead of the dot matrix method.
[0085]
That is, in the second method according to the present invention, the matrix of the dye layer remains on the thermal transfer sheet during thermal transfer, and only the colorless fluorescent agent sublimates and diffuses to the printing surface. It is excellent in invisibility, and it is difficult to find that it is printed using a fluorescent agent.
[0086]
Further, in the second method according to the present invention, only the colorless fluorescent agent is thermally diffused on the surface to be printed, and even if two or more colors are overprinted, an ink laminated structure is not formed. And lowering of the fluorescence coloring ability on the lower layer side due to the lamination of the ink layer is not caused.
[0087]
Furthermore, the amount of heat transfer of the colorless fluorescent agent can be arbitrarily adjusted by changing the heating energy, and when used in combination with colorless fluorescent agents that emit fluorescence of different colors, fluorescent colors of various colors including white Can be created arbitrarily. Moreover, the color tone of the fluorescent color obtained by the color mixture can be changed steplessly. Therefore, in the second method, it is possible to form a full-color fluorescent color image having gradation as in the first method.
[0088]
When the second method of the present invention is carried out by a thermal transfer method, two or more colors containing organic fluorescent agents that are substantially colorless to visible light irradiation and emit fluorescence of different colors to ultraviolet light irradiation. Two or more fluorescent colors can be printed using a combination of a plurality of thermal transfer sheets each having a fluorescent dye layer provided on a separate substrate film.
[0089]
In this case, one of the thermal transfer sheets is superposed with the fluorescent dye layer of the thermal transfer sheet facing the image forming area on the printing surface, and the fluorescent dye layer is heated according to the image information to be printed. The organic fluorescent agent is thermally diffused to the image forming area on the printing surface, and then the fluorescent dye layer is separated, and then the fluorescent dye layers of the other thermal transfer sheets are sequentially used in the same manner in the same image forming area. By thermally diffusing, it is possible to form an image that emits a plurality of fluorescent colors and / or a fluorescent color that is a mixture thereof when subjected to ultraviolet irradiation.
[0090]
Further, in the present invention, two or more fluorescent dye layers containing organic fluorescent agents that are substantially colorless to visible light irradiation and emit fluorescence of different colors to ultraviolet light irradiation are formed on the same substrate. It is also possible to print two or more fluorescent colors by using a thermal transfer sheet provided in a surface sequential manner on a film.
[0091]
In this case, one of the plurality of fluorescent dye layers provided on the thermal transfer sheet is overlapped with the image forming area on the surface to be printed, and the fluorescent dye layer is heated according to image information to be printed. The organic fluorescent agent is thermally diffused to the image forming area on the printing surface, and then the fluorescent dye layer is separated, and then the other fluorescent dye layers of the same thermal transfer sheet are sequentially used in the same manner to form the organic in the same image forming area. By thermally diffusing the fluorescent agent, it is possible to form an image that emits a plurality of fluorescent colors and / or a fluorescent color that is a mixture thereof when subjected to ultraviolet irradiation.
[0092]
As the sublimation thermal transfer sheet used in the second method, the heat-melting fluorescent ink layer of the thermal transfer sheet shown in FIGS. 1 and 2 as used in the first method contains a colorless fluorescent agent having high sublimation properties. The fluorescent dye layer can be used instead. However, the fluorescent dye layer does not need to be transferred to the entire substrate layer including the vehicle by heat, so it is not necessary to provide the fluorescent dye layer on the substrate film via the release layer, but rather between the non-transferable vehicle and the substrate film. In order to improve the adhesion of the substrate, it is preferable to perform an adhesion improving treatment such as corona discharge treatment of the base film or interposing a primer layer.
[0093]
The fluorescent dye layer is prepared by dissolving or dispersing a sublimable colorless fluorescent agent in a non-transferable vehicle and coating it on a substrate film. By heating this, only the organic fluorescent agent is transferred to the fluorescent color layer. The layer can be thermally diffused from the layer to the printing surface, and the non-transferable vehicle remains on the thermal transfer sheet.
[0094]
As an organic colorless fluorescent agent having high sublimation properties, those exemplified in the first method can be used. The non-transferable vehicle has a non-heat-meltable binder resin as a main component and is blended with other components as necessary.
[0095]
As the non-heat-meltable binder resin, a resin that does not melt at the heating temperature of the thermal transfer process is used. Specifically, cellulose resins such as ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, and cellulose acetate butyrate conventionally used as binder resins for sublimation dye layers; polyvinyl alcohol, polyacetic acid Examples include vinyl resins such as vinyl, polyvinyl butyral, polyvinyl acetal, polyvinyl pyrrolidone, poly (meth) acrylamide; polyurethane resins; polyamide resins; polyester resins; and mixtures of these resins. Cellulose-based, vinyl acetal-based, vinyl butyral-based, and polyester-based resins are preferable in terms of heat resistance, dye transferability, and the like.
[0096]
You may mix | blend another component with a sublimation type | mold fluorescent dye layer as needed. For example, a release agent such as silicone oil or polyethylene wax can be blended in order to adjust the friction between the fluorescent dye layer and the transfer object or prevent blocking in the wound state.
[0097]
If the mixing ratio of the colorless fluorescent agent and the binder resin in the fluorescent dye layer used in the second method is also appropriately determined according to performance requirements, as with the hot-melt fluorescent ink used in the first method. Good. The blending ratio of the colorless fluorescent agent is preferably about 0.1 to 80% by weight, particularly about 1 to 50% by weight of the entire fluorescent dye layer, and the blending ratio of the binder resin is based on the entire fluorescent dye layer. It is preferably about 20 to 99.9% by weight, particularly about 50 to 99% by weight. The blending ratio of the colorless fluorescent agent in the fluorescent dye layer is preferably larger than the blending ratio of the colorless fluorescent agent in the hot-melt fluorescent ink layer. The reason for this is that, in the case of sublimation thermal transfer, not all of the fluorescent agent in the transfer layer is transferred to the transfer target, and a certain amount remains in the transfer layer, so a clear fluorescent color This is because the fluorescent color content in the transfer layer needs to be increased in order to form an image.
[0098]
The thickness of the fluorescent dye layer is usually 0.2 to 5 μm, preferably 0.4 to 3 μm, like the hot-melt fluorescent ink layer.
[0099]
In order to form a fluorescent dye layer on a base film, a colorless fluorescent agent, a binder resin, and other components as necessary are added to a single solvent such as toluene, methyl ethyl ketone, ethyl acetate, isopropanol or a mixed solvent thereof. The coating liquid obtained by dissolving or dispersing can be formed by coating on a substrate film by a conventionally known method such as gravure coating, gravure reverse coating, roll coating, and drying.
[0100]
When the fluorescent image is formed by the second method, as described above, even if two or more colors are overprinted at the same place on the surface to be printed, a fluorescent full color image having excellent scratch resistance is obtained. Color tone can be easily controlled. Furthermore, in the second method, it is possible to perform fluorescent printing by the dot matrix method used in the first method, and even in this case, a fluorescent full-color image having excellent scratch resistance can be obtained and its color tone can be easily obtained. Can be controlled.
[0101]
【Example】
(Preparation of coating solution)
Prepare the heat-resistant layer coating solution, release layer coating solution, fluorescent color transfer layer coating solution, hot melt black ink layer coating solution, and protective layer coating solution of each composition shown below. did.
[0102]
  <Coating fluid for heat-resistant layer>
-Polyvinyl butyral resin (ESREC BX-1, manufactured by Sekisui Chemical Co., Ltd.): 3.6 parts by weight
Polyisocyanate (Bernock D750, manufactured by Dainippon Ink & Chemicals, Inc.): 8.6 parts by weight
・ Phosphate ester surfactant (Pricesurf A208S, manufactured by Daiichi Pharmaceutical Co., Ltd.): 2.8 parts by weight
-Talc (Microace P-3, manufactured by Nippon Talc Kogyo Co., Ltd.): 0.7 parts by weight
・ Methyl ethyl ketone: 32.0 parts by weight
-Toluene: 32.0 parts by weight
  <Release layer coating solution>
-Urethane resin (Crisbon 9004, manufactured by DIC): 20.0 parts by weight
Polyvinyl acetoacetal resin (KS-5, manufactured by Sekisui Chemical Co., Ltd.): 5.0 parts by weight
-Dimethylformamide: 80.0 parts by weight
・ Methyl ethyl ketone: 120.0 parts by weight
  <Coating liquid 1 for melt type fluorescent color transfer layer (red)>
Organic red fluorescent agent (R-50, manufactured by Sinloihi): total amount
  <Coating liquid 2 for melt type fluorescent color transfer layer (green)>
Organic green fluorescent agent (R-70, manufactured by Sinloihi): total amount
  <Coating liquid 3 for melt type fluorescent color transfer layer (blue)>
・ Organic blue fluorescent agent (MR-30, manufactured by Sinloihi): Total amount
  <Inorganic melt type fluorescent color transfer layer coating solution 1 (red)>
・ Inorganic red fluorescent agent (Y₂O_Three: Eu): 0.5 part by weight
-Vinyl chloride-vinyl acetate copolymer resin (# 1000 AKT, manufactured by Denki Kagaku Kogyo Co., Ltd.): 100.0 parts by weight
-Toluene: 150.0 parts by weight
・ Methyl ethyl ketone: 150.0 parts by weight
  <Inorganic melt type fluorescent color transfer layer coating solution 2 (green)>
Inorganic green fluorescent agent (ZnS: Cu, Al): 0.5 part by weight
-Vinyl chloride-vinyl acetate copolymer resin (# 1000 AKT, manufactured by Denki Kagaku Kogyo Co., Ltd.): 100.0 parts by weight
-Toluene: 150.0 parts by weight
・ Methyl ethyl ketone: 150.0 parts by weight
  <Inorganic melt type fluorescent color transfer layer coating solution 3 (blue)>
・ Inorganic blue fluorescent agent (Ca₂B_FiveO₉Cl: Eu^{2 +}): 0.5 part by weight
-Vinyl chloride-vinyl acetate copolymer resin (# 1000 AKT, manufactured by Denki Kagaku Kogyo Co., Ltd.): 100.0 parts by weight
-Toluene: 150.0 parts by weight
・ Methyl ethyl ketone: 150.0 parts by weight
  <Coating liquid for hot melt black ink layer>
-Vinyl chloride-vinyl acetate copolymer resin solution (# 1000 AKT, manufactured by Denki Kagaku Kogyo Co., Ltd.): 20.0 parts by weight
・ Carbon black: 10.0 parts by weight
・ Methyl ethyl ketone / toluene (weight ratio 1/1): 70.0 parts by weight
  <Coating liquid for protective layer>
Vinyl chloride-vinyl acetate copolymer resin solution (# 1000 AKT, manufactured by Denki Kagaku Kogyo Co., Ltd.): 100.0 parts by weight
-Toluene: 150.0 parts by weight
・ Methyl ethyl ketone: 150.0 parts by weight
  (Creation of base film for thermal transfer sheet)
  Using a gravure coater, apply the above heat-resistant layer coating liquid on one side of a 6 μm thick, easy-adhesion-treated polyethylene terephthalate film to a solid content of 0.8 g / m.²A heat-resistant layer was formed by coating and drying at a ratio of A thermal transfer sheet of each example described later was prepared using the base film thus prepared.
[0103]
(Example 1)
Using a gravure coater, the release layer coating liquid is 1 g / m in terms of solid content on the opposite side of the heat-resistant layer of the base film for thermal transfer sheet.²The release layer was formed by coating and drying at a ratio of. Next, the melt type fluorescent color transfer layer coating solution 1 (red) is 1 g / m in terms of solid content on the release layer.²Then, a fluorescent color transfer layer was formed by coating and drying at a rate of 1 to prepare a melt-type thermal transfer sheet 1.
[0104]
Further, instead of the melt type fluorescent color transfer layer coating solution 1, a melt type fluorescent color transfer layer coating solution 2 (green) and a melt type fluorescent color transfer layer coating solution 3 (blue) were used. Except for the above, a melt-type thermal transfer sheet 2 and a melt-type thermal transfer sheet 3 were respectively prepared.
[0105]
(Example 2)
Using a gravure coater, the release layer coating liquid is 1 g / m in terms of solid content on the opposite side of the heat-resistant layer of the base film for thermal transfer sheet.²The release layer was formed by coating and drying at a ratio of. Next, using a gravure printing machine, the melt type fluorescent color transfer layer coating solution 1 (red), the melt type fluorescent color transfer layer coating solution 2 (green), and the melt type fluorescent color transfer layer coating The working fluid 3 (blue) is 1 g / m in terms of solid content in the order of surface in the above order on the release layer.²Then, a fluorescent color transfer layer of each color was formed by coating and drying at a ratio of 5 to prepare a melt-type thermal transfer sheet 4. In addition, each fluorescent color transfer layer was formed with a gap of 1 cm with a length of 15 cm along the flow direction of the base film.
[0106]
(Example 3)
In Example 2, a melt-type thermal transfer sheet 5 was prepared in the same manner as in Example 2 except that the heat-melting black ink layer was formed in the surface order together with the three fluorescent color transfer layers. The hot-melt black ink layer is 0.7 g / m in terms of solid content at the next position of the fluorescent color transfer layer on the release layer using the gravure printing machine.²And a length of 15 cm along the flow direction of the base film, with a gap of 1 cm in the front and back.
[0107]
(Example 4)
In Example 2, a melt-type thermal transfer sheet 6 was prepared in the same manner as in Example 2, except that a transferable protective layer was formed in the surface order together with the three fluorescent color transfer layers. The transferable protective layer is 0.8 g / m in terms of solid content at the next position of the fluorescent color transfer layer on the release layer using the gravure printing machine.²And a length of 15 cm along the flow direction of the base film, with a gap of 1 cm in the front and back.
[0110]
(Comparative Example 1)
The same procedure as in Example 1 was performed except that the inorganic fluorescent color transfer layer coating solutions 1, 2, and 3 were used instead of the organic melt type fluorescent color transfer layer coating solutions 1, 2, and 3. The melt type thermal transfer sheets 1, 2 and 3 of the comparative examples were prepared, respectively.
[0111]
  (Evaluation method and results)
  Using the thermal transfer sheets prepared in the above Examples and Comparative Examples, printed materials were prepared and evaluated by any one of the following gradation methods. The thermal transfer image receiving sheet used was all L size paper A4 for Olympus Optical Co., Ltd. color printer P-400.
(1) Area gradation image 1
  A comparative print 2 having an area gradation image 1 was created using a photo retouching software “Photoshop” manufactured by Adobe. This is an area gradation image by a normal dither method, and color dots of R, G, and B colors have overlapping portions.
(2) Area gradation image 2
  Next, as described above, the printed matter 1, the printed matter 2, the printed matter 3, the printed matter 4, and the comparative printed matter having the area image 2 in which the color dots of R, G, and B are not overlapped. Object 1 was created.
[0112]
<Creation of print 1>
160 mJ / mm while the melt-type thermal transfer sheet 1 prepared in Example 1 and the thermal transfer image-receiving sheet are superposed and sandwiched and pressed between the thermal head and the platen roll.²After applying energy at a printing speed of 33.3 msec / line (feeding pitch: 6 line / mm), both were peeled off to form an image made of a colorless fluorescent agent on the thermal transfer image-receiving sheet.
[0113]
Next, printing is performed in the same manner except that the melt-type thermal transfer sheet 2 and the melt-type thermal transfer sheet 3 are used on the region where the image is formed using the melt-type thermal transfer sheet 1. The area gradation image 2 including the mixed color portion was formed. The resulting image made of a colorless fluorescent agent is almost colorless under visible light and difficult to visually recognize. When a commercially available black light (emission wavelength: 365 nm) is irradiated, the image-forming portion shows almost white light emission and is clearly visible. It was. Clearly different colors were obtained from the red, green and blue colors used.
[0114]
<Creation of print 2>
Using the melt-type thermal transfer sheet 4 obtained in Example 2, the fluorescent colors of red, green, and blue are sequentially transferred into the same area on the image receiving sheet under the same printing conditions as those for producing the print 1. Thus, the area gradation image 2 including the mixed color portion of each fluorescent color was formed.
[0115]
The obtained image made of a colorless fluorescent agent is almost colorless under visible light and difficult to visually recognize. When a commercially available black light (emission wavelength: 365 nm) is irradiated, the color tone of each colorless fluorescent agent used in the image forming portion is additively mixed. It showed full color emission and was clearly visible.
[0116]
<Creation of print 3>
Using the melt-type thermal transfer sheet 5 obtained in Example 3, the same printing conditions as those for producing the printed product 1 were received, and black, red, green, and blue fluorescent colors were received with the hot-melt black ink. The images were sequentially transferred into the same region on the sheet, and the letters composed of hot-melt black ink and the area gradation image 2 including the mixed color portions of the respective fluorescent colors were formed.
[0117]
The obtained printed matter was able to recognize only a black character image derived from the hot-melt black ink under visible light, and appeared to be no different from a normal thermal transfer recording image. However, when commercially available black light (emission wavelength: 365 nm) was irradiated, the color tone of each colorless fluorescent agent was additively mixed in the image forming portion of the fluorescent agent, showing full-color emission and clearly visible.
[0118]
<Creation of print 4>
Using the melt-type thermal transfer sheet 6 obtained in Example 4, the red, green, and blue fluorescent colors and the transferable protective layer are formed on the image receiving sheet under the same printing conditions as those for producing the print 1. The same area gradation image 2 including the mixed color portions of the respective fluorescent colors was formed, and the image was covered with a protective layer.
[0119]
The obtained image is almost colorless and difficult to visually recognize under visible light. However, when a commercially available black light (emission wavelength 365 nm) is irradiated, the color tone of each colorless fluorescent agent is additively mixed in the image forming portion, and full color emission is obtained. It was clearly visible.
[0122]
<Creation of comparative print 1>
The above-described area gradation image 2 made of an inorganic colorless fluorescent agent under the same printing conditions as those for producing the printed matter 1 except that the comparative melt-type thermal transfer sheets 1, 2 and 3 obtained in Comparative Example 1 were used. Formed. The obtained image was almost white under visible light, and it was clearly seen that some image was formed.
[0123]
When this image was irradiated with a commercially available black light (emission wavelength: 365 nm), the image forming portion showed blue light emission and was clearly visible.
[0124]
<Creation of comparative print 2>
An area gradation image 1 was formed using the comparative melt-type thermal transfer sheets 1, 2 and 3 under the same conditions as the comparative print 1. The obtained image was almost white under visible light, and it was clearly seen that some image was formed.
[0125]
When this image was irradiated with a commercially available black light (emission wavelength: 365 nm), the formation part of the fluorescent image was able to confirm each color of R, G, B and their additive color mixture, but the natural full color image is It was not obtained. When the fluorescence image is magnified and observed with a microscope, the two or three colors of the transfer layers of R, G, and B are overlapped with each other. I could n’t see it. In addition, it was confirmed that the overlapping portions of the respective colors easily peeled off when rubbed with fingers, and did not have scratch resistance that can withstand practical use.
[0126]
The outline of each test is summarized and shown in Table 1 below.
[0127]
[Table 1]

[0128]
【The invention's effect】
As described above, according to the fluorescent image forming method of the present invention, using an organic fluorescent agent that emits fluorescence having a color tone that is substantially colorless with respect to irradiation with visible light and different from that with irradiation with ultraviolet light, A fluorescent image having an arbitrary color tone that cannot be recognized by visible light can be formed. Further, the obtained fluorescent image has excellent scratch resistance and the fluorescent color tone can be easily controlled. Therefore, high anti-counterfeiting properties can be imparted to the printed matter.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of a thermal transfer sheet according to the present invention.
FIG. 2 is a schematic cross-sectional view showing another example of the thermal transfer sheet according to the present invention.
FIG. 3 is a diagram for explaining the principle of generating a mixed fluorescent color by area gradation in the present invention.
[Explanation of symbols]
1 ... Base film
2 ... Hot-melt fluorescent ink layer
3. Release layer
4 ... Heat-resistant layer
5 ... Hot-melt black ink layer
6 ... Transferable protective layer
7 ... Hot-melt ink layer

Claims (6)

Two or more heat-melting fluorescent ink layers each composed of a heat-melting fluorescent ink containing an organic fluorescent agent that is substantially colorless to visible light irradiation and emits fluorescence of different colors to ultraviolet light irradiation. Prepare multiple thermal transfer sheets provided on another base film,
Image information to be printed by superimposing one of the plurality of thermal transfer sheets so that the heat-meltable fluorescent ink layer of the heat-transfer sheet faces the image forming area on the printing surface. Heat transfer to the image forming area of the print surface by the dot matrix method and heat transfer so that it does not overlap with other color dots that have already been formed or will be formed in the future. The heat-melting fluorescent ink layer is separated, and then the heat-melting fluorescent ink layer of the other heat transfer sheet is sequentially used in the same manner to heat-transfer the heat-melting fluorescent ink to the same image forming region, thereby irradiating with ultraviolet rays. A fluorescent image forming method, comprising: forming an image that emits a plurality of fluorescent colors and / or a fluorescent color that is a mixture of them when received. Two or more heat-melting fluorescent ink layers composed of a heat-melting fluorescent ink containing an organic fluorescent agent that is substantially colorless to visible light irradiation and emits fluorescence of different colors to ultraviolet light irradiation are the same. Prepare a thermal transfer sheet that is provided surface-sequentially on the base film of
One of the heat-meltable fluorescent ink layers provided on the thermal transfer sheet is overlapped with the image forming area on the printing surface, and the heat-meltable fluorescent ink layer is heated in accordance with image information to be printed. The heat-fusible fluorescent ink is transferred to the image-forming area on the printing surface using the dot matrix method and so that it does not overlap with dots of other colors that have already been formed or will be formed. The fluorescent ink layer was separated, and then the other heat-meltable fluorescent ink layers of the same thermal transfer sheet were sequentially used in the same manner, and the heat-meltable fluorescent ink was transferred to the same image-forming region to receive ultraviolet irradiation. A method for forming a fluorescent image, characterized by forming an image that sometimes emits a plurality of fluorescent colors and / or fluorescent colors that are mixed colors thereof. The thermal transfer sheet is provided with a colorant transfer layer containing a colorant visible by irradiation with visible light together with the heat-meltable fluorescent ink layer on the same substrate film in a surface sequential manner,
By superposing the colorant transfer layer of the thermal transfer sheet so as to face the image forming area of the printing surface, by heating the colorant transfer layer according to image information to be printed,
The fluorescent image forming method according to claim 2 , wherein an image that can be recognized by irradiation with visible light is formed together with the image that emits a fluorescent color by irradiation with ultraviolet rays. The thermal transfer sheet is provided with a heat-melting black ink layer composed of a heat-melting black ink, in addition to the heat-melting fluorescent ink layer, in the surface sequence on the same substrate film,
The heat-melting black ink layer of the thermal transfer sheet is superimposed on the image forming area of the printing surface so that the heat-melting black ink layer is heated according to the image information to be printed to transfer the heat-melting black ink to heat. By letting
4. The fluorescent image forming method according to claim 2 , wherein a black image that can be recognized by irradiation with visible light is formed together with the image that emits fluorescent color by irradiation with ultraviolet rays. The thermal transfer sheet, in addition to the hot-melt fluorescent ink layer, further provided a transferable protective layer on the same substrate film in the surface order,
The transferable protective layer of the thermal transfer sheet is overlapped with the image forming area on the printing surface, and the image forming area is covered by heat transfer of the transferable protective layer. The fluorescent image forming method according to claim 2 . A printed matter formed by the fluorescent image forming method according to claim 1 .

Images