JPS63315290A - heat sensitive recording material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a heat-sensitive recording material, which is particularly free from discoloration of image areas caused by chemicals and decolorization caused by plasticizers, and is resistant to water (or moisture). ) The present invention relates to a heat-sensitive recording material that has excellent chemical resistance and water resistance, and has excellent heat sensitivity without decoloring or elution or peeling of the heat-sensitive recording layer due to contact with the heat-sensitive material.

<Prior art and its problems> Thermal recording method has the advantage of being a simple mechanism, dry type, and maintenance-free, so it has been widely adopted in the fields of border smudges and various printers. Among these thermal recording methods, thermal paper using leuco dye is widely used, but after recording, the image may disappear or change color due to fingerprints, diazo copy paper, cellophane tape, autoclave, ink, etc. . In addition, if it comes into contact with certain synthetic resin products for a long period of time, it will lose its color due to the plasticizer contained in the synthetic resin, so it has the disadvantage of poor storage stability. Therefore, its field of use was limited to temporary information transmission and recording.

In response to this current situation, attempts have been made to provide an organic solvent-soluble resin protective layer on the heat-sensitive recording layer to prevent discoloration and fading caused by chemicals, etc. -137155).

However, even with this technique, satisfactory effects have not been obtained. On the other hand, by using a water-resistant agent and a water-soluble polymer protective layer, the above-mentioned problems such as discoloration and fading of the image area caused by chemicals and plasticizers can be significantly improved. Some are used for tickets, etc.

However, since a water-soluble polymer is used as a binder, it has the disadvantage that its function as a recording medium is significantly impaired due to reduction in scratches, peeling, or elution of the heat-sensitive recording layer due to contact with water. Therefore, solutions to these problems are strongly desired in fields where durability of images after recording, such as water resistance, chemical resistance, and plasticizer resistance, is required.

<Object of the Invention> For the above reasons, the first object of the present invention is to provide a heat-sensitive recording material with excellent durability, which is free from discoloration of the image area due to chemicals and discoloration due to plasticizers. A second object of the present invention is to provide a heat-sensitive recording material that has excellent water resistance and does not cause scratches, peeling, or elution of the heat-sensitive recording layer due to contact with water. Moreover, the third object is to provide a heat-sensitive recording material which has high thermal sensitivity while having the characteristics targeted by the first and second objects.

Means for Solving the Problems〉 The present invention, which has been made to achieve the above objects, has the following features:
In a heat-sensitive recording material provided with a leuco dye, a color developer that develops color from the leuco dye by heating, and a heat-sensitive recording layer mainly composed of a thermoplastic resin, the leuco dye is expressed by the following general formula (
A dimer of a fluoran compound represented by 1) is made, the thermoplastic resin is made soluble in an organic solvent and insoluble in water, and a fluoran compound represented by the following general formula (2) is used as a sensitizer. By adding K, the problems of the prior art are solved.

<Details of the invention The heat-sensitive recording material will be described in detail below.

The heat-sensitive recording material of the present invention mainly consists of a leuco dye on a support, a color developer that develops color from the leuco dye by heating, a sensitizer that is a melting point depressant for the leuco dye, and a thermoplastic resin. The heat-sensitive recording material of the present invention may have a structure in which a protective layer is further provided on the heat-sensitive recording layer.Here, the thermoplastic resin used in the present invention That is, the polymer binder is a resin that is soluble in organic solvents and is insoluble in water.Therefore, it can prevent scratches, peeling, or elution of the heat-sensitive recording layer caused by contact with water. This effect achieves the second object of the present invention.

As described above, the thermoplastic resin used in the present invention is soluble in organic solvents and is used as a polymer binder, so the color developer that causes the leuco dye to develop color when heated is limited. This is because if a color developer that is soluble in organic solvents is used, the color may develop in the coating solution or during coating, resulting in background fog when the recording layer is coated on the support. Occurred,
This is because it impairs the commercial value as a recording material and is not desirable. Therefore, as a color developer, it is necessary to select, for example, a compound that is insoluble in aromatic hydrocarbon solvents and can cause the leuco dye to develop color when heated. The following compounds can be considered as such compounds.

Sunawachi, Hensyl-p-hydroxybenzoate, 4
-Methylbenzyl-p-hydroxybenzoate, 4-
Methoxybenzyl-p-hydroxybenzoate, 4,
4'-dihydroxy-3,5-sialyldiphenylsulfone, methyl-bis(hydroxyphenyl)anatate, ethyl-bis(hydroxyphenyl)acetate),
4-(3-10lobenzyloxy)phenyl-4-hydroxyphenylsulfone, 4-(3-methylbenzyloxy)phenyl-4'-hydroxyphenylsulfone,
Examples include 4-pendyloxyphenyl-4'-hydroxyphenylnulphone, 3,4-dihydroxyphenyl-p-)lylsulfone, and the like. However, it is not limited to these.

By using the color developer, a recording material with relatively high whiteness and relatively free of background caps can be obtained.

However, in order to obtain more sufficient whiteness of the background, it is necessary to use a dimer of a fluoran compound represented by the general formula (1) as the dye.

In addition, since the dye generally has a high melting point, the thermal sensitivity of the recording material decreases, so the general formula ( It is necessary to add a sensitizer represented by 2).

The dyes and sensitizers used in the present invention will be described in detail below with specific examples.

Examples of the leuco dye include the following. However, these are limited to 3-diethylamino-7-chlorofluorane, 2-(
2-Fluorophenylamino/)-6-dinithylaminofluorane, 2-(2-fluorophenylamino)-6-
di-n-butylaminofluorane, 3-diethylamine-7-cyclohexylaminofluorane, 3-diethylamino-5-methyl-7-t-butylfluorane, 3-diethylamino-5-methyl-7-t-butylfluorane
Diethylamine-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-p-butylanilinofluorane, 3-cyclohexylamino-6-chlorofluorane, 2-anilino-3-methyl- 5-(N
-ethyl-I)-)luidino)fluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 3-pyrrolidino-7-cyclohexylaminofluorane, 3-N
-Methylcyclohexylamino-6-methyl-7-anilinofluorane, 3-N-ethylpentylamino-6-
Examples include methyl-7-anilinofluorane. However, it is not limited to these.

Further, the thermoplastic resin used in the present invention may be any thermoplastic resin as long as it is water-insoluble and soluble in organic solvents such as aromatic hydrocarbons or hydrocarbons. Here, the thermoplastic resin is used as a polymer binder in the heat-sensitive recording layer of the heat-sensitive recording material of the present invention. Specifically, polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate, polybutyl acrylate, polystyrene, acrylic-styrene copolymer, polyester resin, polyα-methylstyrene, ABS resin, coumaron resin, nitrocellulose, etc. can be mentioned. These resins are insoluble in water and in common solvents such as alcohols, petroleum, oils and fats.

In addition, the heat-sensitive recording layer may contain auxiliary additives to improve the clarity of the image, such as fine powders such as calcium carbonate, silica, alumina, and talc, and ultraviolet absorbers and oxidizing agents to improve the weather resistance of the image. The addition of these does not impair the properties of the heat-sensitive recording material of the present invention.

In the present invention, a protective layer may be provided on the heat-sensitive recording layer having the above structure. Examples of the resin used for this protective layer include polyester resin, polymethyl methacrylate, polyethyl methacrylate, and polybutyl acrylate. Further, even if an auxiliary additive such as an ultraviolet absorber that improves the light resistance of the image is added to the protective layer, the characteristics of the present invention will not be impaired in any way.

Next, a method for producing a heat-sensitive recording material according to the present invention will be explained using an example. First, a thermoplastic resin is dissolved in a color developer dispersion uniformly dispersed in an aromatic hydrocarbon solvent. Next, a recording layer forming solution consisting of a leuco dye dispersed or dissolved in the coating solution and auxiliary additives added as necessary is applied to the paper.
A heat-sensitive recording layer having a solid content of 4 to 102/m2 is formed by coating on a support such as a plastic film or sheet by a coating method such as bar coating, blade coating, air knife coating, gravure coating, or roll coating and drying. A protective layer coating solution containing uniformly dispersed zinc stearate and using an acrylic resin as a polymeric binder is applied onto the layer by the same coating method as described above, and dried to a solid content of 1.
It can be manufactured by providing ~497 m2 of protective layer.

<Effects of the Invention> As detailed above, the heat-sensitive recording material of the present invention has a high degree of whiteness, and not only has basic properties such as image stability under temperature and humidity conditions and head matching properties, but also has excellent recording properties as a recording medium. In addition to imparting durability, high thermal sensitivity can also be obtained. Therefore, thermal recording media using leuco dyes can be used in a wide range of applications, such as recording media for tickets, cards, prepaid cards, and sticker-less commuter passes that require counterfeit prevention. can be used.

<Examples> Examples of the present invention will be shown below. Similarly, in each example, "part" means part by weight.

Example I Solution A Solution B The above components A solution and B solution were separately ground and dispersed in a sand mill for 2 hours, and then these dispersions were mixed with B for 4 parts of A solution.
Thoroughly mix 1 part of the solution to obtain a recording layer forming coating solution, apply it onto synthetic paper (Yupo EPGI 50, manufactured by Tamago Yuka Synthetic Paper Co., Ltd.) using a wire bar so that the dry weight is 797 m2, and dry. A heat-sensitive recording layer was obtained. Next, as a protective layer, the following component C liquid was applied onto the heat-sensitive recording layer to a dry weight of 2 f.
It was coated with a wire bar to give a coating density of 1/m2 and dried to obtain heat-sensitive recording paper.

Solution C Example 2 Solution A and Solution B The above components A and B were separately ground and dispersed in a ball mill for 12 hours. Add these dispersions to 4 parts of liquid A,
A recording layer forming coating solution was prepared by thoroughly mixing 1 part of the solution, and the coating solution was coated onto a 188 μm polyester sheet using a wire bar and dried to obtain a heat-sensitive recording layer so as to have a dry weight of 6,527 mm.

Next, as a protective layer, liquid C having the same components as those used in Example 1 was applied onto the heat-sensitive recording layer using a wire bar to a dry weight of 397 m'' and dried to obtain a heat-sensitive recording sheet.

Comparative Example Liquid A and Liquid B The above components A and B were separately ground and dispersed in a ball mill for 12 hours. Add these dispersions to 4 parts of liquid A,
A recording layer forming coating solution was prepared by thoroughly mixing 1 part of the solution, and the coating solution was coated onto a 188μ polyester sheet using a wire bar and dried to obtain a heat-sensitive recording layer so as to have a dry weight of 6.5η.

Next, as a protective layer, liquid C having the same components as those used in Example 1 was applied onto the heat-sensitive recording layer using a wire bar to a dry weight of 317 m2, and dried to obtain a heat-sensitive recording sheet.

<Evaluation of Examples> The obtained heat-sensitive recording material was coated with a thermal simulator (printing conditions: applied voltage 7 to 13 V, 2.5 m5ON10FF
) was used for thermal printing. The black density of the obtained recorded image was measured using a Macbeth reflection densitometer (RD-514). The results are shown in FIG.

As can be seen from FIG. 1, the heat-sensitive recording materials of the present invention obtained in Examples 1 and 2 have higher heat sensitivity than the comparative examples containing no sensitizer. Furthermore, the recording material of the present invention had excellent basic properties such as excellent heat resistance and temperature/humidity resistance after recording, and no fading of the image in the printed area and no background fogging in the non-printed area.

Furthermore, problems with conventional leuco-based thermal paper, such as the color being erased when it comes into contact with cellophane tape, eraser, or PVC sheet after recording, or discoloration when exposed to diazo copying paper, Signben ink, etc., are eliminated. It didn't happen.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the dynamic thermal sensitivity of the thermal recording materials shown in Examples 1 and 2 and Comparative Example. 1... Dynamic thermal sensitivity curve 2 of the thermal recording material shown in Example 1... 〃 2 3... Comparative example

Claims (1)

[Scope of Claims] A heat-sensitive recording material comprising, on a support, at least a heat-sensitive recording layer mainly composed of a leuco dye, a color developer that develops color from the leuco dye by heating, and a thermoplastic resin, wherein the leuco dye is A dimer of a fluoran compound represented by the following general formula (1), in which the thermoplastic resin is soluble in organic solvents and insoluble in water, and is a melting point depressant for the leuco dye, that is, the heat-sensitive recording material. A heat-sensitive recording material characterized in that a fluoran compound represented by the following general formula (2) is added as a sensitizer. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (1) [R_1 to R_6: hydrogen atom, amino group or its substituted product, alkyl group from C_1 to C_1_0, halogen R_7, R_8: hydrogen atom, alkyl group from C_1 to C_1_0, Allyl group] ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (2) [R_1 to R_4: Hydrogen base paper, amino group or its substituted product, alkyl group of C_1 to C_1_0, halogen]