JPH0699665A - Heat-sensitive recording material - Google Patents

Abstract

PURPOSE:To provide high quality heat-sensitive recording material, which has high sensitivity, excellent image stability and heat resistance of white paper and in which near infrared part can be read. CONSTITUTION:The heat-sensitive recording material concerned is prepared by coatingly providing heat-sensitive color-developing layer and protective layer on base and, when necessary, by providing peel ply through pressure-sensitive adhesive layer on the other side of the base. The recording material concerned contains at least either one of 3,3-bis[2-(p-dimethyl aminophenyl)-2-2-(p- methoxymethyl)ethenil]-4,5,6,7 tetrachlorophthalide and 3,6-bis(dimethyl amino) phthalide as leucodye and 2,4'-dihydroxydiphenylsulfone as developer in the heat-sensitive color-developing layer.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a heat-sensitive recording material. More specifically, the present invention relates to a heat-sensitive recording material which has high sensitivity, is excellent in image storability, is excellent in heat resistance of white paper, and is capable of reading in a near infrared region by a semiconductor laser.

[0002]

2. Description of the Related Art Many thermal recording methods have been known for a long time. For example, a heat-sensitive recording paper using an electron-donating colorless dye and an electron-accepting compound is disclosed in JP-B-43-4.
No. 160, No. 45-14039, etc., and a thermal recording system using these thermal recording papers has recently been applied to various fields such as facsimiles, printers, and labels, and needs have expanded. In particular, for applications such as labels, with the downsizing and speeding up of equipment, color development at low energy, that is, high sensitivity and image storability, and durability in microwave ovens, that is, heat resistance of blank paper are required. ing. or,
The label for heat-sensitive recording has many uses as a bar code label for a POS (Point of Sale Information Management) system, and a method of optically reading a bar code or an OCR character with a scanner is rapidly expanding. In particular, a recording material that can be read by a semiconductor laser having a wavelength in the near-infrared region has been strongly demanded, but it could not be adapted for reading.

In order to increase the sensitivity, use of a sensitizer having a good compatibility between a leuco dye and a color developer (JP-A-60-82382, JP-B-63-42590) and oil absorption An intermediate layer of high pigment is applied (JP-B-57-52915), and the leuco dye and the developer are finely pulverized (JP-A-58-58).
76293) and various other means. The image storability is particularly high for plastics, especially for labels, and it is not possible with the color developer (bisphenol A) that is commonly used for faxcimil, etc. By using the above-mentioned color developer and further providing a protective layer thereon, a thermal recording paper having a balance between sensitivity and image storability has been put into practical use. Furthermore, in recent years, along with the demand for labels that can withstand use in microwave ovens, etc., the heat resistance of white paper is required, and the one having absorption in the near infrared region for reading the recording portion with a semiconductor laser has been demanded. However, none satisfying all of these characteristics was obtained.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to obtain a heat-sensitive recording material which is excellent in image storability, has the heat resistance of a blank sheet, and is capable of reading in the near infrared region.

[0005]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made extensive studies to improve the above-mentioned conditions and, as a result, were able to obtain the heat-sensitive recording material of the present invention. That is, the heat-sensitive recording material of the present invention is a heat-sensitive recording material obtained by sequentially coating a thermosensitive color-forming layer containing a colorless or light-colored leuco dye and a developer on the surface of a support, and a protective layer. In the layer, 3.3-bis [2- (P-dimethylaminophenyl) -2- (P-methoxyphenyl) ethenyl] -4.5.6.7 tetrachlorophthalide or 3 was used as the leuco dye. .6
-Bis (dimethylamino) fluorene-9-spiro-
At least one of 3 '-(6'-dimethylamino) phthalide and 2.4'-dihydroxydiphenyl sulfone are contained as the developer.

Further, the leuco dye of the present invention is characterized by being used in combination with a fluoran type leuco dye.

Further, the heat-sensitive recording material of the present invention is formed by coating a pressure-sensitive adhesive layer on the other surface of the support and attaching a release paper via the pressure-sensitive adhesive layer to form an integrated body. It is characterized by.

The heat-sensitive recording material of the present invention is mainly used for food labels, and conventionally, its image storability is important, and its plasticizer resistance and water resistance to vinyl chloride film for packaging are important. It was necessary to have image storability such as oil resistance against food oil, vinegar resistance, alcohol resistance, or light resistance. Conventionally, color developers (bisphenol A, p-benzylphenylbenzoic acid) that have been generally used for fascinomy are not sufficient, and 4,4′-dihydroxydiphenylsulfone and 4-isopropyloxyphenyl Bisphenol sulfones such as enyl 4′-hydroxyphenyl sulfone and bis (3-allyl, 4-hydroxy) diphenyl sulfone are used (JP-A-60-318).
No. 52, No. 60-208286, No. 60-4
No. 3192), and a protective layer mainly composed of a water-soluble polymer is provided on the thermosensitive coloring layer (Jitsuko Sho 59-990).
No. 9), an intermediate layer is provided if necessary for high sensitivity, and both high sensitivity and image storability are used at the same time.

In recent years, there has been an increasing demand for labels that can withstand use in microwave ovens and the like and that can be read by semiconductor lasers and the like, and the heat resistance of white paper and the reading of the near infrared region have become necessary. As for the heat resistance of white paper, the color is erroneously developed when it comes into contact with a hot plate or the like. Therefore, the temperature at which the color is developed is preferably as high as possible.
It is desirable that the density of the white paper measured by a Macbeth densitometer is 0.2 or less under the temperature condition of 0 ° C. The reading of the near-infrared part is 650 when the color-developing part is absorbed by the spectrophotometer.
Absorption at ~ 900 nm is required, but not in conventional systems.

In the heat-sensitive recording material of the present invention, 3.3-bis [2- (P-dimethylaminophenyl) -2- (P-methoxyphenyl) ethenyl] -as a leuco dye.
4.5.6.7 Tetrachlorophthalide or 3.6-bis (dimethylamino) fluorene-9-spiro-3'-
At least one of (6′-dimethylamino) phthalide,
Also, by using 2,4'-dihydroxydiphenyl sulfone as a color developer and sequentially laminating a thermosensitive coloring layer and a protective layer containing the same, the heat resistance of blank paper is provided, and high sensitivity and excellent image storability are provided. In addition, it was possible to obtain a heat-sensitive recording material capable of reading in the near infrared region.

For the label of the present invention, a release paper is usually attached to the other surface of the support through a pressure-sensitive adhesive layer. A permeation preventive layer or the like may be provided between the adhesive layer and the adhesive layer, but the present invention is not limited thereto.

The leuco dye and the color developer contained in the thermosensitive coloring layer are generally used after being pulverized together with a water-soluble polymer compound, and in order to enhance the sensitivity, the above-mentioned intermediate layer is provided. Or, it is used by reducing the crushed particle size.

The above-mentioned pigment for the intermediate layer is a porous and highly heat-insulating pigment from the viewpoints of improving sensitivity and dust adhesion, and has an oil absorption of 50 ml / 10 according to the JIS-K5101 method.
0 g or more of inorganic powder is used. For example, calcined kaolin, activated clay, silica, calcium carbonate, diatomaceous earth, etc. are mainly used, and further kaolin, talc, etc. can be used in combination. Examples of the water-based adhesive include styrene-butadiene latex, acrylic resin emulsion, styrene-maleic anhydride polymer, polyvinyl alcohol, hydroxyethyl cellulose, starch, starch derivative, casein, gelatin and the like, and other dispersants and antifoaming agents. ,
Lubricants and the like can be added, and those used for general coated paper can be used.

The thermosensitive coloring layer provided on one side of the support is
The main component is a leuco dye and a color developer, but if necessary, a sensitizer (sensitivity improver), waxes, metal soaps, an ultraviolet absorber, etc. may be added, and a pigment or the like may be further mixed. .

The leuco dye in the heat-sensitive recording material of the present invention includes 3.3-bis [2- (P-dimethylaminophenyl) -2- (P-methoxyphenyl) ethenyl]-.
4.5.6.7 Tetrachlorophthalide or 3.6-bis (dimethylamino) fluorene-9-spiro-3'-
Although at least one kind of (6′-dimethylamino) phthalide is used, it is more effective to use an ordinary fluorane-based leuco dye together in order to improve characteristics such as hue and density.

Specific examples of fluoran leuco dyes include the following. Rhodamine B-anilinolactam, Rhodamine B-p-nitroanilinolactam, Rhodamine B-p-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-phenylfluorane, 3-diethylamino-7-3,4-dichloroanilinofluorane, 3-
Diethylamino-7- (2-chloroanilino) fluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-anilinofluorane, 3-ethyl-tolylamino-6-methyl −
7-anilinofluorane, 3-ethyl-tolylamino-
6-methyl-7-phenethylfluorane, 3-diethylamino-7- (4-nitroanilino) fluorane, 3-
Dibutylamino-6-methyl-7-anilinofluorane, 3- (N-methyl-N-propylamino) -6-methyl-7-anilinofluorane and the like.

Further, it is also possible to use a colorless dye which is used for general pressure-sensitive recording paper, heat-sensitive recording paper, etc. within a range that does not cause any trouble. Specifically, the following can be mentioned. (1) As a triarylmethane compound, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone)
3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3- (1,
2-dimethylindol-3-yl) phthalide, 3-
(P-Dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindole-3-
Yl) phthalide, 3,3-bis- (1,2-dimethylindol-3-yl) -5-dimethylaminophthalide,
3,3-bis- (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis-
(9-Ethylcarbazol-3-yl) -5-dimethylaminophthalide, 3,3-bis- (2-phenylindol-3-yl) -5-dimethylaminotalide, 3-p
-Dimethylaminophenyl-3- (1-methylpyrrol-2-yl) -6-dimethyl-aminophthalide and the like.

(2) As the diphenylmethane compound, 4,4'-bis-dimethylaminobenzhydrin benzyl ether, N-halophenyl leuco auramine,
N-2,4,5-trichlorophenyl leuco auramine and the like. (3) Benzoyl leuco methylene blue, p-nitrobenzoyl leuco methylene blue and the like as thiazine compounds.

(4) As the spiro-based compound, 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3,3'-dichloro-spiro-dinaphthopyran, 3-benzylspiro-dinaphthopyran, 3-methylnaphtho- ( 3-methoxy-benzo) -spiropyran,
Examples thereof include 3-propyl-spiro-dibenzopyran and the like, or a mixture thereof. The use of these is determined by the application and the required characteristics.

The developer used in the heat-sensitive recording material of the present invention is 2,4'-dihydroxydiphenyl sulfone, but it is a developer such as a phenol derivative or an aromatic carboxylic acid derivative as long as it does not cause any trouble. Can be used together. Specifically, as phenols, p-octylphenol, p-tert-butylphenol, p-phenylphenol, 1,1-bis (p-hydroxyphenyl) propane, 2,2-bis (p-hydroxyphenyl) propane, 1,1-bis (p-hydroxyphenyl) pentane, 1,1-bis (p-hydroxyphenyl) hexane, 2,2-bis (p-hydroxyphenyl) hexane, 1,1-bis (p-hydroxyphenyl) -2-ethyl-hexane, 2,2-bis (4-hydroxy-3,
5-dichlorophenyl) propane and the like can be mentioned.

As the aromatic carboxylic acid derivative, p-hydroxybenzoic acid, ethyl p-hydroxybenzoate, p
In butyl hydroxybenzoate, 3,5-di-tert-butylsalicylic acid, 3,5-di-α-methylbenzylsalicylic acid and carboxylic acid, these polyvalent metal salts and the like can be mentioned.

Examples of waxes include paraffin wax, carnauba wax, microcrystalline wax, polyethylene wax and the like, as well as higher fatty acid amides such as ethylene bisstearamide and higher fatty acid esters.

Examples of the metal soap include higher fatty acid polyvalent metal salts such as zinc stearate, aluminum stearate, calcium stearate and zinc oleate.

The sensitizer used for improving the sensitivity in the present invention is considerably limited in terms of heat resistance, but oxalic acid di-p-methylbenzyl ester,
Oxalic acid di-p-chlorobenzyl ester, 2-benzyloxynaphthalene, esters of benzoic acid and terephthalic acid, naphthalenesulfonic acid esters, naphthyl ether derivatives, anthryl ether derivatives, aliphatic ether derivatives, other phenanthrenes, fluorenes It is possible to use sensitizers such as the above, and it is also possible to use the above waxes together as a sensitizer.

Each of the above materials is dispersed and applied in a binder (adhesive). The binder is generally water-soluble, for example, polyvinyl alcohol,
Examples thereof include hydroxyethyl cellulose, hydroxypropyl cellulose, ethylene-maleic anhydride copolymer, styrene-maleic anhydride copolymer, isobutylene-maleic anhydride copolymer, polyacrylic acid, starch derivative, casein, gelatin and the like. Further, in order to impart water resistance to these binders, a water resistance agent (gelling agent,
Cross-linking agent), emulsion of hydrophobic polymer,
For example, styrene-butadiene rubber latex, acrylic resin emulsion and the like can be added.

As the support, paper is generally used, but resin film, synthetic paper, non-woven fabric or the like can also be used. As an apparatus used for coating the intermediate layer and the heat-sensitive recording layer, a coater head such as a blade coater, an air knife coater, a roll coater, a rod coater or a curtain coater can be used.

Further, in order to improve the surface smoothness of the coated product, a machine calender, a super calender, a gloss calender, a brushing machine or the like can be used.

In the present invention, it is effective to provide an intermediate layer for increasing the sensitivity, and the coating amount in that case is not particularly limited, but if it is too small, the effect is small and too much. Since the strength of the paper becomes weak and it is not economical, it is 3 to 20 g / m ² , preferably 5 to 10 g / m ^2.
Is appropriate. The coating amount of the heat-sensitive recording layer on the support is not limited, but is usually 3 to 15 g / dry weight.
m ² , preferably in the range of 4 to 10 g / m ² .

In the present invention, a protective layer is generally provided on the heat-sensitive recording layer for solvent resistance and the like. As the protective layer material, for example, water-soluble polymers such as polyvinyl alcohol, various aqueous emulsions,
It is also possible to add pigments, waxes, water-proofing agents, etc., if necessary.

[0030]

As described above, the heat-sensitive recording material obtained by the method of the present invention is provided with a heat-sensitive coloring layer containing a leuco dye and a color developer on one side of a support, and a protective layer thereon, if necessary. It is a heat-sensitive recording material in which a release paper is provided on the opposite surface of a support through a pressure-sensitive adhesive layer. In the thermosensitive coloring layer, 3.3-bis [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -as a leuco dye.
4.5.6.7 Tetrachlorophthalide or 3.6-bis (dimethylamino) fluorene-9-spiro-3'-
At least one of (6′-dimethylamino) phthalide,
And, by containing 2,4'-dihydroxydiphenyl sulfone as a color developer, it is possible to obtain a heat-sensitive recording material having heat resistance of white paper, high sensitivity, excellent image storability, and readable in the near infrared region. I was able to. The reason is
It is considered that due to the compatibility with the leuco dye and the color developer, both heat resistance and high sensitivity were compatible, and reading in the near infrared region was possible.

[0031]

EXAMPLES Next, the present invention will be described in more detail by way of examples. All parts and% shown below are based on weight. The value indicating the amount of smear is the amount of smear after drying unless otherwise specified.

Example 1 1. Preparation of the mid layer 1 Ansilex (calcined kaolin made by Engelhard, oil absorption amount according to JIS-K5101 method 80 ml / 100 g) 100 parts 10% sodium hexametaphosphate 4 parts 20% MS4600 (manufactured by Nippon Shokubai) 30 parts 48% Styrene-butadiene copolymer latex 40 parts Water 90 parts by stirring to disperse the intermediate layer 1 coating liquid, and smear the amount of 8.5 g / m ² onto the base paper of 40 g / m ^{2 with} a blade coater to form the intermediate layer 1 And

2. Preparation of thermosensitive coloring layer 1) Preparation of solution A 3.3-Vise [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4.5.6.7 tetrachlorophthalide 35 parts 5% polyvinyl Alcohol 105 parts Liquid A was pulverized using Dynomill (manufactured by Shinmaru Enterprises) to a volume average diameter of 0.8 μm. 2) Preparation of solution B 2,4'-dihydroxydiphenyl sulfone 70 parts 5% Polyvinyl alcohol 100 parts 40% Zinc stearate emulsion (Chukyo Yushi, Hyderin SZ40) 20 parts Solution B is Dynomill (Shinmaru Enterprises) Was used to pulverize to a volume average diameter of 1.1 μm. 3) Preparation of solution C Light calcium carbonate 35 parts 10% Sodium hexametaphosphate 3.5 parts Water 63 parts The solutions A, B and C prepared above were mixed, and further 10%
The PVA liquid was added so that the solid content was 20% of the total solid to obtain a thermosensitive coloring layer coating liquid.

This thermosensitive coloring layer coating liquid is applied onto the intermediate layer,
A hand-painted bar was smeared at a coating amount of 4 g / m ² to obtain a heat-sensitive recording material.

Next, as a protective layer liquid, 10% polyvinyl alcohol 100 parts 40% zinc stearate emulsion liquid (Hydrin SZ40 manufactured by Chukyo Yushi Co., Ltd.) 5 parts 20% silicic acid (Mizukasil P527 manufactured by Mizusawa Chemical Co., Ltd.) 50 parts 3 g / m ² with a hand-painted bar on the thermosensitive coloring layer
Smear it so that it is 600 on a Beck smooth on a calendar
The treatment was carried out so that it would be ~ 800 seconds.

Example 2 3.3-bis [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -of Example 1
4.5.6.7 Instead of tetrachlorophthalide, 3.6
-Bis (dimethylamino) fluorene-9-spiro-
Example 1 was repeated except that 3 '-(6'-dimethylamino) phthalide was used.

Example 3 Regarding the leuco dye used in Example 1, 3.3-bis [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4.5.6 In the same manner as in Example 1 except that 0.7 tetrachlorophthalide and 3.6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide were used in a combined ratio of 1/1. A thermosensitive recording material was obtained.

Example 4 About the leuco dye of Example 1, 3.3-bis [2-
(P-Dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -4.5.6.7 tetrachlorophthalide and 3- (N-methyl, Nn-propylamino)-
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 6-methyl-7-anilinofluorane was used in a ratio of 1 / 0.2.

Example 5 Regarding the leuco dye of Example 1, 3.6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide and 3- (N-methyl, N- A heat-sensitive recording material was obtained in the same manner as in Example 1 except that n-propylamino) -6-methyl-7-anilinofluorane was used in a ratio of 1 / 0.2.

Comparative Example 1 A thermosensitive recording material was obtained in the same manner as in Example 1 except that 4.4'-dihydroxydiphenylsulfone was used in place of 2.4'-dihydroxydiphenylsulfone in Example 1. .

Comparative Example 2 Example 1 was repeated except that bisphenol A was used instead of 2,4'-dihydroxydiphenyl sulfone of Example 1.
A heat-sensitive recording material was obtained in the same manner as in.

Comparative Example 3 A thermosensitive recording material was prepared in the same manner as in Example 1 except that 4-hydroxy-4'-isopropyloxydiphenylsulfone was used in place of 2,4'-dihydroxydiphenylsulfone of Example 1. Got

Comparative Example 4 3.3-bis [2- (p-dimethylaminophenyl) -2- (p-methoxyphenyl) ethenyl] -of Example 1
4.5.6.7. Instead of tetrachlorophthalide, 3-
(N-methyl, N-n propylamino) -6-methyl-
A thermosensitive recording material was obtained in the same manner as in Example 1 except that 7-anilinofluorane was used.

Comparative Example 5 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the protective layer was removed.

Comparative Example 6 A thermosensitive recording material was obtained in the same manner as in Example 1 except that the intermediate layer was omitted.

The thermal recording materials obtained in Examples 1 to 5 and Comparative Examples 1 to 6 were evaluated for sensitivity, heat resistance of blank paper, image storage stability, and reading in the near infrared region. Is shown in Table 1. The evaluation methods are as follows.

The sensitivity depends on the labeler (ISHIDA, IF2
1EX, 0.65ms, 23V) print density measured with a Macbeth densitometer. The larger the number, the higher the sensitivity.
Practically, at least 0.9 or more is desirable.

The heat resistance of white paper is the density of the rise of static color development as an index for observing the background fog of the white paper in a microwave oven, the value measured at 100 ° C. with a Macbeth densitometer, and the number is The smaller the better, the more practically 0.2 or less is desirable.

The storage stability of the image is the storage stability with a plasticizer, and the residual rate of the image when three diamond laps G (manufactured by Mitsubishi Plastics) are superposed on the image part and treated at 40 ° C. for 24 hrs. The larger the number is, the better the storage stability is, and practically 80% or more is desirable.

The near red portion is read by a self-recording spectrophotometer (H
The absorbance at 650 to 800 nm in ITACHU320 type) was measured, and the one having absorption was marked with ◯.

[0051]

[Table 1]

[0052]

As is apparent from the examples, the present invention has high sensitivity, has the heat resistance of a blank sheet, is excellent in image storability, and is capable of reading the near red portion.

Claims (3)

[Claims] 1. A thermosensitive recording material comprising a support and a thermosensitive coloring layer containing a colorless or light-colored leuco dye and a color developer and a protective layer, which are sequentially coated on the surface of the support. 3.3-bis [2- (P-dimethylaminophenyl) -2- (P-methoxyphenyl) as leuco dye
Ethenyl] -4.5.6.7 tetrachlorophthalide or at least one of 3.6-bis (dimethylamino) fluorene-9-spiro-3 '-(6'-dimethylamino) phthalide, and the developed color A heat-sensitive recording material containing 2.4'-dihydroxydiphenyl sulfone as an agent. 2. The heat-sensitive recording material according to claim 1, wherein the leuco dye is used in combination with a fluoran-based leuco dye. 3. The pressure-sensitive adhesive layer is coated on the other surface of the support, and a release paper is attached through the pressure-sensitive adhesive layer to form an integrated body. 2. The heat-sensitive recording material according to 2.