JPH10181205A - Heat sensitive recording material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat sensitive recording material, with which a clear colored image is obtained, which is excellent in storage properties and also has a few curl and an excellent external appearance. SOLUTION: In a heat sensitive recording material, which is recorded and color-developed through the hot color developing reaction between a leuco dye and a developer, both of which mainly compose a heat sensitive color developing layer provided on a support, two or more coating layer of a heat sensitive recording surface containing the heat sensitive color developing layer are formed. Further, on the rear surface of the support, a back-coating layer mainly made of an anionic styrene-acrylic resin as a sizing agent of a neutralized paper is formed. The preferable solid pick-up of this back-coating layer is 0.5-5.0g/m<2> .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive recording material, and more particularly to a heat-sensitive recording material using a colorless or light-colored leuco dye as a color-forming material and a color developer at the time of heating.

[0002]

2. Description of the Related Art Recently, various information recording devices have been provided in response to the demands of society such as increase and diversification of information, and various information recording materials used for their outputs have been studied and researched.
It has been developed and put into practical use. Among them, the heat-sensitive recording material (1) does not require a complicated phenomenon process and is maintenance-free. (2) The apparatus can be manufactured relatively compact, the obtained recording material can be easily handled, and the running cost is low.
(3) Since there are advantages such as relatively fast recording without noise at the time of recording, such as facsimile field, printer field such as word processor and calculator, computer output, recorder field for medical measurement, ticket, etc. It is widely used in the field of vending machines and the like.

As a support for the heat-sensitive recording material, plain paper, synthetic paper, synthetic resin film and the like are used, and a heat-sensitive color-forming layer capable of causing a color-forming reaction at the time of heat melting is coated on these supports.
A thermosensitive recording material is obtained by forming by drying, and a colored image is obtained by heating this with a hot pen or a hot head.

[0004] The main characteristics required of such a heat-sensitive recording material are (1) sharpness of a color-developed image and (2) robustness of the color-developed image. As one means, a method of providing a precoat layer between the heat-sensitive color-forming layer and the support has been conventionally performed, and as one means for improving the fastness of the color-formed image of the above (2), an over-layer is provided on the heat-sensitive color-forming layer. A method of providing a coat layer (barrier layer) has been conventionally performed.

As described above, in recent years, in order to improve the characteristics of the heat-sensitive recording material, a method of manufacturing a coat layer on the heat-sensitive recording surface by multi-step coating has become common. Is getting bigger. The cause of curl during coating is the expansion or contraction of the support or coating layer during wet / dry, and the dry state during coating has a significant effect. As a general prevention method, the back side of the thermosensitive coloring layer coated surface A method of applying and drying water, a water-soluble resin, latex, or the like on the back surface of the support is often used. However, the drying conditions during coating were limited by the demand for higher line speed of the coating machine, and the application of water or resin on the back of the support was effective when only one layer of the thermosensitive coloring layer was applied. However, as described above, the effect was small when performing multi-step coating on the heat-sensitive coloring layer side, and it was difficult to prevent curling.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat-sensitive recording material having a clear color image, excellent storage stability, less curl, and excellent appearance.

[0007]

According to the present invention, a thermosensitive coloring layer containing a leuco dye and a developer is provided on a support, and the coating layer of the thermosensitive recording surface including the thermosensitive coloring layer is composed of two or more layers. Further, a back coat layer mainly composed of an anionic styrene acrylic resin is provided on the back surface of the support, which is the back side of the thermosensitive coloring layer, to prevent curling.

A method of preventing curling by providing a back coat layer has been conventionally performed. As a component of the back coat layer, water or a water-soluble resin such as starch or PVA, or an emulsion such as acryl or SBR is used. However, these were effective in preventing curling when only one layer of the thermosensitive coloring layer was applied, but the effect was extremely reduced when two or more layers were coated on the thermosensitive coloring layer side.

The present inventors have found that even in the case of two or more steps of coating on the heat-sensitive coloring layer side, curling can be sufficiently prevented.
As a result of intensive research and exploration of materials that exhibit excellent curl prevention effects, excellent curl prevention is achieved by providing a back coat layer composed mainly of anionic styrene acrylic resin on the back side of the support, which is the back side of the thermosensitive coloring layer. It has been found that the effect is exhibited, and the present invention has been completed.

The leuco dye used in the present invention may be used alone or as a mixture of two or more kinds.
Leuco compounds of dyes such as fluoran, phenothiazine, auramine, spiropyran and indolinophthalide are preferably used. Specific examples of leuco dyes are shown below.

3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p
-Dimethylaminophenyl) -6-chlorophthalide, 3
-Dimethylamino-5,7-dimethylfluoran, 3-
Diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-7- (o-chloroanilino)
Fluoran, 6'-chloro-8'-methoxy-benzoindolino-pyrrolospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrrolospiran, 3- (2 '
-Hydroxy-4'dimethylaminophenyl) -3-
(2′-methoxy-5′chlorophenyl) phthalide, 3
-(2'-hydroxy-4'dimethylaminophenyl)
-3- (2'-methoxy-5'-nitrophenyl) phthalide, 3-pyrrolidino-7-trifluoromethylanilinofluoran, 3-dibutylamino-6-methyl-7-
Anilinofluoran, 3-N-ethyl-N-amyl-6
-Methyl-7-anilinofluoran, and the like.

As the color developer used in the present invention, various compounds having an electron accepting property, which makes the leuco dye come into contact when heated and melted, are applied. Specific examples thereof are shown below.
4,4'-isopropylidenebisphenol, 4,4 '
-Isopropylidenebis (2-tert-butyl) phenol, 4,4'-butylidenebis (6-tert-butyl-2-methyl) phenol, 4,4'-thiobis (6-tert-butyl-2-methyl) phenol 4,4'-diphenylsulfone, 4-isopropoxy-4'hydroxydiphenylsulfone, benzyl p-hydroxybenzoate, isopropyl p-hydroxybenzoate, stearyl gallate, lauryl gallate, salicylanilide, 5-chloro- Salicylanilide,
2,4'-diphenol sulfone, 2,2'-diallyl-4,4'-diphenol sulfone, and the like.

In the present invention, various conventional binders can be used for binding the leuco dye and the developer on the support. Specific examples of such binders are as follows. It is on the street. Water-soluble polymers such as PVA, starch, hydroxymethylcellulose, carboxymethylcellulose, acrylamide / acrylic acid ester copolymer, styrene / maleic anhydride copolymer alkali salt, gelatin, casein, polyvinyl acetate, polyacrylic acid ester Emulsions such as ethylene / vinyl acetate copolymers, or styrene / butadiene copolymers,
Latex such as styrene / butadiene / acrylic copolymer, and the like.

Further, in the present invention, if necessary, auxiliary components in the thermosensitive coloring layer include, for example, a filler, an antioxidant, an antifoaming agent, an ultraviolet absorber, a fluorescent whitening agent, a surfactant,
A lubricant or the like can be added. In this case, as the filler, for example, other than inorganic fine powder such as calcium carbonate, silica, titanium oxide, aluminum hydroxide, zinc oxide, kaolin, talc, barium sulfate, urea formalin resin,
Organic fine powders such as styrene / methacrylic acid copolymer, polystyrene, and the like. Specific examples of the lubricant include higher fatty acids or their esters, amides or metal salts, and various waxes.

In the heat-sensitive recording material of the present invention, if necessary, a precoat layer may be used between the support and the heat-sensitive coloring layer, and specific examples of the filler, binder, auxiliary agent and the like used in the precoat layer may be used. Examples thereof include the same ones as exemplified in the thermosensitive coloring layer. The thermosensitive recording material of the present invention can have an overcoat layer as a protective layer on the thermosensitive coloring layer, and specific examples thereof are the same as those exemplified for the thermosensitive coloring layer.

As the support of the heat-sensitive coloring layer used in the heat-sensitive recording material of the present invention, any suitable material may be used, such as plain paper, synthetic paper, plastic film and the like. Further, in the present invention, the back coat layer is formed on the back surface of the support, and the styrene acrylic resin used as the main component may be any as long as it shows anionic property. The fillers, binders, auxiliaries and the like exemplified in the precoat layer can be used in the same manner. The coating amount of the back coat layer is appropriately adjusted depending on the coating amount on the surface of the thermosensitive coloring layer. However, if it is less than 0.5 g / m ² , the curl improvement effect is poor, and if it exceeds 5.0 g / m ² , it is not cost-effective. The range of 0.5 to 5.0 g / m ² is preferred.

[0017]

Next, the present invention will be described in detail with reference to examples and comparative examples. In addition, all parts or% indicating the composition described below are parts by weight. The support, precoat liquid composition, heat-sensitive liquid composition, overcoat liquid composition, and backcoat liquid used in the examples and comparative examples of the present invention are as follows.

(1) Support Support A: high quality paper, 60 g / m ² Support B: biaxially stretched PET film, 50 microns (2) Precoat liquid composition 70 parts of water 10% of PVA-117 30 parts of an aqueous solution (manufactured by Kuraray Co., Ltd.) and 20 parts of Brilliant 15 (calcium carbonate manufactured by Shiraishi Calcium Co., Ltd.) were mixed and adjusted to obtain a precoat.

(3) Composition of heat-sensitive liquid Preparation liquid A 10 parts 3-Dibutylamino-6-methyl-7-anilinofluoran 10 parts PVA-205 (manufactured by Kuraray) 10% aqueous solution 20 parts Liquid B preparation water 10 Part 4,4'-isopropylidene bisphenol 20 parts PVA-205 (manufactured by Kuraray Co., Ltd.) 10% aqueous solution 20 parts Both A and B preparations were pulverized by separate sand mills until the average particle diameter became 1 μm or less. Liquid A 50 parts, B
90 parts of liquid, 50 parts of 15% aqueous solution of PVA-205, 30 parts of calcium carbonate (oil absorption 20 cc / 100 g), water 2
0 parts were mixed and stirred to obtain a heat-sensitive liquid.

(4) Overcoat liquid composition Water 80 parts PVA-117 (manufactured by Kuraray) 10% aqueous solution 80 parts Brilliant 15 (calcium carbonate manufactured by Shiraishi Calcium Co.) 10 parts 30%, Z-7-30 (Chukyo Yushi Co., Ltd.) (Zinc stearate) was mixed and adjusted to obtain an overcoat solution.

(5) Back coat liquid Back coat liquid A: water Back coat liquid B: 5%, PVA-205 aqueous solution Back coat liquid C: 5%, CMC aqueous solution Back coat liquid D ... 5%, polymarine 1301 solution (Styrene acrylic resin manufactured by Arakawa Chemical Co., Ltd.) Backcoat solution E: 5%, polymarine 1308 solution (Styrene acrylic resin manufactured by Arakawa Chemical Co., Ltd.)

Each of the adjustment liquids is coated on a support with a Meyer bar, and the wet coating amount thereof is a precoat liquid... 30 g / m ² heat-sensitive liquid... 20 g / m ^2. Overcoat liquid: 20 g / m ² Back coat liquid: 20 g / m ² Each sample was dried for each coating, and the drying conditions were the same. All samples were calendered after the final coating and drying, and then at 20 ° C and 65%
The samples were allowed to stand for 8 hours under the constant temperature and constant humidity conditions to perform a humidity control treatment, thereby obtaining heat-sensitive recording materials of Examples and Comparative Examples. Details are shown below.

Example 1 A precoat solution having the composition (2) was applied on a support A (high quality paper, 60 g / m ² ) with a 30 g / m ² Mayer bar in a wet state, and then dried in a dryer at 60 ° C. The heat-sensitive liquid having the composition of (3) was applied on the substrate obtained by drying for 1 minute with a 20 g / m ² Mayer bar to form a plurality of coat layers, and then subjected to the same conditions as the pre-coat. And dried.
The back coat liquid D was applied to the back surface of the support on which a plurality of coat layers had been formed by wet coating with a 20 g / m ² Mayer bar, and then dried under the same conditions to obtain the heat-sensitive recording material of Example 1. .

Example 2 An overcoat solution of the above composition (4) was further wet-coated with a 20 g / m ² Mayer bar on the plurality of coat layers of Example 1 and dried under the same conditions. Is Example 1
In the same manner as in Example 1, a heat-sensitive recording material of Example 2 was obtained.

Example 3 A heat-sensitive recording material of Example 3 was obtained in the same manner as in Example 2 except that the backcoat liquid D of Example 2 was replaced with the backcoat liquid E.

Example 4 A heat-sensitive recording material of Example 4 was obtained in the same manner as in Example 3 except that the support A of Example 3 was replaced with the support B.

Comparative Example 1 A heat-sensitive liquid having the composition (3) was formed on a support A (high quality paper, 60 g / m ² ) by using a 20 g / m ² Mayer bar to form a plurality of coat layers. After the coating, the coating was dried in a dryer at 60 ° C. for 1 minute, and then the back coat liquid A was coated on the back surface of the support A with a 20 g / m ² Meyer bar wet and further dried in a dryer at 60 ° C. Thus, a heat-sensitive recording material of Comparative Example 1 was obtained.

Comparative Example 2 A precoat solution having the composition (2) was wet-coated with a 30 g / m ² Mayer bar on a support A (high quality paper, 60 g / m ² ) to form a plurality of coat layers. After the coating was applied, the resultant was dried in a dryer at 60 ° C. for 1 minute, and the same operation as in Comparative Example 1 was carried out to obtain a heat-sensitive recording material of Comparative Example 2.

COMPARATIVE EXAMPLE 3 The same procedure as in Comparative Example 2 was followed up to the application and drying of the heat-sensitive liquid. However, the overcoat liquid having the composition (4) was wet onto a heat-sensitive surface in a 20 g / m ² Mayer bar. After coating,
After drying in a dryer at 60 ° C. for 1 minute, the heat-sensitive recording material of Comparative Example 3 was obtained by performing a backcoating treatment with a backcoating liquid A in the same manner as in Comparative Example 1.

Comparative Example 4 A heat-sensitive recording material of Comparative Example 4 was obtained in the same manner as in Comparative Example 3 except that the backcoat liquid A of Comparative Example 3 was replaced with the backcoat liquid B.

Comparative Example 5 A heat-sensitive recording material of Comparative Example 5 was obtained in the same manner as in Comparative Example 3, except that the backcoat liquid A was replaced with the backcoat liquid C.

Comparative Example 6 A heat-sensitive recording material of Comparative Example 6 was obtained in the same manner as in Comparative Example 4, except that Support A of Comparative Example 4 was replaced with Support B.

Comparative Example 7 A heat-sensitive recording material of Comparative Example 7 was obtained in the same manner as in Comparative Example 1 except that the backcoat liquid A of Comparative Example 1 was replaced with the backcoat liquid D.

[0034]

[Table 1] From the results shown in Table 1, the color-formed images of the heat-sensitive recording materials of Examples 1 to 4 are clear, have excellent storability, and have good appearance with little curl.

Table 1 shows the evaluation of each heat-sensitive recording material. The heat-sensitive recording was performed using a heat-sensitive word processor (Toshiba Lupo 90-H).
X type), and the recorded density (D ₁ ) and the density (D ₂ ) after the preservation test were determined by Dainippon Screen Co., Ltd.
It was measured using an M-401 type. Further, the curl degree was measured at 20 ° C., 6 ° C. for each thermosensitive recording material aligned to A-4 size.
It was left standing on a flat surface under a constant temperature and humidity condition of 5%, and judgment was made by observing the average value of height measurements at four corners. In the storage stability test, each heat-sensitive recording material recorded under the above-mentioned maximum density condition of a word processor was left at 40 ° C. and 90% for 3 days to obtain a processed sample.

[0036]

As described above, the heat-sensitive recording material of the present invention comprises two or more coat layers on the heat-sensitive recording surface including a heat-sensitive coloring layer, and an anion for neutral size is provided on the back surface of the support which is the back side of the heat-sensitive recording surface. By providing the back coat layer containing a styrene-acrylic resin as a main component, it is possible to obtain a color image which is excellent in sharpness and fastness, and has excellent appearance with very little curl.

Claims (2)

[Claims] 1. A heat-sensitive recording material comprising a thermosensitive coloring layer comprising a leuco dye and a color developer as main components on a support, and recording and developing a color by a thermal coloration reaction between the leuco dye and the color developer. Two or more coat layers on the heat-sensitive recording surface including the heat-sensitive coloring layer were formed, and a back coat layer mainly composed of an anionic styrene acrylic resin as a sizing agent for neutral paper was formed on the back surface of the support. A heat-sensitive recording material characterized by the following. 2. The heat-sensitive recording material according to claim 1, wherein the solid content of the back coat layer is 0.5 to 5.0 g / m ² .