JP2779940B2 - Thermal recording material - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a heat-sensitive recording material, and more particularly, to a colorless or slightly pale color leuco dye at room temperature and a color-developing reaction between the leuco dye and a developer. The present invention relates to a heat-sensitive recording material.

[Related Art] In recent years, various recording materials have been researched and developed in the information recording field in accordance with social demands such as diversification and increase of information, resource saving and non-pollution, and are provided for practical use. Above all, the heat-sensitive recording material is (1) that color development is recorded by simply heating and a complicated developing step is not required; (2) that it can be manufactured using a relatively simple and compact apparatus; (3) paper is often used as a support. In this case, not only the cost of the support is low, but also the cost of the support is low.
Due to advantages such as the feel of the obtained recorded material being close to that of plain paper, computer output, printers such as calculators, recorders for medical measurement, low and high-speed facsimile, automatic ticket vending machines, thermal copying Etc. are widely used.

The thermosensitive recording material is usually manufactured by coating and drying a thermosensitive coloring layer liquid containing a coloring component capable of causing a coloring reaction by heating on a support such as paper, synthetic paper or a synthetic resin film, The thus obtained thermosensitive recording material is heated by a hot pen or a hot head to record a color image. As a conventional example of such a heat-sensitive recording material, for example, JP-B-43-4160 or JP-B-45-14039
However, such a conventional heat-sensitive recording material has, for example, a low thermal response, and cannot provide a sufficient color density at the time of high-speed recording.

As a method for remedying such a defect, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran is used as a leuco dye (JP-A-49-10912).
No. 0), development of high-sensitivity dyes using 3-dibutylamino-6-methyl-7-anilinofluoran (Japanese Patent Application Laid-Open No. 59-190891), substances having good coloring properties as developers,
-7-bis (4-hydroxyphenylthio) -3,5-dioxapeptane (JP-A-59-106456), 1,5-bis (4
A technique for increasing the speed and sensitivity by using -hydroxyphenylthio) -3-oxapentane (JP-A-59-116262) is disclosed. Also, JP-A-61-123
584, JP-A-61-215087, JP-A-61-242889 and the like also attempt to increase the speed and sensitivity by combining the substances mentioned above.

In order to realize such a high sensitivity, a protective layer is conventionally provided for improving the reliability of an image. However, it has become necessary to reduce the thickness of the protective layer in a direction not using the protective layer.
For this purpose, efforts have been made to improve the reliability of images in the heat-sensitive recording layer, but no satisfactory one has been obtained yet.

[Problems to be Solved by the Invention] The present invention is to provide a heat-sensitive recording material in which the above-mentioned conventional disadvantages are improved, that is, it has high sensitivity, low background fog under high temperature and high humidity, and wet hands. It is an object of the present invention to provide a heat-sensitive recording material free of stickiness even when touched by such a method.

[Means for Solving the Problems] According to the present invention, a heat-sensitive recording material having a color-forming layer containing a leuco dye and a developer as main components in a polyvinyl alcohol-based binder and having no protective layer is provided on the support. The contact angle between the recording surface and water at (TAPPI T458 os-70)
A heat-sensitive recording material characterized by being at least 60 ° is provided.

Although the reason why the background fog is reduced by setting the contact angle to 60 ° or more is not clear, it is at the boundary of the generation of fog of the heat-sensitive recording layer due to intrusion and intrusion of moisture from the surface of the thermosensitive recording medium. It is thought that it may be. Therefore, it is considered to be an important characteristic for a heat-sensitive recording material having no protective layer.

As a method for increasing the contact angle to 60 ° or more, the binder used in the heat-sensitive coloring layer largely acts, but the effects of fillers and lubricants for improving matching cannot be ignored. The characteristics of the binder used here are, in addition to those having good film forming properties of the sled itself, a crosslinking agent, a curing agent,
Examples of the material include those having improved film formability such as curing by light, heat, and the like, and those having extremely low hygroscopicity. Filler,
A general lubricant is used, but a lubricant having a large BET specific surface area and a large oil absorbing property are not preferable.

As a method for increasing the contact angle without using the protective layer, basically the same substances as those used for the protective layer are effective, but addition of a wax, an auxiliary agent, or the like is also effective.

Specifically, a crosslinking agent such as polyamide epichlorohydrin resin, trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β-aziridinylpropionate is added to the binder in an amount of 0.5 to 10%. % By weight. 1 to 30% by weight of an ammonium salt of maleic anhydride, an ammonium salt of a diisobutylene / (anhydride) maleic acid copolymer, an ammonium salt of a diisobutylene / (anhydride) maleic acid / maleic imide copolymer, and the like. Addition, addition of 0.5 to 5% by weight of cationic surfactants such as amphoteric surfactants such as betaine derivatives and imidazoline derivatives, fatty acid amine acetate derivatives and alkylammonium chloride, and BET specific surface area
Adds 10 to 40% by weight of fillers such as calcium carbonate, aluminum hydroxide, aluminum silicate, magnesium hydroxide, calcium gayate, magnesium silicate, etc., with an oil absorption of 50 or less and 100 or less, and other water repellents, waxes, etc. Addition is also preferred. However, in the present invention, by adjusting the amount of addition, a contact angle of 60 ° or more can be achieved, and it is necessary to select the amount of addition by a method of combining materials.

The leuco dye used in the present invention may be used alone or
Such leuco dyes are applied as a mixture, and any of those applied to this type of heat-sensitive recording material may be arbitrarily applied.For example, triphenylmethane, fluoran, phenothiazine, auramine , Spiropyran-based, indolinophthalide-based dye leuco compounds are preferably used. Specific examples of such leuco dyes include, for example, those shown below.

3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis (p-dimethyl Aminophenyl) -6-diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofurf Oran, 3-dimethylamino-5,7-dimethylfluoran, 3- (N, N-diethylamino) -5-methyl-7-
(N, N-dibenzylamino) fluoran, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-
Pyrirospiran, 6'-bromo-3'-methoxy-benzoindolino-
Pyrirospiran, 3- (2'-hydroxy-4'-dimethylaminophenyl) -3- (2'-methoxy-5'-chlorophenyl) phthalide, 3- (2'-hydroxy-4'-dimethylaminophenyl)- 3- (2'-methoxy-5'-nitrophenyl) phthalide, 3- (2'-hydroxy-4'-diethylaminophenyl) -3- (2'-methoxy-5'-methylphenyl) phthalide, 3- ( 2'-methoxy-4'-dimethylaminophenyl) -3- (2'-hydroxy-4'-chloro-5'-
Methylphenyl) phthalide, 3-morpholino-7- (N-propyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7-trifluoromethylanilinofluoran, 3-diethylamino-5-chloro-7- (N -Benzyl-trifluoromethylanilino) fluoran, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluoran, 3-diethylamino-5-chloro-7- (α-phenylethylamino) fluoran, 3 -(N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluoran, 3-diethylamino-7- (o-methoxycarbonylphenylamino) fluoran, 3-diethylamino-5-methyl-7- (α -Phenylethylamino) fluoran, 3-diethylamino-7-piperidi Fluoran, 2-chloro-3-(N-Mechirutoruijino) -7-
(Pn-butylanilino) fluoran, 3- (N-methyl-N-isopropylamino) -6
Methyl-7-anilinofluorane, 3-dibutylamino-6-methyl-7-anilinofluoran, 3,6-bis (dimethylamino) fluorenespiro (9,
3 ')-6'-dimethylaminophthalide, 3- (N-benzyl-N-cyclohexylamino)-
5,6-benzo-7-α-naphthylamino-4′-bromofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-N-ethyl-N- (2-ethoxypropyl) amino -6-methyl-7-anilinofluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-7-methylfluoran, 3-diethylamino-7,8-benzfluoran, 3-diethylamino-6 Methyl-7-chlorofluoran, 3- (Np-tolyl-N-ethylamino) -6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 2 -{N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluoran, 2- {3,6'-bis (diethylamino) -9- (o-
Chloranilino) lactam lactam xanthylbenzoate, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluoran, 3-diethylamino-7- (o-chloroanilino) fluoran, 3-dibutylamino-7- (o -Chloroanilino) fluoran, 3-N-methyl-N-amylamino-6-methyl-7
-Anilinofluoran, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-N-ethyl-N -Tetrahydrofurfurylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluoran, 3-N-methyl-N-isobutyl-6-methyl-7-
Anilinofluoran, 3-N-ethyl-N-isoamyl-6-methyl-7-
Anilinofluoran, 3-diethylamino-6-methyl-7- (2 ', 4'-
Dimethylanilino) fluoran and the like.

In the present invention, various compounds having an electron accepting property as a developer, for example, a phenolic compound, a thiophenolic compound, a thiourea derivative, an organic acid and a metal salt thereof can be used in combination, if necessary. Shows a specific example.

4,4'-isopropylidenebisphenol, 4,4'-isopropylidenebis (o-methylphenol), 4,4'-secondary-butylidenebisphenol, 4,4'-isopropylidenebis (2-tert- Butylphenol), 4,4'-cyclohexylidenediphenol, 4,4'-isopropylidenebis (2-chlorophenol), 2,2'-methylenebis (4-methyl-6-tert-butylphenol), 2, 2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-butylidenebis (6-tert-butyl-butyl)
2-methylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-
Tert-butylphenyl) butane, 1,1,3-tris (2-methyl-4-hydroxy-5-
Cyclohexylphenyl) butane, 4,4'-thiobis (6-tert-butyl-2-methylphenol), 4,4'-diphenolsulfone, 4-isopropoxy-4'-hydroxydiphenylsulfone, 4-benzyl Oxy-4'-hydroxydiphenylsulfone, 4,4'-diphenolsulfoxide, isopropyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, benzyl protocatechuylate, stearyl gallate, lauryl gallate, octyl gallate, 1, 7-bis (4-hydroxyphenylthio) -3,5-dioxaheptane, 1,5-bis (4-hydroxyphenylthio) -3-oxapentane, 1,3-bis (4-hydroxyphenylthio)- Propane, 1,3-bis (4-hydroxyphenylthio) -2-hydroxypropane, N, N '-Diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, 1,5-bis (4-hydroxyphenylthio) -3-oxapentane, 1,3-bis (4-hydroxyphenylthio) -Propane, 1,3-bis (4-hydroxyphenylthio) -2-hydroxypropane, N, N'-diphenylthiourea, N, N'-di (m-chlorophenyl) thiourea, salicylanilide, 5-chloro Salicylanilide, 2-hydroxy-3-naphthoic acid, 2-hydroxy-1-naphthoic acid, 1-hydroxy-2-naphthoic acid, metal salts of hydroxynaphthoic acid such as zinc, aluminum and calcium; bis- (4- (Hydroxyphenyl) acetic acid methyl ester, bis- (4-hydroxyphenyl) acetic acid benzyl ester, 1,3-bis (4-hydroxycumyl) benze 1,4-bis (4-hydroxycumyl) benzene, 2,4'-diphenolsulfone, 3,3'-diallyl-4,4'-diphenolsulfone, α, α-bis (4-hydroxyphenyl ) -Α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetrabromobisphenol S, 3,4-dihydroxy-4'-methyldiphenylsulfone and the like.

Further, in order to provide the heat-sensitive recording material of the present invention, a crosslinking agent such as polyamide epichlorohydrin and glyoxal must be used in combination with the binder as necessary. As the binder, a polyvinyl alcohol-based binder is used. In addition, a very small amount of starch and its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / Acrylic acid ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide,
In addition to water-soluble polymers such as sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylate, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, Latexes such as an ethylene / vinyl acetate copolymer and a styrene / butadiene / acrylic copolymer can be used together as long as the essence of the present invention is not impaired.

As the filler, auxiliary additives commonly used in this type of heat-sensitive recording material, for example, calcium carbonate, silica, zinc oxide, titanium oxide, marine aluminum, zinc hydroxide,
In addition to inorganic fine powders such as barium sulfate, clay, talc, and surface-treated calcium and silica, organic fine powders such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin can be given. .

However, those having a particularly large specific surface area, those having a large oil-absorbing property, and those having a large moisture-absorbing property are not preferred because they lower the contact angle.

In addition, sensitizers, lubricants, waxes, surfactants, auxiliaries and the like generally used in the heat-sensitive coloring layer can be used as needed.

[Effects of the Invention] The heat-sensitive recording material of the present invention provides a highly practical heat-sensitive recording material that is excellent in background fog under high temperature and high humidity, discoloration of images, etc., and has little stickiness even when touched by wet hands. It is. [Examples] Next, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples. The parts and percentages shown below are based on weight.

Comparative Example 1 A mixture having the following composition was pulverized using a sand mill for 2 to 5 hours to prepare a solution [A] and a solution [B], respectively.

[A] solution 3-dibutylamino-6-methyl-7-anilinofluoran 20 parts 10% aqueous polyvinyl alcohol solution 20 parts water 60 parts [B] solution 1,5-bis (4-hydroxyphenylthio) -3- Oxapentane 10 parts Calcium carbonate 10 parts 10% aqueous polyvinyl alcohol solution 20 parts Water 60 parts Next, a heat-sensitive coating solution was prepared at a ratio of [A]: [B] = 1: 8, and a high-quality paper having a basis weight of 47 g / m ² was prepared. It was coated and dried so that the dry coating amount was 3.0 g / m ² . Further, a protective layer coating liquid [C] having the following composition was prepared, and was coated and dried so that the dry coating amount was 0.5 g / m ² .

[C] Liquid 20 parts of anhydrous silica fine particles 5 parts of zinc stearate 5 parts 10% aqueous solution of polyvinyl alcohol 25 parts 12.5% aqueous solution of polyamide epichlorohydrin 2 parts Water 48 parts The obtained heat-sensitive recording paper is calendered to prepare a heat-sensitive recording paper for comparison. Obtained.

Example 1 Comparative Example 1 was repeated in the same manner as in Comparative Example 1, except that a 12.5% aqueous solution of polyamide epichlorohydrin was mixed into the heat-sensitive coating solution at a ratio of 1/10 of the solution [B] and no protective layer was provided. The thermosensitive recording paper of the invention was obtained.

Example 2 In Example 1, except that an aqueous solution of a 21.5% ammonium salt of a diisobutylene maleic anhydride copolymer having a good film-forming property was added in the same amount as the solution [A] without adding a 12.5% aqueous solution of a polyamide epichlorohydrin crosslinking agent. In the same manner, a thermosensitive recording paper of the present invention was obtained.

Example 3 A thermosensitive recording paper of the present invention was obtained in the same manner as in Example 2, except that paraffin wax was used as a water repellent instead of the ammonium salt aqueous solution of diisobutylene maleic anhydride copolymer.

Comparative Example 2 A comparative thermosensitive recording paper was obtained in the same manner as in Comparative Example 1, except that the crosslinking agent of the solution [C] was not added.

Comparative Example 3 A thermosensitive recording paper for comparison was obtained in the same manner as in Example 1 except that no crosslinking agent was added.

Comparative Example 4 A thermosensitive recording paper of the present invention was obtained in the same manner as in Example 3, except that the amount of the paraffin wax was reduced to half.

Using the thermosensitive recording paper of the present invention obtained as described above and a thermosensitive recording paper for comparison, the following quality evaluations were obtained.
(1) Dynamic color development: Head power 0.45 W / dot, 1-line recording time 20 ms / l, scanning line density 8 × 3.85 dots / mm, using a thermal printing tester with a thin-film head manufactured by Matsushita Electronic Components Co., Ltd. Pulse width 0.2, 0.4, 0.6, 0.8, 1.0 msec
And the print density was measured with a Macbeth densitometer RD-914. (2) Moisture resistance: For the samples whose dynamic color development was measured in (1), those with a print density of 1.0 to 1.3
The density of the image area and the background area after standing for 24 hours in a 90% RH environment was measured.

(3) Stickiness test: The tip of the index finger was wetted with water, and the surface of the recording layer was lightly stroked to evaluate the distance.

(3) Contact angle: Water temperature using a contact angle meter manufactured by Kyowa Kagaku
The contact angle between the distilled water at 22 ° C. and the recording surface was measured.

As is clear from Tables 1 and 2, the heat-sensitive recording material of the present invention has better storability than the heat-sensitive recording paper for comparison.
In addition, it can be seen that dynamic spontaneity is excellent.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41M 5/30

Claims (1)

(57) [Claims] 1. A thermosensitive recording material comprising a support provided with a color-forming layer containing a leuco dye and a color developer as main components in a polyvinyl alcohol-based binder and having no protective layer.
A thermosensitive recording material characterized in that the contact angle between the recording surface and water is 60 ° or more by (TAPPI T458 os-70).