JPH09267557A - Multi-colored recording and displaying medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To record with high resolution and clearly a color tone such as black color, etc., with high visibility by laminating successively a low temp. recording layer and a high temp. recording layer each with an electron-donating dye precursor and an electron-accepting compd. as main components. SOLUTION: A multi-colored recording and displaying medium is constituted by laminating successively a low temp. recording layer and a high temp. recording layer wherein recording is possible to react an electron-donating dye precursor on a substrate with an electron-accepting compd. and different color tones are exhibited. As materials for the low temp. and high temp. recording layer, heat, sensitive recording materials wherein electron-donating dye precursors and electron-accepting compd. are main components are arbitrarily selected. In addition, as the electron-donating dye precursor of the high temp. recording layer, those which perform color development into black or form a complementary color to the low temp. recording layer are pref. The electron-accepting compd. is used as a developer by combining with the electron-donating dye precursor. After the low temp. recording layer is formed on the substrate, a high temp. recording layer is formed thereon by dispersing enough the electron- donating dye precursor and the developer and making them into a coating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has an object of providing a display medium capable of recording a clear image of a color tone having high visibility and being excellent in environmental stability in a thermosensitive color display medium capable of multicolor recording. .

[0002]

2. Description of the Related Art A heat-sensitive recording medium is known in which a recording image is produced by contact between both substances by heat by utilizing a reaction between an electron-donating dye precursor and an electron-accepting compound. Since the recording device is easily miniaturized by a thermal head, it is used in a wide range of fields as a recording medium for facsimiles and thermal printers. Along with the demand for improved performance and diversification of thermal recording media, multicolor recording media capable of recording different color tones have been proposed. The multicolor recording methods are roughly classified into 1) low temperature recording layer color tone (single color) / low temperature recording layer and high temperature recording layer color tone (mixed color) 2) low temperature recording layer color tone (single color) / high temperature recording layer color tone (single color) ) (-The low temperature recording layer is decolored).

The specific structure proposed so far is as follows.
In 1), a high-temperature color-developing layer / low-temperature color-developing layer is laminated on a support,
In 2), a high-temperature coloring layer / decoloring layer / low-temperature coloring layer is formed on the support. Such a multi-color recording method is made up of a stack of layers that express different hues, and multi-color recording is possible by utilizing the difference in color development sensitivity of each layer. As a recording method, there is a demand for a dynamic coloring method using a heat-sensitive head capable of realizing higher speed processing than a heat stamp or the like. The color image produced by the thermal head greatly depends on the heat transfer of the medium.
In a multicolor recording medium in which different color tone developing layers are laminated, it is necessary to form a recording layer having a color for which a clear image is desired to be formed in an upper layer (a layer closer to the medium surface) closer to the thermal head.

[0004]

With the material and layer structure of the conventional multicolor recording display medium, in order to achieve the above performance, the low temperature recording layer provides a high image in the structure of 1) above, but at a low temperature. The recording layer must have a color tone that does not shield the lower layer. For example, a color with high visibility and high concealability such as black is 1).
With this configuration, a high image cannot be obtained. In the constitution of 2), due to the decoloring action of the low-temperature color-developing layer, there is no shielding effect as in the constitution of 1), so that a clear image can be obtained without any limitation in color tone. However, in the configuration of 2), since the decoloring effect is included, there is a problem that the recorded image is easily erased when stored in temperature and humidity, and there is also a problem that it cannot be used in applications requiring high storage stability. there were.

[0005]

In order to solve the above-mentioned problems, the present invention is a recording which can be recorded by a reaction between an electron-donating dye precursor and an electron-accepting compound and which exhibits different color tones. A multi-color recording display medium having a structure in which a low-temperature recording layer and a high-temperature recording layer are sequentially laminated on a support in a multi-color recording display medium having laminated layers.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In such a multi-color recording display medium, it is assumed that the color tone of the low temperature recording layer is a single color and / or the color tone of the low temperature recording layer and the high temperature recording layer is a mixture of colors, and the color tone of the high temperature recording layer is black. good. Regarding the recorded image by the thermal head, the closer to the thermal head, the better the heat transfer and the higher image can be obtained. Therefore, a clear image can be obtained by providing the high temperature recording layer with a hue having high visibility (for example, black). (In the constitution of the high temperature recording layer / low temperature recording layer on the support, the low temperature recording layer has a high resolution, but the hue is limited to the hue that does not shield the lower layer, so black is not possible.)

There is also an advantage by providing an intermediate layer between the low temperature recording layer and the high temperature recording layer. That is, it is possible to realize color separation by complete layer separation and prevent migration of the acidic substance to another recording layer. In addition, by separating the layers, each color tone is clearly colored, and by controlling the thickness between the two layers, the coloring sensitivity of each layer can be adjusted. Furthermore, when only the low-temperature recording layer is colored, the intermediate layer can prevent the high-temperature recording layer from being adversely affected by the electron-accepting compound in the low-temperature recording layer due to storage.

A protective layer may be provided on the high temperature recording layer. By doing so, it is possible to prevent deterioration of the recording layer due to heat from the thermal head and scratches.

The transparency of the layer on the low temperature recording layer is 50%.
When it is above, the color tone of the low temperature recording layer can be made clear without being covered by white turbidity. In the present invention, since the low temperature recording layer is present in the lower layer, it is essential to impart transparency on the low temperature recording layer in order to obtain a clear image.

The static color development start temperature (definition is the temperature at which color development begins by pressure bonding with a hot plate for 1 second) is 50 ° C. or higher and 100 ° C. or higher for the low temperature recording layer and the high temperature recording layer, respectively, and the high temperature for the low temperature recording layer. It is preferable that the difference in static color development start temperature of the recording layer is 50 ° C or more. This is because when the static color development start temperature of the low temperature recording layer is 50 ° C. or less, the sensitivity is too good and the storage stability is poor. The high temperature recording layer has a static color development start temperature of 10
At 0 ° C. or lower, the color density of the low temperature recording layer cannot be sufficiently obtained, and color separation cannot be performed. Further, if the difference in the static color development start temperature between the low temperature recording layer and the high temperature recording layer is 50 ° C. or less, a sufficient color density of the low temperature recording layer cannot be obtained and the high temperature recording layer develops color, so that good two-color separation cannot be obtained. .

In the multicolor recording / display medium of the present invention, paper, plastic film, synthetic paper, non-woven fabric, metal vapor deposition, etc. are used as the material of the support.

As the material for the low temperature recording layer and the high temperature recording layer, a heat sensitive recording material containing an electron donating dye precursor and an electron accepting compound as main components can be arbitrarily selected. As the electron-donating dye precursor, any of those applied to this type of heat-sensitive material as a leuco dye is arbitrarily applied.
In the case of full color, yellow, magenta and cyan colors are selected. For example, triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, spiropyran-based, indolinophthalide-based leuco compounds of dyes are preferably used, but the high-temperature recording layer develops black, or the low-temperature recording layer. It is preferable to form a complementary color with respect to the developed hue.

Next, the electron-accepting compound is used as a developer in combination with the electron-donating dye precursor, and various known materials are used.
Specific examples include the following acidic substances. Phenolic substances such as bisphenol A, octylphosphonic acid, nonylphosphonic acid, decylphosphonic acid, dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, eicosylphosphonic acid and α-hydroxyoctanoic acid Acids, organic acids such as α-hydroxydodecanoic acid, α-hydroxytetradecanoic acid, α-hydroxyhexadecanoic acid, α-hydroxyoctadecanoic acid, metal complex compounds, thiodiphenylurea, quinone Class can be used.

Binder resins containing these recording materials include starches, celluloses, gelatin, casein, polyvinyl alcohols, maleic anhydride copolymers, acrylics, styrene-butadiene copolymer emulsions, urea resins, melamine. Examples thereof include resins, amide resins, polyurethane resins and the like.

If necessary, various auxiliaries can be added. Polyethylene wax and glyoxal as an antifoaming agent. As a sensitizer, stearic acid amide, behenic acid amide, methylenebisstearic acid amide, dibenzyl oxalate, trilbiphenyl ether and the like. Other kaolin,
Pigments such as clay, calcium carbonate, titanium oxide, styrene and micro silica are used.

The high temperature recording layer must be sufficiently pulverized and dispersed into fine particles by a sand mill or the like so as not to affect the image of the low temperature recording layer, and the average particle size is preferably 1 μm or less.

The protective layer not only prevents surface deformation due to heat and pressure when heat is applied, improves chemical resistance, water resistance, abrasion resistance, head matching properties, etc., but also improves transparency. As this material, a resin composition having desired physical properties for the surface protection layer is selected from the materials used for the binder resin of the recording layer described above. In particular, when surface scratch resistance, chemical resistance, and stain resistance are required, thermosetting resins or ionizing radiation curable resins such as ultraviolet rays and electron beams are usually used. The thickness is also selected depending on the desired physical properties and the like.
μm.

The intermediate layer is formed from the same material as the above-mentioned binder resin such as polyvinyl alcohol and methyl cellulose so as not to impair the transparency.

The sensitizing layer is the same as the intermediate layer and the protective layer.
The material is formed so as not to impair the transparency, and as the material, a resin such as hydrochloric acid-vinyl acetate resin, polyester resin, urethane resin or the like is used in addition to the binder resin used for the recording layer. Further, an encapsulation capsule, a filler or the like having a high heat storage effect may be added to these resins.

[0020]

EXAMPLES Examples and comparative examples will be described in detail.

Example 1 A low-temperature recording layer, a high-temperature recording layer and a protective layer having the following compositions were sequentially formed on a white polyethylene terephthalate (support) having a thickness of 188 μm by a gravure printing method, and multicolor recording of the present invention was carried out. A display medium was obtained. The low-temperature recording layer is a red dye (3-diethylamino-7-chlorofluorane), a color developer (3,3-dichlorophenylthiourea),
A mixture of a solvent (10% aqueous solution of polyvinyl alcohol) was dried and then formed to have a film thickness of 5 μm. The high temperature recording layer is a black dye (3- (N-ethyl-Nacylamino)-
A mixture of 6-methyl-7-anilinofluorane), a color developer (bisphenol A) and a solvent (10% aqueous solution of polyvinyl alcohol) was dried and then formed on the low temperature recording layer to have a thickness of 5 μm. . Both the black paint and the color developer in the high temperature recording layer were sufficiently dispersed in a sand mill to give an average particle size of 0.
It was made into a paint so as to have a thickness of 3 μm, and the transmittance of the high temperature recording layer at this time was 72%. The protective layer was formed of an ultraviolet curable resin (urethane acrylate). With this multicolor recording and display medium, a clear image was obtained without black phase dot recording and without the red phase being blocked by the upper layer.

Example 2 A white terephthalate (support) having a thickness of 188 μm and an intermediate layer having a thickness of 2 μm made of a 10% aqueous solution of polyvinyl alcohol were formed between the low temperature recording layer and the high temperature recording layer. In the same manner as in Example 1, a multicolor recording / display medium of the present invention was obtained. With this multicolor recording and display medium, a clear image was obtained without black phase dot recording and without the red phase being blocked by the upper layer. Furthermore, a clear red color could be maintained even during storage.

Comparative Example 1 A high temperature recording layer, a low temperature recording layer and a protective layer were sequentially formed on a white polyethylene terephthalate (support) having a thickness of 188 μm by a gravure printing method to obtain a multicolor recording display medium of a comparative example. . The composition of each recording layer was the same as in Example 1 in which the low temperature recording layer was a red layer and the high temperature recording layer was a black layer, and both the black dye and the color developer of the high temperature recording layer had an average particle size of 2 μm in a sand mill. It was made into a paint so that the high temperature recording layer had a transmittance of 42%. The protective layer was formed of an ultraviolet curable resin (urethane acrylate). In this multi-color recording display medium, black-colored dot recording was unclear (dot periphery was red edging).

Comparative Example 2 A low temperature recording layer, a decoloring layer, and a white terephthalate (support) having a thickness of 188 μm,
A high temperature recording layer and a protective layer were sequentially formed by a gravure printing method to obtain a multicolor recording display medium of a comparative example. Between the low temperature recording layer and the high temperature recording layer, 4,4-dithiomorpholine, 10
% Polyvinyl alcohol aqueous solution, except that a decoloring layer made of water was formed, the same configuration as in Comparative Example 1. In this multicolor recording display medium, the black phase dot recording was clear, but the black color disappeared during storage. (Storage test condition 50 ° C, 90%
RH, stored for 24 hours)

[0025]

The present invention is embodied in the form described above and has the following effects. A color tone such as black having high visibility can be clearly recorded with high resolution. Since it does not have a decoloring agent, it has excellent storage stability. Since the sensitizing layer is provided, it has a heat storage effect, so that it is possible to perform low-temperature recording with good storage stability and dynamic color development sensitivity. Good color separation can be obtained by providing an intermediate layer or adjusting the color density of each layer. By providing the protective layer, deterioration due to heat, scratches, etc. can be prevented.

Claims (6)

[Claims] 1. A multicolor recording / display medium comprising a recording layer which is recordable by a reaction between an electron-donating dye precursor and an electron-accepting compound and which has different color tones.
A multicolor recording / display medium having a structure in which a low temperature recording layer and a high temperature recording layer are sequentially laminated on a support. 2. The multicolor recording / display medium according to claim 1, wherein the color tone of the high temperature recording layer is black. 3. The multicolor recording display medium according to claim 1, further comprising an intermediate layer between the low temperature recording layer and the high temperature recording layer. 4. The multicolor recording and displaying medium according to claim 1, further comprising a sensitizing layer below the low temperature recording layer. 5. The multicolor recording / display medium according to claim 1, wherein a protective layer is provided on the high temperature recording layer. 6. The multicolor recording display medium according to claim 1, wherein the different color tones are a single color of the low temperature recording layer and a mixed color of the low temperature recording layer and the high temperature recording layer. .