JPS63299977A - Near infrared-absorptive recording material - Google Patents

Abstract

PURPOSE:To enable reading of recorded images under a source of light visible to near infrared regions and obtain excellent stability of dye images, by incorporating a specified compound as at least one leuco dye. CONSTITUTION:A compound of formula (I), wherein each of R1, R2, R3 and R4 is a lower alkyl, R5 is alpha- or beta-naphthyl or --NHCOR8, and each of R6, R7 and R8 is hydrogen or a lower alkyl, is used as at least one of leuco dyes, in a recording material utilizing color forming reactions between the leuco dyes and color reaction agents for developing the leuco dyes into colors upon making contact therewith. The leuco dye of formula (I) is a white or light yellow crystalline powder stable in the atmosphere, shows strong absorption in a near infrared region of 600-1000 nm, and performs a rapid color forming reaction upon making contact with an inorganic acid or an electron-acceptive compound at a molecular level, while a color-developed coloring matter displays excellent preservability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a recording material having a near-infrared light absorption image, particularly in heat-sensitive recording or pressure-sensitive recording.

[Prior art]

Recording materials using leuco dyes have been known for a long time.
In recent years, it has been widely used as pressure-sensitive recording paper and heat-sensitive recording paper. Commonly used leuco dyes include, for example, triphenylmethane, fluoran, phenothiazine, and auramine dyes. These dyes come in a variety of colors and are used depending on the purpose. However, many of these dyes have been developed for the purpose of absorbing color tones, that is, in the visible region, and have been developed for the purpose of absorbing in the near-infrared region, that is, in the visible region.
At present, very few dyes having absorption in the range of 700 to 1000 nanometers have been developed. In recent years, as semiconductor lasers have become more popular, there has been a movement to read recorded images such as barcodes with semiconductor lasers, and even thermal paper, pressure-sensitive paper, etc.
It is now required to have absorption in the near-infrared region.

Recently, several proposals have been made regarding leuco dyes that absorb in the near-infrared region. For example, JP-A-51-121035
No., JP-A-51-121037, JP-A-51'-12
No. 1038, JP-A-57-167979 and JP-A-5
Monovinyl- or divinyl-containing phthalide compounds such as those found in JP-A No. 8-157779, JP-A-59-199757
and fluorene compounds such as those found in Japanese Patent Application Laid-open No. 60-226871. However, although these compounds have absorption in the near-infrared region, they have drawbacks such as insufficient absorption strength, poor dye stability, and images that easily fade, and high manufacturing costs. have.

In addition, a new near-infrared absorbing leuco dye has been proposed in JP-A No. 60-231766, but although this dye has strong near-infrared absorption, its storage stability is insufficient, and especially It has the disadvantage of poor heat stability. Therefore, the current situation is that a satisfactory near-infrared absorbing dye has not yet been found.

〔the purpose〕

The present invention uses a novel leuco dye that has strong absorption in the near-infrared region and has excellent storage stability, and can be read with a light source from the visible region to the near-infrared region. The purpose is to provide a new recording material with excellent stability.

〔composition〕

According to the present invention, in a recording material that utilizes a color-forming reaction between a leuco dye and a coloring agent that causes the leuco dye to develop a color upon contact, at least one of the leuco dyes is represented by the following general formula (1). A recording material is provided which is characterized in that it is a compound that is

However, in the formula, R #RIIIR3 and R9 are lower alkyl groups, and RS is an α- or β-naphthyl group or -
〇-NHCOR.

and RG, R, and R6 are hydrogen atoms or lower alkyl groups.

The leuco dye represented by the general formula (1) used in the present invention is a new substance, is a white or pale yellow crystalline powder that is stable in the atmosphere, and has a wavelength range of 600 to 11,000 nm in the near-infrared region. It exhibits strong absorption, and when it comes into contact at the molecular level with inorganic acids such as acid clay and activated clay, as well as electron-accepting compounds (i.e., coloring agents) such as organic acids, phenolic compounds, and phenolic resins, the coloring reaction occurs quickly. This color is useful as a dye precursor because it has excellent storage stability.

The leuco dye represented by the general formula (1) used in the present invention can generally be easily synthesized according to the following reaction formula.

Soba≦ (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 or the like. In addition, regarding the manufacturing method of compound (II) in the reaction formula, for example, Annalen
der Chemie, vol. 623, p. 204 (1959
)It is described in.

R-R4 and R5-R in the general formula (1) of the present invention
The lower alkyl group of 0 is usually a straight chain or branched alkyl group having 1 to 4 carbon atoms.

Specific examples of the compound represented by the general formula (I) are as follows.

[Specific examples of compounds of general formula (1)] In the present invention, when the leuco dye is used as a pressure-sensitive recording material, it may be prepared by a method as described in, for example, US Pat. No. 2,800,457. Can be done. The main physical properties required of the leuco dye in this case include oil solubility, coloring properties with a coloring agent, storage stability of dye images, etc., and the leuco dye is selected in consideration of these physical properties.

In the present invention, when the leuco dye is used as a heat-sensitive recording material, it can be prepared, for example, by the method described in Japanese Patent Publication No. 14039/1983. In this case, the main physical properties required of the leuco dye include thermal coloring properties, background whiteness, and storage stability of the leuco dye and its coloring dye, and the leuco dye is selected in consideration of these physical properties.

In either case, the image of the leuco dye has the property of having sufficient absorption characteristics in the near-infrared region.
It is important to make full use of it.

The color tone of the leuco dye represented by the general formula (1) used in the present invention is green to blue, but it can also 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 combination in this case, leuco dyes that are generally known for this type of leuco recording material are used, and specific examples of such leuco dyes include those shown below. Can be mentioned.

3.3-bis(p-dimethylaminophenyl)-phthalide, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3.3-bis(p-dimethylaminophenyl)-6 -dibutylaminophenyl, 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-chlorofluorane, 3-(N-P-tolyl-he-dithylamino)-6-methyl-7-anilinofluorane, 3-pyrrolidino-6-methyl-7-anilinofluorane, 2- (N-(3'-trifluoromethylphenyl)
amino)-6-dinithylaminofluorane, 2-(3
, 6-bis(diethylamino)-9-(o-chloroanilino)xantylbenzoic acid lactam), 3-diethylamino-6-methyl-7-(n+-trichloromethylanilino)fluoran, 3-diethylamino-7-(0- 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'-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-(d-chlorophenyl)methylaminofluorane, 3-diethylamino-5-chloro-7-(α-phenylethylamino)fluorane, 3-(N-ethyl-p-toluidino)-7,(α-phenyl ethylamino)fluoran, 3-diethylamino-7-(o-methoxycarbonylphenylamino)fluoran, 3-diethylamino-5-methyl-7-(α-phenylethylamino)fluoran, 3-diethylamino-7-piperidinofluoran Oran.

2-chloro-3-(N-methyltoluidino)-7-(p
-n-butylanilino)fluorane, 3-(N-benzyl-N-cyclohexylamino)-5
, 6-penzo 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 materials are conventionally known, and specific examples thereof include those 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-1r-chlorophenylthiourea, di- -m-trifluoromethylphenylthiourea, di-phenylthiourea, salicylanilide, 4,4'-isopropylidenediphenol, 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'-5ec-butylidene diphenyl, 4,4'-cyclohexylidene bisphenol, 4,4'-cyclohexylidene bis(2-methylphenol) , 4-tert-butylphenol, 4-phenylphenol, 4-hydroxydiphenoxide, α
-Naphthol, β-naphthol, dimethyl 5-hydroxyphthalate, methyl-4-hydroxybenzoate, 4
-Hydroxyacetophenone, novolak type phenolic resin, 2,2'-thiobis(4,6-dichlorophenol).

Catechol, resorcinol, hydroquinone, pyrogallol, phloroglycin, prologlycin carboxylic acid, 4-
tert-octylcatechol, 2,2'-methylenebis(4-chlorophenol), 2,2'-methylenebis(4-methyl-6-tart-butylphenol), 2
, 2'-dihydroxydiphenyl, p-hydroxyambu, ethyl fragrant, propyl p-hydroxybenzoate, p-
Butyl hydroxybenzoate, benzyl P-hydroxybenzoate, P-chlorobenzyl p-hydroxybenzoate, 0-chlorobenzyl p-hydroxybenzoate, P-
ρ-Methylbenzyl hydroxybenzoate, n-octyl p-hydroxybenzoate, benzoic acid, zinc salicylate, l-hydroxy-2-naphthoic acid, 2-hydroxy-6-naphthoic acid, 2-hydroxy-6-naphthoic acid Zinc acid, 4-hydroxydiphenylsulfone, 4,2'-
Diphenolsulfone, 4-hydroxy-4'-chlorodiphenylsulfone, 4-hydroxy-4'-benzyloxydiphenylsulfone, 4-hydroxy-4'-isopropoxydiphenylsulfone, 4-hydroxy-4'
-isobutyloxydiphenyl sulfone, bis(4-hydroxyphenyl) sulfide, 2-hydroxy-ρ-
Toluic acid, zinc 3,5-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, methylenebis-(oxyethylenethio)diphenol, ethylenebis-(oxyethylenethio)diphenol, bis-(4-hydroxyphenyltheoethyl)ketone, bis- (4-hydroxyphenylthioethyl)ether, m-xylylenebis(4-hydroxyphenylthio)ether, etc.

In order to obtain a pressure-sensitive recording material in the present invention, first, 1-4% leuco dye is dissolved in alkylnaphthalene-based or terphenyl-based oil, and a resin such as gelatin is hardened.
- Create front and back microcapsules. The microcapsules are coated onto a support such as paper or plastic film using a binder to obtain a color former sheet. Microencapsulation in this case is for example USP280045
This can be carried out by conventionally known methods such as the method described in No. 7 specification. On the other hand, a color former sheet is prepared by dispersing or dissolving a color former in water or an organic solvent using a suitable dispersant, adding a binder if necessary, and applying the mixture to a support such as paper.

In order to obtain a heat-sensitive recording material in the present invention, a leuco dye and a coloring agent are each dispersed in a water-soluble resin, an appropriate binder is mixed with the dispersion, and the mixture is spread on a support such as paper. Apply. In this case, the particle size of the leuco dye is 0
．． It is preferable to set it to about 5 to 5 μI. Further, the weight ratio of the leuco dye to the coloring agent is suitably 1:1 to 1:58 degrees. Note that the coloring layer may be applied in one layer or in two or more layers, or may be applied separately as a leuco dye layer and a coloring agent layer. Also, as is known for heat-sensitive recording materials,
It is also possible to provide an undercoat layer or a protective layer.

In addition, in order to obtain a thermal transfer type recording material in the present invention, a leuco dye is dispersed or dissolved in water or a solvent and applied to a heat-resistant support such as a polyester film to create a transfer sheet, while a coloring agent is A receptor sheet is prepared by dispersing or dissolving the mixture in water or a solvent and applying it to a support.

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, and in order to obtain a pressure-sensitive recording material, When supporting an encapsulated leuco dye or a coloring agent on a support, various conventional 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, acrylamide/acrylic ester copolymer, acrylamide/acrylic 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, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer, and polybutyl methacrylate. , latexes such as ethylene/vinyl acetate copolymers, styrene/butadiene/acrylic copolymers, etc.

Also, if necessary, auxiliary additive components customary for pressure- and heat-sensitive recording materials of this type, such as fillers.

A surfactant, a thermofusible substance, a lubricant, a pressure coloring inhibitor, etc. can be used in combination. In this case, examples of fillers include calcium carbonate, silica, zinc oxide, titanium oxide,
Inorganic fine powders such as aluminum hydroxide, zinc hydroxide, barium sulfate, clay, talc, and surface-treated calcium and silica, as well as organic powders such as urea-formalin resin, styrene/methacrylic acid copolymer, and polystyrene resin. Examples of the lubricant include higher fatty acids and their metal salts, higher fatty acid amides, high paper fatty acid esters, and various animal, vegetable, mineral, or petroleum waxes.

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 and label barcoders. , it can be used as a recording material for recording reading by 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 may have a structure in which a release mount is provided between layers.

〔effect〕

The novel leuco dye represented by the general formula (1) used in the present invention exhibits strong absorption ability in the near-infrared region ranging from 600 to 11,000 nm. Therefore, the recording material of the present invention obtained using the leuco dye can be read with light sources from the visible region to the near-infrared region, and the dye image has excellent storage stability, especially thermal stability. Even under these conditions, the image can be sufficiently read by an image reading device using a semiconductor laser or the like as a light source.

〔Example〕

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

Reference Example 1 Synthesis of bis(ρ-dimethylaminostyryl)-α-naphthylsulfonylmethane [Compound Example No. (1)) 2.8 g of bis(P-dimethylaminostyryl)carbeniram perchlorate and 1.9 g of acetic acid was added to 80 cc of methanol, and 4.1 g of α-naphthylsulfinic acid sodium was added to this.
80 cc of methanol solution was added dropwise, and the mixture was heated under reflux for 1 hour. The generated precipitate was collected by filtration and recrystallized from a mixed solvent of benzene/hexane to give pale yellow crystals (melting point: 178-183℃).
) 3.1 g was obtained.

Reference Examples 2 to 3 Compound specific examples No. 2, (2) and No. ,(
Compound 3) was obtained.

Reference Example 4 Bis(2-dimethylaminostyryl) in Reference Example 1
Compound specific example No. (6) was prepared in the same manner as in Reference Example 1, except that bis(ρ-diethylaminostyryl)carbeniram perchlorate was used instead of carbeniram perchlorate.
The compound was obtained.

Reference Example 5 Bis(p-dimethylaminostyryl) in Reference Example 1
Compound specific example No. (9 ) was obtained.

Reference Example 6 Bis(P-dimethylaminostyryl) in Reference Example 1
Compound Specific Example N was prepared in the same manner as in Reference Example 1, except that bis(4-dimethylamino-2-methylstyryl)carbeniram perchlorate was used instead of carbeniram perchlorate.
o, the compound (10) was obtained.

Table 1 shows the color tone and melting point of the compounds obtained in Reference Examples 2 to 6 above.

Examples 1 to 6, Comparative Examples 1 to 3 Each mixture having the following composition was dispersed in a ball mill to prepare liquids (A) and (13).

[Liquid A]

Leuco dye in Table 2 10 parts 10% polyvinyl alcohol aqueous solution 10 parts water

30 parts [Liquid B] Stearamide 20 parts Calcium carbonate 20 parts 4.4'-diphenolsulfone 30 parts Polyvinyl alcohol 10% aqueous solution 35 parts Water
210 parts [Liquid A] and [Liquid B] obtained as above were mixed at a ratio of 1:1 to prepare a coating solution, and this coating solution was coated on high-quality paper with a dry solid content of the leuco dye. It was applied at a concentration of 0.6 g/I and dried to obtain a heat-sensitive recording material.

This was printed solidly using a reprint facsimile Rifax 130, and its quality was measured. The measurement results are shown in Table-2.

The concentration was measured using Macbeth Density Meter 914, and the filter was K.
It was measured using Odak Ratten No. 106. PC
The s value was determined by measuring absorbance with a reflection spectrophotometer (Hitachi 330), converting the absorbance into reflectance, and using the following formula.

In addition, the heat resistance test results show that the recorded image was placed in a constant temperature bath at 60℃ for 24 hours.
Concentrations after storage for time are shown.

Examples 7 to 10 Thermosensitive recording materials were obtained in the same manner as in Example 1, except that liquid (C) was used instead of liquid (B) in Example 1.

[Liquid C]

Stearamide 20 parts Calcium carbonate 20 parts B in Table 3
Group compound 30 parts Polyvinyl alcohol 10% aqueous solution 35 parts Water
The quality of 210 copies of the obtained heat-sensitive recording material was measured in the same manner as in Example 1. The results are shown in Table-3.

As is clear from Tables 2 and 3, the recording material of the present invention is suitable for the near-infrared region, that is, 600 to 1 OOOnm.
It can be seen that the material exhibits sufficiently strong absorption in the range of , and also has excellent heat resistance stability of the colored part, and has sufficient quality as a recording material.

Claims (1)

[Claims] (1) 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 a compound represented by the following general formula. Features of near-infrared absorption recording material. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R_1, R_2, R_3 and R_4 are lower alkyl groups, R_5 is α- or β-naphthyl group or ▲
There are mathematical formulas, chemical formulas, tables, etc. ▼, and R_6,
R_7 and R_8 each represent a hydrogen atom or a lower alkyl group. )