JP2007076371A - Thermal recording medium and texture hue adjusting method for thermal coloring layer of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent decrease of printing quality of a thermal recording medium by decreasing a difference in a hue of texture near the border of mutually adjoining thermal coloring layers which develop color in different hues. <P>SOLUTION: In the thermal recording medium 1 wherein a plurality of the thermal coloring layers 4 coloring in different hues by application of at least thermal energy to a surface of a substrate 2 are formed, in order to decrease a difference in density of the hue between the thermal coloring layer 4 having a high hue density before thermally coloring and the thermal coloring layer 4 having a low hue density, an adjusting agent in texture hue is added to the thermal coloring layer 4 of at least low hue density to decrease a difference in the texture hue of the mutually adjoining thermal coloring layers 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thermosensitive recording medium that develops colors in different hues in different areas, and in particular, an adjustment method in which the density of the background is slightly different before applying the thermal energy of the thermosensitive coloring layer that develops colors in different hues, and an adjusted thermosensitivity The present invention relates to a recording medium.

  2. Description of the Related Art Conventionally, a multicolor thermal recording medium that realizes a plurality of forms with one thermal recording medium is known. As this multicolor thermosensitive recording medium, a recording medium is known in which at least two thermosensitive coloring layers that develop different hues at different coloring temperatures are laminated on a substrate such as paper. (For example, see Patent Document 1)

  When printing is performed by heating such a multicolor thermal recording medium with a thermal head, images of different hues can be obtained by changing the heating temperature. For example, when it is heated at a low temperature, it develops blue, and when it is heated at a high temperature, it develops black. In order to print such a multicolor thermal recording medium, it is necessary to control the temperature of the thermal head. In addition, when printing is performed with a thermal head controlled to a high temperature, the peripheral portion of the printing dot is at a temperature controlled to a low temperature, so that it appears that the colors are mixed.

  In order to solve such problems, two or more heat-sensitive color developing layers that develop colors in different hues are partially formed on a substrate, and only the pixels that develop the color are selectively heated to obtain a multicolor image. A method has been proposed (see, for example, Patent Documents 2 and 3).

JP 57-178791 A JP 60-208283 A JP 2000-301835 A

  When a medium such as roll paper is used as the recording medium, a stripe-shaped thermal recording layer pattern can be continuously formed in the length direction by a printing method. The size and pattern in the width direction of the recording layer of the thermosensitive recording medium can be changed relatively easily. However, in a thermal recording medium in which a thermal coloring layer is partially formed by a printing method, as described above, when continuous stripe-shaped thermal coloring layers having different colors are adjacent to each other in a plane, for example, black coloring occurs. Since the hue (background) before coloring of the thermosensitive coloring layer and the thermosensitive coloring layer that develops red color is slightly different, a phenomenon occurs in which the hue difference near the boundary adjacent to each other becomes noticeable.

  For this reason, when printing is actually performed on a product label or the like formed from this heat-sensitive recording medium, the print quality of the product label or the like is deteriorated due to the difference in the hue of the background of the boundary portion between the heat-sensitive coloring layers adjacent to each other. It is the cause that causes.

  In the present application, as described above, the object is to reduce the difference in the background near the boundary between adjacent heat-sensitive color-developing layers that develop colors with different hues, and to prevent the deterioration of the print quality of the heat-sensitive recording medium. .

  In addition, the inventor of the present application uses, as a thermal ink used for the production of a thermal recording medium, in water, as an electron-accepting compound, for example, a developer, an electron-donating compound, for example, a pigment such as a leuco dye or a sensitizer. A patent application (Japanese Patent Application No. 2003-099356) relating to a thermal recording medium using water-dispersed thermal ink in which components are dispersed using a dispersant such as a surfactant has been filed.

  In this application, when the water-dispersed thermal ink is applied using a coating device such as a blade coater, air knife coater, roll coater, bar coater, gravure coater, and lip coater, the heat-sensitive ink coated with the water-dispersed thermal ink is applied. When a recording medium is put in an oven or the like and heated to dry, a structure for preventing the generation of a so-called “swimming” stripe pattern is disclosed.

  However, in order to improve the leveling of the coated water-dispersed thermal ink, when adding a surfactant or alcohol used to lower the surface tension, the added material makes the water-dispersed thermal ink Is slightly colored, and as described above, the background density difference between adjacent heat-sensitive coloring layers is particularly likely to occur.

  In a thermal recording medium in which a plurality of thermal coloring layers that are colored with different hues are applied to the surface of the substrate by applying thermal energy, the hue of the background of the thermal coloring layer among the thermal coloring layers adjacent to each other. In order to reduce the difference in density between the heat-sensitive color developing layer and the heat-sensitive color developing layer where the density of the background color is light, the background density adjusting agent is added to at least the heat-sensitive color developing layer where the color density of the background is light, Provided is a method for reducing a background density difference between the heat-sensitive coloring layers adjacent to each other.

  Further, in the heat-sensitive recording medium in which a plurality of heat-sensitive color layers that are colored in different hues by application of heat energy are formed adjacent to each other on the surface of the substrate, at least of the heat-sensitive color layers among the heat-sensitive color layers adjacent to each other. In order to reduce the difference in density between the heat-sensitive color-developing layer and the heat-sensitive color-developing layer where the hue density is light and the color of the background color is light, at least a background color adjusting agent is added to the heat-sensitive color-developing layer where the density of the background color is light. A thermal recording medium is provided.

  According to the present invention, it is possible to reduce the difference in the hue of the background of the thermosensitive coloring layers that are adjacent to each other and develop colors with different colors, and it is possible to provide a thermosensitive recording medium with good print quality.

An embodiment of the present invention will be described with reference to FIGS.
1 is a plan view showing a thermal recording medium, FIG. 2 is a sectional view of FIG. 1, and FIG. 3 is a plan view showing a printing state.

  The thermosensitive recording medium 1 includes a base material 2, an ink receiving layer 3 formed on the surface of the base material 2, thermosensitive coloring layers 4a, 4b that are colored in different colors formed on the ink receiving layer 3, and 4c is formed.

  The heat-sensitive color developing layers 4a, 4b and 4c are integrally formed by penetrating the ink receiving layer 3 as shown in FIG. When the printing method is used, so-called “swimming” is likely to occur. Therefore, it is possible to suppress the occurrence by forming the ink receiving layer 3 integrally. The formation of the thermosensitive coloring layers 4a, 4b and 4c integrally with the ink receiving layer 3 means that the thermosensitive coloring layers 4a, 4b and 4c are completely formed on the ink receiving layer 3 as long as the print quality is not affected by swimming. It does not penetrate and may protrude to the top.

  For example, as shown in FIG. 3, the heat-sensitive recording medium 1 can be a price card or the like by printing a measurement label or the like added to a product, or heat-sensitive coloring layers 4a, 4b and 4c as shown in FIGS. It can be used as a POP. The thermal coloring layer 4a can be visually printed by printing the advertisement product, emphasized characters such as SALE, etc., and the thermal coloring layer 4b by printing the product description and barcode, and the price of the special coloring etc. in different colors. It can be used for POP that can be publicized to customers.

  Here, as shown in the present embodiment, when the layers (4a, 4b, and 4c) of the thermosensitive coloring layer 4 that develop colors with different hues are adjacent to each other in plane, the hue of the background before coloring is slightly different. And its boundary line is conspicuous, causing a problem visually. For example, when the color difference (ΔE) between 4a and 4b of these adjacent heat-sensitive color developing layers 4 is 1 or more, the color difference at the boundary between each other is remarkably noticeable, preferably 0.5. If it is below, the color difference at the border will be inconspicuous. Here, “adjacent” of the thermosensitive coloring layer 4 means that the density (white bean) of the background portions of the layers 4a, 4b, and 4c of the thermosensitive coloring layer 4 having different hues before application of thermal energy is visually recognized. It includes a state of approaching a position that can be distinguished.

  The color difference in the thermal recording layers (4a, 4b and 4c) adjacent to each other of the thermal recording medium 1 used in the embodiment of the present invention is shown in the following table [Table 1] and graph [FIG. 7].

A table showing the relationship of color differences between the printing plate and each color:

  As the cell depth of the printing plate increases, the color difference between the thermosensitive coloring layers 4a, 4b and 4c increases. This is because the thickness of the thermosensitive coloring layers 4a, 4b and 4c having slightly different hues increases as the cell depth increases, so that the color difference increases. It is necessary that the color difference between each color is 0.6 or less, which is considered to be inconspicuous to human eyes (a horizontal broken line N in FIG. 7 indicates a color difference limit at a good boundary). Further, the cell depth of the printing plate needs to be 38 μm or less, which is a problem when the density is not sufficient (the two-dotted broken line M in FIG. 7 is a good boundary printing depth limit). Showing). In the embodiment of the present invention, an experiment was conducted on a method for making the boundary portion inconspicuous even when the cell depth of a 150-line printing plate is 40 μm.

In order to correct the background color difference of each of the heat-sensitive color developing layers (4a, 4b, and 4c) that develop colors in different colors of the heat-sensitive color developing layer 4, the heat-sensitive color developing layer 4 having a light background color (for example, the heat sensitive color developing layer 4c that colors red). ) Is added with a predetermined amount of a colorant so that the hue of the background portion is dark (for example, 4b that develops black). Here, this colorant is referred to as a “background hue adjusting agent”.
Of course, the predetermined amount of the background hue adjusting agent depends on the kind thereof, but in practice, the optimum addition amount is experimentally determined by cut and try. Hereinafter, specific examples performed in the embodiment of the present invention will be described.

  A water dispersion containing an electron donating compound (crystal violet lactone: manufactured by Yamamoto Kasei Co., Ltd.) that develops a blue color when heat energy is applied on a substrate 2 provided with an ink receiving layer 3 containing an electron accepting compound. A blue thermosensitive coloring layer 4a formed by gravure printing; a black thermosensitive coloring layer 4b formed by gravure printing with a water-dispersed ink containing an electron donating compound (ODB-2: manufactured by Yamamoto Kasei Co., Ltd.) that develops black color; A red thermosensitive coloring layer 4 c formed by gravure printing of a water-dispersed ink containing an electron donating compound (Vermilion-DCF: manufactured by Hodogaya Chemical Industry Co., Ltd.) that develops a red color is formed integrally with the ink receiving layer 3. Furthermore, the protective layer 6 is provided so that it can print with a thermal head.

When the electron-donating compound is different, the color of the water-dispersed ink is slightly different, and the thermosensitive coloring layers 4a, 4b and 4c of each hue are printed by a gravure printing method with a dry weight of about 5 g / m ² (the solid content of the water-dispersed ink is If it is about 30%, a water-dispersed ink of about 15 g / m ² is printed.) The hues of the background portions of the heat-sensitive color layers 4a, 4b, and 4c obtained by drying are slightly different.

  When the above-described electron donating compound (the target hue is controlled by changing this kind) is used for the thermosensitive coloring layers having different hues, the adjacent black thermosensitive coloring layer 4b is like normal thermal paper. If it is applied over the entire surface, it does not feel dark, but since the red thermosensitive coloring layer 4c is particularly white compared to the other coloring layers, the boundary portion stands out conspicuously. On the other hand, although the blue thermosensitive coloring layer 4a is slightly colored in blue, since it is visually close to black, the boundary with the thermosensitive coloring layer 4b is not clear and hardly noticeable, but the thermosensitive coloring layer 4c that develops red color. Is adjacent, it becomes a problem because the boundary is conspicuous.

  Therefore, in order to make the boundary line between the red thermosensitive coloring layer 4c and the other thermosensitive coloring layers 4a and 4b inconspicuous, a black aqueous dye is used as a background hue adjusting agent in an aqueous dispersion ink containing an electron donating compound that develops a red color. Containing. Since the hue of the background of the heat-sensitive color developing layer 4b that develops black color is extremely thin black, adding a slight amount of black aqueous dye to the red heat-sensitive color developing layer 4c with a white background may make the boundary portion inconspicuous. it can.

  DUASYN D. as a background hue adjusting agent on the base material 2 provided with the ink receiving layer 3 containing an electron accepting compound. About 0.12% of a black aqueous dye aqueous solution of BLACK HEF-SF liq (manufactured by Clariant) is added to the solid content of the water-dispersed ink of an electron donating compound that develops a red color.

  Print and dry red water-dispersed ink to which black aqueous dye aqueous solution has been added on a printing plate (150-line cell depth 40 μm corrosive plate) of a simple gravure printing machine (manufactured by Matsuo Sangyo Co., Ltd .: K printing proofer). The thermosensitive coloring layer 4c is formed. Similarly, in the adjacent position, a water-dispersed ink containing an electron donating property that develops color in black is printed and dried with a printing plate (corrosion plate having a 150-line cell depth of 40 μm) to form a black thermosensitive coloring layer 4b. Similarly, a blue thermosensitive coloring layer 4a is formed to form a stripe-shaped thermosensitive coloring layer as shown in FIG.

  Thermosensitive coloring layer 4C formed by water-dispersed ink to which 0.12% of a black aqueous dye aqueous solution is added as a background hue adjusting agent (Here, the thermosensitive coloring layer to which the background hue adjusting agent is added is referred to as “thermal coloring layer 4C. Is distinguished from “thermosensitive color developing layer 4c” to which no background hue adjusting agent is added.) Is improved from 0.37 when the color difference from black thermosensitive color developing layer 4b is not added to 0.24. The color difference from the blue thermosensitive coloring layer 4a was improved from 0.45 when the color difference was not added to 0.28.

  Here, when the color density of the thermosensitive coloring layer 4 of the thermosensitive recording medium 1 is made higher, it is necessary to increase the transfer amount of the water-dispersed ink from the printing plate. For example, when a 150-line cell depth 40 μm corroded plate is used to form each of the heat-sensitive color layers 4a, 4b and 4c and the heat-sensitive color layer 4C, the color difference between the black heat-sensitive color layer 4b is 0.5 to 0.34. It was improved from 0.65 to 0.35.

  It can be seen from the numerical value of the color difference that when the 150-line cell depth is 40 μm, the color difference can be reduced from a numerical value of about 0.6 or more where the boundary portion is conspicuous to a problem level.

  As the background hue adjusting agent, the amount of the black aqueous dye aqueous solution added depends on the background concentration of the heat-sensitive color forming layer 4b provided partially, the material of the electron donating compound used, the concentration of the black aqueous dye aqueous solution, and the coloring ability. Need to change. When the visibility of other colors and the boundary becomes a problem, it is effective to add a colorant of another color.

  Specifically, the hue Lab space of each thermosensitive coloring layer 4a, 4b, and 4c was measured with X-Rite 938, and the color difference was calculated by a predetermined mathematical formula (the following [Equation 1]).

Color difference between two points (between A and B) ΔE:

  As a result, the background hue adjusting agent to be added is grasped, and the added amount is actually tested by printing, and the added amount of the background hue adjusting agent is experimentally obtained so that the color difference is 0.6 or less.

  Examples of the substrate 2 include paper, plastic films such as polyethylene terephthalate, and metal foils, but are not limited thereto as long as they do not interfere with the object of the present invention.

When paper is used as the base material 2, when the thermosensitive coloring layer 4 is printed using a normal gravure printing machine, wrinkles are likely to occur in the base material 2 because water-dispersed thermal ink is used. As the thickness of the base material 2 which does not generate wrinkles even if it is used in a normal gravure printing machine, a basis weight of 90 g / m ² or more is necessary, and more preferably, paper having a weight of 100 g / m ² or more is used.

  The ink receiving layer 3 includes a pigment as a main component and a pigment and a binder resin in order to easily absorb the water-based dispersed ink in order to prevent the thermal coloring layer 4 formed by a printing method from swimming. . Examples of the pigment include inorganic pigments such as clay, calcined clay, calcium carbonate, titanium oxide, aluminum oxide, aluminum hydroxide, and silica, and beads such as styrene, styrene / acrylic, and acrylic, hollow resin Organic pigments such as can be used. Furthermore, a porous pigment which is an aggregate in which primary particles are aggregated is preferable. For example, calcium carbonate, synthetic silica, or the like can be used. As the binder resin used for the ink receiving layer 3, a water-soluble polymer or a water-soluble polymer emulsion can be used. Examples of the water-soluble polymer include polyvinyl alcohol, starch and derivatives thereof, cellulose derivatives, gelatin, casein, styrene / maleic anhydride copolymer salts, styrene / acrylic acid copolymer salts, and the like. Examples of the water-soluble polymer emulsion include latex such as styrene / butadiene copolymer, emulsion such as vinyl acetate resin, styrene / acrylic acid ester copolymer, polyurethane resin, and the like. If necessary, lubricants such as zinc stearate and wax, and additives such as hindered phenols may be added to the ink receiving layer 3. Further, when the ink forming the thermosensitive coloring layer 4 contains an electron donating compound and does not contain an electron accepting compound, it is necessary to add the electron accepting compound to the ink receiving layer 3.

The fabricated coating liquid coating machine, 1 to 50 g / ^{m 2} as the weight after drying, preferably 3 to 10 g / ^{m 2} was applied to form an ink-receiving layer 3. As the coating machine, a coating apparatus such as an air knife coater, a bar coater, a roll coater, a blade coater, or a gravure coater can be used. Moreover, you may perform a smoothing process by a calendar etc. as needed.

  As described above, forming the thermosensitive coloring layers 4a, 4b, and 4c integrally with the ink receiving layer 3 in the ink receiving layer 3 reduces "swimming". The thermosensitive coloring layers 4a, 4b and 4c have different coloring hues and contain at least an electron donating compound and a binder resin.

  Examples of the electron-accepting compound include developers, and specifically include phenols, phenol metal salts, carboxylic acid metal salts, sulfonic acid, sulfonate, phosphoric acid, metal phosphate, acidic phosphoric acid. Oxides such as esters, acidic phosphoric acid ester metal salts, phosphorous acids, and phosphorous acid metal salts can be used. Of course, you may mix and use instead of one kind of material.

  Examples of the electron donating compound include leuco dyes, and specifically, <Black> PSD-150, PSD-184, PSD-300, PSD-802, PSD-290 (above, Nippon Soda Co., Ltd.) CP-101, BLACK-15, ODB, ODB2 (above, manufactured by Yamamoto Kasei Co., Ltd.), BLACK-100, S-205, BLACK-305, BLACK-500 (above, manufactured by Yamada Chemical Co., Ltd.), TH-107 (above , Hodogaya Chemical Co., Ltd.), <Blue> CVL, BLUE-63, BLUE-502 (above, Yamamoto Kasei Co., Ltd.), BLUE-220 (above, Yamada Chemical Co., Ltd.), BLUE-3 (above, Hoo Manufactured by Tsuchiya Chemical Industry Co., Ltd.), <red> PSD-HR, PSD-P, PSD-O (manufactured by Nippon Soda Co., Ltd.), Red-3, Red-40 (manufactured by Yamamoto Kasei Co., Ltd.), Red-50 , Red-520 (manufactured by Yamada Chemical Co.), Vermilion-DCF, Red-DCF (or, Hodogaya Chemical Co., Ltd.) can be used a material such as. Moreover, you may mix and use not one type of material.

  Other colors include <green> PSD-3G (Nippon Soda Co., Ltd.), ATP (Yamada Chemical Co., Ltd.), Green-DCF (Hodogaya Chemical Co., Ltd.), <Yellow> Color Yellow-17 (manufactured by Yamamoto Kasei Co., Ltd.) <Orange-based> PSD-O (manufactured by Nippon Soda Co., Ltd.), Orange 100 (manufactured by Yamada Chemical Co., Ltd.) and the like, and dyes other than these colors can also be used.

  As the binder resin, water-soluble resins such as starches, celluloses, and polyvinyl alcohol, and resins such as resin latexes such as polyvinyl acetate, polyurethane, and polyacrylate can be used. Of course, you may mix and use instead of one kind of material.

  Other sensitizers such as waxes, naphthol derivatives, biphenyl derivatives, polyether derivatives, and carbonic acid diester derivatives, head wear inhibitors such as zinc stearate, stearamide, and calcium carbonate, and anti-sticking agents as necessary. Can be used.

  A protective layer (not shown) was formed using OCA-5 manufactured by Nippon Kayaku Co., Ltd. with a bar coater so that the dry weight was 2 g / m 2.

  As a method for forming a water-dispersed ink for forming the heat-sensitive coloring layers 4a, 4b, and 4c, a gravure printing method in which a leuco dye (electron-donating compound), a binder resin, a sensitizer, and the like are dispersed and mixed in water to form an aqueous dispersion. The surface tension is reduced to about 30 mN / m or less by adding a surfactant so that it can be formed. Further, alcohols may be added.

  In addition, a method for forming a water-dispersed ink for forming the thermosensitive coloring layer 4c to which a background hue adjusting agent is added is a water dispersion in which a leuco dye (electron-donating compound), a binder resin, a sensitizer, and the like are dispersed and mixed in water. A surface active agent is added so that it can be formed by gravure printing, and the surface tension is lowered to about 30 mN / m or less. For example, a necessary amount of a black water-soluble dye solution is mixed as a background hue adjusting agent. Further, alcohols may be added.

  Further, these water-dispersed inks may be used in combination with various additives such as an antifoaming agent, an ultraviolet absorber and a preservative.

  The background hue adjusting agent to be added needs to be selected according to the electron donating compound to be used, and the addition amount is appropriately changed depending on the electron donating compound to be used and the coloring ability of the dye. As a guideline, it is desirable that the addition amount is to reduce the color difference to 0.6 or less, and it is about 0.01% to 0.1% of the solid content of the thermosensitive coloring layer 4 with the solid content of the dye used. It is.

  As the colorant to be used, an aqueous dye solution of Kayafect series manufactured by Nippon Kayaku Co., Ltd., a powder product thereof, an aqueous dye solution of Duasyn SF Liquid series manufactured by Client, or the like can be used.

  Sensitizers differ in their ideal materials depending on the electron-accepting compound used and the electron-donating compound used in the thermosensitive color-developing layer 4, but improve the sensitivity of color development due to the combination of the electron-accepting compound and the electron-donating compound. It is a material to make. For example, HS-3520 manufactured by Dainippon Ink & Chemicals, Inc. can be used.

  The specific configuration of the thermal recording medium 1 of the present invention will be described below with reference to examples, but the present invention is not limited to these. In the examples, “parts” represents parts by weight.

<Example 1>
◎ Formation and baking of ink-receiving layer Kaolin (pigment of ink-receiving layer 3) 100 parts (Shiraishi Calcium Co., Ltd., trade name: Kao Cal)
-Hydrophilic silica (pigment of ink receiving layer 3) 11 parts (manufactured by Tosoh Silica, trade name: Nipsil E-220A)
Dispersant: 1 part of polyacrylic acid soda, 400 parts of water The above composition was dispersed with a homogenizer to prepare a pigment dispersion of hydrophilic silica. And in this pigment dispersion,
・ 55 parts of styrene / butadiene copolymer latex (manufactured by JSR, 48% SBR dispersion)
・ 37 parts of phosphate esterified starch (manufactured by Nippon Shokuhin Kako Co., Ltd., trade name: MS-4600, 20% aqueous solution)
Add and disperse and mix with a homogenizer.
・ Developer dispersion (solid content: 40%) 75 parts (D-8, manufactured by Chukyo Yushi Co., Ltd., trade name: F-647)
Sensitizer dispersion (solid content 30%) 100 parts (HS-3520, manufactured by Dainippon Ink & Chemicals, Inc.)
・ Lubricant dispersion (solid content 30%) 32 parts (zinc stearate, manufactured by Chukyo Yushi Co., Ltd., trade name: Hydrin Z-7-30)
-Recrystallization inhibitor dispersion (solid content 35%) 20 parts (DH43, manufactured by Chukyo Yushi Co., Ltd., trade name: Hydrin F-165)
Was added and dispersed with a homogenizer to obtain a coating solution.

This coating solution was applied to a substrate (quality paper) 2 having a weight of 90 g / m ² with a micro gravure coater at a conveyance speed of 50 m / min, a drying temperature of 100 ° C., and a weight after drying of 8 g / m ^2. The ink receiving layer 3 was formed on the base material 2 by drying.

◎ Formation of thermosensitive coloring layers 4a and 4b, leuco dye dispersion (solid content 30%) 50 parts Blue (CVL, manufactured by Yamamoto Kasei Co., Ltd.)
Black (ODB-2, manufactured by Yamamoto Kasei Co., Ltd.)

The leuco dye dispersion was dispersed in water so that 5% Goseilan L-3266 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was used as a dispersant, and the leuco dye was dispersed with a sand mill so that the average particle size was 0.8 μm.
・ 53 parts of PVA 10% solution (PVA110 manufactured by Kuraray Co., Ltd.)
-Surfactant (solid content 10%) 33 parts (Adeka Coal EC4500, manufactured by Asahi Denka Co., Ltd.)
・ 25 parts of water

  The above-described blue and black leuco dye dispersions are mixed with the above-described PVA 10% solution, a surfactant, and water to produce different water-dispersed inks having a colored hue of blue and black.

  The viscosity of each water-dispersed ink was adjusted to 30 to 40 cps (manufactured by Tokyo Keiki Co., Ltd., measured with an E-type viscometer), and the surface tension was adjusted to about 30 mN / m (manufactured by Cruz, K12-Mk5 surface tensiometer) or less. . In particular, in printing by an intaglio, if the surface tension of the ink is large, the ink does not enter the printing plate, so it is necessary to reduce the surface tension of the ink with a surfactant or the like.

  These water-dispersed inks are printed in a stripe pattern on the ink receiving layer 3 in order by a simple gravure printing machine (Matsuo Sangyo Co., Ltd .: K printing proofer) (gravure printing plate 150 lines, corrosive plate having a cell depth of 40 μm). The heat-sensitive coloring layers 4a and 4b of the heat-sensitive recording medium 1 were produced.

Formation of “Thermosensitive Coloring Layer 4C” to which Background Color Adjusting Agent is Added Here, it is distinguished from “Thermosensitive Coloring Layer 4c” to which no background color adjusting agent is added.
It is produced in the same manner as the thermosensitive coloring layers 4a and 4b, and finally a black dye aqueous solution is mixed as a background hue adjusting agent.
・ Leuco dye dispersion (solid content 30%) 50 parts red (Vermilion-DCF, manufactured by Hodogaya Chemical Co., Ltd.)

The leuco dye dispersion was dispersed in water so that 5% Goseilan L-3266 (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was used as a dispersant, and the leuco dye was dispersed with a sand mill so that the average particle size was 0.8 μm.
・ 53 parts of PVA 10% solution (PVA110 manufactured by Kuraray Co., Ltd.)
-Surfactant (solid content 10%) 33 parts (Adeka Coal EC4500, manufactured by Asahi Denka Co., Ltd.)
・ 25 parts of water

  The above-described red leuco dye dispersion liquid is mixed with the above-described PVA 10% solution, a surfactant, and water to prepare a water-dispersed ink in which the color hue is red.

Further, as a background hue adjusting agent: DUASYN D.D. BLACK HEF-SF liq (manufactured by Clariant) 0.018 parts by weight was added, mixed with stirring, printed on the ink receiving layer 3 in the same manner as the heat-sensitive color developing layers 4a and 4b, and a background hue adjusting agent was added. A thermosensitive coloring layer 4C is obtained.
Separately from this, for comparison, the thermal coloring layer 4c was printed on the ink receiving layer 3 in the same manner as the thermal coloring layers 4a, 4b and 4C.

The weight after drying the protective layer (OCA-5: manufactured by Nippon Kayaku Co., Ltd.) on the thermal recording medium 1 on which the thermal coloring layer 4c and the thermal coloring layer 4C added with the background hue adjusting agent thus obtained were printed. It apply | coated using the bar coater so that it might become 1-2 g / m < ² >. Furthermore, the striped thermosensitive recording medium 1 was obtained by calendering.

In evaluation / evaluation, the visibility of the thermosensitive coloring layers 4a and 4b and the thermosensitive coloring layer 4C to which the background hue adjusting agent was added was evaluated.
-Hue between each color was measured with X-Rite 938, and the color difference was calculated.
B-419 (barcode printer manufactured by TOSHIBA TEC Co., Ltd.), a test pattern was printed at a set density +3, and the density and hue of the thermosensitive coloring layer 4C to which the background hue adjusting agent was added were measured (Comparative Example 1 or Comparison) (To confirm the color development and color difference when the colorant of Example 2 is not added). The density was measured with a Macbeth densitometer RD-19, and the hue was measured with an X-Rite 938.

◎ Result / Visibility: No problem because the border is inconspicuous. Color difference of the background: (See [Table 2] below)
(Between blue and red) 0.35
(Between black and red) ... 0.32
・ Print section evaluation (printing with B-419)
Hue density Color difference (before coloring)
Thermal coloring layer 4a Blue 1.3 −
Thermal coloring layer 4b Black 1.5-
Thermosensitive coloring layer 4C Red 1.35 0.65
Thermal coloring layer 4c (see Comparative Example 1) Red 1.34
“Thermal coloring layer 4C”: Thermal coloring layer 4c to which a background hue adjusting agent is added

Color between colors when a colorant is added to the thermosensitive coloring layer:
(Corrosion plate with printing plate 150 lines, depth 40μm)

The color difference of the background portion is smaller after coloring than before coloring, and the effect of the thermosensitive coloring layer 4C to which the background hue adjusting agent is added is seen.
Even in the thermosensitive coloring layer 4C to which the background hue adjusting agent was added, the coloring density changed only 0.01 and the color difference was only 0.65 compared to before coloring. None. (In the case of color development visually, if the color difference is 3 or less, the difference in hue is not well understood.)

<Example 2>
In Example 1, the background color adjusting agent was added to the thermosensitive coloring layer 4c to obtain the thermosensitive coloring layer 4C, and the boundary between the thermosensitive coloring layer 4b and the thermosensitive coloring layer 4a was made inconspicuous.

  Here, as a modified example, the background hue adjustment agent is not added to the thermosensitive coloring layer 4c, but the background hue adjustment is performed on the entire ink receiving layer as long as the ink receiving layer 3 provided on the substrate 2 is not hindered. A method of adding an agent and making the boundary portion due to the color difference between the heat-sensitive color layers 4a, 4b and 4c formed integrally with the ink receiving layer 3 inconspicuous will be described.

  For example, in the case of the heat-sensitive color developing layer using the electron donating compound as shown in Example 1, the black heat-sensitive color developing layer 4b is dark in hue, and the boundary with the heat-sensitive color developing layers 4a and 4c of other colors. The part is visually problematic.

  In order to alleviate this problem, it is possible to alleviate the ink receiving layer 3 by adding a colorant which is a black aqueous dye as a background hue adjusting agent to make the whole black. In that case, the black thermosensitive coloring layer 4b also becomes black, but the boundary is relaxed. In particular

◎ Ink Receiving Layer Added with Background Hue Modifier DUASYN D. 4.9 parts by weight of the background hue modifier. The same as Example 1 except that BLACK HEF-SF liq (manufactured by Clariant) was added.

Formation of thermosensitive coloring layers 4a, 4b and 4c The same as Example 1 except that the colorant of thermosensitive coloring layer 4C was removed.

Result / Visibility: Overall, the image appears darker than in Example 1, but the difference in the boundary is not felt so much and it is close to normal thermal paper.
・ Color difference: (Refer to [Table 3] below)
(Between black and blue) ... 0.51
(Between blue and red) 0.56
(Between black and red) 0.52
・ Print section evaluation (printing with B-419)
Hue density Color difference (before coloring)
Colorant in ink receiving layer Heat-sensitive coloring layer 4a Blue 1.25 2.60
Thermal coloring layer 4b Black 1.46 4.23
Thermosensitive coloring layer 4c Red 1.31 6.38
Ink-receiving layer standard (Comparative Example 1)
Thermal coloring layer 4a Blue 1.30 −
Thermal coloring layer 4b Black 1.50 −
Thermal coloring layer 4c Red 1.34 −

Color difference between colors of thermosensitive coloring layer when background color modifier is added to ink receiving layer:
(Corrosion plate with printing plate 150 lines, depth 40μm)

  From the above results, the effect of correcting the background portion density can be obtained even if a background hue adjusting agent is added to the ink receiving layer 3. However, when a background hue adjusting agent is added to the ink receiving layer 3 in the color developing portion, the color changes greatly, and in particular, the red hue changes, but there is no problem visually. (Treated with different color)

  In Example 1, an ink was prepared by adding an electron-accepting compound to the ink-receiving layer 3 and adding at least an electron-donating compound and a water-dispersed ink in which a background color adjusting agent was added to the water-dispersed ink. The method for forming the heat-sensitive color forming layers 4a and 4b and the background color adjusting agent 4C to which the background hue adjusting agent is added to the receiving layer 3 by using a printing method or the like has been described so that the boundary between the colors is not noticeable. A heat-sensitive water-dispersed ink containing a donor compound, an electron-accepting compound, and a background hue adjusting agent may be formed on the ink receiving layer 3.

  In Example 2, a heat-sensitive color developing layer by printing or the like with water-dispersed ink containing at least an electron donating compound on the ink receiving layer 3 provided with a coating liquid containing at least an electron accepting compound and a background hue adjusting agent on the substrate. Although the method for forming 4a, 4b and 4c has been described, the heat-sensitive color developing layer may be formed using a heat-sensitive water-dispersed ink to which at least an electron accepting compound and an electron donating compound are added.

<Comparative Example 1>
The same as in Example 1 except that no background hue adjusting agent was added and the heat-sensitive color forming layer 4c was prepared in the same manner as the other heat-sensitive color forming layers 4a and 4b.

◎ Results / Visibility: No problem because the border is inconspicuous.
(Between blue and red) 0.65
(Between black and red) ... 0.50
・ Print section evaluation (printing with B-419)
Hue density
Thermal coloring layer 4a Blue 1.3
Thermal coloring layer 4b Black 1.5
Thermal coloring layer 4C Red 1.34
* Thermal coloring layer 4C: Thermal coloring layer 4c with a background hue adjusting agent added

  From the above results, the color difference between the blue thermosensitive coloring layer 4a and the red thermosensitive coloring layer 4c was large, and the boundary portion could be discriminated.

<Comparative example 2>
DUASYN which is a background hue adjusting agent. The same as Example 1 except that 0.039 parts by weight of the pigment concentration of BLACK HEF-SF liq (manufactured by Clariant) was added to form a thermosensitive coloring layer 4C.

◎ Result / Visibility: Since the background of the red heat-sensitive color developing layer 4C to which the background color adjusting agent is added is dyed by the background color adjusting agent, the color difference is blacker than the other heat-sensitive color developing layers 4a and 4b, and the boundary portion is stand out.
·Color difference:
(Between black and blue) 0.50
(Between blue and red) 0.93
(Between black and red) ... 1.21
・ Print section evaluation (printing with B-419)
Hue Concentration Color difference (Comparison with before coloring)
Thermal coloring layer 4a Blue 1.3 −
Thermal coloring layer 4b Black 1.5-
Thermosensitive coloring layer 4C Red 1.34 2.28
* Thermal coloring layer 4C: Thermal coloring layer 4c with a background hue adjusting agent added

  From the above results, there is no problem in the density and color difference of the color development part, but if the amount of the background hue adjusting agent added to the water-dispersed ink is too large, the color difference increases and the boundary part can be clearly identified. Therefore, it is necessary to suppress to an appropriate amount of the background hue adjusting agent.

<Comparative Example 3>
DUASYN which is a background hue adjusting agent. The same pigment concentration of BLACK HEF-SF liq (manufactured by Clariant) as in Example 2 except that 7.5 parts by weight were added to the ink receiving layer.

◎ Result / Visibility: Since it becomes black as a whole, the difference in hue between the black thermosensitive coloring layer 4b and the other thermosensitive coloring layers 4a and 4c becomes inconspicuous, but the blue thermosensitive coloring layer 4a and the red thermosensitive coloring layer The difference in hue from 4b became noticeable.
·Color difference:
(Between black and blue) 0.53
(Between blue and red) 0.70
(Between black and red) 0.53
・ Print section evaluation (printing with B-419)
Colorant in the ink receiving layer Hue Concentration Color difference (Comparison with before coloring)
Thermosensitive coloring layer 4a Blue 1.28 2.41
Thermal coloring layer 4b Black 1.42 4.03
Thermosensitive coloring layer 4c Red 1.36 8.99

  If the concentration of the background hue adjusting agent in the ink receiving layer 3 to which the background hue adjusting agent is added is too high, the color difference between the blue thermosensitive coloring layer 4a and the red thermosensitive coloring layer 4c increases and the boundary becomes clear. The color difference of the part becomes conspicuous.

  From the above results, in particular, when a black or blue boundary portion is visible in the red thermosensitive coloring layer 4c and there is a problem in visibility, a suitable amount of background hue adjusting agent is added to the red thermosensitive coloring layer 4c. The boundary can be made inconspicuous by the layer 4C. Similarly, by adding an appropriate amount of the background hue adjusting agent to the entire ink-receiving layer, although the color changes as a whole, the boundary portion of the background portion in question can be improved.

  The amount, material, and hue of the background hue adjusting agent vary depending on the characteristics of the heat-sensitive water-dispersed ink and water-dispersed ink used. Specifically, it is possible to experimentally determine the type of background hue adjusting agent and the amount to be added so that each color difference is 0.6 or less.

  In the present embodiment, an example using a printing method has been shown. However, when a thermal coloring layer having a different hue is formed adjacently, for example, by a die coating method or the like, and the boundary is a problem, the thermal sensitivity of the background hue is light. It goes without saying that the boundary portion can be made inconspicuous by adding an appropriate amount of the background hue adjusting agent to the coloring layer.

1 is a plan view showing a configuration of a thermal recording medium 1 according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the thermal recording medium 1 shown in FIG. It is the schematic diagram which showed the utilization form of the thermosensitive recording medium 1 in one Embodiment of this invention. 1 is a plan view showing a configuration of a thermal recording medium 1 according to an embodiment of the present invention. It is the schematic diagram which showed the utilization form of the thermosensitive recording medium 1 in one Embodiment of this invention. 1 is a cross-sectional view of a thermal recording medium 1 in an embodiment of the present invention. It is the figure which showed the relationship of the color difference between a printing plate and each color.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Thermal recording medium 2 Base material 3 Ink receiving layer 4 Thermal coloring layer

Claims (5)

  The density of the background hue of the thermal coloring layer of the thermal recording medium adjacent to the thermal recording medium in which a plurality of thermal coloring layers that are formed adjacent to each other on the surface of the base material with different hues are formed. In order to reduce the difference in density between the heat-sensitive color developing layer and the heat-sensitive color developing layer where the density of the background color is light, at least the background color adjusting agent is added to the heat-sensitive color developing layer having the light color density of the background color, A method for adjusting a background hue of a thermosensitive coloring layer, characterized by reducing a difference in density of the background of the layer. In a heat-sensitive recording medium in which a plurality of heat-sensitive color-developing layers that are colored in different hues by applying heat energy at least on the surface of a substrate are formed adjacent to each other,
Among the adjacent thermosensitive coloring layers, at least the density of the background hue is reduced in order to reduce the difference in density between the thermosensitive coloring layer where the background hue of the thermosensitive coloring layer is dark and the thermosensitive coloring layer where the density of the background hue is light. A thermal recording medium, wherein a background hue adjusting agent is added to a light thermal coloring layer.   The thermosensitive coloring layer is formed integrally with the ink receiving layer by impregnating the ink receiving layer provided on the surface of the substrate with water-dispersed ink in which a pigment component containing at least an electron donating compound is dispersed in water. The heat-sensitive recording medium according to claim 2, wherein The ink-receiving layer provided on the surface of the substrate is integrally formed by impregnating with water-dispersed ink in which a pigment component containing at least an electron-donating compound is dispersed in water, and at least with different hues by applying heat energy. In a heat-sensitive recording medium in which a plurality of heat-sensitive color-developing layers that are colored are formed adjacent to each other,
A thermal recording medium, wherein a background hue adjusting agent is added to the ink receiving layer in order to reduce a difference in background hue between adjacent heat-sensitive coloring layers.   The plurality of thermosensitive coloring layers include a thermosensitive coloring layer that develops a red color by thermal energy, and at least the background hue adjusting agent is added to the red thermosensitive coloring layer. The thermal recording medium according to any one of claims 1 to 4.

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