JPH0784100B2 - Thermal recording material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an improvement in a recording material using a leuco dye as a color former, and more particularly to an improvement in heat-sensitive recording.

[Prior art]

Recording materials using leuco dye have been known for a long time, and they are used as pressure-sensitive recording paper, heat-sensitive recording paper, and the like, and the usage thereof is increasing year by year.

The leuco heat-sensitive recording material is a leuco dye and a coloring agent supported on a support, and gives a colored image when an image signal is thermally applied by a minute heating resistor element.

Compared to other recording materials such as electrophotography and electrostatic recording materials, such thermal recording paper can be recorded in a short time with a relatively simple device without performing complicated processing such as development and definition. It is widely used because it can be obtained. Mainly used as a leuco dye for such a recording material,
Crystal violet lactone, a blue dye typified by leuco crystal violet, and a black dye typified by a 7-position anilino-substituted fluorane compound. In recent years, an optical character reading device and a label bar code reading device have been developed, and their use ratio is increasing. In these devices, a light emitting diode,
A light source having a light wavelength of 700 mμ or more using a semiconductor laser is generally used. However, since the above blue dye or black dye hardly absorbs light in the near infrared region of 700 mμ or more, the color reading cannot be performed by the reading device. Therefore, under the present circumstances, there is a strong demand for new development of a leuco dye having a light-absorbing wavelength of 700 mμ or more in a color former.

Conventionally, several proposals have been made for leuco dyes having long wavelength absorption. For example, JP-A-60-230890 discloses a styryl compound represented by the general formula (I). Has a long-wavelength light absorption ability and has a green-blue color tone, and although it can obtain a certain degree of contrast when used alone, it is still unsatisfactory.

〔Purpose〕

The present invention has light absorption in the near-infrared region, can be read by an optical character reader, a bar code reader using a semiconductor laser, and the like, and has a coloring color tone of black. The object is to provide a clear thermal recording material.

〔Constitution〕

According to the present invention, at least two color-forming layers are provided in a heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and a color-developing agent that causes the leuco dye to develop color when contacted with a color-developing layer.
Characterized in that at least one coloring layer containing a dye having absorption in the near infrared region of up to 900 nm and at least one coloring layer containing a dye having absorption in the visible light region are laminated. A thermal recording material is provided.

Examples of the dye having absorption in the near infrared region of 700 to 900 nm used in the present invention include compounds represented by the following general formula (I), and as the dye having absorption in the visible light region, the following general formula Examples thereof include compounds represented by (II).

(In the formula, R ₁ , R ₂ , R ₃ , and R ₄ are hydrogen or a substituted or unsubstituted alkyl group, R ₅ , R ₆ are hydrogen or a substituted or unsubstituted phenyl group, and R ₇ is a substituted or unsubstituted group. It is an alkyl group or a substituted or unsubstituted phenyl group.) (In the formula, R ₁ and R ₂ each independently represent a saturated or unsaturated hydrocarbon having 1 to 10 carbon atoms, and the hydrocarbon group may be cyclic or acyclic, and may contain an ether bond. R ₃ represents a hydrocarbon group having 1 to 2 carbon atoms or a halogen atom, and R ₄
Represents a hydrogen atom, a halogen atom, or a hydrocarbon group having 1 to 6 carbon atoms. ) Specific examples of the general formula compound include those shown below.

In addition, examples of the fluorane compound represented by the general formula (II) used in the present invention include, but are not limited to, those shown below.

3- (N-P-tolyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7- (m-trifluoromethylanilino) fluorane, 3-diethylamino -7- (o-chloroanilino) fluorane, 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-N-methyl-N-acylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-dimethylamino-6-methyl-7-anilinofluorane.

Further, as the color former used in the present invention, various electron-accepting compounds that cause the above leuco dye to develop color upon contact, or an oxidizing agent or the like is applied. Such substances are conventionally known, and specific examples thereof include inorganic acids, organic acids, phenolic substances, phenol resins and the like as shown below.

Bentonite, Zeolite, Acid White, Active White, Silica Gel, Aluminum Chloride, Salicylic Acid, 3-tert-Butylsalicylic Acid, 3,5-Di-tert-Butylsalicylic Acid,
Di-m-chlorophenyl thiourea, di-m-trifluoromethylphenyl thiourea, di-phenyl thiourea, salicylanilide, 4,4'-isopropylidene diphenol, 4,4'-isopropylidene bis (2-chloro Phenol), 4,4'-isopropylidene bis (2,6-dibromophenol), 4,4'-isopropylidene bis (2,6-di-chlorophenol), 4,4'-isopropylidene bis (2- Methylphenol), 4,4'-isopropylidenebis (2,6-dimethylphenol), 4,4'-isopropylidenebis (2-tert-butylphenol) 4,4'-sec
-Butylidene diphenol, 4,4'-cyclohexylidene bisphenol, 4,4'-cyclohexylidene bis (2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenol Sid, α-naphthol, β-naphthol, 3,5-xylenol, thymol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolak type phenol resin, 2,2′-thiobis (4,6-dichlorophenol) ), Catechol, resorcin, hydroquinone, pyrogallol, phloroglysin, phloroglysin carboxylic acid, 4-tert-octylcatechol, 2,2′-methylenebis (4-chlorophenol) 2,2′-methylenebis (4-methyl-6-) tert-butylphenol), 2,2 '
-Dihydroxydiphenyl, ethyl p-hydroxybenzoate, propyl p-hydroxybenzoate, butyl p-hydroxybenzoate, benzyl p-hydroxybenzoate,
p-Hydroxybenzoate-p-chlorobenzyl, p-hydroxybenzoate-o-chlorobenzyl, p-hydroxybenzoate-p-methylbenzyl, p-hydroxybenzoic acid-n-octyl, benzoic acid, 1-hydroxy- 2-
Naphthoic acid, 2-hydroxy-6-naphthoic acid, 4-hydroxydiphenyl sulfone, bis (4-hydroxy-)
3-t-butylphenyl) sulfone, 4-hydroxy-
4'-chlorodiphenyl sulfone, bis (4-hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, tartaric acid, oxalic acid, maleic acid, citric acid, succinic acid, stearic acid, 4-hydroxyphthalic acid, Boric acid, biimidazole, hexaphenylbiimidazole,
Carbon tetrabromide, etc.

In the present invention, when a leuco dye and a color former are bound and supported on a support to obtain a heat-sensitive recording material, various conventional binders can be appropriately used. Specific examples of such a binder include the followings.

Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxy cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, methyl cellulose, ethyl cellulose, sodium polyacrylate,
Polyvinylpyrrolidone, acrylic acid amide / acrylic acid esteryl copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobunalene / maleic anhydride copolymer alkali Water-soluble polymers such as salts, polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic ester, vinyl chloride / vinyl acetate copolymer Latexes such as polybutyl methacrylate, ethylene / vinyl acetate copolymer, styrene / butadiene / acrylic copolymer, and the like.

Further, in the present invention, if necessary, an auxiliary additive component commonly used in this type of heat-sensitive recording material, for example, a filler, a surfactant, a heat-fusible substance, a lubricant, a pressure color-developing preventing agent, etc. may be used in combination. You can In this case, examples of the filler include calcium carbonate, silica, titanium oxide, aluminum hydroxide, barium sulfate, clay, talc, inorganic fine powder such as surface-treated calcium and silica, urea-formalin resin, and styrene. / Methacrylic acid copolymer, organic fine powder such as polystyrene resin can be mentioned, and examples of the lubricant include higher fatty acids and metal salts thereof, higher fatty acid amides, higher fatty acid esters, animal-based, plant-based, mineral-based or Examples include various petroleum waxes.

The heat-sensitive recording material of the present invention is used in various fields like the conventional ones, and in particular, by utilizing its excellent near-infrared light absorption property, it can be used for optical literature readers and label bar coders. , It can be used as a recording material for reading the record of a barcode reader.

When the recording material of the present invention is used as a thermosensitive recording label sheet, a thermosensitive coloring layer containing the above-mentioned leuco dye and a coloring agent is provided on one surface of the support, and an adhesive is provided on the other surface of the support. It may have a structure in which a release mount is provided via a layer, and in this case, a protective layer such as a water-soluble resin layer is provided on the surface of the thermosensitive coloring layer in order to enhance image stability, if necessary. You can also

The leuco dye represented by the general formula (I) used in the present invention is obtained by reducing the carbonyl group of bis (p-disubstituted aminobenzal) acetone with a carbonyl reducing agent, for example, lithium aluminum hydride, and adding an acid such as perchloric acid. In addition, it is obtained by making a bis (p-disubstituted aminostyryl) carbenium salt, and then adding an organic sulfinic acid sodium salt to the salt and reacting the salt.

〔effect〕

The heat-sensitive recording material of the present invention is a combination of a leuco dye having absorption in the near infrared region of 700 to 900 nm and a dye having absorption in the visible light region, and these are contained in different layers. It has an absorption ability in the infrared region and has the advantage that the image can be read by an image reading device that uses a general-purpose semiconductor laser, and the obtained color image is black and has a high density. It is highly reliable.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples. All parts and% shown below are based on weight.

Example 1 Each liquid mixture having the following composition was dispersed by a sand glider for 1 to 2 hours to prepare liquids [A] to [C].

[Liquid A]

Bis (p-dimethylaminostyryl) -p-methylphenylsulfonyl methane 10 parts 10% polynivir alcohol aqueous solution 10 parts water 55 parts [solution B] 3- (N-methyl-N-cyclohexyl) amino-6-
Methyl-7-anilinofluorane 10 parts 10% polyvinyl alcohol aqueous solution 10 parts water 55 parts [C liquid] 4,4'-isopropylidenediphenol 20 parts calcium carbonate 15 parts 10% polyvinyl alcohol aqueous solution 35 parts water 130 parts above The mixed liquid having the composition is pulverized and dispersed by a sand glider for 2 to 4 hours, respectively, and the liquids A, B and C
Liquid] was prepared.

Further, [solution A] and [solution C] were mixed and stirred at a weight ratio of 1: 1 to prepare [solution D]. Similarly, [solution B] and [solution C]
Were mixed and stirred in a weight ratio of 1: 1 to prepare [solution E].

Next, [D liquid] was applied to a high-quality paper having a basis weight of 52 g / m ² and a dry weight of 1.05.
~ 1.5 g / m ² and then [Solution E] to a dry weight of 1.0-1.5 g / m ² and calender to give a Beck smoothness of 500-3000 seconds. A heat-sensitive recording material of the invention was prepared.

Example 2 In Example 1, [Solution E] was previously coated on a support so as to have a dry weight of 1.0 to 1.5 g / m ² , and then [Solution D].
A thermosensitive recording material was prepared in the same manner as in Example 1 except that the coating composition was applied to give a dry weight of 1.0 to 1.5 g / m ² .

Example 3 Bis (p-dimethylaminostyryl) -p-methylphenylsulfonylmethane of [Liquid A] of Example 1 was replaced with bis (p
A thermosensitive recording material was prepared in the same manner as in Example 1 except that -dimethylaminostyryl) -phenylsulfonylmethane (Specific Example No. (36)) was used instead.

Example 4 Bis (p-dimethylaminostyryl) -p-methylphenylsulfonylmethane of [Liquid A] of Example 1 was replaced with bis (p
A thermosensitive recording material was prepared in the same manner as in Example 1 except that -dimethylaminostyryl) -p-chlorophenylsulfonylmethane (Specific Example No. (5)) was used instead.

Example 5 The bis (p-dimethylaminostyryl) -p-methylphenylsulfonylmethane of [Liquid A] of Example 1 is a specific example N.
o It was prepared in the same manner as in Example 1 except that (8) was replaced.

Comparative Example 1 Only the solution (A solution) and the solution C of Example 1 which were mixed and stirred at a weight ratio of 1: 1 (corresponding to the solution D of Example 1) had a dry weight of 1.0 to 1.5. A thermal recording material was prepared in the same manner as in Example 1 except that the coating was carried out so that the coating amount was g / m ² .

Comparative Example 2 The above-mentioned [Solution A], [Solution B] and [Solution C] were mixed and stirred in a weight ratio of 1: 1: 2 to prepare a thermal liquid, and the basis weight was 52 g / m ^2.
A thermal recording material was prepared by coating a high-quality paper of 2.5 to 3.0 g / m ² on a dry basis and drying it, and then calendering it so that the Bekk smoothness was 500 to 3000 seconds.

With respect to the thermosensitive recording material obtained as described above, the maximum color density and the PCS value at a wavelength of 900 mm were measured. The results are shown in Table-1.

Maximum color density: 110 ° C, 2kg / c with Toyo Seiki thermal inclinometer
Printing was performed at m ^{2 for} 1 second, and the density was measured with a Macbeth densitometer RD-514 (filter W-106).

PCS value: The reflectance of the printed part and the background at a wavelength of 900 nm is HITACH
The measurement was performed with an I303 type spectrophotometer, and the PCS value was calculated by the following formula.

As is clear from the results in Table 1, the thermosensitive recording material of the present invention exhibits a black or green-black color tone, is excellent in its maximum color density, and has a high PCS value at a wavelength of 900 nm.

Claims (3)

[Claims] 1. A heat-sensitive recording material utilizing a color-forming reaction between a leuco dye and a color-developing agent which causes the leuco dye to develop a color upon contact, wherein at least two color-forming layers are provided and 700 to 900 are provided.
A heat-sensitive material characterized by laminating at least one coloring layer containing a dye having absorption in the near-infrared region of nm, and further at least one coloring layer containing a dye having absorption in the visible light region. Recording material. 2. A heat-sensitive recording material according to claim 1, wherein the leuco dye having absorption in the near infrared region of 700 to 900 nm is represented by the following general formula (I). (In the formula, R ₁ , R ₂ , R ₃ , and R ₄ are hydrogen or a substituted or unsubstituted alkyl group, R ₅ , R ₆ are hydrogen or a substituted or unsubstituted phenyl group, and R ₇ is a substituted or unsubstituted group. It is an alkyl group or a substituted or unsubstituted phenyl group. 3. The heat-sensitive recording material according to claim 1, wherein the leuco dye having absorption in the visible light region is represented by the following general formula (II). (In the formula, R ₁ and R ₂ each independently represent a saturated or unsaturated hydrocarbon having 1 to 10 carbon atoms, and the hydrocarbon group may be cyclic or acyclic, and may contain an ether bond. R ₃ represents a hydrocarbon group having 1 to 2 carbon atoms or a halogen atom, and R ₄
Represents a hydrogen atom, a halogen atom, or a hydrocarbon group having 1 to 6 carbon atoms. )