JPH0737187B2 - Thermal recording - Google Patents

Description

The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material that has good storability and is suitable for labels, prepaid cards and the like.

[Conventional technology]

Usually a colorless or light-colored substance such as a leuco dye, and a color developer such as a phenolic substance that reacts with this to develop a color, and each is dispersed in water together with a binder, and both liquids are mixed, By coating and drying on a substrate such as paper,
Thermosensitive recording materials have been manufactured and used in facsimiles, printers, and the like.

The thermosensitive recording medium has drawbacks such as (1) color development due to local pressure such as scratches, (2) background color changes during storage, and (3) printing fading during storage. Regarding the pressure coloring of (1), a method of providing a strong protective film is disclosed in Japanese Patent Laid-Open No.
-30437 and the like. For the discoloration of the background (2), a method using a storage stabilizer is disclosed in JP-A-48-101943. Also, divide the color developer and developer into two layers,
A method for preventing the reaction between the two is disclosed in JP-A-49-53840. Regarding the fading of the print in (3), a method using a storage stabilizer is disclosed in JP-A-48-58842.

In addition to the above problems, in applications such as labels and prepaid cards, when printing is read with a semiconductor laser,
Conventional leuco substances and color developers do not have absorption in the infrared and gold infrared regions, so that there is a problem that they cannot be read. On the other hand, a leuco dye having absorption in the gold infrared region has been proposed in JP-A-63-69687.

[Problems to be Solved by the Invention]

Although each of the above-mentioned conventional techniques has its own effect, in principle, the gradually progressing chemical change cannot be completely suppressed by the light rays, the organic gas, the plasticizer, etc., and there remains a problem. Further, there is an essential contradiction that the higher the sensitivity of color development is, the more easily color development under pressure and background fog occur.

As described above, the object of the present invention is, in principle, no pressure coloring or background fog, and there is no fading, and a substance that can be printed by a semiconductor laser can be used, and a conventional thermal recording device can be used. To create a new thermosensitive recording medium.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the present invention provides two or more coating layers having different colors on a substrate such as paper, and a portion which receives heat is a colored heat-fusible substance having two or more layers. Are melted and mixed with each other, and the background color (that is, the color of the outermost colored thermofusible substance)
, Which utilizes development in which a different color appears on the surface.

The thermosensitive recording medium of the present invention is composed of a base material layer such as paper or a plastic sheet and two or more coating layers provided on the base material layer.

When the outermost layer of the coating layer is the first layer, and is referred to as the second layer, the third layer ... in order toward the base material layer, the first layer is mainly composed of a colored heat-fusible substance. It is a layer. The second and subsequent layers are layers mainly composed of a colored heat-fusible substance having a different color from the layers above it. In order to prevent the first layer and the second layer from being mixed at the time of coating, and to increase the coloring sensitivity,
It is also possible to provide a layer of a colorless heat-fusible substance sensitizer between the first layer and the second layer. Also, in all cases, a protective coating can be provided on the first layer.

FIG. 1 is a schematic view illustrating the constitution of layers that can be carried out in the present invention.

The components of each layer will be described in detail below. As the colored and heat-fusible substance for the first layer, each color such as red, blue and yellow is approximately
Any dye that melts at a temperature of 60 ℃ or higher can be used, but as an example of a colored heat-fusible substance, CISolvent Yellow 2, CISolvent Yellow 16, CISol
vent Red 1, CISolvent Red 27, CISolvent Blue 1,
CISolvent Green 3, CISolvent Brown 3, etc. can be used.

When a layer of a colorless heat-fusible substance sensitizer is provided between the first layer and the second layer, the sensitizers generally melt each other during heating and can lower the flow start temperature of the dye. A substance may be used, and examples thereof include waxes such as polyethylene wax and stearic acid amide.

The second layer and below also have the same colored and heat-fusible substance as described above (however,
Different colors can be used for the outer layers).

In the case of performing printing readable by a semiconductor laser, the first layer is a layer of a colored heat-fusible substance having no absorption in infrared and near infrared, and any one of the second and subsequent layers, Preferably, the second layer is provided with a layer containing a colored heat fusible substance having absorption in infrared and near infrared as a main component.

HM-1084-P (manufactured by Mitsui Toatsu) and MR-GREEN LS-7010 (manufactured by Bayer) are examples of heat-fusible substances that have absorption in colored infrared and near infrared.

Each layer of the present invention uses a binder that binds a colored heat-fusible substance or a sensitizer, and examples of the water-based binder include starches, hydroxyethyl cellulose, methyl cellulose, caraboxymethyl cellulose, gelatin, casein, and arabic. Rubber, polyvinyl alcohol, diisobutylene / maleic anhydride copolymer salt, styrene / maleic anhydride copolymer salt, ethylene / acrylic acid copolymer salt,
Styrene / acrylic acid copolymer salt, styrene / butadiene copolymer emulsion, etc.
Preferably about 15 to 30% by weight is used. Further, as the solvent-based binder, for example, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polystyrene and its polymer, polyester and its polymer, vinyl chloride.
A vinyl acetate copolymer or the like is used.

In all of the above cases, a filler can be mixed in the first layer to prevent the adhesion of dust to the thermal head, or a lubricant such as stearic acid amide, zinc stearate, or wax can be mixed. It is also possible to provide a protective film such as polyvinyl alcohol or an ultraviolet curable resin. When the base material is paper, water resistance and solvent resistance are especially required, or when it is necessary to prevent the coating substance from entering the paper, or when the contact with the thermal head is increased An undercoat layer may be provided between the layer and the paper.

An example will be described below.

[Example 1] Liquid A Solvent Blue 1 100 parts PVA 10% aqueous solution 100 parts Water 150 parts was mixed and dispersed with a paint conditioner until the particle diameter of the dye was about 1 μm. Solution B Solvent Red 1 100 parts PVA 10% Aqueous solution 100 parts Water 150 parts Water is mixed with a paint conditioner until the particle size of the dye becomes about 1μ C Solution Solvent Yellow 2 100 parts PVA 10% aqueous solution 100 parts Water 150 parts is mixed and paint Disperse with a conditioner until the particle size of the dye becomes about 1μ, and further, 30 parts of zinc stearate aqueous dispersion (D-523, Chukyo Yushi Co., Ltd., 30% concentration) Silica (P-527, Mizusawa Chemical Co., Ltd.) 20 parts Prepare a stirred liquid by adding a mixture of 100 parts of PVA 10% aqueous solution and stirring.
On fine paper 50 g / m ^2, A was 2 g / m ² coated and dried on a solid basis, and on it, 2 g / m ² coating and the B solution in terms of solid content
After drying, the solution C was coated on the solid content in an amount of 3 g / m ² and dried to obtain the target recording paper.

The results of various tests described separately on the above recording paper are shown in Table 1 together with other examples.

In this example, the background color before recording was yellow, and the color of the recorded image was black. There was no change in the background and image density after storage.

[Example 2] Epoxy-modified PVA aqueous solution 800 parts (DR-587, 12% concentration manufactured by Electrochemical) Silica 20 parts Aqueous dispersion of zinc stearate 50 parts (D-523, 30% concentration manufactured by Chukyo Yushi) 200 parts water The coating liquid obtained in Example 1 was coated with the liquid obtained by dispersing in a homomixer at 2 g / m ^{2 in} terms of solid content and dried to obtain a recording paper.

[Example 3] PVA 10% aqueous solution 200 parts Silica 100 parts Water 100 parts was dispersed by a homomixer on a base paper, coated with 4 g / m ^{2 in} terms of solid content, and dried. 3 layers were provided in the same manner as in Example 1.

Example 4 Liquid A of Example 1 was coated on a base paper at 2 g / m ^{2 in} terms of solid content and dried, and then 100 parts of an aqueous dispersion of stearic acid amide (D-840, manufactured by Chukyo Yushi Co., Ltd., 33% concentration) PVA 10% Aqueous solution 100 parts Water 100 parts was mixed and dispersed with a homomixer.
/ m ^{2 was} applied and dried, and then the liquid C of Example 1 was applied and dried at 3 g / m ^{2 in} terms of solid content to obtain a target recording paper.

[Example 5] A solution prepared by mixing the solution A and the solution B of Example 1 in a ratio of 1: 1 was coated on a base paper at a solid content of 3 g / m ² and dried, and the solution C was added as a solid content. The target recording paper was obtained by applying 3 g / m ^{2 in} terms of conversion and drying.

[Example 6] 100 parts of heat-fusible dye HM-1084-P (manufactured by Mitsui Toatsu; blue dye) PVA 10% aqueous solution 100 parts Water 150 parts were mixed until the particle diameter of the dye was about 1 μm. The liquid dispersed by a paint conditioner is applied at 2 g / m ^{2 in} terms of solid content and dried, and then the liquid C of Example 1 is applied in an amount of 3 g in terms of solid content.
/ m ^{2 was} applied and dried to obtain the desired recording paper.

I recorded the barcode with a barcode printer and read it with a barcode reader that uses a semiconductor laser.
Among the embodiments of the present invention, only the recording paper of this embodiment is
It was readable.

[Example 7] D liquid Solvent Blue 1 100 parts Polyvinyl butyral 10 parts Ethanol 50 parts Toluene 50 parts solution E liquid Solvent Red 1 100 parts Polyvinyl butyral 10 parts Ethanol 50 parts Toluene 50 parts solution F liquid Solvent Yellew 2 100 parts Polyvinyl butyral 10 parts Ethanol 50 parts Toluene 50 parts To a solution of zinc stearate powder 30 parts Silica (P-527 manufactured by Mizusawa Chemical Co., Ltd.) 20 parts Polyvinyl butyral 10 parts Ethanol 50 parts Toluene 50 parts 3 kinds of coating liquid are prepared, and the liquid D is applied to the polyester film having a thickness of 40 μ at 2 g / m ^{2 in} terms of solid content and dried, and the solution E is applied to it in an amount of 2 g / m ^{2 in} terms of solid content. It was dried, and the liquid F was applied on it in an amount of 3 g / m ^{2 in} terms of solid content and dried to obtain the desired thermosensitive recording medium.

* Note 1. PVA in the examples indicates polyvinyl alcohol PVA 105 manufactured by Kuraray.

2. The thermal recording materials obtained in Examples 1 to 7 were adjusted with a super calendar so that the Beck's smoothness was 800 seconds,
The following tests were conducted.

〔Evaluation methods〕

1. Coloring test A commercially available GIII facsimile Copix 6500 (manufactured by Toshiba) was used for recording, and the image density was measured with a Macbeth densitometer RD-514 type.

2. Storage property The same sample as the color development test was stored at 2 levels of 40 ° C, 90% RH, 60 ° C, 15% RH for 24 hours, and then the same measurement as 1 was performed.

3. Reading with a semiconductor laser Print a barcode with a thermal barcode printer,
A reading test was carried out with a bar code reader that reads using a semiconductor laser.

[Operation / Effect] The principle of printing of the thermosensitive recording medium of the present invention is that two layers of different colors are used.
More than one layer is provided, and the respective components of the two or more layers are melted by heat to form a printing portion of a color different from the color of the background (outermost layer). Therefore, as described in the specification and examples, there is no pressure coloring, background fog, and fading at all, and substances that have infrared and near infrared absorption so that they can be read by a semiconductor laser can be freely selected from other than leuco dyes. effective.
Furthermore, since the color can be freely selected for absorption of visible light, for example, by obtaining black printing on a brown background,
It may also have a function to prevent copying at Xerox. In addition, in the case of a card or the like, the background can be darkened, such as black or red, and the function of protecting the confidentiality can be achieved by making the print invisible but recognizable by laser. In addition, the conventional heat-sensitive recording layer can be used as a recording material having an extremely low-temperature color development that always causes background fog.

[Brief description of drawings]

1 (a) to 1 (f) are examples of cross-sectional schematic views of the constitution of the present invention.

Claims (2)

[Claims] 1. A thermosensitive recording medium comprising two or more layers of different colors mainly composed of a colored heat-fusible substance on a substrate. 2. A colorless heat-fusible substance is sensitized between the outermost layer, which is mainly composed of the heat-meltable substance, and the layer below the layer which is mainly composed of heat-fusible substance. The thermal recording medium according to claim 1, further comprising an agent layer.