JPH0435353B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to improvements in recording materials using leuco dyes as color formers, and in particular to improvements in heat-sensitive and pressure-sensitive recording. [Prior Art] Recording materials using leuco dyes have been known for a long time and are used as pressure-sensitive recording paper, heat-sensitive recording paper, etc., and their usage is increasing year by year. Leuco-based pressure-sensitive recording materials generally utilize a chemical reaction between a nearly colorless leuco dye and a coloring agent that causes the leuco dye to develop color upon contact to form a colored image. Specifically, a coloring agent sheet coated with a microcapsule solution of leuco dye in an organic solvent and a coloring agent sheet coated with a coloring agent and a binder are placed one on top of the other, and the two sheets are coated from the back side. The pressure capsule is destroyed by the pressure of a pen, etc., and a color reaction occurs. On the other hand, leuco-based thermosensitive recording materials have
It supports a leuco dye and a coloring agent, and when an image signal is thermally applied using a micro-heating resistor element, a colored image is generated. Such pressure-sensitive and heat-sensitive recording papers have advantages over other recording materials, such as electrophotographic and electrostatic recording materials.
It is used in many fields because it allows recording to be obtained in a short time with a relatively simple device without complicated processes such as development and fixing. The leuco dyes mainly used in such recording materials include blue dyes such as crystal violet lactone and leuco crystal violet, and black dyes such as fluoran compounds substituted with anilino at the 7-position. be. In recent years, optical character reading devices and label barcode reading devices have been developed, and their usage is increasing, but these devices use light-emitting diodes or semiconductor lasers as light sources with light wavelengths of 700 mμ. The above light sources are commonly used. However, the above-mentioned blue dye and black dye hardly absorb light in the near-infrared region of 700 mμ or more, so it is impossible to read the color with the above-mentioned reading device. Therefore, there is currently a strong demand for the development of new leuco dyes whose color formers have a light absorption wavelength of 700 mμ or more. In the past, several proposals have been made regarding leuco dyes that absorb at long wavelengths.
No. 121035, JP-A No. 121037, JP-A-51-
No. 121038 and Japanese Unexamined Patent Publication No. 167979/1983, these dyes have the drawbacks of being difficult to synthesize and very expensive. [Purpose] The present invention uses a new leuco dye that absorbs light in the near-infrared region to provide a recording material that can be read by an optical character reader or a barcode reader using a semiconductor laser. The purpose is to provide. [Structure] According to the present invention, in a recording material that utilizes a coloring reaction between a leuco dye and a coloring agent that causes the leuco dye to develop color upon contact, at least one of the leuco dyes is represented by the following general formula. A recording material is provided which is characterized in that it is a compound. (In the formula, R ₁ , R ₂ , R ₃ , R ₄ are hydrogen or an alkyl group, R ₅ and R ₆ are hydrogen, a phenyl group or a phenyl group substituted with an amino group or a dialkylamino group, and R ₇ is a phenyl group. or a phenyl group substituted with an alkyl group) The leuco dye represented by the above general formula used in the present invention is usually pale yellow, and the color tone is greenish-blue, so sufficient contrast can be obtained even when used alone. ,
It is also possible to use other leuco dyes in combination to adjust the color tone. Specific examples of the compounds of the above general formula include those shown below. In the present invention, the leuco dye represented by the above general formula can be used in combination with other leuco dyes. Dyes are used, and for example, leuco compounds of triphenylmethane-based, fluoran-based, phenothiazine-based, auramine-based, and spiropyran-based dyes are preferably used. Specific examples of such leuco dyes include those shown below. 3,3-bis(p-dimethylaminophenyl)
-phthalide, tris-(p-dimethylaminophenyl)methane 3,3-bis(p-dimethylphenyl)-6-
Dimethylaminophthalide (also known as crystal violet lactone), 3,3-bis(p-dimethylaminophenyl)
-6-diethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)
-6-chlorphthalide, 3,3-bis(p-dimethylaminophenyl)
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-chlorofluorane, 3-(N-p-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-chloroanilino)xantylbenzoic acid lactam}, 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- 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, benzoylleucomethylene blue, 6'-chloro-8'-methoxy-benzoindolino-pyrylospirane, 6'-bromo-3'-methoxy-benzoindolino-pyrylospirane, 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'-hydroxy-4'-dimethylaminophenyl)-3-(2'-hydroxy-4'-chloro-
5'-methylphenyl)phthalide, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidine-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)fluoran, 3-(N-ethyl-p-toluidino)-7-(α
-phenylethylamino)fluoran, 3-diethylamino-7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-
phenylethylamino)fluorane, 3-diethylamino-7-piperidinofluorane, 2-chloro-3-(N-methyltoluidino)-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, etc. Further, as the coloring agent used in combination with the leuco dye in the present invention, various electron-accepting compounds or oxidizing agents that cause the leuco dye to develop color upon contact are applicable. Such substances are conventionally known, and specific examples thereof include inorganic acids, organic acids, phenolic substances, phenolic resins, etc. as shown below. 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'-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'-sec-butylidene diphenol, 4,4'-cyclohexylidene bisphenol, 4,4'-cyclohexylidene bis(2-methylphenol), 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α-naphthol, β-naphthol, 3,5-xylenol, thymol, methyl-4-hydroxybenzoate, 4-hydroxyacetophenone, novolac type phenolic resin,
2,2'-thiobis(4,6-dichlorophenol), catechol, resorcinol, hydroquinone,
Pyrogallol, phloroglycin, phloroglycin 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-chlorobenzyl p-hydroxybenzoate,
o-chlorobenzyl p-hydroxybenzoate,
p-methylbenzyl p-hydroxybenzoate,
n-octyl p-hydroxybenzoate, benzoic acid, zinc salicylate, 1-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2-
Zinc hydroxy-6-naphthoate, 4-hydroxydiphenylsulfone, 4-hydroxy-4'-chlorodiphenylsulfone, bis(4-hydroxyphenyl)sulfide, 2-hydroxy-p-toluic acid, 3,5- Zinc di-tert-butylsalicylate, tin 3,5-di-tert-butylsalicylate,
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, in order to obtain a heat-sensitive recording material,
When a leuco dye and a coloring agent are bonded and supported on a support, various conventional binders can be used as appropriate. Further, in order to obtain a pressure-sensitive recording material, when an encapsulated leuco dye is supported on a support or a coloring agent is supported on a support, various commonly used binders can be used as appropriate. Specific examples of such binders include the following. Polyvinyl alcohol, starch and its derivatives, cellulose derivatives such as methoxycellulose, hydroxyethylcellulose, carboxymethylcellulose, methylcellulose, ethylcellulose, sodium polyacrylate, polyvinylpyrrolidone, acrylic amide/acrylic ester copolymer, acrylic amide/acrylic acid ester/
In addition to water-soluble polymers such as methacrylic acid ternary copolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali salt, polyacrylamide, sodium alginate, gelatin, and casein, polyacetic acid Vinyl, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride/
Vinyl acetate copolymer, polybutyl methacrylate, ethylene/vinyl acetate copolymer, styrene/
Latexes such as butadiene/acrylic copolymers, etc. In addition, in the present invention, if necessary, auxiliary additive components commonly used in this type of pressure-sensitive and heat-sensitive recording materials, such as fillers, surfactants, thermofusible substances,
A lubricant, pressure coloring inhibitor, etc. can be used in combination. In this case, fillers include, for example, calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated inorganic fine powders such as calcium and silica. , urea-formalin resin,
Organic fine powders such as styrene/methacrylic acid copolymer and polystyrene resin can be mentioned, and examples of lubricants include higher fatty acids and their metal salts, higher fatty acid amides, higher fatty acid esters, animal-based, vegetable-based, and mineral-based. Alternatively, various petroleum-based waxes may be mentioned. In the present invention, when producing a pressure-sensitive recording material, the coloring agent sheet is prepared by dispersing or dissolving the coloring agent in water or an organic solvent using an appropriate dispersant, and then adding a binder as necessary to form a sheet of paper or the like. On the other hand, the color former sheet is prepared by dispersing microencapsulated leuco dye with a suitable dispersant and coating it on a support such as paper. Microencapsulation in this case is for example USP2800457
It can be carried out by a conventionally known method such as the method described in the specification of the present invention. On the other hand, when producing a heat-sensitive recording material, a dispersion of a leuco dye and a coloring agent obtained by dispersing them separately is mixed with a suitable binder, and this mixed solution is coated on a support such as paper. According to the present invention, there is also provided a thermal transfer type thermal recording material in which a leuco dye and a coloring agent are supported on separate supports. A heat-resistant sheet, such as a polyester film, is then applied to a support to form a transfer sheet, while a coloring agent is dispersed or dissolved in water or a solvent and applied to the support to form a receptor sheet. . The recording material of the present invention can be used in various fields like the conventional ones, but in particular, by taking advantage of its excellent near-infrared light absorption properties, it can be used in optical character reading devices, label barcoders, It can be used as a recording material for reading records with a barcode reader. When the recording material of the present invention is used as a heat-sensitive recording label sheet, a heat-sensitive coloring layer containing the above-mentioned leuco dye and coloring agent is provided on one side of the support, and an adhesive is provided on the other side of the support. It is sufficient to have a structure in which a release mount is provided between the layers, and in this case, in order to improve image stability, if necessary,
A protective layer such as a water-soluble resin layer can also be provided on the surface of the thermosensitive coloring layer. The leuco dye used in the present invention is produced by reducing the carbonyl group of bis(p-disubstituted aminobenzal)acetone with a carbonyl reducing agent, such as lithium aluminum hydride, and adding an acid such as perchloric acid. Styril) Make carbenium salt. Next, an organic sulfinic acid sodium salt is added to this salt and reacted to obtain the desired product. [Effect] By using the special leuco dye represented by the above general formula, the recording material of the present invention absorbs the near-infrared region, and can be read by an image reading device using a general-purpose semiconductor laser. It has the advantage of being able to read images and is applied to various fields. Moreover, the leuco dye used in the present invention can be produced at relatively low cost. [Example] Next, the present invention will be explained in more detail with reference to Examples. Note that all parts and percentages shown below are based on weight. Reference example 1 1 [bis(p-dimethylaminostyryl)-p-
Synthesis of methylphenylsulfonylmethane] (A) Synthesis of bis(p-dimethylaminobenzal)acetone Add 22.35 g of p-dimethylbenzaldehyde and 4.35 g of acetone to 150 c.c. of ethanol, stir and dissolve, then add caustic soda. Add 30 ml of 10% aqueous solution, protect from light, and leave for 3 days with occasional shaking. The resulting precipitate was filtered, thoroughly washed with water, and then recrystallized from a mixed solution of ethanol/ethyl acetate to give red-orange crystals (mp 197-199℃) 18.5
get g. (B) Synthesis of bis(p-dimethylaminostyryl)carbenium perchlorate 12.82 g of bis(p-dimethylaminobenzal)acetone is dissolved in dry tetrahydrofuran. A solution prepared by dispersing 0.5 g of lithium aluminum hydride in 150 c.c. of tetrahydrofuran was added dropwise to this solution at room temperature over 1 hour, heated at 40°C for 10 minutes, cooled, added 60 c.c. of water, and then added acetic acid. 90c.c.
Add dropwise a mixed solution of 6.7 g of 60% perchloric acid. This dropwise addition turns the solution into a dark green-blue color, and 200 c.c. of water is added thereto and the solution is cooled and filtered to obtain dark green crystals. When this is recrystallized with nitromethane/ether, dark green crystals with a golden luster (decomposition point
200-210℃) to obtain 6.7g. (C) Bis(p-dimethylaminostyryl)-p-
Synthesis of methylphenylsulfonylmethane 2.8 g of bis(p-dimethylaminostyryl)carbenium perchlorate and 1.9 g of acetic acid were added to 80 c.c. of methanol, and 3 g of sodium p-toluenesulfinate was added to 50 c.c. of methanol. Add the solution dropwise and heat to reflux for 1 hour. The formed precipitate is collected by filtration and recrystallized from a benzene/hexane mixed solvent to obtain 2.9 g of pale yellow crystals (melting point: 147-150°C). [Light absorption characteristics] λmax (benzene) 353 mμ, ε: 3.3×10 ⁴ λmax (acetic acid) 792 mμ, ε: 2.0×10 ⁵ [Elemental analysis] H (%) C (%) N (%) Calculated value: 7.00 73.01 6.08 Analysis value: 7.02 73.09 6.15 Reference example 2 [Bis(p-diethylaminostyryl)-p-
Synthesis of methylphenylsulfonylmethane] 3.2 g of bis(p-diethylaminostyryl) carbenium perchlorate and 1.9 g of acetic acid were mixed with methanol.
A solution of 3 g of sodium p-toluenesulfinate in 50 cc of methanol was added dropwise to the mixture, and the mixture was heated under reflux for 1 hour. The formed precipitate is filtered and recrystallized from benzene/hexane to obtain 3.1 g of pale yellow crystals (melting point 143-146°C). [Light absorption characteristics] λmax (benzene) 354 mμ, ε3.4×10 ⁴ λmax (acetic acid) 793 mμ, ε2.1×10 ⁴ [Elemental analysis] H (%) C (%) N (%) Calculated values: 7.41 74.38 5.42 Analysis value: 7.42 74.51 5.51 Reference example 3 [Bis(p-dimethylaminostyryl)-benzenesulfonylmethane synthesis] Reference example 1 except that sodium benzenesulfinate was used instead of sodium p-toluenesulfinate
In the same manner as in step (C), 2.8 g of pale yellow crystals (melting point 142-145°C) were obtained as the desired product. [Light absorption characteristics] λmax (benzene) 355 mμ, ε: 3.0×10 ⁴ λmax (acetic acid) 795 mμ, ε: 1.9×10 ⁵ [Elemental analysis] H (%) C (%) N (%) Calculated value: 6.77 72.61 6.27 Analysis value: 6.85 72.51 6.26 Reference example 4 [Synthesis of bis(p-diethylaminostyryl)-benzenesulfonylmethane] Reference example 2 except that sodium benzenesulfinate was used instead of sodium p-toluenesulfinate
Similarly to
~142°C) 3.0g was obtained. Reference Example 5 [Preparation of microcapsules] Add 10 parts of gelatin and 10 parts of gum arabic to 40°C water.
Dissolved in 400 parts and added 0.2 parts of funnel oil as an emulsifier.
1 part, and further 40 parts of diisopropylnaphthalene oil containing 2% leuco dye dissolved therein were emulsified and dispersed. Stop emulsification when the average size of the oil particles reaches 5 μm, and add water at 40°C to make a total of 900 parts and continue stirring. At this time, make sure that the liquid temperature does not drop below 40℃. Next, add 10% acetic acid to adjust the pH of the liquid to 4.0.
Adjust to ~4.2 to allow coacervation to occur. The mixture is further stirred and cooled after 20 minutes to gel the coacervate film deposited around the oil droplets. Adjust the liquid temperature to 20℃ and add 37% formaldehyde 7.
After the temperature reaches 10℃, add 15% caustic soda aqueous solution and adjust the pH to 9. At this time, add caustic soda slowly and carefully. Subsequently, 20
Stir and heat for 50°C to create microcapsules of leuco dye-dissolved oil. When pressure-sensitive paper is obtained by supporting these microcapsules on a support, the amount of the microcapsules attached to the support is usually 5 to 10 g/m ² . Examples 1 to 3, Comparative Examples 1 to 2 Microencapsulated leuco dyes shown in Table 1 were added to a commercially available pressure-sensitive coloring (or color developing) sheet at a rate of 6 g/m ² using water-soluble starch as a binder. When the colored sheets obtained by coating and drying were stacked together and the color was developed using pressure from the pen, clear records were obtained in all cases. Table 1 shows the color tone and absorption region wavelength in the reflection spectrum.

[Liquid A]

Leuco dye in Table 2 10 parts Hydroxyethyl cellulose 10% aqueous solution 10〃 Water 55〃 [Liquid B] Stearic acid amide 20 parts Methyl cellulose 5% aqueous solution 20〃 Dispersant 2〃 Water 60〃 [C liquid] Calcium carbonate 30 parts Methyl Cellulose 5% aqueous solution 30〃 Dispersant 2〃 Water 60〃 [Liquid D] Activated clay 30 parts Urea-formalin resin filler 10〃 Polyvinyl alcohol 10% aqueous solution 20〃 Water 140〃 [Liquid A] obtained as above , [Liquid B], [C
Prepare a coating by mixing the [liquid] in a ratio of 1:1:1, and apply and dry the coating solution on high-quality paper with a basis weight of 50 g/m ² so that the dry adhesion is 0.45 g/m ² of the dye. death,
Further, [Liquid D] was coated thereon and dried to give a dry solid amount of 2 g/m ² to obtain a heat-sensitive recording material. Next, the heat-sensitive recording material thus obtained was subjected to a color development test to measure the color density, the background density, and the absorption range (wavelength) of the colored image and its light fastness. The results are shown in Table-2. The color density was determined using a thermal gradient tester at 130°C.
The value is for 1 second (applied pressure 2.0Kg/cm ² ), and is measured using the Macbeth densitometer's black filter (filter No.:
Measured values for both the Kodak Latten No. 106) and the blue filter (Filter No.: Kodak Latten No. 25) are shown. The light resistance is the density after being irradiated with 5000 lux for one week, and is the value measured using a black filter. The background density is also the value obtained using a black filter. The absorption region wavelength is the reflection spectrum of the coloring part.

[Table] * Manufactured by a method similar to Reference Example 1 As is clear from the results in Table 2, in the case of the product of the present invention, the absorption region wavelength is in the range of 700 to 950 mμ, while in the case of the comparative example, It can be seen that there is almost no absorption above 700 mμ, and the product of the present invention is extremely useful as a near-infrared absorbing leuco dye. Furthermore, the product of the present invention has superior light resistance (stability of images to light) compared to products of comparative examples.

Claims (1)

[Scope of Claims] 1. A recording material that utilizes a color-forming reaction between a leuco dye and a coloring agent that causes the leuco dye to develop color upon contact, wherein at least one of the leuco dyes is a compound represented by the following general formula: Recording material characterized by: (In the formula, R ₁ , R ₂ , R ₃ and R ₄ are hydrogen or an alkyl group, R ₅ and R ₆ are hydrogen, a phenyl group or a phenyl group substituted with an amino group or a dialkylamino group, and R ₇ is phenyl or a phenyl group substituted with an alkyl group).