JPH0767861B2 - Thermal recording material - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a recording material using a leuco dye as a color former.

[Prior art]

Recording materials using leuco dyes have long been known,
It is used as pressure-sensitive recording paper, heat-sensitive recording paper, and the like, and its usage 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.

Such a heat-sensitive recording paper can be recorded in a short time with a relatively simple device without performing complicated processing such as development and fixing as compared with other recording materials such as electrophotography and electrostatic recording materials. 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, optical literary readers and label bar code readers have been developed and their use rate is increasing. In these devices, the light wavelength using a light emitting diode or a semiconductor laser is 700 nm as a light source. The above light sources are generally used. However, since the blue dye and the black dye hardly absorb light in the near infrared region of 700 nm or more, the color image cannot be read by the reading device. Therefore, under the present circumstances, there is a strong demand for new development of leuco dyes having a light-absorbing wavelength of 70 nm or more for color formers.

〔Purpose〕

The present invention uses a specific leuco dye having light absorption in the near-infrared region to enable reading with an optical character reader, a bar code reader using a semiconductor laser, etc., and fading of a colored image. The object is to provide a sensation recording material that is less and has no background fog.

〔Constitution〕

According to the present invention, in a 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, at least one of the leuco dyes is represented by the following general formula (I). Provided is a thermosensitive recording material, which is a compound, wherein at least one of the above-mentioned color developing agents is a compound represented by the following general formula (II).

(In the formula, R ₁ , R ₂ , R ₃ and R ₄ represent an alkyl group, R ₅ and R ₆ represent a hydrogen atom, and R ₇ represents a substituted or unsubstituted phenyl group.) (In the formula, X ₁ , X ₂ , X ₃ and X ₄ represent a hydrogen atom.) Specific examples of the compound represented by the general formula (I) include those shown below.

In the present invention, the leuco dye represented by the general formula (I) can be used in combination with other leuco dyes. As the leuco dye used in this case, the leuco dyes generally known in this type of leuco recording material can be used. A dye is used. For example, a leuco compound such as a triphenylmethane-based, fluorane-based, phenothiazine-based, auramine-based, spiropyran-based, indolinophtalide-based dye is preferably used. Specific examples of such leuco dyes include, for example,
The following may be mentioned.

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-chlorofurfuride Oran, 3-dimethylamino-5,7-dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino -6-Methyl-7-chlorofluorane, 3- (Np-tolyl-N-ethylamino) -6-methyl- -Anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2-N- {3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3,6- Bis (diethylamino) -9- (o-chloroanilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane , 3-dibutylamino-7- (o-chloroanilino) fluorane, 3-N-methyl-N-amylamino-6-methyl-7-
Anilinofluorane, 3-N-methyl-N-cyclohexylamino-6-methyl-7-anilinofluorane, 3-diethylamino-6-methyl-7-anilinofluorane, 3- (N, N-diethylamino) ) -5-Methyl-7- (N, N
-Dibenzylamino) fluorane, benzoyl leuco methylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrrolispirane, 6'-bromo-3'-methoxy-benzoindolino-pyrrolispirane, 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) fluorane, 3-pyrrolidino-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7- (N -Benzyl-trifluoromethylanilino) fluorane, 3-pyrrolidino-7- (di-p-chlorophenyl) methylaminofluorane, 3-diethylamino-5-chloro-7- (α-phenylethylamino) fluorane, 3 -(N-ethyl-p-toluidino) -7- (α-phenylethylamino) fluorane, 3-diethylamino-7- (o-methoxycarbolylphenylamino) fluorane, 3-diethylamino-5-methyl-7- ( α-phenylethylamino) fluorane, 3-diethylamino-7-piperidi Fluoran, 2-chloro-3-(N-Mechirutoruijino)-7-(p
-N-butylanilino) fluorane, 3- (N-benzyl-N-cyclohexylamino) -5,
6-benzo-7-α-naphthylamino-4′-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluorane, In the present invention, the above-mentioned color developing agent is used, but other color developing agents can be used in combination if necessary. Various electron-accepting compounds that cause the leuco dye to develop a color upon contact, or oxidizing agents are applied. Such substances are conventionally known, and specific examples thereof include the following inorganic acids, organic acids, phenolic substances, and phenol resins.

Bentonite, zeolite, acid clay, activated clay, 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-chlorophenol) ), 4,4′-isopropylidene bis (2,6-dibromophenol), (4,4 ′ isopropylidene bis (2,6-dichlorophenol), 4,4′-isopropylidene bis (2-methylphenol) , 4,4'-isopropylidene bis (2,6-dimethylphenol), 4,4'-isopropylidene bis (2-tert-butylphenol), 4,4'-s
ec-Butylidene diphenol, 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, 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, diuric 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 ester copolymer, acrylic acid amide / acrylic acid ester / methacrylic acid terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / 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-preventing agent, etc. may be used in combination. You can In this case, as the filler, for example,
Inorganic fine powder such as calcium carbonate, silica, titanium oxide, aluminum hydroxide, barium sulfate, clay, talc, surface-treated calcium and silica, urea-formalin resin, styrene / methacrylic acid copolymer, polystyrene resin Examples of the heat-fusible substance include higher fatty acids or their esters, amides (including their methylol compounds) or metal salts, various waxes, and dimethyl terephthalate. , Condensates of aromatic carboxylic acids and amines, benzoic acid phenyl esters, higher linear glycols, dialkyl 3,4-epoxy-hexahydrophthalates, higher ketones, and other heat-fusible organic compounds. , And if necessary,
An undercoat layer made of a filler or a water-soluble binder may be provided between the support and the thermosensitive color developing layer.

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 forming a bis (p-disubstituted aminostyryl) carbenium salt, and then adding an organic sulfinic acid sodium salt to the salt and reacting the salt.

〔effect〕

Since the heat-sensitive recording material of the present invention uses the special leuco dye represented by the general formula (I), this color image has absorption in the near-infrared region, and image reading using a general-purpose semiconductor laser is carried out. It has the advantage that the image can be read by the device, and is applied to various fields. further,
Since the compound represented by the general formula (II) is used as a color-developing agent, it has less image fading and less background fog.

〔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 Liquids [A] to [C] were prepared by dispersing each mixed liquid having the following composition by a sand glider for 2 to 4 hours.

[A liquid]

Bis (p-dimethylaminostyryl) -p-methylphenylsulfonylmethane 10 parts 10% polynivir alcohol aqueous solution 10 parts water 55 parts [B solution] 3- (N-methyl-N-cyclohexyl) amino-6-
Methyl-7-anilinofluorane 10 parts 10% polynivir alcohol aqueous solution 10 parts water 55 parts [C liquid] 1,1-bis (4-hydroxyphenyl) cyclohexane 3
0 parts Calcium carbonate 30 parts 10% polyvinyl alcohol aqueous solution 60 parts Water 180 parts Next, [solution A] and [solution C] were mixed and stirred in a weight ratio of 1: 1 to prepare a heat-sensitive coating solution. The basis weight of this coating solution is 52
The heat-sensitive recording of the present invention was carried out by applying a dry weight of 4 to 5 kg / m ² on a high-quality paper of g / m ² and drying it, and then calendering it so that the Beck smoothness was 500 to 3000 seconds. Created the material.

Example 2 In Example 1, the solution [B] was further used, and [A]
Liquid]: [B liquid]: [C liquid] were mixed in a weight ratio of 1: 1: 2 to prepare a heat-sensitive recording material of the present invention in the same manner as in Example 1.

Example 3 An example except that bis (p-dimethylaminostyryl) -P-methylphenylsulfonylmethane in [Liquid A] was replaced with bis (p-dimethylaminostyryl) -P-phenylsulfonylmethane in Example 1. A thermal recording material of the present invention was prepared in the same manner as in 1.

Comparative Examples 1-2 Same as Examples 1-2 except that 1,1-bis (4-hydroxyphenyl) cyclohexane of [C liquid] in Examples 1-2 was replaced with 4,4'-dihydroxyphenyl sulfone. To prepare a thermal recording material for comparison.

The above four kinds of heat-sensitive recording materials were tested for image fading and background fog. The results are shown in Table-1. The test method was as follows.

Image fading and background fog ... Head power 0.37 in a thermal printing tester with a thin film head manufactured by Matsushita Electronic Components Co., Ltd.
W / dot, 1 line recording time 5ms /, scanning line density 8 × 3.
The pulse width is printed at 1.0 msec under the condition of 85 dots / mm.
After standing at 90 ° C and 90% RH for 24 hours, the reflectance of the image part and the background part at a wavelength of 900 nm was measured by a HITACHI 303 type spectrophotometer.

PCS value …… The PCS value was calculated by the following formula.

As is clear from Table 1, the thermal recording material of the present invention has a higher PCS value at a wavelength of 900 nm, less image fading, and less background fog than the comparative examples.

Claims (1)

[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 color upon contact, wherein at least one of the leuco dyes is represented by the following general formula (I). A heat-sensitive recording material, characterized in that at least one of the above-mentioned color developing agents is a compound represented by the following general formula (II). (In the formula, R ₁ , R ₂ , R ₃ and R ₄ represent an alkyl group, R ₅ and R ₆ represent a hydrogen atom, and R ₇ represents a substituted or unsubstituted phenyl group.) (In the formula, X ₁ , X ₂ , X ₃ and X ₄ represent a hydrogen atom.)