JPS63254165A - Novel leuco dye and recording material containing same - Google Patents

Abstract

NEW MATERIAL:The compound of formula I (R1-R8 are lower alkyl; R9 is H or lower alkyl). EXAMPLE:1,1,5,5-Tetra-(p-dimethylaminophenyl)-3-p-toluenesulfinyl-1,4- pentadiene. USE:An electron-donative color developing agent. Its color-developed part absorbs light of near infrared region and the developed color can be read with an image reading apparatus using general-purpose semiconductor laser. PREPARATION:The objective compound can be produced by adding a small amount of acetic acid to a tetra(dialkylaminophenyl)cyanine compound of formu la II (A<-> is anion), a substituted benzenesulfinic acid salt of formula III (X is Na, K or Li) and a catalyst, boiling and refluxing the mixture in an organic solvent, cooling the product, separating precipitated crystal by filtration and washing the crystal with water and an organic solvent.

Description

Detailed Description of the Invention The present invention relates to a novel leuco dye that develops color when brought into contact with an electron-accepting substance such as an inorganic acid, an organic acid, a phenolic compound or a derivative thereof, or an oxidizing agent; This invention relates to a recording material used as a color former.

[Prior art]

Recording materials using leuco dyes have been known for a long time.
It is used as pressure-sensitive recording paper, heat-sensitive recording paper, etc., and its usage is increasing year by year. Leuco-based pressure-sensitive recording materials generally utilize a chemical reaction between a colorless leuco dye and a coloring agent that causes the leuco dye to develop a special color upon contact to form a colored image. Specifically, a color former sheet coated with a microcapsule solution of leuco dye in an organic solvent and a color former sheet coated with a color former coated with a binder are placed one on top of the other, and the back side is Pressure is applied by twisting, pen pressure, etc. to destroy the capsule and cause a color reaction.

On the other hand, a leuco thermosensitive recording material has 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.

Compared to other recording materials such as electrophotography and electrostatic recording materials, these pressure-sensitive and heat-sensitive recording papers do not require complicated processes such as development and fixing, and can be processed in a short time using relatively simple equipment. It is used in many ways because it allows records to be obtained. The leuco dyes mainly used in such recording materials include crystal violet lactone, blue dyes represented by leuco crystal violet, and black dyes represented by 7-anilino-substituted fluoran compounds. In recent years, optical character reading devices and label barcode reading devices have been developed, and their usage is increasing. However, these devices use light sources with light wavelengths of 700 nm using light emitting diodes or semiconductor lasers.
The above light sources are commonly used. However, since the above-mentioned blue dye and black dye have almost no light absorption in the near-infrared region of 700 nm or more, the above-mentioned reading device cannot read the color. Therefore, the light absorption wavelength of the coloring material is 7
Currently, there is a strong demand for the development of new leuco dyes with a diameter of 00 nm or more.

In the past, several proposals have been made regarding leuco dyes that absorb long wavelengths, such as JP-A-51-121035, JP-A-51-121037, and JP-A-51-1210.
No. 38 and Japanese Unexamined Patent Publication No. 57-167979, these dyes have drawbacks of being difficult to synthesize and very high in cost.

〔the purpose〕

The present invention provides a novel leuco dye having a strong absorption band in the near-infrared region, which has not been seen in leuco dyes used in conventional heat-sensitive and pressure-sensitive recording materials, and a recording material using the same. With the goal.

〔composition〕

According to the present invention, as the first invention, the formula (1) represents a kyl group, and R9 represents a hydrogen atom or a lower alkyl group. ) A second invention provides a recording material characterized in that the leuco dye represented by the general formula (1) is used as an electron-donating coloring agent.

The leuco dye represented by the general formula (I) of the present invention is a new substance, is a colorless or slightly colored solid that is stable in the atmosphere, and is a colorless or slightly colored solid that is dyed with an inorganic acid such as activated clay or acid clay. When it comes into contact with electron-accepting compounds such as organic acids, phenolic compounds and their derivatives, and oxidizing agents at the molecular level, 1
The coloring reaction occurs quickly to form a deep blue dye, and this colored dye has excellent storage stability, making it useful as a dye precursor. The light absorption spectrum λmax of this dye is about 800 to 820 nm in solution,
The coloring area on the recording paper is about 500 to 900 nm.

The leuco dye represented by the general formula (I) of the present invention is produced by the following method.

(In the formula, R1, R2, R3, R4, R5, R6, R7 and RIl represent a lower alkyl group, and AO represents an anion. The anion is derived from an inorganic acid or an organic acid,
Examples include l-1CQ O4-, carboxylic acid anion, and the like. ) and a tetra(dialkylaminophenyl)cyanine compound represented by the general formula (m) (wherein R9 is a hydrogen atom or a lower alkyl group, and X is Na
, K or Li, respectively. ) A small amount of acetic acid is added to the substituted benzenesulfinate salt represented by the following formula and the catalyst, and the mixture is boiled and refluxed for several hours in an organic solvent. After boiling and refluxing, it is cooled and the precipitated crystals are collected by filtration.

Next, the crystals are washed several times with water and then with an organic solvent such as acetone or methyl ethyl ketone to obtain a highly purified leuco dye represented by the general formula (1).

Specific examples of the compound represented by the general formula (1) of the present invention include 1.1,5.5-tetra-(p-dimethylaminophenyl)-3-p-toluenesulfinyl-1,4-pentadiene. , 1.1,5,5-tetra-(p-dimethylaminophenyl)-3-benzenesulfinyl-1,4-pentadiene, 1.1,5,5-tetra(p-dimethylaminophenyl)-3 -p-toluenesulfinyl-
1,4-pentadiene, 1,1,5,5-tetra-(p
-diethylaminophenyl)-3-benzenesulfinyl-1,4-pentadiene, 1-di(p-dimethylaminophenyl)-5,5-di(p-diethylaminophenyl)-3-p-toluenesulfinyl-1, 4
-pentagene, etc.

The leuco dye of the present invention, like conventional leuco dyes, can be used as a coloring agent in recording materials such as pressure-sensitive recording materials, heat-sensitive recording materials, and thermal transfer type recording materials.

To obtain a pressure-sensitive recording material using the leuco dye of the present invention,
First, microcapsules of leuco dye-dissolved oil are prepared. In this case, the microcapsules can be prepared, for example, by the method described in U.S. Pat. No. 2,800,457, in which one to
This can be done by incorporating diisopropylnaphthalene or terphenyl oil in which 4% leuco dye is dissolved. The particle size of microcapsules is usually around 5 μm. These microcapsules are supported on a support such as paper or plastic film using a binder,
Obtain a color former sheet. Layering this color former sheet with a color former sheet having an electron-accepting compound layer as a color former,
A colored image can be obtained on the coloring agent sheet by applying pressure with a pen or the like to destroy the capsules and bringing the leuco dye into contact with the coloring agent.

To obtain a heat-sensitive recording material using the leuco dye of the present invention, a leuco dye, a coloring agent (electron-accepting compound), a filler such as calcium carbonate, a thermofusible substance such as stearamide, etc. are used. Disperse each of the auxiliary components in an aqueous medium, apply the mixture together with a binder onto a support,
dry. In this case, the particle size of the leuco dye is preferably about 0.1 to 5 μm in volume average particle size. The smaller the particle size, the more contact it has with the coloring agent, resulting in improved sensitivity, but extremely fine particles can cause background fog.

Therefore, in order to prevent background fogging and a decrease in thermal sensitivity, it is particularly preferable that the volume average particle diameter is about 2 to 4 μm. This heat-sensitive recording material is produced by heating it with a thermal head or the like to bring the leuco dye and coloring agent into melt contact.
A colored image can be obtained.

Further, in order to obtain a thermal transfer type recording material using the leuco dye of the present invention, a thermal transfer sheet is prepared by supporting the leuco dye on a support, and a receiving sheet is prepared by supporting a coloring agent on the support. . When a transfer sheet and a receiving sheet are placed one on top of the other and heated from the surface of the transfer sheet, a colored image is obtained on the receiving sheet.

The leuco dye of the present invention can be used in various fields similar to conventional ones, but in particular, it can be used in optical character reading devices and label barcoders by taking advantage of its excellent near-infrared light absorption properties. , it can be used as a coloring agent in recording materials for reading records with barcode readers.

In addition, when the leuco dye of the present invention is used in a heat-sensitive recording label sheet, a heat-sensitive coloring layer containing the leuco dye of the present invention and a coloring agent is provided on one side of the support, and is adhered to the other side of the support. It is sufficient to have a structure in which a release mount is provided through an agent layer, and in this case, a protective layer such as a water-soluble resin layer is provided on the surface of the heat-sensitive coloring layer, if necessary, in order to improve image stability. You can also do that.

〔effect〕

The recording material using the novel leuco dye represented by the general formula (I) according to the present invention has a color-forming part that absorbs light in the near-infrared region, and the color is developed by an image reading device using a general-purpose semiconductor laser. It has the advantage that it can be read. Furthermore, the recording material has a low temperature at which coloring starts, a high coloring density, and the colored portion has excellent light resistance and moisture resistance. Furthermore, the leuco dye of the present invention is applied to various recording fields. Moreover, the leuco dye of the present invention can be produced relatively easily and at low cost.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. Note that all percentages and parts shown below are based on weight.

Reference Example 1 Synthesis of .alpha.,.alpha.-bis-(p-dimethylaminophenyl)ethylene In a 1Q four-piece flask in a nitrogen atmosphere, 4.2 g of magnesium and 50 mQ of diethyl ether (anhydrous) were placed and stirred. A mixed solution of 25 g of methyl iodide and 50 mQ of diethyl ether (anhydrous) was slowly added dropwise to this at room temperature over 90 minutes. M lower ridge was boiled and refluxed for 1 hour to prepare Grignard reagent. A four-piece flask containing the Grignard reagent was kept at 15-11-20°C using ice water, and 500 mfl of a benzene solution containing 23.2 g of Michler's ketone was slowly added over 90 minutes.

After the dropwise addition, the mixture was boiled and refluxed for 1 hour, and further left overnight. This reaction mixture was mixed with 40.6 g of glacial acetic acid and 11 g of ammonium chloride.
．． It was slowly added to a cold aqueous solution containing 3 g and stirred at room temperature for 2 hours. After standing for a while, the mixture was separated into a benzene layer containing the reactant and an aqueous layer. After separating the benzene layer, a reactant was further extracted from the aqueous layer with benzene and mixed with the benzene layer. To this benzene solution, 30 g of calcium chloride (CaCΩ2) was added as a dehydrating agent and left to stand overnight for dehydration. Next, calcium chloride, a dehydrating agent, was removed by filtration, and benzene was further distilled off using a rotary evaporator. The residue was 13.6 g of pale yellow-green solid (number ratio 59.
0%) with a melting point of 118.3-120.2°C. This residue was recrystallized with 200 mρ of ethyl alcohol,
9.48 g (yield: 41.%) of yellow-green powder was obtained. The melting point of this compound was 122.5-124°C.

Reference Example 2 Synthesis of 1.1,5.5-tetra-(p-dimethylaminophenyl)-2,4-pentadien-1-olverchlorate Prepared in a 300 m Q double-sided flask according to the method of Reference Example 1. 26.64 g of α,α-bis-(4-dimethylaminophenyl)ethylene and 20 g of triethyl orthoformate
mQ and 200 mQ of acetic anhydride were added and mixed and stirred.

Next, 7.18 g of 70% perchloric acid was slowly added dropwise, and after the dropwise addition, the mixture was boiled and refluxed for 1 hour and 30 minutes. Crystals with metallic luster precipitated during boiling and refluxing, and further crystals precipitated when cooled. The resulting crystals were collected by filtration and washed several times with water. 29.34 g (91% yield) of crystals were obtained. The melting point of this product was 237.5-238°C.

Example 1 Synthesis of 1.1,5.5-tetra-(p-dimethylaminophenyl)-3-ph luenesulfinyl-1,4-pentadiene 1, prepared according to the method of Reference Example 2, 6.4 g of 1,5.5-tetra-(P-dimethylaminophenyl)-2,4-pentadien-1-olverchlorate, 7.1 g of sodium p-toluenesulfinate, and 6 g of glacial acetic acid.
was dissolved in 200 mQ of acetone and boiled under reflux for 2 hours.

After boiling and refluxing, cool and collect the precipitated crystals by filtration.
The crystals were washed several times with water. Next, washing with acetone yielded 5.6 g of almost white crystals (melting point 1'89-1
90℃).

[Visible absorption spectrum]

λmax (acetic acid) 808nm, E: 1.0X10'
[Infrared absorption spectrum] (KBrBr method) 3040cm-”v C8, 2890cm-198C
83,1610cm-'v C=C11520cm-1
Benzene nucleus, 1145 cm-1v S=0 Example 2 Synthesis of 1.1,5.5-tetra-(P-dimethylaminophenyl)-3-benzenesulfinyl-1,4-pentadiene 1.1,5.5- 5 g of tetra-(p-dimethylaminophenyl)-2,4-pentadien-1-olverchlorate, 7.8 g of sodium benzenesulfinate and 4.7 g of glacial acetic acid were dissolved in 150 m Q of acetone,
Boil and reflux for 2 hours. After boiling and refluxing, the mixture was cooled and the precipitated crystals were collected by filtration, and the crystals were washed several times with water. Next, 4.6 g of pale yellow-green crystals were obtained by washing with a small amount of acetone 6 (melting point 167-168°C) [Visible absorption spectrum] λmax (acetic acid) 808 nm, E: 1.0X10'
[Infrared absorption spectrum] (KBr tablet method) 3040cm-'v C812890cm-'v
5CH3, 1610cm-1v C-C, 1520cm
-'benzene nucleus, 1145 cm-1v S=0 Example 3 Synthesis of 1.1,5.5-tetra-(p-diethylaminophenyl)-3-p-toluenesulfinyl-1,4-pentadiene 1.1,5 .5-tetra-(p-diethylaminophenyl)-2,4-pentadiene-1-olperchloride 1-7.6 g and sodium p-toluenesulfinate 8
．． 9 g and 6.0 g of glacial acetic acid are dissolved in 200 mQ of acetone and boiled under reflux for 2 hours. After boiling and refluxing, the mixture was cooled and precipitated crystals were collected by filtration, and the crystals were washed several times with water.

Then, by washing with a small amount of acetone, 7.2 g of pale blue crystals were obtained (melting point: 110-112°C).

[Visible absorption spectrum]

λmax (acetic acid) 815 nm, f: 1. IXIQ" [Infrared absorption spectrum] (KBr tablet method) 3040cm-" v C812970cm-' v
asCH3,2930cm-' vasct(□, 16
05cm-1 C=C11520cm-1 benzene nucleus,
1145cm-1vS-0 Example 4 Production of thermal recording paper Each mixture having the following composition was dispersed in a ball mill to prepare liquids [A] to [D].

[Liquid A]

Leuco dye of Example 1 10 parts Hydroxyethyl cellulose 10% aqueous solution IQn water
551
1. The dispersed particles of leuco dye have a volume average particle diameter of 2.
It was 42 μm.

[Liquid B]

Stearic acid amide 20 parts Methyl cellulose 5% aqueous solution 20 parts Powder
2/7 Wednesday
601/[Liquid C] Calcium carbonate 30 parts Methyl cellulose 5% aqueous solution 30F1 dispersant
2n water
60I! [Liquid D] Bisphenol A 40 parts Polyvinyl alcohol 10% aqueous solution 20/1 water
140# [Liquid A], [Liquid B], [Liquid C] obtained as above,
[Liquid D] was mixed in a ratio of 1:1:1:3 to create a coating liquid, and this coating liquid was coated on high-quality paper with a basis weight of 50 g/m so that the dry adhesion amount of dye alone was 0.45 g/m. A thermosensitive recording paper was obtained by coating and drying.

The thermal recording paper thus obtained was tested using a thermal gradient tester.
Color was developed at 130° C. for 1 second (applied pressure 2.0 kg/a ( ).The color density at this time was measured using a Macbeth densitometer black filter (filter number: Kodak Wratten N).
o25), it was 1.36, and the skin density was 0.12. Further, the color tone is deep blue, and the absorption region of the coloring part is about 500 to 900 nm, and has a very strong absorption. Its reflection spectrum is shown in the drawing (curve I).

The results of the storage stability test of the obtained thermal recording paper are shown in the following table.

Table Image area survival rate after storage 1) Store at 2760°C in a dry state for 16 hours.

3) Store at 40°C and 90% humidity for 16 hours.

’) Stored under 5000 Lux light for 16 hours.

From the table, it can be seen that the coloring density of the recording paper of the present invention decreases less after storage than before storage, and the coloring area has excellent heat resistance, moisture resistance, and light resistance.

Comparative Example A thermosensitive recording paper was obtained and colored in the same manner as in Example 4, except that PSD-150 (trade name, manufactured by Shin Nisso Kako Co., Ltd.) was used as the leuco dye. The reflection spectrum of the colored part is shown in the drawing (curve 2).

As is clear from the drawing, this coloring part has a light wavelength of about 700
It exhibits almost no light absorption for wavelengths larger than nm.

Example 5 Production of pressure-sensitive copying paper 10 parts of gelatin and 10 parts of gum arabic were mixed with 4 parts of water at 40°C.
0.00 parts of the mixture, 0.2 parts of funnel oil as an emulsifier is added thereto, and 40 parts of diisopropylnaphthalene oil in which 2% of the leuco dye of Example 2 is 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, 10% acetic acid is added to adjust the pH of the solution to 4.0 to 4.2 to cause coacervation. Stirring is continued, and after 20 minutes, the mixture is cooled to gel the coacervate film deposited on R4 of 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 a 15% aqueous solution of caustic soda to bring P)I to 9. At this time, add the caustic soda slowly and carefully. Subsequently, the mixture was stirred and heated for 20 minutes to 50° C., thereby creating microcapsules of leuco dye-dissolved oil. The obtained microcapsules were coated on the lower surface of the support at a rate of 6 g/rrr using water-soluble starch as a binder, and dried to obtain a top paper.

When this upper paper and a commercially available pressure-sensitive coloring sheet were placed one on top of the other and pressure was applied using a pen or the like, a clear copy image of deep blue color was obtained on the coloring sheet.

[Brief explanation of drawings]

The drawings show the reflectance for each light wavelength of a colored image of a thermal recording paper obtained using the electron-donating coloring agent of the present invention and a thermal recording paper obtained using a commercially available electron-donating coloring agent. Curve 1 (solid line): Colored image reflection spectrum of the thermal recording paper obtained in Example 3 Curve 2 (dotted line): Colored image reflection spectrum of the thermal recording paper obtained in Comparative Example Patent applicant Ricoh Co., Ltd. Continuing Amendment Book July 1, 1988 1, Indication of the case 1989 Patent Application No. 89269 2, Name of the invention Novel leuco dye and recording material using the same 3, Person making the amendment Related Patent Applicant Address 1-3-6 Nakamagome, Ota-ku, Tokyo Name
(674) Rico Co., Ltd. - Representative Hama 1) Hiro 4, Agent 〒151 5, Date of amendment order Voluntary 6, Number of inventions increased by amendment 07, ``Detailed description of the invention'' in the specification subject to amendment Column 8, Contents of amendment The following amendments will be made to the specification of the application. (1) The structural formula of general formula (II) on page 7, lines 1 and 2 is corrected as follows. “General formula (n)” (2) Page 15, line 7 “λmax (acetic acid) 808 nm
, t :1.0X10'J as "λff1ax (
acetic acid) 809 nm: ε1. I x 10'640nm
: Corrected to t 3.9X10'J. (3) “λmax (acetic acid) 808 nm on page 16, line 5
, ε: 1.0X10'J, "λmax (acetic acid) 810
nm: E 1.15X105640nm:ε3.8X
Corrected to 10'J. (4) Page 17, line 3, “λmax (acetic acid) 815 nm
, ε:1. lX10J, "λmax (acetic acid) 811n
m: ε8.35 x 10'668nm14. lX10
'Correct to J.

Claims (2)

[Claims] (1) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, R_1, R_2, R_3, R_4, R_5, R
_6, R_7 and R_8 each represent a lower alkyl group, and R_9 represents a hydrogen atom or a lower alkyl group, respectively. ) A novel leuco dye represented by (2) General formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, R_1, R_2, R_3, R_4, R_5, R
_6, R_7 and R_8 each represent a lower alkyl group, and R_9 represents a hydrogen atom or a lower alkyl group, respectively. ) A recording material characterized by using a leuco dye represented by the following as an electron-donating coloring agent.