JP2564574B2 - New leuco dye - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel leuco dye for image formation, and particularly to a near-infrared absorbing leuco dye in heat-sensitive recording and pressure-sensitive recording.

[Prior art]

Recording materials using leuco dyes have been known for a long time, and in recent years, they have been widely used as pressure-sensitive recording paper and heat-sensitive recording paper. Examples of commonly used leuco dyes include triphenylmethane type, fluorane type, phenothiazine type, auramine type and the like. These dyes have various color tones and are properly used depending on the application. However, many of these dyes have been developed for the purpose of color tone, that is, absorption in the visible region, and dyes having absorption in the near-infrared region, that is, 700 nm to 1000 nm range have hardly been developed. Is the current situation. recent years,
With the widespread use of semiconductor lasers, there is a movement to read recorded images such as barcodes with semiconductor lasers, and thermal paper and pressure-sensitive paper are required to have absorption in the near infrared region. It was

Several proposals have recently been made for leuco dyes having absorption in the near infrared region. For example, JP-A-51-121035, JP-A-51-121037, JP-A-51-121038 and JP-A-57-16
No. 7979 and JP-A-58-157779, monovinyl- or divinyl-containing phthalide compounds, JP-A-59-1997.
57 and fluorene compounds as disclosed in JP-A-60-226871. However, these compounds
Although it has absorption in the near-infrared region, it has drawbacks that it does not reach a sufficient absorption intensity, the stability of the dye is inferior, the image is easily erased, and the manufacturing cost is high.

Further, JP-A-60-231766 proposes a novel near-infrared absorbing leuco dye. Although this dye has a strong absorption in the near-infrared, it does not have sufficient storage stability. It has disadvantages such as poor light resistance stability, coloration of the background portion, and reduced absorption in the near infrared region. Therefore, in reality, no satisfactory near-infrared absorbing dye has been found at present.

〔Purpose〕

It is an object of the present invention to provide a novel leuco dye having strong absorption in the near infrared region and excellent storage stability. More specifically, it has a wide and strong absorption from 600 nm to 1000 nm, and when used as a leuco dye for heat-sensitive or pressure-sensitive paper, it can be read with a light source from the visible region to the near-infrared region and the dye image light resistance It is an object of the present invention to provide a novel leuco dye excellent in stability.

〔Constitution〕

According to the present invention, a novel leuco dye represented by the following general formula (I) is provided.

In the formula, R ₁ , R ₂ , R ₃ and R ₄ are lower alkyl groups, and R ₅ is (N is an integer of 1 to 8) or (M is an integer of 0 to 2, R ₈ is a substituted or unsubstituted phenyl group) and R ₆ or R ₇ is a hydrogen atom or a lower alkyl group.

The leuco dye represented by the general formula (I) of the present invention is a novel substance which is a white or pale yellow crystalline powder which is stable in the air and has a strong absorption in the near infrared region of 600 to 1000 nm. When contacted with an inorganic acid such as acid clay or activated clay, or an electron-accepting compound (that is, a color former) such as an organic acid, a phenolic compound, or a phenolic resin at a molecular level, a color-developing reaction occurs quickly and a green color is obtained. It forms a blue to blue dye, and this dye that develops color has excellent storage stability and is therefore useful as a dye precursor.

The leuco dye represented by the general formula (I) of the present invention can generally be easily synthesized according to the following reaction formula.

(X ⁻ in the reaction formula represents an anion such as halogen or perchloric acid.) This reaction can be carried out simply by heating in a mixed solvent of methanol / acetic acid. The method for producing the compound (II) in the reaction formula is described in, for example, Annalen der Chem.
ie, 623, p. 204 (1959).

The lower alkyl group represented by R _{1 to} R ₄ and R _{6 to} R _{7 in} the general formula (I) of the present invention is usually a linear or branched alkyl group having 1 to 4 carbon atoms.

Specific examples of the compound represented by the general formula (I) include the following.

[Specific Examples of Compounds of General Formula (I)] The leuco dye of the present invention, like the conventional leuco dye,
It can be used as a color former in recording materials such as pressure-sensitive recording materials, heat-sensitive recording materials, and thermal transfer recording materials.

When the leuco dye of the present invention is used as a pressure-sensitive recording material, it can be prepared by a method described in, for example, US Pat. No. 2,800,457. The main physical properties required for the leuco dye in this case are oil solubility, color developing properties with a color developing agent, storage stability of the dye image, and the like, and are selected in consideration of these physical properties.

When the leuco dye of the present invention is used as a heat-sensitive recording material, it can be prepared by a method described in, for example, Japanese Patent Publication No. 45-14039. In this case, the main physical properties required for the leuco dye include thermal color development properties, background whiteness, storage stability of the leuco dye and its color forming dye, and these are selected in consideration of these physical properties.

In any case, it is important to make full use of the characteristic that the image of the leuco dye of the present invention has a sufficient absorption characteristic in the near infrared region.

When the leuco dye of the present invention is used as a recording material, it can be used in combination with other leuco dyes. That is, the color tone of the leuco dye of the present invention is green or blue, but it can be used in combination with other leuco dyes for the purpose of color tone correction or absorption characteristic correction. As the leuco dye used in this case, a leuco dye generally known in this type of leuco recording material is used, and specific examples of such a leuco dye include, for example, those shown below. No.

3,3-bis (p-dimethylaminophenyl) -phthalide, 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6- Diethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) -6-chlorophthalide, 3,3-bis (p-dibutylaminophenyl) phthalide, 3-cyclohexylamino-6-chlorofluorane, 3-dimethylamino -5,7-Dimethylfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-7-methylfluorane, 3-diethylamino-7,8-benzfluorane, 3-diethylamino-6-methyl-7 -Chlorfluorane, 3- (Np-tolyl-N-ethylamino) -6-methyl-7-anilinofluorane, 3-pyrrolidino 6-Methyl-7-anilinofluorane, 2- {N- (3'-trifluoromethylphenyl) amino} -6-diethylaminofluorane, 2- {3,6-bis (diethylamino) -9- (o -Chloranilino) xanthylbenzoic acid lactam}, 3-diethylamino-6-methyl-7- (m-trichloromethylanilino) fluorane, 3-diethylamino-7- (o-chloroanilino) fluorane, 3-dibutylamino-7- ( o-chloranilino) 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-
Pyrirospirane, 6'-bromo-3'-methoxy-benzoindolino-
Pyrirospirane, 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-methoxycarbonylphenylamino) fluorane, 3-diethylamino-5-methyl-7- (α -Phenylethylamino) fluorane, 3-diethylamino-7-piperidi Fluoran, 2-chloro-3-(N-Mechirutoruijino) -7-
(Pn-butylanilino) fluoran, 3- (N-benzyl-N-cyclohexylamino)-
5,6-benzo-7-α-naphthylamino-4′-bromofluorane, 3-diethylamino-6-methyl-7-mesitidino-
4 ', 5'-benzofluorane and the like.

Further, as the colorant used when a recording material is obtained by using the leuco dye of the present invention, various electron-accepting compounds that cause the leuco dye to develop color upon contact, or an oxidizing agent or the like is applied. Such a material is conventionally known, and specific examples thereof include the following.

Bentonite, zeolite, acid clay, activated clay, silica gel, zinc oxide, zinc chloride, zinc bromide, aluminum chloride, salicylic acid, 3-tert-butylsalicylic acid, 3,
5-di-tert-butylsalicylic acid, di-m-chlorophenylthiourea, di-m-trifluoromethylphenylthiourea, di-phenylthiourea, salicylanilide, 4,
4'-isopropylidene diphenol, 4,4'-isopropylidenebis (2-chlorophenol), 4,4'-isopropylidenebis (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-t
ert-butylphenol), 4,4'-sec-butylidene dipheceal, 4,4'-cyclohexylidenebisphenol, 4,4'-cyclohexylidenebis (2-methylphenol), 4-tert-butyl Phenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, dimethyl 5-hydroxyphthalate, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, Ovolak-type phenol resin,
2,2'-thiobis (4,6-dichlorophenol), catechol, resorcin, hydroquinone, pyrogallol, phloroglysin, phloroglysincarboxylic 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-hydroxybenzoic acid- p-chlorobenzyl, p-hydroxybenzoic acid-o-chlorobenzyl, p-hydroxybenzoic acid-p
-Methylbenzyl, p-hydroxybenzoic acid-n-octyl, benzoic acid, zinc salicylate, 1-hydroxy-2
-Naphthoic acid, 2-hydroxy-6-naphthoic acid, 2-
Zinc hydroxy-6-naphthoate, 4-hydroxydiphenyl sulfone, 4,2'-diphenol sulfone, 4-
Hydroxy-4'-chlorodiphenyl sulfone, 4-hydroxy-4'-benzyloxydiphenyl sulfone, 4
-Hydroxy-4'-isopropoxydiphenyl sulfone, 4-hydroxy-4'-isobutyloxydiphenyl sulfone, bis (4-hydroxyphenyl) sulfide, 2-hydroxy-p-toluic acid, 3,5-di-tert.
-Zinc butyl salicylate, 3,5-di-tert-butyl tin salicylate, tartaric acid, oxalic acid, maleic acid, citric acid,
Succinic acid, stearic acid, 4-hydroxyphthalic acid, boric acid, biimidazole, hexaphenylbiimidazole, carbon bromide, methylenebis- (oxyethylenethio) diphenol, ethylenebis- (oxyethylenethio) diphenol, bis -(4-hydroxyphenylthioethyl) ketone, bis- (4-hydroxyphenylthioethyl) ether, m-xylylenebis (4-hydroxyphenylthio) ether and the like.

In order to obtain a pressure-sensitive recording material using the leuco dye of the present invention, first, 1 to 4% of the leuco dye is dissolved in an alkylnaphthalene-based or terphenyl-based oil, and a resin such as gelatin is usually cured to about 5 μm. Create microcapsules. The microcapsules are coated on a support such as paper or plastic film using a binder to obtain a color former sheet. The microencapsulation in this case is for example
It can be carried out by a conventionally known method such as the method described in USP 2800457. On the other hand, the color developing agent sheet is
The coloring agent is prepared by dispersing or dissolving it in water or an organic solvent using an appropriate dispersant, adding a binder if necessary, and coating it on a support such as paper.

In order to obtain a heat-sensitive recording material using the leuco dye of the present invention, each of the leuco dye and the color former is dispersed with a water-soluble resin or the like, the dispersion is mixed with an appropriate binder, and the mixture is used for paper or the like. It is coated on the support. In this case, the leuco dye preferably has a particle size of about 0.5 to 5 μm.
The weight ratio of the leuco dye to the color former is suitably about 1: 1 to 1: 5. The color-developing layer may be coated in one layer or in two or more layers, or may be separately coated in a leuco dye layer and a color former layer. Further, an undercoat layer or a protective layer may be provided as is known in the heat-sensitive recording material.

Further, in order to obtain a thermal transfer type recording material using the leuco dye of the present invention, the leuco dye is dispersed or dissolved in water or a solvent, and a transfer sheet is prepared by applying it to a heat resistant support such as a polyester film, On the other hand, a color developing agent is dispersed or dissolved in water or a solvent and coated on a support to prepare a receiving sheet.

When a leuco dye and a color former are bound and supported on a support in order to obtain a heat-sensitive recording material, various conventional binders can be appropriately used, and in order to obtain a pressure-sensitive recording material, When the encapsulated leuco dye is supported on the support or the color former is supported on the support, various commonly used binders can be appropriately used. Specific examples of such a binder include the followings.

Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylamide / acrylic acid ester copolymer, acrylamide / acrylic acid ester / methacrylic acid Terpolymer, styrene / maleic anhydride copolymer alkali salt, isobutylene / maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, casein and other water-soluble polymers, polyvinyl acetate, Polyurethane, styrene / butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride / vinyl acetate copolymer, polybutyl methacrylate, ethylene / Vinyl copolymer acid, styrene / butadiene / acrylic copolymer latex such as such.

In addition, if necessary, auxiliary additive components commonly used for pressure-sensitive and heat-sensitive recording materials of this type, for example, fillers, surfactants,
A heat-fusible substance, a lubricant, a pressure coloring inhibitor, and the like can be used in combination. In this case, as the filler, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc,
Inorganic fine powders such as surface-treated calcium and silica, as well as organic fine powders such as urea-formalin resin, styrene / methacrylic acid copolymer, and polystyrene resin can be mentioned. As the lubricant, higher fatty acid can be used. And its metal salts, higher fatty acid amides, higher fatty acid esters, animal-based,
Examples thereof include various vegetable, mineral and petroleum waxes.

The recording material obtained by using the leuco dye 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 is possible to read an optical character. It can be used as a recording material for a device, a label bar coder, and a bar code reader.

When the recording material obtained by using the leuco dye 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 the support is provided. It may have a structure in which a release mount is provided on the other surface of the body via an adhesive layer.

〔effect〕

The novel leuco dye represented by the general color [I] of the present invention has a strong absorption ability in the near infrared region over 600 to 1000 nm. Therefore, the heat-sensitive and pressure-sensitive recording materials obtained by using the leuco dye can be read with a light source from the visible region to the near-infrared region, and the dye image is excellent in storage stability, particularly in heat resistance. As a result, the image can be sufficiently read by an image reading device using a semiconductor laser or the like as a light source not only under daily environmental conditions but also under exposure conditions such as sunlight and fluorescent light.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 Bis (p-dimethylaminostyryl) -p-benzyloxyphenylsulfonylmethane [Specific Example of Compound No.
Synthesis of (1)] Bis (p-dimethylaminostyryl) carbenium perchlorate (2.8 g) and acetic acid (1.9 g) were added to methanol (80 cc), and p-benzyloxyphenylsulfinate sodium 4.
A solution of 80 g of 7 g of methanol was dropped and the mixture was heated under reflux for 1 hour. The resulting precipitate was collected by filtration and recrystallized from a mixed solvent of benzene and hexane to give pale yellow crystals (melting point 188-191 ° C) 3.8g
I got

The elemental analysis values of this compound are as follows, and
The structure was confirmed by the analysis result of NMR spectrum.

Example 2 A compound of Compound Specific Example No (2) was obtained in the same manner as in Example 1 except that p-anisole sodium sulfinate was used instead of p-benzyloxyphenyl sulfinic acid sodium in Example 1. . The melting point of this compound is 12
The temperature was 9 to 130 ° C.

Example 3 In the same manner as in Example 1 except that sodium p-butoxyphenylsulfinate was used in place of sodium p-benzyloxyphenylsulfinate in Example 1, a compound of Compound No. (4) was obtained. It was The melting point of this compound was 182.7 ° C.

Example 4 A compound of Specific Example No. (5) in the same manner as in Example 1 except that sodium p-octyloxysulfinate was used instead of sodium bis (p-benzyloxyphenylsulfinate) in Example 1. The melting point of this compound was 153.4 ° C.

Example 5 A compound of Compound No. (6) in the same manner as in Example 1 except that sodium 4-methylbenzyloxyphenylsulfinate was used instead of sodium p-benzyloxyphenylsulfinate in Example 1. Got The melting point of this compound was 169.1 ° C.

Example 6 Instead of bis (p-dimethylaminostyryl) carbenium perchlorate in Example 1, bis (p-cyethylaminostyryl) carbenium perchlorate was used,
A compound of Specific Example No. (8) was obtained in the same manner as in Example 1 except that p-anisole sodium sulfinate was used instead of p-benzyloxyphenyl sulfinic acid sodium. The melting point of this compound was 163 ° C.

Example 7 Example 5 was repeated except that bis (4-dimethylamino-2-methylstyryl) carbenium perchlorate was used instead of bis (p-diethylaminostyryl) carbenium perchlorate in Example 6. Similarly, the compound of Compound Example No. (10) was obtained. The melting point of this compound is 95 ° C.
Met.

Application Examples 1 to 5 and Comparative Examples 1 to 3 Mixtures having the following compositions were dispersed by a ball mill to prepare solutions [A] and [B].

[Liquid A]

Leuco dye in Table 2 10 parts Polyvinyl alcohol 10% aqueous solution 10 parts Water 30 parts [Solution B] Stearic acid amide 20 parts Calcium carbonate 20 parts 4,4'-diphenol sulfone 30 parts Polyvinyl alcohol 10% aqueous solution 35 parts Water 210 parts [Solution A] and [Solution B] obtained as above
A coating liquid was prepared by mixing at a ratio of 1, and the coating liquid was coated on high-quality paper so that the dry solid content of the leuco dye was 0.6 g / m ^2, and dried to obtain a heat-sensitive recording material.

This was solid printed with a commercially available facsimile refax 130 and the quality was measured. The measurement results are shown in Table-1.

The density is Macbeth densitometer 914, the filter is Kod
It was measured using ak Ratten No106. The PCS value was obtained by measuring the absorbance with a reflection spectrophotometer (Hitachi 330), converting the absorbance into reflectance, and using the following formula.

The light fastness test results show the density after the recorded image was exposed at 5000 lux for 1 week.

As is clear from Table 1, the recording material using the leuco dye of the present invention exhibits a sufficiently strong absorption in the near infrared region, that is, in the range of 600 to 1,000 nm, and also has a light resistance stability of the background part. It can be seen that it is excellent and has sufficient quality as a recording material.

[Brief description of drawings]

The drawing shows the NMR of the leuco dye obtained in Example 1 of the present invention.
It is a spectrum.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Kaoru Kodera 1-2-2 Dojima, Kita-ku, Osaka-shi, Osaka Prefecture Showa Kako Co., Ltd. (72) Osamu Miyazaki 1-2-2 Dojima, Kita-ku, Osaka-shi, Osaka No. 2 Showa Kako Co., Ltd. (56) Reference JP-A-60-231766 (JP, A) JP-A-60-230890 (JP, A)

Claims (1)

(57) [Claims] 1. A general formula [In the formula, R ₁ , R ₂ , R ₃ and R ₄ are lower alkyl groups, and R ₅ is (N is an integer of 1 to 8) or (M is an integer of 0 to 2, R ₈ is a substituted or unsubstituted phenyl group), and R ₆ or R ₇ is a hydrogen atom or a lower alkyl group. ] The novel leuco dye represented by these.