JPH02139276A - Recording material - Google Patents

Abstract

PURPOSE:To obtain a recording material for formation thereon of developed color images which have strong absorption in a near infrared region and can be read over the range from the visible region to the near infrared region. CONSTITUTION:At least one of leuco dyes used is a compound of the formula, wherein each of R1 and R2 is a lower alkyl, substd. alkyl, substd. or unsubstd. aralkyl, or substd. or unsubstd. aryl, R3 is hydrogen, a lower alkyl, alkoxyl or aralkyloxyl, R4 is hydrogen, a lower alkyl, alkoxyl, halogen or dialkylamino, R5 is hydrogen, a halogen or dialkylamino, each of R6 and R7 is a lower alkyl, A is a benzene or naphthalene ring, and n is an integer of 1-4. Developed color images formed have strong absorption over the wavelength range of 700-1000nm, so that the images can be read satisfactorily by a general-purpose optical character reader or by an image reader employing a light-emitting diode or a semiconductor laser as a light source.

Description

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

[Prior art]

Recording materials using leuco dyes were published in Japanese Patent Publication No. 45-14039.
As seen in the above publication, it has been known for a long time, and has been used as pressure-sensitive recording paper, heat-sensitive recording paper, etc., and its usage is increasing year by year.

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 colors, that is, in the visible region, and in the near-infrared region, that is, absorption in the visible region.
At present, almost no dyes having absorption in the 1000 nm range have been developed. In recent years, as semiconductor lasers have become more popular, there is a movement to read recorded images such as bar codes with semiconductor lasers, and pressure-sensitive paper, thermal paper, etc. are also required to have absorption in the near-infrared region. It's here.

Several proposals have been made in recent years regarding leuco dyes and heat-sensitive and pressure-sensitive recording materials that absorb in the near-infrared region. Phthalide compounds containing one or two vinyl groups such as those found in
Fluorene compounds such as those found in JP-A No. 9-199757 and JP-A-60-226871 and JP-A-62-8598
Fluoran compounds such as those seen in No. 6 and JP-A-60-
There are sulfonylmethane compounds as seen in No. 231766.

However, although these recording materials have absorption in the near-infrared region, their strength is insufficient, resulting in insufficient reading by optical reading devices, poor stability, and the tendency for one image to fade. There were some drawbacks.

〔the purpose〕

The present invention provides a recording material whose colored images have strong absorption in the near-infrared region and can be read from the visible region to the near-infrared region using a novel leuco dye that has excellent storage stability. The purpose is to

〔composition〕

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 undergo special color development, at least one of the leuco dyes has the following general formula (1).
) A recording material is provided which is characterized by being a compound represented by:

(Rx-Ri: lower alkyl group, substituted alkyl group, substituted or unsubstituted aralkyl group, substituted or unsubstituted aryl group R3: hydrogen atom, lower alkyl group, alkoxy group, aralkyloxy group R4: hydrogen atom, lower alkyl group, alkoxy group, halogen, dialkylamino group R5: hydrogen atom, halogen, dialkylamino group R,,
R,: lower alkyl group ◎: benzene ring, naphthalene ring n: integer from 1 to 4) In the above general formula (I), specific examples of R1 and R3 include methyl group, ethyl group, propyl group, isopropyl group, Lower alkyl groups such as butyl group and isobutyl group: Substituted alkyl groups substituted with hydroxyl groups or cyano groups such as hydroxymethyl group, hydroxyethyl group, cyanomethyl group, and cyanoethyl group; Unsubstituted aryl groups such as phenyl group;
Lower alkyl groups such as methyl and ethyl groups, methoxy groups,
Lower alkoxy groups such as ethoxy groups, dimethylamino,
Substituted aryl groups substituted with dialkylamino groups such as diethylamino; unsubstituted aralkyl groups such as benzyl and phenethyl groups; lower alkyl groups such as methyl and ethyl groups, and dialkylamino groups such as dimethylamino and diethylamino groups. Examples include substituted aralkyl groups substituted with . Specific examples of R1 include hydrogen: lower alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, and isobutyl group: methoxy group, ethoxy group,
Lower alkoxy groups such as propoxy group and isopropoxy group: aralkyloxy groups such as benzyloxy group and phenylethyloxy group; R4 is a hydrogen atom; Alkyl groups: Alkoxy groups such as methoxy, ethoxy, and propoxy groups: Examples include halogen dimethylamino groups such as chlorine and bromine, dialkylamino groups such as diethylamino groups, and R6 is a hydrogen atom:
Examples include halogen dimethylamino groups such as chlorine and bromine, dialkylamino groups such as diethylamino groups, and RG and R7 include lower alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, and isobutyl group. can be mentioned.

The leuco dye represented by the above general formula is a novel compound, usually a white or pale yellow-green solid, and can be easily synthesized according to the following reaction formula.

[Specific examples of compounds of general formula (1)] (In the formula, R0lRa mountain IR4 mountain r Ri r R1+ @
*n is the same as above) Specific examples of the leuco dye represented by the above general formula in the present invention are listed below, but the invention is not necessarily limited thereto.

/”% CH2Cl(3 /N% CIl, C11゜ C11゜ C11゜ ul.

Shi1chi 113t, listen.

The color tone of the leuco dye represented by the general formula used in the present invention ranges from deep blue to reddish-black, but it can also be used in combination with other leuco dyes for the purpose of color tone correction or absorption characteristic correction.

The leuco dyes used in combination in this case include leuco dyes that are generally known for this type of leuco recording material, such as triphenylmethane, fluoran, phenothiazine, auramine, and spiropyran dyes. Leuco compounds of such dyes are preferably used. Specific examples of such leuco dyes include those shown below.

3.3-bis(p-dimethylaminophenyl)-phthalide, 3.3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide (also known as crystal violet lactone), 3.3-bis(P- dimethylaminophenyl)-6-dibutylaminophenyl, 3.3-bis(ρ-dimethylaminophenyl)-6-chlorophthalide, 3.3-bis(p-dibutylaminophenyl)phthalide, 3-cyclohexylamino-6- Chlorfluorane.

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-dinithylaminofluorane, 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-(0-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)fluoran, 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'-dimethyl) aminophenyl)-3-(2'-hydroxy-47-chloro-5'
-methylphenyl)phthalide, 3-morpholino-7-(N-propyl-trifluoromethylanilino)fluorane, 3-pyrrolidium-7-trifluoromethylanilinofluorane, 3-diethylamino-5-chloro-7-( N-benzyl-trifluoromethylanilino)fluoran, 3-pyrrolidino-7-(di-ρ-chlorophenyl)methylaminofluorane, 3-diethylamino-5-gloro-7-(α-)engineered methylethylamino)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-
Gullow 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, 3-diethylamino-6-methyl-7-(2',4'-
dimethylanilino) fluorane, 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 things are conventionally known, and specific examples are as follows:
Inorganic acids, organic acids, phenolic substances, such as the following:
Examples include phenol resin.

Ben I-night, zeolite 1~, acid clay, activated clay, silica gel, phenolic resin, 4.4'-isopropylidene bisphenol, 4.4
′ -isopropylidene bis(0-methylphenol)
, 4.4'-Secondary-butylidenebisphenol 4.4'-Isopropylidenebis(0-tert-
butylphenol), 4.4'-cyclohexylidene diphenol, 4.4
′ -isopropylidene bis(2-chlorophenol)
.

2.2'-methylenebis(4-methyl-6-tert-butylphenol), 2.2'-methylenebis(4-ethyl-6-tert-butylphenol), 4.4'-butylidenebis(6-tert-butyl-2 -methyl)phenol, 1.1.3-tris(2-methyl-4-hydroxy-
5=tertiarybutylphenyl)butane, 1.1.3-
Tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 4,4'-thiobis(6-tert-butyl-2-
methyl)phenol, 4.4'-diphenolsulfone, 4.2'-diphenolsulfone, 4-impropoxy-4'-hydroxydiphenylsulfone, 4-benzyloxy-4'-hydroxydiphenylsulfone, 4.4'- Diphenol sulfoxide, Isopropyl P-Hydroxybenzoate, P-Hydroxy Yasumi, Benzyl Froate, Benzyl Protocatechuate, Stearyl Gallate, Lauryl Gallate, Octyl Gallate, 1.7-Bis(4-Hydroxyphenylthio)- 3,5
-dioxahebutane, 1.5-bis(4-hydroxyphenylthio)-3-oxapentane, 1.3-bis(4-hydroxyphenylthio)-propane, 2.2'-methylenebis(4-ethyl-6) - tert-butylphenol).

1.3-bis(4-hydroxyphenylthio)-2-
Hydroxypropane, N,N'-diphenylthiourea.

N,N'-di(m-chlorophenyl)thiourea, salicylanilide.

5-chloro-salicylanilide.

Salicyl-〇-chloroanilide, 2-hydroxy-3-naphthoic acid, 11 antipiricitas of thiocyanate, zinc salt of 2-acetyloxy-3-naphthoic acid, 2-hydroxy-
1-naphthoic acid, 1-hydroxy-2-naphthoic acid, metal salts of hydroxynaphthoic acid such as zinc, aluminum, calcium, etc. Bis-(4-hydroxyphenyl)acetic acid methyl ester, Bis-(4-hydroxyphenyl)acetic acid benzyl ester , 1.3-bis(4-hydroxycumyl)benzene, ■,
4-bis(4-hydroxycumyl)benzene, 2.4'
-diphenolsulfone, 3,3'-diallyl-4,4'-diphenolsulfone, α,α-bis(4-hydroxyphenyl)-α-methyltoluene, antipyrine complex of zinc thiocyanate, tetrabromobisphenol A, tetra Bromobisphenol S, 3,4-dihydroxy-4'-methyldiphenylsulfone, etc.

In the present invention, when a leuco dye and a coloring agent are bonded and supported on a support in order to obtain a heat-sensitive recording material, 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 ester/methacrylic acid ternary copolymer, styrene/maleic anhydride copolymer alkali salt, isobutylene/maleic anhydride copolymer alkali In addition to water-soluble polymers such as salt, polyacrylamide, sodium alginate, gelatin, and casein, polyvinyl acetate, polyurethane, styrene/butadiene copolymer, polyacrylic acid, polyacrylic acid ester, vinyl chloride/vinyl acetate copolymer , polybutyl methacrylate, ethylene/vinyl acetate copolymer, styrene/
Latex such as butadiene/acrylic copolymer.

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, lubricants, pressure coloration inhibitors, etc. Can be used together.

In this case, fillers include, for example, inorganic fine powders such as calcium carbonate, silica, zinc oxide, titanium oxide, aluminum hydroxide, zinc hydroxide, barium sulfate, clay talc, surface-treated calcium and silica, and urea. - Examples include organic fine powders such as 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, higher fatty acid esters, and various animal, vegetable, mineral, or petroleum waxes.

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 1 e.g. USP 2800
This can be carried out by conventionally known methods such as the method described in No. 457.

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.

In this case, the coloring layer may be applied as one layer or two or more layers, or may be applied as a leuco dye layer and a coloring agent layer, or as is known for heat-sensitive recording materials. It is also possible to provide an undercoat layer or a protective layer.

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, for example, 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 and label barcode readers. , 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〕

By using the leuco dye represented by the general formula (1), the recording material of the present invention has a color image of 700 to 1.0.
00n111, has strong absorption ability and is a general-purpose OC.
The image can be sufficiently read by an optical character reader (R) or an image reader using a light emitting diode or a semiconductor laser as a light source, and has the effect of widening the field of use.

〔Example〕

Hereinafter, 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) [Preparation of microcapsules] 10 parts of gelatin and 10 parts of gum arabic were dissolved in 400 parts of 40 cc of water, and 0.2 parts of funnel oil was added as an emulsifier.
1 part, and further 40 parts of diisopropylnaphthalene oil in which the leuco dye of general formula (1) is sparsely dissolved is emulsified and dispersed. Stop emulsification when the size of the oil droplets reaches 5 μm on average,
Add 40°C water to bring the total to 900 parts and continue stirring. At this time, make sure that the liquid temperature does not drop below 40°C. Next, add 10% acetic acid to bring the pl+ of the solution to 4.0 to 4.2.
to cause coacervation. The mixture is further stirred and cooled after 20 minutes to gel the coacervate film deposited around the oil droplets. Bring the temperature of the solution to 20°C, add 7 parts of 37% formaldehyde, and after the temperature reaches 10°C, add 15% caustic soda solution to adjust the pH to 9.

At this time, the caustic soda was added slowly and carefully, and then the mixture was stirred and heated for 20 minutes to 50° C., thereby creating microcapsules of leuco dye-dissolved oil. When making pressure-sensitive paper by supporting these microcapsules on a support, the amount of microcapsules attached to the support is usually 5.
~lOg/rr? It is.

Examples 1 to 4, Comparative Examples 1 to 2 A commercially available pressure-sensitive coloring sheet was coated with 6 g/m of microcapsules of the leuco dye shown in Table 1 using water-soluble starch as a binder, and the dried coloring sheet was layered and the writing pressure was applied. When color was developed using , a clear blue-green image was obtained in each case.

Table I shows the Pcs values at 90Onll.

Here, the PO2 value is obtained by measuring absorbance with a Hitachi spectrophotometer, converting the absorbance into reflectance, and using the following formula.

Table 1 Examples 5 to 16, Comparative Examples 3 to 5 Each mixture having the following composition was dispersed in a ball mill [A
[Liquid] and [Liquid B] were prepared.

[Liquid A]

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

30 parts [Liquid B] 4.4'-Diphenolsulfone 30 parts Stearic acid amide 20 parts Calcium carbonate 20 parts Polyvinyl alcohol 10% aqueous solution 70 parts Water
245 copies [A
[Liquid] and [Liquid B] were mixed at a ratio of tit to obtain a heat-sensitive coating liquid. This was coated on high-quality paper with a basis weight of 50 g/tri' so that the dye solid content was 0.5 g/rrl' and dried to obtain heat-sensitive recording paper.

Table 2 shows the color tone and PO2 value of the heat-sensitive recording paper obtained as described above, which was printed and colored using an ordinary printer.

Examples 16-21 In Example 8, except that the coloring agent in Table 3 was used instead of 4,4'-diphenolsulfone in [Liquid B],
A thermosensitive recording paper was prepared in the same manner as in Example 8, and colored printing was performed. The results are shown in Table-3.

Table 3 As is clear from the results in Tables 2 and 3, the heat-sensitive recording material of the present invention forms colored images with excellent absorption in the near-infrared region.

Examples 22 to 37 In Example 5, the leuco dye shown in the following Table 4 was used instead of the leuco dye [compound of specific example (1)] shown in Table 2 of [Liquid A], Furthermore, 4.4'- of [Liquid B]
A thermosensitive recording paper was prepared in the same manner as in Example 5, except that 4,4'-diisopropylidene bisphenol was used in place of diphenolsulfone, and color printing was performed. The results are shown in Table 4.

Table-4

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. Characteristic recording materials. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (R_1, R_2: lower alkyl group, substituted alkyl group,
Substituted or unsubstituted aralkyl group, substituted or unsubstituted aryl group R_3: Hydrogen atom, lower alkyl group, alkoxy group, aralkyloxy group R_4: Hydrogen atom, lower alkyl group, alkoxy group, halogen, dialkylamino group R_5: Hydrogen Atom, halogen, dialkylamino group R_6, R_7: Lower alkyl group ▲ Numerical formula, chemical formula, table, etc. ▼: Benzene ring, naphthalene ring n: Integer from 1 to 4)